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/1286603I 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
