S18 Battery Problem

[John A Peters]

S18 Charger Does Not Charge

Everything was fine The S18 is fun to ride around around people, but the charger port broke. In order to replace the charger port I had to replace the whole circuit board. It was tedious, but when I got it done, I took it outside and tried it out but since I had not put in all of the screws to secure the board down to the heatsink It jumped around and fell in its side after hitting my hand. I think maybe the four wire pins for the start button unplugged. I brought it back in and put all the screws security to the heat sink plate and took it outside and it worked fine, but I could not charge it because - surprise the Lenovo charge port on the new board was a different style.

I finally got the matching charger plug for the charger and soldered it on, but it won’t take a charge. The charger stays green instead of turning red to indicate charging. I'm wondering if it's not around for a month and that was enough time because the batteries to go below 60 V to know if the BMS we will not work. I wonder.

I have hooked the charger directly on the one of the larger batteries and it does turn red to indicate charging but on some of the other batteries it doesn’t do anything and one of them it starts green flashing.

Bard.google.com (AI) tells me the below which may or may not be correct.

The S-18 unicycle does not have four 84-volt battery packs. Instead, it has three 72-volt battery packs, for a total voltage of 216 volts. This is because the S-18 uses a 3S2P battery configuration, which means that there are three battery strings in series, with each string containing two battery cells in parallel.

The smaller battery packs on the S18 unicycle are not directly connected to the charger. Instead, they are connected to the larger battery packs through a series of wires. This means that the smaller battery packs will only charge when the larger battery packs are also charging.

How can I get it to charge?

Oh well at least I have a T4 but I prefer the S18

[Scubadragonsan]

Have you try contacting SF PEV Works for advice or repair to solve your problem? Link https://pev.works/

[chanman]

Disregard the AI response, it's on drugs.

I would measure the voltage of each of the battery packs separately, this should tell you if there's a problem with one of them or whether your charger port replacement or connections are bad if they all seem fine. You should expect the small packs to be equal and half the voltage of the big packs since they are in series together, and parallel with the big packs.

Edited August 1, 2023 by chanman

[John A Peters]

7 hours ago, Scubadragonsan said:

Have you tried contacting SF PEV Works for advice or repair to solve your problem? Link https://pev.works/

They feel that the S18 is an old machine and I agree with them that it has so many screws holding the side covers on and they don't care to work on it. They would work on it but I assume it would be costly. I know the owner and I agree with him. It's probably best if they stay away from it.

[John A Peters]

5 hours ago, chanman said:

Disregard the AI response, it's on drugs.

I would measure the voltage of each of the battery packs separately, this should tell you if there's a problem with one of them or whether your charger port replacement or connections are bad if they all seem fine. You should expect the small packs to be equal and half the voltage of the big packs since they are in series together, and parallel with the big packs.

Turn man thank you very much.

The voltage measurements are 69.2V and 72.02V larger battery packs. 34.7V and 34.8V on the two smaller battery packs.

The charger is putting out 84.2V. It never changes color with everything hooked up standard but if I disconnect one of the batteries and put a charger into that plug it does change color on one of the batteries but on one other battery it just stutters.

[chanman]

Well the small pack voltages together are close to the first pack so that seems fine, and the pack voltages aren't too low or too high. The second big pack being that much higher is a problem though and would explain why they won't charge when all connected. I'm not sure about the cause, possibly you did this yourself if you let just the one pack charge for a while?

If that's the case then hopefully you can separately charge each of the big packs, and then both of the small packs, and once they're all fully charged you can connect everything together and it will stay balanced and discharge and charge properly.

Edited August 2, 2023 by chanman

[alcatraz]

I've never worked on the S18 but...

You have three packs essentially 69.2v, 69.5v, 72.0v

That's a big difference between them and usually if they were all connected you'd likely melt some cables. That means the charger board likely has disconnected one of the packs and perhaps prevents the wheel from turning on.

Try to disconnect the 72v pack and see if the wheel powers on. If that doesn't work, try powering on the wheel with only one pack connected.

The packs should match eachother before connecting them together. You might need to charge them individually so that they match (+/- 0.50v).

[NErider]

S18 batteries have main voltage and Sub voltage on the smaller pins. And even one of the 4 batteries only uses 1 pin for sub voltage measurements. 

This must be tested properly or you could possibly cause further damage. 

Are you aware of the sub voltage pins and the expected volts required on those pins? If not, I can looks at the documentation and see if I can help more. 

The sub voltage provides battery health info to the board. If a pack goes too low, you lose sub voltage and the charger will not recognize the battery. 

[NErider]

With the batteries disconnected from the board, you'll want to measure the main voltage and subvoltage of each battery. The back right(BR) battery is unique in that it only has 1 subvoltage wire, and so it needs to be measured differently.

 

A front battery main voltage has a max voltage of 84V and a nominal voltage of 72V. The subvoltage should be ~12V.

 

The rear batteries add up to one complete front battery, and so each rear battery should measure half of a front battery. The back battery has a max voltage of 42V and a nominal voltage of 36V. The back left battery also has a subvoltage of ~12V, while the subvoltage of the back right battery when measured from these terminals should measure 18V.

Attached image is refrence for the Back Right Sub voltage reading with green indications and the purple is the other battery sub voltage pins.