Dewalt 36 volt batteries

[mustangman]

How much would you pay for a used dead battery pack? A computer or battery has a limited lifespan. I was just trying to point out that fuel cells are not economically sound at this time. With electronics (such as computers, cell phones) the the time frame for a new product to come to market can accurately be determined by Moore's Law( the co-founder of INTEL). I wish we could accurately predict when fuel cells will become cheap enough so we could afford to make the transition from PLEV to fuelcell LEV. I hope I did not offend anyone in my previous posts, my intention was to inform of the possibilities. I personally will start with a SLA system then upgrade to LiFePo4 as the battery price gets even more attractive. I can hardly wait for the affordable fuel cell eBike !!!  (if you build it, will they buy it? At what Price??)

[OneEye]

I don't think anyone has taken offense.  We're all tossing around the plethora of permutations one could have for electric bicycle commuting.  I'd say your contributions to the conversation have been right on target.  Mine too 

I wish batteries followed Moore's law.  I think they are improving at a rate closer to doubling
(capacity/energy density/total delivered power) every 1/2 century.  Some of the most promising technologies of the last few decades have really come with some significant gotcha's.

Another thing favorable to the LiFePO4 battery chemistry is it is not supposed to self-oxidize and lose capacity over time regardless of use.  I hope that claim bears out.  I hate that my two laptop batteries are DEAD DEAD DEAD after having very limited unplugged use.  Much of the LiIon chemistries eat themselves up regardless of charge state, or use, and lose much of their capacity within a few years.  Of course many users will replace their laptop within the 3-year life span of the battery, but I'm currently typing on a 2001 vintage model that still browses just fine.  It would be nice to be able to unplug and surf wirelessly, but I'm not about to spend $100+ to replace a battery on a laptop that is currently worth say $30 (although I doubt I would even have any takers at that price point)

[myelectricbike]

My tendency is to overreact... I'm not offended but possibly put off by being asked if I have found a good use for the TRS-80 Model I when I'm sitting at the Model II and the Model III is sitting next to me when what I really need is Internet distributed processing. 

LiFePO4 is certainly a great improvement over lead acid in many ways if you are willing to make the financial commitment but if you are going to do an improvement quest then you should focus on state of the art and look for ways to make it affordable like maybe a 10 watt fuel cell that you could make yourself and then another and another and another while just keeping an eye on LiFePo4 instead of doing it the other way around.

Not offended but maybe put off.   

Update on the Golden LiFePo4 battery pack...   Philip Yao reports shipping is on hold due to an issue with one of the packs so for the time being the Dewalt batteries appear to be the only way to go.

[mustangman]

 I am glad we seem to be on the same page.    I hate tossing out a perfectly good computer just because something "new" has come along. PALCAN is developing a fuel cell aimed directly for our segment of LEV's because the most air pollution is caused by short trips and the cost per Ah in this category.  Palcan has developed a 500 watt all the way to 5000 watt fuel cell. Please  take a look at their website as well as Ballards. Most fuel cell manufactures rate their output on 12 volts not 36 volts.   

[mustangman]

I have some new information directly from dewalt regarding their 36 volt battery packs:

         Subject
DeWalt Battery control module for DC9360 battery paks
 
 Discussion Thread
 Response (Jeff) 07/17/2007 03:40 PM
Hello mustangman, and thanks for using DEWALT's on-line support.

The control module for this battery pack is not available separately.

The amp hours of this battery is 2.4 amp hours or 2400 mAH. We do not have an estimated run time as this varies depending upon application.

Thank you for allowing us the opportunity to serve you. If your question remains unresolved or if you require additional information please update this incident.

Sincerely,

Jeff

 Product Level 1:  Cordless
Product Level 2:  Batteries
Product Level 3:  36 Volt
Category Level 1:  DEWALT
 

[myelectricbike]

If it has a control module then most likely there is a limit set on rate of charge and discharge. Maybe this is why there is so much interest in testing charge and discharge rates in the RC community.

