Battery voltage query

[fabes]

Have just spent 5 mins searching on here, but cannot (quickly) find the answer, so....

Finally got time to put the CR Pro on the MB with the fully correct model number on it and found a number of electrical faults. Secondary door locks, steering wheel something seatbelt tensioners (stored and current), non are show stoppers, but the battery is often at the seat of the problem

At rest it'showning 11.45

What should it read?
If it's too low (no issue starting though) is MB Newcastle my best bet?

PS I put a new AUX battery on last year from MB Newcastle,

PPS stop start doesn't activate in day to day useage, another indicator on battery I understand......

 

[55AMGCLK]

Fully charged battery should be 12.6 or above.

11.45 is low. If your stop start issue is low battery related, it should work after a long drive.

 

[190]

Problem is when and where to measure the voltage. The only real way to get an accurate figure is to measure at the battery or jump terminals under the bonnet. The car must be asleep and the battery rested for several hours after the engine being run or the battery charged. Then you should measure a minimum of 12.6 or more usually 12.7 volts. Any lower and it needs fully charging and resting before taking the measurement again.

 

[David404]

Problem is when and where to measure the voltage. The only real way to get an accurate figure is to measure at the battery or jump terminals under the bonnet. The car must be asleep and the battery rested for several hours after the engine being run or the battery charged. Then you should measure a minimum of 12.6 or more usually 12.7 volts. Any lower and it needs fully charging and resting before taking the measurement again.

Ideally bring to 100% full charge with good charger such as a Ctec allow to rest overnight and then check voltage.

 

[Flyinspanner]

^ but after charging let battery ‘rest’ for half an hour before checking.

should be about 12.4 minimum.

on the car with engine running, lights on, blower on, you should see about 14.3v if it’s charging ok.

 

[AMGeed]

If the worst happens and its a new battery, I'd check the price from Tayna, then get a quote from MB Grangemouth with a mention of the forum for the best discount.

019 AGM Car Batteries

 

[grober]

As another indication - how old is the battery? With todays heavily electronic dependent cars over 3 years -suspect--- over 5 -renew as a matter of course

 

[55AMGCLK]

I believe the Bosch S5 has a 5 year warranty. MB will only provide 2 years.

ECP may price match Tayna for easier returns.

 

[AMGeed]

If its stop/ start it will have an AGM battery.
Only a 3 yr guarantee with them usually

 

[55AMGCLK]

If its stop/ start it will have an AGM battery.
Only a 3 yr guarantee with them usually

I thought that too but Bosch have started offering 5 years. (About time )

 

[Ted]

As others have said, that is too low.
You either have a faulty battery, charging issues or a parasitic drain - the voltage alone doesn’t give the full picture.
Charging is the easiest to eliminate. Check that the voltage with all consumables off and engine running around 1500 rpm is around 14.3 volts. With headlights and rear screen on it should be above 14 volts. Measure this across the battery with an accurate voltmeter.
This will give a good indication on the charging system - an auto electrician will also check charge current.
The battery - lots of graphs to show what the voltages should be at different states of charge but the only real way to test is to fully charge it and then do a load test on it and measure how it holds up. Halfords and the like have devices that inject an AC current into the battery to test its impedance. Not bad, but I’m not convinced by them.
If you have a parasitic discharge the battery will lose charge (and therefore voltage) over a number of days if it is connected to the car. It won’t do this if not connected. So measure the voltage across the battery over a few days to see if the voltage drops.
Again there are other methods of measuring for a parasitic drain - measuring the current flow with the vehicle asleep is the best way, but unlocking the car/having the bonnet open will wake the car up and may be misleading.
Fyi, I’ve recently replaced the battery on my Jeep. I have a plug in voltmeter in the fag lighter - tested against my Fluke dvm and it is surprisingly accurate (although another one I have is less than accurate). Over the last couple of years the voltage in the morning had dropped to 11.5 volts and I had a couple of spurious fault messages when starting. The voltage is now much more healthy - 12.2 volts in the morning, probably 12.4 - 12.5 at the battery and the stop/start and intelligent charging now come in within a mile or two. This hasn’t worked consistently for over three years. At least on the Jeep I can turn the stop/start off permanently if I want.

 

[AMGeed]

I thought that too but Bosch have started offering 5 years. (About time )

Thats good then. Last I looked a few weeks back ECP had Bosch AGM batteries and the guarantee was only 3yrs. 5 yrs is far better.

 

[BTB 500]

11.45V (if that's correct) is basically dead, and the battery will degrade if left at that state of charge. The voltages vary but this table is about right (open circuit voltage, after standing for a couple of hours):

 

[fabes]

I thought that too but Bosch have started offering 5 years. (About time )

View attachment 92896

Thanks all

So it's lookalike it's battery time (potentially it's on its first still, eight years on)

Where was that Bosch battery at that price.....?

 

[AMGeed]

Thanks all

So it's lookalike it's battery time (potentially it's on its first still, eight years on)

Where was that Bosch battery at that price.....?

Tayna , according to the logo at the top of the screenshot in Post #10

 

[55AMGCLK]

it was on Tayna.

the Bosch battery price is £190 delivered.

 

[fabes]

That's where I looked......

Can't find it (in my size) at that price.
Ho him, will shop around

Cheers

 

[55AMGCLK]

That's where I looked......

Can't find it (in my size) at that price.
Ho him, will shop around

Cheers

The price in the screenshot was for Enduroline, appeared in the screenshot when I was looking up the guarantee for the Bosch

 

[grober]

Bosch Versus Varta batteries-Both the same Batteries?

 

[Petrol Pete]

I am going to ask the moderators again.

Do you not think it is time for a totally separate section on our forum where we can discuss batteries ?