Use 18v Drill Battery as Source for 120v AC

[jblnut]

DeWalt makes what I'm thinking of but I own exactly nothing 20/60v DeWalt. I'm thinking of trying to make something similar to use with some Ryobi batteries I seem to have an abundance of.

I've been tossing this around for a while and keep coming back to an inverter made to go work with solar panels. Most of them are flexible on their input voltages so 18-20v DC would work great. Link to an inverter so you know WTH I'm talking about if you don't already. However most of thesec inverters call out "Please be noted, This grid tie inverter cannot be used as off grid/stand alone solar system. The output need to be connected to the grid power. Can not supply power directly to the AC loads."

Everything I've been finding wants to be tied into grid power or has a rigid advertised input voltage of 12v, 24v, 36v, etc. I'm looking for off grid use. Nothing crazy like a welder or fridge but something more like a fan or some party lights while camping. Yes, Ryobi makes a fan and it's actually quite nice but it's the idea of doing this that keeps nagging at me.

I know a little but probably not enough about Lithium batteries to make this work but it's worth a shot. When an "18v" battery is fully charged it'll be right around 20v and will slowly drain down towards 18v. This inverter would need to be able to handle that voltage drop.

Does anyone know of something out of the box that will convert 18v-20v or 36-40v DC to 120v AC ??

Anyone done this before ?? Other than Dewalt ....

 

[62civa]

Most of the lithium batteries used on hand tools have about a 75 watt/hours rating. They are no where near high enough capacity to run an inverter of any size for very long. If you were to say run a 100 watt invertor from a 75 watt battery you would get about 30 minutes run time. A 300 watt invertor, 10 minutes IF the battery could actually put out that much current without tripping any internal protection circuit. The other problem as you have already figured out is there are no 18 Vdc input invertors.

 

[Sevenhills1952]

There's no free lunch. There's always a loss...battery to inverter which powers stuff.

"something more like a fan or some party lights while camping. "

So if you have a bunch of 18 v Ryobi batteries, I would use them directly to run fan or lights. Lower current means more run time, so LED lights would be my choice.
Lots of things run on 12vdc, so I would use an L7812 regulator IC. Mount it on a heat sink , they're very inexpensive, 3 pins...so 18v in, ground, 12v out. Run a string of LED lights or fan designed for 12v.

 

[PhysicsDude]

I have a small inverter (300w I think) that I've used with lithium cells to power small devices for small periods of time.

The off-the-shelf 12V inverters made for cars WILL NOT work 16+ volts. The cheapie one I have cuts out around 15V.

Car battery + an inverter is cheap and easy. You can get a deep cycle 35AH battery (That's ~8 times more capacity than a Ryobi battery) at Wal-Mart for $70. You can pick up a small inverter for less than $30, and then you have your mobile 120V source for less than $100.

You definitely could make a circuit to use a Ryobi battery for a 120v source, but it would be quite a bit of work, and you'd end up with relatively little power.

If you still want to pursue this idea, my suggestion would be to get something like this:

https://www.amazon.com/dp/B071CWMRYD/?tag=atomicindus08-20

To step the 18-20V down to 12V, and then you can 12V accessories or an interver off the battery. You could also use L7812 regulator ICs.

 

[vavet]

This has some serious Rube Goldberg potential.
Use the batteries you have to drive a motor. Install a V-belt sheave on that output shaft. Use a V-belt to attach 8 alternators. Eight alternators tied together in series, 15V each, should give you 120V. Get rid of the rectifiers on them and you should have alternating current. You can mess with the relative size of the sheaves from the motor and the alternators to get 60Hz.

 

[sberry]

I think Milwaukee makes one. It's complicated and uses several batteries. It uses hi output batteries. There would need to be something very compelling to want to fart with this.

 

[Sevenhills1952]

This has some serious Rube Goldberg potential.
Use the batteries you have to drive a motor. Install a V-belt sheave on that output shaft. Use a V-belt to attach 8 alternators. Eight alternators tied together in series, 15V each, should give you 120V. Get rid of the rectifiers on them and you should have alternating current. You can mess with the relative size of the sheaves from the motor and the alternators to get 60Hz.

Or chuck a fan blade in the drill for a fan!
Burn citronella candles.

 

[American Locomotive]

They make 36v inverters, and 18v lithium batteries in series would work just fine with that.

However, as others mentioned, a single Ryobi battery like that might contain 75-100 watt-hours of power. That means the battery could run a single 75 watt lightbulb for roughly one hour. That's not a lot of power.

 

[jblnut]

If you still want to pursue this idea, my suggestion would be to get something like this:

https://www.amazon.com/dp/B071CWMRYD/?tag=atomicindus08-20

To step the 18-20V down to 12V, and then you can 12V accessories or an interver off the battery. You could also use L7812 regulator ICs.