[OneEye]

The battery pack does have a control module, and the R/C community has done some reverse engineering to figure out what exactly it does.  That is still a work in progress.  In addition to the pins that run through the control module, there are two spade connection slots that bypass the control module and are wired to the positive and negative end of the series of cells.  The negative end connection is fused at 15A so anyone who tries this for a 500W motor may want to use at least 2 parallel packs to give a fused 30A available current.  A number of e-bikers have bypassed the 15A fuse in the pack to allow for higher draws on individual packs.

The R/C community mostly tears these things apart and are only interested in the cells inside.  The R/C aircraft hobby is very interested in the available draw because they run these cells at 30A or more in their stunt planes while doing rolls, vertical climbs, and other "3D" aerobatics.  One of their attractions to the A123 cells is they can provide that kind of draw without killing the cells.  Some of the other lithium chemistries and even the NiMH and NiCad have very short cycle lives at high draws, so they have to provide more parallell packs.  These cells they can get away with only 1 or 2 sets of parallel cells (anywhere from 3S1P to 7S2P depending on the size of the model airplane)

For the e-bike community you can keep the packs intact because the pack weight isn't as critical as it is in aircraft hobbies.  The tool battery form factor is fairly convenient to an e-bike.  Keeping the packs intact you can still utilize the standard DeWalt charger.

[OneEye]

If you troll around the R/C forums you can probably pick up a control module from the inside of a pack for ~$10 by paypal.  They tear the packs apart and throw away anything that isn't a cell anyway.

[OneEye]

One of the folks on the R/C forums is a EE professor at some university.  He had his undergrads pull apart a hammerdrill and a battery pack to draw schematics.  I think he assigned them a lab exercise to build a new tool that could utilize the existing pack.  The control scheme and electronics in the drill were quite simple; most of the brains are already on the battery's control module.  Fortunately, you can bypass all of it to use as a simple e-bike power source.

[OneEye]

I ran across this post before, but didn't remember the author's comment in a later reply...

From:  http://gristmill.grist.org/story/2006/9/8/82015/17778

One battery is adequate for about 6 or 7 miles. I chose not to put them in parallel because the batteries in each pack are matched (within a few percentage of each other in charge) but it is unlikely that the batteries in each pack would match other packs and could back-charge. Using them one at a time is the same as using them in parallel since the current draw never seems to exceed a single pack's capacity. Turning a switch to connect a new battery when one goes dead is trivial and has the advantage of letting you know how much charge you have left, as I mentioned before.

I'm pretty sure the 6 or 7 mile range per pack is not motor-only, and the speed is left unstated, but this is from a user who rides on the hilly roads around Seattle.  Quite promising.  I wouldn't worry too much about paralleling packs.  The manufacturer's technical folks actually recommend putting cells in parallel, as it allows the stronger cells to protect the weaker ones and also spreads the current draw.

[OneEye]

http://endless-sphere.com/forums/viewtopic.php?t=1427

[mustangman]

 Well, according to tha article, I should get to know my local dewalt repair facility, and maybe, just maybe I could get my hands on some "defective" 36 volt battery packs and rebuild them myself!!! It would cut down on the cost of making a large enough batt pack to travel more than 5-7 miles at full power economically feasible. (buy a few and repair a few)   

[OneEye]

I was thinking the same thing.  From the 3 packs he got on his first visit there were still 19 good cells, only 1 shy of two full packs.  I'm going to visit my local DeWalt dealer to see if I can help them out by unburdening them of any bad packs they had to accept on warranty. 

I think the packs use a TORX security bit (the star shaped ones with a hole at the bit's center).

[mustangman]

You might have to pay a small amount of money since we are competing against the RCers who might also have the same idea of reclaiming some battery packs for their own uses. If I found a good source of packs, I would try to keep it silent since information like this travels fast through the grapevine.

[OneEye]

Just noticed this one at the first post on the page

How much would you pay for a used dead battery pack?

Too funny to pass up.

Hey, if you find a good source (and I don't) I'd be willing to pay shipping and handling for any dead packs you don't wind up breaking into.  I'm willing to reciprocate if the situation is reversed.

And before anyone asks...I don't think dead packs come with a warranty