Converting from a lead-acid system to LiFePo

[A-Stensen]

Pardon me if this has been covered before, but there's a lot of stuff here to fish through, a lot of it far more technical than I need or understand.

So, here I am with an 8 year old system in my van — a 270W panel putting out 38V, a TriStar MPPT 45 controller and two 12V, 104Ah AGMs. The batteries are approaching end of life.

If I changed to LFP batteries, would I need to get a different charge controller? And what other bits would I need?

 

[JMc]

Check the owners manual, maybe the Tristar has a setting for lithium batteries.

 

[chrisski]

Even with the lithium setting on a SCC you need to be careful. I charge mine at 13.8 absorption. Much higher voltage than that can wear on cells. I’ve seen SCCs with 14.3 lithium settings and I think that’s way to high.

 

[A-Stensen]

Okay, I found this on the MorningStar site. The controller can be reprogrammed — if you know what you're doing, which I don't. Looks like my life will be easier (and cheaper) (and heavier) if I stick with lead-acid.

Solar Charge Controllers for Lithium Ion & LiPo4 Batteries

Lithium batteries are gaining popularity in off-grid aplications. Learn about charging lithium iron phosphate (LiPO4) & other lithium ion batteries with our solar charge controllers.

www.morningstarcorp.com

 

[Rednecktek]

The other option is to replace your MPPT controller with a more modern one that has Lith settings pre-programmed or is just easier to reconfigure for Lith batteries. There are whole threads here about what settings to use for the batteries and there are usually only 3 things you have to change in the MPPT controller to dial everything in.

Looking at that link they make it WWAAYY overcomplicated to make Lith work with their stuff. Even a basic EPEver would be a good option. Hell, even my super-cheap PowMr units are just "Go to setting X, press enter, press up/down until Y-Volts, press enter", do that 3 times and done.

The worst case scenario, as I understand it (and feel free to correct me) is that if you don't change the settings from AGM to Lith you'll just never qquuuiiitteee get the Lith batteries up to full charge.

 

[MisterSandals]

Okay, I found this on the MorningStar site. The controller can be reprogrammed — if you know what you're doing, which I don't. Looks like my life will be easier (and cheaper) (and heavier) if I stick with lead-acid.

Solar Charge Controllers for Lithium Ion & LiPo4 Batteries

Lithium batteries are gaining popularity in off-grid aplications. Learn about charging lithium iron phosphate (LiPO4) & other lithium ion batteries with our solar charge controllers.

www.morningstarcorp.com

I have an 11 year old Tristar MPPT 45 and did the firmware update. There is a document which details setting a custom charge profile that works great with LiFePO4 batteries.

You can start by downloading MSView from the Morningstar site onto a PC (yeah, PC’s suk).
You can probably find the new firmware too online. I can send you the document that tell what settings to change (takes just a couple minutes).

The trick connecting to the Tristar is that it probably requires a db9 serial connector.

It’s a great SCC as you already know and it’s got a lot of life left in it for your lithium future.