Nissan Leaf 7 Module Pack Wiring Drawing w/ Sergio Relays

[PingEye3]

Attached is a wiring drawing for a 7 module pack, using a Chinese BMS incorporating Sergio's LV/HV & Charging Relay Mod into the drawing. This drawing is designed for a 11x17 size paper. Easily taken by thumb drive to your local Office Depot to have them print copies at 11x17 of larger.

As a reference to the 4 terminal strip on the drawing, I have also included a picture of the power end of my pack where the 175A Anderson connector is mounted and the 4 terminal strip, a pic of terminals an of the BMS end of the pack for reference.

Terminal Strip:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Anderson Connector:
Mouser Pt # - 879-6326G5
https://www.mouser.com/ProductDetail/879-6326G5

I suggest that you do not buy the 175A 2Ga "Anderson" connectors from Amazon unless it is 100% Anderson brand. The Chinese substitutes have 1/2 the thickness of copper in the crimp section of the pins as Anderson. If forced to use them, solder completely, I would not trust a crimp on such thin copper. IMHO

[molfpedal]

Originally Posted by PingEye3

Attached is a wiring drawing for a 7 module pack, using a Chinese BMS incorporating Sergio's LV/HV & Charging Relay Mod into the drawing. This drawing is designed for a 11x17 size paper. Easily taken by thumb drive to your local Office Depot to have them print copies at 11x17 of larger.

As a reference to the 4 terminal strip on the drawing, I have also included a picture of the power end of my pack where the 175A Anderson connector is mounted and the 4 terminal strip, a pic of terminals an of the BMS end of the pack for reference.

Terminal Strip:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Anderson Connector:
Mouser Pt # - 879-6326G5
https://www.mouser.com/ProductDetail/879-6326G5

I suggest that you do not buy the 175A 2Ga "Anderson" connectors from Amazon unless it is 100% Anderson brand. The Chinese substitutes have 1/2 the thickness of copper in the crimp section of the pins as Anderson. If forced to use them, solder completely, I would not trust a crimp on such thin copper. IMHO

That is an awesome drawing, PingEye3! Good for any cart!

[WalterM6]

My question is. Is the Sergio system any better than the original PingEye design? I've got the Pingeye design and I'm trying to decide if it will be worthwhile changing over.

[Sergio]

Gary and I exchanged some emails on that last drawing, we made sure it included how to disable RXV and Club Car IQ/Precedent carts during an LV or HV condition and included descriptions and part numbers of what is needed so folks can easily locate the parts.

PingEye3 has posted many diagrams in the past for different BMSs, so as long as Your setup has a way to safely disable the cart during an LV or HV condition and also stop the charger on a HV (and possibly LV) condition, You don't need to change your system.

Specifically for the inexpensive BMS like the one I used in my Nissan Leaf Pack build, the only way that BMS design can disable anything is by removing the negative connection from the C- port.

Even if Your BMS is capable of handling the charging current, I prefer to by-pass the BMS for charging and eliminate the heat generated in the box by the charging current going through the BMS FETs.

I also noticed in my charger that the LED light stayed ON when it was not powered by AC, I measured it and there was a 7mA "vampire" load, not much but about 5AH/month or 10% of my usable capacity.

I also noticed that if the charger was not connected to the pack, the first time You plugged it to the cart there was a large spark, similar to what You get from plugging a DC voltage reducer to your pack.

So I added the Zener diode to delay the relay closing after the charger was powered and until the charger voltage had risen enough to create a smaller load on the relay contacts when they closed.

I also added the 120vAC relay since I needed a way to "unlatch" that charging control relay once the charger was OFF.

The 120vAC relay also doubles as a "disable cart while charging" circuit.

The "P1" pilot light or 12v LED indicator light purpose is to lower the Leaf 56+ voltage to a less stressful level for the 48v coil relays and it also provides a visual indicator the BMS is working.

Hopefully this helps.

[PingEye3]

Sergio, thank you for adding a great explanation for everyone on this thread.

For those who wired the packs as I have always done, and Nick (RIP) from EV Battery Center had recommended, without the LV protection; can now build the box separately and easily add it to your system for extra protection with only a few wiring changes.

[Sergio]

I was just thinking that if You build just the relay setup (no BMS in the box) to add to an existing system, You can use a smaller box like the one below for the relays:

https://www.mouser.com/ProductDetail...hZDfURGTHFU%3D

[PingEye3]

Great point, always thinking!!!

[fstop]

Originally Posted by Sergio

Specifically for the inexpensive BMS like the one I used in my Nissan Leaf Pack build, the only way that BMS design can disable anything is by removing the negative connection from the C- port.

Even if Your BMS is capable of handling the charging current, I prefer to by-pass the BMS for charging and eliminate the heat generated in the box by the charging current going through the BMS FETs.

With your electrical engineering prowess and experience with the FET based BMS units, I wondered if you would have any advice regarding setup of a pre-built battery that includes this type of BMS.

I have a RoyPow battery currently (which uses this type of BMS as far as I know) and have been happy with it, but am considering a similar 72v system for increased KWH / range and potential increased performance and efficiency. RoyPow indicates they will release a 72v version, but it will be some time in the future from my information.

The question is, the company (Chinese) I've been speaking with of course uses a FET based BMS, with charging also going through the BMS. You had indicated it would reduce heat / wear on the BMS to bypass the BMS during charging - and that makes sense to me. The RoyPow SOC meter requires the BMS to be in the circuit in both charge and discharge, but the 72v system I'm considering has a simpler approach and uses a voltage-based SOC meter.

I think I could specify they wire the BMS differently if it would be beneficial, but I'm not sure what that would involve and wouldn't be able to articulate this to them. I'm not sure I'd implement the HV / LV cutoff solution (but perhaps could add it) since it won't fit inside the steel case, but how would you approach / wiring this type of BMS if you were building a compact single box solution? Or if including another set of terminals on the box for charger input would be beneficial? I realize that regen charging would still have to travel back through the discharge terminals, so not sure how that would work - or if it even would be useful.

I'd like to initially configure any cabling / terminals in the best way possible for our higher amp golf cart specific usage from such a battery / BMS, which I think they typically set up for more generic applications.

Thanks for any insight you might have.

[simicrintz]

How close is this info to a Chevy Volt system? I don't want to derail the thread (I have started one of my own already) but I am just not seeing a bunch of info on the Volt conversion in my searches.

[Sergio]

Those two questions are somewhat related in the fact that it depends on the internal constructions and connections between cells and/or any existing BMS inside the "drop-in" box..

As long as You have access to all BMS and cell connections, You can either install your own BMS or perhaps modify the internal wiring to accommodate external handling of LV and HV shutdown.

The main reason that some BMSs use internal FETs is that they need a way to monitor current in/out in order to provide accurate SOC display.

Any so called SOC meter that only has power connections is not reliable for predicting Lithium batteries SOC, regardless of what any vendor may say otherwise.

Some more expensive BMSs like Zeva use external shunts and need to be always powered during charge/discharge in order to keep track of AH in/out.

If You were installing the Lithium pack in an EV, then I would stick with the models that accurately keep track of SOC using external shunts/hall effect sensors so you don't get stranded.

For a golf cart application I personally don't see that as critical and a "rough estimate" of SOC based on voltage reading is sufficient for most folks.

simicrintz, if the Chevy Volt pack has the BMS tap harness installed, you can tap the existing connector for installing a BMS, the photo below shows the B- and each cell tap available on that connector: