Alternator charging a Lithium bank


Dominique Sery
 

Hello,
Victron recommends that you put T fuses on each battery line in series as you have done. I planned to put in 400 A as you did. Security essential it seems to me.
I bought 6x12,8v batteries and i planned to put 3x400A fuses like you.
Dominique


Scott SV Tengah
 

Doug,

I don't know enough about it to opine as to whether it's a good idea but if it doesn't have any negative effects, better safe than sorry. Let us know what you decide to do.

I have a 450amp "Mega" fuse on each serial pair of Victron Lithiums. I have had them blow when a technician was working on the bow thruster and during this one test forget to shutoff the main switches. The fuses probably saved us from quite a bit more damage. I have heard that Amel did not add fuses because they were concerned that with the original spec lead batteries, high loads would cause such a significant voltage drop that the amperage would spike and potentially blow the fuse. I am certainly glad I have them!

As a side note, the blown fuses showed perfect continuity but would not pass any current! Made me scratch my head for a few hours.

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com


Doug Smith
 

Great feedback Scott, Dominique and Dean. I feel like I am in a “masterclass”.

I was thinking of the Sterling APD, in the same way you use fuses for the batteries.  It is unlikely that the 450 fuses would blow, but having the APD installed gives protection to the alternator, if there is a disconnect of the batteries for any reason.  Not just cutoff of the BMS, but a disconnect for other reasons like a blown fuse on the Cerbo, or BMS, or even the main battery fuses while the engine is running.  Maybe overkill, and that is why I am putting this out there. Trying to learn from those who are already doing the installation and living with it, while I am buying pieces. 

 

Doug Smith

S/V Aventura, Amel 54-113

Patuxent River, MD USA

 

From: <main@AmelYachtOwners.groups.io> on behalf of Scott SV Tengah <Scott.nguyen@...>
Reply-To: <main@AmelYachtOwners.groups.io>
Date: Thursday, February 18, 2021 at 3:29 AM
To: <main@AmelYachtOwners.groups.io>
Subject: Re: [AmelYachtOwners] Alternator charging a Lithium bank

 

[Edited Message Follows]
[Reason: correction: cerbo vs. cyrix confusion on my part]

Doug/all,

That Cerbo GX is pretty powerful! I just skimmed the manual and it certainly provides a lot of cool features. If I was building a system from scratch, I would possibly consider adding it, although the parasitic draw of it and the DMC (which you are required to have if you have the Ve-bus BMS and want to also be able to turn off your inverter - see manual) starts to add up. I went down this road to minimize generator usage, so I am willing to give up some cool features to achieve my primary goal. 

That said, I agree with Dean on minimizing the number of devices/connections that need to work perfectly to keep my expensive Victron batteries alive. One single connection/device failure, ONE TIME, could kill a battery. Not great when you're in the middle of the Pacific. My caveman relay system was "designed" so that if they fail open, the worst case is that the alternator stops charging prematurely. If they fail closed, the MV Alpha Pro II will still stop charging at 27.4v or thereabouts. A low enough absorption voltage that you're well out of the knees of the voltage curve, so per Victron techs, the likelihood of a cell over voltage that is masked by the bank voltage is very very low. If you go the Cerbo route, I suggest you do the same with respect to MV absorption voltages. 

Maybe I am missing something important, but why is the Sterling APD necessary on a mostly Victron system? The over volt/overtemp is dealt with by turning off the MPPT,Quattro,Skylla,MV Alternator and ceasing charging - you will not have a hard disconnect event with the alternator pumping out full output. On a low cell voltage event, the Victron solution is to cut off the loads. The batteries are still connected to the charging side if I recall correctly so the alternator will not experience a hard disconnect. In any event, low voltage disconnect is a missing piece on my system, as I mentioned in previous posts. My installation of the Victron BP-220 was unsuccessful and I intend to wire my system so that the Onan starts if SOC gets below say 30% or possibly if cell voltage is below 3v. To be continued.

Dominique - you can adjust the charging voltages on the MV if that helps. Start with the Lithium profile and adjust as you feel appropriate. That said, I personally think the LiCT and the Li Charge are adding unnecessary complexity. For reasons mentioned above, if I can achieve the same functional result, I would rather go simpler vs. more complex.

Dean - I think that without the BMV-712,  the Cerbo wouldn't know how many AH the MV alternator is putting into the batteries? Maybe it gets that value from its own shunt?


--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com


Dean Gillies
 
Edited

On Thu, Feb 18, 2021 at 07:17 PM, Scott SV Tengah wrote:

Dean - I think that without the BMV-712,  the Cerbo wouldn't know how many AH the MV alternator is putting into the batteries? Maybe it gets that value from its own shunt?

