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Unread 01-19-2020, 12:23 PM   #1
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Default Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

I had always planned in converting to Lithium batteries when it came time to replace my FLA batteries, unfortunately their were starting to outlast my patience.

This past December we had an unusual cold period (for Charlotte, NC) and the batteries performance degradation was noticeable.

I could probably get another year out of this 6-1/2 year old batteries, but I had some time off coming up at the end of the year so I decided to do the conversion.

As in any design there are lots of considerations and compromises that need to be taken in account, the goal was to have a basic safe design and not try to set any benchmark.

I have helped a few folks here with their BMS setup and really liked all aspects and quality of the Zeva setup and if this was an EV conversion where keeping exact track of pack AH was a must, that would have been my choice with a CAN bus control interface.

But it was December, lots of Christmas expenses and my wife often reminding me: "it is just a golf cart ", so I decided to use a cheap FET based BMS and add relays for the LV and HV setup.

While I did not take a whole lot of pictures, I will try to describe the reason for some of the design choices.

I purchase the 7 Leaf G2 Modules from TechDirectClub for around $540.

I also ordered the container box from them for $60, I liked the black color and it would have cost me at least that much in materials for a "one of" box.

The 10 amp charger was also a cheap one from Amazon, normally $100 but during Christmas was $84.

The BMS was a 20 amp with Bluetooth interface version for $35 from aliexpress.

The relays, plastic box, wires, diodes, etc probably another $60 but I had most of it already in spare parts.


The First picture is when I got the batteries (took about 8 days from order to delivery) and was setting up the voltage output on the charger.






In this particular charger the voltage output is controlled by the trim-pot shown on the Top Left (VR2), I turned it counter clockwise until the Voltage was 56.7 or 4.05Vpc.






I changed my design after this procedure and having to buy a not so common fast acting 11 amp fuse for my Fluke.

While the charger current output regulation does a great job charging the output capacitors during power UP, the capacitors are directly exposed to battery current and the initial charging current if the charger is connected to the batteries while the capacitors are discharged is very high.

I had noticed the LED on the charger stays ON even with the AC power OFF since it is being powered by the batteries.

I disconnected the meter to make sure the charger LED went OFF and as soon as I connected the meter again to read the current being drained from the batteries, the fuse blew UP since there is no current regulation from the batteries to the charger.

That meant I could not use the simple charger DC output disconnect as the relay contacts would not last long switching the power and it would be hard on the capacitors as well.

Controlling the charger AC power meant a constant 0.007 Amp discharge when the charger was not ON so I had to come up with a plan "C".


I kept all BMS wires the same length, put number markings on each wire before combining them in two bundles.

I used heat-shrink tube to create the wire conduits and folded the longer wires inside the tubes as needed to get a clean look.

The wires for the Cell taps have 1/4" non-insulated ring terminals and the wires for the balancing taps have non-insulated #8 stud ring terminals.

This picture also shows the temporary placement of the three relays, BMS and Bluetooth module.







This picture is after all wires are connected and the box is ready for closing.

Rather than installing by-pass switches for the unlike event that I would need to operate or charge the cart without the BMS, I took care of that by using male and female bullet connectors for the Controller Lockout as well as the charger positive wire.

That way all I have to do is to disconnect the wire(s) from the BMS input and connect it directly to the output.








This picture is after I put everything back in the cart, I moved the Controller to the tub area since I am always playing around with different interfaces.

I will likely (or not...) cleanup those wires after I am done redoing my Regen interface, these batteries don't accept much Regen current when the pack is near full and I have not determined how much "practical" capacity I need.







This is the wiring diagram of the final version (I had to sketch it this morning since I never did one after the changes).


These relays are rated for 48v but operate as low as 36v (guaranteed) and will last longer with less power dissipation at the coils.

The P1 (Pilot Light) is a 12v LED light (I had a large red in spare parts) and its purpose is to reduce the voltage at the relay coil while providing a visual indication when the BMS is either charging or the cart is ON (discharge).

You can also use a 600Ω x 1 watt resistor in its place.

The Z1 Zener diode is what I decided for the charger disconnect circuit.

The relay K2 is powered by the charger output, so when You plug the charger to AC, the charger slowly charges the capacitors and the voltage starts to rise.

The voltage at the K2 coil before the relay closes is equal to: [Charger current voltage] - [voltage drop on 12v light] - [voltage drop at the Zener diode].

Basically the charger voltage will need to be around 52v before the relay will close, and by that time the charger is regulating the current so the worst possible in-rush current will be 10 amps which is way under the relay 30 amp rating.







The K1 relay disables the Controller during a LV or HV cell condition.


In my Precedent with Alltrax XCT 500 I cut the wire to Pin #10 (KSI power) and connected the ends to the K1 relay, harness side to IN and Controller side to OUT.

That allows the BMS to safely disable the cart even if it happens while driving since the Controller is never disconnected from the pack.



K1 and K2 relays are 48vDC SPST T9AP1D52-48. I would not use the cheap "ice cube" relays found on Amazon as they have a higher coil current.

K3 Relay is 120VAC SPDT relay, it disables K1 during charge and resets K2 after AC is removed.

D1 and D2 are 1N4004 or equivalent and required for DC coil relays.

Z1 is a 5.1v x 5 watt Zener or 300Ω x 1 watt metal film resistor.

P1 is a 12v LED light or 600Ω x 1 watt metal film resistor.


These are parts I typically use so there are links in other threads for them. I will try to post links later if needed but wanted to get this out.

