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Can I use a 12v load tester on 3 linked 2v batterys?

Cocksure

Well-known Member
Hi,
I have 12 2v 618ah traction batteries that i need to load test to find out which ones have failed in my solar power setup.

The cost of a 2v load tester is silly money, but 6/12v tester are quite cheap. The 6v tester applies a load of 50amps, but the 12v test applies a load of 100 amps which is a much better load test if it is possible to do?

My plan is to link 3 batteries at a time and test them 1st under 6v test, and then when i have done all 12 batteries and if not found any faults, retest under the heavier 12v load. Obviously, the scale on the load tester would be useless, but it would tell me which batches of 3 need to be tested with a volt meter on one battery at a time whilst the 3 batteries were under load.

Can anyone think/know of a reason why this wouldn't work? The 12 linked batteries are designed to deliver up to 3 kw of power, so i have no fear of the load test is too much for them, assuming my maths of 6v x 100 amps = 600watts is correct, as that's a mere 200 watts per battery? Its why i doubt the 50amp test will reveal anything as its only a 100 watts per battery.
 

Cocksure

Well-known Member
Question answered, its fine to do so. 2v load tester apply a load of 380 amps, so a 100 amp load is chicken feed
 

outoftheknow

Moderator
Question answered, its fine to do so. 2v load tester apply a load of 380 amps, so a 100 amp load is chicken feed

Don't worry about the ampere hours. 6V at 50A and 12V at 100A is the same load. 0.12 ohms. The tester is a resistive load and the current is delivered by the batteries depending on the voltage. The tester is not delivering a voltage nor current.

Put three cells in series and the load tester will show if the three cells are providing 6V (or 50A it is linear) hence they do not drop voltage when on load. If ok do the next three. If a set of three doesn't pass, remove one of the three and swap with one of a set that passed. If those three fail swap the next one. You will find the defective cells this way.
 

Cocksure

Well-known Member
Many thanks for the detailed reply @outoftheknow :)

It's a dam shame that using the 12v option wouldn't increase the load, but obvious as to why when you pointed it out, that said I still missed the obvious :blush: so many thanks for taking the time to explain and the best way to go about testing them. :)
 

outoftheknow

Moderator
No worries :) hopefully my maths was right! Anyway the point is your plan to load test to find if one is defective is the way to go. :thumbsup:
 

Cocksure

Well-known Member
Woo hoo, worked a treat :)

Battery immediately failed under load, battery replaced and all working again.

Thanks @outoftheknow for confirming I was on the right path :thumbsup:
 

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