Date   

Re: Anchor sizing

Germain Jean-Pierre
 

We have a 35kg ultra with the ultra swivel.  As a RTW couple, we anchor 10 to 11 months a year.

To date, we have never dragged anchor... but we are very careful about setting our anchor.  The Ultra is a very good piece of equipment and we can recommend it unconditionally.

A Rocna would also do a good job.

Cheers

Jean-Pierre Germain, SY Eleuthera, SM007, New Zealand


On 13 Sep 2020, at 19:32, Randall <sailingalbedo@...> wrote:



Slight rewording.

If you don't want to ever end up on youtube for the wrong reason, bigger is better. Your Wasi was chosen by Amel as a good size and would do fine. But for peace of mind. the recommended weight by the manufacturer is always one size too small. Go Bigger!!!!
On my 54 the choice for peace of mind is the 45KG/100LB Ultra is the best. But the weight is more important than shine. So the other choices of Rocna, Mantus, Plow, etc. will work fine.

Randall
A54 #56
Gibraltar

On Sun, Sep 13, 2020 at 9:20 AM The Boat <sailingalbedo@...> wrote:
If you don't want to ever end up on youtube for the wrong reason, bigger is better. Your Wasi was chosen by Amel as a good size and would do fine. But for peace of mind. the recommended is always one size too small.
On my 54 the choice for peace of mind is the 45KG/100LB Ultra is the best. But the weight is more important than shine. So the other choices of Rocna, Mantus, Plow will work fine.

Randall
A54 #56
Gibraltar

On Sun, Sep 13, 2020 at 7:49 AM Bryce Procter via groups.io <Balibryce=yahoo.com@groups.io> wrote:
At the risk of opening a hornets nest I am replacing my 30kg Wasi Bugle anchor with one of the newer breed of anchors. My query is not about which brand or shackles or style though rather sizing.
Assuming the following that the boat is usually fully loaded for extended cruising so in the heavier weight range, occasionally left alone at anchor normally for no more than a day or two though in these times anything is possible;100m of chain, varying bottom types, don't intend to carry a dedicated "storm" anchor etc etc. Based on these and the endless other variables does anyone have any advice or thoughts on the best size/weight?
I have seen SM's being swapped out with anywhere from 30kg to 45kg Rocnas, Mantus or other newer style anchors. One piece of advice I read sometime ago was that if the other yachties at the dock aren't laughing at your anchor it's not big enough!
Cheers

Bryce
SM 2K #467


Re: Anchor sizing

ngtnewington Newington
 

On my 54 Amel provided a 33kg Wasi, that I feel is slightly undersized for such a vessel. I also think the WASI, although a good anchor, is now out of date and has limited holding power. On board, when I purchased Amelia, was a 45Kg Delta that was set up as the primary anchor with the Wasi set up on the secondary port roller. 

I then switched them around and found the Wasi, although smaller than the Delta to be better all round than the Delta, although probably due only to it’s very sharp tip. I think the well set Delta would have greater holding power. The Delta however was harder to set. 

I was never happy with either as my main anchor; so after much research I purchased a 37Kg Spade that I am delighted with. Only the other day at anchor in Leros on very good holding, after two days of 25-30kn Meltemi. It was a beast to raise. Even on 1:1 scope It required 1500 RPM to even budge.

For a SM, which is pretty much the same size and weight as the 54 I completely agree 30Kg Wasi is really not big and modern enough for peace of mind.

I would go for either an Ultra or a Spade between 35Kg and 45Kg. My experience with the 37 Kg Spade is that if set in good holding ground it will not budge no matter how hard it blows. This would be over 20% heavier than the original Wasi supplied by Amel and for sure a much better anchor. 

Nick
Amelia (AML 54- 019) stored ashore in Leros.

On 13 Sep 2020, at 08:31, Randall <sailingalbedo@...> wrote:


Slight rewording.

