Battery charging / power supply switch board for a Red Rhino electric scooter

[withalligators]

Hey folks,
A friend of mine found a electric scooter being tossed. The company is Red Rhino, the model appears to be a Reddie. The device seems pretty simple. It's a battery, a charger/switching board, and an electric motor. The input is an external power brick.

Some short or something happened on the board and damaged it pretty severely. I tried to repair the damaged traces by running a few wires around what was missing, but still no luck. I'm no engineer, and really don't understand the layout of it. For example, that resistor goes nowhere. Why?

Bypassing the board with the leads from the battery works, the motor spins.

Any advice on getting it working or replacing it? There seem to be generic boards on ebay.

Cheers

[petehall347]

did you check the fuse ?
which resistor ?

[withalligators]

Yes, sorry for not mentioning it. Fuse is fine.

The bottom grey one. Which now that you point out, may be a capacitor?

[stj]

that was destined to fail,
there is no diode across the relay coil to protect the transistor!!!

[withalligators]

Originally Posted by stj

that was destined to fail,
there is no diode across the relay coil to protect the transistor!!!

Yes, certainly seems like a POS, but I can only take your word for it on the why. Worth repairing / modding as you suggest or looking for a drop in replacement?

Cheers

[stj]

can you draw a diagram of how it connects to everything else?

there is probably a better way, if not then that;s an easy fix i suspect.

[eccerr0r]

Starting to see a lot of lead acid scooters being disposed of... or are old lithium ion ones also being dumped?

[withalligators]

Here's a diagram as best as I could do with my limited knowledge.

[redwire]

I couldn't figure it out, I redrew the schematic but the relay coil connections are unknown as the traces go underneath it. If you can beep out the 85/86 terminals, where the 15R resistor goes and Q1 anode (middle pin) goes.
What connects to CN1?

I imagine you press a button, the relay pulls in and the scooter motor is on. But how do you stop this thing?
The SCR (transistor) purpose is to latch something (relay?) and keep it on, until ???

[stj]

maybe the voltage divider and scr are a low-battery or motor overload cutout.

[withalligators]

Originally Posted by redwire

I couldn't figure it out, I redrew the schematic but the relay coil connections are unknown as the traces go underneath it. If you can beep out the 85/86 terminals, where the 15R resistor goes and Q1 anode (middle pin) goes.
What connects to CN1?

I imagine you press a button, the relay pulls in and the scooter motor is on. But how do you stop this thing?
The SCR (transistor) purpose is to latch something (relay?) and keep it on, until ???

I'll see the guy tomorrow and ask him to test continuity on those leads, but I think 85/86 go nowhere, as does the capacitor and the anode of the transistor. Which resistor is 15R?

Looking more closely at your draft, (and I could be totally wrong) but the only thing on the negative side of the charger is CN1, which goes nowhere.

[redwire]

The relay must have connections to the coil, this pic shows they are there but run on the top of the pc board, if you look carefully.
I don't see a capacitor on the board. There is a 15 ohm grey body resistor going to CN1 the two-pin plug. It does not connect to the charger like you think, it has to be the enable or on/off switch for this entire board.

[withalligators]

Ah, right. I see the traces now. Also, the throttle must connect to those second set of male spades, right?

[redwire]

I don't what the throttle looks like. I assume it's downstream of this relay board?
I would say the board acts as a master power switch, the SCR latches on once the motor receives any power.

All the melted traces seem to be between the battery and the charger, so I think the charger shorted somewhere.

[withalligators]

Ok, there's good connectivity between the anode of Q1 and 85 on the relay, and good connectivity between CN1 and 86 on the relay.

What's interesting is that 85 and 86 have good connectivity, and the anode of Q1 and CN1 have good connectivity, but the numbers are really low between the anode and 86 and CN1 and 85.

But, I'm an idiot, so there's a solid chance that's not interesting at all.

[stj]

numbers are really low? explain.

[withalligators]

Q1 to 85 I get ~80ohms. Q1 to 86 I get descending numbers until it settles at 0.1/0.0.

For CN1 to 86 I get ~80ohms. CN1 to 85 I get the same descending numbers.

For 85 to 86 I get ~80, and for Q1 to CN1 I also get ~80.

[redwire]

Originally Posted by withalligators

[...] good connectivity between the anode of Q1 and 85 on the relay, and good connectivity between CN1 and 86 on the relay.
... 85 and 86 have good connectivity, and the anode of Q1 and CN1 have good connectivity, but the numbers are really low between the anode and 86 and CN1 and 85.
...
Q1 to 85 I get ~80ohms. Q1 to 86 I get descending numbers until it settles at 0.1/0.0.
For CN1 to 86 I get ~80ohms. CN1 to 85 I get the same descending numbers.
For 85 to 86 I get ~80, and for Q1 to CN1 I also get ~80.

I'm confused... So Q1 anode goes to 85 or 86? CN1 has two pins and one goes to the 15 ohm resistor, and the other to B+ I think.

Overall, It's still not quite making sense, the SCR grounds one end of the relay coil but something at CN1 puts power on the other end of the coil; which is OK but the SCR needs (motor) power to latch on.
So I'm not sure how this relay board works still.

It looks like a pulse from a pushbutton switch at CN1 will pull in the relay and then the SCR latches and keeps the relay on.
I don't know what can shut off the relay - this is puzzling.

The Songle relay SLD-12VDC-1C has a coil resistance of 90 ohms and 133mA nominal which is what your ohmeter is showing.

[withalligators]

Q1 goes to 85.

CN1 goes to the negative side of the charger port on one end and to 86 on the other end, and I get no continuity with it and any of the resistors.

[redwire]

Hmmm... the 15 ohm 3W resistor connects to CN1 pin 1, and other end to the relay coil 86, OK that's fine.
CN1 pin 2 goes to PJ-? I thought it goes to PJ+.

We're still not working because the relay coil needs a source of power from somewhere.