Firefly batteries


Paul Dowd and Sharon Brown
 

Hi all,

 

I am curious to know if anyone has any experience with Firefly batteries, and if so whether they are recommended.

 

Cheers,

Paul

 

Paul Dowd & Sharon Brown

S/Y Ya Fohi, Amel 54 #98
tel: +44 (0)7710 466619

skype: pauldowd
web:
https://my.yb.tl/yafohi

 


--
Cheers
Paul
Ya Fohi - Amel 54 #98


Mark Erdos
 

If you search this group you will find extensive postings regarding Fireflys from sv Harmonie. Or you can look on their website: https://fetchinketch.net

 

 

 

With best regards,

 

Mark

 

Skipper

Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising - Tahiti, French Polynesia

www.creampuff.us

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of Paul Dowd and Sharon Brown
Sent: Thursday, October 7, 2021 9:30 AM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] Firefly batteries

 

Hi all,

 

I am curious to know if anyone has any experience with Firefly batteries, and if so whether they are recommended.

 

Cheers,

Paul

 

Paul Dowd & Sharon Brown

S/Y Ya Fohi, Amel 54 #98
tel: +44 (0)7710 466619

skype: pauldowd
web:
https://my.yb.tl/yafohi

 


--
Cheers
Paul
Ya Fohi - Amel 54 #98


Michael Winand
 

Hi Paul,  we installed firefly batteries 2 years ago,  happy with them,  I have experience with wet cell batteries,  firefly are easier to maintain.  I can't compare them with gels or agm styles. 
We have a large frame 175amp alternator,  1kw solar, 5kw quattro,  we only use the genset if we have limited sunshine. 
Can run 1 aircon during the day on a hot summer day. 
Michael Nebo sm251 

On Fri, 8 Oct 2021, 5:30 am Paul Dowd and Sharon Brown, <paul.dowd@...> wrote:

Hi all,

 

I am curious to know if anyone has any experience with Firefly batteries, and if so whether they are recommended.

 

Cheers,

Paul

 

Paul Dowd & Sharon Brown

S/Y Ya Fohi, Amel 54 #98
tel: +44 (0)7710 466619

skype: pauldowd
web:
https://my.yb.tl/yafohi

 


--
Cheers
Paul
Ya Fohi - Amel 54 #98


Mike Longcor (SV Trilogy)
 

Installed ours in May 2019. I give them a thumbs up. It's comforting to know that they can be in a partial SOC without causing significant damage or drastically shortening their lifespan. Will be interesting to see how long they actually do last, cycling pretty much every day. They're technically an AGM battery, carbon foam AGM. Ideally they get topped up to 100% once a week. And should get a periodic "restoration charge", which we've only done a couple times because it's only really feasible with shore power. We weren't quite ready for a switch to lithium so we went with these.

Cheers,
Mike Longcor
SV Trilogy SM23
NZ


On Fri, Oct 8, 2021, 8:30 AM Paul Dowd and Sharon Brown <paul.dowd@...> wrote:

Hi all,

 

I am curious to know if anyone has any experience with Firefly batteries, and if so whether they are recommended.

 

Cheers,

Paul

 

Paul Dowd & Sharon Brown

S/Y Ya Fohi, Amel 54 #98
tel: +44 (0)7710 466619

skype: pauldowd
web:
https://my.yb.tl/yafohi

 


--
Cheers
Paul
Ya Fohi - Amel 54 #98


Jamie Wendell
 

Paul, I had them installed several years ago and they all failed to deliver for me after a couple of years. The issue was always voltage drop under high loads like bow thrusters, etc. Eventually, I could not keep them charged properly - I had low-voltage alarms almost every night.
I do not want to dissuade you from taking that route, as I know others have used them successfully.
Maybe I am a unique situation with higher than average loads, but I am just reporting my bad experience. I ditched them for LiFePO4 batteries 2 years ago. Without any doubt, the lithiums have been excellent, with the most significant feature being (to me) that they retain a constant voltage throughout the discharge cycle.
I will never return to any type of lead-acid batteries. Keep in mind that Fireflys are a type of lead-acid battery, albeit with the added benefit of carbon foam.
Hope that gives you my perspective.
Jamie
Phantom, A54 #44


Bill Kinney
 

Paul,

We have a full set of Firefly batteries, and love them.  We periodically do a complete discharge to dead flat, and a rapid recharge as Firefly recommends as a "restoration charge."  Every time we we have done this we carefully monitor the amount of power discharged.  Each time the amount of power they have delivered has been above the original specification sheet value, and it is still the same as the day we installed them. The last I looked, it seemed that Firefly bumped up the rated specification of the batteries from 116A-hr to 120A-hr which is more in line with what we measure. We take good care of them, but while out on the hook, we certainly do not bring them fully charged every day.  They don't care.

