Badcaps Forums

Badcaps Forums (
-   Custom Tweaks, Modifications, and Revisions (
-   -   2m/70c Radio battery eliminator build (

goontron 02-10-2018 03:03 PM

2m/70c Radio battery eliminator build
15 Attachment(s)
Well, this timeline is going to be full of holes here. Make sure you format the right SD card kids! Anyway...

So, the battery from my old dual band radio finally quit. I decided to build a battery eliminator.
The case is about 1 1/2" x 3" x 1/2" OD, so space is a bit tight, but not horrible.

Here's what it looks like gutted and my first attempt at a ground bus installed. (Hint, tin coated steel doesn't stick to silicone very well.)
Next, the picture of my first (Failed) attempt.
Why it no work? battery dead? 5.5v? WTF
Doh! I that read wrong. Thats a 6v regulator, not 8v :noob:
Well, lets try switchmode then!
It Verks! *pop* ...are you shitting me? It committed suicide. LED is out.
Round 2?
Round 2 Verks!
Into the case it goes. I had the whole assembly process photographed, but oops.:facepalm:
Still Verks!
Well, glamour (shame?) shots then.
I forgot the nylon nut and bolt.... Crap. I may fix that one day.
DC 20v test. Looks good.
AC 20v test. Also good.
Let me shoehorn in some firmware fuckery proof here.

IN: AC ~9v-30v/DC +/-10v-35v OUT:7.6vDC

Not a bad little eliminator.

stj 02-10-2018 06:32 PM

Re: 2m/70c Radio battery eliminator build
nice - a UV5R, (or is it the 8W model??)
that is a bad idea - the regulator will cook when you transmit 5W.
i would put the regulation at the other end of the cable with a heatsink on it.
then use the battery shell for extra filtering - inductors,caps etc.

goontron 02-10-2018 07:38 PM

Re: 2m/70c Radio battery eliminator build
Its the BF-F8HP. Ive been stress-testing it all day QSLing with the KC7SNO and WU7G/R (2m,70c respectively) repeaters and managed to catch some skip from Denver. My filtering is good enough it seems, and being a 3 amp regulator she gets a bit toasty, but nothing extreme.

desert-rat 02-11-2018 08:51 AM

Re: 2m/70c Radio battery eliminator build
162.55 is the nat. wether sev. As I remember 144 . Mhz is 2 meter ham .

goontron 02-11-2018 11:41 AM

Re: 2m/70c Radio battery eliminator build
^ Yep. It can receive down into those bands. xmit, no. I was using it as a recive test. Interesting thing about the 775, its sponsored partly by the NWS, and they run nets on it.


The daily weather net is at 6:45 am (local) on the 146.775 repeater.

stj 02-11-2018 11:27 PM

Re: 2m/70c Radio battery eliminator build
if you program it with CHIRP you can extend the frequency range a fair bit

goontron 03-23-2018 08:53 PM

Re: 2m/70c Radio battery eliminator build
7 Attachment(s)
So, i just wanted to post an update. I got the MFG's battery eliminator, and surprise surprise, it's an older design, same spec, with less filtering and no AC bridge. And a fuse.

Glory shot

Houston we have a problem. Why is the cord coming out the bottom? Well that won't sit in a cup holder!

Houston, another problem. Dead short on the input! Diode pushed into the heatsink. Easy fix. Also, Focus you FAK!

ChengX caps. This is actually probably one of the better applications for these caps....

Board overview. These is why i say old design. Single layer board, that chip was designed to be a simple retrofit with minimal redesign of the board from a linear regulator according to the datasheet, and it switches at a paltry 52Khz, compared to the 1Mhz in the one i built.

The underside shows much room for improvement...

Now for the reason i got this. It looks a hell of a lot better than a lighter plug to banana plugs, then a set of roach clips hooked onto them.

I personally don't care, but my boss very well might while im opertaing a company truck. Though, with how the inverter is wired in......

So, thats my excuse for getting it. Being able to see how close my design was compared to one built by the maker of the radio, was just a nice extra.

eccerr0r 05-16-2018 09:08 AM

Re: 2m/70c Radio battery eliminator build
how long did that battery last before it became unusable and ripe for becoming a battery eliminator cartridge?

goontron 05-16-2018 09:13 AM

Re: 2m/70c Radio battery eliminator build
^ About half a year and a couple seconds in my morning coffee...

eccerr0r 05-16-2018 09:22 AM

Re: 2m/70c Radio battery eliminator build
Couldn't find another way to get your daily lithium dose? :D

Hmm... I might be forced to get a cheapie radio, curious about the battery management on these devices and how long the cells last before they become unusable.

goontron 05-16-2018 09:24 AM

Re: 2m/70c Radio battery eliminator build
^ Well, the Yaesu i have is good for 300 cycles, and its far from a cheapy radio.

eccerr0r 05-16-2018 09:40 AM

Re: 2m/70c Radio battery eliminator build
Crap, I was about to ask how many cells it was, but at 7.6V it must be 2-cell, answered own question.

Why? At that point, it starts separating the cheapie and the better designed battery packs/systems... I also suspect there's no internal SMPS inside the HTs to boost voltage and thus power output/range goes down as battery runs down too (at the expense of noise generated by the SMPS?)

goontron 05-16-2018 10:38 AM

Re: 2m/70c Radio battery eliminator build
^ Current draw increases.

eccerr0r 05-16-2018 12:15 PM

Re: 2m/70c Radio battery eliminator build
Interesting, so there is a boosting regulator in it for when the battery drains down...?

stj 05-16-2018 12:46 PM

Re: 2m/70c Radio battery eliminator build
well, the UV82 battery is 7.2v Lithium-Ion and the charger is a slow charge at something between 8 and 10.5v i dont have it to hand to check.
the battery has internal protection and the charger has a chip in it - i can pull the exact details from another pc later.

i should also have the UV5r schematics.
i'm pretty sure there is no boost, just direct battery for the transmit circuit, and a regulator before the digital stuff.

stj 05-16-2018 12:49 PM

Re: 2m/70c Radio battery eliminator build
btw, if you buy a radio, the UV82 is the one to get.
better speaker than the others and double PTT buttons that you individually assign!!

eccerr0r 05-16-2018 01:01 PM

Re: 2m/70c Radio battery eliminator build
Interesting. So I need to get a radio with published schematics!!! :D

stj 05-16-2018 01:09 PM

Re: 2m/70c Radio battery eliminator build
not much in them, they use digital direct conversion and modulation.
if you expect a bunch of cans and coils your not going to find them!!!
that's how they got them so cheap, they are almost software based.

stj 05-16-2018 01:11 PM

Re: 2m/70c Radio battery eliminator build
your gonna like this!!

All times are GMT -6. The time now is 07:16 PM.

Powered by vBulletin ®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.