BMS with inverter/charger

[hermanr]

Off-Grid system - no grid at all.

I have an AIMS 6kw split phase inverter/charger, currently, it is in AC priority mode and I have a 10kw generator into the AIMS. The battery bank is 14s Nissan Leaf pack, no BMS today. Today I monitor voltage and shut everything down when not in use but soon we will have our tiny home completed and the system will need to be on 24/7 so the following upgrades are taking place and then the question I have. Moving to a 14s6p Ford Energi pack, Chargery BMS16t with a contactor to shut off main (inverter side) for Undervoltage. Midnite has done a great job to not overcharge above my set parameters but will monitor and can add another contactor or relay to shut the panels off in that case.

Question is, is anyone using an inverter to charge the pack as needed via the Genset? Right now my concern is winter when we drop solar generation and can go 3-5 days not having good sun. I seen a lot of folks using a portable Lithium-ion charger and just plug it into the Genset and connect to the battery bank directly but in my case, I have the Genset wired into the built-in transfer switch of the AIMs so it feeds my AC panel and charges at the same time. Makes it really simple for the wife to monitor and will allow me to make that an automatic occurrence in the future (auto Genset start via a set parameter on the BMS or even the AIMs has a set point)

Another reason for this question is again this is also my shop so when I need to run larger equipment such as the welder, planner, table saw, etc. I just fire up the Genset, go to town for that window and power off. No other interaction is needed. That is also why the big inverter, to handle the shop loads, not the tiny home but they are built together so one system for both was most cost-effective.

Thanks!

[Mike90250]

Whatever your charging source is, it has to be able to throttle back to preserve the battery, I don't know how flexible the AIMS is. Most inverter chargers have highly efficient chargers, and will be faster than a plug-in charger. I could charge 90A @ 48v but my generator can't handle that. No plug in chargers would be able to do more than 35A @ 48V

And you need a BMS to prevent charging when the batteries are at freezing (Li only) - if charging from the AIMS or Midnight, you have to reduce amps at 40F, and prevent charging at 33F (Did your battery vendor forget to tell you about the cool restrictions for charging Li batteries ? )

[hermanr]

Thanks Mike90250, I'm aware and they are in an insulated box in winter months to help with that. The AIM's charging is adjustable and max's out at 60a I believe and all the way down to about 10a on the low side. My GenSet can handle the 60 at times with no other load but I typically keep it about 25/30a on the dial.

[Ampster]

...........
And you need a BMS to prevent charging when the batteries are at freezing (Li only) - if charging from the AIMS or Midnight, you have to reduce amps at 40F, and prevent charging at 33F (Did your battery vendor forget to tell you about the cool restrictions for charging Li batteries ? )

Mike has a good point about temperature. I have used some Chargery products and they seem to be limited to RC applications with no control over charging parameters related to temperature. I don't know what your investment is in your used Ford Energi pack but if it is significant you may want to invest in a more robust Battery Management System to protect your investment. I have used an Orion Jr on a Nissan Leaf 14s pack with good luck. There are several other good ones available at less than $500.