Going LiPoFe4 - Renogy Sale

[uthurricaner]

I've done some initial testing and disconnecting the ground control wire on the factory bim appears to be the ticket to disabling the engine charging to the lifepo4's.

The thing I was worried about is disrupting the disconnect relay interlocks. The way those guys work is you cannot operate them when the engine or generator is running, which makes sense as you don't want the engine or genset to shut down if someone where to accidentally turn them off. I have no idea how this interlock is accomplished thanks Winnebago's wonderful drawings, then again most rvs have no electrical drawings.

I'm going to install a pushbutton switch in place of a spare breaker hole to reconnect the emergency start switch. That switch just energies the bim relay that connects the batteries together. I'm pretty familiar with the whole operation at this point although I'm lacking some details due to a lack of info from the bim manufacture and Winnebago.
As always looking for input from others making this change as nothing is ever as easy as it seems.

Sam

[creativepart]

Can you post a photo of where you disconnect the wire... or take my photo above and show where that wire is on that photo?

[creativepart]

I'm thinking that I'll disconnect the positive feed cables to the battery (I have 3 of them) And see which one has 12v power when the engine is running. It may not even need to have the engine running. This should isolate the cable supplying charge current from the alternator.

Then, my thinking is... that I can connect that to the input on the DC2DC charger and then run the output from the charger to the battery bank.

One nice thing about the Victron is that it auto-senses that the engine is running and turns on and off via that auto-sense feature. No wire to the ignition is needed.

[uthurricaner]

That probably will not work because that cable also supplies power to the genset start and run. You have the inverter but I think your wiring is the same as mine according to Winnebago drawings. Here is the link to the bim manual https://www.precisioncircuitsinc.com...nager-RevF.pdf
You will see a pic of the device you want to disconnect the white wire labeled ground at the bottom left of the pic. The alternative to this is to install a diode on that wire which will not allow the charge but will allow the gen power. That was my original idea which did work but that's when I discovered the lifepo4's were still charging the chassis batteries due to that bim

Sam

[uthurricaner]

If you decide to disconnect relay ground do not try and undo the connection but rather trace the wire by pulling on it then cut it like 8" from the relay so it is easy to splice onto. Make darn sure you have the right white wire.

Sam

[DavidM]

Yes, I mistakenly confused powercat's Precision Circuits BIM as noted in his post #4 with Creativepart's BIM. It sounds like Creativepart has the older relay system and I agree that will be a bear to replace with the Precision Circuit Li-BIM 225.

FWIW I have the Precision Circuits BIM 160 in my 2021 Thor Axis and the Li-BIM 225 is a drop-in replacement which I assumed was the case for Creativepart.

Doing away with the relay based BIM and wiring in the DC2DC in its place is a possibility as uthurricaner suggest above.

But before I would do anything, I would measure the current from the chassis alternator to the coach batteries as currently wired with the new Li batteries well discharged. I am guessing that 50-75 amps continuously would be ok from a heavy truck alternator.

Also check the alternator case temp at low engine rpms which is the toughest duty for an alternator pulling lots of amps. If it stays below 200 F you should be ok.

David

[uthurricaner]

David, thanks for the correction. You would think they would have made the replacement bim a little closer to the original or provided an adapter kit. I hooked up one 100 amp 75% discharged lifepo4 and the alternator was charging at 80 amps so that pretty much indicated no direct connection was a good idea.

Sam

[creativepart]

Originally Posted by uthurricaner

That probably will not work because that cable also supplies power to the genset start and run.

I doubt that... my generator is started by my chassis battery. So, are my slides, my leveler and my TV elevator.

NOTE: Even though I do know it's my chassis battery that starts the gen, I don't know if I'm still not wrong about how best to accomplish this install.

[uthurricaner]

I just looked at the drawings for your rig and the house battery starts the gen unless someone has modified it. Use the chassis disconnect and see if the generator will still start. Everything else you mentioned should be run off the chassis battery with the exception of the tv elevator, see if that works with chassis connect off.

Sam

[creativepart]

Ok, wow, for some reason I firmly believed that the chassis battery started the genset. But rereading the Operator’s Manual it clearly states the the House batteries start the “120v generator.”

Thought I knew something I didn’t know.

[creativepart]

Sam... and others:

I found a great source of info on "drop in LiPo" batteries - well, it's in boats but still applies.

This is a long detailed overview of the systems and has tons of good information.

https://marinehowto.com/drop-in-life...ated-consumer/

In the section on DC to DC chargers I found this very interesting idea. The concept is: don't connect the D2D charger to the alternator but make the chassis battery the "source" charger. So, you disconnect the alternator from the House batteries and connect the D2D charger to the Chassis battery and then from there to the House bank.

So, the alternator charges the chassis battery, then the chassis battery sends current to the D2D charger and the charger sends charging to the House battery bank.

This protects the alternator and perfectly accommodates the D2D charger.

Here's a graphic:

[uthurricaner]

Yes , that will work fine provided you disconnect ground wire to the bim. As I said earlier the chassis battery charges through the factory ford wiring. Therefore if you disconnect the factory bim and connect the victron dc to dc charger from the chassis battery to the house battery you will solve the house battery charging, but you will no longer have the chassis battery being charged from inverter or converter. I'm still working on that minor detail.

Sam

[uthurricaner]

Here is a pic of the bim.

[creativepart]

This has turned out to be more complex than I planned - due to the BIM and the multiple roles it plays in charging house and chassis batteries and starting Generator.

I don't need to rush this. I have the batteries, purchased on sale at a good price. I have them connected in Parallel in my garage and fully charged. The batteries in my RV are still good. So, even though I'd love to rush and get these installed I need to do a lot more research and speak to more people.

[DavidM]

Yes, iinstalling a DC to DC charger is complex, particularly when you want to maintain all of the functions of the BIM.

If I were doing this I would replace that relay with the DC to DC charger. I would then rig up either a manual switch to bypass the DC2DC or a relay remotely operated to do it. This would give me the capability of charging the chassis battery from the coach which is useful for storage as well as combining the two battery systems for aux starting.

David

[creativepart]

Thanks David. Lots to consider.

If I put a rotary cutoff in the battery compartment - after the BIM - just before the battery bank I'm wondering if I could turn off alternator charging while driving but when parked turn the connection back on to allow the BIM to charge the chassis battery as needed???

I don't know what that would do to generator starting. Perhaps I could rewire that to the Chassis battery???

OR... instead of a Cutoff, I could have a high amperage rotary 3-pole selector - right D2D charger on, middle all off, left Alternator on??? The D2D Charger would be connected to the Chassis battery as Source.

[DavidM]

Originally Posted by creativepart

If I put a rotary cutoff in the battery compartment - after the BIM - just before the battery bank I'm wondering if I could turn off alternator charging while driving but when parked turn the connection back on to allow the BIM to charge the chassis battery as needed???

That would work to protect the alternator since with the switch off no current would flow from the alternator to the coach batteries. With the switch on it is back to normal.

Certainly, the cheapest and easiest- no DC2DC charger required, but no coach charging either from the chassis alternator. I don't see any other downsides.

David

[creativepart]

Originally Posted by DavidM

I don't see any other downsides.

Generator starting on the road could be a problem. I'd probably have to relocate that to the Chassis battery???

[uthurricaner]

Here is the drawing of my battery circuit and I believe it is the same as creativepart's RV. One source of confusion might be what Winnebago is calling the auxiliary start solenoid is actually the bim which is just a relay with some electronics that one of its functions is an auxiliary start solenoid. It also charges both the chassis and the coach batteries.

[uthurricaner]

BIM Wiring Diagram