Author Topic: 9.6v battery charger  (Read 9188 times)

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Offline jah1282Topic starter

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9.6v battery charger
« on: December 02, 2006, 05:49:36 PM »
I'm learning to ask before purchasing!
New question:  What charger would you recommend for me to charge my 9.6v 1400mah NiCad battery with?

Offline DomoArigato

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Re: 9.6v battery charger
« Reply #1 on: December 04, 2006, 01:31:44 PM »
I'm not really qualified to make a recommendation, but I'm using an old 9.6 volt NiCad battery pack, and I saw chargers for sale at a lot of different places.  I saw some at radio shack.  The local hobby store here had one too.  There are also a ton on ebay and all the online battery stores.  Most of them tell you it's for a 9.6V NiCad batterypack.  Goodluck, I hope that helped a little.

Try these:
http://www.megabatteries.com/item_details.asp?id=13707&cat_id=58
http://www.radioshack.com/product/index.jsp?productId=2062124&cp=2032056.2032147&parentPage=family

Offline JesseWelling

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Offline dunk

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Re: 9.6v battery charger
« Reply #3 on: December 04, 2006, 05:47:13 PM »
or if you are like me and always end up with different sizes of battery pack you can try making your own charger.
to charge a battery you want to hook it up to a power supply, +ive to +ive and -ive to -ive and monitor the current flowing into the battery with a multimeter (set to read Amps).
now, before everyone goes and toasts their batteries note the following:
this method will work for NiCad and NiHH but DO NOT use it for Lithium Polymer batteries without first reading up on their complicated charging scheme.

so, on to charging NiCad and NiHH batteries,
you want to first look at the mAH (milli Amp Hour) rating of your battery pack.
let's use jah1282's 9.6V 1400mah as an example.
to charge this pack you would want to connect a power supply which is a few Volts higher than the battery pack. eg a 12V supply.
connect the positive terminal on the power supply to the positive terminal on the battery.
now connect the negative terminal on the power supply to one lead on your multimeter and the other lead to the negative terminal on the battery.
make less current flow into the battery by putting a resistor in series with the multimeter.

have a look how much current is flowing into the battery using your multimeter.
for example with jah1282's1400mAH means the battery can deliver 1400mA for one hour.
to recharge it you want to deliver the same power back into it (plus 20 - 40% for the inefficiency of the whole system)

so with jah1282's 1400mAH battery, 140mA were going into it you would charge it for a bit over 10 hours.
if 280mA were going into it you would charge it for a bit over 5 hours.
you could probably charge it in an hour with 1400mA but you would want to be carefull that the batteries were not over heating and that you stopped within an hour.
generally speaking, the slower you charge your battery, the better life expectancy it will have.

ok, it's not quite that simple.
i suggested using a resister in series to limit the current flow.
the problem is, as the battery charges and it's voltage gets closer to the voltage of the charger you are using, less current will flow.
using the method i described you would have to manually change the value of the resister several times during charging.

the solution?
use a LM317 voltage regulator as described here: http://www.dprg.org/projects/1999-05a/.
the LM317 keeps the output from the charger circuit a set voltage above the battery so the same amount of current always flows.
it's a really simple circuit to set up.

nice hu?

so, although it's possible to fast charge packs like this, without designing some sort of thermal shut out i'd recommend keeping to trickle charging. (ie, slow, all day charging.)
aim for about 14 hours at 0.1 x the mAH rating of the battery for NiCads.

NiHH on the other hand can be trickle charged almost indefinitely with very little damage.
i have a robot that lives in it's charging cradle 90% of the time.
it is constantly charging at about 0.08 x the mAH rating of it's battery and i haven't seen any real degradation of the cells for over a year.

have fun!

dunk.

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Re: 9.6v battery charger
« Reply #4 on: December 04, 2006, 07:53:03 PM »
two more comments . . .

if you are ever going to charge lithium batteries dont use dunks method . . . burning your hand isnt cool  ;D
for any other battery, just make sure it doesnt heat up too much.

if you are really serious about robotics, i recommend making an investment into a smart charger that JesseWelling linked to . . . they are 6x more expensive but let you charge many different types/voltages of batteries at optional speeds.

