Hacking a SkateMaster (UK) board - help needed!

This happened to me once. I found a cheap automatic lipo trickle charger- think it was like $12 (that I've since burned out and thrown away). It charged the cell to a point where my normal charger would work without giving me an error code. I still have that 6s pack and it is functional.

The charger wasn't giving an error code, just trickle-charging until it hit either the capacity or time limit. However, while trying to get a photo for RMA'ing the pack, the charger decided it would fully-charge it this time. I've had all 3 cells reading 4.20V, so I'll give it the benefit of the doubt. Unfortunately I can't return the pack now anyway; while wiring things up, I accidentally shorted a wire and in yanking things apart accidentally broke one of the balance leads in 2 places. I dissected it in an attempt to solder it back together, but ended up breaking it closer and closer to the pack. It now extends a mm or so out of the shrink-wrap. I searched around for advice and determined that while I could dismantle the battery and re-solder the lead to the PCB, I didn't feel comfortable with it. I stripped back some of the shrink-wrap trying to expose the plastic shield around the battery, but got halfway down and couldn't find the end. I've patched it all up now. Since it's the red cable, I can just solder this to the positive discharge cable, right? I'm hoping to rig up an in-situ charging solution so with luck the batteries won't need to move much when they're laid into the carrier.

Now, a real problem I am having - whenever I plug in the batteries, I am getting huge power surges and sparks, big enough to fry the XT60 connectors. I'm up to seven ruined plugs now, out of spares, and really not enjoying the high-temperature soldering I'm having to do. Whenever I plug the b*stard things together to create a circuit, there is a huge flash and crack within the plug, and even if I'm quick, the contacts in both plugs are blackened and cooked. I mean, I know there's a crazy amount of current in these batteries, but I am struggling to work out why the surges are so big - the controller admittedly does not have a power switch in-line with the batteries, so they are not physically isolated, but even so, I didn't get this kind of fireworks with the SLAs! What I really don't get was that I managed to connect one half of the parallel setup successfully, so the controller had 24V connected, then I plugged in the other half and immediately incinerated the parallel connector. WTF is going on?!

A friend who has airsoft guns was helpful only in suggesting swapping the whole lot out for XT100s. Seeing as I now have everything set up around XT60 connectors, I would like to avoid this if at all possible. Any other advice?

Gargravarr - sounds like a short to me. I'd quadruple check your + and - ... I had similar happen to me one time and turns out i flipped one of my xt-90's i soldered onto the ESC. Fried a couple connectors before i stopped, double checked, and finally found it. D'oh! moment.

The spark you should see even at 24v is only a quick pop with small discoloration to the metal - not slagging or melting - that's welding and makes me think something is wonky and you are grounding out/shorting it.

Post up a series of pics of your wiring and we can look it over for you?

GL!

sl33py said:

Gargravarr - sounds like a short to me. I'd quadruple check your + and - ... I had similar happen to me one time and turns out i flipped one of my xt-90's i soldered onto the ESC. Fried a couple connectors before i stopped, double checked, and finally found it. D'oh! moment.

The spark you should see even at 24v is only a quick pop with small discoloration to the metal - not slagging or melting - that's welding and makes me think something is wonky and you are grounding out/shorting it.

Post up a series of pics of your wiring and we can look it over for you?

GL!

Click to expand...

I suspected it was a short, but showing the same friend this photo, he was convinced it was only a power surge:


Well, the current carnage includes:


Okay, so I dug out my graphics tablet and created this:


Granted, it could be a bit clearer, so let me explain the logic:

• 2 banks of 2 batteries - 1 of 4,000mAh, 1 of 5,000
• 1 battery from each bank in parallel for 12V, 9,000mAh, such that drain should be equal across both banks
• Both sides into series for 24V, 9,000mAh, into the ESC
• 2x3S->6S charging adapters for charge alarms, eventual external charge connector

Besides my atrocious attempt at drawing, is there any problem with this layout?

Ugh... that drawing doesn't help me. OK, looking at it again it makes a bit of sense...

As for your friend who says that looks normal needs to not ever touch electronics again... that isn't spark that's WELDING. That is a short and mine looked almost identical. Smoke and black/melted is not "spark". "spark" is a small tap sound and small flash. You will see a bit of oxidization where it sparked and over time it will wear your connector out. That is not the same. Melted metal is no bueno.