Scott, 
My REC BMS has its own shunt, which allows it to monitor Ah in/out (Coulomb count), this information is provided from my BMS to the Cerbo by CAN Bus and is used by the DVCC assistant as well as being displayed on the Touch. In my case the 712 is therefore redundant.
If the Victron batteries/BMS offer this same functionality, then I wondered if the 712 is not needed.  It may be that the Victron battery/BMS subsystem does not provide this function?

Cheers, Dean
SV Stella
A54-154


Dean Gillies
 

Hi Dominique,
Scott does have a good solution.

Regarding the Cyrix disconnect, I'm not convinced you will see that problem in real use. It is very unusual for a lead acid battery (gel, agm or flooded) to rest for long at 13.2V+ volts. As soon as you apply any load at all to the battery, the voltage will drop to 12.7-12.8V.  I suspect that simply connecting your battery to the Cyrix will cause the voltage to drop quickly to less than 13.2V (per battery) and therefore the Cyrix unit will disconnect. 

Maybe you can test this?

Personally I like the idea of retaining some Lead Acid capacity for a few reasons, but mainly as a fail safe. The system I am working on at the moment has lead acid and Lithium connected directly together. Ie no Cyrix unit in the system. As you correctly noted this does cause the Li battery to top-off the Pb at the end of a charge cycle, and the Pb does almost nothing on a discharge cycle until the Li reaches around 5% SOC.  If you think about these two characteristics for a bit, you will realise that they are very good things. Li batteries don't like to remain at high SOC for too long (they won't), and the Pb batteries provide an extra buffer at low SOC to support the Lithium batteries as they near low Voltage disconnect.

When operating the system in real life, I would try to maintain the Li system above 20% SOC, this means that the Pb batteries are almost always close to full charge.

If/when the Li batteries disconnect (for any of the reasons that can happen) the Pb batteries continue to power the boat systems with no outage.

The alternator disconnect issue is solved of course, because the Pb is always in the system.

When leaving the boat or simply being alongside for long periods, the Li system can be dropped to 50% SOC and simply turned off, leaving the Pb system to operate in the usual float mode. 

Finally, as with your system, weight of the Pb batteries helps with the port side list of the 54. 

Best regards, Dean

SV Stella
A54-154

 

 

 


Scott SV Tengah
 
Edited

Doug/all,

That Cerbo GX is pretty powerful! I just skimmed the manual and it certainly provides a lot of cool features. If I was building a system from scratch, I would possibly consider adding it, although the parasitic draw of it and the DMC (which you are required to have if you have the Ve-bus BMS and want to also be able to turn off your inverter - see manual) starts to add up. I went down this road to minimize generator usage, so I am willing to give up some cool features to achieve my primary goal. 

That said, I agree with Dean on minimizing the number of devices/connections that need to work perfectly to keep my expensive Victron batteries alive. One single connection/device failure, ONE TIME, could kill a battery. Not great when you're in the middle of the Pacific. My caveman relay system was "designed" so that if they fail open, the worst case is that the alternator stops charging prematurely. If they fail closed, the MV Alpha Pro II will still stop charging at 27.4v or thereabouts. A low enough absorption voltage that you're well out of the knees of the voltage curve, so per Victron techs, the likelihood of a cell over voltage that is masked by the bank voltage is very very low. If you go the Cerbo route, I suggest you do the same with respect to MV absorption voltages. 

Maybe I am missing something important, but why is the Sterling APD necessary on a mostly Victron system? The over volt/overtemp is dealt with by turning off the MPPT,Quattro,Skylla,MV Alternator and ceasing charging - you will not have a hard disconnect event with the alternator pumping out full output. On a low cell voltage event, the Victron solution is to cut off the loads. The batteries are still connected to the charging side if I recall correctly so the alternator will not experience a hard disconnect. In any event, low voltage disconnect is a missing piece on my system, as I mentioned in previous posts. My installation of the Victron BP-220 was unsuccessful and I intend to wire my system so that the Onan starts if SOC gets below say 30% or possibly if cell voltage is below 3v. To be continued.

Dominique - you can adjust the charging voltages on the MV if that helps. Start with the Lithium profile and adjust as you feel appropriate. That said, I personally think the LiCT and the Li Charge are adding unnecessary complexity. For reasons mentioned above, if I can achieve the same functional result, I would rather go simpler vs. more complex.

Dean - I think that without the BMV-712,  the Cerbo wouldn't know how many AH the MV alternator is putting into the batteries? Maybe it gets that value from its own shunt?


