Orphaned (expensive) batteries - options?

NicaSol · September 2018

I had a 3 string 24 volt battery bank (4 Trojan L16H-AC batteries per string). The batteries are a bit less than 2 years old.

A recent maintenance check revealed that one battery in one string was dead (volts=4.1; SGs=0.000, 1.110, 1.225). Fortunately, I have several 12 volt circuits, and panels and a controller left over from an old 12 volt system, that would make use of two of the batteries.

That leaves 1 orphaned battery that is still in very good shape. I would hate to see it just sit and waste away. Are there any options for maintaining it? Can it (and whatever may be the odd battery out) be cycled in the 12 volt system (or the 24 volt system)? Is there a 6 volt charger, or other charge maintenance option, that can maintain a 435 AH battery? I haven't found anything yet but then I may not be searching correctly. Any thoughts greatly appreciated. Thanks.

Estragon · September 2018

My cheap-ish automotive type charger has a switch for 6v or 12v. I wouldn't leave a battery sitting on it long term, but it would work okay for a monthly top up charge to offset self-discharge.

Swapping in and out sounds like a PITA to me, but I suppose it could be done.

No hope for a warranty claim to replace the failed battery?

NicaSol · September 2018

Could try to find an automotive charger with a 6v switch. Just never seen one before. The vendor was willing to replace the battery however there were no L16H-ACs to be found (that's Nicaragua). And there is the new/old mix thing. Given the age of the batteries both the vendor and Trojan were iffy about mixing in a new battery anyway. Both were adamant about not using a new generic L16H-AC such as from US Battery.

In the absence of an separate charging source, I'm less concerned about the mechanics of swapping in and out than the effects of different states of charge - hopefully kept to a minimum - between the battery going in and the remaining battery in the bank for the 12v system, or the other 3 batteries in one string of the 24 volt system (and any cascading effects on the sting of 4 connected in parallel),

cow_rancher · September 2018

NicaSol said:

Could try to find an automotive charger with a 6v switch. Just never seen one before.

Schumacher makes and has made for many years 6/12 volt chargers, they even make a 6/12 volt battery maintainer.

https://www.batterychargers.com/en/products/battery-chargers/fr01333-15a-6v12v-fully-automatic-battery-maintainer

Rancher

NicaSol · September 2018

Thanks for the thoughts about 6/12 volt chargers/maintainers. Are the 1-2 amps output of most models sufficient to maintain (trickle charge?), or recharge, a 435 Ah battery. I doubt, though, that a "recharge" of any great amount would ever be necessary. If I am to cycle the batteries (unless others in the forum nix that), I would most likely cycle the battery going out after being fully charged (even equalized). The device would most likely just have to maintain the battery in a good state of charge. Various models have claims of being able to recharge batteries up to a maximum of 100-120 AH (in addition to maintaining them). But, would even trickle charging a 435AH battery be beyond their capability, being ineffective or even over heating and failing?

Vic · September 2018

Hi NicaSol,

IMO the self-discharge rate of a 435-ish Ah battery would most probably exceed the capability of most Battery Tenders. Do not use them, but have not seen a tender that would manage a 6V battery.

If you did have an automotive 12V battery charger, you could place a power resistor in series with one of the output leads to keep the charge current limited. Such a resistor may be hard to find, with the appropriate resistance and power rating.

You might try an auto headlamp in series with the output of a 12V automotive charger, and measure the current to see if it is appropriate for the charger that you are using.

If you are planning to trying to tend this battery manually, you will need a multimeter (DMM), and some ammeter. A Clamp on DC ammeter should be fine for this task.

If you do not use an ammeter, you could use your DMM, measure the voltage drop across a resistor of a known value, to determine the current -- I=E/R. A headlamp would not have this a known R ...

R=Resistance, E=Voltage, and I=Current.

Good luck, Vic

Estragon · September 2018

It seems to me my cheap-ish charger is ~10-15a. In heat, self discharge would be higher, but a couple of hours every few weeks would likely offset it. A 1a maintainer might have to be on pretty much daily.

jonr · September 2018

Say a 435 Ah battery self discharges at 10% (5% is reported as typical) per month. That's .6A to keep it charged.

Orphaned (expensive) batteries - options?

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