C5 Battery

wigelywoo · Post by **wigelywoo** » 07 Feb 2009, 14:43

Had my battery tested this morning.
Voltage ok
Amps only 375
Should I be looking for a new battery

2.2 hdi

Post by **myglaren** » 07 Feb 2009, 15:01

What should the cranking amperage be?

One thing that C5s are very sensitive to is any drop in voltage, which will occur if too much is demanded of the battery.

I keep considering installing a new one as it seems to crank rather slowly especially first start of the day.
However, there are none of the usual indications that the voltage may be dropping, other than whan I left the headlights on for ages while fixing daughter #1's mini. On starting I got an airbag or ABS warning, not sure which now. Gone the next day so it can't have been much to worry about.

If you aren't getting any electronic lunacy you are probably OK. Usual ones are FAP/Eolys warnings, windows going nuts and dropping into "Crawl Home" mode.

wigelywoo · Post by **wigelywoo** » 08 Feb 2009, 09:43

this link shows cold cranking amps @680

http://www.performancebatteries.co.uk/f ... ttery_info

Post by **myglaren** » 08 Feb 2009, 10:44

There must be a reason you are down to almost 50% of that.
Is it the battery type specified for the car? If it has ben replaced, perhaps someone cut a corner, put a secondhand battery in that is for a smaller engine, or a petrol engine.

Is the battery fully charged? Alternators don't do a very good job of charging a depleted batter, especially if you are running lights, rear screen heaters, aircon etc. and doing shortish trips. I'm surprised mine survives at all.
How old is it?

I keep telling myself I will pull the battery and give it a 48 hour charge but always come up with some excuse not to. Can't be any good in the long run. I do do a few longish trips but too infrequently to be much use.

reblack68 · Post by **reblack68** » 08 Feb 2009, 13:21

Doesn't that just mean that the starter only wants 375 Amps?

Post by **Peter.N.** » 08 Feb 2009, 15:03

Could be due to a high resistance in the starter/earth circuit. Check the voltage across the starter and compare it with that across the battery. An alternator that is running correctly should be good at keeping the battery up, they regulate at about 14v and a fully charged battery is 2.2v per cell, I make that 13.2v. Most have an output of 80 amps or more which should be well up to the job of running all the normal accessories - unless you have a 1kw audio system.