--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com


Dominique Sery
 

Hello Dean,
 
Before having read the attractive solution proposed by Scott, I considered, as proposed by Victron, to keep two lead batteries (in series to have 24v) connected in parallel to the lithium batteries with either a Cyrix Li CT or a Cyrix Li Charge associated with an Argofet diode distributor.
What annoys me:
The Mastervolt alternator (with lithium profile chosen with the Master Adjust software via the Masterbus-USB interface) has a bulk phase at 14.25 v, an absorption time at 0 and a maintenance phase at 13.25 v.
With the Li CT the coupling is done at 13.4v and the separation at 13.2v. The Victron batteries that I received (not yet installed, for the moment in my garage) have a voltage of 13.28v whereas they would be charged only at 50/60% according to Victron. Charged, the voltage will be a bit higher so I'm afraid that the Li CT will remain open when the engine is stopped (the alternator doesn't turn anymore) and that the Li batteries will discharge into the Pb batteries until they are below 13.2v and the relay opens.
For the Cyrix Li charge the connection is made at 13.7v and the disconnection at 13.4v.
So the generator will be switched off at the end of the bulk phase and will not use the 13.25v maintenance phase provided by Mastervolt, the Argofet diode generator will consume power even when stopped unless additional relays are installed.
The solution proposed by Scott with an SSR seems more interesting to me.


Dominique Sery
 

Thank you Scott,
You have found a good solution,
thank you for sharing it.
Dominique
 


Dean Gillies
 

Hi Doug,
The Cerbo, operating with DVCC, will certainly provide relay control for the alternator cut-off.

I believe (but have no practical experience) that the Victron BMS will interface to the Cerbo to provide the necessary signals. That is a valid solution.

However, I think that a better solution is to control the alternator cut-off directly from the BMS. This eliminates one level of abstraction and a potential point of hardware/comms failure.

The Cerbo is still a very useful device in a Victron system for all sorts of reasons that you already know!

I wonder if you actually need the BMV-712 in your system? Does the Victron Battery/BMS subsystem provide all of the same information via the Cerbo/Touch display? If so, what is the purpose of the 712? Maybe it is not required, in which case you may consider leaving the Xantrex display in-place and relocate its Shunt to monitor the 12V starting battery.   

Best regards,
Dean
SV Stella
A54-154

 


Doug Smith
 

Thanks Scott, Dominique and Dean.

I appreciate the real world experience. I will look more into the VE.Direct circuits and logic within the Cerbo, Victron.BMS and Cryix-Li-ct, to see if those offer the options to disconnect the Alternator regulator, when high SOC/voltage is met.  The individual cell level monitoring is certainly the reason to use the Victron BMS with Victron Batteries. I still am thinking that one of these (Cerbo or the BMS, or possibly the BVM, if it receives a command from the others) could be used to disconnect the power to the regulator, thereby turning off the charging from the alternator. I am suggesting using the existing relays that are tied to the ignition circuit, to depower the regulator. In the Cerbo manual there is a section on DVCC, (Distributed Voltage and Current Control).  Section 8 and it sounds like this then makes the Cerbo an active control device for the over voltage scenario, using information obtained from the BMS and chargers. This is my reason for bringing this conversation back to the front. If the ignition relays are the right ones, than the Cryix relay would do the trick. And it is controlled through the Victron Direct messaging from the BMS or the Cerbo.

Scott, a few of the steps you created switches for, and steps used to turn off the chargers prior to starting the generator, then ramping up the charging are largely addressed by using the Cerbo, and the Digital Multi Control panel. That was my motivation for the added devices.  Your switches won’t fail for 100 years, but my mind would likely need a checklist to ensure I didn’t skip steps or forget steps.  And the ability to monitor and manage from off the boat is a nice benefit as well.

I believe the risks to the alternator from a sudden disconnect of the BMS and batteries at low voltage has already been discussed and I am comfortable that the Sterling APD will give protection from the spike that would occur, if there were a sudden, unanticipated battery disconnect while a large alternator current was being delivered.

I have a current Mastervolt inverter, 2500 watt, that is 12 years old, and may last longer, but will be replacing with the quattro next year or so.  The other Mastervolt devices are inverters, and are not involved in the charging circuits, so I won’t be managing those through the Victron world.  They are just providing stable voltages for the electronics and low draw devices.

Thanks for the great discussion and assistance.

 

Doug Smith

S/V Aventura, Amel 54-113

Patuxent River, MD USA

 

From: <main@AmelYachtOwners.groups.io> on behalf of Scott SV Tengah <Scott.nguyen@...>
Reply-To: <main@AmelYachtOwners.groups.io>
Date: Wednesday, February 17, 2021 at 5:13 AM
To: <main@AmelYachtOwners.groups.io>
Subject: Re: [AmelYachtOwners] Alternator charging a Lithium bank

 

Hi Doug,

Seems you read what I wrote but it didn't provide the answers you needed? Probably the result of someone who studied economics trying to explain something way out of his pay grade. :)

I'll try to answer your questions, though.

- As Dean alluded to, you do not want to base your alternator charging cutoff on battery bank level voltages. Your Victron chargers, interfaced to your Victron BMS will do that automatically. The Quattro does it through ethernet but my Skylla-i 24/80 needed an interface wire, which of course Victron sells. I have seen my Victron BMS, which monitors cell level voltage, cut off charging while the bank voltages and my BMV-712 (which I think is a coulomb counter?) showed it was not even 90% SOC and the bank level voltage seemed fine at around 28.0v. The voltage spike on the one problematic cell was hidden by the other (4x6-1=23) cells that were not spiking.  As an aside, this imbalance occurred because I didn't charge to 100% for a few months and small cell imbalances started accumulating. That was resolved with few hours at 100% with solar and a temporarily extended (4 hr) absorption time, which allowed the batteries to self-balance at a cell level.

I cannot remember exactly where I set the alternator absorption voltage to, but I recall it being somewhere around 27.4v on the Alpha Pro II. This makes it such that my lithium batteries are never fully charged by the alternator, but I'm ok with that, especially when I find myself unhappily motoring for 24 hours in the doldrums! The 27.4v usually represents anywhere from 80-92% bank SOC - again a reminder that you can't rely on voltage to represent SOC on lithium.

I assume you wanted to install the Cyrix relay to abruptly disconnect the alternator from the battery bank if the BMS detects a cell overvolt/overtemp condition? I would not suggest that as it could damage the alternator. Maybe not, but why take the risk when you can simply use the Ve.BUS BMS "charge disconnect" wire to control the relays as I suggested in this post:
https://amelyachtowners.groups.io/g/main/message/50689

As Dominique stated, the Victron BMS cannot power a normal Hella relay. I tried many times and had senior techs at Victron helping me, but it simply didn't have enough power to do so.  That's why I had to put in a much lower draw solid state relay in combination with Hella relays. See the post I linked for details. It has worked perfectly for 10,000nm over a year of full time cruising since I installed that alternator cutoff system. A real engineer, who built a well known company hacking into car ECU and control systems helped me implement it, so that should give you more confidence that it works. :) The low absorption voltage is an additional protection in case one of those relays fail.

- How do you intend to have your Victron BMS control your Mastervolt battery chargers? I don't have MV chargers, so can't provide advice, but you need to make sure the MV chargers stop charging when the BMS detects a problem. 

- Clarification: the 24v alternator is a Mastervolt too, not a Volvo charger. The Volvo charger (Bosch, really) is the 12v charger and doesn't have anything to do with my lifepo4 system. Get the alt temp sensor and install it on the MV. I have never seen my alternator taper charging current due to alternator overtemp, even when it charged the bank from 30%-90% SOC. That's roughly 3.5 hours at full output on my system. But you can never be too safe if you're in the middle of the Pacific without a MV dealer nearby.

- I did not install the Cerbo, Touch GX or the DMC. I found that I could replicate most of their functions without the additional complication and parasitic power draw of those devices. It's cool stuff for sure, but there is a draw and it's simply more components to fail. 

- Make sure you can turn off your Quattro inverter easily. I think Victron says it draws 30w at idle, but I am seeing more like 45-50w. That's almost 50amps a day of parasitic loss if you kept your inverter on 24/7, equivalent to the power output of a 250w solar panel, more or less! We have a simple switch (see post linked above) that we turn on right when we use it and off when we're done. 

- I use the BMV-712 right now to keep the batteries from being kept at a high SOC by the solar, per the solution I detailed on my previous post. We are sadly away from Tengah for 3 months due to visa issues but the boat watcher tells me the batteries cycle between 65%-85% range as I intended. The bonus is that the dehumidifier I am using to burn off excess solar energy is keeping the boat dry inside. For this possible use and also the reasons mentioned above, I wouldn't use this BMV-712 programmable relay to control your alternator.

Hope this helps clarify things a bit. 

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com


Scott SV Tengah
 

Dominique:

See https://amelyachtowners.groups.io/g/main/message/50689

I banged my head against the engine room firewall for over a year until I had a very smart non-marine engineer help me implement that solution. I've run it for over a year now and it works perfectly.

That will solve your problem. 

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com


Scott SV Tengah
 

Hi Doug,

Seems you read what I wrote but it didn't provide the answers you needed? Probably the result of someone who studied economics trying to explain something way out of his pay grade. :)

I'll try to answer your questions, though.

- As Dean alluded to, you do not want to base your alternator charging cutoff on battery bank level voltages. Your Victron chargers, interfaced to your Victron BMS will do that automatically. The Quattro does it through ethernet but my Skylla-i 24/80 needed an interface wire, which of course Victron sells. I have seen my Victron BMS, which monitors cell level voltage, cut off charging while the bank voltages and my BMV-712 (which I think is a coulomb counter?) showed it was not even 90% SOC and the bank level voltage seemed fine at around 28.0v. The voltage spike on the one problematic cell was hidden by the other (4x6-1=23) cells that were not spiking.  As an aside, this imbalance occurred because I didn't charge to 100% for a few months and small cell imbalances started accumulating. That was resolved with few hours at 100% with solar and a temporarily extended (4 hr) absorption time, which allowed the batteries to self-balance at a cell level.

