Cordless Power Tool - corder...

[TaDa]

Hi!

Another of my cordless tools has hit the point of uneconomical 'repair' - where the cost of the new batteries exceeds a new tool.
This one is a circular saw - so no real need for the battery to be attached...

I find this really annoying, previously I have successfully replaced the batteries (they're often just sub-c NiCds) but this is a bit of a pain.

I'm currently thinking of making a generic battery pack (using new NiCds and the temp sensor from the original pack) and then run a power cord to the tool from the box (!!)

If I have an 18V battery and a 500W tool - I'm going to be drawing around 30Amps, for a 12V battery and 500W this would be 42Amps
(perhaps a (significant) spike more at motor start up)

Car battery jump leads are rated at 200A plus - but I wonder if they could withstand 30Amp for "a few minutes at a time"?
I've done a bit of research and feel that 8 gauge cable should be sufficient (and have some flexibility)

I really want this to be possible as I could then re-use the charger and, if I get a suitably rated female socket, I can fix that to the empty original battery pack thus making it 'look the part'. As other 18V tools die I can just replace their batteries with another connector. Who knows, maybe I'll just buy second hand tools from thereon ;-)

So, could I use some 8 gauge Car battery jump leads - perhaps 1.2m long - to join the battery pack to the tool?

And, if so, are there any reasonably cheap durable connectors I could use? (Andersons are too pricey - even if they are perfect)

 

[4pyros]

I have converted car battery chargers to full wave rectificashoin to get 18 volts out of them and wired the end that used to go to the battery (large aligator clips) to an old battery pack shell so I can use all my 18 volt tools with it, and still be able to use batterys when I need to. Works grait!

 

[TaDa]

I have converted car battery chargers to full wave rectificashoin to get 18 volts out of them and wired the end that used to go to the battery (large aligator clips) to an old battery pack shell so I can use all my 18 volt tools with it, and still be able to use batterys when I need to. Works grait!

Cool!
That was quite a powerful battery charger you had there - I did similar with one a few years back and blew the rectifier (£4 for a much better one from Maplins) .
How did you get 18V out of it - did the transformer give 20V ac?
Surely the the charger cables would be less able to handle the high current - watch you don't burn yourself on long cutting/drilling sessions!

So I think my original questions still stand - is 8ga sufficient (sounds like it might be) and what connectors could I use?

 

[tcmtech]

Personally for a short range cord say ten feet long at 50 amps 10 ga stranded wire would be plenty heavy enough.

At 30 - 35 amps 12 ga fine strand type speaker wire will easily take that and barely warm up even after several minutes.

 

[TaDa]

Personally for a short range cord say ten feet long at 50 amps 10 ga stranded wire would be plenty heavy enough.

At 30 - 35 amps 12 ga fine strand type speaker wire will easily take that and barely warm up even after several minutes.

Ah! I am being Victorian in my over-engineering here then!

Is that 10 AWG or 10 SWG - I see some car audio power installation kits but they have 10 awg wire - I know swg cable is thicker than awg - so I need to even worry?

Can I buy mains twin core in this gauge - would that be suitable/capable?

Also, could I use some form of audio connector too - I don't want to use mains like connectors as this is just asking for trouble (!!)

 

[tcmtech]

Up to you what you use. I go by standard AWG values.

If you look inside your cordless tools most of them are wires with 14 gauge wire anyway.

 

[Al Manzoli]

Hi!

Another of my cordless tools has hit the point of uneconomical 'repair' - where the cost of the new batteries exceeds a new tool.
This one is a circular saw - so no real need for the battery to be attached...

I find this really annoying, previously I have successfully replaced the batteries (they're often just sub-c NiCds) but this is a bit of a pain.

I'm currently thinking of making a generic battery pack (using new NiCds and the temp sensor from the original pack) and then run a power cord to the tool from the box (!!)