(note: make sure you can plug the charger into the wall and not just off a car battery)

Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #5 on: July 23, 2007, 07:14:04 PM »
Does the chargers voltage matter as much?
I have a 6v 1400mAh Ni-MH battery pack and a DC adapter that outputs 12v at 100mA. Would I be able to use this as my charger?
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Offline dunk

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Re: 9.6v battery charger
« Reply #6 on: July 24, 2007, 02:53:11 AM »
the voltage of the charger has to be greater than the voltage of the battery.
i would reccomend charger that can supply at least 140mA for a 1400mAh battery but using a lower current will just take longer so it is possible.
be sure you don't use more current than the charger (12V adapter) can supply or you will damage it.

dunk.

Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #7 on: July 24, 2007, 09:31:52 PM »
be sure you don't use more current than the charger (12V adapter) can supply or you will damage it.
What do you mean? Are you talking about for charging? Or do mean using it to power a circuit that requires more than the adapter can supply?

BTW when I hook up the adapter to my battery, the (+) from the adapter goes to GND on the battery right? Do I need to put a resister in series or anything?
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Offline dunk

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Re: 9.6v battery charger
« Reply #8 on: July 25, 2007, 03:12:57 AM »
Quote
What do you mean? Are you talking about for charging? Or do mean using it to power a circuit that requires more than the adapter can supply?
both.
if you use your 12V adapter to supply anything with more than it's rated 100mA you risk damaging the 12V adapter.

Quote
BTW when I hook up the adapter to my battery, the (+) from the adapter goes to GND on the battery right?
NO!! this will burn.
read the thread. it explains this.

Quote
Do I need to put a resister in series or anything?
read the thread. it explains this.

dunk.

Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #9 on: July 25, 2007, 11:45:25 AM »
oh crap... sorry Dunk :( I guess I either got ADD after I read that or just didnt pay attention when I read it :( sorry


-EDIT-
I did what you said Dunk. I hooked up the GND on my Battery to GND on my adapter and then I left (+) open so I could have my DMM complete the circuit. To test the amperage I set my DMM to read up to 10A(because your supposed to go from highest setting to lowest until you get your readings), which has an idle display of "0.00", and touched one lead to the (+) from my adapter and the other to (+) from my battery and got "0.00" still. But whenever I set it to the next lowest setting("200m"), which has an idle display of "00.0", I get "1" which based on the documentation from this url means its over ranged. Does this mean that I need a different DMM? :'(

I feel so friggen helpless as of late  :-[ :( ???
« Last Edit: July 25, 2007, 12:50:52 PM by HDL_CinC_Dragon »
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Offline dunk

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Re: 9.6v battery charger
« Reply #10 on: July 25, 2007, 02:05:10 PM »
Quote
oh crap... sorry Dunk Sad I guess I either got ADD after I read that or just didnt pay attention when I read it Sad sorry
heh. no problem. sorry you caught me at a grumpy time of morning.


hmm. multimeter weirdness.

so i'd expect a current over 200mA but less than 10A to still show up on the 10A scale.
(200mA = 0.2A)
i doubt if you need a different multimeter.

it's hard to make out from the picture on the link you posted but on my meter i have to move the position of the leads if i want to use the 10A scale.
maybe yours is the same?

try experimenting with a few resistors and your multimeter to see if you can read current over 200mA but below 10A.
connect a high value resistor across a battery.
V=IR
or written in english:
Voltage = Current * Resistance

eg.
3V across a 100ohm resistor would give 0.03Amps (30mA)
3V/100ohm = 0.03Amps

(be carefull you don't connect your meter to too high a current while it is switched to too low a setting or you will blow it's fuse.)

good luck.

dunk.

Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #11 on: July 25, 2007, 09:45:17 PM »
ah ok... so i need to find a 64ohm resistor... >_< (9v/64ohm = 140mA)

thanks for the help dunk :)
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Offline dunk

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Re: 9.6v battery charger
« Reply #12 on: July 26, 2007, 02:50:47 AM »
Quote
ah ok... so i need to find a 64ohm resistor...
no. not for the charging circuit.
V=IR is only true for a resistor over a single power supply.

i was only suggesting this so you can test your multimeter.

for your charger circuit you will have 2 power supplies, the voltage of one will be constantly changing (as the battery charges) so V=IR will not hold true.

you will not be able to charge the battery with a single resistor because the value of the reistor you would need will change as the battery charges. (read the post....)

dunk.

