I’ve given up on AGM batteries in my GEMs. I currently have a 2016 and a 2024 with a pair of 48 volt 100Ah batteries in each of them connected in parallel. It gives me almost 80 miles of range but I live on an island that’s about 7 miles long so I probably shouldn’t be putting it on charge every night when I still have 80% capacity remaining. I know the AGMs wanted to be topped off every night but I’m not sure about these batteries. There are EV chargers at the restaurants and beaches here so my question is, should I just use the local charge points when I go out to eat and shop and not worry about topping off at home every night? I realize the BMS protects the batteries from overcharging but I cringe when I see the cells top out at 3.68v when I think 3.65v is full. Seems the batteries would be better off with occasional charging and keeping it midrange as long as the cells stay balanced.
Thoughts?
I would cringe too! That does sound a little high.
What charger are you using and is it set for this battery?
What settings do you have in the BMS? Perhaps they should be reviewed?
What does the maker of your battery say about this?
The 2016 has the original Delta Q charger and the car BMS is programmed for an AGM distance pack. I’ve got about a year and a half on those batteries and they’re doing great. Lasting longer than the stock AGMs and a lot less money. ($759 times 2).
The 2024 has the original Lester charger and this car comes with an Acuity battery monitor. I’m able to adjust some limited battery settings so that the car SOC matches the battery SOC so everything works like original. That charger also thinks it’s charging AGMs.
The batteries are rated as 51.2v with a 58.4 charging voltage. The stock chargers seem to agree with this and I assume that the battery BMS must kick in to end the charging when it’s full.
They seem to charge at 54 volts for most of the cycle and only get to 58.4 volts at the end for 4 or 5 minutes and the cells climb from 3.50 to 3.65 pretty quickly with little amperage.
The only other important specs I was paying attention to were 200amp continuous discharge (times 2 is plenty for any GEM).
I can’t imagine this setup isn’t getting a little more popular so I’m wondering how it’s working out for others.
I watched this real scientific sounding guy that had done a lot of studies on the chemistry and he said to charge them to 3.46. so that’s what I set my BMS to. I’m using a solar panel to charge mine I’m in Arizona so it trickle charges all day.
You are better off not topping them off all the time. I charge mine once a week or so. I let mine get to 20-30% and then charge. Lithium hates being stored fully charged
So when you charge them, do you go all the way? And how high do the cells go to? Are you using stock charger?
My E4 sits around sometimes for weeks so I keep it around 50%.
The E2 is out every day. I plug in at the free EV charging stations when we go out to eat or to the beach. I’m just thinking of never topping off again unless I ever see a cell get out of balance.
I’m still tinkering with the Acuity unit to see if I can prevent the Lester charger from straying a bit above the 58.4 mark.
2024 E4. I run a performance setup. 63v 310ah. Set the lester to charge higher. In you case dont worry about it getting to 58+ volts. Lester does a low amp equalization charge when finishing. Won’t hurt your batteries at all. The key for you is not getting them that high all the time .LFP cells only come out of balance at the very top end or bottom end, shouldn’t be an issue. Charge them when they got to 50% or less. At that rate they will have thousands of life cycles and will wear out from age before cycling out.
Thanks. My plan going forward will be occasional charging and just keeping it in the middle. Not too high and not too low. Don’t think I’ll ever miss lead batteries.