The care and feeding of a123-based packs...

Gary, Seeing how you are into bikes, what do you think about stretching a cut inner tube over your pack stick's body for more protection? You could even watertight seal this with that boot goo you light with a flame and drip on it?
Jeff K. "Deep Cycle" project
 
jeffkay said:
Gay, Seeing how you are into bikes, what do you think about stretching a cut inner tube over your pack stick's body for more protection? You could even watertight seal this with that boot goo you light with a flame and drip on it?
Jeff K. "Deep Cycle" project
Click to expand...

That's an interesting idea. I might give that a try. My favorite covering is the heavy rubberized shrink tubing that Batteryspace used to sell, but no longer does now. Here's what the last bits of this stuff that I have looks like:

Rubberized%20Shrink%20Wrap.jpg


I have searched high and low for another source for this stuff, which shrinks up so that it ends up being about 1/16" thick. I'll give a free a123 4s4p kit to the first person who can tell me where to buy some more of this. :)

-- Gary
 
Sorry Gary, I caught that I had typed "Gay" after I sent it... Anyway, the inner tube concept is pretty cost effective. I think the sporting goods stores sell that goo I was talking about to repair wader boots. Let me know if you make one. My pack is too big (well i guess I could use a car inner tube).
Jeff
 
Gary, I think your spring based packs are cool but be aware of problems down the road. I had a "clamped springy neoprene" based pack on "Deep Cycle" for a year. It performed well. Later, when I was disassembling it to build a soldered pack, I found that moisture had got in (condensation?) over time and started to creep into the contacts. This is kind of like when you find an old flashlight with corrosion. I know the corrosion is from leaking electrolyte but maybe the moisture plays a part. Perhaps one should take apart the packs built with your system at some interval for inspection/cleaning/maintenance--which is one nice feature, that you can get the cells out. Also, looseness in the pack could make for some hot spots and losses.
Jeff K. "Deep Cycle" project
 
jeffkay said:
Gary, I think your spring based packs are cool but be aware of problems down the road. I had a "clamped springy neoprene" based pack on "Deep Cycle" for a year. It performed well. Later, when I was disassembling it to build a soldered pack, I found that moisture had got in (condensation?) over time and started to creep into the contacts. This is kind of like when you find an old flashlight with corrosion. I know the corrosion is from leaking electrolyte but maybe the moisture plays a part. Perhaps one should take apart the packs built with your system at some interval for inspection/cleaning/maintenance--which is one nice feature, that you can get the cells out. Also, looseness in the pack could make for some hot spots and losses.
Jeff K. "Deep Cycle" project
Click to expand...

This is actually my second or third go-around with this construction technique. The earlier version simply used round-head screws as the contact points, and although the packs that I have recently torn down that used this method didn't show any signs of corrosion, there were a few connections that had worked loose a little bit. My latest version uses brass rings on one side, and nickel-plated battery springs on the other, and everything is compressed down very tight, to the point you can't twist the blocks of cells. I don't think corrosion will be an issue, and I believe using these in high current applications will be a lot better than relying on four tiny spot weld points that you have if the DeWalt tabs are used. I went on a ride yesterday that had multiple peaks of 100-105A, and not one of the packs had even a warm spot. :) Mechanically, these are about as solid as you can get, and no solderjoints or welds breaking apart to worry about.

I'm going to look into the innertube idea. As for sealing, I have also used Plasti-Dip for this purpose, which works great as a sealant. I'll look into this boot goo stuff you are talking about as well.

-- Gary
 
Hey Gary,
Have you tried McMaster-Carr for the heat shrink? They seem to have a good selection.
JJ
 
Does anyone know of a BMS or balancing board for 20 cell a123 pack?
For my trials bike (motorcycle) I finally settled for 66V packs (charge to 72v).
The packs don't stay balanced, so I periodically remove all the batteries and hook them up in parallel.
It is kind of a pain, as you can imagine. I built my own packs of 72v @ 6.6ah and 11ah.
However, they are 20 cells in serial and not intercell connected between strings.
I connect the serial strings at either end to achieve a parallel connection.
Space on the bike has been difficult, so I strap to the top frame.
I charge with a 72v, 13.7A power supply. On the bike, I set the low voltage to 54 V, so no worries about over discharging.

