p38 2.5 battery charging

hello everyone has some of you may know i,ve been the proud owner of a 2.5dse for 2 weeks but due to the mot running out its sat on my drive since i,ve had it.now i,ve read about low battery power giving people some probs so coz its not goin to be mot,d till fri i,m thinking about running my m/cycle trickle charger straight to the battery.is there any pitfulls in doing this,will i trigger alarm or damage the ecu,s/fusebox etc has i,m not gonna disconnect the battery just run the charger to it.also when changing relays do you have to disconnect battery first.cheers

Shouldn't be any probs using a trickle charger while the battery is still connected however if the battery is very low then it may not charge up enough. These chargers are only really designed for small capacity batteries or keeping one topped up through the winter as you would with a bike. Better to take the battery off and give it a test and a charge using a bigger charger. A normal full size battery charger, even when set at 12Volts, can often put out up to 16Volts which is too much for the delicate electronics so best not do it on the car.

Only take the battery off a P38 if you have the EKA reset code or access to a diagnostic unless you use a memory saver. You could of course connect e.g. a bike battery to the connectors using small jump leads while the main battery is off. This will keep power in the system and keep you from having to reset every window, sunroof, radio etc etc. Some P38s have a back up alarm which will go off if you disconnect the battery but as long as you keep power in then that should be ok.

Removing relays is ok while the battery is on generally but maybe not while the engine is running however be careful what the relay is for, e.g. you wouldn't want to leave the keys in the car when you disconnect or re-attach the central locking relay just in case it goes, "thunk - ha ha, I've got your keys!!!" (In fact never leave keys in these cars even when everything is working for the same reason.)

I've put a motorcycle charger on mine, and whilst it trickle cahrges it it doesn't fully charge it up.

I wouldn't leave the car with the battery unconnected for any lenght of time though, the electronics may be sensitive to 16V, but I'd say they are more sensistive to 0V!

I've used some pretty beefy chargers in my time, and they've only ever gone up to 14.5V though.

cheers lads the trickle chargers on.i,ve also got a motorcycle battery to bridge the connections should i have to disconnect the battery to fully charge(fantastic idea)thanks for the replies

I've just done that on mine while I put a new batterty on......... Then one of the leads fell off. This is when I discovered that

1, my P38 has the back up alarm.

2, although I had the EKA code the alarm kept going off till I tried starting the engine after inputting the code about 5 times.

3, I've got good neighbours somewhere, the police turned up to investigate the damned alarm.

Steve

Steve, The back up alarm won't activate if you disconnect the battery within 17 seconds of switching the ignition off. In other words if you have to take it off again without the spare battery connected, have everything loosened, switch the ignition on, then off, run round the front and pull the connectors off. If you use the EKA code the car expects to be started (I think within 30 seconds) hence why you had prob 2 as well.

Cheers mate, I'm on a bit of a learning curve it's a bit different to my 20 year old ex army 110 and the wifes old Disco

Steve