Sorry Cable Guy

[classic53]

Hey Mike,

I haven't read much of the skinny lately but I have a question now that the new generation of DA's are out. Any ideas about going Litthium on the DA polisher? Sure would like not having to deal with electrical cords hanging around when tryig to use it.

[Nick Chapman]

Re: Sorry Cable Guy

They had a battery powered DA avaliable for a while. But aside from appling and removing wax, it was useless. Battery power does not give you enough torque to remove defects.
They have since discontinued the battery powered DA. Doubt they will bring it back.

Nick

[Mike Phillips]

Re: Sorry Cable Guy

Nick's right.

A cordless polisher is a great idea and while it seems to work great for a whole host of tools like drills for example, but it just doesn't work for a tool that has to rotate a foam pad over large surface areas for long periods of time.

We had a poll one time where it was asked how many hours do you spend detailing your car and if memory serves us correctly the most popular choice was 12 hours.

If you're starting a new detail on a car that has swirls and scratches and you want to remove them, (not just wax the car), then the "Cleaning Step" for the average car is going to take you anywhere from 3 to 6 hours. That is the step where you would use the DA Polisher with a polishing pad and a cleaner/polish like M80 or M83 will take you the longest amount of time because it's the step where you're removing a little paint over all the painted panels in an effort to level the surface with the lowest depth of the deepest defects and this is not a fast process.

A cordless polisher just doesn't have the power to do the cleaning step.

Once the cleaning step is over then yes, a cordless polisher will work to spread out a layer of wax, but that's not what most people want to do with a DA Polisher, at least not initially.

Great idea, maybe someday technology will pave the way to a tool that will do this.

[BlueZero]

Re: Sorry Cable Guy

I've been shopping for a cordless drill and I really do see this being a possibly in a year or so. I got a Bosch Pocket Driver free with my table saw and it's amazing. It's only 10.8V but since it's lithium it seems like more. It has 80 lbs of torque. The ad states it will drive 100 - 3" screws per charge and I believe it. Charging a battery only takes 30 mins. When you start getting into the bigger drills they last longer and charge faster. You can charge a battery faster than you can drain one.

I think as far as power, it's already there. As far as run time, with lithium it's there too. Just have to get someone to put it all together in to the right tool.

[Nick Chapman]

Re: Sorry Cable Guy

The ad states it will drive 100 - 3" screws per charge and I believe it. Charging a battery only takes 30 mins.

100 3" screws really isn't a lot of time if you think about it.

How long does it take to drive a 3" screw? 15 seconds at the most? Thats 1500 seconds total......25 minutes.

I still think it's a long ways off before they will develope a battery that can last hours and hours, and still produce enough torque to power a DA to removed defects. You have to remember, the screwdriver is focusing it's torque across a 1/4 in screw head. Now magnify that to a 6" pad, while applying the same amount of pressure. Thats a lot of torque!

Nick

[the other pc]

Re: Sorry Cable Guy

It comes down to battery technology.

No existing battery technology can hold enough energy to drive a buffer that’s powerful enough to do significant paint correction for a useable period of time.

Let’s run a few numbers.

The Porter-Cable DA sander/polisher, aka the G100, 7424, 4336, 7335, etc draws 3.7 amps of current at 120 volts ac. That’s 3.7 volts x 120 amps = 444 watts of power consumption.

Milwaukee’s V18 series cordless tools are a good example of commercial-grade products built for use in the construction trade. Dewalt, Makita and the others make similar products.

A Milwaukee V18, 18 volt Li-ion battery pack (model 48-11-1830) sells for about a hundred bucks. It’s rated for 3 amp-hours of energy. So that’s:

18 volts x 3 amp-hours = 54 watt-hours of total energy storage

So, if you were to try to drive a tool with the same power as a G100 with this battery you’d get:

(54 watt-hours)/(444 watts) = 0.12 hours of runtime

That means you’d get about 7 minutes and 18 seconds to buff your car before you’d have to recharge/change the battery.


PC.

[Mike Phillips]

Re: Sorry Cable Guy

Thank you so much Paul for your detailed explanation of why it won't work!

[Nick Chapman]

Re: Sorry Cable Guy

That means you’d get about 7 minutes and 18 seconds to buff your car before you’d have to recharge/change the battery.


PC.

