Charging NiCds?

Batteries, Chargers, and Battery Management Systems.
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Link   100 MW

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Charging NiCds?

Post by Link » Dec 28 2007 6:17am

I'm planning to use some NiCds in my project. The pack will be make up of six Black and Decker 18V power tool packs (hey, they were free).

They will be 2s3p (yes, yes, negative delta, yada, yada, I know) for a total of 36V 3.6Ah.

I need a decent charger. I took apart one of the ones they came with, and was like, "ZOMG! WTF!?". The whole of the charger consisted of a transistor, a diode, and a resistor. I'd rather not use them for fear of killing my batts prematurely.

If any of you could recommend me a charger, be it 18V or 36V, that would be great. If it had a temp sensor, that would be even greater.

Keep in mind, cost is at a premium. The whole setup is cheap and I'd like to keep it that way :wink:.
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Ypedal   100 GW

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Re: Charging NiCds?

Post by Ypedal » Dec 28 2007 7:10am

Surf ebay for RC chargers.. usually powered by a 12v source ( got a stash of 12v SLA's gathering dust ? ) or a 12v regulated power supply..

Should be a large variety of them available.

3paralell and only 3.6ah ??

edit to add : The BD chargers, as simple as they look, are low rate chargers, Nicad can tolerate over-charge to an extent, and these chargers as so slow they don't harm the cells unless left plugged in for days.. Once you start to feel the pack warm up.. unplug the charger.
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deardancer3   10 kW

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Re: Charging NiCds?

Post by deardancer3 » Dec 28 2007 10:32am

Depends on what typoe of charging you are going to do.

two different methods, but there are more.

If you are going to need quick road charging, you need a amp hour meter and/or a a smart charger.


If you think you can make your day's travels without a fast road charger, then you can go cheaper and just trickle at home each night.
or
You can use a cheap 36v NIMH smart charger, then just add the 10k NTC thermistor to the side of your pack.


I might go with a road amp hour meter (because it helps with managing batteries, energy and trouble shooting, about $50) and then have a stupid charger (maybe the one in your hand with a few different charge rate limit resistors and a household timer which you already have.

On the road, you know how much battery you have used, set the charger rate and timer to almost top off, continue on.

At night set timer to again take you to about 80%, then put then charger on 1/30c for the rest of the time to next ride or 12 hours max. on the timer.
cheap but lots of intervetnion.

Or just get a 36v NIMH Nex cell , shop the net. use a current splitter on the road, switch packs at night. unless you find them cheap enoug to buy two. (I think I saw a guy in LA with 1.5 amp NIMH 36v Nex cell for ~$30 apiece last year)
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Johnbear   10 kW

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Re: Charging NiCds?

Post by Johnbear » Dec 28 2007 11:08am

From my experience with nickel based batteries (and I see you are trying to keep the cost down), I would not spend too much money. I have probably spent over $1500 in nicads /nimh of various manufacturers and the performance is very poor. However you cannot beat the free price of the packs! All the best. I have bought chargers from both http://www.batteryspace.com and ebikes.ca.
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Link   100 MW

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Re: Charging NiCds?

Post by Link » Dec 29 2007 6:00am

Ah, screw it. I'll rewire the B&D chargers. Only doing this till lithium gets into my price range, anyway.

Now, how am I gonna charge six packs in parallel? Think I could just parallel up the chargers?
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Beagle123   10 kW

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Re: Charging NiCds?

Post by Beagle123 » Jan 01 2008 2:46am

Hi Link,

Just remeber that you can't charge NiCads in parallel.
Avoid BMSBattery like the plague. (I read that somewhere :)

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Link   100 MW

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Re: Charging NiCds?

Post by Link » Jan 01 2008 5:30pm

Blah, I know. Schottky's should fix that, though. Right?

Doesn't matter, in any case. I'd use a Mini-Fit Sr. connector (or whatever a trip to my local electronics candy shop turns up) to connect them up for charging/discharging. That or a PCB with some relays on it...

Dammit, I gotta figure out a set of connectors to standardize all my plugs with...Powerpoles for power and Micro-Fits for signal? Hmm...
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monster   100 kW

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Re: Charging NiCds?

Post by monster » Jan 01 2008 9:25pm

i recently nuked a nimh battery when charging in parallel so watch out. i use a transformer-rectifier-lightbulb to charge my batteries and it works well. you can re-wind a transformer if you cant find the right voltage for you.

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Link   100 MW

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Re: Charging NiCds?

Post by Link » Jan 02 2008 7:36pm

Yeah, I know. Luckily, the transformers for the chargers are wound to give me exactly 21.75V. Or so it says on the case. I've got five of those.

Did they explode? :twisted:
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monster   100 kW

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Re: Charging NiCds?

Post by monster » Jan 04 2008 4:55pm

nay no explosion. but 150*C hot and smelly.

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