Itasca (Winnebago) house battery charging

[Flair-22]

I have a 2014 Itasca Sunstar 26HE (same as Winnebago Vista). An interstate battery rep told me that the house batteries are not charged while driving. He claimed the wire from the alternator to the batteries is too small to provide a real charge & that the only way to charge the house batteries is either from shorepower or the generator.
I'd like to know if anyone has looked into this and knows for sure if this is true, one way or the other.
Thanks.

[twinboat]

Wow, that was some bad info.

The alternator wire is sized for the alternators maximum output, probably 160 amps. That wire connects to the chassis battery, like any vehicle.

In motorhomes, they use battery cable size wires between the chassis battery and house battery for boost starting, and since its there, charging between the two battery banks.

Once you start the engine, the isolation relay, in that heavy cable, closes, effectively creating one larger battery bank from both batteries.

When the relay closes, the battery voltages equal out and the alternator senses this. That causes it to increases its output to get them all charged back up.

We dry camp often, while traveling between longer stays. We set up, use lights, watch TV and even run fans or heat if needed.
In the morning we use our electric coffee maker.

We get underway in the morning and by that afternoon, the batteries are charged and ready for the next night.

[Mark_K5LXP]

Wire gauge and alternator capacity notwithstanding, they don't charge house batteries as well as a multistage converter. Alternators are more about powering chassis equipment and restoring the small amount of energy in the chassis battery used for starting the engine. The alternator voltage profile does not charge storage batteries all that quickly. It will provide some useful number of Ah for sure, especially if they're low but it would be many hours of sustained driving to charge house batteries 100%. So it would be incorrect to say the alternator "doesn't" charge the house batteries but it would also be incorrect to say it's good at it.

Contrast this to a multistage converter powered by a generator or shore power. It will adjust it's voltage per the charging phase the battery requires, which is especially important during absorption for a complete charge. While a say, 55A converter doesn't sound as impressive as a 180A alternator, if you were to monitor the currents from each you would find the alternator supplied current tapered relatively quickly during the bulk phase where with the converter the current would be constant throughout that phase. Couple that with restoring through to a 100% charge and the converter from generator/shore wins out over alternator. Consider the alternator source a "supplement" and not a "substitute".

Mark B.
Albuquerque, NM