If I have an 18V battery and a 500W tool - I'm going to be drawing around 30Amps, for a 12V battery and 500W this would be 42Amps
(perhaps a (significant) spike more at motor start up)

Car battery jump leads are rated at 200A plus - but I wonder if they could withstand 30Amp for "a few minutes at a time"?
I've done a bit of research and feel that 8 gauge cable should be sufficient (and have some flexibility)

I really want this to be possible as I could then re-use the charger and, if I get a suitably rated female socket, I can fix that to the empty original battery pack thus making it 'look the part'. As other 18V tools die I can just replace their batteries with another connector. Who knows, maybe I'll just buy second hand tools from thereon ;-)

So, could I use some 8 gauge Car battery jump leads - perhaps 1.2m long - to join the battery pack to the tool?

And, if so, are there any reasonably cheap durable connectors I could use? (Andersons are too pricey - even if they are perfect)

I M O , this is not only impractical , it could be potentially dangerous !

Cheap power tools are cheap comparatively.

I have hated to toss power tools , because the cost of the batteries was not feasible .

But , bite the bullet and buy new . A lot safer !

 

[3v0]

I M O , this is not only impractical , it could be potentially dangerous !

What great danger do you see? It would be no less practical then corded drill!

 

[Al Manzoli]

What great danger do you see? It would be no less practical then corded drill!

A corded drill was designed , tested and approved.

Try getting a Mickey Mouse hook up tested and approved !

You are dealing with line voltage instead of low voltage .

 

[tcmtech]

A corded drill was designed , tested and approved.

Try getting a Mickey Mouse hook up tested and approved !

You are dealing with line voltage instead of low voltage .

Huh?

In his third paragraph he clearly states that this will be running off an external battery pack through a cord.
Where does your AC line voltage issue come from?

Also why does he have to get his own tools tested and approved by anyone?

I am not following any of your reasoning here?

If he needs approval I approve of his actions!

 

[Al Manzoli]

Huh?

In his third paragraph he clearly states that this will be running off an external battery pack through a cord.
Where does your AC line voltage issue come from?

Also why does he have to get his own tools tested and approved by anyone?

I am not following any of your reasoning here?

If he needs approval I approve of his actions!

Remember , I did say I M O .

Unless the O P is an electrical engineer , I think he should be extremely careful !

Safety First !

You have made your decision on this topic , and I respect that !

 

[MrAl]

Hi,

I run my drill off of a 12v lead acid battery now. Long long time ago i got extremely fed up with replacing the sub C NiCd batteries in the pack, and the new packs are over priced.

My drill draws about 30 amps or maybe a little more when fully loaded, yet it works pretty well with what i think is #14 gauge wire. However, my motor is a 9.6v motor so it does not mind a little voltage drop from 12v. But the run is short too, about 6 feet, so there isnt much drop anyway.

For 30 amps a wire diameter of 0.1 inches is good. If you look up your country's wire standard you can use that as a guide. That's about a #10 AWG wire here in the US. For the short run you have this should work fine.

Once it tried using a lead acid battery rather than NiCd's i was sold, never to go back to using NiCd's again ever. Not only do they seem to last longer, but the capacity is much greater. A typical sub C NiCd is about 2 ampere hours, while a smallish 12v 8 ampere hour battery has four times the storage capacity meaning that it will drill and drive for 4 times as long as the NiCd's before needed a recharge.

The time when you might really need the NiCd's is if you use the drill a lot over a day where you have to keep charging the batteries over and over, and maybe have two or more packs on hand so when one is being used the others are being charged. The reason is that NiCd's can take recharging more than lead acid, so that's something to consider too. But for me i dont have to use the drill every day, but when i need to use it i really need to use it and it must work, so i have a couple 12v batteries for it.

I made my own connector to connect the drill to the battery. The drill came with two NiCd packs, so i took all the cells out of one and put a high current diode inside and wired it up to about 6 feet of wire. The other end of the wire i just soldered two "Fast-on" connectors that plug right onto the battery terminals. It's not hard to use as i just stick the connectors on and im ready to go.
An improvement though would be to have connectors right on the battery itself, where the modified pack would plug into it with one connector like a Molex or something. That would make it even easier.
The extra wire now is a little bit of a bother, but not too bad. You can still carry it with you wherever you want to go.

