Batteries Batteries!!

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Finally got my SLAs (4) 15ah for my 48v system. V Max Charge Tanks. Supposed to be superior to most SLAs, built to MIL specs with better plates for deepcycle etc- blah blah blah. Have a good warranty though. Waiting on tires to begin the build. Dropping the 700c fixie to 26x1.5 high pressure tires for less rolling resistance.

Next project is to build a Li-Ion battery pack, a 48v 10ah. I bought a lot of 60 Sanyo 18650 2600mah cells still tabbed in pairs. These are supposed to be unprotected. I need 52 for the build. They are used but checked out. Hoping out of 60 I will get what I need. Will assemble them into 13 4cell 10ah packs in parallel then series them together. Going to manage them with a 48v 30amp 13s BMS for Li-Ion. The bike will be built to run with either pack and charge with the same 48v charger so I can swap out as needed.

Any insights, advice and pointing out any brain fades in my thinking would be appreciated!
 

deacon

minor bike philosopher
Jan 15, 2008
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after I burned up the nimh battery pack ( which by the way turned out to be no smaller than the sla pack) because I had to keep adding cells. I am back to using my sla 48 hour packs. I rode them Sunday when the temp was 60+ degrees. and they did pretty darn well. I had used them in the cold and was not impressed with them at all.

so I decided to make a batter pack heater. What i did was take an old camera bean bag I had and put it in the microwave for one minute. It put out a steady though small amount of heat for almost 30 min.

I expect with a little more time in the microwave, and closing the warmer off from the air by dropping it in the battery box, it might do to keep the batteries warm. Im sure it will be safe in there since it is just warm beans in cloth nothing to flame or over heat.

It might be a way to get a few more winter miles from the old sla pack/
 

cannonball2

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Oct 28, 2010
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Sounds like a great idea Deacon! Sorry about the nimh pack. Hope Im able to come up with a decent pack out of this parade of batteries. Read all the rest voltages and really only 3 are suspect. Am cycling them now. Took longer to clean them from original packaging than to build the pack probably.
 

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cannonball2

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Oct 28, 2010
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OK- first lesson learned. These batteries are tabbed in pairs. with proper salvaging the original tabs can be soldered together. However if one does this be sure the tabs on the positive end are humped up off the heat shrink of the battery. The entire outer case is negative. If you have a tab against the heat shrink and burn through it while soldering youre in for quite a light show! Probably best to solder wire jumpers on the positive end to the middle of the tab bridges.
 

paul

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Dec 23, 2007
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this is great cannonball2, thank you for sharing on how to build i bicycle battery! i have wanted to but would have no idea what so ever on what i was doing and learning from you guys, i really do appreciate it
 

cannonball2

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Oct 28, 2010
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Well hopefully my general science learning will prevail. One really has to be careful to keep things in order. Assembling the batteries is fairly elementary. You just have to be familiar with the batteries chemistry/characteristics your are working with. I am trying to match cells. Ideally one would cycle all the cells to know their actual capacity, a huge job with this many cells. I am going to match cells based on their rest voltages, and cycle(charge/discharge) representative cells from each group. Sorta of an educated crap shoot. The BMS will balance the cells as much as their capacities will allow. One cant expect a perfect battery from used cells but for the money invested(less than $150 including the BMS) Im willing to gamble.
 

motortriker

New Member
Mar 5, 2012
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http://www.youtube.com/watch?v=XoIpsuCDkl0

This is how to test the cells. Notice a cell in parallel with another cell can be open.

Resting voltage testing would not show up the dead open cell in parallel with a good cell.

The time you take testing each cell and matching them in the pack will pay off later.

Put balance connectors on the pack so you can study the pack after it is built and to trouble shoot the pack.

The Hyperion 1420 hooked up to a computer display will show you clearly what is going on with the pack.

When all looks good then you can put a good bms on the pack.

Leave the balance plugs on the pack for future troubleshooting.

https://www.google.com/search?q=bui...Search&channel=fe&client=browser-ubuntu&hl=en

https://www.google.com/search?q=bui...ntu&hl=en#channel=fe&hl=en&q=solder+A123+pack

http://www.youtube.com/watch?v=vkDgoXikI_8
 
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silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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northeastern Minnesota
A couple of questions regarding the batteries. This is in reference to a current project for a hybrid trike with a gas engine and an older golden motor 36V pancake front wheel which I used with 3 12V. SLA batteries (which I hope are good enough to use initially).

