What's the best way to build a 123 pack these days

[ponobill]

There's a lot of information on the forum about packs, but a lot of it dates from 2007 or 8. It looks like 123 cells are pretty easy to get from China these days--at least it seems that way on ebay. I assume these are legit. I also assume folks are no longer disassembling dewalt packs to get them. Yes/No? I just ordered a couple of 48V 15AH packs with bms and charger from china via ebay, and I'm feeling a lot of buyer remorse even though they aren't here yet. The more I study here and elsewhere, the more it looks like A123 batteries are what I should be using. Fortunately I have some budget left.

What I have is a CatTrike Expedition with an Ecospeed mid drive. I've been driving it around the neighborhood making a general nuisance of myself with packs salvaged from two goofy, underpowered hub motor electric bikes I bought for the wife and I a year ago.

What I want is lots of capacity to deal with hills. I live in Hood River, Oregon, and there isn't anywhere I can go in any direction that doesn't require a chug up a steep hill.

So assuming the ebay 26650 A123 batteries are for real, I'd buy a hundred of them and build a couple of big packs. I'm thinking 48V which probably means 13 series and perhaps 4 parallel in two packs.

My questions are:
1. Does this sound rational
2. What BMS should I use. I'd want two I guess since I like the idea of two packs--one on each side of the trike
3. What charger

I have the Velociraptor controller from Ecospeed and the energy meter/speed thingy installed.

 

[texaspyro]

Unless you are a masochist with lots of experience and some high dollar welding equipment I'd talk to forum member cell_man. He is in China (but he's British and speaks passable engrish :lol and fabs A123 packs for a very good price.

 

[ponobill]

I've got lots of welding equipment (Tig, Mig, gas, etc.) but not the spot welding stuff I'd probably need. Sounds like sound advice. But what about the charger and BMS question?

 

[gblast123]

There are a couple of different solutions.. but none of them are really good and easy.. there seem to be a series of tradeoffs with time, money, and easy solutions

1) Easy route - spend the money and get a pre-made battery pack...expensive solution

2) Harder but practical - if a123 cells are really important, get the 32157 cells.. they run about $25 or less for slightly used cells but these have screw threads on the ends and it is easy to put together a nice pack.. no welding but be careful.. these have huge 40C discharge rates so a small mistake can cause a big problem.. they are about 8 Ah so 16 cells will give you a nice pack and 32 cells should give you the 15+ Ah solution.

The headways are a little cheaper but don't have a high C rate.. not good if you need a lot of power, but easier to work with.

3) Use dewalt battery packs and take out the cells.. there are threads here on how to just use the whole 28v or 36v battery pack with just a little welding. Not a bad solution but you will need to tinker and weld a good bit.

4) Buy cells, etc and weld your own.. not for the faint of heart and you need to be very very careful... you are looking at 20C discharge rates for the a123, 26650.. so small mistakes are not easily forgiven.

BMS - go to tppacks.com and get a 16s BMS from andy.. I would have it premade - about $200 and that should take care of your BMS issue for now..

If you need any other help, I am still somewhat of a rookie but I should be able to give you some guidance or names of people that I used or vendors that can help you.

David

 

[biohazardman]

Lots of good ways to build them. That written in 2007 and 2008 is still good info. I'm in Portland and we have plenty of hills here also.

A- It looks like 123 cells are pretty easy to get from China these days--at least it seems that way on eBay. I assume these are legit.

Some are some are not you have to be carefull with anything you buy from China as there are lots of imitations there.


B- I also assume folks are no longer disassembling DeWalt packs to get them. Yes/No?

I for one still get my a-123s (DeWalts) from the packs and solder the tabs on the packs together to get the voltage and AH I need expect many others do also.

C- I'm thinking 48V which probably means 13 series and perhaps 4 parallel in two packs.

At 3.3v nominal per cell 13 is a bit low on voltage at 42.9 you probly want 14 or 15 in series. I have done both 14 and 16 the latter preferred on hills as it pulls much better.

My questions are:
1. Does this sound rational

Yes

2. What BMS should I use. I'd want two I guess since I like the idea of two packs--one on each side of the trike

Not sure that you need a bms on board. In the 6K I have done with the LifepO4 batts I have not used a BMS for anything other than balancing the charge. My controller LVC does just fine at stopping me from over-discharging. If you fear damaging a few cells a simple LVC unit can be installed on the batts to monitor each cell.

