2002 E825 Basic electrical questions..make it make sense to me!

[JockGem]

#1 Probably the most basic question one can ask but can someone please tell me how many volts the hot side of my key switch should read all the time and what both sides would read when i have the key switched on ?? I have a simple 2 pole switch from NAPA on there. Where should i be pulling the ground from to measure the key switch? Chassis? Controller Neg? 1st Batt Neg? Last Batt Neg?

When grounded to:

Neg of battery #1 which is directly behind the rear drivers seat……..

switch off….30V hot side…21.5v switched side

switch on….30v hot side…30v switched side

Neg of battery #6 (which i believe is the last batt in the series top shelf under hood?) please correct me if i am wrong.

switch off…4.5v hot side…..13.7v switched side switch on…4.1 v hot side….4.1v switched side

Neg of controller…

switch off…30v hot side…21v switched side

switch on….30v hot side…30v switched side

Neg to chassis (I used the horn ground here)

switch off..13.3v hot side…0 v switched side switch on…13.3 hot side…13.3 switched side.

Pulling from #1 batt neg to #6 Batt pos i am reading 78.5v.

Can someone tell me what is the “main battery pack” please? In everything i read or watch everything is always off the “main pack” but when you have 6 batteries i am unclear as to what that is referring to and if i should be pulling off the neg of one battery and the pos of another or is it off one battery or a location under the dash?

There is a few reasons i need to figure this out.

1. I am trying to install a little battery fuel gauge to come on when i switch the key on. Problem is when I have it grounded and touch it to the hot side of the key switch i get nothing but when i go to the batt and touch neg and pos respectively it works. Any thoughts or direction on this one?

2. I am also trying to install a 5 pin 72v relay in front of a 72v step down converter in front of a fuse box for more accessories thinking i am doing the right thing when it comes to adding lights, soundbar blah blah blah. Am I ? I believe I have the updated converted in the Gem which some said i could use for the accessories but I would still like to install the equipment i have just because i have it now and also to learn the way this voltage stuff works on this thing. I want the converter to power on when i turn the key on which the converter is capable of doing but at this point i am looking for help because i wired everything up the way the diagram shows (without the relay in line yet) and popped the 20amp fuse on the converter. I have attached a few pics so you can see what i am working with. Anyone willing to help me out on this one? Again i would like to add the relay in front of this converter unless the converter’s key switch wire is doing the same thing the relay would do and only be drawing power if the key switch is on? I appreciate the advice in advance gentlemen. Hopefully i can get some guidance and get this thing wired up for my daughter by the weekend.

   
   

[JarJarJava]

What happens when you lick the terminals on the switch?

[Inwo]

@JockGem

Neg to chassis (I used the horn ground here)

switch off..13.3v hot side…0 v switched side switch on…13.3 hot side…13.3 switched side.

Correct method. 12v system is isolated from traction battery.

[JockGem]

across both terminal that created a lightning rod in my pants !

[JockGem]

Please pardon my ignorance but what is the traction battery ?

[AssyRequired]

Ok- Note to future readers: For clarity, the first thing when submitting such a post is to state what year the car is that you are having issues with. From details gleaned in the post, I can guess this is a Gen1 car. (why make me work for it?).

Second, (if a Gen1 car (99~04)), then you need to identify if your car has the new DC Converter/wiring update installed. @JockGem actually stated this, and Yes, I see the Surepower unit in the pic.

We can proceed…

@JockGem - The first thing you need to understand about the electrical system is that there are two systems in this car 72v to drive the car, and 12v to drive the misc accessories. The two systems are isolated from each other and when testing circuits the correct reference must be used otherwise you will get some pretty strange results on your meter.

what is the “main battery pack”

The 72v system is usually referred to as a complete pack. Sometimes even called the “Traction Battery” in EV speak. It might even be referred to as the “motivator” (not really). Depending on it’s state of charge it has a wide swing of expected voltage. To avoid confusion of numbers by the nitpicky probers, I will sometimes refer to it as a more generic PackV unless looking for a specific number when diagnosing an issue.

