Dewalt 36 volt batteries

[erdurbin]

Has anyone heard of using the dewalt 36v li-ion batteries? I think they are rated for 2.3ah. I saw a setup somewhere online where a guy had 3 of these on a 3-way switch = 6.9ah. Whenever a battery would get low, he would flip the switch to the next. They advertise 1500-3000 life cycles, with an average of 2000. If I used and recharged these everyday, I am looking at an average of 5 years for the batteries (and I don't ride everyday). They are about $110 for one, with a charger around $35. They only weigh 2.4 lbs. a piece equaling 7.2 total lbs. of batteries.

Rough estimate of cost
3 batteries = $330
2 - 1 hour chargers (home and work) = $70
Total = $400
average 2000 miles a year.
batteries last 5 years = 10000 miles on one battery pack potentially
=$.04 a mile for batteries alone

SLA cost
200-500 recharge cycles (one year of use)
my cost was $85 for 3 12ah x 5 years = $425
10,000 miles
charger included with kit
= $.0425 a mile

This is a rough estimate and I may be way off since I have not been riding my e-bike setup for more than a month. I am going from other forums and what people say about the longevity of the batteries.

I am just looking for an alternative to my heavy SLA's and when they die, I probably will be looking into these dewalt batteries very seriously.
Plus, only 7.2 lbs of battery and one-hour recharge per battery is nice. If I got 3 chargers, I could be ready to go in 1-hour.
I am not sure what the range would be, but I read somewhere that one battery could be good for about 6 miles.

Any thoughts?

If these go down in price next year when I replace my SLA's, I will be even better off.

[OneEye]

I've been watching the dewalt batteries myself as a possible battery option when I buy a goldenmotor kit; see my post regarding cutoff voltage for the controller.  The controller cutoff voltage seems to be one of the few obstacles to using the dewalts as a power source; you could potentially miss out on a lot of the pack's stored capacity.  myelectricbike is reporting a cutoff voltage programmed into the controller at around 31.5 volts.  The dewalts are really only 33V to start with, and have a recommended low-voltage cutoff down near 22V.  Depending on the current draw you might get shorted a significant amount of capacity unless you can reprogram or trick the controller to allow voltages down to near 22V.

Folks with 4 dewalt packs are reporting in the neighborhood of 20 miles pedal-assist range.  I have also seen a motor only range reported on the order of 6 miles for a 2-pack.  It might be higher for your use, because he was using them in series to power a 72V motor and it sounds like he was running at a higher top speed (~25mph?).

Durability on these batteries is reportedly amazing.  One guy ran a continuous charge - discharge test on a cell at a 30A draw (13C) and the cell still had 80% of its rated capacity at the end of 1050 cycles.  Lower discharge rates should allow for more cycles.

You can actually wire your batteries together to work with one charger if you get ambitious.  It doubles the recharge time, but they still get charged rather quickly.  Search for "aerorider" and "dewalt" on Google.  David wired 5 packs together for his.  He bulk ordered some connectors and still has some to sell to other users who are interested in paralleling their packs together for charging.  There are threads on visforvoltage.net and rcgroups.com discussing the dewalt batteries for non-tool usage.

Let us know when you take the plunge and set your bike up for operation on them.  I'd love to see what your actual range per pack ends up being and how well it cooperates with the controller.

-Mike

[myelectricbike]

Do you have a picture of the Dewalts?

[OneEye]

http://www.dewalt.com/36v/

Skip the intro, click on battery/charger.  There is a picture there.

This guy on VisforVoltage has a bike built around 4 dewalt packs and a "Golden Island" 400W hub motor... wonder if there is any similarity to the goldenmotor 500W made by Golden Island Machinery?

http://visforvoltage.net/member-vehicle/25-36-volts/769-electric-hybrid-bicycle-using-four-dewat-36-volt-nano-phostphate-lith

Might be worth contacting him to find out more specifics on range, terrain, and where he got his motor and controller.

I'm assuming the original poster has already seen http://gristmill.grist.org/story/2007/6/1/1287/76804, but I'll link to it from here for anyone else to take a look.  The guy has several other posts on the same forum, and one of them is where the reported 6-mile range is given by a user (he initially quotes 6-km for a 2-pack, but later corrects to 6 miles)

-Mike

[myelectricbike]

What does the warranty look like?

[OneEye]

Good question.

If you buy the batteries as part of a tool pack, it might be covered under a 3yr warranty/1yr service contract/90day money back guarantee the tool comes with.  You can get 2 batteries and charger as a kit for ~$275 or so (with hammerdrill and carrying case included at no extra charge ) on ebay.  I don't know if the warranty is tied to an authorized retailer.  If warranty is a major concern you can check on the battery coverage by chatting with the folks at 1-800-4-DEWALT (1-800-433-9258).  It is hard to say whether use in an e-bike will automatically void the warranty on a tool battery, but you might want to throw some sawdust at the drill before trying to get the battery replaced under warranty 

The folks at the RC forums don't seem to care much about warranty -- they rip the packs apart and use the individual cells wired up in various series/parallel combinations to meet their flight needs.  They are much more interested in how they perform in use.  They've been burned by extremely short cycle life of LiIon and Li-Polymer cells in the past.  There is at least a core of enthusiasts who have been won over by these batteries.

