Understanding Lead-Acid Battery Life

[Dockhead]

We recently discussed the failure modes of lead-acid batteries in a tremendously popular, but unfortunately acrimonious thread. Despite the minority of participants who disrupted the tone of the thread, however, I think many of us learned a lot from discussing how sulphation works and how lead-acid batteries die.


I continue reading and thinking about these issues, and recently learned that there is an actual test regime which seems to be quite representative of how some of us use our batteries -- IEC 61427 -- which contains a great deal of PSOC cycling, just like what we do.


This makes really interesting reading: https://www.trojanbattery.com/pdf/RE...7_Standard.pdf


and from this:


https://www.trojanbattery.com/pdf/RE...27_Premium.pdf


I find it quite believable that these heavy duty L16 batteries will really last more than 1000 cycles in realistic off-grid cruising.



It's the first time I've seen a cycle life rating which I thought could be applied to what we do. I know that my own Trojan batteries (27TMX) are rated for 600 cycles @ 50% DOD, but in my usage, which includes PSOC cycling, they don't give even half of that.

[john61ct]

Originally Posted by Dockhead

representative of how some of us use our batteries -- IEC 61427 -- which contains a great deal of PSOC cycling, just like what we do.

Hmm.

Is that the royal we?

I agree many (most) off-grid cruisers fail to frequently enough get to 100% Full.

But many can and do once they learn how, starting with getting an ammeter so they can measure objectively.

To me that approach is the first to take, chronic PSOC abuse is only unavoidable for IMO a small percentage of owners' setups.

With the right gear and protocols in place, even if the bank is perfectly coddled, spending more per AH to get greater longevity is then easier to justify.

But when the care is sub par, best IMO to stick with good-but-basic level of quality like T-105.

In that context I doubt buying higher quality is economic, unless traveling to primitive locations where replacement choices are poor value.

[Dockhead]

Originally Posted by john61ct

Hmm.

Is that the royal we?

I agree many (most) off-grid cruisers fail to frequently enough get to 100% Full.

But many can and do once they learn how, starting with getting an ammeter so they can measure objectively.

To me that approach is the first to take, chronic PSOC abuse is only unavoidable for IMO a small percentage of owners' setups.

With the right gear and protocols in place, even if the bank is perfectly coddled, spending more per AH to get greater longevity is then easier to justify.

But when the care is sub par, best IMO to stick with good-but-basic level of quality like T-105.

In that context I doubt buying higher quality is economic, unless traveling to primitive locations where replacement choices are poor value.

If you have a large solar bank and use it right (charge up the batts with something else in the morning enough that the solar then gets a real finishing charge on it; have proper charging regime; etc.), then you don't care how well the batts stand up to this, and you don't need especially good batteries.


If you're not off grid very often, like the great majority of sailors, then you don't care.


But a lot of us simply don't have any way to put a finishing charge on every day, and even struggle to do it once a week sometimes. So that is the subset of people who really care about this.


T-105s (or equivalent cheap golf cart batts) are kind of the standard solution to this, but are they optimal? You need this kind of a test to know.

[john61ct]

Originally Posted by Dockhead

If you're not off grid very often, like the great majority of sailors, then you don't care.

Yes no need for the more-robust systems, I am always oriented toward living full-time off-grid, get to shore power maybe couple nights a month.

> If you have a large solar bank and use it right (charge up the batts with something else in the morning enough that the solar then gets a real finishing charge on it; have proper charging regime; etc.), then you don't care how well the batts stand up to this, and you don't need especially good batteries.

See my feeling is spending more on top-notch **lead** batteries is only worth it when you have the infrastructure in place to care for them properly.

Even the best lead like Rolls Surrette - **much** better than any Trojan IMO - will fail pretty quickly if they are abused, and then you won't get the extra value out of them.

So if the bank really needs replacing say every other year, best to stick with as close to $1/AH as possible, long as they are true deep cycling.

I'm not saying rigorous testing might not prove me wrong, if you have the resources to get that done, please post your results!