That sounds like a challenge Paul. You saying I'm not man enough?

[Mike Phillips]

Re: Sorry Cable Guy

Just a little off topic...

Paul, we changed your Avatar to a better and larger picture of Duckman, hope you don't mind...

[BlueZero]

Re: Sorry Cable Guy

Thanks for the info Paul! I see where your coming from.

Just thinking out loud here with a bit of wishful thinking... Bosch has 36V lithium battery packs so lets say that would double the run time, plus they have a higher capacity version with even longer run time. Now throw in a more efficient motor and we are getting closer with the technology that is currently out. It's not going to run for a few hours but I would think it's close to running for as long as it would take to charge a new battery. I wouldn't want to buy one till I get at least a good hour of run time but I'm just saying.

Or just use my patented cordless extension cord and your all set.

[the other pc]

Re: Sorry Cable Guy

That sounds like a challenge Paul. You saying I'm not man enough?

Nick, I know you’re tough enough to buff out a car if the buffer wasn’t even running! But I also know you’re smart enough not to try it.

...Paul, we changed your Avatar to a better and larger picture of Duckman, hope you don't mind...

Love it! Thanks!

...Just thinking out loud here with a bit of wishful thinking... Bosch has 36V lithium battery packs so lets say that would double the run time, plus they have a higher capacity version with even longer run time. Now throw in a more efficient motor and we are getting closer with the technology that is currently out. ...

Unfortunately, it doesn’t really work that way. Bosch’s 36 volt batteries don’t necessarily have any more energy capacity than Milwaukee’s 18 volt batteries. (And I guarantee you they have far less capacity than the 12 volt battery under the hood of your car.)

The key characteristic at issue is called energy density, which is how much energy you can fit into how much space. That’s primarily based on battery chemistry but it’s also affected by construction. So an 18 volt battery will have exactly the same energy capacity as a 36 volt battery if they’re the same size and same chemistry.

The fundamental building block of a battery is called a cell. A cell contains the chemicals and electrodes that hold the energy. When connected to an electrical load the cells convert the chemical potential energy into electrical energy. The amount of energy is proportional to the amount of chemicals involved.

Each cell will have a low voltage, based on its chemistry. The battery’s voltage comes from stacking the cells in series, which adds their voltages together. A lead-acid car battery has about 2 volts per cell and they stack 6 cells to get 12 volts.

Since the total amount of energy comes from the total amount of chemicals, it doesn’t matter if you have six 2 volt cells at 12 volts, nine smaller 2 volt cells at 18 volts or eighteen even smaller 2 volt cells at 36 volts. If you have the same volume of chemicals, you’ll have the same total energy.

Li-ion cells have around three and a half volts, depending on specific chemistry. An 18 volt battery will have around five cells and the 36 volt battery will have around ten. If they have the same chemistry (and therefore the same energy density) they’ll contain the same energy if they’re the same physical size.

Bosch, Makita, Milwaukee or whoever wasn’t the point. I just used Milwaukee as an example because they actually mention the energy spec for that battery.

Power tool companies don’t make batteries. They buy them from battery companies. The battery business is highly competitive and reasonably mature. Improvements are coming incrementally and when they do they get commercialized quickly. So, all the tool companies have access to pretty much the same “state of the art” battery technology.

For now and the immediately foreseeable future there is no battery technology that promises to provide enough energy density to make a cordless buffer practical. Companies and research institutions are spending billions of dollars on battery R&D so there’s hope for the future.

Electric motors have been around for more than a century and a half. They’re also developed to a very high level and they’re already very efficient. There are improvements being made in power and size and a variety of other characteristics but any improvements in efficiency can’t be big.



PC.

[BlueZero]

Re: Sorry Cable Guy

Wow, thanks PC! Interesting information. I always like learning.

I was just reading a write up on digital camera batteries last week. Now it makes so much more sense.

[G Force]

Re: Sorry Cable Guy

About a year ago i purchased a rechargeable drill.It is really slow to drill concrete at home.I used it several times to polish, wet sand head lights.
I guess it can turn four hours after one night's charge.It has a heavy battery with Ni-Cd 18V written on it.

[Lydia]

Re: Sorry Cable Guy

Hey Paul, did you use your slide rule to figure that out?

[the other pc]

Re: Sorry Cable Guy