-Mike

[mustangman]

   If the DeWalt batteries are indeed 2.3 Ah, it would take over 6 packs to equal 15 Ah! ( 15 Ah / 2.3 Ah = 6.5 Packs) Each pack is going for approx. $100 dollars on Ebay including shipping.  Unless someone used these batteries for their trade such as contractor, it would make little since to go this route since a golden Battery pack of the same size(36v 15Ah @ $472)would cost potentially less and give more performance than the Dewalt system.

[OneEye]

Agreed.  For the 15Ah capacity pack sold by goldenmotor you will come out with a significantly better price.

Depending on the user, one may not need the range provided by 15Ah.  If sized to the desired range, the DeWalt system could be cheaper in total, albeit with less capacity.  Considering the typical SLA pack seems to be about 12Ah (since carrying much more weight seems to be out of the question) and SLA is usually only run to ~80% depth of discharge, this is similar to about 4 packs.  Some folks have survived with 7Ah SLA packs (the "standard" range pack for some motor kits), which would be equivalent to about 2 1/2 packs, so either 2 or 3 depending on how far you need to go.

Another consideration is the longevity of the battery pack.  Depending on the formulation and the way it is manufactured, a LiFePO4 battery may or may not have an extremely long life.  The claims by the DeWalt cell manufacturers have been backed up by user punishment tests.  I hope the same is true of the pack sold by Goldenmotor, but I don't know.  Does anyone have some 3rd party data on the cells used for the Goldenmotor pack?

If one were to buy enough DeWalt packs to cobble together a 15Ah system (the 6 packs you mention) it would be able to put out the same performance as the goldenmotor pack.  The A123 cells in the DeWalt packs are rated at 20C and have been put through user punishment tests at 13C with good results.  The disadvantage is the do-it-yourself assembly and the $600 price tag for those 6 packs.

In summary, I am agreeing with you.  I hope the goldenmotor packs grow the same reputation these DeWalt cells seem to have picked up.  If they do, the only decision factor between the two becomes whether one needs 15Ah at a discount, or a smaller capacity at a higher incremental cost (with the DIY hassle thrown in the mix just to keep life interesting.

-Mike

[mustangman]

  Mike, I agree with your post, but it never fails that you think that you have enough batt power to get to your destination only to end up pedaling the rest of the way!  The Dewalt packs contain  a123 batteries(a123racing.com or a123.com) The RCers break apart these dewalt pack because it is cheaper than buying the batteries individually. I totally agree that the a123 batteries have been proven to perform. The only person on this forum that possibily could shed more light on this subject is myelectricbike. He eluded that he has a 36v 15Ah pack and knows what the actual run time and approx. recharge time. When I try to cobble together a project like this one, It seems never to work out to my advantage.     Anyone else want to add their experiences ??

[myelectricbike]

Nope, sorry, I don't have a LiFePo4 pack yet - only the authorization to sell them and I have not yet sold any. I have asked for a sample Golden pack in order to give you guys a report but please understand that I'm in a learning mode myself as to the cost and technological benefit and I'm learning a lot of this stuff by monitoring and interacting with you. My own personal interest, however, is centered around fuel cells rather than battery technology although for an ebike application they are not yet stand alone but remain interdependent.

[OneEye]

I'll continue to agree with you MustangMan.  It is certainly an equation of leg power, battery power and how far you need to go.  How far you can realistically go on a DeWalt battery pack is going to be a significant concern.  How much is that reduced to when there is a headwind is another concern.  How much extra pedalling will you be forced to do if you make a detour to a store on the way home is yet another concern.

Maybe when the price of an e-bike suitable fuel cell system is in the right ballpark...

Ah, wishfull thinking for future days.

-Mike

[mustangman]

    Ballard currently has a fuel cell that produces 1200 watts of power, but the price at the present time is very prohibitive. PLEV's (plug-in Light Electric Vehicles) such as electric bikes will benefit the most with the advances in fuel cell technology. The time frame for fuel cells to become economically viiable is anywhere from 2 to 5 years, maybe sooner if oil prices continue to rise. It always takes time for the market to gear up for new tech. (remember the price for the first computers, $3000-5000 per unit what know cost $500-1500)  

[myelectricbike]

As for comparing computers how much would you pay for one of those $3,000 machines now? Except as an antique they are worthless. If you include the difference in computing capacity in your evaluation then today's computers would be worth $3,000 but cost $10 -$3,000.

[OneEye]

Along the same lines as other PLEV concepts it will probably be most efficient to pair the right fuel cell witht the right battery system.  Size the fuel cell to provide enough power to maintain 20mph "on the flat" (I'm just guessing here, maybe 200W continuous?)  Pair that up with the right battery system for those 30A bursts during startup, acceleration and hills.  That should give you a nice combination of range and performance.

A pair of Jadoo's N-gen (100W 12V) at $1K each, a few extra capacity canisters at $850 a pop, and a fueling station at $600, we'll throw the DC/DC boost converter in for free...  Hmm, that's 20 lbs of power plant (sans battery) $4,300 and we're only up to the equivalent of 36V/20Ah.  A bit short of infinite range, but we're working on it  

[myelectricbike]

I sent um an email. Maybe they have something in the 25 to 85 watt range to extend the range of post office home delivery vehicles that could be adapted to an ebike.