For the way we use our boat, they give us all the benefit that a set of Lithiums would, at a significant discount.  They never have had any trouble with powering the bow thruster, or high loads out of the inverter.  At a steady 50 amp draw the voltage stays remarkably steady all the way down to about 15% SOC.

Some issues to watch for:

Firefly recommends that the batteries be charged at between 0.2 and 0.5C My recollection of a 54 is that you have 12 G31 batteries.  That would give you a bank of 720 A-hrs.  Charging that large a back at a rate of 0.2*720 = 144 Amps might be a challenge with a standard charging setup.  Our older SM has a 480 A-hr battery bank.  We have a DC generator that outputs 150 amps at 24 volts, so it fits well within the minimums recommended.  If you can't reach the recommended minimums, they request you talk to their technical staff for an alternative procedure.  I don't know what this is, but  it might be worth investigating up front if it might be an issue for you.

Early in their production run Firefly had difficulty with the occasional battery developing a shorted cell.  Left undetected, this can bring down the entire bank  in short order because of charge imbalances.  It is not a problem unique to these batteries, any type of lead acid battery can have this problem, but it seemed Firefly had more than their fair share.  We had this happen to us, and Firefly was 100% helpful and completely took care of us under warrantee. Our current monitoring system doesn't allow this to happen without us knowing about it very quickly.

We have 615W of solar. Our normal daily power usage is about 3kW-hrs, and solar can make about half this. During our normal charging cycle while at anchor in good weather we end up in the morning at about 75% SOC.  Over a sunny day, the solar panels bring the batteries up to about 90%.  The next morning, the batteries drop to about 60-65% SOC.  The generator starts in the early morning, runs for 80 to 90 minutes, and brings the bank up to 93% where it shuts down, and the solar panels have the bank at 100% by 3PM.  And the same two day cycle repeats.

We find we get excellent utilization for the power available from our solar panels, and the generator runs most of its time at high load, where it is most efficient.  For us, minimizing expensive generator run time is important.

We have looked very hard, and sharpened our pencils a lot, and for us we just don't see a benefit to Li batteries that justify the higher costs.  But every boat works differently, and everybody has different needs.

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA


Paul Dowd and Sharon Brown
 

Thank you Bill and all others who have responded. The feedback has been very helpful, and it is quite likely that I will go for the Fireflys. I had in mind 12 x G31s so nice to have that corroboration. Bill you mention briefly about your monitoring system. Could you possibly elaborate a bit on exactly what that is?

 

Cheers,

Paul

 

Paul Dowd & Sharon Brown

S/Y Ya Fohi, Amel 54 #98
tel: +44 (0)7710 466619

skype: pauldowd
web:
https://my.yb.tl/yafohi

 

From: main@AmelYachtOwners.groups.io <main@AmelYachtOwners.groups.io> On Behalf Of Bill Kinney
Sent: 08 October 2021 06:09
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] Firefly batteries

 

Paul,

We have a full set of Firefly batteries, and love them.  We periodically do a complete discharge to dead flat, and a rapid recharge as Firefly recommends as a "restoration charge."  Every time we we have done this we carefully monitor the amount of power discharged.  Each time the amount of power they have delivered has been above the original specification sheet value, and it is still the same as the day we installed them. The last I looked, it seemed that Firefly bumped up the rated specification of the batteries from 116A-hr to 120A-hr which is more in line with what we measure. We take good care of them, but while out on the hook, we certainly do not bring them fully charged every day.  They don't care.

For the way we use our boat, they give us all the benefit that a set of Lithiums would, at a significant discount.  They never have had any trouble with powering the bow thruster, or high loads out of the inverter.  At a steady 50 amp draw the voltage stays remarkably steady all the way down to about 15% SOC.

Some issues to watch for:

Firefly recommends that the batteries be charged at between 0.2 and 0.5C My recollection of a 54 is that you have 12 G31 batteries.  That would give you a bank of 720 A-hrs.  Charging that large a back at a rate of 0.2*720 = 144 Amps might be a challenge with a standard charging setup.  Our older SM has a 480 A-hr battery bank.  We have a DC generator that outputs 150 amps at 24 volts, so it fits well within the minimums recommended.  If you can't reach the recommended minimums, they request you talk to their technical staff for an alternative procedure.  I don't know what this is, but  it might be worth investigating up front if it might be an issue for you.