I cannot remember exactly where I set the alternator absorption voltage to, but I recall it being somewhere around 27.4v on the Alpha Pro II. This makes it such that my lithium batteries are never fully charged by the alternator, but I'm ok with that, especially when I find myself unhappily motoring for 24 hours in the doldrums! The 27.4v usually represents anywhere from 80-92% bank SOC - again a reminder that you can't rely on voltage to represent SOC on lithium.

I assume you wanted to install the Cyrix relay to abruptly disconnect the alternator from the battery bank if the BMS detects a cell overvolt/overtemp condition? I would not suggest that as it could damage the alternator. Maybe not, but why take the risk when you can simply use the Ve.BUS BMS "charge disconnect" wire to control the relays as I suggested in this post:
https://amelyachtowners.groups.io/g/main/message/50689

As Dominique stated, the Victron BMS cannot power a normal Hella relay. I tried many times and had senior techs at Victron helping me, but it simply didn't have enough power to do so.  That's why I had to put in a much lower draw solid state relay in combination with Hella relays. See the post I linked for details. It has worked perfectly for 10,000nm over a year of full time cruising since I installed that alternator cutoff system. A real engineer, who built a well known company hacking into car ECU and control systems helped me implement it, so that should give you more confidence that it works. :) The low absorption voltage is an additional protection in case one of those relays fail.

- How do you intend to have your Victron BMS control your Mastervolt battery chargers? I don't have MV chargers, so can't provide advice, but you need to make sure the MV chargers stop charging when the BMS detects a problem. 

- Clarification: the 24v alternator is a Mastervolt too, not a Volvo charger. The Volvo charger (Bosch, really) is the 12v charger and doesn't have anything to do with my lifepo4 system. Get the alt temp sensor and install it on the MV. I have never seen my alternator taper charging current due to alternator overtemp, even when it charged the bank from 30%-90% SOC. That's roughly 3.5 hours at full output on my system. But you can never be too safe if you're in the middle of the Pacific without a MV dealer nearby.

- I did not install the Cerbo, Touch GX or the DMC. I found that I could replicate most of their functions without the additional complication and parasitic power draw of those devices. It's cool stuff for sure, but there is a draw and it's simply more components to fail. 

- Make sure you can turn off your Quattro inverter easily. I think Victron says it draws 30w at idle, but I am seeing more like 45-50w. That's almost 50amps a day of parasitic loss if you kept your inverter on 24/7, equivalent to the power output of a 250w solar panel, more or less! We have a simple switch (see post linked above) that we turn on right when we use it and off when we're done. 

- I use the BMV-712 right now to keep the batteries from being kept at a high SOC by the solar, per the solution I detailed on my previous post. We are sadly away from Tengah for 3 months due to visa issues but the boat watcher tells me the batteries cycle between 65%-85% range as I intended. The bonus is that the dehumidifier I am using to burn off excess solar energy is keeping the boat dry inside. For this possible use and also the reasons mentioned above, I wouldn't use this BMV-712 programmable relay to control your alternator.

Hope this helps clarify things a bit. 

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com


Dean Gillies
 

Dominique,
I am considering a hybrid 24V system using lead acid and lithium, but without the Cyrix Li CT.
I wonder if you could elaborate a little on the disadvantages you mention?
many thanks
Dean
SY Stella
A54-154


Dean Gillies
 

Hello Doug,
Good points above from the other members.

I would not recommend the use of any alternator cut-off mechanism that is not based upon direct cell-level monitoring.  You must ensure that the alternator ceases charging before the BMS disconnects due to a cell over-voltage.  This is not guaranteed to happen if you only monitor the battery (24V) voltage to control the alternator.

If you planning on using the Victron Lithium batteries and BMS then I think Scott has a solution. Scott?

Dean
SV Stella
A54-154

 

 


Dominique Sery
 

Hello Doug,
I am in the process of installing lithium batteries on my 54.
I followed the different interventions (especially the very detailed one by Scott) with a lot of interest.
Like you I chose the Victron system.
My only concern is the Mastervolt 24V 110A alternator.
I have an Alpha pro 2 regulator and I bought a Masterbus USB interface that allows me to set the alternator parameters with the Mastervolt software to adapt it to lithium and also an alternator temperature sensor.
The Ve BMS Victron does not allow to disconnect the regulator from the alternator and it does not have enough power to control a relay (10mA only).
I only see the solution of the manual switch.
On my boat the Amel system consists of two relays: a 12 volts relay activated by the ignition key, this relay activates a 24 volts relay that feeds the regulator (brown wire).
The audible alarm of the Ve BMS only goes off in case of deep discharge but not in case of overload.
The BMV 712 can control a relay but it only takes into account the voltage of the boat but not the voltages of each cell as the BMS does.
I did not find a satisfactory solution, except to keep two lead batteries (for 24v) in buffer with a Cyrix Li CT as proposed by Victron but there are also disadvantages.
If anyone has a solution...
Regards
Dominique


Doug Smith
 

Thanks for the detailed answer Dan!