Offline elixier

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Re: 9.6v battery charger
« Reply #13 on: July 27, 2007, 02:58:23 PM »
good work Dunk
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Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #14 on: August 01, 2007, 03:10:39 PM »
Hate to HiJack this thread but would This be the best charger for my 6v 1400mAh NiMH pack? If im not mistaken, Id say it is... but Id rather ask people who know what theyre talking about. The only concern I had was "Charging Current 0.9A for battery packs with capacity from 1100mAh -2200mAh. For 2000mAhpack, charging time is 1 hour." Is that ok for my battery?
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Offline Admin

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Re: 9.6v battery charger
« Reply #15 on: August 04, 2007, 09:23:23 AM »
Batteries are rated for some maximum charging current rate . . . check the datasheet.

Then make sure your charger does not supply a current higher than that.

If your battery heats up while charging, that means the current rate is probably too high.

Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #16 on: August 04, 2007, 03:53:59 PM »
Ok my data sheet says the max peak charge rate is 1A.
so I guess im good to get that one since it maxes at .9A

sry for the curt response but im in a hurry! :) catch you guys later
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Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #17 on: August 21, 2007, 07:43:08 PM »
Ok I got my charger the other day and when I look on the sheet that came with my battery it says I should discharge it to about 1/10 capacity before charging it for the first time to "wake it up". So basically it says discharge my battery to about .6v before charging for the first time. Should I do this? Or can I just charge it now? Ive got an LED being powered directly by the battery right now with my DMM leads hooked up to the leads from the LED (the leads from the LED are stuck directly into the female end of my battery wire) and it says right now 1.78v. Its slowly going down though, like .01 volt every 2-3 minutes or so.
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Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #18 on: August 21, 2007, 08:25:30 PM »
Ive decided to start charging.

Battery:
OnlyBatteryPacks.com
6 volts
1400mAh
NiMH

Charger:
Tenergy Universal Smart Charger
.9A - 1.8A switch (.9A selected)
fuse in series in the wire

Its not gunna blow up right? I dont want that to happen....
« Last Edit: August 21, 2007, 08:26:02 PM by HDL_CinC_Dragon »
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Offline Admin

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Re: 9.6v battery charger
« Reply #19 on: August 21, 2007, 08:51:31 PM »
Quote
Ok I got my charger the other day and when I look on the sheet that came with my battery it says I should discharge it to about 1/10 capacity before charging it for the first time to "wake it up". So basically it says discharge my battery to about .6v before charging for the first time. Should I do this? Or can I just charge it now?
Hmmmm Ive never heard of that for NiMH, only NiCAD . . . but if the instructions say do it, I guess just do it . . .

Just monitor the battery occasionally to make sure it doesnt overheat. It should take I think 2 or 3 hours to recharge at that rate? Id say NiMH is the safest battery type out there, I wouldnt worry too much.

Offline Gertlex

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Re: 9.6v battery charger
« Reply #20 on: August 21, 2007, 10:29:05 PM »
Charger:
Tenergy Universal Smart Charger
.9A - 1.8A switch (.9A selected)
fuse in series in the wire

Its not gunna blow up right? I dont want that to happen....

I've got that same charger... though I think 7.2 to 12 V is it's range. Too lazy to go down in the basement and check  ;)

Used it for a handful of charges of my 7.2v 3200mAh batteries and it hasn't blown up, heh.

(BTW, got my batteries and charger off ebay as a single item... not seeing any downsides to this)
I

Offline HDL_CinC_Dragon

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Re: 9.6v battery charger
« Reply #21 on: August 22, 2007, 06:36:40 AM »
Yeah it charged pretty quickly, about less than an hour I think. Charged to a full 7 volts and lots of amperage lol. Only started feeling warm to the touch shortly after the charger light went green (meaning it was fully charged and was now 50mA trickle charging)


no 'splosions or anything which is good... I like 'splosions but theres a time and a place for that, and this is not it lol
« Last Edit: August 22, 2007, 06:37:32 AM by HDL_CinC_Dragon »
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Offline TrickyNekro

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Re: 9.6v battery charger
« Reply #22 on: August 22, 2007, 03:47:47 PM »
And if you want to use Li-Po batteries, it's a good option, but need advanced electronics...
You need a MCU and a smart battery charger...

Li-Po batteries are used is cell phones and are good for power up electronics... Two packs of them and you've got 7V2... Perfect for the BS2 I'm using...


If you want to make a start google: DS2760 and Free Sample it!!!! (you need to be a member of Maxim so register!!!)(it isn't relevant but you can free sample from Analog Devices,too. I have ordered two gyros and two accelerometers!!! You just need to make a student form!!!)

They will last hours and the DS2760 has an embed ADC for voltage and temperature!!!
Have FUN!!!

Regards, TrickyNekro,
Greece
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

 


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