Super Cheap Nicad Powertool Packs For SLA Replacement?

Yesterday while perusing my local Harborfreight store for a 18v nicad powertool pack to replace my old Ryobi pack that just died, I noticed Drillmaster 1.7ah Nicad packs on sale for $10.
http://www.harborfreight.com/cpi/ctaf/Category.taf?CategoryID=143&pricetype=
If like my Ryobi pack, they're sub-C's in a 14-S, 5-4-5 configuration. The Ryobi replacement costs $25 online. So I'm planning to pull the cells from this pack instead, swapping them into the Ryobi casing.

$10 per pack is $0.71 per cell -- significantly cheaper per AH than the $2.69 2.3ah sub-C nicad cells from all-battery et al:
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=418

An 8.5ah 36 volt, 30s4p pack for e-rides could be constructed for about $85 minus the charger(s). Of course each string would need to be charged separately, or separated with diodes, but still, this is significantly cheaper than even SLAs considering a 5-10 year service life. Some EV people have done the same thing with NiMH sub-C's.

I wish I knew what you were talking about

newbie electric rider said:

I wish I knew what you were talking about

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Better, cheaper and faster (theortically) than lead batts... by using NiCd tool batteries from the cheepo importer: Harbor freight tools.

Cheeper than getting bare-batts from the usual suspects.

Charging gets a little tricky.

:wink:

Tyler's translation is pretty good, but I'll go one step further.

My attempt:
Xyster found a bunch of cheap NiCd packs at Harbor Freight. They are sub-C's - which mean they are somewhat smaller than a standard alkaline "C" cell. Each cell in the pack is 1.7Ah (which is not much) and is 1.2V. He says that if these are like the ones that he has in his other pack, they are 14 cells in series (14s).

He then goes on to extrapolate from this 18V 1.7Ah pack, that one could make an 8.5Ah 36V pack by taking 8.5 packs apart ($85 from $10 packs? 36@8.5Ah from 14V@1.7Ah packs?). Why 8.5? I presume because it makes the math easier.

By taking all the cells out of... 8.5 packs... you could get 120 cells. These cells could be arranged as a 30s4p - 4 parallel packs of 30 series cells each. Nominal NiCd voltage is 1.2V, so 30*1.2=36V, then 4 parallel packs of 1.7Ah each gets you 6.8Ah. I'm not clear on the math here either...

But the point is good - that you could - if you felt like taking apart a bunch of drill packs - make a pretty good short-range bicycle battery pack fairly cheaply. But as Xy said, and Tyler translated, charging them would not be fun. NiCd packs can't be charged in parallel, so you'd need 4 36V NiCd chargers, or you'd need to wire up a circuit using diodes to enable you to use one charger.

Thanks for the jargon translation guys
And also the math error correction...excuse: I wrote it this morning, pre-coffee.

I just bought the $10 drillmaster pack. The cells seem to be comparable, 1.7ah Sub-C sized nicads, but there's 15 instead of 14 (assuming I can still count) and in a different configuration than my Ryobi.

The pack on the right is the new drillmaster; the one on the left the old Ryobi. Both packs are labeled "18 volts" -- but we know how that goes

Anyway, I'm off to try and reconstruct my Ryobi pack...saving $15 in the process (woo hoo!)

Thanks for the explanation, you guys are way to nice!

I'm pleased to report the Drillmaster --> Ryobi battery transplant procedure was completed successfully. The patient is recovering voltage on the Ryobi charger now. Due to the incompatible physical cell configurations, and the surgeon's general unwillingness to spend the rest of the day soldering, the patient suffered slight, not entirely unexpected disfiguration. After an initial period of recuperation and occupational rehabilitation, Mr. Ryobi will be permanently bound by duct tape, and a restraining device fashioned to keep him from falling out of his saw holster while in use.

Well-wishers may send flowers.

Good that you've shown the insides. Your old ones are Panasonic beauties which don't get much better than that & may be how they got away with one less cell. I'm thinking they probably sag less and/or have a flatter discharge. I would suspect they have a lower internal resistance & higher amp rating than the new pack which that extra cell is kind of a tell-tale sign, but maybe not. B4 investing too heavily you would need to do a load test to verify the max current you can get at 1.0 Volt sag so you can figure the minimum number of strings needed, if even 4 in parallel are up to it. Let us know how well these new ones hold up.

Get this Turbo: I was wrong on the cell count too (bad day for me, eh!). The original Ryobi pack is 15 cells as well; there was one extra stuffed up into the neck and covered by a black cap. The new, cheap pack charged fine and my reciprocating saw lives again! I don't think I'm going to invest in these as an ebike battery replacement -- maybe if I had the chargers already -- I was just tossing them out there as perhaps the cheapest way possible to build a new, better-than-SLA pack.