Thanks, Doug Smith

Amel 54-113, Aventura
Petuxent River MD, USA
Dugsmith98@...

On Feb 16, 2021, at 12:27 PM, Dan Carlson <carlsdan61@...> wrote:


Hello Doug, 

When I was lost in the weeds in all the design decisions and particularly with regard to integration, the best advice some one gave me is design your charging systems to manage themselves! Don't rely on communications between systems. That is good advice. I have a Venus GX system and I have had to reboot it every month or two because the basic coms I use to monitor my system needs to be reset. 

When you set up your charging  systems don't try to count amp/hrs. That's nice for monitoring, but control your charging to battery voltage, preferable measured at the battery or the shunt right at the battery. Use the conservative values that your battery maker provides for your charge profiles.  Others may suggest that you can be more aggressive, but your battery capacity should allow you to easily support your daily needs between 40%-80% SOC.

For my batteries that is 26.72v float and I charge to a max of 27.5v when topping/balancing the battery (about once a month). I think that the lowest I've pulled the battery is to about 25.5v. 

If you have not upgraded your Alternator controller yet, then I encourage you to look at the WakeSpeed 500 controller. I think that it still has features that are ahead of the others, and it has a layer of programmability above that. I did not need to do any programming. I used it right out of the box.  But a couple of features I really like are:
1) the WS 500 measures temperature at the alternator negative terminal, 
2) it measures voltage AND current from your BMV shunt,
3) a dip switch on the box de-rates the alternator to 75% output to protect the alternator (and drive belts). 
4) When using the out of the box Lithuum charge profile you can add a switch that switches the controller between normal charge profile or "float". When it is set at the "float" setting it charges to and holds the battery at 26.72v (approximately 75% SOC), but it also monitors the current flow at the shunt to react quickly to large current draws (winches, windlasses, bow thruster). I love that feature and leave it on float as a default. I only switch it the "charge" mode when I need to charge the batteries and then I am paying attention and monitoring the BMS.

This is a different philosophy from set it and forget it, but the common theme of battery failure (lead acid, AGM, or Lithium) is that something happens when no one is watching and the result is a pile of trashed batteries at the next marina while you scramble to get a replacement shipment.

I hope that helps a bit.

Best regards Daniel Carlson on sv BeBe, SM #387


On Tue, Feb 16, 2021, 12:14 PM Doug Smith via groups.io <dugsmith98=yahoo.com@groups.io> wrote:

Hello group and apologies for such a very specific question.  This is regarding the ‘stop charging’ cutoff for the 24V Mastervolt alternator with respect to a Lithium house bank.

I have reviewed everything I can find within our internal group email messages on this subject and have found great value in the education I have received. Also scoured the Victron site, Wil Prouse’s videos, PYS and the Marine How To web site for more information.

 

I have spent the last few weeks mapping out the transition of the equipment I currently have and drawing my schematics for the upgrade to Lithium over the next 12-18 months.

My schematic is attached for planned system. I agree with the idea of one vendor for the system, and have a mostly Victron layout to begin with so will continue that direction. 

Phase 1, installed already or over this winter

Cerbo GX, with Touch GX for display, mounted in battery compartment with the display on the forward bulkhead of the passage berth at eye level.

BMV-712 replacing the Xantrex.

Skylla-I 24|100|1+1 battery charger

Sterling Alternator Protect Device

Currently have a Mastervolt, 24-2500 Mass sine wave inverter, 24/24 inverter, and 24/12 inverters

Phase 2, next winter

We will upgrade to the quattro with the Digital Multi Control panel in the second phase with necessary cabling as required

Solar Arch with Panels, and Smart Solar MPPT controller.

Alpha Pro III, upgrading from the Alpha Pro. Keeping the original Mastervolt 24/110 alternator.

Phase 3, will be to switch to Victron Lithium and BMS when current AGM’s reach end of life cycle and my own full time retirement begins

 

Scott’s email from SV Tengah described a method of cutting off the Volvo Alternator charging circuit using external relays and using the battery disconnect signal from the VE.BMS to control when the cutoff relay would disconnect the Alpha Pro regulator. This disconnect would be set at a level lower than full voltage, and it appears he set it around 26.5 for float.

Arno, Mark, Bill and others have commented on using Coulomb counters for amount of current out-in to measure when the SOC is nearing 90-100%. 

