TwixFix Posted June 1, 2016 Share Posted June 1, 2016 I took apart my Gotway Mten and noticed there was a ton of padding and extra space around the battery pack. After some careful measurements and planning, I managed to squeeze 48 cells into the Mten without any modification to the original shell. I used 3500mah LG MJ1 cells in a 16s3p configuration, so if I’m calculating correctly it should be 59.2V * 10.5Ah = 621.6Wh. I purchased the BMS board from Jane. I purchased a few extra since shipping was expensive, contact me if you’re interested as I may have an extra BMS. The original pack was 16s2p of Sony US18650V3 2200mah, so 59.2V * 4.4Ah = 260.48Wh. The new pack makes a huge difference. With the original pack, at about 50% capacity, you would notice the wheel response becoming soft. It would become easier to overlean when doing abrupt direction changes such as when idling. I never went below 50% with the original pack because it made me nervous I would overlean the wheel. With the new pack, I can now empty the pack to ~54v when the wheel would start to tilt back and it would still feel stronger than the original pack at 50%. Basically, the performance of the wheel stays the same from full to empty. So in terms of usable capacity, I’m guessing it’s closer to 4x more than the original. Here’s the initial charge using the Charge Doctor V2 to log. Not quite 620wh, but I think it might be due to not fully discharging the pack before charging or maybe the cells need to be cycled a few times to get the full capacity. Build pics: Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted June 1, 2016 Share Posted June 1, 2016 Holy crap that's a monster sized pack. Nicely done. Do you find using the metal braid to solder to the battery ends better than using nickel tabs? You might want to consider getting one of those spotwelders as it looks like you do this a lot! Are those smaller red wires to the BMS heavy enough gauge to handle the current? ps: Nice work on the IPS130 pedal height mod as well. Link to comment Share on other sites More sharing options...
TwixFix Posted June 1, 2016 Author Share Posted June 1, 2016 31 minutes ago, HunkaHunkaBurningLove said: Holy crap that's a monster sized pack. Nicely done. Do you find using the metal braid to solder to the battery ends better than using nickel tabs? You might want to consider getting one of those spotwelders as it looks like you do this a lot! Are those smaller red wires to the BMS heavy enough gauge to handle the current? ps: Nice work on the IPS130 pedal height mod as well. This is just my second time building a pack, I don't really plan on doing any more in the future, so I couldn't justify a spotwelder. The smaller red wires are 22 gauge. The Gotway BMS is actually 2 separate boards, terminals B1-8 on one board, and B10-16 on the other. They're wired together by 24 gauge wires, so I'm guessing the 22 gauge I used is enough. I believe they're only used for balancing and not during bulk charging, so not much current actually flows through the wires. I didn't use the second board in my pack to save space, though I think it might fit in there. There's no actual circuitry on it, it's just a breakout board essentially. Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted June 1, 2016 Share Posted June 1, 2016 Where did you source all those batteries from? So after adding up all the costs how much would you say that your TwixFix SuperPack cost to make? Link to comment Share on other sites More sharing options...
TwixFix Posted June 1, 2016 Author Share Posted June 1, 2016 26 minutes ago, HunkaHunkaBurningLove said: Where did you source all those batteries from? So after adding up all the costs how much would you say that your TwixFix SuperPack cost to make? Lol, the question I've been avoiding answering myself. Let's see, 48 LG MJ1 was ~$310 shipped from batterybro.com. The BMS was $60 shipped. and the heat shrink was $13. Everything else I had on hand, so a little under $400. It's probably overkill, but I'm loving the extra range and peace of mind. For comparison, I was quoted 320 Euro ($345) for a 414wh pack shipped from 1radwerkstatt, which I would have settled for if they were able to figure out a way to ship to the US. I was originally just going to build a 414wh pack, then I saw I might be able to fit 48 cells when I opened up the mten. Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted June 1, 2016 Share Posted June 1, 2016 That's not too bad of a price at all considering you have 50% more capacity than 414 wh plus I wonder if they could have made the custom fitted pack to fit that space. It likely would have been a lot more if you ordered it. Do you have any room for cushioning around the pack in case of a fall? I guess it's all shrink wrappd up so it should be solid. Nice job especially arranging and wiring up all those cells to fit in that space. The Mten doesn't look that big it's surprising what you have accomplished. I bet @Grimlet will want to place an order from you... Link to comment Share on other sites More sharing options...
