Michael Janke

A couple electrical-related things happened on our September 2020 trip. The result is ‘Camper Electrical Version 4’. 😁

1. Our OEM WFCO battery charger/converter failed, which meant that we could not charge our batteries even if we were plugged into an electric outlet. I bought an inexpensive automotive charger to use to top off the AGM batteries if we were camped in an electric spot and relied on the engine/alternator to keep the lithium batteries charged. The OEM WFCO converter was a pretty dumb device & will not be missed.
2. We figured out that because of the way that the OEM chassis/coach battery interfaced worked, we had to have slightly discharged AGM batteries in order to reliably charge the lithium batteries from the alternator. That meant flip-flopping between batteries to get the AGM discharged before starting out in the morning.
3. Relying on the engine/alternator to charge the lithium batteries works great. Charging the AGM directly from the alternator doesn’t work so well. The AGM’s need a specific charge profile and temperature compensation – neither of which are supplied by the OEM battery interface.
4. A few months ago I installed a Schottky diode based device between the battery banks to see if it would be useful for using power from the lithium batteries to charge the AGM’s. But after testing it this summer I decided it didn’t add value.
5. I’m tired of the non-configurable OEM 12.2V battery disconnect. The low voltage disconnect should be configurable and should automatically reconnect if it sees normal battery voltage. The OEM disconnect does neither.

Having to buy and charger/converter and low voltage disconnect anyway, and not being satisfied with current state in general, a redesign made sense. Using what we’ve learned the last couple years, I wanted to focus on using the alternator as a charge source and try to keep things simpler overall. Not sure if the latter is true or not.

Constraints

The design is constrained by the assumption that there will be times when I cannot use the lithium batteries. They cannot be charged below 32F nor discharged or stored below -4F. Even though I have a battery heater, I want the camper to function with the lithium battery disconnected or removed.

I also need the AGM’s to start the generator. The lithiums are not suitable for that. I’m really temped to eliminate the on-board Onan generator. It’s heavy, noisy, and unused. But I’m thinking that if we sell this thing I’d have to re-install it, something that would be pretty painful. Maybe the next iteration.

Space is also extremely restricted. There simply is no usable, accessible space for any new equipment, especially wall mounted. Much time was spent re-arranging and re-wiring existing electrical to make space for the new stuff.

Version 4

I spent the last few days undoing most of both the OEM and what I’d done the last couple years. Here’s where I ended up:

The new charger/converter is a 30 amp Victron Blue Smart IP-22. It has Bluetooth and can be configured with custom charge profiles. It’s relatively inexpensive for a configurable Bluetooth-enabled charger. I installed it so that it always charges the battery bank from which we’re currently running.

The problem of getting the AGM batteries properly charged using the alternator is addressed by a Victron Orion-TR 18 amp DC-DC charger. It can use either the alternator or the lithium batteries as a charge source (selectable with an A/B switch) and has Bluetooth & custom charge profiles.

The low voltage disconnect is now a configurable, Bluetooth enabled Victron Smart Battery Protect.

In the prior iteration I had the ability to switch either set of solar panels to either battery bank. Now they are all tied to a single A/B switch and always charge the same bank. I’ll likely use the solar to charge the lithium battery depend on the DC-DC charger to keep the AGM charged via the lithium’s.

I gave up the ability to use the camper AGM batteries to automatically keep the chassis battery charged, as supplied by the OEM battery interface. If the camper is parked for long periods of time I’ll have to attach a trickle charger to the chassis batteries. I can live with that.

Some of the in-line fuses that I used in prior iterations were replaced with a fuse block. I don’t have space for completely replacing all of the inline fuses though.

Operation

The alternator charges the lithium battery via the Redarc DC-DC charger and the AGM’s via the B2B A/B switch and Victron DC-DC (B2B) charger. The Transit alternator has adequate capacity to charge both simultaneously. The Victron DC-DC can also use the lithium battery as a charge source via the B2B A/B switch.

The solar can charge either lithium or AGM depending on position of solar A/B switch.

The Victron IP-22 charger/converter charges whichever bank is currently supplying the camper load, selectable via the load A/B switch.

We’ll see how this version works.

Edit (2022-07-23): I’m on Version 5. Current configuration and related post