Disconnecting Battery - wow! big spark

MFL wrote:
I have some spark when I disconnect my battery. I disconnect the neg first, and hook it up last.

My radio cannot be shut off, and then I also have the alarms. When I reconnect the battery, I get some arcing too. Does anyone know if this sparking can cause any damage to electrical components?

Thanks, Jerry

The risk that you take is if the battery is off gassing the spark can blow up the battery. That is why they tell you to ground jumper cable negative cables to an engine point not the battery negative terminal. Moves the spark away from the gassing battery.

While in the Coast Guard years ago I was working with the base engineer to jump start a Loran A station generator. The batteries were being charged from a charger in the control panel. I was at the next generator over and correctly connected the jump cables red to positive and black to negative. The engineer crossed his and the batteries blow up in his face.

I ran him outside an turn a hose on him, and he was ok!

So gassing batteries and sparks are NOT good. A marine style battery switch is sealed to prevent gas vapors from reaching the spark at connection or dis-connection.

Anyone getting a healthy spark should find out why and resolve that issue.

I too have a factory switch that only turns off some of the loads. So I installed two addition switches. One is a main disconnect and the other is for slides and jacks that I turn off while traveling or parked for extended periods.



200 amp fuse is for a Heart Freedom 10 inverter/charger. This great little inverter has been in two of our boats and now two trailers. It has a 50amp 4 stage charger, 1000 watt inverter and 30 amp auto transfer switch. Brought it back around 1991 for $465. Converter is only used when dry camping with Honda eu1000i generator with its own power inlet, the rest of the time the Freedom 10 does the charging.



Chris

+1
Negative first is just for safety of shorting out a wrench or tool. touch a wrench from negative cable to ground it's no big deal. If the negative is off first you can ground out the positive with no problem.
If your unhooking the positive first and make connection to ground with say your ring with the wrench touching the other side, big problem.

Duck wrote:
I have been told several times by people who have been in the battery-auto-marine electrical business for years that you should always disconnect the negative terminal first when removing a battery.
Don

There are good reasons for doing that but not because the positive terminal will not spark.

With the negative connected and the positive disconnected any metal part of the car will spark if accidentally connected (say by a wrench) to the positive terminal. With the negative disconnected the only accidental short is to directly contact the two terminals.

I have been told several times by people who have been in the battery-auto-marine electrical business for years that you should always disconnect the negative terminal first when removing a battery.
Don

greatwhitenorth69 wrote:
Why do people quote info when they haven't the slightest idea of what they're talking about, just heard it from the uncles, girlfriends, cousin's grandma, so it must be true. If you don't know don't give an opinion, it just confuses the whole thread. A spark will come from either terminal if there is draw, a dead short will pop a fuse, or melt the wiring if not fused.

I think the problem is confusing the term ground in a 12V system (which is not a ground but the positive terminal) with the ground in a 120V AC system where the ground is really grounded to earth and normally does not carry current and so will not spark if disconnected.

It would be better not to use the term ground in our 12V systems and use the accurate term positive.

4x4FF wrote:

wgriswold wrote:
How would removing the ground cable first negate any sparks?

It has to do with current flow. You will almost never get arcing when disconnecting the ground first even if there is a dead short.

Steve

Why do people quote info when they haven't the slightest idea of what they're talking about, just heard it from the uncles, girlfriends, cousin's grandma, so it must be true. If you don't know don't give an opinion, it just confuses the whole thread. A spark will come from either terminal if there is draw, a dead short will pop a fuse, or melt the wiring if not fused.

Part of the battery draw is the gas detector. They are hard wired and and always on when there's power. I have a battery cut off in the front compartment but what a pain to get to. I have found for years the easiest is to take the negative of the battery off.

I don't think arcing matters all that much unless it damages the connectors. But the battery draw is a problem over a several week period.

I have some spark when I disconnect my battery. I disconnect the neg first, and hook it up last.

My radio cannot be shut off, and then I also have the alarms. When I reconnect the battery, I get some arcing too. Does anyone know if this sparking can cause any damage to electrical components?

Thanks, Jerry

My battery disconnect from the factory does not disconnect everything. It does shut off the lights. The landing gear still works. I was thinking of adding a complete cut off so when I am plugged in at home, I won't cook my battery if I forget to check the water levels in the battery. Is this sound?