Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Batteries, Chargers, and Battery Management Systems.
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Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Mar 21 2018 7:13am

Hey guys!

So to give a little back story. I haven't really riden to work yet, primarily because the roads and trails around here aren't really advantageous of commuting from where I'm at. I live in DC and so typically Metro is an option but not where I'm at, I'd have to drive and then park to metro which would cost more than what I'm already paying now for parking at my work ($180/mo). I got the idea that I could bike to work by saving a ton of money from parking and auto expense. However, that really hasn't panned out yet. My SO and I are looking to move this summer to a place closer to our work and so that'll give me the opportunity to finally bike to work. I built an ebike last summer and started with the battery. I used a combination of cheap chinese cells and older brand name cells. Some of which I have some concern about... So this is where I'm at. Through riding last summer I was able to put over 100miles on the bike and I had a blast. I took a nasty spill in the parking lot of Marriott International in the fall and that was my wakeup call that this bike isn't so much a bike anymore...when you're going 30+mph... So anyway. Back to the bike. I have the stock controller which says 26A 48V, but I can comfortably do 33-34A which gets me close to 1500W. This is awesome for accelerating and getting up to full speed. On a fully charged battery I can do about 35MPH. Riding comfortably is around 20-25MPH. In a single ride I've riden around 20 miles and still had plenty of charge left. I think I was down to around 44V.

So the battery. I built the battery as cheap as possible using copper wick wire and used cells, some new. Some of these cells only got me around 1500mAh but I didn't test every single cell... So here's my dilemma. I'm going to take apart my current battery of 91 cells. Discard the cells I retest that achieve under 1900mAh and replace them with a bargin! I found older NCR18650 Panasonic 2700mAh cells for $1.6/cell. Not all of the cells will be replaced as this would be quite expensive, but only the cells that fail the test will be replaced. Also, I'm adding a parallel group to reduce my load per cell. Since I'll get around 1400-1500W that means at full charge I'll draw close to 4A per cell, or 2C from a standard 2000mAh cell which most of them are. I'm really hoping the Panasonic cells perform really well and help the battery out. lol. I also had some design flaws in my first battery that I hope to fix with this new one. I designed the battery to hug the top rail of my bike as you'll see in the picture below. Problem was I didn't have my bike at the time I built it so I didn't measure the diameter of the bike tube correctly and so the cells ended up being too wide... Hopefully through this redesign I'll be able to make a more compact battery. Basically I'm attempting to make it look like it's part of the bike rather than one of those dolphin packs you commonly see.

If anyone is interested in purchasing the Toshiba battery pack that has the panasonic cells in it: https://www.ebay.com/itm/NEW-Toshiba-Li ... 1438.l2649

The battery is probably upwards of 10 years old. The cells in the test battery I got were around 3.4V, charged them up and they still get over 2700mAh at 1A discharge. Pretty exciting!


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For now I've purchased a new soldering iron (last one died somehow). More wick wire from china which will take awhile... and the 24 panasonic cells. I also have LG 18650 S3 cells that I will include in replacing the older cells. These cells are 2200mAh cells rated for 4A discharge max which should work just fine.

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Mar 23 2018 7:42am

Theres about a pound of tape on my battery that I've been working in the morning on removing. I have most of it gone and the tricky part will be removing all the hot glue between the cells. I've heard rubbing rubbing alcohol around hot glue will release the hold very easily. So I will give that a go.

Few changes. I think a triangle pack is going to be the best option. I want it to be versatile and so triangle seems to be the way to go.

I've got all the new cells ordered and finally a new 54.6v 4A charger. Hopefully this will solve the issue with my balancing. I'm going to have to spend a decent amount of time testing each cell.. I checked the voltages of each series connection on my current battery and I'm from 3.96V to 4.03V from highest to lowest. Quite a range which I hope to fix!

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Mar 24 2018 5:00pm

Well good day getting the cells out of the pack. GOSH this hot glue is a PAIN! But I am SOOO thankful I used an additional layer of shrink wrap for each cell. I can basically just cut out the shrink wrap around each cell and the cell pops right out! Takes a little work but the cells come out nice and clean! No on to some capacity testing!

