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Battery Testing

Paulkp
Paulkp
in General Ford Related Discussions

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This is a regular topic on most car forums including this one !

Just measuring no load voltage does not provide much information, it is how the voltage drops when presented with a known load that will give you a better indication.

Having four cars, and a spare battery sitting on a small solar charger, I did some measurements using an old fog lamp fitting with a 55W H11:

H11 Load
55W Bulb 		Battery
Capacity 		No Load
V1 		Load
Current
A 		On Load
V2 		Voltage
Drop
V3 (V1-V2) 		Battery Internal
Resistance
m Ohm (=V3x1000/A)
Solar/Ca 390/43Ah 12.44 4.27 11.58 0.86 201.41
Pb 590/60Ah 12.28 4.25 11.93 0.35 82.35
Ca 1 590/60Ah 12.43 4.29 11.91 0.52 121.21
Ca 2 500/52Ah 12.47 4.31 12.29 0.18 41.76
Ca 3 500/52Ah 12.40 4.30 12.20 0.20 46.51

 

All the cars have run during the last ten days, and batteries are at least five years old apart from the Ca 3, which is about 18 months old.  Not a perfect test, but wil give a good indication.

I'm planning to do some thing more comprehensive using in car loads at some stage, but not on a sunny day like today !

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