24V house batteries? - Page 2

Wowbagger · 01-01-2016, 03:54 PM

The alternator is programmable - so I should be able to set it for the 26.5V that the batteries want to charge to. The nice thing about LiMnFePO4 is that it has a very simple charge curve: up to 3C current (900A in my case) until you hit 26.5V, then hold 26.5V. The alternator will be the limiting factor.

tmblsn · 01-30-2019, 05:43 PM

Wowbagger,

This thread is quite old, but hopefully you can still respond. I'm in the early stages of design a SMB and I happened upon this thread when searching for RVs using the MSH4024M.

How is your rig's electrical system working out for you? Is it operating as you expected?

Wowbagger · 01-30-2019, 06:13 PM

More or less. I've had problems with the BMS battery control modules - one decided it wasn't going to talk, so I had to replace it - and since the version I had was no longer made (possibly due to the very problems I had) I had to replace all of them.

Also, I was unable to get the second alternator - that is only an option on the gasoline engine, not the diesel. Instead, I have a 1200W 12V to 24V DC-DC converter to charge the system from the 12VDC alternator, and a 24V to 12V converter to run the 12V loads from the house batteries. I wish I'd been able to catch that Sportsmobile didn't put in the 24V version of the Danhard AC and Espar heater, as that would have simplified things.

However, other than that, the system works well. The 1200W 12V to 24V DC-DC converter to charge the system does well. Not as well as a second alternator would do, and if I were to hear of a 2nd alternator kit for the diesel engine I'd jump on it in a heartbeat, but it does pretty well. And it is really nice to be able to run pretty much all the 120VAC loads in the rig without worrying about the inverter overloading.

tmblsn · 01-30-2019, 06:20 PM

Thanks.

I'm looking at the Sprinter, which does has a 24V alternator option. I will make a note that the Danhard and Espar units are available in 24V flavors.

Thanks again.

Wowbagger · 01-30-2019, 06:56 PM

Good to hear. Also, most LED lighting can run on 24V, as can the Norcold fridges (mine is set up for 24V). You can also get SureFlo water pumps in 24V (mine is) - if you can do that, you can keep almost all the "house" loads on 24V, and thus not worry so much about running the chassis starting battery down.

tmblsn · 01-30-2019, 07:35 PM

Interesting. I was thinking about completely separating the 12V chassis systems from the 24V house systems. The 1st alternator, which is 12V, would be strictly for the chassis and the 2nd alternator (24V) would be for the house.

Wowbagger · 01-30-2019, 07:48 PM

Yes, that's the way to do it if at all possible - you ALWAYS want to be able to start the engine.
However, if you go that way, don't forget to have some means to keep the 12V system topped up when on shore power, such as a 120VAC to 12VDC battery tender.

Wowbagger · 01-31-2019, 05:22 AM

FYI: I have a second set of batteries, like the first: 100aH LiMnFePO4 batteries, quantity 6, new in box, that I bought and now don't need. They need the control boards and BMS, but they have the connection hardware. Location Wichita, KS - anybody interested contact me via the board. US$3700 plus any shipping costs.