What I am raising as a question is “why not use the BMV – 712 self-contained relay, as the method to cut off the alternator charging when either or both the voltage hits a threshold or the SOC is near capacity?”  There is an internal relay on the back of the BMV-712, with both normally open and normally closed contacts that is bi-directionally stable, with low current draw, and a built in option to activate the relay using a logic circuit of both voltage and SOC based on a low and a high threshold.  Then use the Alpha Pro “activate and disconnect relays” in the box that are activated when the volvo is running by means of the ignition circuit. When SOC is 90%, it would disconnect the alternator ignition circuit using the relays in the regulator box. Also, does anyone have better information about how those relays are connected to the ignition circuit? I have attached what I have found, but not sure if any of this impacts the circuits running the engine or its system electronics. This would appear to simplify the concerns, but I am worried I am missing something.

A second option is a Cryix-Li-ct 12/24-120 relay.  This would be one more Victron component to add, but appears to be a way to disconnect using the Victron Direct port signal coming from either the Cerbo, BMS or the BMV.

I am pretty deep into the weeds on this so any or all feedback is appreciated,

 

Doug Smith

S/V Aventura, Amel 54-113

Patuxent River, MD USA


Dan Carlson
 

Hello Doug, 

When I was lost in the weeds in all the design decisions and particularly with regard to integration, the best advice some one gave me is design your charging systems to manage themselves! Don't rely on communications between systems. That is good advice. I have a Venus GX system and I have had to reboot it every month or two because the basic coms I use to monitor my system needs to be reset. 

When you set up your charging  systems don't try to count amp/hrs. That's nice for monitoring, but control your charging to battery voltage, preferable measured at the battery or the shunt right at the battery. Use the conservative values that your battery maker provides for your charge profiles.  Others may suggest that you can be more aggressive, but your battery capacity should allow you to easily support your daily needs between 40%-80% SOC.

For my batteries that is 26.72v float and I charge to a max of 27.5v when topping/balancing the battery (about once a month). I think that the lowest I've pulled the battery is to about 25.5v. 

If you have not upgraded your Alternator controller yet, then I encourage you to look at the WakeSpeed 500 controller. I think that it still has features that are ahead of the others, and it has a layer of programmability above that. I did not need to do any programming. I used it right out of the box.  But a couple of features I really like are:
1) the WS 500 measures temperature at the alternator negative terminal, 
2) it measures voltage AND current from your BMV shunt,
3) a dip switch on the box de-rates the alternator to 75% output to protect the alternator (and drive belts). 
4) When using the out of the box Lithuum charge profile you can add a switch that switches the controller between normal charge profile or "float". When it is set at the "float" setting it charges to and holds the battery at 26.72v (approximately 75% SOC), but it also monitors the current flow at the shunt to react quickly to large current draws (winches, windlasses, bow thruster). I love that feature and leave it on float as a default. I only switch it the "charge" mode when I need to charge the batteries and then I am paying attention and monitoring the BMS.

This is a different philosophy from set it and forget it, but the common theme of battery failure (lead acid, AGM, or Lithium) is that something happens when no one is watching and the result is a pile of trashed batteries at the next marina while you scramble to get a replacement shipment.

I hope that helps a bit.

Best regards Daniel Carlson on sv BeBe, SM #387


On Tue, Feb 16, 2021, 12:14 PM Doug Smith via groups.io <dugsmith98=yahoo.com@groups.io> wrote:

Hello group and apologies for such a very specific question.  This is regarding the ‘stop charging’ cutoff for the 24V Mastervolt alternator with respect to a Lithium house bank.

I have reviewed everything I can find within our internal group email messages on this subject and have found great value in the education I have received. Also scoured the Victron site, Wil Prouse’s videos, PYS and the Marine How To web site for more information.

 

I have spent the last few weeks mapping out the transition of the equipment I currently have and drawing my schematics for the upgrade to Lithium over the next 12-18 months.

My schematic is attached for planned system. I agree with the idea of one vendor for the system, and have a mostly Victron layout to begin with so will continue that direction. 

Phase 1, installed already or over this winter

Cerbo GX, with Touch GX for display, mounted in battery compartment with the display on the forward bulkhead of the passage berth at eye level.

BMV-712 replacing the Xantrex.

Skylla-I 24|100|1+1 battery charger

Sterling Alternator Protect Device

Currently have a Mastervolt, 24-2500 Mass sine wave inverter, 24/24 inverter, and 24/12 inverters

Phase 2, next winter

We will upgrade to the quattro with the Digital Multi Control panel in the second phase with necessary cabling as required

Solar Arch with Panels, and Smart Solar MPPT controller.

Alpha Pro III, upgrading from the Alpha Pro. Keeping the original Mastervolt 24/110 alternator.