3. What charger?

I have 5 chargers and 3 power supplies all werq very well at charging. Many are using the Meanwell brand of power supplies I have one also but my main charging unit is a 48V Vicor power supply putting out 52.7 for 14S packs. Both of these were purchased off of eBay. It is coupled to one of the early version 2.2 TPpacks BMS units, no longer available, so the packs with individual cell balancing wires are always in balance. The other two packs without the balance wires are not balanced all that often one stays near perfectly balanced on it's own the other sucks and I think after replacing six or eight weak cells it is finally doing better. Ask around TPpacks or any on the forum for the BMS thing for charging as it keeps things simple.

I have this charger for my 16S pack and it works great. Lots of ways of doing things.

http://www.evassemble.com/index.php?main_page=product_info&cPath=3&products_id=7

 

[myzter]

have you every thought of using a 12V high capacity booster pack switched in series with the controller output with a DPST switch ?

I have a controller with Conversion Efficency of 95%

and shown on the watt meter this is like 3-5 watts difference between straight battery to motor connection @ 12V

 

[MitchJi]

Hi,

So assuming the ebay 26650 A123 batteries are for real, I'd buy a hundred of them and build a couple of big packs.

Probably a bad assumption.

I also assume folks are no longer disassembling DeWalt packs to get them.

Wrong.

I'm thinking 48V which probably means 13 series and perhaps 4 parallel in two packs.

For 48V you should use 16s. Explained here:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=2498

2) Harder but practical - if a123 cells are really important, get the 32157 cells.. they run about $25 or less for slightly used cells but these have screw threads on the ends and it is easy to put together a nice pack.. no welding

Since the A123 M1 223ah cells are selling for about $4-$5 each thats an expensive way to do it. BTW where can you buy those cells?

3) Use dewalt battery packs and take out the cells.. there are threads here on how to just use the whole 28v or 36v battery pack with just a little welding. Not a bad solution but you will need to tinker and weld a good bit.

4) Buy cells, etc and weld your own..

Almost everyone takes the packs apart and uses the individual cells. You can easily assemble the cells without welding or soldering if you prefer:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=17912

 

[ponobill]

OK I'm confused. Why would folks be buying Dewalt Packs to take apart. lowest price I've seen is $70 bucks for the 28v pack which must have 8 batteries. You can buy 8 A123 26650 M1A batteries on eBay for $72 with tabs welded top and bottom and the seller will weld them in about any configuration you want for $.02 per tab.

On the other hand I've been somewhat tempted to use the Dewalt packs as-is in a 4 parallel, 2 serial array which would give 56 V. I figure I could buy 16 of the packs and have one set on the charger all the time, using standard dewalt chargers. I'd also switch over all my cordless tools to use these lithium packs. It would be a little bulky on the bike, I guess, but the instant swap benefit seems worthwhile.

What am I missing?

 

[MitchJi]

Hi,

OK I'm confused. Why would folks be buying Dewalt Packs to take apart. lowest price I've seen is $70 bucks for the 28v pack which must have 8 batteries. You can buy 8 A123 26650 M1A batteries on eBay for $72 with tabs welded top and bottom and the seller will weld them in about any configuration you want for $.02 per tab.

On the other hand I've been somewhat tempted to use the Dewalt packs as-is in a 4 parallel, 2 serial array which would give 56 V. I figure I could buy 16 of the packs and have one set on the charger all the time, using standard dewalt chargers. I'd also switch over all my cordless tools to use these lithium packs. It would be a little bulky on the bike, I guess, but the instant swap benefit seems worthwhile.

What am I missing?

• 
  1. Dewalt packs and cells pulled from Dewalt packs are selling for about $4 per cell on ES. Example:
  http://endless-sphere.com/forums/viewtopic.php?f=9&t=20280
  

  I have approximately 200 M1 A123 2.3 ah 26650 cells for sale, with tabs $6/cell.
  
  I am offering them for $6 each (US funds), plus shipping to your location.

  http://endless-sphere.com/forums/viewtopic.php?f=9&t=20280&start=15#p320654
  

  Screw it. I'm selling them all. I need a CA and these are cluttering up my shop.
  
  I have approximately 400 on hand. 100 tested and ready to go, 300 (after removing the dead and lame ducks) still in packs.
  
