I know many people are looking to do lithium conversions on Gems but maybe confused about how it all works . Lets try and explain a few things .
There are many different types of lithium battery chemistries . They all have different pluses and minuses and are used for different applications . The lithium battery in your phone and laptop is completely different from the kind you would use in a boat or a car , you would Never use this type of battery in a Gem or EV . The Lifepo4 chemistry you would use in a boat or car starting battery is completely different from what car manufactures use in EV’s . Most all Ev’s use one type ( except Tesla , theirs is different) . So When someone says lithium it doesn’t tell you anything . For the purpose of this I will focus on the 2 chemistries that would apply to use in a Gem .
First is LiFepo4(also known as LFP) . These are the square cells you see . (the green cells Inwo sold are these chemistries ) If you buy a drop in replacement for your car or boat they will be Lifepo4 chemistry . These are one of the safest chemistries available , They are thermally stable to 518 degrees . There are hundreds of Youtube videos of manufacturers putting nails thru them, shooting them , charging them to twice their max voltage . In almost all cases they smoke but don’t catch on fire .But heat them to 518 degrees and they will .
Many people consider them safer than a flooded lead battery . Try to charge a lead 12v battery to 24v and it will go boom . These are a consumer lithium battery and widely sold . No car maker uses these in an EV . The reason is low power density and voltage . They do not hold as much power for their size or weight as other lithium . And They have a lower voltage per cell so you need more of them for an application . These work great in a gem but you need 25 to 28 for a Gem . They require a lot of connections to make a pack so more possibilities of connection problems .
NMC (also known as NCM) This is the Chemistry Chevy , Nissan , Jaquar , BMW , Mercedes and every other manufacturer uses . Most of the batteries used in Gems come from one of the EV cars . They have evolved nicely over the last few years . The trick here is to get modules that can be configured to work well in Gems . You want 20 -24 cells in a Gem . So modules that come in 14 or 16 cells don’t work . You want a minimum of about 65h . This would match a set of gels for range . Smaller cells set up in a parallel/serial application can work but make for a difficult install and monitoring . If you are buying used cells you want to get ones that have been tested . All batteries lose capacity over time and lots will not be anywhere close to their once rated capacity . Nissan leaf cells are rated at 64ah new . Nissan considers them end of life at 80% capacity , under that they are removed from service . These are the thousands you see sold on Ebay . Most test about 70%, this means they are now 44ah . This can apply to any battery and explains why some people don’t get the results they are looking for . NMC is also considered a safe chemistry and is Thermally stable to 410 degrees .
Other things to know . Don’t charge any of them to 100% . All lithium lasts much longer if only charged to the low 90% range . If discharged lower than minimum voltage most will be permanently damaged . They may take a charge but will probably swell and will have diminished capacity . Always use a BMS . A good BMS will keep your cells balanced , won’t allow over charging and will disconnect your battery if voltage gets too low to protect it. A properly designed lithium conversion should give you years of service and be safe to operate .Any questions let me know .
Hi! I have a 2012 GEM e4 and I am considering converting to a 72v lithium. Would the existing charger work or would I need to also get a new charger?
Thanks in advance!!
It will work as-is with some caveats. It can also be reprogrammed for up to 98 volts.
Are you just looking for a no maintenance 20 mile battery?
Many of us are hotrodders and go for high performance and up to 100 mile range.
Figure roughly 150wh to 250wh per mile.
Your charger will need to be reprogrammed for lithium. Inwo or I can do it. One day turn around. Will need to know what type of lithium and how many cells.
Thanks! The 12v batteries I have now are still good so I want to get the life out if them first. However, the DeltaQ onboard charger seems to have gone bad. It flashes red 6 times and it’s not charging the batteries, which I know are still good (confirmed with a voltmeter and show 13.75v)
So because it seems I need a new charger, my preference would be to buy one now that works with my existing configuration but will also work at the point that I decide to go lithium.
I have multiple people that have done that. The versions I have are lithium programable. So we set them up for lead and then when they switch to lithium we just add the lithium profiles for their setup.
I have a 2009 GEM e2. I decided to replace my worn out gel batteries with lithium batteries. I purchased six (6) 12 volt LiFePo4 batteries each rated at 100AH. I installed them today and did a test run. Everything worked fine until I accelerated to top speed. As soon as I accelerated the 100A main disconnect tripped. I reset it but it continues to trip when I accelerate to top speed. Apparently, I am drawing too much amperage. Can you offer a solution? Thanks.
Premade LFP batteries have BMS’s in them. Usually they are small and only allow 100a-200a draw. If exceeded will trip breaker. Second problem is many premade 12v lithium batteries can only be hooked up 4 in series( we need 6) You need to contact seller and make sure they can be 6 in series and find out what maximum draw is. Which batteries are they?
I purchased two (2) sets of 36v Dakota Lithium batteries and wired them in series. Thanks LG and AR, I can only reply 3 times so I’m editing this response. The wiring to the new LiFePo4 batteries is exactly as it was for the original gel batteries. No wiring has been changed. When the breaker goes the entire GEM goes black. What does the 100A breaker protect?
The 100A breaker in the GEM tripped. I can reset it but it trips again upon acceleration. Is there a solution without returning the batteries? I can only reply 3 times here. The batteries seem to work fine but the 100A main (under the dash) trips when I accelerate. What is the 100A breaker protecting? If I increase it, what could be damaged?
It sounds like he is tripping the breaker on the bottom of the PSDM (under the fuse panel)
As LG said, the motor should not be going through that breaker. It sounds like some wires may have been switched around. Follow the wire from batt6(+) and it should go to one of the big connects on the Main Contactor relay. Then a cable should go from same connect to the 100A main breaker to supply the car.
Hey guys, thanks for your input. I was just granted full privileges to respond. Yes, the main 100A disconnect/breaker under the fuse panel is tripping with the new lithium batteries. All wiring has remained exactly the same i.e. original. I just received the wiring diagrams from Rodney and will continue to diagnose. Any help would be appreciated.
Thanks LG. I purchased two (2) 36V Dakota Lithium sets. Each set consists of three (3) 12V, 100AH batteries. I wired them in series to get 72V. Is there any kind of work around I can do to make this work?
There shouldn’t be a work around. It really is a fix. Batteries don’t seem to be the problem, The fact this is running thru the main 100a fuse is the problem. Maybe pictures would help where cables are connected. @Inwo is our resident genius when it comes to this. We are going to need some pictures.
Probably not the problem, but are they approved for 72v?
Assuming each has a bms, mosfets in each must be rated high enough for the total voltage. I’m not a fan of multiple bms, but if they say it will work it should be ok.
Do you mean the main disconnect switch trips. It’s not unusual for them to go bad.
To be honest, I don’t know if it’s a circuit breaker or a safety disconnect. If marked 100a it can’t be a breaker. It would trip all the time, unless it has a special long trip delay.
Good question. I am trying to get an answer from Dakota on the 72v approval. I did not ask in advance. There is no outward sign of a bms on the batteries. I will trace the wiring to see how the batteries connect to the controller, motor, and 100a disconnect and get back to you.
Hmm, specs say that it takes charging to reset bms, so thats not it.
The 200ah batteries are good for 400a peak. May be a good choice if the are approved for 6 in series.
I would still not recommend it. Hard enough to keep one battery balanced. 6 batteries sounds like a Pita.
Let’s see what they say.
