I am interested in connecting my MTX400 to a 12V battery, as a backup power supply. Looking for pros, cons and tips...thank you.

[Guest Mark J]

Wanting to use a standalone 12V battery as a backup power supply in the event of a prolonged power failure. Looking for battery recommendations and tips for connecting the radio to the battery. Is it a simple as connecting red to positive and black to negative (don't want to blow anything)? Any comments or suggestions would be appreciated. Surely some other folks have done this. Thanks!

[WROZ250]

You might want to check these guys out:

http://www.westmountainradio.com/
 

Look at their pwrGate products

[PACNWComms]

Your method can work, but I would recommend fuses in both positive and negative wires, and also some method for charging that battery. Many radios do draw a small amount of current when turned off(and will lose some charge sitting as well), and your battery may be dead when needed if there is no charging circuit, or method to trickle charge the battery. If you wish to use a car type battery for backup, add a Battery Tender or similar type of charger connected to the posts, to keep the battery charged. The, it is as easy as you mention.

Uninterruptible Power Supplies (UPS) units also work well for this purpose. At work today, I just repurposed several Eaton battery backup power supplies for exactly this use case. I have some mobile radios that are lightly used, but when the are needed, they need to work. Seeing many UPS units that just needed new batteries,I swapped in new gel cells and charged them up for their new job, as backup power for these radios. For my use, I only need the radio to work for an hour or so when AC power is lost, so small desktop, or under the desk UPS units work for me. If you need more time, use a larger UPS.

 

[marcspaz]

I bought a Thunderbolt 100w solar kit from Harbor Freight.  It comes with a controller, which hooks to the battery.  I then hooked up a 100 amp hr battery.  When the sun is out, the radio runs off the solar kit, but as the sunlight weakens and at night, it runs off the battery I got from Batteries Plus.  Total out of pocket was about $500. 

[OffRoaderX]

2 minutes ago, marcspaz said:

 I then hooked up a 100 amp hr battery. 

Have you tested the power output of the radio while on battery to see if you're getting the full radio power output?  I'm wondering if on 12V instead of 13.8V it will make much of a difference (it did on my MXT500) - although when the power is out we can't be picky, but I'm curious.

[marcspaz]

1 minute ago, OffRoaderX said:

Have you tested the power output of the radio while on battery to see if you're getting the full radio power output?  I'm wondering if on 12V instead of 13.8V it will make much of a difference (it did on my MXT500) - although when the power is out we can't be picky, but I'm curious.

 

I have on an antenna, but not a dummy load.  I definitely do not get full power at night.  The short of it, if the battery drops to 12vdc even, when I key up my GMRS radio, the voltage drops to as little as 11.4vdc while transmitting and I see about 18w-20w output.  My 100w HF radio will send the battery down to 11.1vdc and I'll see about 50w out.

 

At night, I usually reduce power to get more run-time out of the battery and so I don't stress the radio as much with increased current.

 

Depending on how busy I get this week, I can see if I can get real measurements on the dummy load, if you're interested.