  I am going to get them ready, and sell them. I'll decrease the price steadily until they are all sold, my timeframe is the next 6 weeks or so.
  
  Price is solid at this time, $4 untested (but bad ones removed) and $5 tested (capacity at 5c test written on cell).

  
  2. Are you sure the Cells from Ebay are really A123 cells in good condition?
  
  3. Using the packs doesn't work well. Check the care and feeding thread.

 

[webfootguy]

OK I'm confused. Why would folks be buying Dewalt Packs to take apart. lowest price I've seen is $70 bucks for the 28v pack which must have 8 batteries. You can buy 8 A123 26650 M1A batteries on eBay for $72 with tabs welded top and bottom and the seller will weld them in about any configuration you want for $.02 per tab.

On the other hand I've been somewhat tempted to use the Dewalt packs as-is in a 4 parallel, 2 serial array which would give 56 V. I figure I could buy 16 of the packs and have one set on the charger all the time, using standard dewalt chargers. I'd also switch over all my cordless tools to use these lithium packs. It would be a little bulky on the bike, I guess, but the instant swap benefit seems worthwhile.

What am I missing?

It is mostly a few trade offs going on. The DeWALT packs are heavy (2.4 lbs) while the 8 cells inside only weigh 1.23 lbs. If you can get by with only a couple of packs and use the interface board (which limits discharge to about 25 amps / pack) and you are ok with using the stock 1 hour charger, then the packs make a great solution. But, if you want a denser pack with more cells and don't want to use the stock charger, then keeping the cell packs with their built in BMS does not make much sense. You do more work but you get a better solution in the end. The high C rate (power density) of the A123 cells is what make them attractive for small setups.

 

[The Mighty Volt]

Lots of good ways to build them. That written in 2007 and 2008 is still good info. I'm in Portland and we have plenty of hills here also.

A- It looks like 123 cells are pretty easy to get from China these days--at least it seems that way on eBay. I assume these are legit.

Some are some are not you have to be carefull with anything you buy from China as there are lots of imitations there.


B- I also assume folks are no longer disassembling DeWalt packs to get them. Yes/No?

I for one still get my a-123s (DeWalts) from the packs and solder the tabs on the packs together to get the voltage and AH I need expect many others do also.

C- I'm thinking 48V which probably means 13 series and perhaps 4 parallel in two packs.

At 3.3v nominal per cell 13 is a bit low on voltage at 42.9 you probly want 14 or 15 in series. I have done both 14 and 16 the latter preferred on hills as it pulls much better.

My questions are:
1. Does this sound rational

Yes

2. What BMS should I use. I'd want two I guess since I like the idea of two packs--one on each side of the trike

Not sure that you need a bms on board. In the 6K I have done with the LifepO4 batts I have not used a BMS for anything other than balancing the charge. My controller LVC does just fine at stopping me from over-discharging. If you fear damaging a few cells a simple LVC unit can be installed on the batts to monitor each cell.

3. What charger?

I have 5 chargers and 3 power supplies all werq very well at charging. Many are using the Meanwell brand of power supplies I have one also but my main charging unit is a 48V Vicor power supply putting out 52.7 for 14S packs. Both of these were purchased off of eBay. It is coupled to one of the early version 2.2 TPpacks BMS units, no longer available, so the packs with individual cell balancing wires are always in balance. The other two packs without the balance wires are not balanced all that often one stays near perfectly balanced on it's own the other sucks and I think after replacing six or eight weak cells it is finally doing better. Ask around TPpacks or any on the forum for the BMS thing for charging as it keeps things simple.

I have this charger for my 16S pack and it works great. Lots of ways of doing things.

http://www.evassemble.com/index.php?main_page=product_info&cPath=3&products_id=7

Hi there, why are the balance taps on the battery in that photo so heavy?? For Balance taps, those are massive.

 

[GGoodrum]

Hi there, why are the balance taps on the battery in that photo so heavy?? For Balance taps, those are massive.

They look to be about 18-gauge, which I think is just fine, as long as they aren't too long. Smaller gauge wire have more resistance which will skew the voltages the shunt circuits see. This can affect the accuracy of the balancing.

-- Gary

 

[The Mighty Volt]

Hi there, why are the balance taps on the battery in that photo so heavy?? For Balance taps, those are massive.

