This is my third article about batteries for the Yaesu FT-817 in my blog. But it is the second article translated to english. I am sorry, but i started the translations with the fourth article (LiFePO4 batteries)
When i started looking for batteries for the FT-817, i found the lithium batteries with 18650 size (18x65mm)
Most of these batteries, are made with voltages between 3,6 and 3,7 volts, and current capacities around 2000mAh.
Exploring the web about 18650 batteries, i found several videos about how to change old and exhausted cells 18650 that are into computer battery packs.
I read, a few years ago that mobile phones or computer batteries, die due to failure in the charge/discharge electronic circuits .
Suddenly i thought, why not to try recycling this batteries? I had two old battery packs from my old Compaq Presario.
Why don’t try it? I had to open the container and remove the electronics. Then, i had to try to recover the batteries because, surely, it would be died
In the photo shown above, you can see these batteries. A box containing usually between 6 and 10 Li-Ion cells .
To open the box, a well sharpened cutter is needed. Be careful, it’s too easy to get an injury on the process.
And be careful again, try to open the box with the cutter slowly. You must not drill any cell.
Once the box is open, you can see something like this:
As you can see, there are 4 blocks of 2 cells in parallel. The electronics are deprecated. The balance wires and power wires are deprecated too. Then select 6 cells to build the battery pack.
I use 6 cells instead of 8, because Li-Ion cells have 3.6-3.7V. But after a full charge, his voltage is 4,1-4,2V. So, 8 cells in 4 serial blocks would have been 16.8V. Too much voltage for the FT-817. And the FT-817 is tested with 8.9V and working OK.
If you purchase new batteries, go to the next paragraph. But, if you recycle a old battery pack from a computer, now you have to check if the old cells are usable and if you can charge it. If you can not charge it, search in the web about recover lithium batteries.
Once received the new cells or recovered and charged the old cells, join the cells with melt glue and solder the cells in 3S2P configuration. You are free to do the pack form.
Then you should solder the power wire. It will be used to power the transceiver and to charge/discharge the battery.
I have used a old food container from Ikea. Its small size is enough to hold the cells, and even space left for something else.
I have used a pair of 30A Powerpole to connect the battery to the FT-817 and to charge or discharge it.
And it is the box with the battery into it.
Batería lista para el ataque
I use 6 cells insted of 8, because Li-Ion cells has 3.6-3.7V. But after a full charge, his voltage is 4,1-4,2V. So, 8 cells in 4 serial blocks would have 16.8V. Too much voltage for the FT-817.
So, the nominal voltage of this battery is 11.1V. At full charge is 12.6V.
If you recycle a old computer cells, it is possible to find that the cell voltage is too low or zero. It is a critical point. Recover a cell wich is difficult, even impossible. There are not magic recipes. There are several methods to recover it. But, please, search in the web and be careful, Li-Ion are dangerous.
I recovered them using the Ni-MH program of my Imax B6 charger. Once the cell has 2.7V the program was stopped and after that, the Li-Ion program was used.
The real capacity of this pack, measured with the Imax B6 charger, was over 4400mAh.ra Really good.
The weight of the pack is around 300 grams. Really good, a SLA battery of similar capaciy weight about 1400 grams.
Regular 18650 Li-Ion cells are made with a discharge capacity of 1 or 2C. That is, if the cell has a capaciy of 2000mAh, the discharge capacity would be betwen 2000 and 4000mAh.
This battery pack was made of 3 blocks of 2 cells in parallel. So, the maximum current would be 8A.
But, if you want a really powerful battery, with high discharge capacity, look at my LiFePO4 battery pack.