JJL's 1500w 48v E-Bike Battery Build

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JosiahLuscher

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What an excellent website! I've already learned so much. You all have helped me avoid some major mistakes already; thank you so much.

TLDR: I have a question regarding pack construction. Can I mix Samsung INR18650-20R and INR18650-20Q batteries? - And if this isn't a horrible idea, what type of arrangement should I use?

I'm building a E-Bike pack, so pretty high discharge rate given the relatively small pack size: 1500w ~48v ~35a
I'm building a 13s?p pack. I've been collecting old powertool batteries for about a year now. I also broke down and ordered 50lb worth of power tool packs from batteryhookup.com; those havent arrived yet.

I had NO IDEA that 18650 cells vary so much in their capacity, charging rates, discharging rates, internal resistance, etc... I thought they were as interchangeable as alkaline batteries. Thank goodness you all set me straight.

So most of the cells are being set aside as they are just a jumble of threes and fours of weird sizes, or are low capacity. I do have ALMOST 13s6p worth of Samsung INR18650-20R cells, I'm just finishing up capacity testing. Then I have over 13s1p worth of INR18650-20Q cells.


The Q cells have a much slower charge speed (1a vs 4a) and a significantly lower maximum discharge rate (14a vs 22a).

I'm thinking I put 2 or 3 of the 'Q' cells into each of seven strings? OR I make one string of 'Q' cells and five (maybe six) strings of 'R' cells? OR I keep hunting for battery packs and hopefully get more.

What do you think?

PS: I have many more questions, this is just the most pressing and the one I have no basis to guide me. - I plan on updating this thread or, something, as I go.

 

JosiahLuscher

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I built a 13s1p test pack and it was awesome to see the wheels spin, but the BMS cut out the power almost immediatly if I tried to run it while riding. I don't know exactly how big a pack will be good, but other off the shelf 1500w 48v packs are 14ah. So I figure 7p with 2000mah cells will be the minimum. I'd really like to go bigger, hopefully the shippement of batteries for disassembly arrives soon.

Is this a reasonable pack size?

Any advice on BMS's for ebikes? I got one 13s BMS that says it can output 45A continuous, and 90A Max. I found another one that says it's for e-bikes specificially; it's still in the mail.
 

OffGridInTheCity

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I built a 13s1p test pack and it was awesome to see the wheels spin, but the BMS cut out the power almost immediatly if I tried to run it while riding. I don't know exactly how big a pack will be good, but other off the shelf 1500w 48v packs are 14ah. So I figure 7p with 2000mah cells will be the minimum. I'd really like to go bigger, hopefully the shippement of batteries for disassembly arrives soon.
For 14ah @ 48v - a standard config of 2000mah cells would be 14,000mah (14ah) / 2000mah (2ah) cells = 7 as you said. I would go 14s however for 48v. So 14s7p would get you 14ah @ 48v. I use this link for quick calcs - https://milliamps-watts.appspot.com/

Is this a reasonable pack size?
A 14s7p @ 14ah will have ~ 672wh. 80% of that (e.g. useable power) = 538wh. If the motor is 1500w, then at full throttle, the 538wh would be used up in about 1/3 of an hour (20min). If you run the motor at 1/3 speed (e.g. 500w) then could last an hour. You're showing hi-discharge-amp cells (above) so that's great.

Any advice on BMS's for ebikes? I got one 13s BMS that says it can output 45A continuous, and 90A Max. I found another one that says it's for e-bikes specificially; it's still in the mail.
1500w / 48v = 31.25a. Motor probably surges 2x or 3x? - so say 93.75a. A 100a 14s BMS should let you ride and 150a will give some cushion in case the BMS is not up to 100% of it's specs. :) The key things that come to mind about ebikes vs powerwalls is 1) ebikes are subject to weather - rain/water- so you'd need to make sure it doesn't short out and 2) maybe it would get warm/hot? - so allow for some air-flow if you can.

I'm powerwall only but maybe a Daly BMS - https://www.amazon.com/DALY-Battery-Management-Protection-Balance/dp/B087CDZ9MS - would be a good starting place. They come in a wide variety of 13s, 14s, 100a, 150a, 200a, ... etc. There are youtubes on them for reference.
 
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JosiahLuscher

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Thank you! - So I've switched to a 14s configuration, and I got a few more cells. The ones I ordered still haven't arrived. Well they did arrive but they were tthe wrong batteries! So I returned them, and the correct batteries should be here soon? Maybe Monday.

Not sure I want to wait that long actually, would take 2 more weeks to tear the packs apart, and test all the cells.

I'll keep updating this as I make progress. I did get two packs with 2500mah Samsung 25R cells in them. Enough to add another "p", but I really don't know when mixing cells becomes a problem. I need to read up on that.

