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Old 09-20-2018, 04:56 PM   #1
ag4ever
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Default Lithium Battery Conversion - LV & HV control relay wiring

I plan to convert my 2012 Club Car Precedent to Lithium Batteries this weekend. I was going to use a Gigavac disconnect and solenoid for main pack disconnect and HV/LV power control, but there is no indication on when they will ship.

In the interim I plan to use the T9AP1D52-48 style relay to control power to the charger on the HV side and control key switch power to the existing solenoid on the HV/LV controller side.

The intention is to allow the batteries to charge if the key is in the off position with the first relay and have the second relay disconnect power to the controller if the pack voltage gets too high on regen or too low on normal discharge.

I have sketched up the attached wire diagram, the biggest concern is where I have bridged the HV to LV relays on the BMS. I think I need a diode to prevent a back feed of power to the charger relay coil. (Do I also need a diode on the bridge to prevent back feeding from the charger relay coil to the controller relay coil?) Can some of the brilliant minds here look it over and give their input?
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Old 09-20-2018, 04:58 PM   #2
ag4ever
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

File did not attach in previous post. See below sketch.
Attached Images
File Type: jpg Sepex relay wiring.jpg (71.5 KB, 0 views)
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Old 09-21-2018, 11:19 AM   #3
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

This will be a good thread. I am going to use the same relay's on my build.....but I now need to determine what size diode's I will need.

I did some surfing and found this site: http://www.futureelectronics.com/en/...056-4294917087
where I entered my highest voltage (I used 58.9)and also selected "Uni-directional".

So...for you guys with the knowledge stuff......am I selecting the proper diode for my needs?

Now, don't use my results as gospel, as this is all new to me.....but from what I am understanding about diodes is, I need a "fly-back" diode to protect the relay from premature failure. (Nothing like being 2 miles in the woods only to have....say the LV relay fail and get stuck) I don't know if that's possible.....but I don't wanna find out.
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Old 09-22-2018, 09:35 AM   #4
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

I don't like the idea of the relays ON all the time, unless someone remembers to put the Zeva BMS to sleep it will lead to early relay coil failure.

I designed this with Sepex carts that do Regen brake in mind since both Low and High voltage cell conditions should be monitored, but it also applies to Series carts and the additional $0.10 for the diodes is not a big deal.

It is also not a bad idea to monitor Low cell voltage during charge in case the charger fails and acts as a load to the pack.

The D5,D6,D7 and K4 are totally optional and would put the Zeva BMS to sleep automatically anytime the Key Switch is OFF and the charger is unplugged from AC power.

The only thing to remember is that the Zeva auto-balance bleeding resistors run for up to 1 hour after the charging cycle ends, so the charger should not be unplug from AC power immediately after it finishes charging.

Please notice that power is not being removed from the Zeva BMS, so it should not affect SOC saved data.


K1->K3 - 48v SPST Relay:
https://www.mouser.com/ProductDetail...55-T9AP1D52-48

K4 - 48v SPDT Relay:
https://www.mouser.com/ProductDetail...55-T9AP5D52-48

D1->D7 - Diodes - 1N4007:
https://www.amazon.com/100-Pieces-1N...s=1n4007&psc=1

K4 - 120vAVC SPDT Relay:
https://www.mouser.com/ProductDetail...qfqAYZNg%3D%3D

Hopefully this will give other members addtional ideas on how to protect their Lithium packs.

Attached Images
File Type: jpg Zeva_HV_LV_Relays_Idea.jpg (126.1 KB, 0 views)
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Old 09-22-2018, 01:08 PM   #5
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

Sergio,

Thanks a million! That is what I was trying to accomplish.

If my understanding is correct,

Relay K3 supplies power to the coil of Relay K2, this way, K3 and K2 coils are closed only when 110v ac power is present (charger plugged in).

Relay K2 also requires BMS LV and HV relays to be closed to supply ground, so relay K2 coil is powered when: 110v ac power is present, pack voltage is above min threshold, and pack voltage is below max threshold.

