Another Chevy Volt Lithium thread

Car: 2002 (manufactured 01/2002) E825 long bed.
Current config: wrong cheapo batteries from autozone (purchased this way), quickcharge select-a-charge (SCO7210), T1 controller. Everything stock including motor.

My use case: Private property, all hills, most days see 2-10 miles usage.

My goal: Easy maintenance (no checking water), lighter car, and hopefully getting more years out of the batteries than lead acid. Plus it just sounded cool.

Shopping list:
2x 12s2p Chevy Volt batteries (from a 2015) - Purchased on ebay. $390 each.
1x Delta Q New, $350 (#177 for 98v)
1x Chargery BMS $350
1x Over/under voltage spoof $25 (15v for 24s)
1x Charger interface $25 (one wire connection to DQ white)
1x Wiring Harness $70 (for two)

My skillset: shade tree mechanic, rancher, and computer guy.

I plan on documenting my experience (and questions) here, since other threads have been so helpful to me. Even if this is mostly redundant, hopefully others will be able to find something useful from it. I decided to only go with 2x 12s modules because I’m hoping I can satisfy my relatively modest range requirements with this setup, and I’m trying to save a few bucks. If it turns out I do need the additional range, I will add an additional 2x 12s modules.


Comment from @Inwo in another thread:

The T1 and T2 don’t seem to run over 95v, even with spoof.
Older carts need suspension work.
Even a prewired harness needs to be tested before plugging into bms. (each pin)
Have bms off.
Plug in B- section first.
Isolate bms chassis from “floating” frame.
Extending lcd cable needs shielded wire and away from power cables.
First and last pins of bms plugs are duplicates.
Batteries are in series. One “low side” B-, and one “high side”. B+ (or two of each)
Harness plugs are not keyed.

Anything to add?
Most users don’t wish to share their smoke stories.
C’mon jump in, the waters fine. :slight_smile:

Regarding T1/T2 controllers not working over 95V, even with spoof… Is this worth me even trying, or should I just only charge each cell to 3.95v so I don’t go over 95V?

Suspension: my front suspension is old and worn out, and I have a lot of negative camber. I’m planning on putting my 2 Volt modules under the passenger side of the bench seat, and hoping that removing a couple hundred pounds from the front of the car will help with the saggy old suspension. Not sure what it will do for traction though, since I routinely have stuff in the bed of the gem car. I’m not a light guy.

I have a T1 in my car and have not had a problem going over 96V. I’ve charged all the way up to 97V with no problem. The voltage spoof works great. I will be curious to see if you have trouble at 96V. The only issue I get is an error 76 when lifting off the throttle while charged above 95V. I suspect it is from a transient voltage inside the controller but haven’t figured it out yet. I don’t normally charge above 95V because I have way more range than I need. On rare occasions if I know I might be running the hills hard or going to the other side of the community I will charge above 96 and just endure the errors until the voltage drops.
Concerning suspension - I’ve never heard of one sagging. They are notoriously over-stiff. I purchased some air shocks off of an old Goldwing but will need to fab a bracket to mount them. Will have to wait til after vacation but it should make it ride nicely with the reduced weight. I’ll be following your project closely!

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It’s worth trying to find the max voltage. Then set the bms to stop charger.
That’s what Grant and a few others report.
A T4 will run at 100 volts.

It’s most likely regen settings protecting what it thinks are 72v batteries.
Remove regen and work on motor braking.

@Inwo I originally assumed it was regen so I lowered the threshold to below 50% battery charge before it will come on and it still does it. It happens instantaneously upon lifting off the throttle so I’m not sure it can even start regenning that fast. I will probably completely eliminate regen for a test run to see if it goes away but not until after vacation.

I don’t understand regen settings. Try going the other way maybe.
Or ask @LithiumGods.

Where should my ~72v B- and B+ cables physically connect to from the batteries?
Because I’m going to put my two batteries under the seat, I’ll need to disconnect the cable that currently runs from B6+ (up front), and re run a new cable from B2+ under my seat.

The existing cable that runs from B1- should be fine when I re use it, but would still like to know where it should physically connect.
This image from the manual shows them both going to the charger, but I think maybe this is more of a logical drawing than a physical drawing.

P.S. For future reference of anyone reading this, in this drawing, B5 and B6 are under the hood (B5 is closest to front bumper, and B6 is closest to dash), while B1-B4 are under the seat. B1 is under drivers side, and B4 is under passenger side.

This is the battery connection picture.

If I understand your question correctly, this image might help. You have 2 batteries wired in series that build string voltage from left to right in this pic. B- will connect to one negative terminal. The positive terminal of that battery will connect to the negative terminal of the second one and the positive of the second will connect to B+ on the car. With a 2 pack setup you should only need the B+, B- wires that run to contactor and controller, and then a single jumper between the batteries to wire them in series. All of the other jumpers from the lead setup are not needed.
Hope this helps


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I need to clarify because what I said above is not completely accurate. In my 2002, under the seat are batteries 1-4. On the driver’s side is battery 1 so you will find B1 - labeled on the wire. This goes to the negative terminal on the low side (left battery in pic above). On the passenger side is battery 4. The cable that connects to B4 + runs to the front to B5-. I connected B4+ to the B+ terminal in the pic above and then re-routed the other end to the contactor input. I eliminated the cable coming from B6+ that used to connect to the contactor. It was a simple matter of fishing the B5- end of the wire back through the firewall. The jumper from B5+ to B6- and from B6+ to the contactor can be removed.
I hope that clarifies it. :slight_smile:

Thanks guys,

I took the flooded batteries out today, and confirmed the physical wiring. At the moment, my goal was just to understand how its currently setup before I replace it with the new setup.