Might end up making a 14s7p pack this weekend. I'm using 30ga tinned copper wire for connecting to busses as a sort of fuse. I also need to get more data on what amps-ish that wire will melt at, but it's the best I've got.
 

JosiahLuscher

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Seems like it took forever to get the correct battery packs shipped to me. The summer weather here in Oregon is quickly coming to a close. - The e-bike project had to be put aside because my wife decided to get some chickens; and I just had to build the a chicken pallace.
That's complete now, it may never be "done". ;-)

So after two delays I started working on the ebike again. To warm back up to it I'm salvaging some more cells, and I rebuilt a powertool battery that had failed. WOW! Did that feel good, to take a broken pack, strip out the cells, and rebuild it with recovered cells and have it work. I may do a few more of them to build back up my confedience.

More substantive updates to follow; hopefully soon.
 

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floydR

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Nice chicken palace what breeds are the two chickens in the front of the pen or are they strange looking turkeys?
later floyd
ps I believe average joe and lithium solar both have videos on 30 ga tinned copper wire as fuses. probaly best to test your 30ga wire because of possible manufacturing variations.
 

OffGridInTheCity

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Nice chicken palace what breeds are the two chickens in the front of the pen or are they strange looking turkeys?
later floyd
ps I believe average joe and lithium solar both have videos on 30 ga tinned copper wire as fuses. probaly best to test your 30ga wire because of possible manufacturing variations.
I use 30 AWG tinned copper wire - https://www.amazon.com/gp/product/B01M0AXONC/ref=ppx_yo_dt_b_search_asin_title in all my packs. They burn thru at 7-20'ish amps in my anecdotal burn tests.

>pack size: 1500w ~48v ~35a
At this level, 7p would be 35a/7p = 5amp/cell. The 30 AWG should work but you could go with thicker wire. Do you know if you have surge amps?.
 
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JosiahLuscher

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Nice chicken palace what breeds are the two chickens in the front of the pen or are they strange looking turkeys?
later floyd
ps I believe average joe and lithium solar both have videos on 30 ga tinned copper wire as fuses. probaly best to test your 30ga wire because of possible manufacturing variations.

They are "Transylvanian Naked Necks" - A friend dumped them on us as a joke cause she thought they were ugly. So far they are ok chickens, not really sure I'm ready to judge. I've nwvre had a rooster before, but they seem more aggressive than the Bard Roc's (SP?) we had before.
 

JosiahLuscher

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I use 30 AWG tinned copper wire - https://www.amazon.com/gp/product/B01M0AXONC/ref=ppx_yo_dt_b_search_asin_title in all my packs. They burn thru at 7-20'ish amps in my anecdotal burn tests.

>pack size: 1500w ~48v ~35a
At this level, 7p would be 35a/7p = 5amp/cell. The 30 AWG should work but you could go with thicker wire. Do you know if you have surge amps?.

Thank you for the info on the wire!

I don't know how much the surge at start will be, but it's probably significant. I'm going to go for it with the 30ga wire, and I'll have to check on it after a while. Seeing as this is an experiment for me failure is an acceptable option. I'd rather have the extra fusing than not. I'm putting a 70A fuse on the whole pack.
 

JosiahLuscher

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Progress! I wanted to post the pack configuration here for future reference. (Boring numbers, picture at bottom)

I used RePackR.com, it's a 14s 8p battery, the cell list is:

2005,2012,2020,2026,2027,2027,2029,2037,2040,2043,2044,2044,2045,2050,2052,2052,2056,2060,2061,2068,2069,2069,2077,2079,2080,2085,2090,2092,2092,2100,2101,2101,2102,2105,2114,2121,2123,2124,2125,2125,2127,2127,2129,2133,2134,2135,2136,2141,2143,2145,2146,2147,2147,2147,2150,2151,2151,2157,2157,2158,2159,2164,2166,2168,2168,2169,2186,2171,2173,2174,2181,2181,2181,2182,2183,2184,2184,2188,2191,2193,2193,2195,2196,2197,2200,2200,2203,2206,2206,2209,2211,2215,2215,2221,2223,2225,2227,2234,2237,2242,2244,2249,2251,2254,2261,2270,2272,2176,2279,2281,2297,2307

RePackR gave me this layout:

2193 2297 2215 2237 2254 2242 2281 2261 2249 2227 2270 2272 2307 2279
2181 2234 2200 2197 2223 2209 2200 2206 2225 2215 2195 2251 2186 2244
2173 2211 2184 2188 2203 2196 2181 2150 2221 2206 2183 2157 2182 2191
2168 2193 2158 2181 2147 2174 2151 2147 2184 2171 2176 2146 2169 2168
2157 2159 2151 2102 2134 2125 2147 2133 2127 2164 2136 2125 2143 2166
2145 2044 2129 2101 2127 2092 2141 2123 2069 2135 2121 2100 2092 2105
2124 2026 2079 2101 2052 2085 2056 2114 2069 2037 2090 2080 2060 2027
2043 2020 2068 2077 2044 2061 2027 2050 2040 2029 2012 2052 2045 2005

Photo attached.

