Hello, I’m new to the forum, and had questions about my 2002 gem car. I am looking to convert from the original 12v gel batteries and broken Zivian charger to lithium ion and a reprogrammed ride 4 fun charger. Now I heard of some people buying 72 volt batteries instead of the 12v and connecting them in parallel instead of series to gain more amp hours. I found a company which sells a drop in ready 72v that comes with their own charger and connects in parallel. The only down side is the price. I was wondering if I should buy the kit, or just go the conventional route and get 12volts in series, or just buy my own 72v batteries and connect them in parallel myself if possible. Thank you so much, any information and advice would be most helpful.
Run away.
Series, parallel all bad. By the correct battery for a 72v Gem and be done.
Search drop in lithium and avoid the same mistakes others have made.
@LithiumGods , @djgabriel2004 , and myself built custom Gem batteries for less money and easier install.
Is it an E2 or E4?
Where are you located?
I’m not the biggest fan of these “drop in” conversions… too many things that can fail.
Do you know which Chemistry are they using? If its LFP then Its a double nono for me. 
Hello, I believe the chemistry is lifepo4 with a 24s celI configuration. Yet I don’t know very much about chemistry though. Thank you very much for your reply.
It is a 2002 E825 and located in NY. Thank you very much for your reply. Honestly the whole idea of adding the extra voltage sounded kind of sketchy to me. Do you think I should just have ride 4 fun reprogram the charger and buy the 12volt lithium’s? Thanks again
Why do you ask?
See above.
R4F charger? Pay more for less!
If you are still looking for some sort of guidance,
I will ask you a return question:
What is the nature of this car?
(What will this car be to you?)
Well, then you might be in the wrong place. You are in the company of some of the sketchiest Gem Owners on the planet.
You have a choice. Are you going to take the Red pill, or the Blue one?
GEMs loooove extra voltage. Go faster. Go longer. It’s kind of like Cialis with a Red Bull chaser for golf carts.
Those pre-packed lithium batteries that look like lead acid batteries are meh. Not much range and can’t provide the kind of power (amps) a gem may draw on a launch or with a heavy load
Thank you for your reply. I think upgrading gems is pretty cool not sketchy. The 72v batteries though was the sketchy part, I’m glad @Inwo and @djgabriel2004 cleared that up for me. I want to upgrade to lithium ion, but just wanted to know a safe and conventional route. Again thank you for your help. 
I have a couple ready to go. Both use new Samsung SDI cells and 350a jk bms.
20s=73v $2650
21s=77v $2750
Delivered Fedex
Just to expand on this further, the problem with the multiple drop-in solutions is that each box has it’s own BMS and they are not talking to each other. They will charge and protect within their own container, but there are a a few scenarios that may provide unpredictable results when arranged in a large multiple pack scenario.
Not long ago, many of these companies did not recommend connecting more than 4 in series (not really a solution, just containing the odds of it being a problem), but I’m not sure if this has changed lately if they are changing their hardware/firmware.
In either case-
- 12v/high AH x 6 Batts in series to make Higher V (72v)
- 72v low Ah x 6 Batts in parallel to make higher Ah
you have a more complicated system than you may think. Each arrangement have their own points of failure and has a high possibility of becoming unbalanced without you knowing. Then eventually cascades into pack failure.
It is far better to install a pack designed as a single entity, controlled by a single BMS.
I think all the major manufacturers have even figured this out.
Maybe even these guys had it right too?
Hi,
New here. I have a 2002 Gem 825. Thinking of convertion to Lithium batteries from my Lead Acid. However my knowlegde in this area could fit in a thimbel, but I am hands on. I do the idea of one integrated BMS for all the batteries.
What charger would you use wth this system?
I talked w/ Ride-4-Fun and he told me not to reprogram the R-4-F super chager I enstalled several years ago, rather to go with the charger that comes with what ever lithium batteries I go with. Thus my question about a charger.
Using your set up is there a way to conect a LED readout to the dash showing battery charge level?
From the charger can I easily then connect into the controller on the GEM?
