18V Cordless Tools >> 12V Power Supply?

[rardiH36]

I have an older generation 18V cordless jig saw and also an 18V cordless 5 1/2" circular saw. Original battery packs were NiCad. Long since past their "peak condition", they will only hold a barely adequate charge for a few minutes. Pretty useless. Not worth replacing them again with with outdated NiCad technology.

In the past, I have jury-rigged 12v and a 14.4V cordless drills to be powered instead by my 12V boat or car batteries. Great tool to have on a boat.

Am thinking to do the same with my 18V saws.

The voltage drop of 110V AC over a long and/or too small gauge extension cord I know can "do in" the motor of a power tool that is operated under load. (Yes, I've done that!)

I am concerned that a 12V DC power source verses 18V DC tools might do the same. When using a cordless tool, except for the first few minutes of operation, the tool does keeps running as the voltage of the battery pack drops. Albeit at a slower and less powerful rate. But the available amperage also drops along the voltage. So maybe that's the "protection" for the tool?

But Connected to the 12v Group 27 battery array on my boat, the 12V also comes with plenty of amps delivered to the tool.

Anyone know for sure?

 

[dlochner]

If I understand you correctly, you want to convert your cordless tools to corded tools.

You are correct you probably won't get the same power from them, which may or may not be an issue. The voltage drop will probably have less impact on the drills than on the saws. The circular saw has to spin a relatively heavy blade through wood, it may not have the power to cut much of anything.

If you go down the road, use wire that is a large enough gauge so the voltage drop on the wire is minimal. Blue Sea systems has a chart the gives the voltage drop for different wire gauges and currents. It won't hurt to use 10 gauge wire.

How do yo connect the new power cord to the tool?

 

[jamhass]

My guess (and that is all it is) is that the tool in unlikely to work on 12v. I say this noting that as Li-i batteries run down, the tool works fine then "suddenly" stops as the battery voltage drops. I'm not sure at what voltage the tool cuts out at, but I'm guessing it is close to the nominal battery voltage.

My guess is the tool will be much happier -- and you too -- by keeping batteries charged using the inverter to power the charger as needed.

Let us know what your actual experience is.

 

[Jackdaw]

My bother (contractor) knows guys that do this with no apparent damage to their tools. 9v, 18v, 24v. From a technical point of view there are LOTS of variables however, so YMMV.

 

[tjar]

Would there be any advantage in using a step up converter to boost the voltage from 12v to 18v? There are many types available on Ebay for $20-50.

 

[Justin_NSA]

Is this any help? You can convert nicad tools to lithium ion
http://www.instructables.com/id/Converting-Cordless-To-Lithium-Li-Po/

 

[sailnoproblem]

I use battery powered tools all the time. I find when the battery starts to die it's cheaper to buy a whole new tool set then to try and replace a new battery.they are fairly inexpensive nowadays. why would you want a cord? again that's only my stupid opinion. as I am not a contractor just a DIYer.

 

[capta]

My Ryobi drill has a 12 volt fast charger for their 18 volt lithium batteries. Charges one battery faster than I can deplete the other one. Perhaps other manufacturers have something comparable. If not, I'd highly recommend this set up. In the old days when I was off the dock for extended periods the generator rarely ran long enough to charge the cordless drill batteries completely. Few of my battery chargers would operate well on my square wave 3k inverter.

 

[MisterR6]

Batteries plus can take your old batteries and convert them to the new batteries using the old battery housing. Usually cheaper than just a replacement for the older model cordless tools. I have cordless tools over 20 years old that are still in use this way. They work at least as good as the original batteries at a reduced cost. Prices vary from brand to brand and many other variables. Its at least worth looking into if there is a batteries plus store near you. Hope my two cents worth helps.

 

[bawlmer]

I had the same issue with a 15.5 volt rechargeable Shark vacuum. When the batteries died I installed a 12 volt cord. It works acceptably but not as well as the original power source. That was only a 3 .5 volt difference. I think your saw with a 6+ volt difference and a much greater amperage draw will not give you satisfactory performance. Just my .02.

 

[rardiH36]

Thanks for your insights everybody!

- Encouraged by Jackdaw's recount that contractors have done similar with their higher voltage "cordless" tools, I will give it a try. The jigsaw will be more useful than a circular saw to have on a boat (like to cut an opening in the interior liner to install something), so I will do the jigsaw first.

- Reason for the "why do I want a cord?": While I have a berth with AC, I never connect to it unless I spend a night or two. Otherwise, a solar panel keeps the house batteries at full charge. At all other times, for the spur of the moment repair or project, much easier to plug the cord of my 12V "cordless" electric drill into my boat's cigarette lighter socket than it is to dig out my 120V dock cord and rig it to the AC power outlet on the dock. I like to have certain tools permanently on the boat. But I don't want to bother with maintaining them always charged. And I prefer not to shuttle tools back and forth between home and boat. Re-purposing otherwise no longer utilized home tools to 12V power source gets around all this.

- I once did check with Batteries+ about repacking a 14.4V DeWalt NiCad pack with new cells. Wasn't all that much of a bargain compared to buying a brand new Li-Ion Craftsman drill.

- Much as the link Justin_NSA provided, I was familiar with the intricacies of LiPo/Lithium Ion batteries because of a past model airplane hobby. Several years ago I did DIY modify a couple of existing NiCad battery packs to Li-Ion. Performance is orders of magnitude better than was the NiCad. A special hobby charger manages the charging regimen. The main issue then is to ensure that the battery pack is never drained down to below about 3.0V per cell. Otherwise the pack is permanently ruined. Commercial tool battery packs have minimum voltage cut-off circuits built in. That is why a Li-Ion tool will be working great then suddenly stop. I added a low battery alarm to my modified packs. The alarm does not cut-off the power. Only gives an audible alert to stop using the tool until charged up again. On standby, the alarm device slowly drains the battery pack. If the tool is stored away somewhere, the alarm can't be heard and the pack will drain below the permanent damage level. So an on/off switch is required.

 

[jeepbluetj]

I wouldn't bother. A Ryobi li-on drill/saw combo is pretty cheap. They make a 12v charger that works fine. The convenience of the battery power is hard to beat.

 

[sailnoproblem]

I wouldn't bother. A Ryobi li-on drill/saw combo is pretty cheap. They make a 12v charger that works fine. The convenience of the battery power is hard to beat.

I agree.