Now, if PSOC specifically is the only problem, then maybe Firefly's the way to go.

Or the whole issue goes away completely with LFP.

[Dockhead]

Originally Posted by john61ct

. . Even the best lead like Rolls Surrette - **much** better than any Trojan IMO - will fail pretty quickly if they are abused, and then you won't get the extra value out of them.

So if the bank really needs replacing say every other year, best to stick with as close to $1/AH as possible, long as they are true deep cycling.

I'm not saying rigorous testing might not prove me wrong, if you have the resources to get that done, please post your results!
.

I'm not sure the underlined passage is true -- if you read the Trojan report, they are getting more than 1000 cycles out of their industrial L-16 batteries with heavy PSOC cycling, according to that test regime.


That is bloody good.



"Abuse" is a loaded term. If PSOC cycling is not reasonably avoidable on your boat, then it's a "use case", not "abuse"


Trojan make a number of different L-16 batteries, but they don't seem to cost much, if any more per amp/hour than T-105's.



If I could find some place to put them (I don't think I ever could), they could be a great solution for my use case. 1000 cycles including a lot of PSOC cycles is entirely satisfactory -- that would be at least 8 or 9 years.



The other benefit of L-16 batts is that I could make a single bank of sufficient capacity with no paralleling. Can't do that with T-105's. Paralleling lead acid batteries, especially with a large physical separation like I have, sucks. Huge reduction of useful life because of the unavoidable imbalance (by the way, bit of thread drift, but lead-acid batteries would surely benefit enormously from having proper BMS's themselves).

Originally Posted by john61ct

Or the whole issue goes away completely with LFP.

Indeed!

[Kenomac]

Lots of threads about the same issue. Why don’t you buy a couple of deck mounted solar panels from Solbian.... problem solved.

[tanglewood]

I had Trojan L16s in an off-grid system set up as a 19kwh bank. They were the 6V variant, but the 2V version in the paper just have the three cells wired in parallel rather than series, so essentially the same battery.


Anyway, they lasted about 5 years, which is around 1500 cycles. That's right what their figures suggested. They cycle every day, and can go for days without a full recharge. Cost was about $168 per kwh of capacity



I am now on the last legs of a very large Surrette bank set up as a 64kwh bank. They cost was $225 per kwh of capacity, so 30% more per kwh. They have lasted 10 years, which is also as predicted.


- The Surrettes lasted twice as long, but cost 4x what the Trojans cost. Next time I'll buy Trojans.


- The Surrettes lasted 10 years, but I had to replace two cells along the way at nearly the cost of new. One I paid full new price, and the other about 80% of new because of shipping. So much for a 10 year warranty. It was useless and a massive runaround from Surrette. And the replacements took 4 months to get, both times. I had to reprogram and run the system at 44V rather than 48V while I waited for replacements.



Overall the Surrettes were a massive, costly mistake. I believed "common knowledge" that they were superior, but in my experience they totally suck in pretty much every way.


I also see very little benefit from shallow cycling the big battery bank vs deeper cycling the smaller bank. In fact I think the economics of the smaller Trojan bank, including deeper cycling was significantly better than the larger bank.

[boat driver]

Originally Posted by john61ct

Yes no need for the more-robust systems, I am always oriented toward living full-time off-grid, get to shore power maybe couple nights a month.

> If you have a large solar bank and use it right (charge up the batts with something else in the morning enough that the solar then gets a real finishing charge on it; have proper charging regime; etc.), then you don't care how well the batts stand up to this, and you don't need especially good batteries.

See my feeling is spending more on top-notch **lead** batteries is only worth it when you have the infrastructure in place to care for them properly.

Even the best lead like Rolls Surrette - **much** better than any Trojan IMO - will fail pretty quickly if they are abused, and then you won't get the extra value out of them.

So if the bank really needs replacing say every other year, best to stick with as close to $1/AH as possible, long as they are true deep cycling.

I'm not saying rigorous testing might not prove me wrong, if you have the resources to get that done, please post your results!