Early in their production run Firefly had difficulty with the occasional battery developing a shorted cell.  Left undetected, this can bring down the entire bank  in short order because of charge imbalances.  It is not a problem unique to these batteries, any type of lead acid battery can have this problem, but it seemed Firefly had more than their fair share.  We had this happen to us, and Firefly was 100% helpful and completely took care of us under warrantee. Our current monitoring system doesn't allow this to happen without us knowing about it very quickly.

We have 615W of solar. Our normal daily power usage is about 3kW-hrs, and solar can make about half this. During our normal charging cycle while at anchor in good weather we end up in the morning at about 75% SOC.  Over a sunny day, the solar panels bring the batteries up to about 90%.  The next morning, the batteries drop to about 60-65% SOC.  The generator starts in the early morning, runs for 80 to 90 minutes, and brings the bank up to 93% where it shuts down, and the solar panels have the bank at 100% by 3PM.  And the same two day cycle repeats.

We find we get excellent utilization for the power available from our solar panels, and the generator runs most of its time at high load, where it is most efficient.  For us, minimizing expensive generator run time is important.

We have looked very hard, and sharpened our pencils a lot, and for us we just don't see a benefit to Li batteries that justify the higher costs.  But every boat works differently, and everybody has different needs.

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA


--
Cheers
Paul
Ya Fohi - Amel 54 #98


Bill Kinney
 

Paul,

Our electrical system is basically all Victron and we have installed their Cerbo GX to monitor and control all the bits and pieces.  The key key piece for the batteries is the BMV Battery Monitor.  In addition to all the usual functions of bank voltage and amp usage tracking, it can monitor the difference between the "top" of the bank and the "bottom".

All the batteries on the 0 to 12 volt side are tied together. Likewise, all of them on the 12 to 24 volt side.  In the ideal world, the voltage inside each group would be exactly one half of the overall bank voltage, or (nominally) 12 volts. If a single battery was to develop an internal short that half of the battery bank would drop in voltage, and the other half would rise, increasing the difference between them.

Normally our batteries run with a 0.00V difference. Toward the end of a hard charging cycle we can see up to a 0.04V difference.  We have an alarm set to flag if the difference gets above 0.06V.  So far, it has never gone off.

I have attached the voltage graph from our last full discharge and rapid recharge.  The discharge rate was pretty steady at 50 Amps for about 10 hours.  The charge rate was all the batteries could take, or 200 Amps whichever came first. It was pretty warm that day, so the absorption voltage was a bit lower than you might expect.  The top and bottom difference increased as the batteries approached fully empty, during the steepest part of the bulk phase, and in the middle of the absorption phase, all of which is normal behavior.



Bill Kinney
SM160, Harmonie
Annapolis, MD, USA


Arno Luijten
 

Hi Paul,

Be careful with the size of the Firefly batteries. I did not manage to get 12 batteries in the cavity. I’m not sure how many I now have as I’m not close to the boat but I do know these batteries are slightly bigger then the size Amel used initially. The Firefly’s are 120Ah and the default Amels were 105Ah.
The batteries perform well for me however I do find the voltage to be a bit lower then AGM at the same state of charge.

Cheers,
Arno Luijten
SV Luna,
A54-121 


Paul Dowd and Sharon Brown
 

Hi Bill,

 

When you say this:

 

All the batteries on the 0 to 12 volt side are tied together. Likewise, all of them on the 12 to 24 volt side

 

Do you mean that the low side batteries of each 24v pair are all connected together with all their negative terminals, and similarly the high side?

 

Another possible hitch is that I’ve been told by a UK supplier that FF recommends no more than four pairs, but I believe you mentioned that a 54 would normally take 12. Would you know anything about this? It is the G31s I’m talking about.

 

Hi Arno,

 

You say that 12 batteries would not fit. I note you have hull 121 and wonder if Amel may have resized the compartment in the interim from #98? According to my measurements on record it will be 2mm short on the width but assume some inaccuracy in this measurement.

