Differing battery capacity in same bank ok?

[Sulaire]

I am going to preform a capacity test on my house bank tomorrow.

Lifeline say for my 4dl’s 25 amps applied until voltage from full gets to 10.5volts is 390 minutes 100% capacity that is for one 210 Ah battery.

I have 3 in parallel, equalling 630Ah. Does this mean i still should expect the same as 1 or 3 times as long?

Should i test 1 at a time? Which would be a real PITA.

Am i over thinking this?[emoji3]

[john61ct]

A proper load test would be each unit on its own, even if they are all the same size/model and mfg date.

Maine Sail has a good generic protocol laid out in his adjusting SoC meters article.

Ideally you benchmark after the commissioning routine and breaking in period, then run it the same way when you want to compare from new.

And yes, most normal people don't bother with any of this, are willing to just buy new as needed.

[sailinglegend]

Originally Posted by Sulaire

I am going to preform a capacity test on my house bank tomorrow.

Should i test 1 at a time? Which would be a real PITA.....

One at a time so you know how each battery is performing.

Yes a PITA, but not as bad as doing three 20 hour tests!!!!!

[Sulaire]

Thanks for the inputs, much appreciated.

Whilst messing around trying to making sure the bank is up to full SOC, for the capacity test, i disabled the victron chargers “battery safe” mode that limits absorbtion time.

I let the absorption charge of 14.30v go on for an hour or two and noticed that firstly-

the amps getting put into the bank actually went up! Not down as time went on. Over that time, granted only a 5 amps rise , but still it was chucking 25amps into a bank that had been on charge through shore power for a few days! NOT GOOD. The victron battery safe mode adjusts the absorbtion time to how long the bulk was. Bulk was under 5 minutes. Therefore absoption time was only lasting around 15 mins before dropping to float before i disabled battery safe mode.

Next i noticed that 2 of the batteries were getting hot, the other was ambient temp, i stopped absorption at that point , oh dear.

I reckon its new battery time!

[john61ct]

By default OOTB 99.99% charge sources transition to Float before 100% SoC.

If possible, if you care about longevity,

AHT should be adjusted until you see endAmps is reached at Absorb, before dropping to Float,

at least most cycles, doesn't need to be every time.

And going "too long" sometimes is much better than never getting to 100%

[rgleason]

John, If you don't mind, can you explain this:

By default OOTB 99.99% charge sources transition to Float before 100% SoC.

[john61ct]

Originally Posted by john61ct

By default OOTB 99.99% charge sources transition to Float before 100% SoC

Even with super-fancy charge sources

the defaults out of the box are set too short

[Sulaire]

Well i tried again and the batteries are heating up alarmingly and no reduction in charging amps at 14.30, they still go up and the batteries get hotter!

Oh well 10 years is pretty impressive, can’t complain, if i was dodging about coastal hopping I might give them a while, but they have crossed their final ocean!

Thanks for all the inputs, in regards to my initial question, i will not mix capacities in the new bank as I cannot get a lifelines out here.

[sailinglegend]

Originally Posted by rgleason

John, If you don't mind, can you explain this:By default OOTB 99.99% charge sources transition to Float before 100% SoC

Originally Posted by john61ct

.....Even with super-fancy charge sources the defaults out of the box are set too short.....

Again I disagree!

I would say 100% of all smart chargers without end amp options drop to Float well before the batteries are 100% absolutely fully charged.

This is because chargers are designed to ‘charge’ batteries and not - or I should say ‘never’ - overcharge batteries. Getting to 100% fully charged happens in Float mode.

Please tell us about any battery or charger manufacturer who is happy with your opinion that staying at end amps whilst at absorption ‘too long’ is ok for batteries. Open flooded can be topped up with water, but I reckon many readers here have Marine Leisure batteries which are sealed and can’t be topped up. This will damage the battery more than never getting to 100%. They don’t care if these are not ‘deep cycle’ which is not what these threads are only about.

Please respond without smart phone shorthand. This is a serious Forum for people who want to gain knowledge without having to keep asking you what your posts mean.

[john61ct]

Originally Posted by sailinglegend

Again I disagree!

Feel free, it's a free world.

> I would say 100% of all smart chargers without end amp options drop to Float well before the batteries are 100% absolutely fully charged.

That is a flaw, or rather for adjustable units a misconfiguration by the owner.

Yes shunt-based is the ideal well worth spending the extra money, but all too rare.

> Getting to 100% fully charged happens in Float mode.

No Float is only for carrying loads and counteracting self-discharge when stored. For a properly adjusted charge source there is no significant further charging once it drops to Float.

100% Full is **always** defined by any quality bank maker as endAmps at the higher voltage.

> ‘too long’

is a tautology.

PSOC abuse is 100000x more of a problem out in the real world than a few extra hours at Absorb now and then.

Yes only deep cycling batteries should be used for deep cycling usage. Anyone ignoring that fundamental can ignore all these finer points, like someone frying up Hamburger Helper asking a chef about herbs and spices

Post as I like I will.

[sailinglegend]

Originally Posted by john61ct

.......PSOC abuse is 100000x more of a problem out in the real world than a few extra hours at Absorb now and then.....

All your posts suggest that you still don't understand battery chemistry because nowhere in your arguments do you use the words I keep repeating ....when the batteries are full....when the batteries are full.....

Setting a longer absorption time is fine when the batteries drop to Float way too early, but when the batteries have reached 100% full the batteries only take the current they need, but the extra energy being supplied by the absorption voltage 14.4v, or more, has to go somewhere. This causes excessive gassing and water loss and this is why all chargers drop to float before this happens to protect the batteries. This is basic battery charging law. Full batteries should not sit at absorption voltage for 'too long'. If your programming allows this to happen even for 1 hour a day for say 6 months over the winter you will come back to dry batteries. I have seen this so many times caused by solar chargers.