Dead battery, need help?

What is the proper way to attach a trickle charger to my 400i?

 

disconnect the battery 1st.

 

Why??? A trickle charger is only delivering like .3A or something really small like that... If the key is off I don't see how hooking a trickle charger up to a hooked up battery could have any impact on any system other than the battery it is charging. Please enlighten me master Dave, as I am certain I will need one for any 400 I end up with too.

Thanks,
James M
Austin, TX

 

Its a matter of not taking a chance; or risk vs reward.
The ignition units are famous for blowing when they get a spike from the car being jumped or from an errant spark. Those units are NLA and a rebuilder will charge well over a grand to rebuild one.
Someone here will argue and say it doesn't matter and they are probably right. But again, its a question of risk/reward. Call me a conservative, I like it that way.

 

woulndt call you conservative..ill call you right!!..

 

Thanks Dave. Here is a second question; why wouldn't disconnecting and reconnecting the battery cause a spike to the ignition units?

 

That is my thought too. The battery itself can deliver a HUGE amperage, the little trickle charger hardly any at all. I would think there would be a much bigger risk to hooking up and disconnecting a battery than a maintainer...

Not trying to be argumentative here, just trying to follow the logic on this one.

 

+1 on the battery disconnect! I always remove earth cable first when disconnecting, connect earth cable last on reconnect + I always disconnect the battery for trickle charging even though I have a battery disconnect switch, and have had no troubles w/Elec. Ign. unit (the original one is still running strong).

 

Why not just replace it?

 

Dave is right. Electronic ignition modules of this vintage are all notorious for ground buss bias issues. Pull an arch on the ground plane and you run a risk of damage. When using a trickle charger I recommend that the battery cables be removed for two reasons. First, if you have any electrical leaks you run the risk of overloading the charger, running the risk of having a short to ground...... and #2 it takes no time at all to remove the cables. Always remove the ground before removing the positive, and replace the positive before finishing with the ground.

 

I will go with what the expert say, thanks Dave and Boyd.