If you don't want to ever end up on youtube for the wrong reason, bigger is better. Your Wasi was chosen by Amel as a good size and would do fine. But for peace of mind. the recommended weight by the manufacturer is always one size too small. Go Bigger!!!!
On my 54 the choice for peace of mind is the 45KG/100LB Ultra is the best. But the weight is more important than shine. So the other choices of Rocna, Mantus, Plow, etc. will work fine.

Randall
A54 #56
Gibraltar

On Sun, Sep 13, 2020 at 9:20 AM The Boat <sailingalbedo@...> wrote:
If you don't want to ever end up on youtube for the wrong reason, bigger is better. Your Wasi was chosen by Amel as a good size and would do fine. But for peace of mind. the recommended is always one size too small.
On my 54 the choice for peace of mind is the 45KG/100LB Ultra is the best. But the weight is more important than shine. So the other choices of Rocna, Mantus, Plow will work fine.

Randall
A54 #56
Gibraltar

On Sun, Sep 13, 2020 at 7:49 AM Bryce Procter via groups.io<Balibryce=yahoo.com@groups.io> wrote:
At the risk of opening a hornets nest I am replacing my 30kg Wasi Bugle anchor with one of the newer breed of anchors. My query is not about which brand or shackles or style though rather sizing.
Assuming the following that the boat is usually fully loaded for extended cruising so in the heavier weight range, occasionally left alone at anchor normally for no more than a day or two though in these times anything is possible;100m of chain, varying bottom types, don't intend to carry a dedicated "storm" anchor etc etc. Based on these and the endless other variables does anyone have any advice or thoughts on the best size/weight?
I have seen SM's being swapped out with anywhere from 30kg to 45kg Rocnas, Mantus or other newer style anchors. One piece of advice I read sometime ago was that if the other yachties at the dock aren't laughing at your anchor it's not big enough!
Cheers

Bryce
SM 2K #467




Re: Anchor sizing

Bryce Procter
 

Thanks Randall, the 45 ULTRA was my original choice and after looking at it I'm sure it will get a few grins/smirks on the dock. Though along your line of thought I would rather have the peace of mind and not be wondering/hoping that the anchor holds when that unexpected 40 knot squall comes through while on shore or away. 



Re: Anchor sizing

Randall Walker
 


Slight rewording.

If you don't want to ever end up on youtube for the wrong reason, bigger is better. Your Wasi was chosen by Amel as a good size and would do fine. But for peace of mind. the recommended weight by the manufacturer is always one size too small. Go Bigger!!!!
On my 54 the choice for peace of mind is the 45KG/100LB Ultra is the best. But the weight is more important than shine. So the other choices of Rocna, Mantus, Plow, etc. will work fine.

Randall
A54 #56
Gibraltar


On Sun, Sep 13, 2020 at 9:20 AM The Boat <sailingalbedo@...> wrote:
If you don't want to ever end up on youtube for the wrong reason, bigger is better. Your Wasi was chosen by Amel as a good size and would do fine. But for peace of mind. the recommended is always one size too small.
On my 54 the choice for peace of mind is the 45KG/100LB Ultra is the best. But the weight is more important than shine. So the other choices of Rocna, Mantus, Plow will work fine.

Randall
A54 #56
Gibraltar

On Sun, Sep 13, 2020 at 7:49 AM Bryce Procter via groups.io <Balibryce=yahoo.com@groups.io> wrote:
At the risk of opening a hornets nest I am replacing my 30kg Wasi Bugle anchor with one of the newer breed of anchors. My query is not about which brand or shackles or style though rather sizing.
Assuming the following that the boat is usually fully loaded for extended cruising so in the heavier weight range, occasionally left alone at anchor normally for no more than a day or two though in these times anything is possible;100m of chain, varying bottom types, don't intend to carry a dedicated "storm" anchor etc etc. Based on these and the endless other variables does anyone have any advice or thoughts on the best size/weight?
I have seen SM's being swapped out with anywhere from 30kg to 45kg Rocnas, Mantus or other newer style anchors. One piece of advice I read sometime ago was that if the other yachties at the dock aren't laughing at your anchor it's not big enough!
Cheers

Bryce
SM 2K #467


Re: Anchor sizing

Randall Walker
 

If you don't want to ever end up on youtube for the wrong reason, bigger is better. Your Wasi was chosen by Amel as a good size and would do fine. But for peace of mind. the recommended is always one size too small.
On my 54 the choice for peace of mind is the 45KG/100LB Ultra is the best. But the weight is more important than shine. So the other choices of Rocna, Mantus, Plow will work fine.