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Mar 31 2018 3:01pm

Progress! So it seems that a good amount of the crap chinese cells indeed are crap... some have lost over half their original capacity in like maybe 25 cycles......yea i know. Good case of you get what you pay for... howeverrrrr, the Panasonic NCR18650's have arrived and they're the newer ones! So I'm super excited about it! Debating purchasing 3 more packs for an additional 18 cells to replace...

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I did a real quick moc-up of the battery case where it'll fit in my bike frame... It takes up a decent amount of space but I think I can get it work. I'm thinking Lexan will be a good choice of material for the battery box... I plan to round the corners so the box looks molded into the frame...hopefully... More to come! Waiting on my wick wire from China to get here before I can start assembling the battery

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 02 2018 5:49am

Ordered 3 more battery packs since they're the newer panasonic cells. Super stoked about the battery. This one is going to be SOOO much better than my first battery. Wish I had enough funds for an all panasonic battery but I really think this will be a HUGE upgrade over my first battery. Heck I didn't have any cells over 2500mAh and now i've got 1/3 of the battery with Panasonic cells. With adding another parallel set I should be able to get more range and more power while drawing less from each cell. My goal is to draw around 2c per cell which will easily get me over 1500W. My controller is limited by its shunts to around 33-34A so that will be perfect.

I believe I'll get my wick wire in another 2-3 weeks and by then I'll have my pack all designed and hopefully something for the frame built already. After that it should just be soldering the cells together....

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Overclocker » Apr 02 2018 10:55pm

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i have older NCR with dotted wrapper. some of them are clocking in at over 2900mah at 1C (2.9A discharge). that's more than advertised capacity after like 8 years

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 03 2018 5:13am

They're crazy good cells! Now I know why Tesla uses them... I really needed to rebuild my battery because some of these FST 18650 2.2Ah cells from China were clocking in at around 1000mAh...lol and when I first got them they were 2000mAh.... So I'd imagine if I would have kept going they probably would have eaten up my entire battery pack.

Of the 104 cells in my new pack I should have about 40 Panasonic cells. 20 are the LG 18650 S3 cells, 6 Sony US18650GR cells, 9 rewrapped LG cells that I'm not sure which ones they are but they deliver around 2100-2200mAh in testing, 4 Samsung 18650-30A, 9 SZNS Purple Chinese cells which are actually decent, they still hold over 2000mAh, and I'll mix in some decent capacity blue cells that I have left over that can get over 1800mAh. The pack total should get me over 800Wh which will get me a decent range...


I need help with the frame case... I'm looking to make a hard plastic case for the batteries to fit inside the frame but I'm not sure what material to use. I'm worried Lexan is too ridged and might crack over time, plus its pretty expensive for how much I'll need. I need like some decent soft plastic to mold the triangle shape and screw into the frame... any ideas? I don't need something this big:
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but I do need it to be most of my frame. Essentially I want to do the same thing as this: https://www.electricbike.com/build-a-gr ... -than-150/
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I wasn't sure if there was a cheaper material available at HD or someplace...

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by 999zip999 » Apr 03 2018 1:12pm

I would put a set of sense wires on for ez checking with a cell monitor and you could balance thru the leads if needed. But great to have a way to know. You only as good as your weskest string.

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Bobw » Apr 03 2018 1:26pm

I made a frame case for my conversion from 4mm acrylic (picked up a 1/2 sheet for $20 locally). The case holds a 96 cell pack. I was warned that the case would crack from use but so far no problems. Polycarbonate was suggested as a better material to use. Here’s a pic of the completed case, I did some video while making it.
3608D6C0-5C4B-409C-8D53-B7584A696C1B.jpeg

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 03 2018 6:57pm

Bobw wrote:
Apr 03 2018 1:26pm
I made a frame case for my conversion from 4mm acrylic (picked up a 1/2 sheet for $20 locally). The case holds a 96 cell pack. I was warned that the case would crack from use but so far no problems. Polycarbonate was suggested as a better material to use. Here’s a pic of the completed case, I did some video while making it.
3608D6C0-5C4B-409C-8D53-B7584A696C1B.jpeg
Nice! That's my main concern also. I looked up some fiberglass and for starters I'm in an apartment so not really the space to do that and 2nd...its actually really expensive... If I could get a laminate wood that bends but is thick enough I'd work with that and then make metal/foam filled flashing that will mold to the tubes of the bike... that might work..just not sure there's a laminate that'll fit that bill...