When referring to one/ether end of the pack, that point will be called out as B+ (pos) or B- (neg). These are specific points that can be tapped for reference in the car.
B- on the pack is under the seat, (NEG) post on the first battery in the chain, under the driver on the left. B- under the dash is on top of the controller, Right hand side.
B+ is the POS post, last battery in the chain, up under the front hood, or under the dash, pass side of the car, on either side of the main fuse. There are other places B+ can be picked up, but they are more complex to describe.

There should be no other wires connected to the batteries other than the interconnect cables.

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how many volts the hot side of my key switch should read all the time and what both sides would read >snip< Where should i be pulling the ground from to measure the key switch?

Your car key loop is based on 12v (ref ChassGnd). When probing your key loop you should get +12v on the hot side of the key switch when it is off. and then when KeyON it will be on both sides.
Follow?

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1. I am trying to install a little battery fuel gauge to come on when i switch the key on.

Best place for this would be to attach the Neg wire from your little monitor to B- up at the controller, then attach the Pos wire from your monitor to the output from the Key relay (gray wire). Locate the Key relay under dash, up near the base of the windshield on pass side.

==

I believe I have the updated converted in the Gem which some said i could use for the accessories

Know that the surepower converter is rated for 30a.
Figure out how many amps you will add to this car. LED lights don’t add very much. I don’t know what the specs of your sound bar is. Mirror ball, smoke and bubble machine will add up as well as the spot lights on the stripper pole.
If not all of that applies to the extra activities of your daughter then possibly the surepower unit will handle what you are looking for.

The car even has two extra unused circuits and places for fuses!
(I found these the other day and have not published it anywhere yet. I am curious how many cars have these wires and why nobody else has discovered them yet. )

Back Room/Unpublished/Secret Squirrel content

Up under the hood in front(under the rubber flap) is your fuse holder.

Note that there are no fuses in 7 and 8. ← (this has always bugged me)
Inspection of back side of the fuse block reveals there are wires attached to these vacant spots!

Wire colors are
F7 - Grn/R
F8 - Brn/R

They dive into the Main harness and can be found exiting over by the controller either taped to the harness or floating (not hooked to anything) with shrink tubing over the end. These may even be paired with a Blk(ground) wire for your use (or use ChassGnd for your accessory -12v).

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2. I am also trying to install a 5 pin 72v relay in front of a 72v step down converter but I would still like to install the equipment

But Ok, If you must complicate your car even more…
Installing an extra converter can be tricky. It needs to respect the separated relationship of both pack(72v) and accessory(12v) grounds. I have not studied yours, but if both black wires are not electrically related, you can give it a try. Also, check the case of the converter to make sure it is not connected to either black wires.

The other tricky wire is the little red “wake” wire. The diagram is confusing, but it implies that you need B+ to activate the controller. (remember that your car Key loop uses 12v). You could use that same gray wire to activate this converter.

i wired everything up the way the diagram shows (without the relay in line yet) and popped the 20amp fuse on the converter.

Difficult to say what you did here, but it might be a product of mixing the grounds. Double check your wiring, disconnect your grounds. Try again.

[JockGem]

Wow i cant thank you enough. I especially appreciate the clarification on the main pack and the B+ and B- locations thank you. I do apologize about not specifying the year and model of the cart as that was a total brain fart on my end. Its a 2002 E825 4 seater. I will edit the post to reflect that thank you.

I had no idea its broken down into 72v and 12v systems thanks for that detail. I’ll take what you have given me and play around with some things like you said…disconnect, trace and reconnect some things and see what happens. Thank you so much for taking the time and detailing things the way you did. Aside from my dog labeled pictures are my (a man’s) best friend! I’ll do a little work and report back. I know i am going to have more questions along the way if you do not mind chiming in on them.

Joe

[Inwo]

A lot to read. I may have missed it, but be very sure dc-dc converter is isolated type.

[AssyRequired]

Yep. I more/less put that in the last paragraph using more words than necessary.

But Ok, If you must complicate your car even more…
Installing an extra converter can be tricky. It needs to respect the separated relationship of both pack(72v) and accessory(12v) grounds.

[Pythan]

(post deleted by author)

[JarJarJava]

@JockGem

across both terminal that created a lightning rod in my pants

This guy is awesome!