Gel Battery Left Uncharged

[fooby]

I've recently discovered that my van has a 120Ah Lucas gel leisure battery installed along with a voltage sensing relay, I'd imagine this was installed for a rear light along with a trailer module that was connected to the leisure battery.

The fuse from the starter battery to the relay was blown, after replacement everything works and the leisure battery is charging. I'd imagine that it hasn't been charged since being a work van 3 years ago and was only reading 5.5v previously.

It's now showing 12.1v after charging. How do these gel batteries hold up to being stored in a discharged state for long periods of time? I'm doing a camper conversion and it would save a considerable amount of money if I could use it.

[electronpusher]

1. Being a "12v" lead acid discharged to 5.5v, yes it is probably dead.
2. Being a leisure battery, possibly it's not completely dead? Might be more tolerant than a starter.
3. Only sure way to know is measure it.

So maybe like

1. charge it until you think it's charged
2. let the charge relay drop out
3. put a 12v bulb across it... headlamp? whatever, depends how long you want to wait
4. calculate how long it's going to take that bulb to discharge the battery at its nominal capacity.
5. * 120Ah battery, 5A bulb => 24h
6. * Maybe you want to draw more current? Do you have some more bulbs?
7. measure the voltage often enough that you don't feel like repeating the experiment when you didn't get good data

When to stop... if it goes the distance, it's still good so don't take it below... not sure, 11v?

If it doesn't go the distance, it's scrap anyway.