OK to charge battery with cables attached?

[michel88]

My uncle has asked me to charge up the battery on a approximately 2000 Nissan minivan. He is storing it for a friend in his garage and the battery is low and it won't start. He needs to move it to get access to his lawn tractor. I would rather not remove the battery cables to charge it because I am not sure if it will mess up the computer. I always remove the cables on my old cars to charge the batteries. I just don't want to do any damage or create problems.

I had a problem with my daily driver that I inherited when my wife got a new car about three years ago. It had an alarm system with a control fob that was not part of the key. When the battery in the alarm fob went bad I just stopped using the alarm and locked it manually. I later removed the fob from the key ring since I wasn't using it anymore. When I replace the battery and the old one was removed it set the alarm. I was at a battery warehouse and the alarm immobilized the car. I was stuck and had to get my wife to find the alarm fob, bring it to me and replace the battery in it. Then after using it to lock the doors and then unlocking them the car would start. Not sure if this is the case with the minivan, thats why am asking.

[jan arnett (2)]

I have never had a problem with leaving the cables connected. There are several potential issues which you should be aware of. If you have corrosion between the cable and the battery and you are clamping the cable you will have a high resistance. If you have a dead short on the car being charged you will have a problem.

Hope this helps

Jan

[Larry Schramm]

If you are charging the battery from one car to the other, I would have the key for the car being charged off while the charging car is running.

[michel88]

Jim and Larry, thanks for the info. I will be using a battery charger and I will leave the cables connected, also will check for corrosion.

[rocketraider]

Woody, I've never seen any issue by leaving cables connected unless the cables themselves were in bad shape.

I generally leave the cables connected with the Battery Tender connected and running too; as a matter of fact the BT came with ring terminal leads designed to permanently mount to bolt type top mount terminals. They don't work but so good with side terminal cables and don't work at all with GM Spring-Rings, but the alligator clip leads handle those and spare batteries OK.

I'll admit to some redneck ingenuity on the Toronado and its Spring-Rings. Car has an easily accessible junction block post on the fenderwell that I put the ring terminal (+) lead on, and the (-) lead is connected to the A/C compressor bracket. Good permanent connection and remote from the battery. I expect I'll eventually wire up the other Oldsmobiles similarly as they all have those junction blocks.

[Guest Bluesmobile]

Take my advice and remove the cables any time you charge a battery in the car. I made the mistake of NOT removing the cables one time and it cost me $60,000. The battery in the car had run down and I was in a hurry and left the charger on it overnight. Turns out that there was a short somewhere in the car that had run the battery down in the first place. Rather than just run the battery down, now it had an unlimited supply of juice which overheated the wiring and caused a huge fire in the middle of the night. Please learn from my stupid mistake and disconnect the cables when you use a charger. I knew better but it was late in the evening, I was tired and careless.

[Guest]

No problem leaving them attached and will not harm the ECM. What will happen if you disconnect is you will have to reset all your radio stations after the install.

Don

[Reatta Man]

ANY time you disconnect battery cables, just make sure you do it with plenty of ventilation.

Charging batteries produces hydrogen gas. VERY explosive when concentrated in a small contained area, such as around a battery in a fender well or on an enclosed engine compartment.

On any computerized car, you can charge the weaker battery with the cables connected and the charging car running. But, as was previously suggested, only do that when you are keeping an eye on the car. When the car starts, turn off the engine of the charging car before disconnecting the cables; this will help prevent a spike to that car's computer.

Finally, I would NOT use a high-end Japanese car with a coded key as a charging car. On several Toyota models (Lexus) if you spike the computer and fry it, you have to get a new computer from the factory that is coded with the keys---ranging from $1200-2000. And no, on several models, the factory will NOT let a dealer or distributor recode a computer and keys.

Joe

[rons49]

ON new cars always turn OFF the donor vehicle. If there is a power surge from one car to the other a computer module can blow. Since 1980 most cars are computer controlled. The donor car is usually the one running, since the reason for the boost is due to the weak battery in the receiver car. That is the only car you can remove the cable from safely.

[Guest]

If you read the original thread michel88 he is asking about charging the battery of a Quest. He is not asking about jump starting it.

Don

[D Yaros]

No problem leaving them attached and will not harm the ECM. What will happen if you disconnect is you will have to reset all your radio stations after the install.

Don

Someone feel free to jump in here and correct me if I am wrong, but if the battery is truly (totally) dead, will not the radio stations have to be reset anyway?

My DelTran Battery Tender comes with a cable to permanently attach to the positive post of the battery, precisely so one may charge the battery without ever having to touch the factory cables.

One does not remove the battery cables when jumping a car, so why would it be necessary to do so when charging a battery?

Now, the direct short, that is another situation . ...

[Guest]

A completely flat battery 0 voltage will loose radio memory, ATC memory, clock. Not sure about key fob, my guess you will have to reinitial the system.

D.

[Guest]

A flat battery can be charged in the car. Also a FYI if you intend to leave your newer type vehicles (not talking about older type- anitque/show car) say for vacation or business trip, anything over a week. Most new cars have a extended storage switch located in the fuse box or a fuse which is labeled in the fuse box that you remove to keep the battery from going down due to all the systems mentioned in my last thread.

D.

[Larry Schramm]

You may or may not lose station present depending on the vehicle. On some completely dead batteries you may need to put them on a slow charge for as long as a week until they start to take a charge and then charge completely. I have done this to a number of "bad batteries" that were given to me and ended up using them for 4-5 years. Now this only works on a newer battery usually less than a year old. Will not work for a battery more than 5 years old give or take.

[rocketraider]

Heh. I have an Autocraft Silver 27F battery that was in the blue Starfire and went totally dead when I neglected it for over a year. At the time, it was four years old. Over course of a week or so I slow-charged it back to 1.275 SG and then charged it a couple times a year. It then spent a year in a friend's 66 Olds until he decided to get a repro battery for that car. I had the Battery Tender by the time it came home and it gets connected to that every couple months.

At nine years old, it holds a 1.265 SG charge and passes a load test with flying colors. That's not saying if I put it in regular service in one of the cars it won't die in a month, but I'm convinced that a little care and maintenance goes a long way toward keeping a battery viable. I sure haven't had the old car battery issues I used to have since the Tender came to live with them, and it keeps me from having to monitor three battery chargers and go thru the spring and fall charging ritual. It is money well spent for any old car owner.

I've done that with a couple other batteries and gotten as much as 12 years out of one Delco. Now when that one died, it did it with style. I went in WalMart and when I came out, it was dead in the water.

I've also gotten to where if I buy a new battery, unless it's an emergency installation I'll put it on a 2A charge at least overnight or until the automatic charger shuts off. I've found that a lot of on-the-shelf batteries are not fully charged, whether from storage or just bad sales preparation.

[michel88]

Glenn, I have both 6V & 12V Battery Tenders and they have made my life easier as far as battery problems in my old cars. My 63 Riviera has a Interstate battery that is at least 10 years old and still going strong. Thanks to all for good info on charging batteries.