Author Topic: DIY Handheld Radio External Battery Pack  (Read 5996 times)

Offline Greekman

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DIY Handheld Radio External Battery Pack
« on: April 27, 2013, 03:17:32 AM »
Here is a battery bank I did for my HT.



It uses this battery case.
https://www.fasttech.com/products/1286603

I had to rewire it for 2series-2parallel since my radios battery is a 7.4V.
Then I added the RCA plug and the fuse holder.



I had to work new holes in the place of the existing ones, so I added a new wall to host the plugs. It is made from a DVD case, epoxied on and soon I will be adding supporting structures in the area the original PCB screw points are

For batteries I will be using 4 Samsung 2600 (pink) in the 18650 size. Cheap and of good capacity are a best buy for this application. Alternatively one can use the Sanyo 2600 (red) or the Panasonics NCR18650B 3400 (green). With the latter it will be more than 4 times the OEM battery.

One more pic showing the wiring in more detail.



(the black wire snakes under the fuse holder and is connected to the RCA plug case.)
All other wires carry the positive current.
Fuse is a 3A one, since my TH-F7 maxs at 2A.



Then the wires end in two fake batteries that are placed in a Kenwood battery case.
It is of a good coincidence that my HT does not have a automatic battery detection feature. So I choose the lithium option from the menu and make it think it is powered by the original lithium battery (7.4V, 1550mAh).
Also it does not use 3 contacts for the OEM lithium battery, just two. This is most critical cos I do not know how this would work with the radio was using a 3rd contact to monitor nattery state. Being dump proved to be helpful in this case

Issues to be resolved…
- I have observed some voltage drop from the 18650 batteries to the battery case. (to be expected with some many connections). I have yet to measure it and see how to limit it.
- I have not yet monitored how the battery measuring feature of my HT corelates to the power available of the battery bank.

That is all for now….Greekman

Offline viking

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Re: DIY Handheld Radio External Battery Pack
« Reply #1 on: April 27, 2013, 06:18:08 PM »
Nice job!

Offline backwoods_engineer

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Re: DIY Handheld Radio External Battery Pack
« Reply #2 on: May 02, 2013, 01:59:41 PM »
Nice work, but I suggest next time you use Anderson PowerPole connectors.

Offline Greekman

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Re: DIY Handheld Radio External Battery Pack
« Reply #3 on: May 04, 2013, 05:13:15 AM »
yep I know about them.....
But it is an expensive proposition to order them. Especially since the USPS international postage prices have skyrocketed
No one else uses them. Even if the RCA are a stange option i will not be them first oen that uses them in my area.
It has become very hard to procure parts. what you see are left-overs in my local market. I.E I will have to special order mic sockets for cases. No one wants to stock these items anymore.
A.P.s are very big for this application...

Offline FreeLancer

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Re: DIY Handheld Radio External Battery Pack
« Reply #4 on: May 04, 2013, 10:14:45 AM »
That's cool!  I want to try making some 18650 battery packs.

Offline Greekman

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Re: DIY Handheld Radio External Battery Pack
« Reply #5 on: May 05, 2013, 01:03:09 AM »
If you need help in the process, howler....

But first check on your HT, especially the battery contacts thing

Offline Greekman

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Re: DIY Handheld Radio External Battery Pack
« Reply #6 on: May 12, 2013, 11:28:13 AM »
Days after this construction I found this!

http://www.fasttech.com/products/1420/10004461/1341503-qidian-4-piece-3a-1-418650-dual-usb-output-mobile-

I really do not know if it can keep the current steady and for how long, or how reliable ti is but the things is tempting!

Offline Greekman

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Re: DIY Handheld Radio External Battery Pack
« Reply #7 on: May 12, 2013, 11:44:00 AM »
Important Safety Notice…..

There is a safety issue with the way the batteries are connected in this power bank (2 series – 2 parallel)
Lithium Ion batteries in series are not a good idea without a protection circuit (either a common one like your laptop battery or an individual one in the bottom of each battery).
The theory is that dissimilar batteries put a stress on the weaker one, or the weaker gets its polarity reversed if it gets exhausted and still receives current from the other ones>Then it may ignite.
Monitoring the remaining charge and using matched batteries from the same lot will limit the possibilities of a mishap, but it still your own calling…

(moderators reading this, could you edit my 1st post and add this in it?)


Offline idelphic

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Re: DIY Handheld Radio External Battery Pack
« Reply #8 on: May 13, 2013, 08:11:51 AM »
I don't have the radio any longer,.. rather wished I did.  But I had a Kenwood Th-22 as my first HT.  The battery of course went south after a few years of steady use.

My Elmer and Electronics / Computer Mentor had the Dual band cousin the TH-79/79.  When the battery went on his, he hack a old cell phone battery to use. 

At the time, we both had a PrimeCo cell phone, It was a cool phone at the time and just before the Startek came out from Motorola.

Keeping all the electronics in the battery pack, we cut out the old cells from the radio, and soldered in the PrimeCo battery pack which is the same LI batteries, but it included the PCB controller.

I don't remember the performance after the modification,.. but the radio would seemingly last for 2 full months before needing a fresh charge.

Offline Greekman

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Re: DIY Handheld Radio External Battery Pack
« Reply #9 on: January 16, 2015, 11:23:52 AM »
I finally updated it with a voltage meter. Volateg sag is 1.2 volt from 8.2 open circuit (old batteries too)

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