They look to be about 18-gauge, which I think is just fine, as long as they aren't too long. Smaller gauge wire have more resistance which will skew the voltages the shunt circuits see. This can affect the accuracy of the balancing.

-- Gary

Maybe it is just the photo, they look fatter than that. Cheers.

For the OP:

I am building an A123 battery. What I have done is build 24 sub-packs, each consisting of 10 A123 in parallel, for 22-23Ah. I then connect each pack in series for 72v.

 

[katou]

The picture shows blue wires gathered into one group inside a black cover which runs down to the battery, I assume this is done to help manage all those wires.

If you look just at the black, it looks like 4 ga wire, which would be huge. I can see why you might see that.

The individual wires (blue, one per channel of the BMS) look to me about 18 ga too.



I am the seller that Mitch referred to in his post at $4/cell. I am out of cells right now. I may have some in the future... or not. These things are sort of a windfall. $4/cell seems to be the going price.

The only member that seems to have a semi-regular supply is Dr. Bass, and his are usually snapped up quick. (although with John in CR sated, the rest of you may have a better shot)

People are using single cells because it's cheap, fairly easy to build a pack, and the chemistry is very, very hard to kill. Trust me, if you saw some the cells I've seen, that tested out just fine, you'd be amazed.

Out of 50 packs I've torn down so far, I've only chucked one without even testing. It looked like it had been in the bottom of a bucket of mud for a month. Part of it was, I didn't want to even touch it. Blecch.

I want to try the Konions because some users report zero need for balancing (hence no BMS other than LVC) but I'm fine just with the A123's for the forseeable future.

On the other hand, if there was a lipo charger that plugged into a wall, and would do the 20s that I need (without modification), I might be drawn to the Dark Side...

 

[biohazardman]

Lots of good ways to build them. That written in 2007 and 2008 is still good info. I'm in Portland and we have plenty of hills here also.

A- It looks like 123 cells are pretty easy to get from China these days--at least it seems that way on eBay. I assume these are legit.

Some are some are not you have to be carefull with anything you buy from China as there are lots of imitations there.


B- I also assume folks are no longer disassembling DeWalt packs to get them. Yes/No?

I for one still get my a-123s (DeWalts) from the packs and solder the tabs on the packs together to get the voltage and AH I need expect many others do also.

C- I'm thinking 48V which probably means 13 series and perhaps 4 parallel in two packs.

At 3.3v nominal per cell 13 is a bit low on voltage at 42.9 you probly want 14 or 15 in series. I have done both 14 and 16 the latter preferred on hills as it pulls much better.

My questions are:
1. Does this sound rational

Yes

2. What BMS should I use. I'd want two I guess since I like the idea of two packs--one on each side of the trike

Not sure that you need a bms on board. In the 6K I have done with the LifepO4 batts I have not used a BMS for anything other than balancing the charge. My controller LVC does just fine at stopping me from over-discharging. If you fear damaging a few cells a simple LVC unit can be installed on the batts to monitor each cell.

3. What charger?

I have 5 chargers and 3 power supplies all werq very well at charging. Many are using the Meanwell brand of power supplies I have one also but my main charging unit is a 48V Vicor power supply putting out 52.7 for 14S packs. Both of these were purchased off of eBay. It is coupled to one of the early version 2.2 TPpacks BMS units, no longer available, so the packs with individual cell balancing wires are always in balance. The other two packs without the balance wires are not balanced all that often one stays near perfectly balanced on it's own the other sucks and I think after replacing six or eight weak cells it is finally doing better. Ask around TPpacks or any on the forum for the BMS thing for charging as it keeps things simple.

I have this charger for my 16S pack and it works great. Lots of ways of doing things.

http://www.evassemble.com/index.php?main_page=product_info&cPath=3&products_id=7

Hi there, why are the balance taps on the battery in that photo so heavy?? For Balance taps, those are massive.

Sorry got sick so been out of it fer a while. Balance taps, red on pack 2, are 18Ga lead wire flexible stuff. Thick insulation makes them look massive though they are not. Just trying to choose some wire that would take a bit more abuse than some of the thin 22-26Ga stuff I have purchased from China. Bundled blue wires on the BMS and other battery are 18Ga also but not near as pliable as the red ones that I used on my second battery pack. Flexible is good when you have to move it around and I prefer it over the stiff wire I used on pack build 1 and the BMS.