I did a little test this morning, relative to input loads and with not stressing the vehicle Alternator.
BACKGROUND
The 4x4 has a 185A ignition switched solenoid under the hood, which powers 3 circuits. One, is an Anderson plug on the rear bumper to power a 25A DC-DC charger in the Caravan (RV) for the 2 x 100Ah LFP house batteries @ 40A fuse. Two, is a 30A fused power source for the RV Anti Sway system, also on the rear bumper, also Anderson.
The third is in relation to this post; There is a cable run from the solenoid to inside the 4x4 wagon rear storage space. It powers a 75Ah LFP slimline battery fastened to the side of the single storage drawer. Also 40A fused.
This is my Auxiliary battery and hereto referred as AUX BAT. It also has an inbuilt 20A DC-DC charger.
Note - When IGN is off all power to these 3 circuits is electrically disconnected from the start battery.
The fuses are around 15cm (6") from the solenoid and it’s input is also fused between it and the start battery.
Although I could run the Charger1 (C1) cable to the start battery, I already have enough connected to it.
The primary reason for the following setup is, my current loads on the Alternator are already at 45A, plus whatever the antisway will use if activated. I also have a light bar on the bull bar (roo bar) that the vehicle system powers.
My thought was that if I run the C1 from the AUX BAT, there will be little added load on the alternator if C1 is set to a similar load as AUX BAT charging.
I also wanted to set the C1 voltage at 35V to ensure the full 10A of output went into the power station.
As I already have a heavy gauge short cable (60A fused) to the AUX BAT to power a 375W Victron Inverter, using an Anderson plug to connect it, I used this source for the C1. I also made up a 30cm heavy gauge cable with Anderson on one end and into the C1 input the other. So, very short cable lengths compared to the C1 OEM cable. (Prior to buying the C1, this inverter was and still could be used, to charge both AC70 & AC180 PS in Silent mode charge setting.)
As the System is using a Victron Smart Shunt, I can monitor the AUX BAT as well as using the Bluetti App to see what the C1 is doing. The test unit was an AC70 at around 60% SOC.
(Above) This is engine ON (idling) and shows a positive value of 2.24A.
What does this mean? - The AUX BAT was at 13.1V and 100% SOC with engine off and 13.82V with engine on. Therefore, the AUX BAT is powering C1 and being charged at 2.24A or 31W.
Not done or noted in this test is; I also have an Engel 40lt fridge/freezer that is normally running in the rear at around 3A load.
It may be said that there is no auto disconnect, in other words, C1 will continue to charge after engine off occurs and until it senses a low voltage. But, the AUX BAT capacity exceeds that of the AC70. In the instance of my AC180, yes it will run AUX BAT to empty before fully charging, with engine off.
On the bright side, my use of either power station is generally less than 25% of capacity, but will still require monitoring and managing.
CONCLUSION
With the C1 settings noted, there is very little change to existing alternator loads, which is better for its longevity. However, as total charging has increased in Wh, it also means driving further for longer.
On a recent trip, I noted AUX BAT was at approx 30 SOC and my planned driving was a short trip. I overcame this by - Most of it was at 100kph (60 odd MPH) so, I drove at 60kph or just over half the speed. I still covered the same distance, but it took longer. Something to consider. When out camping, I do a fair amount of off road and rugged driving, so speed is not an issue, or time. Getting back in one piece, me and the 4by are, lol.