The Li-ion drills are supposed to be a bit better as they have less self discharge. I'm still sold on the lead acid though.

 

[4pyros]

That was quite a powerful battery charger you had there - I did similar with one a few years back and blew the rectifier (£4 for a much better one from Maplins)

It was a 2-10 amp charger witha 50 amp start from sears.
I pulled all the guts out and made my own 50 amp bridge rectifier to get 17 volts norm and about 19 volts at 50 amps on the start mode, but you can not run on start mode all the time with out it over heating.

 

[3v0]

Remember , I did say I M O .

Unless the O P is an electrical engineer , I think he should be extremely careful !

This is not rocket science and you don't need an EE degree to do this! If you want something to be concerned about try the guys who want to build inverters when they don't know a capacitor from a can opener.

 

[4pyros]

Personally for a short range cord say ten feet long at 50 amps 10 ga stranded wire would be plenty heavy enough.

Yes for a short run ware it is not fully loaded all the time 10 gage is fine. Thats what the charger came with.

 

[4pyros]

Also, could I use some form of audio connector too

It will be hard to find an audio connector that will handle 30 amps.
Just hard wire an old battery case, the connector was made to handle the current.

 

[TaDa]

Thanks everyone - Now I know its a goer I'm really looking forward to this

I've already bought a cheap set of jump leads and will hack one set of clamps off - I reckon they'll come in handy one day
and a few 'cheap' anderson 50Amp connectors (£10 for 4 - not that cheap but I don't want to spend my life on this) I will solder one of these where I removed the clips
I will then attach another to the empty battery pack of my circular saw - possibly using soldered on fast-on connectors inside the pack - thanks for the tip!

I'm presuming the diode is to prevent misorienting the terminals and running the tool in reverse - is that right?
Thats a doozy of a diode - 50Amps - given Maplin's ranges and prices I fear I could buy a whole new circular saw :-(
So, for now, given that the connectors only connect one way round and the thick black and red cables are quite a clue to putting them on the battery correctly I'll live with the risk.

One day I guess I might put an in-line fuse and diode on the leads (near the clamps)

Now, is there an easy way to selectively 'voltage double' the 12V up to 14.4V, 18V and 19.2 Volts (or down to 9.6 or 4.8v for that matter) - yet still retain the huge current?

 

[tcmtech]

The easiest way to get the correct voltages would be to use batteries that have somewhat close voltage ratings.

There are single cell type LA batteries that come in small sizes like a 2 volt 2.5 ah D size and up going into the 25+Ah range. Per cell they are fairly cheap and allow for making custom voltage LA based battery packs easy.

Enersys is one big manufactures of them and they can be found on eBay cheap!

The other option is using 6 volt UPS type battery packs.

The odds are the 4.8 volt stuff will run on a 6 volt LA battery pack without problems and the 9.6 on 12 volts. As for the 14.4 and 18 I would just go with an 18 volt LA system based on three six volt batteries in series.

As I know with my own 19.2 cordless tools they have no problems with running on 24 volts either and in fact I have seen my nicad packs come off the chargers at near that voltage.

The point is the electric motors used in these sort of cordless tools are pretty forgiving to having a bit extra voltage given to them.

 

[TaDa]

Yeah - but I've got nice big car battery 'just sitting' there and my circular saw is 18V

I know what you mean though and if I had 3 6v LA battery packs I could run any of these items as required...

Hmm, car batteries (especially this one from a landrover) are not that portable and my LA car battery charger has a 6v setting - perhaps this is 'a sign'

It would be nice to just have one 12v battery and switch between them though - another day perhaps!

 

[3v0]

Car batteries are not well suited as a power source for a cordless tool. However deep cycle batteries intended for RV and trolling motors would be a good choice.

Car batteries are designed to start the car and then be recharged. Running them down will shorten their life dramatically.

I am not saying you can't use one. It just has that one downside.