Charging the battery

[reef2k]

Do i need to disconnect the positive lead before connecting a charger ? I want to charge my battery tomorrow,after first checking/cleaning terminals. it needed a jump today,so hope to keep it starting for a couple of days until i get time to get a new one,if needed.

[milleplod]

I think it depends on what sort of charger you've got. If its an 'intelligent' one, it shouldn't be a problem - I charged my previous battery on my '09 C5 in situ using my CTEK charger a couple of times, with no issues at all. If your charger is a traditional one that simply charges at a constant rate, I think its a no-no charging with the battery still connected.

Pete

[reef2k]

Hi Pete
It's a modern pulse charger so was hoping it would ok,as i don't want to lose the radio code etc. i had thought about plugging my jump start box into the cigarette lighter to retain voltage if i can find the supplied lead.

[GiveMeABreak]

You won’t loose the radio code - they don’t have this feature anymore, as the head units are VIN coded to the vehicle.

Absolutely agree with what Pete said; only use an intelligent charger that will control the charge and shut off as needed.

Also, if your vehicle is fitted with a battery charge status module, the negative of the charger should be attached to this and not the battery negative post. If you’re not sure if it is fitted with one, PM or post your VIN or Reg. number and I’ll look it up for you.

[reef2k]

Marc, i've bit the bullet and disconnected the battery,so hope it'll be ok. it's now charging, i started it earlier with my jump-start unit as i needed to go to the post office.i left it running while i was there and returned home,turned off and tried re-starting,but wasn't having it. Checked voltage yesterday,it was 12.8 V when flat,so will check again with ignition on.Hope it's the battery and not alternator. Battery light always goes out !!

[RichardW]

12.8V is quite high for a standing battery...

What symptoms does it give when it won't start? The starters on these seem to be a bit weak, resulting in a no-start situation when the engine is warm; you just get a clunk. My 307 has been doing it a while - but since I failed (twice) to get the old starter out, I never got the new one in!

[reef2k]

It just about cold starts with my little 22 amp jump start unit,but not tried a hot start.Yes,12.8 V is high for a flat battery,so may need to get it tested before buying a new one.

[reef2k]

New battery arrived and all is well again,no issues having been disconnected for 3 days Batteries are funny things ..when i first charged the original,it behaved normally,charger took about five hours to complete cycle,re-connected and was as dead as when it started. Put on charge again and after the 3 minute test procedure,the charger rejected it with all lights turning red,tried again,same result even though the magic-eye was happily glowing green. i may lever off the sealed cover and check the water levels,but guess it's beyond help ?

[white exec]

Likely a duff cell, or battery is self-discharging.
Glad the new one is doing its stuff.
Many car systems are now quite intolerant of low battery voltage, even one that will crank the engine.
Low battery voltage does glowplug system no favours in cold weather; even worse while cranking, which is just when you need the GPs.

[reef2k]

My Dad's old BMW 325i would turn over fine,but wouldn't fire unless fast enough,and that was built in 1987,so it's not just modern vehicles,but i know what you mean. The 70 mile trip home in the dark last saturday killed off the old battery,all appeared fine until then,but obviously not all was well.