Randall
A54 #56
Gibraltar

On Sun, Sep 13, 2020 at 7:49 AM Bryce Procter via groups.io <Balibryce=yahoo.com@groups.io> wrote:
At the risk of opening a hornets nest I am replacing my 30kg Wasi Bugle anchor with one of the newer breed of anchors. My query is not about which brand or shackles or style though rather sizing.
Assuming the following that the boat is usually fully loaded for extended cruising so in the heavier weight range, occasionally left alone at anchor normally for no more than a day or two though in these times anything is possible;100m of chain, varying bottom types, don't intend to carry a dedicated "storm" anchor etc etc. Based on these and the endless other variables does anyone have any advice or thoughts on the best size/weight?
I have seen SM's being swapped out with anywhere from 30kg to 45kg Rocnas, Mantus or other newer style anchors. One piece of advice I read sometime ago was that if the other yachties at the dock aren't laughing at your anchor it's not big enough!
Cheers

Bryce
SM 2K #467


Anchor sizing

Bryce Procter
 

At the risk of opening a hornets nest I am replacing my 30kg Wasi Bugle anchor with one of the newer breed of anchors. My query is not about which brand or shackles or style though rather sizing.
Assuming the following that the boat is usually fully loaded for extended cruising so in the heavier weight range, occasionally left alone at anchor normally for no more than a day or two though in these times anything is possible;100m of chain, varying bottom types, don't intend to carry a dedicated "storm" anchor etc etc. Based on these and the endless other variables does anyone have any advice or thoughts on the best size/weight?
I have seen SM's being swapped out with anywhere from 30kg to 45kg Rocnas, Mantus or other newer style anchors. One piece of advice I read sometime ago was that if the other yachties at the dock aren't laughing at your anchor it's not big enough!
Cheers

Bryce
SM 2K #467


locked Re: Batteries starting to get weak - MMM - What to do -

Scott SV Tengah
 

Mark/Arno,

Arno pointed out one huge problem with using voltage as an indicator of SOC and a trigger to start charging. While lithium has a much flatter voltage profile than lead with respect to load, it still has a voltage drop under high loads. As mentioned, my bank drops into the mid 24v range when I'm running the bow thruster with engine/genset off. My load varies dramatically. We may be drawing only 60w but then suddenly the washer and dishwasher hit the heating part of their cycle and that is aligned with the misses using the microwave and we decide to run the water maker. Oh and the fridge compressors turn on. At that moment, we could easily go from 30w draw to 6000w draw. Additionally, you really need to monitor and act upon cell level voltage. You could easily have 26v at the battery/bank level but an imbalance has one cell at 4.2v, but unseen at the battery or bank voltage level. Keep feeding current and the battery is irreparably damaged.

Mark - you stated  "I think this high discharge rate has a significant impact on the Voltage vs. SOC results."  Based on this and our variable load, unless you are able to consistently let your batteries get to their resting voltage, I still think voltage is not useful for determining SOC. 

In my opinion, using voltage is a shortcut to try to make things easier. I am all for simplification as there is less to go wrong. But the manufacturers and the decades of academic research on lifepo4 all point to using a coulomb counter (like a BMV-712 or equivalent) to determine SOC and the target charging voltages are based on their research. Moreover, if I follow Victron's recommendations and a battery fails, they are on the warranty hook. They are incentivized to give you good information. It may be that the manufacturers and the decades of research and are wrong and that blogger and the MV guy is right, but I am not willing to risk my five figure lithium investment and my six figure boat on conclusions drawn from a sample size of two. I am certain the blogger wouldn't be providing warranty replacements if I tell him that I followed his advice and my batteries failed. :)

I am impressed that people are willing to go to the bleeding edge to save money. When I first started talking about installing a mostly-Victron system that was designed to work together, more than a few said that it was too risky to use "explosive" lithium. That was just two years ago. Now people are willing to mix and match batteries/chargers/BMS and trying non-standard charging routines. But I wouldn't be comfortable doing that on my boat on our intended, in-progress circumnavigation.

