[TJ Clark]

Richard I apologize.

Apparently my ADHD didn't let me see the attachment or the last sustenance of that post.


My wiring was slightly different. (before I started fixing it)

All my batteries house and chassis are positive switched.

The positive from the house lands on the merge solenoid before going to the isolator.

I have 3 large positive conductors landing on the lower compartment fuse panel. It is likely that they use another 4/0 to go back to the rear compartment fuse panel.


I talked with Tom a few minutes ago. Helped me sort out the chaff from the real target.

His advise is to put the wiring back the way it was before the 8D's were removed. Install the lithium as if they are the old 8D's and disconnect the conductor to the isolator/merge solenoid.

[Richard]

No worries, just trying to help. I agree with Tom’s counsel.

When you get to a functioning coach, we can help fine tune some of the connections to give you features you want, and delete ones you don’t.

[TJ Clark]

No worries, just trying to help. I agree with Tom’s counsel.

When you get to a functioning coach, we can help fine tune some of the connections to give you features you want, and delete ones you don’t.

Thank you.

[TJ Clark]

A thought came to me at 3am today. When I hook it all back up as it was with the 8D's, how am I going to get the generator to start off the chassis batteries and not the house batteries?

[Richard]

So……….why is starting the gen off the house batteries an undesirable thing? Many LiPo manufacturers say not to use the LiPo as starting batteries. In this particular case, the starter load is very low. I have been starting my gen for 10 years off the house LiPo setup without a single issue.

You may have another reason.

[Jack Houpe]

On our coach all the house batteries are positive switched not ground switched also but overall the schematic of the wiring is correct. TJ what type of lithium batteries do you have? I assume they have a built in BMS?

[TJ Clark]

Yes the manufacture says not to use them as start batteries. They have internal BMS's and are rated at 250A continuous discharge. This link is to the batteries I have. LiTime 12V460Ah LiFePO4.

https://www.litime.com/products/litime-1...8wh-energy

Thanks.

[Richard]

You got me wondering, because honestly I never thought much about it.

I just went out and started my generator while watching the amp draw on the inverter panel. As best as I can tell it was just over 100 amps for just a blink plus the 10 amps I normally see when the batteries on float. I also put the clamp on ammeter on the batt cable at the house bank and registered 33 amps. I suspect the shunt on the battery monitoring system is more accurate and picked up the inrush current.

So if you have 3 of these cells (I think that is the number) then each cell BMS is going to see about 30 amps when cranking the gen. And if I read the literature correctly, each battery has 800 amps for 1 second on the BMS.

I am NOT trying to talk you into anything. Just providing data so you can make an informed decision.

If you do decide to cable back to the chassis battery side to crank the gen, PLEASE ensure that you do not inadvertently tie the chassis and house side together. There are two reasons. One your alternator may not like that. But more importantly. If you kill your house batteries you kill your chassis batteries at the same time, and have NO way of getting anything cranked to start the recharge process.

I personally like having the gen on the house batteries. If I goof and lose the chassis side, I can crank the gen, merge the banks, and eventually charge the chassis side enough to get going. I have had to do that twice when having an engine issue. If I kill the house side, then I can crank the engine, merge the batts long enough to crank the gen, and I am back in business. But this is personal preference. The same could be said for having the gen on the chassis batts. If you lose the chassis batts, merge, and crank the gen.

[TJ Clark]

Thanks Richard for running that test. I had been pondering that exact test since last night. In doing some simple googling of starter amp draw on small displacement engines I was finding 100-200 amps, on the high side. That had me thinking.... what you just posted.

Then when you and Jack asked your questions I had about made up my mind to give it a try.

I did not think about the amp load being distributed across all the cells. (6 by the way) Now that amp load starts getting to the insignificant range per BMS.

I appreciate and understand your cavate.

So really the only thing I need to do is remove the house system from the isolator, and be mindful of the merge switch. I think I'll paint it a bright color add a label to the dash to reminding me to pay attention.