The drawback to electric bikes for me is the cost of the batteries once you opt for something better than the SLAs, so your approach in building your own with used cells is of great interest.

Where did you find these used cells?

Is a different controller needed for these batteries? Mine is for SLA's...? Can the same charger be used as for the SLA's?

If I can use my original stuff then switching over to the better cells would be pretty inexpensive!

I know so little about this stuff it is pathetic, so any advise is appreciated. Once again Cannonball, you are blazing a new trail...
SB
 

cannonball2

Well-Known Member
Oct 28, 2010
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Thanks for the links Motortriker. I separated the cells that were paired by cutting the - tab. I could then read the cells individually. Cells with voltages 3.75 or over I assumed good(not best to assume I know) and soldered the tabs back together. Cells with lower voltages were charged then load tested on my charger noting the mah in the charge discharge cycle. I found all the cells to be of good capacity. I found one @ 3.15v that I figured done for. It actually charged up to 4.2v and returned better than 2500mah on the load test. Hoping for the best!
You are right it would be best to test each cell.

Hey SB Thanks for the kudos but folks been building these packs for years. My E bike kit was a 36v that was actually a 48v with a 36v charger, so I opted for 48v because of increased performance at a lower amp draw. Bought a 48v charger of course.
These cells were from reclaimed laptop batteries, they are genuine Sanyo. Still not super cheap around $75 and a possible crap shoot. They do read the voltages. Some sellers actually load test but at higher $$.
If using a BMS the SLA charger will work, as well as the controller. The BMS will also balance the cell groups. I bought a new set of SLAs which I want to be able to use so am making this bike able to easily accept both types.
Building the pack is kinda fun, you have to be able to solder well and keep up with what you are doing, but its not demanding.

What I have built is a 13 cell pack with 12s and 1p for 48v. It is a 10.2ah pack which is pretty good capacity. The BMS will limit the surge draw to 30amps with a constant max of 15amps. for 720w constant max and 1440w surge--if my figures are right, think so.

Hers a pic, it aint no thing of beauty, but its well assembled. Weighs just over 5.5 lbs and is 9.5x2.5x2.85 in. I will find a secure case for it. Am leaving the +/- wiring off until I assemble the Ebike which is next.
 

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cannonball2

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Oct 28, 2010
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See what I mean about keeping up with things! The cell in the middle of the pack closest to the ruler needs to be bridged and one in the next row right near the back as well as the next row front. Didn't affect the voltage of the pack, but it would have lost a good bit of capacity!! Long day with too many cells and a lot of soldering. All fixed now.
 
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paul

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Dec 23, 2007
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remember i am clueless to all of this cannonball and going to ask lots of questions, this is a great thread and educational to. what do you mean by the cell needs to be bridged?
 

cannonball2

Well-Known Member
Oct 28, 2010
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The pack is made of parallel 4cell sub packs that are [email protected] These are then joined in series to make a [email protected] "brick". I then assembled the 7.4 bricks into the main battery jumping 7.4v at a time til I reached 44.4v. I then added a 3.7v parallel 10.2ah pack to the last series cell to get 48.1v. When assembling 52 cell you get a little bug eyed and I neglected to join some of the + ends of the primary 4cell sub packs taking that pair out of the circuit. I got the voltage but not all the capacity.
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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northeastern Minnesota
If the sub cell packs are each 3.7 volts then ten of them would come to 37 volts. My controller is for 36 volts. Does the extra volt make any real difference?
SB
 

cannonball2

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Oct 28, 2010
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Colonial Coast USA.
I would think not SB, the packs will come off the charger @ close to 4.2v which is well over the 36v rating. The controller has a margin built in to allow for a fresh charged battery. Open the controller and look at the capacitor. I bet its a 60v. Which will allow either 36/48v use.
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Didn't see the first question. A BMS is a battery management system. It regulates the battery with in certain parameters on charging/discharging. Sets amp draw levels, cut off voltages, charge voltages etc. You could operate with out one but the batteries wouldn't get properly balanced on charging, could be overloaded and over charged/discharged. @ $40 it a deal!