Using a tool battery as a power supply

[raylo32]

Before I got into converting a couple of my bike to e-bikes I had plenty of Li-ion battery tools around and have always loved the versatility and the power you can get from these smallish batteries. We recently got an inflatable kayak and I wanted to be able to inflate it on the beach or near the water away from my vehicle, so using my 3D printer I rigged up a way to use Milwaukee M12 batteries to supply the power. In this case the vehicle (kayak) isn't battery powered but the air pump is. The tiny 1P CP battery will do the job but it is marginal and the voltage will sag enough for the pump to cut off after a couple of fills. The larger XC version that I believe is 2P can easily fill and deflate my 3 chamber kayak (3 psi sides, 6 psi floor) at least several times. I haven't run into the limits yet.

Anyway, this little plug turns any M12 battery into a handy power supply for kayaks, paddle boards, or whatever. I used a female XT-60 on the pigtail and male XT-60s on the device sides. Makes it easy to use on multiple devices. For instance in the shop for testing stuff... or radio control aircraft field boxes. See the instructions and print files here as well as a video demonstration. I am making another similar but heavier duty 12V power supply using Makita 18v batteries and a 12V step down transformer and will post it when finished.

https://www.thingiverse.com/thing:4931489

 

[john61ct]

Nice but

> This thing is a plug that will allow you to tap a 12V Milwaukee tool battery for other uses

may confuse people not familiar

The name for the battery series that offers 12V is Milwaukee M12.

Milwaukee M18 is 18 volts

 

[raylo32]

Ummm... My original post does call them M12 in 2 places... what post are your reading? There are CP and XC versions of M12. I also mention that. The XC type is far superior for this kind of use. The transformed 18V version will be Makita since I don't have any Milwaukee 18v tools or batteries but I do have Makita 18v platform. Confused people don't need to attempt it. Are you confused? LOL.

Edit: OK I think I see what you mean. The description on Thingiverse doesn't use the term M12 in the first reference to the battery. But it does use the term later and clearly shows pictures of batteries labeled M12. I'll edit that text to add M12 to the first instance.

Nice but

> This thing is a plug that will allow you to tap a 12V Milwaukee tool battery for other uses

may confuse people not familiar

The name for the battery series that offers 12V is Milwaukee M12.

Milwaukee M18 is 18 volts

 

[fatty]

Thanks for sharing :thumb:

I am making another similar but heavier duty 12V power supply using Makita 18v batteries and a 12V step down transformer

This wouldn't be beneficial, and with an additional current-limiting device, would actually be "lighter duty" than native 12V. If you need higher power or capacity, simply use the higher capacity packs and/or parallel them.

 

[raylo32]

Tested it and it works fine. The thing is I have a lot of the Makita 18v batteries and those are the biggest Ah ones I have. I only have one of the bigger M12 batteries with native 12V. The devices I am running are mainly compressors that pull max 12-15 amps @12V so that would only be about 8-10 amps out of the 18v battery. The transformers come with 12V outputs ranging from 2 amps to 30 amps and aside from some small loss in efficiency are not going to be limiting current. With as many Makita 18V batteries as I have and the transformer I pretty much have unlimited 12V DC power supply.

This is V1 with a 6 amp transformer... which will see limited duty. I am making a V2 with a 30 amp transformer and a 3D mount with an on/off switch. I'll post it when it is finished.

Thanks for sharing :thumb:

I am making another similar but heavier duty 12V power supply using Makita 18v batteries and a 12V step down transformer

This wouldn't be beneficial, and with an additional current-limiting device, would actually be "lighter duty" than native 12V. If you need higher power or capacity, simply use the higher capacity packs and/or parallel them.

 

[john61ct]

Yes I meant at Thingiverse.

Could you link to the transformers you mean?

And maybe the DC-DC converters too, reliable robust high current ones are usually pricey.

Thanks

 

[raylo32]

It's just one device we are talking about here, DC/DC buck stepdown transformers. This is the one I will be using next, input 15V to 40V, output 12V (well, 12.4 V really) 30A. Looks just like the 6A one in the picture above. Not anything high end and I don't know how reliable it will be but it'll be fine for my use case that won't get close to that 30A max. I am not tying to power a bike off of it or any life critical machines. If it fails I'll look at more expensive options.

https://www.amazon.com/dp/B01JAIC7OO?psc=1&ref=ppx_yo2_dt_b_product_details

Yes I meant at Thingiverse.