Now, if PSOC specifically is the only problem, then maybe Firefly's the way to go.

Or the whole issue goes away completely with LFP.

if you are replacing your bank every year then something is wrong- the bank should make it three- four years with daily use and complete charging.
and without any specific solar or grid charging consistently- charging when not quite 50% and doing a full charge via quality volt meter will suffice.
Most issues i see with lead-acid battery failure is failure to add water(monitor) , corrosion, incorrect programmed smart charger, and quite often particularly with sailors, not getting the batteries charged completely via motor- the run is timed vs voltage monitored. .

[ArmyDaveNY]

Do you think the desulfication chargers will help solve the shortened life of the batteries? I've read some good reviews on some of them, in particular the ones from PulseTech.

[a64pilot]

Originally Posted by Kenomac

Lots of threads about the same issue. Why don’t you buy a couple of deck mounted solar panels from Solbian.... problem solved.

I don’t think he could fit enough of them.
I think his answer is one of five things.
1. Continue as is with frequent replacements
2. Fit a much smaller genset and run it for 8 hours or more a day, cause even if you discharge to 50% and autostart the genset, the bank will be 100% fully charged in eight hours, as long as you have enough bank to carry you through the next 16 hours and not go below 50% SOC this works. Likely can do it with less than eight hours, but I’m sure eight would cover it.
3. Fit Firefly batteries and reduce your gen run time maybe by half
4. Fit LFP and maybe reduce gen run time by half or a little more?
5. Fuel cells, but I don’t know of any big enough and fuel may be an issue?
Eight hours of gen run time on an aggressively sailed boat ought not be too obnoxious, you could also do all of your cooking and watermaking during that time, I assume no clothes washing.
So you need a bank large enough to carry your electronics, bilge pump etc for 16 hours. Shouldn’t have to be a huge bank for that?

If your really worried about heeling, pendulum mount the thing like a stove.

On edit of course you don’t need a smaller genset, just likely just charging batteries is not really loading down what you have.

[john61ct]

Originally Posted by Dockhead

I'm not sure the underlined passage is true -- if you read the Trojan report, they are getting more than 1000 cycles out of their industrial L-16 batteries with heavy PSOC cycling, according to that test regime.

In Calder & Maine Sail's research on PSOC resistance, **none** of the other banks came even close to Firefly's PSOC resistance (imperviousness) to abusive PSOC conditions.

I believe no FLA was included.

If you (or MS or someone) were able to do similar real world testing, maybe also use that SAE? one, that would be a tremendous service to the community.

In the meantime color me skeptical.

Trojan's overblown claims wrt their AGM, have made me so.

Every mfg has a constant struggle between honest scientists / engineers and the slimeball sales & marketing types, and these days the good guys usually aren't winning.

Especially if the pricing per AH is in the same ballpark as good ol' T-105's.

[john61ct]

Originally Posted by boat driver

if you are replacing your bank every year then something is wrong- the bank should make it three- four years with daily use and complete charging.

Nothing to do with me.

If you follow the context, I was addressing another member's scenario where PSOC abuse seems to be unavoidable.

No idea just how bad, gave the 1-year example as a worst case extreme, specifically arguing for cheap $/AH in that context.

[john61ct]

Originally Posted by ArmyDaveNY

Do you think the desulfication chargers will help solve the shortened life of the batteries? I've read some good reviews on some of them, in particular the ones from PulseTech.

No complete snake oil, sorry.

[a64pilot]

Dock,
I think your issue is you’ll run your generator for four hours a couple of times a day, as opposed to one long run. Two four hour runs and one eight hour run are of course the same run time in a 24 hour period, just the two four hour ones won’t fully charge you, they add partial cycles though, twice as fast.
You need I think to adopt an attitude that if I’m starting this thing, it’s running until my bank is topped off

[a64pilot]

Totally different thing of course, but I’ve know people who will crank the Honda and go into town, when they return, their bank is topped off.
Most of course will run it a couple of hours before they go to bed, and that is partial cycling them of course.