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- 27 Jan 2008
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The battery in my phone is flat, but the battery in my car is not, it shape does not change, being charged or discharged, there does seem with flooded lead acid a marked decline in available amps as the battery becomes discharged, this is less evident with glass mat or valve regulated lead acid, it also seems odd that discharge a charged battery to 10% and it will fail to start a car, but charge a battery from discharged to 10% and it will start a car.That would be FLAT.
I have noted with Nickel Iron batteries used on buses and milk tankers they do seem to give full starting amps until the reach fully discharged, which is why they are used with milk tankers to suck the milk in and then still start the prime mover engine after. But alkaline batteries are stored discharged, but lead acid are stored in the charged state.
But when a fork lift is reaching end of shift it goes slow as battery gets need to fully discharged, and electric cars at least a Renault Kango van also goes slow when it reaches end of shift, so it seems there is no different to NiMh or what ever is fitted in electric cars now to lead acid they both with high loads reduce the amps available as they become discharged.
There is clearly even with flooded lead acid a difference between makes and types as to how the battery performs as it becomes discharged, specially when lights left on, and you try to recharge with small battery charger, the threshold between starting and not starting does vary, even when both are claimed to be vehicle batteries. With traction batteries or leisure batteries I have looked at Ah rating and it has claimed 90 Ah and I have put lights on it rated at 5 amp and it has lasted as expected 180 hours, maybe a little more. This is what we are doing with a phone battery, it is being discharged over a long time.
It was claimed the battery was faulty on my wife's car, it would fail to start the car, it was a VRLA in that car, and it failed after just stopping, we would sit there wondering what to do, I would say give it another try and it would spin the engine over as if fully charged, but had acted as if totally discharge 10 minutes earlier, the battery was changed and we retained old one to use in caravan, car has been A1 since change, and old battery seems to be A1 used in the caravan, so some lead acid batteries do seem to have a life of their own.
It just seemed odd that the old Honda Jazz battery recharged so quickly.