What count as a cycle (battery life)

[sstuller]

Re Sterling Power video the Walmart Everstart batteries have the same test results. AS an example The 27DC $75 battery has an RRC (repetitive reserve capacity) of 65 cycles to 10.5 volts which results in reducing the capacity to 50% of a new battery. This is about the same as the AGM in the video. Maybe the Everstart batteries deserve more respect. Thanks.

[john61ct]

Battery capacity is one thing, and easily tested.

Battery **longevity** under deep cycling conditions is a completely different matter.

Many people use inexpensive batts for a few years light usage and then replace, no shame in that.

But a large expensive bank you want to last for 5-8 even 10+ years daily use takes products designed for the purpose, and it takes well over a decade for enough user reports to accumulate before the community can make a solid judgment.

That brand you're referring to, do you know who actually makes them?

[gauvins]

Originally Posted by john61ct

Battery capacity is one thing, and easily tested.

Battery **longevity** under deep cycling conditions is a completely different matter

Very good point. I was in the "buy inexpensive" group and didn't have the tools (or knowledge) to justify investing in a alternatives.

To me, the tricky thing is that "inexpensive" depends on your circumstances. Looks like lithium might be cheaper than FLA because they can manage a much higher number of discharge cycles. But the initial cost is much higher. So if you don't know what you are doing, FLA end up being a better option.

My plan is to see if I can get the number of Amps claimed by a manufacturer (capacity x number of cycles). If I do, I'll very probably go lithium on my next bank.

[john61ct]

LFP costs 5-7 times even quality lead, and is very easy to murder.

But yes over a thirty year timeline if nothing goes wrong LFP works out cheapest. In theory.

ROI that long and up-front investment that high, is very risky.

[sstuller]

Optima batteries advertise a 350 cycle life for testing similar to the Sterling cycle with a remaining capacity of 50 % of the battery when new. Thanks.

[john61ct]

That's not a good batt for deep cycling since Enersys spun them off to JCI.

Great Starter batts though.

[sailinglegend]

Originally Posted by john61ct

Battery capacity is one thing, and easily tested.

Battery **longevity** under deep cycling conditions is a completely different matter....

Wow - how do you test battery capacity then?

In 14 years as a live aboard I have never seen anyone do it properly - that's discharge at the battery design current - the C20 rate - until the battery falls to 10.5v. If it takes 20 hours then the capacity is 100%, if it only takes 10 hours the capacity is about 50%.

Keeping this discharge current 'constant' as the battery voltage falls is very difficult as more loads need to be switched on and an accurate current measuring device needs to be used. Lights can add to the load but often LEDs take so little current that you may soon run out of the right loads. A constant load tester is needed to make this practical.

[john61ct]

Search for 20 hour capacity test here https://marinehowto.com/programming-a-battery-monitor/

Any constant-variable controlled load, can run through an inverter if needed.

Timed snapshots of the meter from a cheap phone so you don't need to sit and watch the whole time.

If running regular benchmarks, having results from a run done after the commissioning process is very useful, just ensure they're run the same way each time.

[sailinglegend]

Originally Posted by john61ct

Battery capacity is one thing, and easily tested...

Originally Posted by john61ct

Search for 20 hour capacity test here https://marinehowto.com/programming-a-battery-monitor/ .....

Of course - see MaineSail's article - been there, done that, got the T shirt, and I did it last year - and it's NOT easy.

MaineSail actually says:

'This is a tedious and imprecise process for the average DIY.'

That was my point - it is not easy - especially because:

You have to do it on each battery in turn that could take a week or more because you have to recharge - at the C20 rate - for each one before the next test.
You can't use variable loads like the fridge which keeps coming on and off - so no fridge for a week!
You need an accurate digital voltmeter and current meter.
The battery temperature must be 75F-80F through the test.
This will disrupt your sleep!!!!!

AND if you do the test at the C20 rate of say 5 amps for a 100 Ah battery and the test says it's at 70% then for accuracy you should really do the test again because it will be showing lower than it really is at about a 75% capacity. (Peukert effect) So It's best at the start to assume you battery is at about 80% capacity and use a C20 rate of 4 amps and see the difference. At 80% FLA batteries should be replace - Lifeline say theirs can go down to 50% of their original capacity.

[a64pilot]

I have never cap tested my bank. I have done many aircraft batteries as part of the aircrafts annual inspection cause it’s a required inspection, that is almost never done. I use a landing light, it’s close enough. It can tell me if a battery has enough reserve capacity to get an aircraft on the ground in the event of a charging system failure, and that is the point of the inspection.
However I maintain that with my battery monitor along with my Smart Gauge, I can get a close enough estimate of bank capacity. Based on that it seems that my four year old 660 AH bank is actually about 600 amps. This is further evidenced by if I program the bank size of 600 amps in my battery monitor, it tracks very closely with the Smart Gauge, they do disagree at times, but the first thing in the morning they are nearly identical in reading.
Of course I have to reset my battery monitor often, as in once a week at least. Actually it auto resets, I have to make sure I’m really 100% SOC though.

