Choosing between batteries

[TheBeastie]

I have two batteries, neither of which were bought by me but "came" with The Beastie when I got it about 4 years ago. One is a Hoppecke 70Ah and 540 cold crank amps and the other is a UKB 65Ah and 490 cold crank amps. Originally the Hoppecke was the main battery but about 2 years ago I decided to put the UKB (which looked unused) as the main and use the Hoppecke for my radio.

Have had both batteries out today to try and squeeze in connections for a big jump lead setup I have built and took opportunity to check and give a maintenance charge to both. Fluid levels in the UKB were fine but I had to give quite a decent drink of de-ionised water to the Hoppecke.

I am planning to get an Optima deep cycle battery to run the radio and need to decide which of the two batteries is the best one to keep, and which to donate to my radio club as a starter for a "new" mobile 12.5kVa generator we have built and will set it up to trickle charge the battery when running, so condition is perhaps less vital.

Is there any way I can determine which battery is in best condition for me to keep as a starter battery for The Beastie.? I have a decent multimeter but that is all.

Any thoughts most appreciated.

[crwoody]

Ideally you could do with one of those high current discharge testers I've seen used at battery places, however you could do pretty much the same test by monitoring the battery voltage with your multimeter while cranking the engine for maybe 20 seconds or so, you may need to get someone else to turn the key! You might also need to disconnect the fuel cut-off solenoid to prevent the engine from starting while testing.

The battery that maintains the highest voltage while under heavy load would be the one to keep - so long as they are both fully charged to start with.

[snagglebag]

you could be cheeky and do as many use to at our garage and say you have had a flat battery and they will test both for free in the hope of getting a sale.

our garage had one of the new fancy ones that you just put on the battery and it digitally ran several tests to determin cell damage and other unknown hidden future probs and best of all it would give you a complete print out at the end to take away with you and digest in your own time.

this would be the best way in my opinion.

cheers gavin

[LandyLee]

if not a garage try your local battery supplier like a independent car parts seller , all of our local ones have bosch battery condition meters which as per previous post test a battery properly.

[eds]

From my experience if you have had to add a lot of water to a battery you have already done damage and it will never recover its full abilities. Sometimes it can ruin a battery adding a lot to top it up. The electrolite just becomes too weak.

Also those heavy duty battery testers really overwork the battery and I think are best avoided. I certainly would not put one over my battery.

Batteries are sensitive things that need careful constant attention if you want them to out live their expectancy.

No battery does much over 5 years unless very carefully maintained.

Battery politics is a big discussion area so don't think my answer is difinitive.

I would just get two new batteries and love them as best you can!

HTH