Why do Noco-style chargers have you connect the negative cable to the battery?

[slacktide_bitog]

With a regular jump box, or jumping using another car, you connect the negative end of the good battery (or jump starter) to the ground on the car being jumped (an unpainted metal surface).

But Noco chargers, and the knockoffs of the same style, have you connect the negative cable to the negative terminal of the bad battery.

Why the difference?

 

[Owen Lucas]

I think it's more beneficial for a low amperage current to be connected directly to the battery to avoid any potential connection issues from grounds in every vehicle?

 

[slacktide_bitog]

I think it's more beneficial for a low amperage current to be connected directly to the battery to avoid any potential connection issues from grounds in every vehicle?

Are these Noco chargers lower amperage than a regular jump box or car's battery?

 

[Danno]

I use either connection with our GB70s. Almost every day lately.
2 in parallel on the really dead vehicles.
Wagoneers are the worse offenders.

 

[Blueshound]

With a regular jump box, or jumping using another car, you connect the negative end of the good battery (or jump starter) to the ground on the car being jumped (an unpainted metal surface).

But Noco chargers, and the knockoffs of the same style, have you connect the negative cable to the negative terminal of the bad battery.

Why the difference?

Jumper cables are live but the NOCO's not powered until you turn it on. No sparks to potentially ignite hydrogen.

 

[Owen Lucas]

Are these Noco chargers lower amperage than a regular jump box or car's battery?

A charger pushes out 1 to 10 amps, maybe a little more, whereas a booster box or car battery is a few hundred. My logic is a lower amperage might have issues going through a maze of possible old or weak connections on a ground point rather than directly to the battery. I'm not an electrician so just my .02.

 

[eljefino]

A Midtronics style battery *analyzer* needs to be directly connected to the battery, as it sends an AC ripple through the battery and analyzes its results as part of the test. I've hooked them up to remote "boost" terminals and gotten false positive failures.

A smart battery *charger* may well have battery testing circuitry, that relies on being close to the terminals, for more advanced functions like the automatic desulfation.

 

[supton]

When jump starting a car, the vehicle that is running is pushing current into the dead battery, possibly even when the dead car starts. When removing the cables, you can get sparks, and a charging battery can be gassing off hydrogen, thus... safety first. [Or third in my case, I never do this.]

These smart battery chargers, they aren't pushing that much current, and I have a hard time believing that they run some sort of AC test to test the battery... but if they did, clamping to other than the battery may cause it to read a falsely high ESR. Maybe I'm wrong and the newer/better ones do that, and really want to be on the battery. When measuring milli-Ω's, every bit counts. And in that region, it doesn't take much inductance to start to fake things out and make a simple peak detector circuit "see" a higher ESR.

 

[jim302]

When jump starting from a running car, spare battery, or old jump pack without a switch you will usually get a spark when attaching second cable. Batteries can generate hydrogen gas, and hydrogen gas + a spark = boom. Attaching the positive cable to the positive terminal and the negative to a ground away from the battery keeps the spark away from any potential hydrogen buildup.

(Most) modern computer controlled jump packs and chargers don't supply power until they detect a battery which means you will not get a spark when you attach the cables. This removes the risk of explosion. Jumping and charging directly at the battery terminals will bypass potential sketchy grounds, improving jump start success rates. It also gives you a better shot at getting a full charge on the battery if you are attaching a charger.