Hi Guys, I am thinking about building a extra battery pack that could go in the trailer I just bought. Would something like this be good? I would like another 48 volt one, my controller is 36 volt 20amp. I need extra range. Another quick question, if I upgraded my controller to a 72 volt one would my 406 handle more volts? And one more question, with the extra weight 100lbs, for the trailer, 80lbs for the bike (guess) 175 me, would that be putting dangerous strain on my forks for the dreaded complete front end watch my tire roll down the road, with a superman view of it in slow motion like failure. I am not looking for extra speed on the trailer, It is comfortable at around 30 km/ hours, anything beyond that just feels dangerous.

newbie electric rider said:

Hi Guys, I am thinking about building a extra battery pack that could go in the trailer I just bought. Would something like this be good?

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If you're OK with multiple chargers, one per each series-string, or plugging and un-plugging one charger multiple times, then I think these small ni-cads would make an excellent, inexpensive and long-lived pack about half the weight of SLA.

I would like another 48 volt one, my controller is 36 volt 20amp. I need extra range. Another quick question, if I upgraded my controller to a 72 volt one would my 406 handle more volts?

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4xx series easily handles 72 volts.

would that be putting dangerous strain on my forks for the dreaded complete front end watch my tire roll down the road, with a superman view of it in slow motion like failure. I am not looking for extra speed on the trailer, It is comfortable at around 30 km/ hours, anything beyond that just feels dangerous.

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I don't know.

Thanks for the reply, I was looking at your thread how you put together your lipo batteries , many pages and lots of detailed pics.(tyvm ) I am fifty / fifty to try something like that or just order another 48 v batery pack. The drawback for me in your system is the huge array of wires and chargers (people must really think you are a mad scientist in your neck of the woods lI am thinking when going on rides with the trailer and all the extra weight, it would be nice to have a lot of extra range (amps i think ), we have some beautiful bike paths around here, 100s of kms of them, and it is great activity with the kids and gf. Plus with the trailer can just load the extra batteries in the trailer. Maybe even just run a wire up from the trunk compartment and keep all the batteries in there when using the trailer.( in that configuration i would not be comfortable having lipos there just in case of some sort of accident/ fire, the kids are strapped in there. ) Any thoughts you might have on how to proceed would be appreciated.

newbie electric rider said:

Thanks for the reply, I was looking at your thread how you put together your lipo batteries ,

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Technically, they're lithium-ion (li-ion) laptop batteries, not lipo (lithium polymer). Same basic chemistry, different packaging. I got a good deal on them from all-battery.com at ~$3/per.
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1643

I am fifty / fifty to try something like that or just order another 48 v batery pack.

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A DIY pack is the best way for architecturally-minded people like me. The pack can be made in whatever shape best fits; cell choice is much better and usually cheaper; cells can be mixed-and-matched or replaced as necessary; partial-packs can be tacked-on to increase voltage and capacity, and the pack can be built to any size and spec.

The drawback for me in your system is the huge array of wires and chargers (people must really think you are a mad scientist in your neck of the woods l

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LOL. The highly parallel configuration has the advantage of great redundancy. Until I tore the pack down and tested the cells individually, I couldn't tell that two of the 15-cell subpacks were effectively 14-cell subpacks because one cell in each had a faulty solder connection.

I am thinking when going on rides with the trailer and all the extra weight, it would be nice to have a lot of extra range (amps i think ), we have some beautiful bike paths around here, 100s of kms of them, and it is great activity with the kids and gf.

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Same here. I love being able to ride for hours without a care as to how much power I have left. The excess capacity allows me the freedom to explore, and allows each cell to live a longer life as I almost never have to run the pack down below 50%. Mostly, I charge to 80%, and discharge to 50% -- about 10 amp-hours in the range preferred by the lithium-cobalt chemistry.

Plus with the trailer can just load the extra batteries in the trailer. Maybe even just run a wire up from the trunk compartment and keep all the batteries in there when using the trailer.( in that configuration i would not be comfortable having lipos there just in case of some sort of accident/ fire, the kids are strapped in there. ) Any thoughts you might have on how to proceed would be appreciated.

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A trailer opens up another set of possibilities as far as batteries, and is on my project list. If you're too uncomfortable with lithium cobalt (both lipo and li-ion), there's always the new, much safer 2nd generation lithium cells -- LiFePO4 (such as a123) and LiMn (such as emoli), or you could build a NiMH or Nicad pack.

You really present a very logical argument for building your own pack. Besides the satisfaction of doing it your self, I am really persuaded by being able to check each cell periodically, so they are balanced and have the best (for lack of a better word ) power band.
The diy Trailer battery project begins.