necessary to disconnect battery cables prior to charging ?

when I hook up a external battery charger to charge dead battery is it necessary to disconnect the battery cables or is it OK to leave them on ?

I have always disconnected bur I see people do it with the cables connected

so can it hurt to leave the cables connected ?

 

With all lights, radios, etc. off, there is no problem. Best bet is the same as for jumping from another car - positive to positive and negative to a good engine ground.

 

Well first off if you're having to recharge your batt often there's a problem with your charging system that need to be fixed ( Batt, Alt,Volt Reg,Wires,Terminals Etc. ).
My answer to your question would be yes you're better off just disconecting one of the car's terminals or both of them prior to recharging battery, just in case.

 

naw , just a wife (or me ) who leaves the lights on from time to time .

Ive just always disconnected one terminal but its a PITA plus if battery's dead as it is now I can put the charger on and have her take it off when she needs to leave .

If I pull the cable then I have to be here to reconnect

 

Agree with Goldstar.

Side note to anyone who reads this: Be VERY careful about jump starting your late model car. Some make/models have specific procedures to follow that require more than just + to + and - to - and if not adhered to can cause damage to some electrical components. In many cases your RADIO must be turned off or it can be damaged during the jump. The safest method to jump is with a portable jumper box and not jumper cables with the jumping vehicle running. This is because with the jumping vehicle running you are putting 13-14 volts through the cables. That was okay on your '57 Chevy, but not necessarily a good idea on your '07 Chevy.

 

Why take the chance? I can't categorically say charging the battery can harm the car, but with all the sensitive and expensive electronics on a car nowadays, I'd hate to think I'm putting a voltage spike through the system. I disconnect the battery. It only take at most a couple minutes.

 

Provided it's not one of those vehicles with the battery buried and only a remote terminal stud showing.

 

i gotta agree with TTG...jump starting todays vehicles is VERY risky. if it's dead in your driveway, connect your battery charger properly and then plug it in or turn it on(mine has an on/offswitch), don't connect it to the battery with it already on. be sure to fully charge the battery...the lowest rate for a long period (over night, preferably). not charging fully is very hard on charging systems...contrary to popular belief, alternators (generators for you OBD II purists) are NOT battery chargers, they are battery maintainers.

if I go on a service call for a car that won't turn over, i take a hot battery with me and swap it out to get the car to the shop...then charge and test the customers battery while I diagnose the dead battery condition (if necessary...i've left the lights on too!). this ensures the least risk of zapping sensitive electronics (have you priced asian or euro electronics lately?) as well as the least stress on the charging system.

 

There's mechanics who make house calls???

 

Yes - they're called relatives!

 

Yeah, forgot; I'm the one in the family who fits that description.

 

And soooooo appreciated, no doubt. That's why you get all the fifty dollar bills in the Christmas cards.