Sign in to follow this  
Followers 0
mikkel

Cordless Drill battery (was car battery)

16 posts in this topic

Cordless Drill battery (was car battery)

I have not bin lucky to find any old UPS system so now I work with 18 v batteries from an Cordless Drill. (I have fore of them and I intend to connect them parallel at least 3 of them)

I have tested with one of this batteries on an older laptop that uses 19.5 v and it worked fine with out any converters or anything. Now for the real setup it is an other laptop An IBM ThinkPad 390. This laptop is only 16 V and 3.36 A. At the same time I want a couple of PC speakers to get power from the batteries they are 8.5 V and 0.6 A. Lets start with the laptop. It seems I can not just by a convert for this specific task in the big electronic shop that we have here in Copenhagen. They have only (maybe) some resistance that I can use. But the question is do I really need anything for the laptop (it is only 2 V in deference and the battery probably lose some V as it loses energy)?

The speakers is different they are only 8.5 V. What can i do her? Can I use some kind of resistance, will that wast a lot of energy, can I by such resistance or maybe converters cheaper online?

Thanks

/mikkel

0

Share this post


Link to post
Share on other sites

Well a 2 v difference probably won't mean much... but the 2x for the speakers... figure on blowing them pretty quick...

Here in the states cordless drill batteries are made up of many smaller cells, each soldered to the next in series... mostly you'll find 'C' cells. Probably the same in Europe considering everything is made in China or Japan now anyways...

open the battery case up... and make a tap at the 16 volt point... and another one at the 8.5 volt point... Leave the rest of the cells wired up so you can use the regular unmodified cordless charger...

Something like this...

15 cells = 18v in a Dewalt cordless drill

so 18 / 15 = 1.2 volts per cell

therefore...

from ground... count up (16 /1.2) or 13th or 14th cell to get the 16 volt tap...

from ground count up to the (8.5 / 1.2) or the 7th cell... for the 8.5 volt tap (close enough)

Might just be easier to charge them up and probe with a multimeter until you find a voltage you can use.

The batteries are just soldered together... so just solder on an extra wire for the taps... Now... I'm not sure but I think you could still wire the cells up in parallel... experiment first... make sure it doesn't over load and go boom. but you'll just need to wire the grounds, the 8.5 and the 16 volts to their respective partners...

And the whole time, you can still use your regular charger and no power wasting resisters... Maybe could put a slide switch on it.. so when they get weak, you can add another 'cell' by changing the tapping points..

Have fun... and don't lick your fingers after playing with the individual cells....

Edited by PurpleJesus
0

Share this post


Link to post
Share on other sites

Super cool PurpleJesus. If that is right I am more Lucky than I have hoped. Your explanation seems very pedagogical I can see it all for me. Now I am looking forward to open the battery. Thank you for taking the time.

/Mikkel

0

Share this post


Link to post
Share on other sites

Be careful what type of batteries you used though...

Laptop batteries are usually Lithoum ion and are designed for a low current drain...Car and drill batteries are designed for a short but high current I believe

0

Share this post


Link to post
Share on other sites
Be careful what type of batteries you used though...

Laptop batteries are usually Lithoum ion and are designed for a low current drain...Car and drill batteries are designed for a short but high current I believe

Real good point... the resistance of the battery itself could be part of the power regulation circuit... If they differ greatly could be a problem... Hell go for broke... When your ready to try the lap top out... wire your multimeter in so you can watch how many amps come out... Don't let it get away. If theres a problem, hopefully it'll only blow the fuse in the multimeter and we'll have reason to rethink this.

but I think it will work... because lithium batteries are used in cordless drills now too... They are just an optional battery pack... no special drill or charger now...

but yeah... wire a fuse in it... maybe two.... just to be safe.

(btw- any regular car fuse will work Like a 10amp radio fuse would be good I think.... wink wink nod nod)

Any other ideas anyone??? Speak up before we fry his laptop.

//edit

pedagogical

Had to look that one up..

Thought I'd share the irony. Thanks.

Edited by PurpleJesus
0

Share this post


Link to post
Share on other sites

If you can solder and read a schematic why not build your own DC-DC converter... it can be simple or as complicated as you are willing to make it.

If you go that route you can choose the easy but slightly less efficient way(linear regulators) or the hard way (a switcing regulator).

I would go with a linear if you never did anything like this before.

Google for datasheets for these parts... most will have application notes, sample circuits and calculations to do just what you want.

