Community Forums

sbleiweiss · 01-01-2021, 08:02 AM

While driving with the genny running, which charges batteries, alternator or genny? I am just curious.

paddler1954 · 01-01-2021, 08:20 AM

This is just a guess, I'd vote for the RV alternator.

Brentw · 01-01-2021, 08:31 AM

A guess here too, I'll go with generator. Highest voltage will win. So, output setting of your charging systems (alt or genset) and size of the wire to batteries ( resistance) from each device. Will determine who can flow.

twinboat · 01-01-2021, 08:35 AM

Inverter/charger, or converter charger, running off the generator, will out charge the alternator in bulk mode and absorb modes.

The alternator may assist, if the batteries are very low, but alternators are regulated to about 13.7 volts. Bulk charge is higher in 3/4 stage chargers.

Some isolation systems disable alternator to house charging, when house charging is detected. That keeps the Alt Fail light off.

C.Martin · 01-01-2021, 08:42 AM

Bi-directional relays usually have a sense wire for ignition and gen run. With both sensing use...IE engine running g and generator running it defeats the bridge. Unless rigged much differently than our coach...the Genny will be powering you House Inverter or Converter and charge the house batteries...the Alternator will charge the chassis batteries. You will have to turn off the engine and/or the Generator to allow the bi-direction relay to tie the two banks...if you want to charge both from a single source. I realize there are many different combinations of devices in use...so yours may be different.

windsorbill · 01-01-2021, 10:38 AM

Quote:

Originally Posted by sbleiweiss

While driving with the genny running, which charges batteries, alternator or genny? I am just curious.

the generator will take precedence usually because it will have a higher voltage.

Many RV's mfg will recommend running the generator BEFORE you start the main engine after the house batteries are discharged. This minimizes the alternator from overworking/overheating and shortening it's life. Once the batteries are charged, this isn't an issue.

twinboat · 01-01-2021, 11:10 AM

One point, in most cases, the generator doesn't charge anything.

It powers the RVs electrical system, which runs the charging system, just like shore power does.