Flat battery season

[tejr]

I've so far not left the car standing more than a week, but when I have its always started first time. However I drove it on Saturday and come Monday after 3 attempts to start (and almost fire) I had to resort to jump starting Battery was reading 11.9v after the last attempt but I still would have expected it to be enough..

Anyway, I have now cracked out the ctek and put it into 'winter mode'

Luckily its not my daily drive, but anyone else been caught out unnexpectidly? I really didn't expect it to flatten in 2 days when its never let me down before!

[boss1uk]

new battery time me thinks if flat in 2 days. mine will go 2 weeks easily.......... that is with a new battery i might add,

[tejr]

Actually, on a related note, what voltage should the Cerb charge at?

I've installed a voltmeter but just put down the low voltage to poor TVR wiring (its hooked up to the stereo wiring, not direct to the battery) but it can read anything from 11.9v (lights/heater fan on) to 13.5v, but on average only around the 12v-12.5v mark.

I'm now thinking the random flat battery is more due to a lack of charge (ie BIG fuse!) and thus the low charging voltages where I would be expecting 13.8-14.4v

[gruffalo]

I think the standard out put of the alternater is 13.8V that would be dragged down by an old or faulty battery or having high current devices like heated rear screen, headlights and heater fan turned on. If you are getting 12.5 volts with things turned on I would say that is probably OK with a less than new battery.

If your battery is flat after 2 days it is breaking down internally and acting as a heavy load on your alternater, time to change it I am afraid.

[Chuggaboom]

I was told that coz of the relative size of the belt pulleys, there is little charge below around 2500 revs and actually none at idle, so if you're sat in traffic with lights etc on then don't expect a lively starter the next day

[boss1uk]

u should never drive at under 2500 revs (once warm) in a cerb so shouldn't be a problem. i find high the revs the better the car goes !!!!!!!!!!!!!! hehehe

[Cedar]

How long should a good battery hold its charge in a cerb? a couple of days sounds really scary.
The one in my chim can still crank it after standing for 3 weeks..

[Juddder]

For me with my Cerbera at two weeks with no use I'm pushing it as to whether it will start without a boost/trickle charge.

BTW on the charging/not charging question, the AA guy measured my alternator when we were jumping it [before I realised that you need a good ground and the top of the front alternator/A/C pump/whatever was the best place to get a solid connection] and there is little to no charge at idle.

So it's trickle charge everytime I get it out of the garage if not well used...

[Steve_T]

Aside: if you let a battery get deeply discharged, then sulphates form on the plates which prevent the battery from holding charge, which means the capacity of the battery is reduced for future use. Best to charge more often than just when you fancy using the car to avoid killing the battery.

[verminator]

Have always kept mine on an optomate charger, never had a problem even after not starting it for 2 months at a time.

[gruffalo]

verminator said:

Have always kept mine on an optomate charger, never had a problem even after not starting it for 2 months at a time.

2 months are you sure it is a Cerb you have, I struggle not driving mine for more than 2 days!!!!!