Author Topic: DIY Handheld Radio External Battery Pack  (Read 5558 times)

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GreekMan

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DIY Handheld Radio External Battery Pack
« on: April 27, 2013, 04:11:41 AM »
edit:
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…

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 (green)

One more pic showing the wiring in more detail.



(the black wire (ground) 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
« Last Edit: May 12, 2013, 12:43:16 PM by GreekMan »

Tempstar

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Re: DIY Handheld Radio External Battery Pack
« Reply #1 on: April 27, 2013, 06:11:11 AM »
Nice job and a great looking pack! What antenna do you have on the HT?
"Preparedness is a lot more than just buying stuff"

GreekMan

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Re: DIY Handheld Radio External Battery Pack
« Reply #2 on: April 27, 2013, 11:38:45 AM »
I honestly don;t know. Its a Midland whip 30cm long....

GreekMan

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Re: DIY Handheld Radio External Battery Pack
« Reply #3 on: May 12, 2013, 12:28:47 PM »
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 handle the current steady and for how long , or how reliable ti is but the things is tempting!

GreekMan

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Re: DIY Handheld Radio External Battery Pack
« Reply #4 on: May 12, 2013, 12:42:33 PM »
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…



spacecase0

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Re: DIY Handheld Radio External Battery Pack
« Reply #5 on: May 15, 2013, 03:16:12 PM »
I have been playing with lithium cells for a while now,
and if you are using the 18650 cells I expect it will be somewhat unlikely your pack will catch fire on you,
but if you did the same thing with 14500 cells it would be way more likely
still the protected cells are way better as you don't have to charge the set in a fire proof area
also if you run protected cells and charge them all in parallel it works out better

GreekMan

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Re: DIY Handheld Radio External Battery Pack
« Reply #6 on: May 30, 2013, 09:14:02 AM »
Your concerns are real....
But the batteries will be charged individually. Since they are removable it is MUCH simpler than using a hobby charger and balancing leads etc etc.
Inddeed unprotected batteires in series are an issue, especially since they are not protected (these will nto fit in the slots)

BUT,
 I have recently found this too.
http://www.fasttech.com/products/1009/10002230/1161600-2s2p-74v-18650-holder-with-battery-build-in-pcm-pr

It outputs the desired 7.4Volt ANd has a built in protection circuit....
the onyl downside is that it is not in a box form....

spacecase0

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Re: DIY Handheld Radio External Battery Pack
« Reply #7 on: June 04, 2013, 05:01:40 PM »
that is a very neat battery holder,

I was looking at these
http://www.electriccarpartscompany.com/40Ah-32V-br-46L-19W-73H-in-br-117-47-186-mm-br-34-Lbs-153-Kg-br-Sinopoly-br-EV-LiFePo4-Lithium-Prismatic-Battery-br-Model-SP-LFP40AHA_p_259.html
but it will be 14 pounds for a set of 4 to run my radio on
and your 18650 holder may work better,
I will have to think more on what to get now.

GreekMan

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Re: DIY Handheld Radio External Battery Pack
« Reply #8 on: June 06, 2013, 12:43:37 AM »
do notice the safety issues and that it is a Small contraption.

I demostrated the battery pacl in a local HAM Fest and got interesting input on it.
Some guys that do SOTA use LiPo battery packs from the RC market.
these are a bit over the voltage range for a HT , but they fix that with a zener diode.
« Last Edit: June 06, 2013, 12:46:08 AM by GreekMan »

spacecase0

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Re: DIY Handheld Radio External Battery Pack
« Reply #9 on: June 06, 2013, 12:54:06 AM »
I had not looked at the RC hobby batteries,
that is a great idea.

GreekMan

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Re: DIY Handheld Radio External Battery Pack
« Reply #10 on: June 06, 2013, 10:27:12 AM »
keep us posted on your setup!

GreekMan

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Re: DIY Handheld Radio External Battery Pack
« Reply #11 on: January 16, 2015, 12:25:15 PM »
I finally updated it with a voltage meter. Voltage sag is 1.2 volt from the 8.2V open circuit (old batteries too)

Pics:








GreekMan

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Re: DIY Handheld Radio External Battery Pack
« Reply #12 on: August 09, 2015, 12:18:49 PM »
today i did the preliminary work on the 2nd and the 3rd model


output will be 7.2V for my Bao


output will be 13.8V for my Kenwood Th-F7