LM338K (5A adjustable reg) for the lappy

LM7809 (9V 1A fixed reg) close enough to 8.5V for the speakers

LM7808 (8V 1A fixed reg) close enough to 8.5V for the speakers

jameco.com is good to get shit from.

LM7812.pdf

0

Share this post


Link to post
Share on other sites
If you can solder and read a schematic why not build your own DC-DC converter... it can be simple or as complicated as you are willing to make it.

If you go that route you can choose the easy but slightly less efficient way(linear regulators) or the hard way (a switcing regulator).

I would go with a linear if you never did anything like this before.

Google for datasheets for these parts... most will have application notes, sample circuits and calculations to do just what you want.

LM338K (5A adjustable reg) for the lappy

LM7809 (9V 1A fixed reg) close enough to 8.5V for the speakers

LM7808 (8V 1A fixed reg) close enough to 8.5V for the speakers

jameco.com is good to get shit from.

LM7812.pdf

That would be better. Yes. Way better... but If I remember the other car-battery post correctly ... Dude is broke and trying to do this on the cheap... Ie... no money for parts.

Mikkel, are you old enough to work construction?? Maybe a summer job for an 'alarm systems installer' would net you some goodies... (ever see all the crap in a 'fire alarm' room???)... Have the right attitude and they'll probably unload allkinds of 'junk' on ya... stuff good enough to still work.. just not good enough to sell to clients.

0

Share this post


Link to post
Share on other sites

Just this litle info. The batteries are Ni-HM. 18 v, 2 A.

/Mikkel

0

Share this post


Link to post
Share on other sites

You could make a linear type regulator from scavenged parts. You'd need probably just an old TV and an old PC power supply. I'd do it like this: get one of the huge power transistors from the TV (the flyback driver transistor would be a good choice). Get a +5v regulator from the PC power supply. Connect the regulator so you get a constant +5v from the 16v power packs. Use the +5v through a variable resistor to vary the output of your transistor (use a volt meter to determine the correct output setting). This will get you closer to the range you need (there will still be sort've loose tolerance -- the +5v regulators are usually +/- 0.05 v or less in my experience, and that fluctuation can cause more significant change in the power transistor) but it'll be better than running straight 16v into a 14v application, and probably keep you from letting the magic blue smoke out of your speakers for the 8.5v side.

I've used transistors driven like this for all of the fan and lighting controls in my desktop PC. Those big old flyback transformers can handle some serious current -- you can find out just how much by looking up the manufacturer's datasheet.

0

Share this post


Link to post
Share on other sites
Just this litle info. The batteries are Ni-HM. 18 v, 2 A.

/Mikkel

Glad to see ya posting.. i was worried you might have fried your laptop...

Ni-HM? or Ni-MH?? nickel metal hydride? Those are good batteries... better life then Ni-cad's

Is the series of batteries 18v or is each cell 18v wired in parallel??

Systems Glitch.. I like the idea of tearing an old TV apart.. do you have any pics of the project? Maybe a new thread for that.

btw... Mikkel... if you go the TV route make sure that capacitor in the back of the TV is fully discharged... else it could easily kill you if you touch it the wrong way. There is enough power there to weld a screwdriver to the capacitor terminals... no kidding.

And I was thinking of how to safely test this project on the cheap.... remember the car fuses I was talking about earlier?? Well... what if you cut the power line leading to the laptop, wire in a fuse, then connect it to a known GOOD powersupply and work yourself up in the smallest increments (1amp, 2,3,5,7.5,10 etc) available until you DON'T blow a fuse... Now you know which fuse rating is correct for the laptop... then try it with your batteries and if the fuse blows we know it won't work and hopefully haven't fried the laptop.

Crazy idea... See if you can find some appliance/stereo repair shop near by... maybe they'll like you enough to mentor ya with some hands on electronics training... A mom and pop shop is what your looking for ... a Corporate shop is probably a dead end. who knows, you might end up with a job. You seem to have the drive...

0

Share this post


Link to post
Share on other sites

For the fuse rating, you could either connect a multimeter in series with the laptop if it has an amp mode (make sure it's DC AMPS not milliamps), or read the max output value on the power adapter. They usually have either an amperage or wattage rating. It's easy to figure amperage from wattage -- just divide by voltage, if it's a single voltage power source.