 

Cheers,

Paul

 

Paul Dowd & Sharon Brown

S/Y Ya Fohi, Amel 54 #98
tel: +44 (0)7710 466619

skype: pauldowd
web:
https://my.yb.tl/yafohi

 

From: main@AmelYachtOwners.groups.io <main@AmelYachtOwners.groups.io> On Behalf Of Bill Kinney
Sent: 08 October 2021 14:54
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] Firefly batteries

 

Paul,

Our electrical system is basically all Victron and we have installed their Cerbo GX to monitor and control all the bits and pieces.  The key key piece for the batteries is the BMV Battery Monitor.  In addition to all the usual functions of bank voltage and amp usage tracking, it can monitor the difference between the "top" of the bank and the "bottom".

All the batteries on the 0 to 12 volt side are tied together. Likewise, all of them on the 12 to 24 volt side.  In the ideal world, the voltage inside each group would be exactly one half of the overall bank voltage, or (nominally) 12 volts. If a single battery was to develop an internal short that half of the battery bank would drop in voltage, and the other half would rise, increasing the difference between them.

Normally our batteries run with a 0.00V difference. Toward the end of a hard charging cycle we can see up to a 0.04V difference.  We have an alarm set to flag if the difference gets above 0.06V.  So far, it has never gone off.

I have attached the voltage graph from our last full discharge and rapid recharge.  The discharge rate was pretty steady at 50 Amps for about 10 hours.  The charge rate was all the batteries could take, or 200 Amps whichever came first. It was pretty warm that day, so the absorption voltage was a bit lower than you might expect.  The top and bottom difference increased as the batteries approached fully empty, during the steepest part of the bulk phase, and in the middle of the absorption phase, all of which is normal behavior.



Bill Kinney
SM160, Harmonie
Annapolis, MD, USA


--
Cheers
Paul
Ya Fohi - Amel 54 #98


Matt Salatino
 

I installed Fireflys on my previous boat.
many of the benefits of Lithium, except the weight.
They will also charge using your conventional chargers.
I was pleased. I replaced a 600 amp hour, standard AGM house bank with 348 amp hour Fireflys and didn’t notice any reduction in usage, as you can discharge them deeper than conventional lead acid without damage.
today’s concern is that I can now find Lithium for similar prices as Firefly.


Arno Luijten
 

Hi Paul,

I doubt Amel changed the size of the cavity. I ordered the batteries with a fellow 54 owner with a much earlier hull number and he had he same problem. I do know the problem was in the few centimeters region but that is all it takes to prevent you from installing 13 (12+1) batteries in the cavity.
Keep in mind that the cavity is much bigger then the hole you have to put the batteries trough. I’m not sure anymore but that may have been the problem in the end. It was like playing Tetris with very heavy batteries. 

Cheers,

Arno
SV Luna,
A54-121


Bill Kinney
 

Paul,

Our batteries are connected like this:



(Except with 8 instead of 6).

You might want to check the information about the maximum battery back that can be created.  I KNOW that they do not recommend connecting more than 4 in SERIES (as you would if you were making a 48Volt bank), but I can think of no reason that the number of parallel batteries would be limited. My manual doesn't suggest any limit.

I found the terminals of the Firefly G31 batteries to be slightly taller than the Lifeline batteries they replaced, but our fitting isn't tight, so a bit of expansion in footprint I would not have noticed.  Generally, for any battery, it is not a great idea to have them pressed tightly together. They need a bit of air space to lose heat..  Firefly suggests a minimum of 1cm between batteries.

I might be labeled a heretic but do you really NEED 12 batteries? We have never been in a situation where we felt we wanted more than the 8 our boat came with.  The Firefly batteries are happy with a deeper discharge profile than the FLA batteries the 54 was designed with.

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA


Paul Dowd and Sharon Brown
 

Hi Bill,

 

That’s interesting. Our Amel came with them as 6 pairs comprising 2 batteries in series, then all 6 in parallel. I guess there are pros and cons for each method.

 

Cheers,

Paul

 

Paul Dowd

Managing Director
FGPS Limited
Tel: +44(0)7710 466 619

skype: pauldowd
www.fgps.com

 

This e-mail (including attachments) may contain sensitive and/or confidential information. If received in error, its use by you is not authorised and may be unlawful. Please notify the sender and delete all copies immediately. E-mails may be subject to error, interference and virus and no liability is accepted for loss or damage however it arises and whether direct or indirect.

 

From: main@AmelYachtOwners.groups.io <main@AmelYachtOwners.groups.io> On Behalf Of Bill Kinney
Sent: 10 October 2021 21:19
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] Firefly batteries

 

Paul,

Our batteries are connected like this:



(Except with 8 instead of 6).