Could you link to the transformers you mean?

And maybe the DC-DC converters too, reliable robust high current ones are usually pricey.

Thanks

 

[raylo32]

Got this thing put together this morning... 30A DC/DC converter, 30A rocker switch, 14 GA wire. Off the shelf Makita 18V battery dock from Amazon. Everything is off the shelf except the black 3D printed mount which is optional (the battery dock and DC converter can be sandwiched and hard wired as in the earlier version pictured above), as is the switch. This converter puts out 12.1V DC.

 

[ZeroEm]

y raylo32 » Aug 19 2021 8:32am

Got this thing put together this morning... 30A DC/DC converter, 30A rocker switch, 14 GA wire. Off the shelf Makita 18V battery dock from Amazon. Everything is off the shelf except the black 3D printed mount which is optional (the battery dock and DC converter can be sandwiched and hard wired as in the earlier version pictured above), as is the switch. This converter puts out 12.1V DC.

This is great. I'm a Makita fan and need a 12V source. Last time (1-2yrs) checked on the docks they where priced crazy high. If you don't mind I will copy your design. Great Thread.

 

[raylo32]

You are certainly welcome to use the design, in fact I am posting it on Thingiverse right now. The docks are $15 on Amazon, cheap enough that I didn't bother trying to design and print one. The DC converter was $22, and the switches were $8.99 (for 5). See the listing here on Thingiverse for the 3D print file and links to the parts. That site is slow so it may not be fully loaded with the photos and such yet. But the parts links are there.

And if you don't want a switch or to do a 3D print of the mount you can just sandwich the dock and the converter and connect the wires.

https://www.thingiverse.com/thing:4936295

This is great. I'm a Makita fan and need a 12V source. Last time (1-2yrs) checked on the docks they where priced crazy high. If you don't mind I will copy your design. Great Thread.

 

[john61ct]

Watch out for heat buildup on the DCDC might need to add heatsinking and/or a fan

without that 15-20A might be maximum.

If it becomes important, carry a spare

 

[raylo32]

This thing won't be running continuously for long durations so I am not really worried about heat. But I have lots of alternatives... can usually plug into the car, and I have the Milwaukee version as above, and I have a Li-Ion jump start pack that will also do the job, and failing that I always bring a manual pump. Lots of ways to skin this cat. Perhaps too many?

Watch out for heat buildup on the DCDC might need to add heatsinking and/or a fan

without that 15-20A might be maximum.

If it becomes important, carry a spare

 

[john61ct]

Redundancy is a good thing.

Over packing is not.

 

[raylo32]

Indeed. Probably won't be doing anything but day paddling so no heavy packing. If we went overnight I'd just take the manual pump.

Redundancy is a good thing.

Over packing is not.

 

[Hillhater]

I guess its a case of using what you have available....
In my case i have a surplus of “retired” RC lipo packs ( mostly 5Ah, 5s ) that have been superceeded by bigger/newer packs .
Reconfigured/repackaged as 3s packs they are very compact and able to be attached to 12 v kit such as those “off road” tyre pumps and high power LED flashlights...making them truely portable without the trailing lead to the cig lighter socket !
5- 10amps is no sweat even for a 10 yr old lipo, and can reinflate a car tyre many times on a single charge.
I also have some similar packs remade from 12ah , 2C lipo that are incredibly small !
I take these camping with a cig lighter socket “tail” and a range of usb chargers for Ipad, phone, headlamps, camp lights etc etc
Recharging the lipo is done whilst traveling in the truck between camp sites etc.

 

[raylo32]

LOL... yes, use what you got! I need to check... I also have a couple of 5Ah (or are they 3.5Ah?) LiPo packs around... for an obsolete drone. I don't remember what S they are but if 3S they would be another no brainer 12V source for me. And they already have XT60 plugs. And I have a couple of AC/DC RC chargers. Although the Makita batteries are 5Ah and are probably safer than LiPos.

I guess its a case of using what you have available....
In my case i have a surplus of “retired” RC lipo packs ( mostly 5Ah, 5s ) that have been superceeded by bigger/newer packs .
Reconfigured/repackaged as 3s packs they are very compact and able to be attached to 12 v kit such as those “off road” tyre pumps and high power LED flashlights...making them truely portable without the trailing lead to the cig lighter socket !
5- 10amps is no sweat even for a 10 yr old lipo, and can reinflate a car tyre many times on a single charge.
I also have some similar packs remade from 12ah , 2C lipo that are incredibly small !
I take these camping with a cig lighter socket “tail” and a range of usb chargers for Ipad, phone, headlamps, camp lights etc etc
Recharging the lipo is done whilst traveling in the truck between camp sites etc.

