Hi,
I’ve been thinking.
My Yaesu FT-817 has an internal, rechargeable battery pack. 1400mAh.
Not big, does the job, I rely on slabs usually when out on an activation.
However, radio also came with an internal battery clip FBA-28 which takes
8 x AA cells.
So, my thoughts went along the line of…ditch the internal battery and load the radio with 8 x rechargeable cells. This could give me 2900mAh 
But - the instruction book tells me bad things will happen if I load this clip with anything other than conventional AA cells. hmmmm!
Why?
“Do not attempt to use Ni-Cd or other rechargeable cells in the FBA-28, because it does not contain the protection circuitry required when using rechargeable cells.” - Yaesu handbook.
I don’t intend to try and charge the cells when in situ in the radio…where’s the harm…or am I being thick?
In reply to G1STQ:
I have used this battery clip with high capacity NiMHs for some years. It is necessary to cut and insulate the green wire after which you can charge the cells in the box just like the battery pack that is provided. I have never had any problems. Go for it!
73
Brian G8ADD
In reply to G1STQ:
You do the green wire mod and that allows you to charge up NiMHs in the battery holder. You’re not being thick at all and the warning is there for a good reason. Without a thermal fuse amongst the rechargable cells there is a possibilty of one cell eventually overheating and catching fire. All (most) commercial rechargeable packs have a thermal fuse in circuit that will open circuit the pack should the temperature rise enough.
So no thermal fuse is a possible fire risk. It is a very small risk and so Yaesu are correct to tell you not to do this so that should you burn down your house you can’t sue them. The likelyhood of this very small but significantly greater than zero. Now I would imagine the majority of 817s have had the green wire mod and there haven’t been reports of hams burning themselves out of house and home yet.
So you can snip the wire (mine has been done) and charge up cells in the radio. Wait, there’s more though. You don’t want to really charge the cells this way for a few reasons.
-
The 817 charging circuit is pants. Utter pants. It charges at a fixed rate for 6hrs or 10hrs. There is no overcharge detect or voltage/temp charge cutoff. It’s designed to charge the battery packs but it’s a poor design. To charge a 2900mAh cells would require around 3x 10hr charge cycles. That’s a mighty long time.
-
It charges the cells in series. This is a bad way to charge multiple cells. They don’t all discharge or charge at the same rate and so you risk overcharging some cells.
The ideal way is to use a parallel charger that conditions and charges cells independantly. To do that you need to remove the cells from the radio. I bought a 6 cell smart charger a few years back for £9.99 from Aldi/Lidl and it works fabulously as do the 2400mAh cells. It charges much faster too. All modern NiCds/NiMHS can be fast charged.
If you have to remove them to charge them then there is little point snipping the wire! But it is worth doing. You charge the cells every 2nd/3rd cycle fully in the external charger and give them a boost in the 817 a few times. This works well if you don’t completely flatten then cells. The full parallel charge will sort out imbalances and you should get the best of both worlds.
Andy
MM0FMF
In reply to MM0FMF:
Thanks Brian ans Andy for your replies.
Very interesting.
Much more to this than I thought.
I have spoken to Micky (M6MMM) who deals in batteries and he is going to get me one of those chargers which charge each cell separately and some fresh 2900mAh AA cells.
It will be interesting to see how the radio performs on AA cells. Should make life much easier, especially in the rain - the radio can stay in my rucksack.
Thanks again for taking the time to reply to my question,
Cheers,
John
In reply to G1STQ:
Just about everything you want to ask/know about the FT-817:
73
Graham G4FUJ