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Blown final club? I think I have a membership

 

Ken
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a bit off topic... what kind of run time do you get with the NiMH batteries in your 897? I've gone though about a half dozen battery packs over the years and I've never been happy with the run time.
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?But ?like you said, they fit so nicely in the case
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Mik wb8vge
 

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I bought my FT-897 with 2x dead batteries, I've never gotten either to hold a charge. When googling replacements, I was surprised to see availability on Amazon, but never bought a pair. Like many other FT-897 owners (I assume) I'd love to get either a LiPO battery pack that fits in the chassis OR a nice AC power supply, but so far no luck...

(And it's sorta on-topic, since there is so much similarity among the FT-8x7 family of radios... ;^)

Ken, N2VIP

On Aug 9, 2024, at 11:29, Mike Bryce <prosolar@...> wrote:

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Ken
?
a bit off topic... what kind of run time do you get with the NiMH batteries in your 897? I've gone though about a half dozen battery packs over the years and I've never been happy with the run time.
?
?But ?like you said, they fit so nicely in the case
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Mik wb8vge
 

Ken, N2VIP wrote¡­

I'd love to get either a LiPO battery pack that fits in the chassis OR a nice AC power supply, but so far no luck...
I would go with LiFePO4. It is slightly lower energy density than LiPo but a lot safer and it can tolerate deep discharge a lot better. You might get several thousand charge-discharge cycles out of them, especially if you don¡¯t take them right down to zero. As well, they actually hold the voltage very steady rate until the very end.

An AC Power supply is always good to have. A switching supply will be a lot lighter, but watch out for RFI. Another option would be one of the larger USB-C PD battery power banks with power delivery. I don¡¯t have one but INIU seems to have a good reputation.

--
73 Keith VE7GDH
 

joe and the group,
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Yaesu had a 'thing' for using timers to control battery charging. I have a drop in charger for my FT411 handheld and it uses a timer to charge the battery. One issue, is the battery is charged and you lift the radio out of the charger and back in, you start a brand new charging cycle even though the battery is already charged!
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Mike wb8vge
 

Which can result in an overcharge depending on what the charge circuit is. SMH.

Joe?
N1KHB?


On Sun, Aug 11, 2024 at 10:40 AM, Mike Bryce
<prosolar@...> wrote:
joe and the group,
?
Yaesu had a 'thing' for using timers to control battery charging. I have a drop in charger for my FT411 handheld and it uses a timer to charge the battery. One issue, is the battery is charged and you lift the radio out of the charger and back in, you start a brand new charging cycle even though the battery is already charged!
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Mike wb8vge
 

The FT817/818 charge circuit would not really cause issues if "overcharging". The radio is built for NiCD / NiMH cells and the charging regime is 14 hours times 0.1C, so 14 hours times 10% of the capacity of the cells. The "fourteen times 10%" is to make up for losses in the charge / discharge process; "ten times 10%" would charge the cells but the process has losses. Hence 14 hours.

However, NiCD cells no longer exist (environment!), and NiMH cells have grown in technology. I think the original packs had a capacity of roughly 700 mAH, so a charge current of 70 mA. Today's cells are often closer to 3000 mAH, and hence a 70mA charge current won't charge the cell in 14 hours, you need much more than that.
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With a low charge current like this, "overcharging" won't affect the cells unless you do it continuously. The cells will dissipate the energy they can't store. They get warm, but not hot. The amount of energy is not very high.
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The charge circuit is just a current source. If you look at the schematic, it is Q1103 with R1435 defining the charge current and Q1101 enabling the circuit.
There is a second charge circuit, Q1105 and R1436 with Q1102 enabling. This is a trickle-charge as NiCD/NiMH are known to self-discharge.
The "green wire" disables both charging circuits (charge and trickle) which is just as well because trying to charge alkalines is likely to cause them to leak.
I have changed R1435 to match my cells; you will need to revise yourself if you want to do this, and please mind the dissipation and max Ic for Q1101 and Q1103; I have not blown my finals but I *have* blown the charging circuitry at some time.

To add, the FT817/818 doesn't charge 14 hours, but selectable 6-8-10 hours. The result is that even a 10-hour cycle won't get close to charging them modern high-capacity NiMH cells and two cycles won't hurt the cells. We're not talking "ultra-speed 30 minute fill charge", the battery chemistry is 30 years older.
 

Average Ham does not mean much these days.? Most repair of Ham gear is not that hi-tech.? Yaesu hires high school drop outs to do it.
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And replacing the FT817 PA finals on the is not that difficult.? If think so no you should not be inside the radio.
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Once when my finals blew, I did order and install the PA board.? But when the finals died so did the driver transistors on the main board. SMTs, easy job to replace once got the parts.? Do need the right tools, mainly a very small pencil iron and small solder, not 035".? I have just such an iron I use for SMT with 0.050 pins.
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73, ron, n9ee

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