Battery Test

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Battery Test

Postby HansR on Mon Jul 12, 2010 2:59 am

I have 6 new flooded batteries (6V Trojan 145) in series of two to make 3 12V banks. They did not perform. A load test was recommended. I tested 2 of them sofar using 3 auto head light of 55W in series giving me about 12.8 V (average, close to 5% of Ahs). Here are the results:
Time ∂Time Volts Amps Amins Cumulative Ahs
8:35 13.10 0.0
8:40 5 12.59 13.9
9:10 30 12.48 13.1 405 6.750
9:40 30 12.21 13.1 393 13.300
10:30 50 12.11 13.1 655 24.217
11:30 60 12.05 12.9 780 37.217
12:30 60 12.07 13.0 777 50.167
13:30 60 11.92 12.9 777 63.117
14:30 60 11.97 12.9 774 76.017
15:30 60 11.76 12.7 768 88.817
16:30 60 11.70 12.5 756 101.417
17:30 60 11.59 12.5 750 113.917
19:00 90 11.57 12.6 1130 132.742
20:30 90 11.30 12.5 1130 151.567
22:15 105 11.01 12.6 1318 173.529
23:00 45 10.36 12.1 556 182.792

I will be testing the others soon. I bypassed my SAR because it is used to keep the rest of the system going.

Questions: a} These are batteries with a nominal 260Ahs. They delivered only 183Ahs. Are they defective or is this normal for un-broken-in batteries?
b} I tested 2 at the time because of the problem of getting 6V devices. Is this legitimate?

Your advice will be greatly appreciated.

HansR
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Re: Battery Test

Postby Coulomb on Mon Jul 12, 2010 11:28 am

Battery manufacturers test batteries at a constant current, not a constant load resistance as you have done. A constant current is easier to measure Amp-hours.

With your method, getting an accurate result manually is unlikely because the current is changing over time. An electronic meter that can take readings every second and compute Amp-hours is necessary.

Breaking in will help 5-10%.

However, actual capacity is often 15-25% less than what the brochure says.
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Re: Battery Test

Postby HansR on Tue Jul 13, 2010 12:39 am

Coulomb,
One variable I have not mentioned is the ambient and battery temperature. We are in a climate (Malaysia) where the ambient temperature during the day is about 32 - 34 deg C, while at night it still stays around the 30's. How does this affect the various readings?

HansR
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Re: Battery Test

Postby Coulomb on Tue Jul 13, 2010 2:04 pm

Amp-hours will be more above 25C.
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