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Power a mobile rig from a cordless drill battery?

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Jul 28th 2013, 23:51
RecycledElectrons Joined: Jun 2nd 2011, 04:57 Total Topics: 0 Total Posts: 0	Has anyone ever powered a HAM radio off a cordless tool battery? I don't want to re-invent the wheel. I have rewired 3 chargers to act as battery holders with power pole connectors. (Sorry, I'm new to this forum and have not figured out how to post a picture yet.) I think I can use a DC/DC converter to drop the voltage down from a nominal 18V DC (really 15.0V-21.5V) to a nice, clean 12.0V DC. 10 Amp DC/DC converters are available on ebay for under $50. I could even use a big regulator if I didn't mind the inefficiency, but I have a DC/DC converter laying around. The circuitry to switch between several batteries would be difficult, but it could be done. I would be more likely to just drop off for a few seconds as I pulled one battery and inserted another.
Jul 29th 2013, 02:52
aa6e Joined: Apr 4th 1998, 00:00 Total Topics: 0 Total Posts: 0	I see no reason in principle why this wouldn't work. In practice, you need to worry about the quality of your DC-DC converter, same as with any switching supply. You will often get radio interference from these, especially if you're working at HF. It's less of a problem at VHF and up. You may find that 12.0 V is lower than optimum for your rig. They may want up to 13.6 V or so, which is typical for mobile setups. Check your manual. 73 Martin AA6E
Jul 29th 2013, 13:34
RecycledElectrons Joined: Jun 2nd 2011, 04:57 Total Topics: 0 Total Posts: 0	RFI? I never thought of that, but it's easy enough to test once a DC/DC converter is wired in. Yes, 12.0V DC is lower than I would like, but 12.0V DC/DC converters are much easier (and cheaper) to obtain than are 13.6V DC/DC converters.
Sep 2nd 2013, 22:28
RecycledElectrons Joined: Jun 2nd 2011, 04:57 Total Topics: 0 Total Posts: 0	I've got it assembled. One problem: that "20A" panel mount ammeter from eBay actually reads 20.0 at 1 Amp, 10 at 0.5 Amp, etc. http://www.Next2070.com/Radio/DC-DC_Converter.JPG http://www.Next2070.com/Radio/18V_Adapter_and_Charger.JPG (I need to learn to take better pics at some point. I apologize for the quality of my pics.) It seems to work for power tools so far, and it runs a cigarette lighter socket in my apartment just great. I use a cheap Imax B6 hobby charger to charge batteries that are plugged into the adapter. It lets me charge my home-refurbished lithium battery packs. I have not tried it with a ham radio, yet.
Nov 1st 2013, 19:03
dboyt Joined: Aug 21st 2013, 16:28 Total Topics: 0 Total Posts: 0	I'm new to the forum, but I have used an electric drill battery for an HT. I went with a 12V lithium ion system, so there was no need to convert voltages. Also lets you use other accessories,such as a flash light with the same battery. The connection is a cigarette lighter socket that lets me use the battery eliminator on the HT without modification.
Nov 21st 2018, 09:18
KW1W Joined: Aug 28th 2018, 13:45 Total Topics: 0 Total Posts: 0	Would an 18 or 20 volt drill battery recharge an HT without damage? KC1JYC
Nov 21st 2018, 11:55
W1VT Super Moderator Joined: Apr 4th 1998, 00:00 Total Topics: 0 Total Posts: 0	A charger that used switching supply technology can often be designed to handle a wide input range of voltages, but that technology is the hardest to reverse engineering to determine the limits of a mystery circuit. A charger based on a pass transistor or linear techniques will usually overheat when the input voltage is significantly increased. Zak W1VT ARRL Senior Lab Engineer