My first post here.
I think there are a few here that can give me an educated direction to go in.
I just purchas mt first Gem.
2015 e4.
Batteries are dead.
I have some LFP prismatic cells i could put in.
And i have some excellent gen 1 nissan leaf cells. And some gen 1 leaf cells at 66% soh.
I also have two Rivian modules at a nominal voltage of 44v
Can i drop these in or does something need to be reprogramed? Or a different controller? Different charger
Thanks…
Hi Timf
Welcome to the group.
You are standing at the door that leads to an exciting new world.
Yes, Most people in here have been where you stand now. If you want to continue on your present path you can follow much of the process and mayhem through the posts in the archives. Feel free to use the search tool in the upper right of your screen and enter various keywords related to your project. The archives can be a great learning tool and a fantastic look back on where it all came from.
With this tool you also have the ability to learn from other peoples projects, saving tons of time, work, and cash by avoiding their mistakes.
I find it odd that most of the cart world is just now ramping up with their Drop-In multi battery kits and it will be interesting to see what happens with all of that especially with their 10 year warranties.
Note that much of the battery tech has been found to be problematic here and tends to be worn out in about a year. I don’t think anyone here is still running Lifepo4 and has moved on to other things with more promise.
IMO- Your Gen1 Leaf cells at 66% may not be worth the effort. It is up to you.
The Rivian modules sound like an interesting choice but I don’t know anything about them. The guys here smarter than me figured out that the classic gems really enjoy running higher voltage. 88 to 90v is a great upgrade.
Charger-
It looks like the charger you pictured in your post(DQDB) is one that can be programmed for different profiles and higher voltages.
Take some time and explore the archives, Decide on a build plan for your car. What is your car going to be? What environment will it be living in?
You will also need to learn more about what you have.
What motor is in this car?
What gear set is in the gearbox?
What is your skill set?
What is in your tool box?
I would like to know if the Rivian modules will fit physically.
Do you have the pigtails for building the bms harness.
88v nominal is higher voltage tjan will run in a gem, unless you have 0lans to convert to high voltage motor and controller.
The hv limit is about 84-86v, meaning you can only use about 50% capacity.
If you were local, I might concider trading for a pair of Lightning batteries. 10s 36v nominal.
I had a complete set of Rivian, but sold them because they weren’t suited for Gem service.
Oh, wait. You are local. 
That’s where my Rivian batteries went. Small world.
You dont own a golfcart named Suzy-Q do you? They guy i purchased the rivian module does.
I think David
I will soon have 20 prismatic cells wired in series. But have no clue which way to hook up the battery wires.
One if the two major wires from the pack has a black cover but the wire is labeled “pack +” the other end of this wire is labeled “BAT --”
The other major wire is labeled “pack --” with a red cover. The the other end of this wire is labeled “MC+” And has a red cover.
(Attachment 20240311_144739.mp4 is missing)
(Attachment 20240311_144507.mp4 is missing)
Here is where it gets tricky when designing your own pack. This is why I suggested you to study up before you jump in on a project like this.
20 is not going to be enough.
Also- are you running a BMS?
I will add a bms when and if i get it all working. The cells have been sitting in my basement for a couple of years. And are down to 3.3 . Giving me 66 pack volts.
The screen did come on. Yaaaaaa.
But motor did not move.
I added 3 more cells to bring it up to 76v. Still no motor movement.
This is where things get interesting. With the main breaker/switch off. I get 76v drop across the main contactor. With the switch on. I get 1.3v drop across the contactor. And i see 76v when in measure the two big inputs to the controller. I think this is some kind of phantom reading. Because i can physically see that the main contactor did NOT close.
I do have the rear and front of the vehicle off and all wires disconnected. Is one of these preventing the contactor from closing?
Thanks.
2015 e4 it was an isurance claim
I think what you are observing is the pre-charge circuit doing it’s job.
It normally happens when you have the MBS ON (Main Batt Switch) and also KeyON. It pre-charges the caps in the controller to prevent the massive power surge at MC (Main Contactor) Close from blowing up the output transistors.
On a 2015 car, the MC will not close until a number of safety checks are passed and you press down on the pedal to go. If the controller is upset over one or more issues it normally displays a code number on the Dash Display.
Trying to run the car on 66v is one of them. I bet it was showing a code 15 at that time. Adding 3 more cells helps.
Are there any codes on your display now?
These are the three screens i get when pushing the trip button.
I requested a pdf service manual from someone on a forum .but not have recieved anthing yet
We all get busy. What is your email address?
I have one for a 2013 that should apply to you.
I do have the rear and front of the vehicle off and all wires disconnected. Is one of these preventing the contactor from closing?
What do you mean by this?
The tail light harness?
Maybe the headlight harness?
Those won’t keep the car from going.
Anything else disconnected?
18-19s battery will error on low voltage unless over charged.
22s + will error on high voltage unless under charged.
21 is the sweet spot. Get by with 20s.
I might be confused on what cells he is using.
I thought it was LFP, (maybe an Eve cell).
Timf1981 - The cells have been sitting in my basement for a couple of years. And are down to 3.3
Hopefully that is not a Samsung cell. It needs a charge.
I was thinking leaf.
The nissan leaf cells are still in the pack. The prismatic cells were in the basement.
My main issue now is to figure out why the main contactor is not closing
My main issue now is to figure out why the main contactor is not closing
If no other error codes on screen,
Have you tried dropping the hand brake(verify that the brake light on the dash goes out), Then pressing the pedal a bit?