My batteries are connected the same way as Mr Vern Described (1-4 under seat, 5-6 under hood). What I wasn’t sure about was where B1- (which is the same as “B-”/Low side in this case) and B6+ (B+ / High side) connected to the rest of the charging/running system.

Here are pictures of where they connect:

In factory configuration B- (B1-) connects to the Controller here, which in my case is labelled “CONTROL B-”

In factory configuration B+ (B6+) connects to the 400 amp fuse, and is labelled “FUSE”

BTW In my line of work, this sort of labeling is ridiculous because the purpose of labeling is so you know where a cable goes without having to physically trace it out. Labeling Fuse on the fuse side of the cable isn’t helpful, instead you’d label “fuse” on the battery side, and “B+” on the fuse side so you can look at it and know where it goes. So these labels are more for assembly instructions than for understanding where the cables go. But anyway, now I know :slight_smile:

Also, after removing all the batteries, I suspect my original plan of putting the batteries under the seat will not work with my suspension. I’m now probably going to put both 1 or both lithiums up front. I will probably throw the lithiums in and take it for a test drive to see how it is with both config before deciding. we’ll see.

Oops, I forgot about the fuse being inline before the contactor. Glad you sorted that out.

Concerning suspension, I have 2 2002 cars. A 4 seater and a 2 seater and I am not at all convinced that my suspension on either has ever compressed even 1/8". I put lo pro tires on my 4 seater and it rides rough as heck. I left the lead batteries in the front for ballast at first and then took them out one day while working on the car and I cannot tell an ounce of difference. I seriously think an aluminum bar in place of the springs would be more flexible. LOL
My recommendation is to put the batteries under the seat and just leave the lead in for ballast if you want the weight. Then you can pull them out and see if there is any difference. My 2 seater rides smoother because I still have stock tires on it. I believe 100% of the suspension action we feel is in the tires.I also have the Goldwing airshocks to try on my car but I have to fab a bracket in order to make them work so it will have to wait til after vaca.

Our 2002 e825 4 seater rides like it has no suspension when I am alone. Four adults and it smooths out nicely.

OK, so I got a BMS and some wiring in the mail from @Inwo - The only problem is I don’t know what to do with half of it!

Here’s a couple of pictures of what I have, numbered so I can easily reference the items in the photo.

This page describes most of the cables here, but #4 and #7 are a mystery to me. I assume these are the custom voltage spoof, and charger controller that @Inwo makes, but I’m not sure which is which, or what to do with them.

Where specifically do they plug into, and what are the instructions for installing them?

Regarding the current shunt (#10), how/where should I physically install/mount that? Any suggestions, or example photos?

I believe I don’t need the “Relay control wire” (#6), because the charger control wire will allow the BMS to shut off the charger, right?

Where should I mount the temperature sensor (#8)? Any photos or examples?

BMS Harness -

  • There is a single loose wire (circled in green), where does it go?
  • There appears to be a red and a black side to the harness, which plugs do I use, and which plugs are reserved for future use?
  • Several of the BMS-side plugs on the harness are taped, what is the significance of that?

Thanks folks!

1 connects bms via 2
3 is alarm, I don’t use it myself
4 is spoof, replaces controller pin #1
5 connects to shunt 10
6 may be alarm led
7 bms to DQ white wire interface
8 temperature sensors, plug in correct port only
9 com connection for flash updates
10 connects to B-, all load goes thru it to be measured
11 parallel harness, must be connected correctly after battery install

Taped wires unused, for Gen2 modules
Big red plugs parallel high side modules, 48v-96v
Big black parallel low side, 0v-48v
3 small plugs, blk=0-8 cells, blue=9-16 cells, red=17-24 cells
Do not connect until tested!
Bms switch set to ext
Blk first-red-blue
Do not connect until tested! Every time…


1,2,3 blk go to low side batteries, use any two
1,2,3 red high side
Small plugs are jst-xh, connect blk, blue, red, in order, after testing voltages.

Green loop, ? , check integrity of it’s connection,

Thanks @inwo! Makes sense. When you say test, I should just test for continuity to verify the pins are in the right order (low to high side in order on the harness), and of course that I have connectivity, right?

Is there a particular pin tool I’ll need to re-pin the #1 pin on the controller? I have a pin tool for smaller pins (DB9/RJ45 adapters), but it won’t do anything on these large harnesses. Any methods for doing it without a pin tool?

So to confirm, you’re saying that the circled loose wire shouldn’t be loose, and likely came out of the harness?

Yes, it must have pulled out. See if there is a spot for it. If 3 x 9p connectors are full it must be an extra.
Testing will show.

Harness was tested here so no re-pinning should be needed.
By testing every time you connect bms it keeps you on your toes.
From B- using dc volts check each pin. 0v-4v-8v etc. all the way up to 96v.
Except when you go from one plug to the next duplicates. Notice on the harness, they are connected together with scotch lock.

Thanks for posting, it helps.