Hi,

I went to Autozone for a new battery for my 2011 Trail 4runner. After installing it, the man said I have a short somewhere because he saw a spark when putting on the positive cable. It must have been a small spark because I was watching and I didn’t see it. He told me to take the car in to have it looked over by a mechanic.

When I got home, I did some reading and found out that you can get a small spark when installing the new battery if the radio or other things were left on while removing the original battery.

Do I have anything to worry about? Should I take it in or is the small spark normal? Is there anything I can look for myself?

Also, I haven’t been driving the 4runner long distances very often so I bought a Noco Genius5 to charge the battery from time to time, maybe every month. Some people say to remove the battery to do this. Is it OK to charge the installed battery but outside in order to vent the hydrogen gas. I am especially interested in this for my Prius which has the battery in the trunk and is much more difficult to remove. I would like to keep the battery in the back and charge from under the hood where you would jump start the car. I asked on the Prius forum but received no advice.

Thanks very much, Kent

Hi Kent - did he connect the positive cable after connecting the negative? If so, that’s why I avoid discount auto shops because you should always connect the positive first. The Noco Gen5 is a great charger - I have one also and have been charging my battery in my 4Runner, in my garage for the last 8 years on a regular lead acid battery. My garage is older and definitely not air tight - I had done some testing a while back doing a full recharge/boost charge and a hydrogen gas detector and the readings were extremely low <1% at multiple points in the room. There is always air circulating out with ducting and is also pretty drafty so I guess it depends on your situation.

The spark is normal. The first spark is usually the result of the inrush current of electronics that have capacitors in them that are charging.


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Thanks so much, pianorocks06 and Travisstorma. I will just leave it then and mention it next time I take the 4runner into the dealer. I also have a feeling it is common here because it is very dry. Especially at night, whenever I put metal to metal I see a small spark. I also get a shock from touching metal.

I just changed out my 2007 Prius battery which was quite involved so I do know to attach the positive 1st. I was watching the Autozone guy from a distance and it was somewhat dark and difficult to see and so I can’t say for sure if that is how he did it. I should have paid more attention. Such a basic thing I would think even a discount auto worker wouldn’t make that mistake. They must do hundreds and he sure talked like he knew what he was doing . On the other hand, today I reset the battery because it was seated on top of the tray and the cable on the negative post wasn’t fully seated. Hmmmm.

Thanks again to both of you. I appreciate the help!

Anyone working at car parts store and installing battery knows Positive terminal gets connected first, it is just common sense. Spark at terminal when it gets connected is not a big deal since at some distance current will jump the gap similar to what spark plugs do. You are overthinking it, don't worry.

Great. Thanks for the confirmation. I won't worry about it and I have learned something new.