You might want to check the information about the maximum battery back that can be created.  I KNOW that they do not recommend connecting more than 4 in SERIES (as you would if you were making a 48Volt bank), but I can think of no reason that the number of parallel batteries would be limited. My manual doesn't suggest any limit.

I found the terminals of the Firefly G31 batteries to be slightly taller than the Lifeline batteries they replaced, but our fitting isn't tight, so a bit of expansion in footprint I would not have noticed.  Generally, for any battery, it is not a great idea to have them pressed tightly together. They need a bit of air space to lose heat..  Firefly suggests a minimum of 1cm between batteries.

I might be labeled a heretic but do you really NEED 12 batteries? We have never been in a situation where we felt we wanted more than the 8 our boat came with.  The Firefly batteries are happy with a deeper discharge profile than the FLA batteries the 54 was designed with.

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA


--
Cheers
Paul
Ya Fohi - Amel 54 #98


Jamie Wendell
 

Bill, can you elaborate on your setup. The way you show the drawing it appears as if you actually have 36 volts per "leg" vs 24 volts. I may be misunderstanding the drawing, but I doubt that is the case.
Either way, the issue with series connections is that you have to ensure all in-series batteries are balanced. That is one of the main reasons to limit the number of batteries connected in series, and is a strong incentive to go with 24-volt batteries if possible.
I know that the Fireflys are 12 volts.
Jamie
Phantom, A54 #44


 

How to wire the battery bank can certainly be debated and the "expert" Nigel Calder will tell you the Henri Amel method is wrong. Others will try to convince you of this also. But, I have been on the other end of a conversation with a panicked owner with a shorted battery. With Henri's method, it is very easy to explain how to remove a pair of batteries. With Nigel Calder's method, it is nearly impossible to explain how to isolate a problem battery. I think I know why Henri made his decision.

Who's method is better? Actually, Nigel Calder's method is technically better in terms of battery balance and may result in 1-5% longer life, but do not call me when you have a problem. I believe that 1-5% improvement is not worth the risk unless you are very familiar with the wiring you choose, as some of you are.😀 I chose not to use Nigel Calder's method.

I am sure that you understand what I am saying.

Bill


CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar

On Mon, Oct 11, 2021 at 8:02 AM Jamie Wendell <mysticshadow54@...> wrote:
Bill, can you elaborate on your setup. The way you show the drawing it appears as if you actually have 36 volts per "leg" vs 24 volts. I may be misunderstanding the drawing, but I doubt that is the case.
Either way, the issue with series connections is that you have to ensure all in-series batteries are balanced. That is one of the main reasons to limit the number of batteries connected in series, and is a strong incentive to go with 24-volt batteries if possible.
I know that the Fireflys are 12 volts.
Jamie
Phantom, A54 #44


Bill Kinney
 

Jamie,

The drawing is correct, and generates 24 volts.  A full explanation is here:  https://fetchinketch.net/boat_thoughts/battery-connections/(opens in a new tab)

The common connection across the "middle" of the bank allows a single battery balancer to keep the batteries high and low at the same voltage during charging. It also makes certain that load and charging current is evenly shared between every battery in the system. It also allows us to easily measure and detect a single badly performing battery by monitoring the voltages of the upper and lower halves of the bank.  https://www.victronenergy.com/upload/documents/Datasheet-Battery-Balancer-EN.pdf

In any multiple battery system the important thing is to be sure that the batteries share the load and the charging current and voltages as identically as possible. If this is not done, over time some batteries are chronically undercharged, and others are overcharged. This will shorten the lifespan of the bank as a whole, and increases the chance of a "shorted" battery to kill all the others.

For batteries like flooded lead acid that are regularly equalized this this isn't so much an issue, the equalization process balances the batteries.  Gel and AGM batteries typically are NOT equalized, and therefore need more attention to this.  It is possible that the regular "restoration charges" that Firefly recommends (and that we do) fully addresses this issue, but the addition of the balancer gives me an extra level of comfort that everything is charging evenly. Our measurements support that this has been effective.

It's useful to remember that with the system as installed by Amel, batteries were expect to be replaced OFTEN.  In the Super Maramu owner's manual Amel says that for a boat that spends most of its time at anchor the lifespan of the batteries "will probably not exceed 18 months." As battery technology has improved, including much more sophisticated charging systems that let us keep our batteries closer to full more of the time, they last a lot longer.  

If you install inexpensive batteries and change them often, you can get away with systems that are simpler than if you use more expensive batteries and more careful controls.  Neither choice is better than the other, they are different and suit different styles of boat use and owner involvement in the details.

