Battery conundrum - dying or not ?
Discussion
Wondered what people's take on this is:
10 year old car on original battery.
Last weekend noticed it turned over slowly, but did fire, Tuesday (after a -4 night) slow single turnover but managed to fire.
Seemed faster crank in the warmer afternoon for return jouney, covered maybe 20-25 miles. Was stopped and restarted on the return journey, no problem.
The car then wasn't used at all, until friday mid morning, very lazy crank speed on one try and then dead. Weather has been much warmer than Monday/Tuesday over the past few days.
Battery does show as discharged according to the charger. Left on charge for a few hours, starts no probllem. usual fast turnover, made a short trip (say 3-4 miles), car stopped, restarts fine, drive home again, stop, restart - all fine.
At this point 14.7v when engine running, 12.2v immediately after shut off last night.
This morning 15+ hours later its still at 12v, frost overnight, starts no problem with usual cranking speed.
I kind of expected it to lose voltage overnight.
Positive that no interior light etc left on at any time, usage (admittedly light) hasn't differed from normal. terminals tight.
I have a new battery to put on, but not sure if I'm wasting my time and money if I can't fault the old one at present.
I'd be happy to say that the cold last week / start of this killed the battery off - but it started (just) ok on Tuesday in the cold and died between then and Friday, when it was warmer - last few days have been 1 degree low to 8 degree high.So doesn't quite add up.
So slow crank last weekend - only just started Tuesday, dead on Friday suggests whatever is going on was happening las weekend and through this week, apparently hasn't happened overnight in to this morning.
The only thng I can think of is for some reason the car didn't shut of al power and caused a drain, but for some reason is now ook and hasn't done that ovenright...I don't know how I'd even prove that either.
So do I condemn the battery and change it or return the new one as not needed ?
Voltage is obviously a bit low but isn't noticeable in terms of crank speed / any alerts on board.
10 year old car on original battery.
Last weekend noticed it turned over slowly, but did fire, Tuesday (after a -4 night) slow single turnover but managed to fire.
Seemed faster crank in the warmer afternoon for return jouney, covered maybe 20-25 miles. Was stopped and restarted on the return journey, no problem.
The car then wasn't used at all, until friday mid morning, very lazy crank speed on one try and then dead. Weather has been much warmer than Monday/Tuesday over the past few days.
Battery does show as discharged according to the charger. Left on charge for a few hours, starts no probllem. usual fast turnover, made a short trip (say 3-4 miles), car stopped, restarts fine, drive home again, stop, restart - all fine.
At this point 14.7v when engine running, 12.2v immediately after shut off last night.
This morning 15+ hours later its still at 12v, frost overnight, starts no problem with usual cranking speed.
I kind of expected it to lose voltage overnight.
Positive that no interior light etc left on at any time, usage (admittedly light) hasn't differed from normal. terminals tight.
I have a new battery to put on, but not sure if I'm wasting my time and money if I can't fault the old one at present.
I'd be happy to say that the cold last week / start of this killed the battery off - but it started (just) ok on Tuesday in the cold and died between then and Friday, when it was warmer - last few days have been 1 degree low to 8 degree high.So doesn't quite add up.
So slow crank last weekend - only just started Tuesday, dead on Friday suggests whatever is going on was happening las weekend and through this week, apparently hasn't happened overnight in to this morning.
The only thng I can think of is for some reason the car didn't shut of al power and caused a drain, but for some reason is now ook and hasn't done that ovenright...I don't know how I'd even prove that either.
So do I condemn the battery and change it or return the new one as not needed ?
Voltage is obviously a bit low but isn't noticeable in terms of crank speed / any alerts on board.
If it really is 12v, then thats quite discharged. See https://sunonbattery.com/agm-battery-voltage-capac...
Crafty_ said:
10 year old car on original battery.
Change it.When they wear their internal resistance goes up, so a high charging voltage isnt a good indicator of anything other than the alternator works. Needs a proper battery test, but at 10 years just change it, its exceeded its expected life and is guaranteed to fail when its least convenient
Voltage is (relatively) meaningless if you don't know also what the current draw is at the time. For example, are you measuring voltage just after opening the car and unlatching the bonnet? Some cars can draw 10-15A in waking up various modules and doing initialisation processes on them. Unless you actually measured it with wires connected before unlocking it; AND knew the quiescent current draw at the time too, you're guessing. And what are you measuring voltage with? Many cheaper multimeters drift on voltage measurement quite significantly when their internal battery gets weak. And many cheap ones are basically hopeless at accurate voltage measurement in the first place.
But its an educated guess.
Best approach is to use a proper battery tester, there are old-style (which just impose a large current draw and monitor voltage over time); and newer ones which use imposed ripple current to determine State of Health more accurately, eg Topdon AB101 and similar.
But its an educated guess.