OK, to the troubleshooting. With your drawing not helping as it looks reasonable to me, how about this - simplify. Try a single set in series and eliminate the parallel. If not a problem, try the other set in parallel and not in series. Either has issues, then let's dig into that setup specifically.

Under volting the setup will likely not perform well, so i wouldn't do much except confirm it doesn't weld a connector (parallel).

Make sense from a troubleshooting/diagnosing perspective? Wish i could point out "x" was obviously the issue...

HTH - GL!

sl33py said:

Ugh... that drawing doesn't help me. OK, looking at it again it makes a bit of sense...

As for your friend who says that looks normal needs to not ever touch electronics again... that isn't spark that's WELDING. That is a short and mine looked almost identical. Smoke and black/melted is not "spark". "spark" is a small tap sound and small flash. You will see a bit of oxidization where it sparked and over time it will wear your connector out. That is not the same. Melted metal is no bueno.

OK, to the troubleshooting. With your drawing not helping as it looks reasonable to me, how about this - simplify. Try a single set in series and eliminate the parallel. If not a problem, try the other set in parallel and not in series. Either has issues, then let's dig into that setup specifically.

Under volting the setup will likely not perform well, so i wouldn't do much except confirm it doesn't weld a connector (parallel).

Make sense from a troubleshooting/diagnosing perspective? Wish i could point out "x" was obviously the issue...

HTH - GL!

Click to expand...

That's what I thought - it doesn't make any logical sense why there would be a short, unless the ESC is doing something very strange that it really shouldn't be. Could the charge adapters have something to do with it? All the other cables are insulated (I even went so far as to replace the heat-shrink I had to cut off to re-solder them), the ESC connector has correct polarity and all the batteries are wired up properly.

I did try connecting just one pack to the ESC in an attempt to charge up whatever capacitors might be in it, trying to reduce the spark, and at first it seemed to work - when I connected 2 in series, there was no noticeable spark. However, that was when I cooked the parallel connector.

The charge adapters are the only things I can think might be influencing it, although passing enough current through the XT60s to weld them, I would have expected the balance leads to melt, which they haven't. I'll have to do some experimenting, I guess.

Okay guys, I think I was right about the charge adapters. I didn't realise they bridge the batteries into series - the central pin in the seven-pin 6S connector is connected to both the positive end of the first battery and the negative end of the second (taking GND to be of the first battery). I traced this out on my whiteboard and discovered there is indeed a short when the batteries are wired together in a certain order (other balance leads omitted for some semblance of clarity; focus is on the 5,000mAh bank of batteries):


However, if I plug the batteries into the charge adapter in reverse order, I can't see a short:


Same story on the other side in the 4,000mAh bank:
Short:


No short:


I'd love it if a second pair of eyes could just double-check my wiring; I think I've gotten it right in the second and fourth photos, and I've labelled the adapters accordingly (my batteries are also numbered on their discharge leads), so I think this will now work without shorting.

Shit shit shit...!

I connected the 4 batteries up minus the charge alarms, and sure enough got only a small spark when 24V was applied. As the board stops running long before the cell voltage drops to dangerous levels, I didn't bother with the alarms. However, I got halfway to work this morning and, while riding over some very fine bumps, the board cut out. Hoping it was just a loose power connector, I opened it up... and it had shorted out. The 24V positive cable seemed to have caught on a screw on the controller housing, wore through and shorted out drastically against the case (melted the screw and all). While I do have spare cables, I now have no idea what kind of damage has been done. I might even have blown up the controller :'(

Crap. I'd fix the cable and see if you can get it going again. Hopefully it grounded out without damaging your ESC.

Check out some of the nylon sleeving to avoid wearing through. I'm just about to do this on my motor wires (need to shorten them too).

Techflex general purpose. they have a ton of specialty wraps including high temp and abrasion resistant types. Some are just open ended sleeves, others are open wraps you can put around wires. I prefer the sleeves personally. Most you need to at least melt the ends after cutting or they will unravel. I usually will shrink wrap the ends. The new "clean cut" is nice, but imagine it still might fray over time.

Good lesson about sharp edges inside near wires (or near the cells in the packs). I'd look over any wear points and count yourself lucky if you didn't damage the battery!