0

Share this post


Link to post
Share on other sites

There is a lot of ideas now I cant follow op at all many of the electric specific terms I don't know what means but TV is easy for me to get everyone in Denmark want flat screen TV and trough there old TV out. I also have an old laptop power supply that I could live without

>Is the series of batteries 18v or is each cell 18v wired in parallel??

each cell is only 1,2 v and they are connected + - + -. I haven't tried withe the laptop but just from my filing and thinking I don't think it differs much from a laptop battery. As I sad before I have tested this with an (even) older laptop of mine and it worked just fine. The firs solution to open the batteries and take out at the right point is very much the easiest. To learn to build electronic tools would be very interesting, but i have so many things I would like to do also, that I think if I could get around it for now it would be better.

/Mikkel

0

Share this post


Link to post
Share on other sites
There is a lot of ideas now I cant follow op at all many of the electric specific terms I don't know what means but TV is easy for me to get everyone in Denmark want flat screen TV and trough there old TV out. I also have an old laptop power supply that I could live without

>Is the series of batteries 18v or is each cell 18v wired in parallel??

each cell is only 1,2 v and they are connected + - + -. I haven't tried withe the laptop but just from my filing and thinking I don't think it differs much from a laptop battery. As I sad before I have tested this with an (even) older laptop of mine and it worked just fine. The firs solution to open the batteries and take out at the right point is very much the easiest. To learn to build electronic tools would be very interesting, but i have so many things I would like to do also, that I think if I could get around it for now it would be better.

/Mikkel

I think Systems Glitch was talking about using the old CRT TV's... I don't know jack about the newer flat screens..

So... have you tried powering the laptop off of the battery 'tap' yet?? I'm not sure if you said you did or didn't.

0

Share this post


Link to post
Share on other sites

OK got new ideas.

Firs no I haven't tried yet with the IBM laptop. I have plenty of time with the project so why hurry.

A small correction to my earlier mail. Each cell is 1.5 v not 1.2

A general question

In a serial connection the volt value of each cell will be added to the total amount of volt

what happens to the Amp in a serial connection?

In a parallel connection the volt value will stay the same in the total amount of volt

what happens to the Amp in a parallel connection?

The following has something to do with this general question.

If the total amount of Amp will grow in a parallel connection I think I will just use one cordless drill battery and the make a switch so I can replace it when if it runs out.

Now for the PC-speakers I think I have an other cheap and easy idea.

why not have a separate battery for the speakers?

It is inspired by the battery in my sons remote-controlled-toy-car. It is just a package of 8 small normal rechargeable battery with to wires coming out an a connection socket in the end of this wires. The charger is simply a converter with the right amount of volt and amp.

Now the PC-speakers that I have was originally build with a converter to take power from the wall. I took that out, but I still have it. Now what if I just make a packages of ordinary rechargeable batteries (like what you bay in a supermarket) 1.5 v and some small amount of milliamp.. For instance seeks of these connected parallel and serial to get 9 volt and held together with a lot of Gaffa tape. Then use the convert from the PC-speakers 8.5 v 0.6 Amp as charger for this battery. Wouldn't this work?

/Mikkel

0

Share this post


Link to post
Share on other sites
OK got new ideas.

Firs no I haven't tried yet with the IBM laptop. I have plenty of time with the project so why hurry.

A small correction to my earlier mail. Each cell is 1.5 v not 1.2

A general question

In a serial connection the volt value of each cell will be added to the total amount of volt

what happens to the Amp in a serial connection?

the amps stay the same...

In a parallel connection the volt value will stay the same in the total amount of volt

what happens to the Amp in a parallel connection?

The amps add up with the each cell added

The following has something to do with this general question.

If the total amount of Amp will grow in a parallel connection I think I will just use one cordless drill battery and the make a switch so I can replace it when if it runs out.

Now for the PC-speakers I think I have an other cheap and easy idea.

why not have a separate battery for the speakers?

It is inspired by the battery in my sons remote-controlled-toy-car. It is just a package of 8 small normal rechargeable battery with to wires coming out an a connection socket in the end of this wires. The charger is simply a converter with the right amount of volt and amp.

Now the PC-speakers that I have was originally build with a converter to take power from the wall. I took that out, but I still have it. Now what if I just make a packages of ordinary rechargeable batteries (like what you bay in a supermarket) 1.5 v and some small amount of milliamp.. For instance seeks of these connected parallel and serial to get 9 volt and held together with a lot of Gaffa tape. Then use the convert from the PC-speakers 8.5 v 0.6 Amp as charger for this battery. Wouldn't this work?

/Mikkel

I think you got it figured out...

0

Share this post


Link to post
Share on other sites

Thank you PurpleJesus. Short and prices answers. I will return when I got some results to tell about. It might take some time. Thanks again to all helpers.

/mikkel

0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0