My plan is to also add the R-4-F 7.5 HP motor. Good idea?
I know most of this is probably pretty basis but I’ve been following alot of the conversations here and have seen the willingness of all the people posting to help those of us that do not have your expertise. So thnak you in advance!
There may be others out there where your input would help too.
Knowing I just read for so long without engaging, having a basic tutorial on the feasability of my paln would be appreciated.
Again thank you for giving of you time and knowledge.
Any charger, including R4F will work with my battery.
Yes, optional dash lcd or a $10 meter.
The only issue is fitting a one piece battery in an older Gem. The rest is an hour install. Connect two wires.
This is one standard size:
Thank you to everyone for their very helpful replies. Sorry I haven’t replied sooner, work recently got the best of me. Your information is very helpful and I’ll go over it and weigh my options (have to run it by my girl so she doesn’t get upset) Again thank you very much for all your help.
OK Thank you. The guy at R4F said I could send my charger in to reprogram but he would need the exact specs on the battties so the reprogram whould be right. Based on the mailing back and forth, his rebuild,and cost I think he felt it best to just go with the charger that comes with the batteries. I assumed he ment the charger that comes with somrthing like battle born or big battery, something like that where it is drop in ready.
Do you have a preference for a good charger?
What are the amp hours on your battery pack?
I just messure the battery location on the Gem undrer the rear seat. I see the challange for fit you noted. The Gem has two cross member supports of the frame angeling down in the battery mount box.
Thanks again for your input!
This probably is showing my ignorence but does the black portion in the cardboard box fit over the top of the battery pack itself? I assume that is the BMS.
The 2 connections you mentioned are the B- and B+. I just hook them up to the GEM -+ and everything operates as before.? Wow
That seems pretty straight forward.
What are the amp hours for the pack?
I like the fact that I would not have to change out my Super-charger from R4F, because it would charge your batteries.
I think I saw a pic in th forum of a GEM w/ these installed and they modified the rear cowling for a good battery fit.
Thnaks for your response in advance.
Barry
The complete battery with bms, black box, is shown in the box. Its all connected as shown.
Sometimes bms will be internal, but connects the same.
Connect to +&- that’s it.
The R$4 SuperCharger is northing more than a rebranded Quick Charge corp Select-A-Charge SCO7210. The F5 profile, which is the lithium profile, needs to be factory programmed because they want to set the max voltage to match the number of cells in your pack. F5 was originally intended for LiFePo4 cells, which only go to 3.6v / cell whereas the SDI cells are a different chemistry and go to 4.1v. It’s a brute force, old school, dumb as box of rocks, wound transformer based charger - I have no idea how F5 might interplay on a different lithium chemistry.
As @Inwo might have told you, you are probably better off with one of the lead profiles.
Now, I see you have Trojan XHS30 batteries in there. If configured correctly, this should put the charger on F3-d2. F3 is the 3-stage deep cycle program, and d2 lengthens the cycle and I believe raises the voltages. It’s the modifier for the “BIG” batteries: Trojans, Full River, US Battery for example.
You might need to change the “d” profile. Not sure if F should be changed to something like F2 (2-stage) or F4 (AGM - which on this charger has a flatter curve). - that’s a @Inwo or @LithiumGods question that I can’t answer.
Changing profiles is super easy, here’s the manual, and they also put a youtube video out. You power it up without the batteries connected and it goes into programming mode. Then its just pushing buttons on the front.
Here’s all the documentation that they scattered around their website:
- Operating manual:
https://www.quickcharge.com/standard%20portable%20chargers_htm_files/SCO%20charger%20Instructions.pdf - Tech product cut sheet:
https://www.quickcharge.com/standard%20portable%20chargers_htm_files/SCO%20lit..pdf - Charge curves for various profiles:
https://www.quickcharge.com/standard%20portable%20chargers_htm_files/charge%20curves.pdf - FAQ, they talk about F5 about 3/4 of the way down
Quick Charge Corp. Battery Chargers - Product page:
select-a-charge on board battery chargers
OMG! ^^^ Awesome info.
I… I…
I got nuthin’ like that!