Understanding Lead-Acid Battery Life

[tanglewood]

Originally Posted by rgleason

I don't know what to believe at this point.

I get the impression a lot of these comments are coming from users in relatively warm climates all year round.

Some of these elegant and highly technical lithium installations which look so beautiful, are not intended to be removed every fall. In fact they are relatively permanent installations. If these batteries are left in place over winter where it can get down to -10F + wind chill, what can be done if no shore power lines are allowed to the boats by the yard?

I suppose they are left at 50%SoC and then they have to be checked every week (not possible). I am not at all sure this is a practical situation.

If it's not a practical solution for you, then don't do it. But that doesn't mean is bad for everyone.


The cells all have operating and storage temp ranges, so you need to operate in those ranges. For CALB, it's 0 to 45C. I've tracked the laz temp in our boat, and others like it to get comfortable that we can reliably stay in that range. The boat never gets laid up, but can definitely stay idle for months. I'm real confident we will be within that range, actually well within it. The only risk is a heat failure in very cold weather, and I'll have to be ready to deal with that. So for our boat it works.



That said, if you are talking about a boat that gets laid up in the winter or the summer in extreme conditions, LFP may not be the right choice. At a minimum I think you would need to plan on removing the cells for storage, and that needs to factor into your decision.


Remember, water is useful to have on a boat, and worth it even though you need to empty it and blow out the pipes for storage every winter.

[rgleason]

Excuse me. Thats a little better. Are these portables able to be added to the electrical system and be charged with low & high v protection without much manual intervention? How would you use them to charge LA "long tail"?

Can they be oriented in any way? I do not have enough height for them.

[rgleason]

Tanglewood
I can deal with domestic h20 system blowout & removal of batteries, I do now, in RI winters.
What I realize is that if I remove the lithium batteries they have to be reconnected and the BMS moved and appropriate charging added, all set up in my basement. This requires some consideration, so perhaps your portable pack might be a good solution, if it can be configured appropriately.

[rgleason]

I must have been looking at a different battery. 8.7" high will fit. There is a 3% discharge per 30 days. So they could be left for several months, then checked.

[tanglewood]

Originally Posted by rgleason

Tanglewood
I can deal with domestic h20 system blowout & removal of batteries, I do now, in RI winters.
What I realize is that if I remove the lithium batteries they have to be reconnected and the BMS moved and appropriate charging added, all set up in my basement. This requires some consideration, so perhaps your portable pack might be a good solution, if it can be configured appropriately.

Good question re storage. It all comes down to the self discharge rate of the batteries when stored, and I gather it's a lot less than LA. It's not something I've paid a lot of attention to since I haven't been faced with storage. Perhaps some people here can offer up some experience. And I'm sure there are research papers studying it. But I wouldn't be surprised if you could store at 60% and be fine through the winter with them at room temp. No matter what I'd monitor them the first time. And storing without BMS will be no load vs a small load with BMS. So I think better without.

[tanglewood]

Originally Posted by rgleason

Excuse me. Thats a little better. Are these portables able to be added to the electrical system and be charged with low & high v protection without much manual intervention? How would you use them to charge LA "long tail"?

Can they be oriented in any way? I do not have enough height for them.

It's worth reading the thread on Drop in LFP. Best case, drop in is sub optimal battery and power management.


As for using LFP to do the finish charge on LA, it just doesn't make sense to me. Just use the LFP. But that goes back to the Hybrid LA/LFP thread.

[tanglewood]

Originally Posted by rgleason

I must have been looking at a different battery. 8.7" high will fit. There is a 3% discharge per 30 days. So they could be left for several months, then checked.

Oh, and you had asked about orientation. I don't know about Winston and others, but CALB wants them upright.

[mbartosch]

Regarding storage: we disconnect (almost) all loads and leave the bank at 50-60% SoC for the winter.
Remaining loads on the bank are the House Power BMS cell modules (~ 0.5 mA) and the BMV 700 (4 mA), which would be roughly 45 Ah (or about 10 % SoC on our bank) a year. Not a problem for our use case.

Regarding orientation: the Winston cells shall be operated „upwards“ or „lying on the shorter side“. They shall not be used lying on the wide side. Storage orientation (no charge/discharge) is arbitrary, however.

[john61ct]

Originally Posted by rgleason

https://www.electriccarpartscompany....fied-Batteries Nice idea well executed but 4 x $260 = $1040 plus the case and all the fixins.
Not cheap for 100ah

Quality LFP is not going to be cheap, never claimed that, I've always said LFP is 5-7x pricier than lead even taking usable AH into account.

Please don't call me deceptive just because reality does not meet your expectations.

But that **is** pretty high even for NA market, may me worth self importing. And larger cells are a bit cheaper per AH.

If you need lighter go lower capacity, couldn't do it at all with lead.

> Not a real choice for most people

Do you just mean the cost issue or something else?

[a64pilot]

Self discharge rate is way slow, you can leave them at 50% SOC and months later it’s still going to be very close to 50% SOC

[john61ct]

Originally Posted by rgleason

I don't know what to believe at this point.

I have not seen any conflict on this between credible posters, and in fact posted direct links to cell mfg specs in the other thread.

If you ask specific Qs in a new thread I'm sure the truth will be clear.

> users in relatively warm climates all year round

That where most cruisers live.

> are not intended to be removed every fall

Because those owners don't need to. Unlike lead that is a pretty easy design requirement to fulfill with LFP.

If spending the premium is worth it to you for other reasons.

> If these batteries are left in place over winter where it can get down to -10F + wind chill, what can be done if no shore power lines are allowed to the boats by the yard?

There is no problem storing at that temp, just make sure the cells are isolated and if possible below 50%.

> they have to be checked every week

No need to check them that frequently. In fact if fully isolated, all winter is OK if you **know** the self-discharge rate (empirically) and maybe go to 60-70% if necessary.

Of course if none of these factors fit your preferences then simple, don't use LFP, just not a good fit **for you**.

[john61ct]

Originally Posted by rgleason

Are these portables able to be added to the electrical system?

LFP DIY is pretty much pioneer territory.

Unless you pay a systems integrator, most of those Qs you'd need to figure out for yourself, maybe experiment and report results back here.

When you say "these portables" what do you mean?

Each person builds their own setup to meet their own needs.

> How would you use them to charge LA "long tail"?

Again, that's just a very speculative and controversial thought experiment, waiting for a brave pioneer to prototype and report test results.

> Can they be oriented in any way? I do not have enough height for them.

See below.

But the compression plates / straps would need to be designed for your physical layout.

[john61ct]

Originally Posted by rgleason

if I remove the lithium batteries they have to be reconnected and the BMS moved and appropriate charging added, all set up in my basement.

No, just sit isolated, check V with a DMM once in a while.

Many people manually act as BMS even in daily cycling, certainly no worries going bareback for storage.

[john61ct]

Originally Posted by rgleason

I must have been looking at a different battery. 8.7" high will fit. There is a 3% discharge per 30 days. So they could be left for several months, then checked.

Test yourself for your situation.

Varies **a lot**, not least with temperature.

[john61ct]

Originally Posted by tanglewood

storing without BMS will be no load vs a small load with BMS. So I think better without.

Correct