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


Zoom meeting - QSails owner/manager will present sails for Amels - Sat, 09/12/2020 #cal-notice

main@AmelYachtOwners.groups.io Calendar <noreply@...>
 

Zoom meeting - QSails owner/manager will present sails for Amels

When:
Saturday, 12 September 2020
20:00 to 21:00
(GMT+00:00) UTC

Description:
Time will be 2000 UTC.

Over 60 Amel owners have purchased sails from QSails, Izmir, Turkey. QSails has shipped these sails worldwide. Emrah Oge, owner, manager, and avid sailor will present how sails are made and some key points to be aware of in the selection of sails for your Amel. 

QSails offers very fast shipments of sails for many Amel models. In fact, many Amel sails are actually shipped from pre-made stock at QSails.

To ensure that you get the best quality and the best price, QSails and Amel owners have designed 3 simple choices for you of Good, Better, and Best:

GOOD - CrossCut AP Dacron is a quote for budget-minded Super Maramu owners who would like a Dacron polyester cross-cut sail similar to what Doyle Sails provides.
BETTER - TriRadial Cut Pro Radial Dimension/Polyant Dacron is a quote for those owners wanting a very high-quality Dacron Polyester fiber sailcloth from the German company Dimension-Polyant. It is cut and assembled in a TriRadial configuration. This is a slightly higher quality sail with the same TriRadial construction that your Super Maramu had when new.
BEST
- HydraNet TriRadial Cut is a quote for TriRadial Cut HydraNet from the German company Dimension-Polyant. I consider Dimension-Polyant the best sailcloth manufacturer in the world, and HydraNet the best sailcloth...it will not stretch.

Zoom link for the meeting:

Topic: AYOG Monthly Zoom Meeting: QSails

Time: Sep 12, 2020 20:00 Greenwich Mean Time

Join Zoom Meeting

https://epfl.zoom.us/j/94687396754

Meeting ID: 946 8739 6754

Link for the Youtube stream: https://youtu.be/nQob9dJu3RE

 


Re: Outhaul gear pulled in Annapolis

Karen Smith
 

We have found a puller that we can borrow! Amelia s are the best!

Regards, 
Karen Smith
S/v Harmonie SM #160
Bert Jabins Yacht Yard, Annapolis, MD




Zoom meeting - QSails owner/manager will present sails for Amels - Sat, 09/12/2020 20:00-21:00, Please RSVP #cal-reminder

main@AmelYachtOwners.groups.io Calendar <main@...>
 

Reminder: Zoom meeting - QSails owner/manager will present sails for Amels

When: Saturday, 12 September 2020, 20:00 to 21:00, (GMT+00:00) UTC

An RSVP is requested. Click here to RSVP

Description: Time will be 2000 UTC.

Over 60 Amel owners have purchased sails from QSails, Izmir, Turkey. QSails has shipped these sails worldwide. Emrah Oge, owner, manager, and avid sailor will present how sails are made and some key points to be aware of in the selection of sails for your Amel. 

QSails offers very fast shipments of sails for many Amel models. In fact, many Amel sails are actually shipped from pre-made stock at QSails.

To ensure that you get the best quality and the best price, QSails and Amel owners have designed 3 simple choices for you of Good, Better, and Best:

GOOD - CrossCut AP Dacron is a quote for budget-minded Super Maramu owners who would like a Dacron polyester cross-cut sail similar to what Doyle Sails provides.
BETTER - TriRadial Cut Pro Radial Dimension/Polyant Dacron is a quote for those owners wanting a very high-quality Dacron Polyester fiber sailcloth from the German company Dimension-Polyant. It is cut and assembled in a TriRadial configuration. This is a slightly higher quality sail with the same TriRadial construction that your Super Maramu had when new.
BEST
- HydraNet TriRadial Cut is a quote for TriRadial Cut HydraNet from the German company Dimension-Polyant. I consider Dimension-Polyant the best sailcloth manufacturer in the world, and HydraNet the best sailcloth...it will not stretch.

Zoom link for the meeting:

Topic: AYOG Monthly Zoom Meeting: QSails

Time: Sep 12, 2020 20:00 Greenwich Mean Time

Join Zoom Meeting

https://epfl.zoom.us/j/94687396754

Meeting ID: 946 8739 6754

Link for the Youtube stream: https://youtu.be/nQob9dJu3RE

 


locked Re: Batteries starting to get weak - MMM - What to do -

Matt Salatino
 

Had them on my previous boat. Excellent!

~~~⛵️~~~Matt

On Sep 12, 2020, at 5:08 PM, Mark McGovern <mfmcgovern@...> wrote:

Matt,

That is true and Firefly batteries are technically lead acid batteries.  They are just so unique and unlike "traditional" lead acid batteries that I put them in their own category.

--
Mark McGovern
SM #440 Cara
Deale, MD USA


locked Re: Batteries starting to get weak - MMM - What to do -

Mark McGovern
 

Matt,

That is true and Firefly batteries are technically lead acid batteries.  They are just so unique and unlike "traditional" lead acid batteries that I put them in their own category.

--
Mark McGovern
SM #440 Cara
Deale, MD USA


locked Re: Batteries starting to get weak - MMM - What to do -

Matt Salatino
 

Fire Fly doesn’t care if stored at 50% SOC

~~~⛵️~~~Matt

On Sep 12, 2020, at 3:29 PM, Mark McGovern <mfmcgovern@...> wrote:

Arno,

No problem.  That article that I linked to by Compass Marine is by far the most comprehensive that I have found regarding using LiFePO4 batteries in a marine electrical system.  I have read it many, many times and every time I re-read it I learn something new.

If I was not intending to move aboard full time and do extensive off-grid cruising, I would not have made the switch to LiFePO4.  The Firefly batteries you mentioned would be my choice for "part time" cruising.  They appear to have many of the same benefits of LiFePO4 regarding charge acceptance rate and Partial State of Charge use without the relative complexity and cost of installing a LiFePO system.

When thinking about SOC keep in mind that part of the beauty of LiFePO4 batteries is that, unlike Lead Acid batteries, they really don't care what the SOC is within a really wide range. They seem to be as happy at ~30% SOC as they are at ~90%.  They really just dislike the extremes, so the main job of the BMS (at least how Victron designs their BMS) is to keep the batteries from getting over-charged (over voltage) and getting over-discharged (under voltage) by cutting off charging source(s) or load(s).  Otherwise, the BMS doesn't really intervene in normal daily use (outside of intra-battery cell balancing which is a separate topic to itself and disallowing charging at temperatures below 5 deg C).

To give you some idea of the "new thinking" required with these batteries compared to Lead Acid when I took delivery of my batteries it was going to be several weeks before I could install them.  New batteries are delivered at about a 50% SOC.  When I asked my dealer how long I could leave them "as is" and what I needed to do to maintain them he said I could leave them that way for many months and probably years, and that I didn't need to do anything other than store them at a reasonable temperature.  Can you imagine what would happen to your Lead Acid batteries if they were left at 50% SOC for months?


--
Mark McGovern
SM #440 Cara
Deale, MD USA


locked Re: Batteries starting to get weak - MMM - What to do -

Mark McGovern
 

Arno,

No problem.  That article that I linked to by Compass Marine is by far the most comprehensive that I have found regarding using LiFePO4 batteries in a marine electrical system.  I have read it many, many times and every time I re-read it I learn something new.