The bike goes about 22-24mph flat out, but is used for off-road trials competition.
Gearing is approximately equivalent to 2nd on the gas powered motorcycle..
You can check out some of last years point of view videos at ecotrials.com if you are interested.

Thanx in advance for any help you can provide.
 
Yes, I saw that, but it is not the heavy-duty rubberized stuff I was getting. Still, it is certainly the widest shrink tubing I've seen available anywhere.. :)

-- Gary
 
i know that batteryspace used to sell them and they stopped , well you know that too, you bought it from them but did you check lately

http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=306
 
Great info. Great expanation too.
I found the a123 M1 battery spec sheet here (the URL is one character too big to fit on my window width... it's a .pdf ):
http://a123systems.textdriven.com/product/pdf/1/ANR26650M1_Datasheet_MARCH_2008.pdf

My novice question is, why disassemble the Dewalt pack for the M-1s at the expense of loosing the Battery Management System that comes with the pack? Why not just plug them into something? I'm obviously missing something.
Thanks.
John
 
EVnow! said:
My novice question is, why disassemble the Dewalt pack for the M-1s at the expense of loosing the Battery Management System that comes with the pack?
Click to expand...

I may be mistaken and am a complete novice too, but I've read around here and heard (from a local service center guy) that the DeWalt BMS are complete junk.
 
Another thing to remember is that the other "feature" of the BMS on the Dewalt is the low voltage cutoff. You will not have this capability when you use these packs without a bonifide Dewalt tool plugged in. So, couple a weak cell balance circuit, with no low voltage cutoff at the pack level, then stick a crapload of them in parallel in a pack and look out! You can damage a pack someday. The A123 cell is kick ass and they give you all the power they have as long as they can, but the catch is, when they near depletion, the voltage at the cell level falls like it was off a tabletop and you can kill a cell if you are not careful.

The bright side? They will send you a new pack for free, all you pay is shipping one way.

You can protect yourself somewhat by getting a Cycle analyst and setting the Low voltage cutoff pretty high, that way, you don't run the packs down so far and can avoid killing a cell, at the expense of range. Another trick is to have a couple extra Dewalts that you can leave on the chargers all the time and rotate them out with 2 in your bike pack. that way, the charger has a chance to balance the packs. E.g. I had a 6p pack on my bike with 8 Dewalts total, I also had 4 chargers so i constanly rotated 2 out. this way, I could be fully up in one hour too.
 
pwbset said:
EVnow! said:
My novice question is, why disassemble the Dewalt pack for the M-1s at the expense of loosing the Battery Management System that comes with the pack?
Click to expand...

I may be mistaken and am a complete novice too, but I've read around here and heard (from a local service center guy) that the DeWalt BMS are complete junk.
Click to expand...

The Dewalt BMS boards are crap.

Use a CycleAnalyst as an LVC, or buy one of goodrums LVC boards.

Then either charge with single cell chargers, or use a big charger and some kind of discharge balancer.
 
kbarrett said:
The Dewalt BMS boards are crap.
Click to expand...
That's for sure.

kbarrett said:
Use a CycleAnalyst as an LVC, or buy one of goodrums LVC boards.
Click to expand...
Not the CA pack-based LVC. A123 cells need a per-cell LVC like goodrum's or you'll eventually ruin some cells. A123's have too steep an end of charge curve. The higher the voltage of your pack the less reliable a pack-based LVC will be. I lost 3 cells after my first month of commuting with a 20s4p A123 pack using a CA as LVC.

kbarrett said:
Then either charge with single cell chargers, or use a big charger and some kind of discharge balancer.
Click to expand...
Or talk Gary and Bob into finishing their charge management board.
 
GGoodrum said:
rf said:
...Or talk Gary and Bob into finishing their charge management board.
Click to expand...

Patience is a virtue, my friend. :wink:
Click to expand...
I've come very close to ordering another ten Voltphreak's single-cell chargers to speed things up. I guess this means I should hold off ...