_
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Unread 01-19-2020, 03:01 PM   #2
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Dang it. I wish I had 1/8th of your knowledge on this stuff. What you have just shown to the members is that Leaf Lithium conversion is similar to the cost of FLA replacement. I know you already provide a wealth of knowledge to BGW members and this goes above and beyond but...

1) Those part numbers would be great. Even for the box containing the BMS and relays as well as the BMS itself.
2) What are the wire sizes you used on each interface?
3) I'm not exactly sure where the pack is on your drawing.
4) What is the 120 VAC into K3 used for? I would have thought that the only 120 VAC would have been to the charger.

Thanks again, Sergio. A stable inexpensive leaf conversion as you have shown will greatly help me and others.
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Unread 01-19-2020, 03:13 PM   #3
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Sergio, great post!!! I started putting together another pack on Saturday and was documenting it to update my DIY 101 thread using simular Chinese BMS. Now that you've covered it you saved me a lot of typing!!!

Great write up. One of these days I'm going to have get the relays and wire up your HV/LV ckt.



Sent from my SM-G960U using Tapatalk
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Unread 01-19-2020, 08:04 PM   #4
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Thanks for detailed write up and pics. Looks great
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Unread 01-20-2020, 10:52 AM   #5
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

The pack connections are B+ and B-.

The K3 relay (120Vac) is needed to deactivate the relay K2 once the cart is disconnected from AC power.

If You look at the picture of the installed pack, power from the AC receptacle goes under the driver's side where it connects directly to the charger and to the relay inside the Control Box.

All of the wiring between the Relay coils circuit is 22awg due to its low current requirement.

The wiring from charger DC output to relay contacts and to pack positive and negative is 12awg.

The wires on the K1 contacts is 14awg in case it is used to interrupt the KSI power instead of just the Controller KSI low current input, pin #10 on a Precedent Curtis or Alltrax XCT.

I soldered 18awg to the BMS Input (B-) and Output charge/discharge (C-) when I first got the BMS, but 22awg would have worked as well.

Here is another close-up picture where You can actually see the wire gauge on the wires:







One thing I would do differently is to place the top cable gland holes a little closer to the sides of the Box and the side cable gland holes a little higher than half-way so there is more room to route the wires inside the box:







Here is another view of the pack before I placed it in the tub:







I had to use my side grinder to cut a small block protusion on the back of the tub to get the pack fitted.







I am putting together a list with links to parts and will post soon.
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Unread 01-20-2020, 11:32 AM   #6
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Great work Sergio ....

Looking forward to the rest of the build-out.
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Unread 01-20-2020, 12:48 PM   #7
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

As I mentioned I have a lot of these miscellaneous parts at home from other projects, but I tried to put a list together to all products used in this setup:


7 Leaf G2 modules, bus-bar and 1/4" Cell tap screws:
https://www.techdirectclub.com/48-vo...tion-lot-of-7/


Leaf "#8 stud" Center tap screws:
https://www.techdirectclub.com/lot-o...n-1-and-gen-2/


Metal Box for 7 Leaf modules:
https://www.techdirectclub.com/48v-k...age-container/


Battery connection Studs:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Anderson Charger Connection:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Charger 10 amp, 14S Generic:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


BMS 14S, 20 amp with Bluetooth:
https://www.aliexpress.com/item/3287...d3ca4c4dHGu4hn


Plastic Box for BMS/Relay:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


48vDC SPST Relay:
https://www.mouser.com/ProductDetail...QaAg4pEALw_wcB


1N4007 flyback diode:
https://www.mouser.com/ProductDetail...xY3rLmCS1i8%3D


120vAC relay:
https://www.mouser.com/ProductDetail...AENZrAmmiTg%3D


Cable Glands (variety pack):
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Zener 5.1v:
https://www.mouser.com/ProductDetail...LNK2%252Bms%3D


300 ohm resistor (if Zener diode is not used):
https://www.mouser.com/ProductDetail...nWXYXGO2BJY%3D


P1, I had unused eagle eye LEDs similar to these. The Blue, Green, Yellow and purple are better color choice due to their higher voltage drop:
https://www.amazon.com/Motorcycle-Da...=1&sr=8-6&th=1


620 ohm resistor (if P1, 12v panel mount LED is not used):
https://www.mouser.com/ProductDetail...Q4V%2FdWXPM%3D


120vAC receptacle for cart:
https://www.amazon.com/Journeyman-Pr...3-9797311?th=1


1/4" non insulated ring terminal (cell taps):
https://www.ebay.com/itm/272695645997


#8 stud non insulated ring terminal (balancing taps):
https://www.ebay.com/itm/292130709738


The relays listed above use 3/16" quick connectors for the coil and 1/4" quick connectors for the contacts, You will need insulated crimp terminals for those.
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Unread 01-20-2020, 05:09 PM   #8
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Sergio, would you build 3 packs for me that are ready to drop in to EZGO RXV's? I would happily drive to NC and pick them up.
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Unread 01-20-2020, 05:39 PM   #9
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Quote:
Originally Posted by brightred2020 View Post
Sergio, would you build 3 packs for me that are ready to drop in to EZGO RXV's? I would happily drive to NC and pick them up.
Oh, and 2 more for a Club Car DS. I think mine should go first this is a club car forum
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Unread 01-20-2020, 05:40 PM   #10
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

I was almost over building one of these for my cart and sold on buying the drop ins from Allied. Now i am back on the hook. Thanks
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