Lithium Batteries

[msmith1199]

Just downsized from a Class A DP to a Class B+. I got the residential fridge in the new motorhome so power when off the grid is going to be more of an issue that it was before. I’ve been looking at Lithium batteries and they look like a good solution for me. Only problem I see is physical size. The two current batteries I have are 11.5 inches long and they are a tight fit in the battery compartment. All the lithium batteries I’ve seen are at least 12.5” or longer. So they won’t fit in the existing battery compartment without modifications. But those are all 100AH batteries. I see they also have 200AH lithium batteries. They are a lot longer, over 20 inches, but one of those batteries will fit in the compartment versus two 200AH batteries. So not only does the 200AH battery have a smaller footprint than two 100AH batteries, they are also quite a bit cheaper than buying two 100Ah batteries.

Anybody see any issues in going with one 200ah battery versus two 100ah batteries?

[FWC]

I think it is the other way around, an LiFePO4 battery will actually (slightly) charge the the starting battery, and draw itself down if left connected to the tow vehicle. The LiFePO4 sits at 13.2 - 13.3V, compared to 12.6 - 12.8V for the lead acid starting battery. As a result there might be a small current that flows to the truck battery, and any parasitic loads from the truck will be carried by the lithium battery.

[01tundra]

pianotuna wrote:
I think the issue is over voltage to the LI battery bank, not protection of the alternator.

LI batteries have been known to burn up some alternators due to the high charging demand, they've also been known to draw down tow vehicle batteries due to the higher resting voltage of LiFePO4 vs LA, if left hooked up with the engine off with a constant hot charge wire.

There is no overvoltage worries due to the voltage drop on inadequate factory wiring for charging purposes. If you upgraded you wiring such that you could get higher than 14.6V at the batteries then the BMS would kick in on high voltage.

For MY application the DC charger is there to actually provide enough amps to charge the batteries while running and isolation from the TV when the engine is off.

DC chargers have many benefits and one is absolutely protecting the alternator -

https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/

[pianotuna]

I think the issue is over voltage to the LI battery bank, not protection of the alternator.

[01tundra]

I'm running a Victron Orion 12/12-18 DC-DC charger with a dedicated 4AWG charging circuit from the truck. I get 25A out of it at peak charging and don't have to worry about the truck's alternator voltage fluctuation or it being harmed.

The charger has settings that allow it to sense alternator current to automatically start/stop to prevent the trailer LiFePO4 batteries from drawing down the truck lead acid batteries when the engine is off.

[BFL13]

Going around in circles here 🙂 This came up earlier and explains it all for DC-DC and some good diagrams. Just get your guy to do which applies to yours. The MH builder is behind the times it seems.

https://shop.pkys.com/Alternator-Lithium-Battery.html

[msmith1199]

Okay, for the latest. I contacted an installer recommended by the battery company. He told me since my motorhome was so new I may already have a DC to DC converter in it and he suggested a contact the motorhome builder to see. So I contacted my motorhome builder to see if they had already installed a DC to DC converter and told them what I was trying to do. This is their reply to me:

Mark,

A DC / DC regulator / converter is unnecessary to use lithium ion batteries on the house side, our BIRD (bi-directional relay/ delay ) already serves that purpose. There should not be any modifications necessary to use lithium ion batteries on the house side.


So I called the tech at the Battery Manufacturer and told them about this BIRD thing, and they disagree that it will replace the the DC to DC converter. So now I have no idea what to do! Any ideas? I do have an appointment to meet with the installer on Thursday and I’ll see what he has to say.

[steveh27]

Hope this works for the 4 pages of battery specs:









Thanks for the help.

[msmith1199]

steveh27 wrote:
Here's a site I found:

https://shop.pkys.com/Alternator-Lithium-Battery.html

The info in this article is pretty much exactly what the techs at Battleborn batteries told me. And I have purchased the DC to DC converter. Now just a matter of finding someone to install it. Everybody around here is booked and I don’t have the knowledge to install it myself. It looks easy but it needs to be installed and the old wires need to be disconnected. Hopefully the old wires can be used on the DC to DC converter so new wiring doesn’t have to be run throughout the motorhome. But that’s all above my pay grade. I don’t even change my own oil!

[BFL13]

steveh27 wrote:
need to learn again about posting jpgs. DO I need to have them on some other online site first?

http://photoposting.is-great.net/?i=2

[steveh27]

need to learn again about posting jpgs. DO I need to have them on some other online site first?

[pianotuna]

Steveh27,

The LI are fine.

The wiring is also fine.

The alternator needs to have a duty cycle that will accommodate 50 amps continuous. Research the make and model of alternator.

[Itinerant1]

No it didn't work. Take a screen shot and post as a picture. Or use a free pfd uploading host site, it will give options on how you want to post it in a thread.

[steveh27]

I think my 2 100AH LiFePo4 batteries are ok. I have not used them yet other than on 2 day trips due to my health. My alternator has a max capacity of 117 amps. It connects via #8 wire through 2 40 amp mini breakers to a battery isolator and then to the house batteries. I am attaching the specs for those batteries including the BMS protection, not sure if it will come. I hope you guys can confirm I am OK.

I do not know how to change this pdf file to a jpg I can attach. I could scan it into my pc then attach.
file:///C:/Users/Steve/Downloads/12V100Ah%20with%20BMS%20specs.pdf

It says max continuous charge current is 50 amps, and the max charge current is 60 amps or less.

[pianotuna]

I guess it depends now the ecu is adjusted? Are they adjustable?