IDEA...charging house battery(set) underway.

wwest wrote:

landyacht318 wrote:
A problem with this is the cabling used between alternator and battery by the vehicle manufacturer, and why I suspect higher RPM's made no difference in BFL13's case. This cabling is not adequate to pass high currents for long, It was designed to be just adequate for the briefly lasting loads expected by the stock systems and a battery which never goes below 90% and can never ask for much. The bean counters won again.

This can be negated with a fatter cable between alternator and battery. I've done this, just adding a parallel circuit and the amperage increase is close to 60% when the house battery(s) are depleted and the RPM's are there.

"when the house batterys are depleted" is exactly when you are most likely to boil electrolyte away due to UNLIMITED "underway" charge currents!

I just have this pecky 13.7 volt issue where my engine computer located voltage regulator will randomly decide that 13.7 is fine and dandy, even when the batteries are crying for 14.8v.

Puzzling...I am under the impression that the VR (limited by engine RPM) determines alternator voltage output. On the other the major shortcoming of the chassis battery charging system is that it does not limit the voltage charging level once the CHASSIS battery is almost fully charged. Maybe yours does which results in not being able to EVER fully charge the house batterys.

Using an INverter on the engine battery to power a regular battery charger is Standard procedure In Australia, especially when the 'caravan' is towed and quite a distance from the alternator.

My alternator, rated at 130 amps can barely make 32 amps at hot Idle, so If I were to employ this system, I would be robbing peter to pay paul whenever idling.

Not suggesting that "hot idle" or any level of idle be relied upon to charge house batterys via ANY method.

I disagree. (with your reply in bold print to what I wrote) If the house batteries are depleted and the alternator is blasting everything it can make at a given rpm, they are not going to start gassing until the ~80% charged level, at which point the VR is likely going to limit voltage, and thus the alternator's output required to hold that voltage.

I dont think you will find many threads about an alternator overcharging batteries. Not with Stock systems. The bean counters and the lawyers pretty much dictate that the charging systems are limited so as to not overcharge a battery, lest it become dangerous and set other lawyers and a lawsuit happy public out on the warpath for free money.