Will the new CMS tie my shoes too?

Richard
 
rf said:
Will the new CMS tie my shoes too?

Richard
Click to expand...

Damn near...

I'm helping Gary with a new design. We hope to test soon. I anticipate there will be bugs in the first iteration (there always are), but hopefully nothing major. It's just a matter of time.

I have a pile of A123's waiting for this too. :wink:
 
Can this be similar to above but all made?

Goto the interactive presentation.

http://www.modenergy.com

If not can a bunch of single Li-Ion batteries be put together to make a big one to power a car?
 
schlepers said:
Can this be similar to above but all made?

Goto the interactive presentation.

http://www.modenergy.com

If not can a bunch of single Li-Ion batteries be put together to make a big one to power a car?
Click to expand...

No.

Looks like a startup looking for markets. Wrong kind of Lithium batteries. Suspect too expensive at
this point, and no consumer availability, far as the web page seems to convey. They're in search of
a market and using old tech by our standards. Some of their ideas are what we're dealing with here.
But we appear to be ahead of them. They don't mention the charging advances dealt with in this
list at all.

Gary and Richard and this discussion ARE the cutting edge for smaller applications.

:)
 
I have to agree with rf here. I can't even understand what actual "product" they offer ?

Best,

Don Harmon
 
rf said:
Not the CA pack-based LVC. A123 cells need a per-cell LVC like goodrum's or you'll eventually ruin some cells. A123's have too steep an end of charge curve. The higher the voltage of your pack the less reliable a pack-based LVC will be. I lost 3 cells after my first month of commuting with a 20s4p A123 pack using a CA as LVC.
Click to expand...

I can believe that ... the CA tends to be a bit slow to notice what's going on. It also can't monitor individual 3.3V cell banks. Once you get past 2.7V, the A123s slide into the death zone fairly quickly.

I'm using one of goodrums boards, so hopefully I won't be buying a lot of replacement cells.
 
Time for me to confess ... I killed my first a123 cell in my Nirve chooper e bike. :(

As described here ... http://endless-sphere.com/forums/viewtopic.php?f=6&t=4160#p62310 ... I use sticks of 12-a123 cells in series in each fork tube.
I charge each stick with a standard 36V SLA charger (float charge = 42.5V and max charge = 44.5V and max I = 2.5 amps)
These bats are installed in the forks of my Nirve chopper (2 x 36V = 72V) and I never balanced the cells in about two months of much usage.

Well ... Just a few days ago I noticed one fork tube was 3.3V lower than the other :shock: so I emptied the fork bats (took 2-minutes)
and checked each cell V. Sure enough one cell was 0 volts (funeral hymn). Removing the cells from the 'bad' tube 11 cells each measured exactly 3.32V and 1 cell measured 0.00V.

Just for fun I charged the other tube to full (what I call full) and as soon as the charger shut off (V hit 44.5V) I removed those and measured those 12 cells too.
Right after charging the 'good tube' cells measured 3.43, 3.51, 3.49, 3.63, 3.50, 3.58, 3.49, 3.48, 3.41, 3.50, 3.47, and 3.45 (Sum = 41.96).

Golly! Guess it's time to balance all my cells to 3.6V independently!

As much as I would like to have balancing wires installed, there is no easy way to fabricate a stick cell with 11 wires for balancing while 'in-the-tube'.
 
You have just experienced why low-voltage protection neds to be done at the cell level, not the pack level. This is especially true with a123 cells because they hold their voltage up so well that there is almost no warning that the cell has reached the end of capacity. In the span of just a few seconds, the voltage will drop quickly. If you don't catch it, it will go all the way to zero, like yours did, and the cell is dead.

I'm sorry, but unless you figure out how to either individually charge each cell, or figure out a way to balance them, you will likely continue to have this problem where a low cell can die. Having an LVC capability would at least keep the cells from being damaged.

-- Gary
 
Gary i agree with you about the lvc and most everything i know i learned from you especially with knucles setup with only 1p version but why do you think it would have made a difference with single cells charging
 
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