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 04 2018 10:56am

OK I think I'm going to go with using lexan for at least the frame of the battery box. I can get a 12x24 piece for $16 and I'll use 2 layers of it around the frame and glue them together which should provide enough support. After that I think I'm going to use my famous roof patch and some wire for the spacex foil look and added rigidity... Once all that is done I'll back it up with foam around the actual battery. I want to have the battery open and exposed so I can monitor it throughout its life and the foam will protect it. Best part about that is I should be able to easily remove the battery as I plan to build in a door with a hinge on the side of the battery case so it's easy to remove and charge.

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 06 2018 11:35am

Well I ditched the hard case design for my bike. It is going to just be too much work and time that I don't have being in grad school... I ended up purchasing a frame triangle bag off eBay. According to the dimensions I should have no problem fitting the battery in it. I've made a few tweaks to my design but I believe I'm all set! Once I get the rest of the Panasonic cells next week I will start to put the cells together. Hot glue is the binder of choice for gluing the cells together. I can hopefully get that done next weekend. My wick wire made it in the US so I will have that soon and I can start to build the battery completely! I'm going to use a 5.5x2.5mm port for charging it. I'll have 12gauge wire leading out the bag to the power analyzer. Final battery dimensions will be a triangle with the length of 11" by 8" down.

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by 999zip999 » Apr 06 2018 1:32pm

Did you get the little circle donut shaped gaskets for the positive end to protect against the negative case not to be shorted out. Before assembly. The whole entire battery is negative except for that little tit that pokes out of the top which is positive.

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by EbikeAus » Apr 07 2018 2:24am

999zip999 wrote:
Apr 06 2018 1:32pm
Did you get the little circle donut shaped gaskets for the positive end to protect against the negative case not to be shorted out. Before assembly. The whole entire battery is negative except for that little tit that pokes out of the top which is positive.
Yes, I definitely would recommend using them as well!
Choose LiFe 8)

May all your batteries be fully charged and perfectly balanced :P

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 07 2018 6:23am

The newer Panasonic NCR18650's already have them on them so I will leave it as is. The others do not. I will likely put down some paper between the packs to add an extra layer of ghetto insulation. The wick wire is very flexible and so I just need to raise it off the negative shell of the battery with something small when I'm soldering the positive end and that'll be no problem!

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This is my template. It's very very close to the actual size the battery will be. I noticed I left more of a gap between the cells than will actually be IRL compared to the drawing. I'm actually considering using my template as a single piece of insulation and also a guide for the connections... lol. I just need a hole punch so I can solder the cells up with the template...

The final dimensions of the 104 cell battery should be 11.25"L x 7.75"H x ~2.8"W...pretty compact for a 104 cell battery. Certainly once I get the frame bag it'll be much easier to ride around with than my previous battery. I plan to use a TON of zipties to really secure the frame bag to the bike...especially since I don't plan on removing the frame bag ever...Compared to my previous battery, this is going to be light years ahead! The 42 or so NCR18650 along with the new LG S3 batteries will really make an impact on the overall performance of the battery. Really looking forward to juicing 1500W outta this thing!

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by 999zip999 » Apr 07 2018 7:21am

The wick is very flexible and can easily touch the sides of the negative can of the battery on the positive end it would be good for all cells to have this gasket. This is where many batteries short out and cause fire.

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 07 2018 8:46am

999zip999 wrote:
Apr 07 2018 7:21am
The wick is very flexible and can easily touch the sides of the negative can of the battery on the positive end it would be good for all cells to have this gasket. This is where many batteries short out and cause fire.
Yea...I'll probably do the paper and cut holes for the positive and negative ends to solder... That should be a full proof measure. I could pick up the circles but I can probably just make the same stuff for way cheaper and I won't have to wait a month for it to arrive from China..

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 08 2018 10:47am

HD is out of hot glue sticks.... A lot of people must be building battery packs around me this time of year...
I'll probably have to wait till next weekend to glue the full pack together. I will also have the wick wire so at this point I can build the entire thing next weekend hopefully and then I'll just be waiting on the new charger and triangle bag for the bike.

Stay tuned!

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 10 2018 5:26am

Had a little bit of hot glue sticks left over from my last battery. So I ended up using what I had... Didn't get me far...

