I bought a used 4 seater GEM and the batteries are hilariously bloated and hosed due to Craigslist liars. Regardless, that’s not relevant to this, more of a warning to newcomers. (new battery doth not mean good battery). They kept enough of a charge to let me know the GEM does, in fact, turn on and lights up so there is that. Now the next step is to get new batteries.
Due to the one conversation thread about “why on earth do people still use lead acid or gel batteries?” as well as “lithium conversion for dummies” I am taking the plunge on going lithium immediately as well.
Lot’s of the information is spread out or confusing as a newcomer so for reference sake I thought it might be nice to do another guide and be sure to keep it updated as best I can. I have the info below as I know it and need clarification from you guys. I will update the bullet points once I know.
Batteries
I have purchased this 72v Volt pack that has been customized. If you go this route you will need an additional 6s 22v (sometimes called 24v) pack in order to keep the batteries in their butter zone.
You can also buy two of these instead which will put you at 96ish volts but we will fix that high voltage by using Inwos voltage spoof. (you can also run your headlights for a bit to bring the voltage down for testing sake)
It’s important to note however, the stock charger will not stop charging, it will jsut charge and charge and charge and charge until the battery explodes. You have to monitor it and stop at the correct voltage. Don’t be an dummy like me and overcharge the dookie out of your batteries the first day. This is dangerous.
It looks like this guy is popular to buy batteries from via ebay. He was quite nice to me.
Controller
I have a controller made in 06/04.2004. It appears to be a T3 due to the last 2 characters in the “catalog number” section of the controller tag. I am working with @Inwo to make it like my higher volatge needs using his single pin mod to trick the controller into letting us go faster. 30mph appears to the be the fastest the T3 controller will go, even with firmware flashes. You need to go to a T4 controller to break that hard limit.
Charger
I have 2 Delta-Q QuiQ chargers. The yellow ones. One is on board and one is external. No idea why, but hey, cool for me. @Inwo says he runs the stock QuiQ charger in the flood profile and things work fine.
C is for cookie, that’s good enough for me.
What QuiQ chargers are programmable?
Look at the first numbers of DQ.
DQCP with a black dot=good
DQCT or later=good
Earlier are not programmable.
Speed
The GEMS are hard limited via software at 25mph. I had the cart up on jackstands and felt it do some bucking or limiting at 25mph so I am grabbing a Magic Magnet from Inwo This seems pretty straighforward. It’s imposibly easy to install and well worth the money. The device tricks the speedo into thinking its a lower speed via some magical pixie wrangling.
BMS
It seems like most users here say they hooked up the BMS but the charger does a good job of keeping things in check. I’d like to do some monitoring to prevent my garage from turning into a fireball at 3am someday, so I will dig into this once I get my batteries installed.
Voltage Spoof
If your new batteries are giving you more voltage than the stock GEM can handle, (it needs to be in a specific range or your cart will not turn on) you can do a voltage spoof. This is how some of the users here are hotrodding their carts to go faster. I’ve read some of them can do burnouts.
The core issue is the controller needs to see a specifc range of volatge in order to turn on. If you are too high or too low, it will not work.
The best way to do this is to hit up the ever popular @Inwo and he can build the mod for you. I bought one and it was easy peasy to instrall. Get more info here.
Remember, this is slightly uncharted waters and could club the longevity of your motor, controller, license or life. These are low speed vehicles and if you are caught ripping around at 40+ mph your local police might be less than thrilled. Don’t be dumb.
On a related note, I have a youtube channel and plan on making this a long term project with many videos about upgrading, fixing, modifying and more.
These are rated 3.7v nominal per cells… there’s 18cells there… which make it 66.6v and 4.2v fully charged which make it 75.6v… So that’s why it’s refereed as a 72V.
Been there, done that.
Don’t trust anyone who sells a 66v as a 72v.
Minor difference! 6v is the difference between working and not working.
A gem won’t start below 68v.
So you will only be able to use 25% of the battery that you paid for.
Plus, charging over 4.1 lowers life of battery. More markedly in high temperatures.
Buy a 24s 88 volt module or another 6s 22v.
You can then wire for full voltage. (or more)
20s is absolute minimum.
One other thing.
Charging ?
Any 72v charger will over charge the hard limit of 4.2v 75.6 total.
And that’s with perfect balance.
Let me know where you’re at. Grant, Mike, and myself will help it go smooth.
Look at the first numbers of DQ.
DQCP with a black dot=good
DQCT or later=good
Earlier are not programmable.
If you run the correct battery, the stock charger does pretty well.
I run 22s in my Gem EL with charger set to flooded. It charges to >4v >88v total.
Buy 24s and tap it at 22s. Easy to do.
May need to leave the lights on to get down to 85v after a full charge, but there is a simple fix for that too.
Hope I don’t sound like a smart a**, but too many have went down this road.
Calling 12s 48v is a pet peeve of mine. It sells batteries, and gives disappointment.
Yes, that’s what I’d do. Start at 22 cells. that’s only 2 unused.
You can always go up or down.
I like a bms. If for nothing else, it lets you see each cell voltage at a glance. At a minimum get a $10 cell log that checks 6 or 8 at a time.
If you have those bought, buy another 22v 6s module.
I have been running 98 volts for a few months now. My apologies on not getting a good post up with pics. I ran 2 12-cell packs in parallel and then used them in series to get me to 4.1x24 volts. DQ charges up to 98 without a problem. I am using a BMS 24 management system to keep my cells in balance. I used a 15 volt spoof with may controller. I will try to get my post up soon. I bought my batteries from the guy in Chandler.
In my dummies thread I tapped one cell on each to bring the voltage down. I ended up untapping and using the full packs which would have been a little easier to start with. Now I’m also at about 98 volts with the voltage spoof. Works just fine.
I’m using the chargery charger system and the voltage spoof from Dave. Pulled my old charger completely out. I’m in the no BMS needed camp. Voltage solid…
Now we’re talking. Need more in open forum, so I’m not repeating myself.
I’ve learned more from these last posts, than last two years.
Generally no feedback.
I believe there are about 6 super-volters out there now.
1 failure that couldn’t get spoof to work in a t1 or t2.
Starting to think it was a ??? Controller.
Enough feedback now that if a controller blows up, I won’t feel responsible.
When I was the only one, though it might be a fluke.
Good call on running the full packs @ryan380golf. I don’t think I will be tapping mine when they come in.
Even if my batteries are charged too high I can run the headlights until I get within range for testing like @Inwo pointed out. “For testing purposes only” as the CarandCameras guys say.
Speaking of overvoltage, how do I get your voltage spoof @Inwo? I did some searching and I can’t tell if it’s a some reworking of the controller wires I cna do myuself or if it’s a breakout box you are selling.
