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Discussion Starter · #1 ·
Hi:
I've completed the fabrication part of my reversible Microcar conversion project and I have some questions on the wiring. I have the Build Your Own EV book and seen several diagrams so I understand the purpose and layout of the large components, but need some help on the wiring of the ignition switch, shutoff switch, contactor, and various fuses.

Question 1: I'm not sure I understand the connection of the Charger- ignition key switch- contactor - shutoff switch. What order they go in and what kind of fuses / contactor I need.
Question 2: I'm not sure how to connect the wiring into and out of the BMS.

I've attached a chart of my wiring diagram and would like some help validating where some of these other components go. Anything with a yellow call out box is what I need help with. The pack is a 72v 78ah 2C discharge rate LiFePo4 pack, with an 8k Qs-260 hub motor.

I've also attached a few photos so you can see what I'm building.

thanks in advance,
Shawn
 

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What on earth is that machine????!!! Most excellent!!!!

Lots of questions about your system but will limit to 2 right now:
-Did you generate the drawings or are those from your book? (which I am not familiar with)
-Are you using the exact components as shown? Might be good to start populating some pin name/numbers as you go.

All I can respond to ATM:
"Is this grounded back to the battery negative?" at your DCDC 12V output. Ground this to chassis where the alternator or Marvelous Space-Time Continuator negative post was connected, and 12V battery or other 12V loads (-) as needed.
If at all possible, keep your 12V (-)/ chassis ground separate from B-.

Welcome and good luck with that... thing.
 

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I have a hard time following such diagrams, since a lot of the wiring will actually depend on the functionality of the components. So there is that one high level question - what part of the system controls the contactor ? I doubt it's your BMS. Maybe the motor controller ? Or perhaps you've got the ignition directly switching contactor on/off ?

Either way, you probably don't want to route your charger through the main power contactor. You seem to have a BMS with FETs controlling the battery output on the common port, so the charger should connect to that. I don't believe you need a fuse for the charger, but your main power fuse should be right behind the BMS and in front of everything else, including MPC. Your main power fuse should be rated below the max current rating of your BMS, your contactor and your wiring.

Also you want a fuse for your DC-DC on the battery side, it needs to be at or below the rating of the converter.
 

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(y) More dissection of the system design needed, agreed.
I don't believe you need a fuse for the charger,
Careful there, in most cases the charger will have B+/- wiring much smaller than is safe for the main fuse rating , needs to be protected from short circuit etc. Fuse as close to battery as possible at beginning of smaller wire run.
 

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(y) More dissection of the system design needed, agreed.

Careful there, in most cases the charger will have B+/- wiring much smaller than is safe for the main fuse rating , needs to be protected from short circuit etc. Fuse as close to battery as possible at beginning of smaller wire run.
Short in the charger itself you mean ?
 

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Discussion Starter · #6 ·
What on earth is that machine????!!! Most excellent!!!!

Lots of questions about your system but will limit to 2 right now:
-Did you generate the drawings or are those from your book? (which I am not familiar with)
-Are you using the exact components as shown? Might be good to start populating some pin name/numbers as you go.

All I can respond to ATM:
"Is this grounded back to the battery negative?" at your DCDC 12V output. Ground this to chassis where the alternator or Marvelous Space-Time Continuator negative post was connected, and 12V battery or other 12V loads (-) as needed.
If at all possible, keep your 12V (-)/ chassis ground separate from B-.

Welcome and good luck with that... thing.
Hi:

thanks for responding. I made the drawings in Powerpoint based on the drawings supplied with the components, plus what I could glean from DC wiring diagrams on EV West (https://evwest.com/support/Basic Kit Schematic - DC System.pdf) and some other places. My setup should be simpler than some of the ones I started with because I don't have multiple battery packs and I don't have a 12v battery.

Here are the components I'm using:
1. Kelly KLS7275H controller
2. QS 260 8000w hub motor
3. Delgreen 24S BMS for LiFePo4
4. Delgreen 72v 25A charger.

I still need a DC to DC converter and the other parts I mentioned (fuses, ignition, shutoff, contactor).

Regarding the negative ground, if my existing electrical system is grounded to the chassis I thought I could not ground the EV system to the same. That was why I asked the question.

thanks in advance for your help.

Shawn
 

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Hi:

thanks for responding. I made the drawings in Powerpoint based on the drawings supplied with the components, plus what I could glean from DC wiring diagrams on EV West (https://evwest.com/support/Basic Kit Schematic - DC System.pdf) and some other places. My setup should be simpler than some of the ones I started with because I don't have multiple battery packs and I don't have a 12v battery.

Here are the components I'm using:
1. Kelly KLS7275H controller
2. QS 260 8000w hub motor
3. Delgreen 24S BMS for LiFePo4
4. Delgreen 72v 25A charger.

I still need a DC to DC converter and the other parts I mentioned (fuses, ignition, shutoff, contactor).

Regarding the negative ground, if my existing electrical system is grounded to the chassis I thought I could not ground the EV system to the same. That was why I asked the question.

thanks in advance for your help.

Shawn
You should get an isolated DC-DC converter, then you can tie its negative side of output to the chassis.

So with Kelly you probably will have contactor and ignition tied to the motor controller. Now does that BMS provide for some kind of ignition/sleep mode of its own ?

One other thing - you may want to look into disabling drive mode while charger is plugged in. Kelly may have a signal for that, and if it doesn't then you can have a relay interrupting MPC (normally closed) when charger is active.
 
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