Relay K1 controls the activation signal to the controller, and the coil is energized only when: key switch is on, pack voltage is above min threshold, and pack voltage is below max threshold.

Relay K4 is normally closed and supplies a ground path to the sleep input on the BMS. When either the charge circuit (relay K3) or the key switch is on, this ground path is disconnected.

Diodes D1, D2, and D7 are flyback diodes.

Diodes D3, D4, D5, D6 are used to prevent back feeding current.

If that is correct, I have the K1 and K2 relays on the way, should be here today. Just need the K3 (110v coil) relay and the K4 (NC 48v coil) relay, as well as a hand full of diodes.

This has been extremely helpful.
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Old 09-22-2018, 05:11 PM   #6
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

That is a very good description.

The design also provides the proper "Wake Up" sequence.

When the Zeva is in sleep mode, it turns OFF its internal power supply which powers OFF both LV and HV Solid State Relays.

When the cart is either plugged to 120v or the Key switch is turn ON, the K4 relay will power UP and take the BMS out of "sleep Mode".

Once the BMS is fully functional and has satisfied both High Voltage and Low Voltage cell condition, it will enable both Relays LV and HV and the cart will either drive (K1 Closes) or charge (K2 Closes).

I imagine the time between the Zeva waking up and the K1 relay closing falls in the "not noticeable" range.

If someone does something similar please lets us know the wake up time delay.
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Old 09-22-2018, 05:55 PM   #7
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

That 120v ac coil relay is some mythical creature. Can’t find one at mouser, or digikey, or any local parts houses, or google, or amazon, etc... Mouser has theirs on backorder with the mfg.

So I plan to get this one.

https://www.mouser.com/ProductDetail...5AXXBC3ML-120A

Should be the same, just different form factor and only the NO contact.
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Old 09-22-2018, 05:59 PM   #8
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

Quote:
Originally Posted by Sergio View Post

The design also provides the proper "Wake Up" sequence.

When the Zeva is in sleep mode, it turns OFF its internal power supply which powers OFF both LV and HV Solid State Relays.

When the cart is either plugged to 120v or the Key switch is turn ON, the K4 relay will power UP and take the BMS out of "sleep Mode".

Once the BMS is fully functional and has satisfied both High Voltage and Low Voltage cell condition, it will enable both Relays LV and HV and the cart will either drive (K1 Closes) or charge (K2 Closes).

I imagine the time between the Zeva waking up and the K1 relay closing falls in the "not noticeable" range.

If someone does something similar please lets us know the wake up time delay.
How does it wake up the ZEVA? From what I see, it applies ground when the relay is not powered. When the coil sees power, it removes the ground. If the ZEVA is in sleep mode and powered down, how does it know to power up. Does the ZEVA in sleep mode, still monitor the sleep input?

I plan to wire mine up like this, but I doubt I have equipment that can measure the delay. I bet it is much less than 1 second.
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Old 09-22-2018, 08:44 PM   #9
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

Sergio, when I look at the diode placement on D3 and D4, (from the ZEVA LV) you have the diodes placed that no voltage from the LV can pass up. So....from my understanding is that the ZEVA can't do what it's suppose to do.

Since no current is going past the diodes D3 & D4, how can the BMS properly function?
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Old 09-22-2018, 09:31 PM   #10
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Default Re: Lithium Battery Conversion - LV & HV control relay wiring

I did not notice that relay was not in stock, You can also get it from other sources:
https://www.newark.com/schneider-ele...30a/dp/32C2652
The one You linked would NOT work, it needs to have a N.C. contact.

Most AVR type MCU will have a very low current (much less than 1 micro amp) sleep/idle mode that detects a level change interrupt in order to to wake up, so Yes, the BMS will still detect the negative level being removed from the "sleep" pin when the K4 relay closes and wake up.

DaveTM, those diodes are oriented properly since current is flowing from each relay (positive) to the LV+HV path to the pack negative.
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