Battery problems
Discussion
I've got a new battery but I'm puzzled about what the old one was doing.
My Volvo XC60 battery was dead in morning a few days ago. So I got a jump start from a neighbour and the car was fine for a couple of journeys for the rest of the day.
It was flat again the next morning, about 6V. I hooked it up to a battery charger that shows a charging light for just 45mintes then changed to "ready/maintaining". I was getting 13.2V on the battery (charger disconnected) in this condition. However the car would barely turn the crank when starting, then the voltage dropped after trying to start and I was back at the beginning.
So I was a bit more patient and after 3 hours had enough charge to start the car. It ran on idle for 10 minutes then a 10 minute drive to Halfords. At Halfords the battery tester showed a capacity of 250A for a 700A battery. But then the car wouldn't start so they gave me a jump start. I drove around for 30 minutes and even kept the revs at 1500 at traffic lights.
So back to Halfords and the capacity was up to 450A instead of 700A. I needed a jump start again, the crank wouldn't turn.
I'd expect it to be able to restart after that much driving. So either the alternator isn't working or the battery isn't charging. I'd checked the alternator charge after one of the jump starts, there was 14V at the battery terminal and because the battery was 6v before starting that voltage must have been coming from the alternator. Secondly the battery wasn't charging up on the charger either (full charged after 45 min!). So no charge from two sources would indicate the fault was in the battery and I got a new one.
Now here's the curious thing, I popped the old battery on charge last night and the orange "charging" light is still on this morning as you'd expect, it's been on for 11 hours, instead of 45 min I was getting yesterday.
So 2 questions:
- What was happening when the battery showed a full charge with 13.2V after 45 min? I thought damaged cells would result in a reduced voltage?
- Is it credible that lugging the battery out of the car and moving it around dislodged something so the battery is now charging as it should?
My Volvo XC60 battery was dead in morning a few days ago. So I got a jump start from a neighbour and the car was fine for a couple of journeys for the rest of the day.
It was flat again the next morning, about 6V. I hooked it up to a battery charger that shows a charging light for just 45mintes then changed to "ready/maintaining". I was getting 13.2V on the battery (charger disconnected) in this condition. However the car would barely turn the crank when starting, then the voltage dropped after trying to start and I was back at the beginning.
So I was a bit more patient and after 3 hours had enough charge to start the car. It ran on idle for 10 minutes then a 10 minute drive to Halfords. At Halfords the battery tester showed a capacity of 250A for a 700A battery. But then the car wouldn't start so they gave me a jump start. I drove around for 30 minutes and even kept the revs at 1500 at traffic lights.
So back to Halfords and the capacity was up to 450A instead of 700A. I needed a jump start again, the crank wouldn't turn.
I'd expect it to be able to restart after that much driving. So either the alternator isn't working or the battery isn't charging. I'd checked the alternator charge after one of the jump starts, there was 14V at the battery terminal and because the battery was 6v before starting that voltage must have been coming from the alternator. Secondly the battery wasn't charging up on the charger either (full charged after 45 min!). So no charge from two sources would indicate the fault was in the battery and I got a new one.
Now here's the curious thing, I popped the old battery on charge last night and the orange "charging" light is still on this morning as you'd expect, it's been on for 11 hours, instead of 45 min I was getting yesterday.
So 2 questions:
- What was happening when the battery showed a full charge with 13.2V after 45 min? I thought damaged cells would result in a reduced voltage?
- Is it credible that lugging the battery out of the car and moving it around dislodged something so the battery is now charging as it should?
How old is the volvo?
Get a multimeter, start the engine and measure the voltage on the battery. with no lights or fans on in the car you should see over 14 volts. with fans on full and headlights on it should drop to around 13.6v. if it is significantly lower than any of those then your alternator is at fault.
Get a multimeter, start the engine and measure the voltage on the battery. with no lights or fans on in the car you should see over 14 volts. with fans on full and headlights on it should drop to around 13.6v. if it is significantly lower than any of those then your alternator is at fault.
It's a mere 10 years old still on the original battery until I replaced it yesterday. 
The alternator is putting on over 14V with the engine running.
The main bit that puzzles me is how the old one showed as fully charged after 45 min on the charger and measured 13V. Clearly it wasn't full to capacity, but I thought a damaged battery showed up with a lower voltage?
I had 13V but at a puny number of Ah. A car battery is very simple with 6 cells in series. The capacity comes from the number of plates in parallel within a cell, not multiple parallel cells. So I guess there is a dodgy connection within a cell so some of the plates were disconnected, this would still showing 13V but a reduced capacity. A connection problem would explain the sudden loss of capacity (45 min to recharge) with no symptoms beforehand and the sudden return to capacity (ie over 12 hours to recharge as you'd expect).
The alternator is putting on over 14V with the engine running.
The main bit that puzzles me is how the old one showed as fully charged after 45 min on the charger and measured 13V. Clearly it wasn't full to capacity, but I thought a damaged battery showed up with a lower voltage?
I had 13V but at a puny number of Ah. A car battery is very simple with 6 cells in series. The capacity comes from the number of plates in parallel within a cell, not multiple parallel cells. So I guess there is a dodgy connection within a cell so some of the plates were disconnected, this would still showing 13V but a reduced capacity. A connection problem would explain the sudden loss of capacity (45 min to recharge) with no symptoms beforehand and the sudden return to capacity (ie over 12 hours to recharge as you'd expect).
Edited by Telurium on Friday 10th August 14:31
Well, if you put a new one in and all is fine, then obviously the problem was the old battery.
Exactly what the failure mechanism is, who knows? There days batteries seem to just suddenly die, although I know from Mercedes forums (I have an older Merc) that battery deterioration can cause all sorts of weird issues as the cars get older. Generally the advice on there is the car starts exhibiting a few apparently unconnected electrical problems is to try a new battery.
Exactly what the failure mechanism is, who knows? There days batteries seem to just suddenly die, although I know from Mercedes forums (I have an older Merc) that battery deterioration can cause all sorts of weird issues as the cars get older. Generally the advice on there is the car starts exhibiting a few apparently unconnected electrical problems is to try a new battery.
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