Best approach is to use a proper battery tester, there are old-style (which just impose a large current draw and monitor voltage over time); and newer ones which use imposed ripple current to determine State of Health more accurately, eg Topdon AB101 and similar.
Just for context a brand new fully charged 100% healthy battery will show 12.6/7 volts at rest, every 0.1 volt under that is a loss of around 15% charge as a rule of thumb.
As others have implied this is not 100% cast-in-stone but a good rule of thumb.
So, your 12.0 volts is around 15% healthy (give or take) so that is your answer.
Your charging voltage is fine, so the alternator is working.
Your experience of warmer temperatures "helping" is normal as cold is the enemy of battery efficiency.
Change it & you will be fine.
When you do change it (properly) check all connections are good.
As others have implied this is not 100% cast-in-stone but a good rule of thumb.
So, your 12.0 volts is around 15% healthy (give or take) so that is your answer.
Your charging voltage is fine, so the alternator is working.
Your experience of warmer temperatures "helping" is normal as cold is the enemy of battery efficiency.
Change it & you will be fine.
When you do change it (properly) check all connections are good.
Some cars alter their charging curve over time to suit worn batteries, and you should tell the car in the coding that the battery has been replaced to not cause problems with the new battery.
Dont keep using your dying battery, low voltage can cause all sorts of problems on complicated recent cars.
Dont keep using your dying battery, low voltage can cause all sorts of problems on complicated recent cars.
Edited by OldGermanHeaps on Saturday 10th January 15:50
Treat yourself to a new exide with the highest cca for the spec you need.
Your existing battery is giving you a warning, don’t ignore it.
While the cranking ability reduces with cold so does the discharge rate. If it lasts long enough come the summer it’s likely to become significantly discharged over a shorter period of time.
Your existing battery is giving you a warning, don’t ignore it.
While the cranking ability reduces with cold so does the discharge rate. If it lasts long enough come the summer it’s likely to become significantly discharged over a shorter period of time.
Volts have virtually nothing to do with a battery being fit for purpose. Amps are what is need, measuring the voltage will not tell you how many amps will be delivered to the Starter.
Do a load test if you have a multimeter, that will give you an idea.
A 10yr old battery wants throwing in the bin and replacing.
Youtube videos on how to do a load test. https://www.youtube.com/results?search_query=batte...
Do a load test if you have a multimeter, that will give you an idea.
A 10yr old battery wants throwing in the bin and replacing.
Youtube videos on how to do a load test. https://www.youtube.com/results?search_query=batte...
As I wrote on another thread, my 9 year-old 335d BMW was slow to start the other day. Then I realised it was the glow plugs pre-heating. Yesterday, I started on a long trip and got a (white) warning triangle showing in the instrument cluster. I couldn't check safely whilst driving, but when I arrived, I saw in the notification 'battery discharged'. On closer inspection it was the remote fob battery. I could still enter and start the car on the remote. The original 12V battery is still good, for now.
What voltage do you need to start a car?
My battery (standard petrol engine, not stop start etc) had a five year warranty and is six years old. I haven't used the car for the past couple of weeks including cold snap and yesterday it wouldn't start. Nothing. Dead.
I got out the (lead) battery pack I keep in a cupboard and charged it up overnight. Terminals read 12.4V. Connected it up the usual way, switched on. Engine click click clicks as per low battery but no turnover.
Aside from needing a new car battery, do I also need a new battery pack battery? It's at least as old as the car battery and I top it up maybe once a year (was that my mistake and why it's not working)? I think I've only had to use it once before (when it got the car started the last time it needed a new battery).
My battery (standard petrol engine, not stop start etc) had a five year warranty and is six years old. I haven't used the car for the past couple of weeks including cold snap and yesterday it wouldn't start. Nothing. Dead.
I got out the (lead) battery pack I keep in a cupboard and charged it up overnight. Terminals read 12.4V. Connected it up the usual way, switched on. Engine click click clicks as per low battery but no turnover.
Aside from needing a new car battery, do I also need a new battery pack battery? It's at least as old as the car battery and I top it up maybe once a year (was that my mistake and why it's not working)? I think I've only had to use it once before (when it got the car started the last time it needed a new battery).
OldGermanHeaps said:
Voltage means nothing . Its amps you need to crank an engine. Measuring static volts tells you almost nothing.
Partially true. What you need to start a car is sufficient power to turn over the engine at a certain rate, while the voltage doesn't drop below a certain amount (so the modules can still operate). This voltage is typically 7.2 - 9.6 volts minimum. A good starter will still have 10.5-11V during cranking.P = V x I
I agree that measuring voltage gives relatively little information to the state of health of a battery, unless it is a rested voltage with no surface charge on it. In most modern cars, it is impossible to measure this without disconnecting the battery. Thus, the suggestion to use a modern battery tester such as a Topdon AB101 or similar.
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