That little buck converter will do the trick. I can use it to run a small 12v inverter to make 120AC

There would need to be something very compelling to want to fart with this.

No real need other than why not ?? I was looking at my pile of batteries and thought it has to be possible. What better place to ask than on here ?? With such great minds like yours to pick I figured someone will have a much better answer/suggestion than what I can come up with.

 

[u3b3rg33k]

I don't see why this would be a problem for small loads. plenty of cigarette lighter inverters are limited to 10-15 amp draw (120-180W), so if you can find a cheap inverter that runs off tool batteries, the only issue will be runtime.

 

[GRB]

Unless you are power something that must be run on AC, the thing to do is run your load directly. If you want a fan, run the fan from the tool company. The largest capacity right now are the Milwaukee 18v 9ah batteries and they will run a decent fan for hours, lights for a long time.

It doesn't make sense to use a tiny battery such as a cordless tool battery and then lose efficiency with an inverter if you are only running something that will run on DC.

Think of it this way:
a huge cordless battery is the Milwaukee 18v 9ah - 9x18=72 amp hours - less than the capacity of a small deep cycle battery like you would use for a battery powered trolling motor for just moving a small row boat around at 2mph.

There is a reason why the battery in my small battery powered forklift weights 1100 pounds.

RVs and boats don't use battery power to run the same lights they run when hooked up to line powery, they have separate low voltage DC lights. They only run items that must be run on AC.

 

[u3b3rg33k]

Unless you are power something that must be run on AC, the thing to do is run your load directly. If you want a fan, run the fan from the tool company. The largest capacity right now are the Milwaukee 18v 9ah batteries and they will run a decent fan for hours, lights for a long time.

It doesn't make sense to use a tiny battery such as a cordless tool battery and then lose efficiency with an inverter if you are only running something that will run on DC.

Think of it this way:
a huge cordless battery is the Milwaukee 18v 9ah - 9x18=72 amp hours - less than the capacity of a small deep cycle battery like you would use for a battery powered trolling motor for just moving a small row boat around at 2mph.

There is a reason why the battery in my small battery powered forklift weights 1100 pounds.

RVs and boats don't use battery power to run the same lights they run when hooked up to line powery, they have separate low voltage DC lights. They only run items that must be run on AC.

because it's made of lead? it'd be 350# if it was Li-ion.

amp-hours are a bad comparison unless you're looking at the same voltage battery. also less of a factor with Li-ion than lead acid is the rate at which you pull out power - slow draw (RC rating) on a lead acid yields a lot more usable power than faster drawdown (1h). on li-ion, so long as you're within the safety limits of the battery, there's very little difference, so you can often get away with a much smaller (Ah) battery.

Wh is a better number for battery comparisons than Ah because the voltage doesn't matter.

 

[alfredeneuman]

Wh is a better number for battery comparisons than Ah because the voltage doesn't matter.

You can easily convert Ah to Wh by simply multiplying the Ah with the voltage.

Ah X Voltage=Wh

 

[u3b3rg33k]

 

[GRB]

You can easily convert Ah to Wh by simply multiplying the Ah with the voltage.

Ah X Voltage=Wh

Sorry, I did mean Watt Hours. The Milwaukee large Cordless battery is 9ah and 18 volts.

9 amp hours x 18 volts = 162 watt hours.

Didn't get the math right either since I wrote 72 instead of 162.

The point is still the same. Converting DC to AC to run a load that could work well on DC doesn't make a lot of sense so avoid it where you can.

 

[theoldwizard1]

Does anyone know of something out of the box that will convert 18v-20v or 36-40v DC to 120v AC ??

First, don't waste your time and money converting to 120VAC if all you want to run is a fan and a few lights. The BEST inverters are only 90%-95%, most are less.

You can buy DC-DC "buck" converts/power supplies on eBay, CHEAP. These are bare, no housing. Spend a few extra dollars and get one with a built in display. Set it for 12VDC and use an RV fan and LED auto bulbs.

 

[62civa]

Unless you are power something that must be run on AC, the thing to do is run your load directly. If you want a fan, run the fan from the tool company. The largest capacity right now are the Milwaukee 18v 9ah batteries and they will run a decent fan for hours, lights for a long time.

It doesn't make sense to use a tiny battery such as a cordless tool battery and then lose efficiency with an inverter if you are only running something that will run on DC.

Think of it this way:
a huge cordless battery is the Milwaukee 18v 9ah - 9x18=72 amp hours - less than the capacity of a small deep cycle battery like you would use for a battery powered trolling motor for just moving a small row boat around at 2mph.

There is a reason why the battery in my small battery powered forklift weights 1100 pounds.

RVs and boats don't use battery power to run the same lights they run when hooked up to line powery, they have separate low voltage DC lights. They only run items that must be run on AC.

18v x 9 amps = 72 watt hours, not 72 amp hours.