Lead Acid puzzle

John :-#)#

I didn't find much on premature failure there. I did here:

The only issue I'm seeing there is uncontrolled temperatures which may have resulted in the battery drying out. Charging to 15.2v has if anything worsened them, which lines up with that. I'll try adding acid & water. Thanks

I'm guessing they managed about 200 cycles of maybe 15-20% discharge average.

NT

PS I read somewhere that connecting a welder for a few seconds can break off sulphation.

NT

Battery University goes into the recommended charging voltages for batteries - your voltages are too high for lead-acid - and their business is battery chargers so it seems to make sense to follow their advice.

John :-#(#

You have a bad cell in one of the batteries, which may be reversed polarity. The charger is over-charging the other cells to bring it up to voltage.

Test a 12V battery, (13.8V appx no load) under 100 amp load and monitor during test. If full charge and good battery, the voltage will not be below 10V for ten seconds.

Thanks.

Battery abuse. The cheap charger has knackered both of your batteries.

Recharging lead acid cells for maximum longevity requires some form of thermal compensation of the voltage per cell during charging. eg

Too much over voltage and they gas. Incorrect treatment on top up and they sulphate or corrode internally either way you do damage to them. The weakest cell in a chain fails first and the others then wreck it.

Yup. Last time I looked for something suited to SLA AGM all the ones I saw used voltages suited to flooded cells.

NT

Apply a modest load to the two batteries and then measure across them.

Temperature compensation during charging is vital to maintaining the health of a battery, and they are available:

The data sheets for the better brands of the gel cell types have a graph showing expected life vs number of charge / recharge cycles. Typical design life for ups float applications can be as much as 10 years, but under regular cycling, can be

And dont forget to buy a high quality computerized charger. A cheap bad one wil sulfide the batteries in notime.

Fully charged terminal voltage is critical as well, typically 2.3 volts per cell max, but the data sheets will have voltage vs temperature curves. Overcharging increases gassing which should normally be minimal. The UPS people have years of experience of that, as opposed to consumer electronics product, where the charger often looks like an afterthought...

Chris

It's 48v, 115v and $459, no use on 3 counts. The ones nearer what I'm looking for lack temp compensation.

NT

NT

AIUI gassing is not an option for AGM. That rules out most chargers on offer. UPSes have a terrible record of battery abuse.

I might have to take the idea of making a charger seriously, I've never found one that does what's needed. Not that it's difficult, 240v 24v multistage AGM charging with temp comp.

NT

Where did I get the idea that car batteries, golf cart batteries and marine boat batteries all have fundamentally different designs? Where did I hear that golf cart batteries can be routinely discharged to about 10.5 volt, which would kill a car battery?

At least you should not head any generic advice about handling batteries, i.e. advise that doesnot address the specific battery you have.

You may assume that golf cart batteries are okay for golf carts.

Groetjes Albert

Battery mfrs & books on lead acids presumably. These ones are gone at 12.3v. Not entirely sure why.

I doubt car batteries would last long on it.