 

[john61ct]

anything is safer than LiPo

3S of the 3.6-3.7V li-ion chemistries is a bit low for nominal 12V

4S of LFP is perfect

 

[spinningmagnets]

Buck converters efficiency is not too bad.

A transformer has two coils with either AC on the input, or pulsed DC.

One coil creates a magnetic field, and the other coil right next to it transforms that pulsing magnetic field back into current.

Buck converters "dim" voltage by pulsing it on and off at a frequency where the average voltage on the output is lower.

There are variable buck converters that can take any common DC voltage and convert it to an adjustable output DC voltage. I bought one to make my 52V ebike battery a variable power supply for simple experiments, but I haven't had time to work on it yet.

 

[raylo32]

Good to know about the variable converters. Probably much cheaper to make a basic variable power supply than to buy a fancy one. But these converters being switched like that probably make somewhat "dirty power", but how dirty? Just thinking... with our e-bike batteries and power tool batteries we have lots of power outage backup potential for things like routers and modems...a assuming your provider keeps their systems up and running. I have a couple of APC UPS's but if these converters would work I could probably do away with the APCs the next time their lead acid batteries bite the dust. I'll give this a test sometime.

Buck converters efficiency is not too bad.

A transformer has two coils with either AC on the input, or pulsed DC.

One coil creates a magnetic field, and the other coil right next to it transforms that pulsing magnetic field back into current.

Buck converters "dim" voltage by pulsing it on and off at a frequency where the average voltage on the output is lower.

There are variable buck converters that can take any common DC voltage and convert it to an adjustable output DC voltage. I bought one to make my 52V ebike battery a variable power supply for simple experiments, but I haven't had time to work on it yet.

 

[ZeroEm]

by raylo32 » Aug 20 2021 9:03am

Good to know about the variable converters. Probably much cheaper to make a basic variable power supply than to buy a fancy one. But these converters being switched like that probably make somewhat "dirty power", but how dirty? Just thinking... with our e-bike batteries and power tool batteries we have lots of power outage backup potential for things like routers and modems...a assuming your provider keeps their systems up and running. I have a couple of APC UPS's but if these converters would work I could probably do away with the APCs the next time their lead acid batteries bite the dust. I'll give this a test sometime.

Dirty power is AC not DC. If i'm wrong please correct me. On the AC side you know it's the Pure Swine wave you want. The others are dirty power.

 

[raylo32]

I am not an electronics engineer by any means... but one who is replied in the other thread that the switching in these converters creates RF interference. Maybe not technically dirty "power" but could perhaps interfere with some electronic devices? Maybe it is just a problem for actual radio transmitters and receivers but then that is what a router essentially is. I dunno. I'll test it at some point.

Dirty power is AC not DC. If i'm wrong please correct me. On the AC side you know it's the Pure Swine wave you want. The others are dirty power.

 

[Hillhater]

3S of the 3.6-3.7V li-ion chemistries is a bit low for nominal 12V

I operate mine 3.7-4.15v (11.1 - 12.5 v) .....they seem happy and are near 10 yrs old !
Also , most 12 v pumps, lights, usb chargers, etc are run ok on anything above 9-10v.

 

[ZeroEm]

y raylo32 » Aug 20 2021 9:54am

I am not an electronics engineer by any means... but one who is replied in the other thread that the switching in these converters creates RF interference. Maybe not technically dirty "power" but could perhaps interfere with some electronic devices? Maybe it is just a problem for actual radio transmitters and receivers but then that is what a router essentially is. I dunno. I'll test it at some point.

I stand corrected, for got about the RF. The old days we needed to put filters in line to clean it up. As the world moved to computers in cars they have been cleaning it up. Just never thought about it until now. Thx.

 

[raylo32]

No worries... electrons are not my main field and I am learning new stuff here every day. Maybe just enough to be dangerous? But this is a great site.

I stand corrected, for got about the RF. The old days we needed to put filters in line to clean it up. As the world moved to computers in cars they have been cleaning it up. Just never thought about it until now. Thx.

 

[ZeroEm]

I state things but like to challenge what I think I know with reality.