Alternator charging battery?

[TNReb]

I have a lithium battery with NMEA for my cranking and electronics.

When the outboard is off, it shows I’m pulling about 7-8 amps. This displays as a negative number, like -7.8.

When I’m running the outboard, the draw/current is around -14 when idling at low rpm. At 4000rpm, it’s showing -17.

Am I wrong in thinking that with the outboard running the alternator should be charging the battery instead of drawing more?

I’ve been having problems with my batteries going dead. The manufacturer just sent me a new replacement. This is the first one that has a NMEA connection so I can see exactly what the BMS thinks.

For what it’s worth, the Bluetooth app shows the same thing.

[ThomasD]

Sounds like your alternator or voltage regulator is shot.

[Redngoo]

If this is a mercury. I would post it in the Mercury forum

[yam911]

Any idea as to the brand and model of the motor?

[CJ1]

Your charging system is bad. The battery MFG sent you a new battery? Because of it going dead? The higher the engine rpm is the more current the engine draws because of the higher demand for the ignition system. I see this quite a bit with the symptom getting fixed (dead battery) and not the problem (charging issue) CJ