Bill Kinney
SM160, Harmonie
Annapolis, MD


Paul Dowd and Sharon Brown
 

Hi Bill,

 

That’s very useful to know. Just one thing that occurred to me, do you have any cable specs for this arrangement? Presumably I would replace the Amel installed six +ive & -ive cables with a two of a bigger gauge?

 

Cheers,

Paul

 

Paul Dowd & Sharon Brown

S/Y Ya Fohi, Amel 54 #98
tel: +44 (0)7710 466619

skype: pauldowd
web:
https://my.yb.tl/yafohi

 

From: main@AmelYachtOwners.groups.io <main@AmelYachtOwners.groups.io> On Behalf Of Bill Kinney
Sent: 11 October 2021 20:14
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] Firefly batteries

 

Jamie,

The drawing is correct, and generates 24 volts.  A full explanation is here:  https://fetchinketch.net/boat_thoughts/battery-connections/(opens in a new tab)

The common connection across the "middle" of the bank allows a single battery balancer to keep the batteries high and low at the same voltage during charging. It also makes certain that load and charging current is evenly shared between every battery in the system. It also allows us to easily measure and detect a single badly performing battery by monitoring the voltages of the upper and lower halves of the bank.  https://www.victronenergy.com/upload/documents/Datasheet-Battery-Balancer-EN.pdf

In any multiple battery system the important thing is to be sure that the batteries share the load and the charging current and voltages as identically as possible. If this is not done, over time some batteries are chronically undercharged, and others are overcharged. This will shorten the lifespan of the bank as a whole, and increases the chance of a "shorted" battery to kill all the others.

For batteries like flooded lead acid that are regularly equalized this this isn't so much an issue, the equalization process balances the batteries.  Gel and AGM batteries typically are NOT equalized, and therefore need more attention to this.  It is possible that the regular "restoration charges" that Firefly recommends (and that we do) fully addresses this issue, but the addition of the balancer gives me an extra level of comfort that everything is charging evenly. Our measurements support that this has been effective.

It's useful to remember that with the system as installed by Amel, batteries were expect to be replaced OFTEN.  In the Super Maramu owner's manual Amel says that for a boat that spends most of its time at anchor the lifespan of the batteries "will probably not exceed 18 months." As battery technology has improved, including much more sophisticated charging systems that let us keep our batteries closer to full more of the time, they last a lot longer.  

If you install inexpensive batteries and change them often, you can get away with systems that are simpler than if you use more expensive batteries and more careful controls.  Neither choice is better than the other, they are different and suit different styles of boat use and owner involvement in the details.

Bill Kinney
SM160, Harmonie
Annapolis, MD


--
Cheers
Paul
Ya Fohi - Amel 54 #98


Scott SV Tengah
 

FWIW, my Victron batteries (Smart lifepo4 12.8v) documentation explicitly states "Do not interconnect the midpoints". See drawing on bottom of page1. FYI the gray lines are the data cables for the BMS.

https://www.victronenergy.com/upload/documents/Datasheet-12,8-&-25,6-Volt-lithium-iron-phosphate-batteries-Smart-EN.pdf

When I installed my system 3 years ago, I wanted to connect the midpoints and use a battery balancer and decided against it. 

Perhaps this is not an issue with Fireflies/AGM/Gel/FLA.

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


Mike Longcor (SV Trilogy)
 

Without midpoint voltage monitoring, connecting the mid points is not recommended as it will mask a battery problem.

From Victron (BMV manual):
"Midpoints should not be interconnected: one bad battery can go unnoticed and could damage all other batteries."

We run our six Fireflys in series parallel with 3 individual balancers. Feels like overkill but it works well. With an upgraded battery monitor, I would probably connect the midpoints so loads and charges are more evenly shared.

Cheers,
Mike Longcor
SV Trilogy SM23
NZ


On Tue, Oct 12, 2021, 8:58 AM Scott SV Tengah <Scott.nguyen@...> wrote:
FWIW, my Victron batteries (Smart lifepo4 12.8v) documentation explicitly states "Do not interconnect the midpoints". See drawing on bottom of page1. FYI the gray lines are the data cables for the BMS.

https://www.victronenergy.com/upload/documents/Datasheet-12,8-&-25,6-Volt-lithium-iron-phosphate-batteries-Smart-EN.pdf

When I installed my system 3 years ago, I wanted to connect the midpoints and use a battery balancer and decided against it. 

Perhaps this is not an issue with Fireflies/AGM/Gel/FLA.

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