Battery Testers

[155V6]

I've managed to collect about 5 spare car batteries,& can't actually remember which ones are any good.I've looked on eBay,& you can get testers for a tenner or less,are these likely to be any good,or is it a case of getting what you pay for?

[sierraman]

I'd just use a multimeter, charge them up then see what happens.

[twosmoke300]

Multimeter is pretty limited . What you need is the old fashioned drop test with the two spikes and a big spark .

[DodgeRover]

Heavy discharge tester is the proper way of doing it, or put them one a vehicle and use it for a bit with the original in the boot and some jump leads.

Multimeter can tell you if a cell is gone anything less than 12v when they've been sat for a day after being fully charged and they are usually scrap, if you can open it up to top up electrolyte then adding some EDTA and slowly charging might revive it, I have a 50% success rate doing this for use in the caravan or a battery bank in the shed.

[cobblers]

The cheapo battery testers don't tell you much.

 

To test them pretty accurately with what you have lying around, Charge the batteries up full and then wire a 55w headlamp bulb up. Come back after 3 hours, the bulb should still be bright. If not, scrap it as it's got less than 15AH left.

A lot of batteries will have their capacity marked on the top, but usually a small battery will be 35AH up to 100+ for a massive one. Adjust your timings accordingly.

[DodgeRover]

As above but add a timer and low voltage cut off batteries don't really like being fully flattened

[SiC]

As above but add a timer and low voltage cut off batteries don't really like being fully flattened

55w bulb at 12v draws 4.5a ish. If it can't draw that for 2-3hrs (9ah to 13.5ah), then the battery is pretty knackered and worthy as scrap anyway...or as a spare to throw in before flogging chod on.

 

Just don't forget to check it in 2hrs or so and leave it running!

[Des]

There are tiny little LCD battery testers available for about £30, you dial in the capacity and they take about 10 seconds to tell you what % is left using sorcery, I've found one to make sense, but still value the second opinion of a drop tester or wanging over on the starter with the coil lead off and a voltmeter telling tales.

[PiperCub]

Got a cheap Bergen drop tester, about £20 on Amazon - actually been pretty accurate in my experience. But the bulb test/drain method detailed above it a neat zero-cost alternative. 

 

A multimeter is virtually useless as by definition it puts very little load on a circuit when testing voltage, my neighbours u/s battery showed a fairly healthy 12.45V across the terminals but was utterly knackered - loading it up even a bit dropped the voltage to around 7V. 

[155V6]

Thanks for the replies,I'll try the bulb method as I can do that tomorrow.I might invest in a drop tester though,pretty cheap as said.

[Eddie Honda]

http://autoshite.com/topic/26460-shite-battery-chargers-the-bradex-thread/?p=1110053

[PiperCub]

^^ Now that's a battery tester to be proud of!!! 

[cros]

Just try and start one of these 2 cylinder jobbies, if theres smoke it's a good 'un.

 

[AMC Rebel]

..or as a spare to throw in before flogging chod on.

 

 

I wondered why I always seemed to need a new batt on recently acquired vehicles