nicad batterys and charger

[SmAsH]

hi guys, ive been sourcing a battery pack and dont really want to pay like $25 for a 6v yet (im poor, live with it!)
could i just connect 5 1.2 rechargeables in series and use that?

but my main question is for charging them. i have an ac adaptor that puts out 6V@500ma. i know it is definatly not safe to charge at these levels, is there anything that i could use that limits current down to like 75ma-100ma?
and id like to use a fuse (dont want any pesky fires starting now do we? id look like an idiot just after 200 people died in fires ) i know ill just use a 150ma fuse?

so to sum up my questions:
what can i use to limit current?
is it safe to chain batterys in series and charge them if they're ni-cad?

[HDL_CinC_Dragon]

resistors limit current
the current rating on adapters is just their maximum before they die
you should generally charge a battery with at LEAST 1v more than the battery is rated for
If you run a battery in opposite directions it become a constant resistor

take a 12v battery and a 6v battery, hook them up + to + and - to -. The 6v battery becomes a 6v resistor meaning it will always resist 6 volts.

very tired so I wont explain in detail cuz im about to pass out on the keyboard.

[SmAsH]

ok then, drunk pass out or sleep deprived pass out? anyways, nighty night dragon and thanks for the help.
also, with a voltage regulator is it as simple as connecting like so

    unregulated v----gnd-----reg out?
also, where would i connect ground to if this is a stand alone circuit? negative? and where do the -V go (in and out)?

and because i didnt want to start a new thread for this:
i have an old laptop that i got from my sister for free, would this be good for running anything? the specs are absolute BEEP. im currently running win98 on it.

[Trumpkin]

Check in the data sheet of the voltage regulator to see how to connect it. This is usually how you would connect one

i have an old laptop that i got from my sister for free, would this be good for running anything? the specs are absolute BEEP. im currently running win98 on it.

First step is to get ubuntu on it, then make a robot with it!

1k posts

[Soeren]

Hi,

you should generally charge a battery with at LEAST 1v more than the battery is rated for

For NiCd's, the End of Charge Voltage should be 1.40 to 1.45V/cell (exact voltage depends on manufacturer, but 1.40V is safe).
5 cells will then need 7.0V End of Charge voltage.

To charge in such simple way, max. current should be limited to C/5  (where C is the capacity in mAh) or lower.

If you run a battery in opposite directions it become a constant resistor

take a 12v battery and a 6v battery, hook them up + to + and - to -. The 6v battery becomes a 6v resistor meaning it will always resist 6 volts.

Reversed batteries (or cells) doesn't become resistors! They negates the potential difference with the amount of voltage they hold.

Reversing a cell in a battery of rechargeables, there's nothing constant to watch. The reversed cell will first discharge rapidly, reaching 0V and then be charged in reverse, which is a sure way to destroy them.

Incidentally, that's the sole reason for the End of Discharge voltage defined to be somewhere between 1.1V and 0.9V per cell (depending on who defines and on the current drain the battery sees). Single cells can handle being used all the way to 0V.

[pomprocker]

and because i didnt want to start a new thread for this:
i have an old laptop that i got from my sister for free, would this be good for running anything? the specs are absolute BEEP. im currently running win98 on it.

I have a 15 year old laptop that came with windows 98, and I loaded a stripped down version of Windows XP called TinyXP. You can find a bit torrent, or you can make your own using nLite and your own copy of windows xp:


http://www.nliteos.com/nlite.html


Your old laptop will be able to run XP without any major memory requirements

[SmAsH]

ill have a look for tinyxp. and trumpkin how would i go about making a robot out of it?

[Trumpkin]

Read this http://www.societyofrobots.com/member_tutorials/node/140 You could do something similar. Although I suggest you use some kind of linux distro. (I hate Windows)

[SmAsH]

ahh yes the butler robot, i just thought about using as a remote control 'controller' platform with all those simple trnasistor circuits flying around

[Admin]

i have an ac adaptor that puts out 6V@500ma.

A NiCad battery can easily take that charging rate. Probably 5A actually - check the battery datasheet for charging rates!

Just remember to fully drain your NiCad battery before recharging or else you get memory effect and the battery loses life.

[SmAsH]

i have an ac adaptor that puts out 6V@500ma.

A NiCad battery can easily take that charging rate. Probably 5A actually - check the battery datasheet for charging rates!

Just remember to fully drain your NiCad battery before recharging or else you get memory effect and the battery loses life.

wow, one the battery it says normal charge 50ma 15hrs
quick charge 120ma @ 120ma for 4-6hrs?