SpinnerUp

The truck/onboard charging system never sees the charger and it doesn't output anything back to the truck. It accepts whatever voltage 's on the wire and modifies it on the fly to fit the house/aux battery charge curve. AGM's don't off gas when charging unless you really pour the voltage to them. I prefer to not have flooded batteries bubbling normally inside the van. If they gas off they're ruined because there's no way to refill the electrolyte.

mountainmanjoe

Of course the system 'sees' the charger. You can't get something for nothing (in this case higher voltage on the charger output). The charger will be loading down the entire system, which causes the voltage to sag. Especially if the starting battery is low. The voltage is measured, and the alternator will be commanded to compensate. Also, if alternator output is insufficient, then your charger will start to run down the starting battery as well, which the van is able to directly measure. The charger is a load that the system cannot 'manage' so they may end up fighting. Maybe it will be fine. Hope you post your results because I'm curious to know.

I'm curious also, where do you plan to connect your house batteries to the rest of the system?

Flooded deep cycle batteries always have watering caps for maintenance, so no they're not ruined. They are usually filled with a bit of extra electrolyte for reserve, and in my auto experience they haven't needed any topping up. That may be different in warmer climates though.

From battery university.
"Charging batteries in living quarters should be safe, and this also applies to lead acid. Lead acid produces some hydrogen gas but the amount is minimal when charged correctly."

SpinnerUp

I wasn't clear, if the AGM's pop the vents and off gas you can't refill them. Flooded lead can off gas all they want and you can refill them. You only quoted part of the BU article 703, the next paragraph about hydrogen sulfide is certainly informative. Things don't always work as they should, I'll err on the side of safety. Flooded lead acid can off gas all they want, just dump some preferably distilled water in them. I don't want them gassing into the environment I Iive in though.

The dc-dc charger takes current at the voltage provided by the truck system, the charger connects to the aux batteries and the camper systems ground to chassis. Read about one system here:

https://redarcelectronics.com/produc...attery_charger

Everyone on the internet has an opinion, I'm fully aware. These systems work as advertised, are not some off the wall, something for nothing product.

I just wanted a simple question responded to, but appreciate your interest and time.

mountainmanjoe

What I meant was, where are you going to connect the charger's input? Directly to the chassis battery or alternator etc..