I know you are trying to charge without removing the batteries - but if you have simple balance plug extensions you can place a normal battery alarm on one without grounding it out? If it complicates your charging, or you have to pull batteries to charge - is it worth it so you don't possibly over-draw/damage your battery?

Let us know if you get it running again and GL!

So, been a while. I haven't given up with this board, but the UK summer has given up without a fight and I've struggled to see decent boarding weather.

Thankfully the controller wasn't fried. Surprisingly, the broken positive wire didn't short all the way through - there was still continuity. Still not sure why the board cut out; maybe the controller has some kind of safety cutoff. Still, once I replaced the busted series connector, it worked again. I've laid the ESC on its back instead of its side, so now neither the battery or motor wires have to cross over the top and rub against a screw. There is some noticeable heat coming through the plastic battery carrier, but so far it doesn't seem to be hurting it.

I also revised my over-complicated wiring; sorry for that horrible drawing! I decided to go series into parallel rather than parallel into series; not sure why I didn't in the first place, really. So now I have the 4Ah bank wired for 24V, then the 5Ah the same, and them both into parallel to power the board. So I still have 9Ah on tap, and I paid careful attention to wiring them up so I could use the charge adapters. I put the parallel board in the carrier and brought the power connectors out to the side, so I can now attach the charger to one XT-60 and one 6S balance connector to charge all 4 batteries. I also bought a temperature sensor and placed it between the two banks, setting the charger to cut off at 50'C. I haven't seen temperatures get higher than 35'C while charging.

It's working okay, but charging is slow - the charger doesn't output much more than 3.5A even when set to maximum (7A) and the batteries are no longer able to power the board. I guess this is inherent in my approach - it's not a problem because it works, and needs minimal supervision now. I've bought a small waterproof project box that I'm going to use to cover the power connectors to protect them from the elements.

Overall, the board is working well now, but I'm still struggling with range. I think the best I've managed is about 5 miles on one charge. I might be able to cram one more cell in the middle if I bought a 6S. On the other hand, the ESC seems to be designed with a SLA battery in mind, because it cuts off power at around 21V. The individual cells are usually far above 3.0V and could technically discharge further. Is there any way I could convince them to do so, perhaps with a voltage regulator? Or would it be too risky to deep-discharge the batteries?

Well, it's been a very long time. I have actually been using the board as much as I can - it's been working very well with my idea to use the charge adapters and a parallel board. Charging is a simple matter of unscrewing the watertight box on the side of the battery carrier, connecting the main, balance and temperature sensor connectors to the charger and then setting it to balance a 6S. I've been getting a pretty consistent figure of 6Ah put back in the batteries after a day's trip to work and back, so I've spec'd the li-pos pretty well, and they charge properly. Every few charges, I take the carrier off and balance each battery individually. That's been working very well.

Sadly, disaster has struck again, and this time it may be fatal. I think the motor has burned out. Last week, I noticed performance was down a little when first setting off, and the motor was making some odd noises. They cleared once the motor warmed up so I didn't think much of it. Then on Thursday, on my ride home, I hit a bump and the whole thing rolled to a halt. At this point I could smell burned electrics, and when I lifted the board up, there was smoke coming from the motor. I flipped the power off but I guess the damage is done.

The screws holding the motor housing together were badly warped from years of abuse (probably before I even got it) so it's taken me a while to get the tools to get into it. However, when I pulled the end caps off, I discovered the housing is the motor - the end caps hold the armature bearings and the permanent magnets are attached to the tube. The bearings are still good, but there's a strong smell of burning from the rotor even now.







It's a plain brushed DC motor. There are scorch marks around a couple of brushes in the end cap, and the armature is covered in metal filings, which seem to have come off the magnets. At a guess, the magnets have worn away and worked into the electrical path, where they shorted out something. The wiring doesn't look burned, but whatever caused the failure sucked a lot of power through - the casing was untouchably hot and trust me when I say it stinks!

What are the chances of repairing the motor? I've got a sizeable investment in the board now, I'd rather not bin it. The chance for replacement is next to zero since the company is long defunct.

What's more annoying is that we actually have a summer in the UK this year, I'm missing out on using it!!

a year later, but did you find a replacement motor ?