US69 Posted June 1, 2016 Share Posted June 1, 2016 4 hours ago, TwixFix said: Lol, the question I've been avoiding answering myself. Let's see, 48 LG MJ1 was ~$310 shipped from batterybro.com. The BMS was $60 shipped. and the heat shrink was $13. Everything else I had on hand, so a little under $400. It's probably overkill, but I'm loving the extra range and peace of mind. For comparison, I was quoted 320 Euro ($345) for a 414wh pack shipped from 1radwerkstatt, which I would have settled for if they were able to figure out a way to ship to the US. I was originally just going to build a 414wh pack, then I saw I might be able to fit 48 cells when I opened up the mten. That's a fantastic Price for over 600wh!!! Link to comment Share on other sites More sharing options...
HEC Posted June 1, 2016 Share Posted June 1, 2016 Nice "Tetris" work you've done here. Congrats on job well done and having improved your riding safety amongst other parameters! Link to comment Share on other sites More sharing options...
alon av Posted June 1, 2016 Share Posted June 1, 2016 Very very nice work ! I would love to make a pack as an outside option. Can you explain by a sketch or some graphical document how to wire the batterys to the BMS board ? I may want to buy from you a BMS board . paying you by paypall is ok ? Thanks Link to comment Share on other sites More sharing options...
TwixFix Posted June 1, 2016 Author Share Posted June 1, 2016 13 hours ago, HunkaHunkaBurningLove said: Do you have any room for cushioning around the pack in case of a fall? I guess it's all shrink wrappd up so it should be solid. No room for padding, it's basically an exact fit, the pack doesn't jiggle at all inside, yet the case doesn't struggle to screw together. I do have a 360 degree foam wrap around the shell anyways since the Mten is hard on the legs without padding. 5 hours ago, alon av said: Can you explain by a sketch or some graphical document how to wire the batterys to the BMS board ? I may want to buy from you a BMS board . paying you by paypall is ok ? This diagrams explains it well. The BMS has terminals for B1-16 which connect to each junction between the cells in series. Paypal would be fine, PM me if interested. Link to comment Share on other sites More sharing options...
Sponge Posted June 2, 2016 Share Posted June 2, 2016 Nice work I already designed a bigger Case for 3D printing to fit in a second or just one big battery but now I am thinking to do just what you did ...have you ever thought about that when the tire is broken that you can throw away the unicycle? I have the 340Wh version but your Calculation tells me that they are wrong ? My pack has Panasonic 3400mah 59.2V * 6.8Ah = 402,56Wh ??? Link to comment Share on other sites More sharing options...
Chriull Posted June 2, 2016 Share Posted June 2, 2016 32 minutes ago, Sponge said: Nice work I already designed a bigger Case for 3D printing to fit in a second or just one big battery but now I am thinking to do just what you did Be carefull soldering the top of the cells - if you offend somehow the "fragile" green insulation at the side you have fireworks! ( shortened the cell!) 32 minutes ago, Sponge said: ...have you ever thought about that when the tire is broken that you can throw away the unicycle? Why - are there no spare tires/tubes available? 32 minutes ago, Sponge said: I have the 340Wh version but your Calculation tells me that they are wrong ? My pack has Panasonic 3400mah 59.2V * 6.8Ah = 402,56Wh ??? If you have a 16s2p configuration your calculation seems right. Link to comment Share on other sites More sharing options...
Sponge Posted June 2, 2016 Share Posted June 2, 2016 2 minutes ago, Chriull said: Be carefull soldering the top of the cells - if you offend somehow the "fragile" green insulation at the side you have fireworks! ( shortened the cell!) I have a shop here they would do it. 2 minutes ago, Chriull said: Why - are there no spare tires/tubes available? No could not be found in various aliexpress dealers and shops here in my town I checked even at gotway who no longer have them. If anyone know where to get them please tell me. Manufacturer: HIC Tubeless Nylon 9 x 3.00 - 6 Max.Inflate to 45 P.S.I - 3.0BAR Link to comment Share on other sites More sharing options...
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