Also I found an interesting wire fusing video:

View: https://youtu.be/qMGJ0PIUUXM
 

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JosiahLuscher

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Victory! It works!

It took WAY longer than I had hoped it would to create all the buss wires and solder on all the 30 AWG fuse wires on to the buss's. That took at least 12 hours, ridiculious! It was my first time and, I was making it up as I went. There are many things that I think could speed up the process.

Welding the buss wires on to the batteries was also very time consuming!

The technique for welding 30 AWG wire to battery cells was difficult to master, but I think I found a relatively reliable technique: With one probe apply hard pressure on the wire against the cell, then lighten up so you're _just_ pressing gently. Then apply the second probe firmlly to only the battery cell. If pressure on the wire is too high the wire tends to deform and not 'stick' if pressue is too low the wire is annihialiated in a bright blue spark and is gone. - Also, good safety tip - wear sunglasses with strong UV protection to protect your eyes.

If you can afford a K-Weld, I hear they can be set to output a specific amount of energy. I'm using a super cheap 8$ ali-express welder.

Well all that is done now! And it rides great!

I need to make a battery holder/box or _something_ to protect the pack and hold it on the bike. But oh man does it feel good to zoom down the road on this thing. I'm not sure right now how much of that is relief that I did it and it worked, and how much of that is enjoying flying up hills with no effort.

Thank you all for you're help!

I'll update some time later when I figure out a battery box. But I might put that off for a week or so. I need a change of pace, and I'm toying with the idea of 3D printing a battery box. But my 3D printer isn't big enough to print a whole one in one go. At least not yet!
 

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italianuser

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Congrats man! Great job... looks good; and yes I invent things as I go ahead, too... I suppose it's what we all have in common in the forum (y) :p
 

JosiahLuscher

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Bike testing updates:

Further tests make it seem like my e-bike has the power to go faster than 35mph, but the motor controller is either limited to, or not capable of, putting out significant torque above 35. On a long flat stretch it quickly got to 35, but then the power seemed to evaporate. With a slight tail wind I did eventually get up to 39mph, but it felt like the motor hit some soft RPM limit. -- This really is _plenty_ fast enough; it is just a bicycle.

Range testing is still underway. I went 28 miles today including some big hills, the battery voltage went from 58v to 51v.

The battery management system will shut off the bike if the battery voltage falls below 42v.

The energy in the pack compared to the voltage might not be linear, but it definitly can go further than 30 miles, which is pretty great!

Unfortunatly the roads around here are littered with lots of things hazardous to bike tires. I've ridden my road bike into Longview once; and got a flat tire just after crossing the bridge. The tires were old, and I replaced them both. - But almost the same thing happened again today with the e-bike. The cheap rear tire that came with the motor kit got a flat on the way back out of Longview. Again just after crossing the bridge. I'm going to have to get the strogest kevlar mountian bike tires that are available.

Also the duct tape holding the battery is much worse for ware, so a better battery case is also a priority. :)
 

JosiahLuscher

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Range testing completed! The battery has enough power to get me into town, and back, but climbing the big hills on the way home really eats up the power. So 26-28 miles of range with lots of hill climbing, stop and go traffic, and almost no pedaling on my part.

I'm taking all the chargers and battery tools and making a more premanent place for them in my shop. (I need to get that folding table out of the way!) So I last night and today I made this huge box to put on the wall to hold cells. I just made it with scraps as a design-build project. It will hold 1,560 18650 cells!
 

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italianuser

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Range testing completed! The battery has enough power to get me into town, and back, but climbing the big hills on the way home really eats up the power. So 26-28 miles of range with lots of hill climbing, stop and go traffic, and almost no pedaling on my part.
26-28 miles is a huge distance! I do 4KM with my bike to get to work (and another 4 to get back) and it seems a lot to me LOL :giggle:
I'm taking all the chargers and battery tools and making a more premanent place for them in my shop. (I need to get that folding table out of the way!) So I last night and today I made this huge box to put on the wall to hold cells. I just made it with scraps as a design-build project. It will hold 1,560 18650 cells!
Obviously you keep them safe and at a certain distance from anything else... worst case occurs if they should warm up and get into a thermal runaway or fire scenario. Hopefully never!
 
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