If I was not intending to move aboard full time and do extensive off-grid cruising, I would not have made the switch to LiFePO4.  The Firefly batteries you mentioned would be my choice for "part time" cruising.  They appear to have many of the same benefits of LiFePO4 regarding charge acceptance rate and Partial State of Charge use without the relative complexity and cost of installing a LiFePO system.

When thinking about SOC keep in mind that part of the beauty of LiFePO4 batteries is that, unlike Lead Acid batteries, they really don't care what the SOC is within a really wide range. They seem to be as happy at ~30% SOC as they are at ~90%.  They really just dislike the extremes, so the main job of the BMS (at least how Victron designs their BMS) is to keep the batteries from getting over-charged (over voltage) and getting over-discharged (under voltage) by cutting off charging source(s) or load(s).  Otherwise, the BMS doesn't really intervene in normal daily use (outside of intra-battery cell balancing which is a separate topic to itself and disallowing charging at temperatures below 5 deg C).

To give you some idea of the "new thinking" required with these batteries compared to Lead Acid when I took delivery of my batteries it was going to be several weeks before I could install them.  New batteries are delivered at about a 50% SOC.  When I asked my dealer how long I could leave them "as is" and what I needed to do to maintain them he said I could leave them that way for many months and probably years, and that I didn't need to do anything other than store them at a reasonable temperature.  Can you imagine what would happen to your Lead Acid batteries if they were left at 50% SOC for months?


--
Mark McGovern
SM #440 Cara
Deale, MD USA


locked Re: Batteries starting to get weak - MMM - What to do -

Arno Luijten
 

Mark, Scott,

Thanks for the links and additional information.  Very interesting and helpful.

My point with using voltage to determine SOC is that the whole system on a boat in “action” is not stable. Your fridges turn on and off all the time. There is a cloud in front of your solar panel, a windgust for your windgenerator, you run a sheet winch, etc etc. So the voltage varies quite a bit because of fluctuating current draw and we just determined the voltage curve on Lithium is quite flat. How is your BMS to determine the SOC? This is why you really need a coulomb counter and some way to make it control your charging sources. Mastervolt has this mastershunt thing and some other stuff to make that happen but it quickly becomes very complex and maybe too complex for a bue water boat. I don’t know.
Anyway, for my usecase I think (as Scott rightfully says) it is not worth the trouble. I’m first going to try Firefly carbon foam batteries and in a few years we will see what the next best is. For those who spend most of the time off-grid lithium is much more attractive.

Regards,

Arno
SV Luna,
A54-121


Re: Gearbox ratio

Mark Barter
 

Thanks Mark, by complete chance I managed to capture that plate on our gearbox in a video I made. Now that I know what I am looking at I have the answer to my question. For anyone who needs to know the ratios are A: 2.74      B: 2.72
--
Mark & Nicky Barter
S/V Nunky
SM 110


Re: Ankerwinde Amel euros

Elja Röllinghoff Balu SM 222
 

Hallo Valentin
Ja die Winde scheint es zu sein , ich würde aber immer eine nehmen mit einem Verholspil
( einer Rolle an der Seite ) das erleichtert manchmal die Arbeit mit der Mooring .
Bei uns war ein Loch zum Kettenkasten ca 40 mm dadurch fiel die Kette direkt in den Kasten .
Das einzige Problem der Kasten ist nicht sehr tief und dadurch läuft die Kette dan auf und verstopft das Loch , dann must du die Kette mit der Hand wegräumen. Das kannst du aber mit einem ball fixiertan der richtigen Stelle umgehen , dann fällt fie Kette auf den Ball 🏀 unf verteilt sich besser .
Achte bitte darauf unsere Euros war eine Euros 39 !
Ich weiss nicht ob die Masse auf dem Vordeck etwas anders sind ,


Wenn du noch etwas brauchst jederzeit gern
Grüße Elja
SM Balu

Von meinem iPhone gesendet


locked Re: Batteries starting to get weak - MMM - What to do -

Mark McGovern
 
Edited

Scott,

Thanks for taking the time to reply.  I have read your posts with great interest and they have definitely helped me in planning and implementing my own system which shares many of the same components that you chose (i.e. I have lots of blue Victron stuff in my SM!).  

