Battery float charger question

With a battery float charger am I supposed to connect the positive or negative first, and when I discount it do I disconnect the positive or negative first?

Always connect the positive first and then the negative.

And the reverse when disconnecting.


Are you sure? Because in the manual it says to connect negative first then positive but that seemed weird to me that’s why I am asking.

If you connect/disconnect the clamps with battery charger disconnected from power supply it won’t matter.

1 Like

My old timey thoughts, I usually connect the positive first, then the negative to the frame of the car last to avoid any potential explosion due to spark from fumes on the battery, Looking for better suggestions as I have not had a problem yet, but I learn new stuff every day. Then neg first when disconnecting, looks like I and tester are on the same procedure, though nevada has a valid point.

Do you leave the hood up on your car or can you close it when using the battery float charger? The manual said something about ventilation while using it so I’m not sure. Also if you close the hood will it hit the clips or is there clearance?

Attach they clips horizontally instead of vertically and the hood won’t know the difference.

1 Like

Matt, why question the manual ? It stands to reason that should be the final say about equipment usage.

It doesn’t matter which battery terminal you connect first, because the charger should be off/unplugged when you attach it to the battery. Connect both terminals, and then plug in or turn on the charger.

When I use a float charger on my motorcycles, I connect an adapter to the battery so I don’t have to connect it to the terminals, I just plug it into the adapter before I turn on the charger.

I have a solar float charger for my car, and it doesn’t have an on/off switch. When I connect it, I disconnect the adapter that has alligator clips, I connect the adapter to the battery posts, and then I plug the adapter into the solar charger, connecting both leads at the same time.

It depends where you’re storing the car. If you’re storing it in a locked garage, I would leave the hood up for convenience. If you’re storing it in public or outdoors, close the hood.

The warning about proper ventilation is likely about your safety and the possibility of breathing noxious fumes, not the amount of ventilation getting to the battery itself.

Float chargers are by design not going to charge at a high enough rate that would cause any electrolyte to boil off. As long as your garage is not hermetically sealed, it’s not of much concern, unless you have a defective unit.
If you have an older high rate charger, then there may be sparks on connection which might ignite some unusual accumulation of hydrogen gas. Almost all new chargers have an automatic circuit that will not apply any power until it detects a minimum voltage on the clamps, indicating a connection has already been made to the battery. Only then it starts applying power for charging, which minimizes the risk of sparking.

When charging a lead-acid battery hydrogen gas is generated. Hydrogen gas is very explosive. Thus the reason for ventilation – do not smoke a cigarette around a charging battery.

Better yet, do not smoke even if not around a charging battery.