Phase 3, will be to switch to Victron Lithium and BMS when current AGM’s reach end of life cycle and my own full time retirement begins

 

Scott’s email from SV Tengah described a method of cutting off the Volvo Alternator charging circuit using external relays and using the battery disconnect signal from the VE.BMS to control when the cutoff relay would disconnect the Alpha Pro regulator. This disconnect would be set at a level lower than full voltage, and it appears he set it around 26.5 for float.

Arno, Mark, Bill and others have commented on using Coulomb counters for amount of current out-in to measure when the SOC is nearing 90-100%. 

What I am raising as a question is “why not use the BMV – 712 self-contained relay, as the method to cut off the alternator charging when either or both the voltage hits a threshold or the SOC is near capacity?”  There is an internal relay on the back of the BMV-712, with both normally open and normally closed contacts that is bi-directionally stable, with low current draw, and a built in option to activate the relay using a logic circuit of both voltage and SOC based on a low and a high threshold.  Then use the Alpha Pro “activate and disconnect relays” in the box that are activated when the volvo is running by means of the ignition circuit. When SOC is 90%, it would disconnect the alternator ignition circuit using the relays in the regulator box. Also, does anyone have better information about how those relays are connected to the ignition circuit? I have attached what I have found, but not sure if any of this impacts the circuits running the engine or its system electronics. This would appear to simplify the concerns, but I am worried I am missing something.

A second option is a Cryix-Li-ct 12/24-120 relay.  This would be one more Victron component to add, but appears to be a way to disconnect using the Victron Direct port signal coming from either the Cerbo, BMS or the BMV.

I am pretty deep into the weeds on this so any or all feedback is appreciated,

 

Doug Smith

S/V Aventura, Amel 54-113

Patuxent River, MD USA


Doug Smith
 

Hello group and apologies for such a very specific question.  This is regarding the ‘stop charging’ cutoff for the 24V Mastervolt alternator with respect to a Lithium house bank.

I have reviewed everything I can find within our internal group email messages on this subject and have found great value in the education I have received. Also scoured the Victron site, Wil Prouse’s videos, PYS and the Marine How To web site for more information.

 

I have spent the last few weeks mapping out the transition of the equipment I currently have and drawing my schematics for the upgrade to Lithium over the next 12-18 months.

My schematic is attached for planned system. I agree with the idea of one vendor for the system, and have a mostly Victron layout to begin with so will continue that direction. 

Phase 1, installed already or over this winter

Cerbo GX, with Touch GX for display, mounted in battery compartment with the display on the forward bulkhead of the passage berth at eye level.

BMV-712 replacing the Xantrex.

Skylla-I 24|100|1+1 battery charger

Sterling Alternator Protect Device

Currently have a Mastervolt, 24-2500 Mass sine wave inverter, 24/24 inverter, and 24/12 inverters

Phase 2, next winter

We will upgrade to the quattro with the Digital Multi Control panel in the second phase with necessary cabling as required

Solar Arch with Panels, and Smart Solar MPPT controller.

Alpha Pro III, upgrading from the Alpha Pro. Keeping the original Mastervolt 24/110 alternator.

Phase 3, will be to switch to Victron Lithium and BMS when current AGM’s reach end of life cycle and my own full time retirement begins

 

Scott’s email from SV Tengah described a method of cutting off the Volvo Alternator charging circuit using external relays and using the battery disconnect signal from the VE.BMS to control when the cutoff relay would disconnect the Alpha Pro regulator. This disconnect would be set at a level lower than full voltage, and it appears he set it around 26.5 for float.

Arno, Mark, Bill and others have commented on using Coulomb counters for amount of current out-in to measure when the SOC is nearing 90-100%. 

What I am raising as a question is “why not use the BMV – 712 self-contained relay, as the method to cut off the alternator charging when either or both the voltage hits a threshold or the SOC is near capacity?”  There is an internal relay on the back of the BMV-712, with both normally open and normally closed contacts that is bi-directionally stable, with low current draw, and a built in option to activate the relay using a logic circuit of both voltage and SOC based on a low and a high threshold.  Then use the Alpha Pro “activate and disconnect relays” in the box that are activated when the volvo is running by means of the ignition circuit. When SOC is 90%, it would disconnect the alternator ignition circuit using the relays in the regulator box. Also, does anyone have better information about how those relays are connected to the ignition circuit? I have attached what I have found, but not sure if any of this impacts the circuits running the engine or its system electronics. This would appear to simplify the concerns, but I am worried I am missing something.

A second option is a Cryix-Li-ct 12/24-120 relay.  This would be one more Victron component to add, but appears to be a way to disconnect using the Victron Direct port signal coming from either the Cerbo, BMS or the BMV.

I am pretty deep into the weeds on this so any or all feedback is appreciated,

 

Doug Smith

S/V Aventura, Amel 54-113

Patuxent River, MD USA