To be clear, I'm not saying that what the owner of MV Tanglewood is doing is the "correct" way to do it.  It certainly is not what most LiFePO4 manufacturers recommend.  I was simply stating that there does appear to be an observable and actionable correlation between voltage and State of Charge (SOC) with LiFePO4 batteries.  I totally agree that there is not a lot of "resolution" in the middle of the curve but there is enough resolution at the tail ends of the curve to take action before damage is done on either end of the curve.

Regarding the data posted that is posted here: https://www.powerstream.com/lithium-phosphate-charge-voltage.htm  you can see from the description of the test above the data that the test was done using very small batteries (less than 2.5 Ah capacity) and was done at over a 1C discharge rate (2.5 Amp discharge on 2.2 to 2.4 Ah batteries).  That is an extremely high discharge rate that is not really indicative of how we generally use our battery banks on our boats.  My normal "sitting at anchor" discharge rate is closer to 0.01C and I can even run one of the Air Conditioner units on the boat and still stay under 0.1C.  I think this high discharge rate has a significant impact on the Voltage vs. SOC results.

The data posted at the bottom of this article is from a test that I believe is much more indicative of how we use our battery banks:  https://marinehowto.com/lifepo4-batteries-on-boats/ and even this test is done at a relatively high discharge rate of about 0.075C.  Here is the chart of Voltage vs. Ah Discharged on the  772nd(!) Cycle on his ~11 year old LiFePO4 battery bank: https://marinehowto.com/wp-content/uploads/2015/09/34-LiFePO4-On-Boats.png


  


It's impossible to read the chart above but you can see the details in the links I that posted above.  I took the data from this 0.075C discharge test to get the following approximate Voltage vs. State of Charge %:

At 3.15v per cell or (3.15*4/8 = 12.6v/25.2v) you are at around ~15-18% SOC.
At 3.2v per cell or (3.2*4/8 = 12.8v/25.6v) you are at around ~30% SOC
At 3.3v per cell or (3.3*4/8 = 13.2v/26.4v) you are at around ~95% SOC
At 3.4v per cell or (3.4*4/8= 13.6v/27.2v) you are at around ~99-100% SOC

So on our nominal 24v boats there is a 1.2v difference from ~95%SOC to 15-18% SOC (26.4v-25.2v=1.2v).  That's not a huge difference, but it is easy to observe and use in decision making.

Other things to note in those test results:

  • He charges the bank to only 13.8v (3.45v per cell) with a 7.5amp tail current.  That's 27.6v on our 24v boat and is well below what most LiFePO4 battery manufacturers recommend. 
  • The battery bank reaches only 13.5v (3.37v per cell) at the start of the test with those charging parameters.
  • The voltage drops from 13.5v to 13.26v (3.32v per cell) after discharging only 6 Ah.
  • This data is from an eleven year old battery bank of LiFePO4 cells that has been in use in the lab and on a sailboat for and has had 773 cycles.  Most of those cycles have been to 80% depth of discharge or more.
  • This bank was rated at 400Ah when it was new but eleven years and almost 800 deep cycles later it still has MORE capacity than it was rated for when it was new.
Based on all of the above, Tanglewood's seemingly relatively simplistic scheme of charging to 3.45v per cell (but apparently only reaching 3.35v per cell or 26.8v on a 24v system), discharging normally, then charging again when the battery bank reaches 3.15v per cell (25.2v for Amels) seems pretty reasonable as it would cycle his batteries from 95% SOC to 15=18% SOC.  Only time will tell!  Hopefully he will continue to post his findings, good or bad. 