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Everything seems to be coming together really well! I get the rest of the Panasonic NCR18650's today and hopefully the solder wick wire later this week. Glue sticks are still out of stock and they say they will be till next week (slow supply chain).... I guess in the meantime I can start to cut the BMS wires to length...

Using excel and the actual capacity of every cell I can get each series connection within 50mA of eachother which is really good! This will help keep the battery balanced even with using different cells!
This battery is going to be surprisingly small for a 104 cell battery...surprised myself how small the battery can be when you wedge the cells all together

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 14 2018 7:22am

Just a little bit of progress this week. The lack of hot glue sticks is really holding me back. I think I may just end up getting the walmart hot glue sticks which I've read don't hold as well...but I'll be using so much I think I'll be ok...

I went ahead and soldered the negative terminals of the three groups I have done thus far... I'm waiting on the positives so I can get a insulator between the positive terminal and negative body...
It doesn't look the best but it sure works well. The wick wire came yesterday so once I have the rest of the hot glue I can actually put this thing together!

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 17 2018 8:46am

Battery is coming along well. I made some execution errors when hot gluing my battery together and now there's about a quarter inch gap between the cells in the middle of the pack... It looks sloppy but not enough for me to attempt to redo the battery.

Check out my flickr album https://www.flickr.com/photos/30149337@ ... 5521867628

Anyway,
I got thin cutting board material that I'm going to use once the battery is fully built to encapsulate the cells in. This will be my protective layer as I plan to use a rubber foam insulator around them too.

Great news! My triangle bag is going to be here by Thursday hopefully! Assuming usps doesn't lose my package again like they did a few months back I'll have it in no time! Once I get the bag I can verify that it'll fit, assuming the bag dimensions are correct, and I'll finish up the battery! Maybe I can even take it for a spin this weekend!!! Better news! I ended up getting a suspension fork! The 2nd to last upgrade needed for my bike! I've been dying to get a suspension fork and figured now would be the time! The last few upgrades will be to paint the bike flat black and get a new kenda rear tire to replace the stock tire that came with the hub motor! After that my bike should be entirely complete! I also have a 4A charger on the way for the larger battery. I'm hoping this charger works better than my lead acid one and actually gets the bms to balance the cells! I'm going to have to cooling mod the charger though because there's no way I can charge at 4A with no type of cooling for the charger. Lol

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by 999zip999 » Apr 17 2018 9:29pm

I suggest you balance the pack to the same level before you attach the BMS. A bms is not meant to balance a mismatch pack a BMS is meant to keep a balance pack in balance. Put some sense wires on there for easy checking with a cell log.

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 18 2018 9:12am

999zip999 wrote:
Apr 17 2018 9:29pm
I suggest you balance the pack to the same level before you attach the BMS. A bms is not meant to balance a mismatch pack a BMS is meant to keep a balance pack in balance. Put some sense wires on there for easy checking with a cell log.

Yea. I'm thinking I need to do that too. It'll take an extra bit of time but it'll save the bms some.

Ended up soldering all the negative series together so now I just need to do the positive ends then link them alltogether. Even better news is I get my battery bag today! I'll check the fit then see how I want to finish off the edges of the battery with the plastic sheeting.

I also get my new suspension fork on Friday so I'm really hoping I don't encounter any issues installing it. All I know about the trek 800 front fork is it's 1-1/8" threaded with a quill stem. So hoping it's just a quick swap.

I want to repaint the bike. I'm tired of the blue and I'd like a more modern updated bike. Color suggestions? I'm thinking flat black all around.

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by 999zip999 » Apr 18 2018 10:30am

If you dont balance the pack before you put on the. Bms it may take a week for the bms to help. Working it little bleed down resistors to death. Plus you will be asking way your pack won't balance.? ??

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Re: Rebuilding my 48V 14AH 18650 Pack 13S7P to 13S8P

Post by Philaphlous » Apr 19 2018 7:38am

Well good news and bad news.... The good news is I got my triangle bag. The bad news is the dimensions are totally off and not even close to fitting the battery... However, I chopped up the bag and now it's a sleeve and it barely fits the battery. I'm not sure if it's a good or bad thing but I'll be able to make it work....
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Not exactly what I had in mind but it just barely fits....so I'll roll with it.

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