Chassis engine charging house batteries?

[Mitchmedford]

I have tried to read through a bunch of threads on this topic before posting, but I either can't seem to find the exact answer or I'm just not getting it.

I would like to know exactly how and when the alternator will assist in charging the house batteries on my 2017 DX3 BH.

I have the Xantrek system and when I use it to watch the battery status, I never see any charge going in when I have the truck idling and stuff putting a load on the house batteries. No shore or generator power, frig and main TV running on house batteries, start truck and let idle. Xantrek shows load on the house batteries, but nothing going in.

I realize that the batteries must not just be connected in parallel or when the house or chassis batteries get drained everything would be drained. This implies an active circuit that "decides" when to let the alternator charge the house batteries.

Can anyone explain the system to a newbie?

[Motorhome1]

Put a voltmeter across your batteries and step idle up to 1500 to 2000 Rpm. Battery voltage should start to read between 14 - 14.5 volts. Alternator does not alway charge at idle.

[formerFR]

yes, you should have a device installed, called a bird or bim, or similar name, that allows the Alternator output to reach the House batteries when the Chassis batteries have reached a certain level, such as 13.5 volts.
The reason you are not seeing anything on your readout, like my Magnum ME-RC panel, is that the alternator 12v power is not flowing thru your CHARGER, it is simply flowing directly to the battery bank, bypassing any sensors.... just like any solar charging would - you would only see it if you looked at the Solar Controller, not your Inverter panel.

With your CHARGER, it is designed to show you not only the Volts, but the 'status' of the Charging, such as 'BULK', or 'ABSORD', or 'FLOAT', etc., but any other charging to the batteries will not show. Your panel should only be reading 'INVERTING' or something similar, and the current 'load' status of the battery bank. As you travel, the volts should certainly start to inch higher, unless you are using quite a few items WHILE you are traveling, if then it should probably hold steady.

[KRedburn]

The alternator will not charge the batteries at idle. The draw to power up the frig is greater than the power output from the alternator --at idle.

I have found it best to run the gen set for an hour after arriving at a place when boondocking. This will "top off" the batteries prior to shut down for the night. By doing this I have had the batteries last all night running the frig and running heat from the aquahot.

The alternator will be providing power to the batteries while you are driving but will not necessarily be generating sufficient power to bring your batteries to peak charge with the inverter providing power to the frig. That is why I have found it best to run the gen for a bit to "top off" the batteries after arriving at a stopover.

[Mitchmedford]

Can anyone explain the mechanism by which the charging from the alternator is regulated to decided between chassis and house. I can't imagine that the alternator is always charging the house batteries. Something must be balancing the flow to chassis battery vs house.

[formerFR]

https://www.discoveryowners.com/bird.pdf

[Mitchmedford]

Very informative and sounds smart. Are you says that my DX3 has one of these? I have looked and not seen anything with the Intellitech logo on it that looks like this.

[formerFR]

BCLEMONS may be able to weigh in on the exact brand/model or device Dynamax uses... but they all are similar.

[Chuck_S]

Vehicle alternator is only designed to charge the starting battery and the voltage regulator will keep the charging voltage low to not overcharge it. The engine will usually keep the battery charged but bringing up from near dead takes a very long time.

Many emergency vehicles like ambulances (and many boats) have a second alternator to charge the house batteries efficiently. They're quite expensive compared to automobile alternators but sill charge very effectively.

-- Chuck

[bclemens]

BIRD

[Mitchmedford]

Thanks for docs Brian.

Where is it located on my 2017 DX3?

[bclemens]

Electrical bay

[Mitchmedford]

Thanks, I found it. It was hiding on the back wall behind a large clump of zip-tied wires. All green.

[Philkaty]

need this info also thanks

[bclemens]

Originally Posted by Philkaty

need this info also thanks

I'm not sure what info you need? But if I assume it is the BIRD location, and I assume that you still have the Forester that is in your signature, then that location would have to be given by the Forester division.

However, if I can assume it is still where it was when I was there, I am pretty sure we mounted it under the driver seat (or right behind the driver seat) on the floor of the chassis.

[Barch]

Where is the BIRD on the ISATA 3?

[bclemens]

Isata 3 doesn't use a BIRD, it is handled by the Battery Control Center. That is in the step-well.