--
Mark McGovern
SM #440 Cara
Deale, MD USA


locked Re: Batteries starting to get weak - MMM - What to do -

Scott SV Tengah
 

Mark,

I looked at his first post and a few things he stated that is not consistent with the known characteristics of lithium:

1) Take a look at the voltage vs. SOC graph for a Lifepo4 battery. 
https://www.powerstream.com/lithium-phosphate-charge-voltage.htm

At 3.2v per cell or (3.2*8 = 25.8v) you are at around 3-8% state of charge.
At 3.3v per cell or (3.3*8 = 26.4v) you are at around 20-31% state of charge.
At 3.4v per cell or (3.4*8= 27.2v) you are at around 96-99% SOC. 

But it's not just the spread, it's the shape of the curve. The challenge is that the lithium curve, unlike lead, is NOT linear. The middle portion between say 10% and 90% has a very flat voltage curve.  See link above. I can attest that with my Mastervolt 110A charger set to 27.5v absorption, the alternator has stopped charging anywhere between 75-100%, averaging 85%.

If you set your charger to stop charging at 26.8v, you may be charging your batteries to only 40-50%.

And as you can see with lead, the voltage vs. SOC curve is quite linear, making it far more useful to determine SOC from voltage.
https://www.researchgate.net/profile/Jeff_Cherry2/publication/315847359/figure/fig2/AS:633864561106948@1528136496496/Typical-Open-Circuit-Voltage-OCV-of-12V-Lead-Acid-Battery.png

2) He stops charging at 3.45v per cell and has a high voltage alarm at 3.5v. His high voltage ALARM is below Victron's absorption voltage of 3.55v and below Mastervolt's absorption voltage of 3.6v. Keeping voltage low like that will help avoid high SOC induced imbalances but there are other sources of imbalance too, namely high load or imperfectly assembled batteries. And most cell balancing systems require you to charge to near full before they start balancing, as indicated by low charge current acceptance rate - namely because of the non-linear charge curve. I have had batteries that show perfect balance until you approach 3.5v+ and then one cell goes wildly out of balance.

By not charging your batteries fully every once in a while, you may end up prolonging a cell imbalance issue that, in the event that you need to draw the batteries quite deeply (big storm, can't run the genset because of sea state), could result in a cell LOW voltage problem that will destroy the battery or cause your BMS to disconnect your loads at the worst time. Further, most battery monitors determine state of charge based on calibrating to 100%. And 100% on my battery monitor is determined when charge current is below X for time period Y. That means the battery is full and no longer accepting charge. As such, Victron explicitly recommends charging fully once a month to recalibrate the SOC monitor.



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


locked Re: Batteries starting to get weak - MMM - What to do -

Mark McGovern
 

Arno,

Voltage may not be as bad an indicator of SOC of LiFePO4 batteries as you might think.  Here's a quote from the owner of MV Tanglewood who has had his LiFePO4 bank in operation for about ~18 months now:

First, counter to what everyone says, I think battery bank voltage is a sufficiently close indicator of SOG.  People say it's a much worse indicator for LFP vs Lead, but I disagree.  My lead bank was 50.4 volts when fully charged, and 48.0V when is was 50% empty and the generator started.  That's a spread of 2.4 volts.  In contrast, my LPF bank is full at 53.6V, and ready for recharge at 50.4V.  That's a 3.2V spread and is 30% more voltage swing than lead.  The difference, though, is that in the mid area of charge, the LFP voltage doesn't vary much, so there isn't as much differentiation between 60% and 50%.

Granted, this 3.2v spread is for his nominal 48v system but even with our nominal 24v system it would be a 1.6v spread which is a significant enough spread to monitor and act on.  I am literally in the middle of installing my LiFePO4 system and I am not yet living full time on the boat so I don't have a ton of personal experience with it just yet.  However, the experience that I do have so far lines up with Tanglewood's experience.  I think that if you operated an LiFePO4 system simplistically such that it is assumed to be "full" at 26.8V (stop charging) and then "empty" at 25.2v (start charging), the battery bank would be quite happy and would give you many years of service.

Here is the full blog post:  http://www.mvtanglewood.com/search/label/Lithium%20Batteries  

Be sure to read his other LiFePO4 related posts.  They are full of great information.
 
--
Mark McGovern
SM #440 Cara
Deale, MD USA

4261 - 4280 of 58456