RVs with DIY Lithium

[Txglader]

Getting some hardware mounted and cables ran. I hope to mount this in the RV tomorrow and get the BMS balance leads wired up and install the batteries. Next will be the inverter and AC wiring.

 

[corporate.joe]

Coming right along. Looking good.

 

[Txglader]

Coming right along. Looking good.

Thanks. Still a lot to do.

 

[Txglader]

Added a few more components.

Took the old lead acid batteries out.

I had to change a little of the existing wiring. Removed extra and bypassed the old disconnect. The landing gear for the 5th wheel and a couple other items are on a seperate system than the DC fuse panel. All wiring for it is now setup to work with the lithium batteries.

 

[Txglader]

Mounted the board with all the components in the RV. Test fitted the battery box.

Now to put all the cells in the battery box, connect the bus bars and BMS units.

Then I will need to connect the DC loads and mount the inverter/charger. Then connect the DC to it and wire up the AC side.

 

[Hedges]

I am not sure if one way is better than the other. Each battery positive will connect to one of the 100A fuses. The 400A will go to a disconnect switch. The switch is connected to a Victron Power In.

100A Mega fuses - interrupt rating is 2000A (at 32V)
They should be fine for an overload, but all bets are off if you get a dead short circuit.
I think lithium batteries can put out 20,000A into a short circuit. Class T fuses are rated to interrupt that.

https://www.littelfuse.com/~/media/automotive/datasheets/fuses/passenger-car-and-commercial-vehicle/bolt-down-fuses/littelfuse_mega_datasheet.pdf

 

[Txglader]

100A Mega fuses - interrupt rating is 2000A (at 32V)
They should be fine for an overload, but all bets are off if you get a dead short circuit.
I think lithium batteries can put out 20,000A into a short circuit. Class T fuses are rated to interrupt that.

https://www.littelfuse.com/~/media/automotive/datasheets/fuses/passenger-car-and-commercial-vehicle/bolt-down-fuses/littelfuse_mega_datasheet.pdf

I learned this after the fact. Through I would be fine as the Victron Distributer and Powen in is setup for MEGA fuses. The BMS units have short circuit protection, but I don't want to rely on them. I plan to chang it out.

 

[snoobler]

Hmm, in fact, that gives me an idea for a charge management mode - something like storage/excercise mode. I could call it Prius mode. Those cars like to charge their packs to a mere 80% for maximum life.
(It’s a very Toyota mentality. They are crazy about reliability.)

Speaking specifically to a Prius, they like to charge them to 55-60%. They will charge them up to 85% on a long downhill, but car will do everything it can to turn that charge into kinetic energy until it gets back down to 55-60%. They will sometimes spin the ICE w/o burning gas to bleed the HV battery down.

No point in having your kinetic energy recovery system so full it can't absorb any kinetic energy.

NiMH Chemistry starts to get inefficient above 70% SoC progressively worse to 100%.

That inefficiency manifests itself as heat and pressure.

All NiMH hybrids behave in a similar fashion.

 

[keithd]

Mounted the board with all the components in the RV. Test fitted the battery box.

Now to put all the cells in the battery box, connect the bus bars and BMS units.

Then I will need to connect the DC loads and mount the inverter/charger. Then connect the DC to it and wire up the AC side.
View attachment 43863

This looks really well done! Are you available for contract work??

 

[Txglader]

Would love to, but I don't think my current job would allow me the time to do it. It would have to be evenings and weekend, so it would take me a while to complete.

 

[Txglader]

Here is how the box goes together.
1. Empty box.
2. Side view.
3. Corner view. Can see the extended bottom which will hold it down when slid in place like a drawer.
4. Cells in box.
5. Boards inserted to hold down on cells. Notches to hold BMS board in place.
6. BMS board in place.
7. Boards inserted to hold BMS board in place.
8. Lid in place. I may not use this as it will only have about a 3/4" gap between it on the step above it.

 

[Txglader]

Installed the Bus bars, positive cables and BMS units connected to the negatives.