So it would appear that there is more than one way to skin a cat, and a cap check doesn’t have to have lab quality equipment, it’s better if it does of course, but who can carry that around in their boat?

My mentor as a test pilot has several sayings, one is that perfection is the enemy of good enough. We don’t always have to drive things down to perfection, sometimes good enough, is well good enough.

[a64pilot]

The way to do a pseudo cap check with a Smart Gauge and an amp counting battery monitor is to ensure your really, fully 100% SOC. Best to be at a dock of course.
Then turn off any charge sources and use just use the boat, ideally monitor loads as to be close to the 20 hour rate, then when the Smart Gauge reads 50% SOC, look to see how many amps have been used.
Then of course immediately fully recharge the bank with biggest charge source you have, this is why it’s nice to be plugged into shore power.
It is not lab accurate of course and your testing the whole bank, not each battery. Bank temp seems to remain very stable, takes a lot to Cool or heat several hundred lbs of lead I guess, right now my bank is 82 F, but I’m in really warm weather.

[LeaseOnLife]

Originally Posted by a64pilot

The way to do a pseudo cap check with a Smart Gauge and an amp counting battery monitor is to ensure your really, fully 100% SOC. Best to be at a dock of course.
Then turn off any charge sources and use just use the boat, ideally monitor loads as to be close to the 20 hour rate, then when the Smart Gauge reads 50% SOC, look to see how many amps have been used.
Then of course immediately fully recharge the bank with biggest charge source you have, this is why it’s nice to be plugged into shore power.
It is not lab accurate of course and your testing the whole bank, not each battery. Bank temp seems to remain very stable, takes a lot to Cool or heat several hundred lbs of lead I guess, right now my bank is 82 F, but I’m in really warm weather.

I do similar tests, once in a while. I have three batteries as house bank, each ~210Ah. I can run my consumption from each one of these batteries only. Turning on some additional systems, (lights, fans, Laptop) over night, using ~10A average gives my close enough of a 20hr rate.

• I start the test in the late afternoon after I made sure all batteries are 100%SOC.
• Turning off all charging sources (solar) I run from a single battery for the next 10h, have an alarmclock wake me up, note the AH used on the battery monitor.
• I then switch the tested battery off while turning on the breakers for the two other batteries. Go back to bed.
• in the morning, after the tested battery had >= 4h hours to rest, I measure the resting voltage and compare to a SOC chart from the manufacturer.
• With this I can calculate the capacity: If resting voltage points to a 40% SOC, I used up 60% using ~100Ah. 100%/60%*100Ah => 167 Ah total available on that battery
• then charge all batteries to full again, with generator and/or solar (don't have shore power...)

good enough for me...


on edit: I have Lifeline AGMs, can't measure specific gravity. And no SmartGauge on this boat.

[john61ct]

Never said it was easy.

Just that it is the only low-tech way that is accurate.

When I get my iCharger 4010-duo for balancing LFPs, apparently it has a "regenerative discharge" feature that may work for load testing, maybe even away from a mains-powered test bench, will report back here.

[sailinglegend]

Originally Posted by a64pilot

.....However I maintain that with my battery monitor along with my Smart Gauge, I can get a close enough estimate of bank capacity. Based on that it seems that my four year old 660 AH bank is actually about 600 amps......

This is a very good way to estimate the bank capacity - you don't need to know exactly but I was 55% down on my Lifelines, and I'm still going with them this year.

If you use SmartGauge and the battery monitor you need to adjust the BM parameters so that it tracks the SG during both discharge and charge.

So you've set the Ah to 600 - about 10% down - now you need to adjust Peukerts to synchronise the discharge - this is Logarithmic so very small changes are needed, and adjust the charge efficiency to synchronise the charging. This is a great game to play all summer long!

Both Peukerts and charge efficiency change as the batteries age which is why a SmatGauge is so much better than a Battery Monitor.

[john61ct]

Whatever modified version test you use, is better than none.

As long as you do it exactly the same way every time, and also

you do it the first time shortly after the commissioning procedures are all done

(which have similar requirements anyway, and usually help boost initial AH capacity)

then you have a reference benchmark to compare to later results.

Those away from civilization for long periods, or otherwise desiring "no surprises" reliability, will then be able to proactively replace their bank in advance of any problems, in locations offering batt value and selection.

Industry standard for EoL is 80% SoH, but most non-wealthy users push to 75 or even 70%.