Personally I prefer 500 Hz as I'm in Australia and the bands are fairly quiet. But those in more densely populated areas might got for a narrower (250 Hz) filter. Installation ie easy and requires no soldering. I have 2 of the Zippy LiFePO4 4200mAh and find them pretty good. I get about 5-6 hours out of 1 on my 817 and weigh 480gm each and a decent size (you can fit 3 or 4 lengthways on an 817).

Windcamp 3000mah lithium battery kit for yaesu ft-817 - eHam.net

The battery cover fits perfectly, the battery is very close to the announced capacity and it has overcurrent and surge protection. The FT-817/FT-818 has a wide voltage range but you want to avoid a battery that gives around the extremes of this. Too low a voltage (eg 8 - 9 volts) will mean the FT-817/FT-818 won't be able to put out its full 5 watts What is not apparent from this is that the compressed transmission is narrower and cleaner. That's because without the compressor, the FT-817's ALC is providing the compression. I have done what most FT-817 owners probably do, and turned the SSB mike level up to get a louder signal, at the cost of a bit of splatter. The RF compressor cleanly reduces the peaks, as well as bringing the lower levels up, so the ALC doesn't have to work so hard. The end result is a louder but cleaner signal. Whether that's worth the cost is your decision. Working CW

No obscenities, discriminatory, abusive, or other content not suitable in public or for younger readers. Can I ask if you have considered an internal LIPO rather than external ones? There is a flat 2.5Ah 11v 3S lipo that sits nicely in the battery bay in the FT817 and by my experience will give a good two hours activation on 5W SSB output. I've had good results from sealed lead acid (cheap but heavy), NiMH and, more recently, LiFePO4 battery types. Note that the latter is quite critical with charging and if you leave it for a while its voltage It’s basically a nicely designed 3D-printable part for 3 x 18650 Li-Ion cells, load balancer, fuse, etc. Thanks to a new cover, the cell can be charged while inserted in the rig. The good news is that when operating on the 2.5W mode (the default for battery power) the FT-817 appears to deliver the full 2.5W regardless of SWR. I guess this applies to the lower power modes too.

W4RT Electronics - WiMo

You probably do want an external charge connector so that you can balance the cells from time to time, and possibly charge them faster than the FT-817 can. But I see no harm in letting the radio charge them. It will provide a useful and convenient top-up charge. Clearly you mustn’t use both charging methods at the same time (I presume this is why the battery tray that started this thread provides a switch). If you don’t want the radio to charge the cells in any way then you need the green wire connecting. I hear stories about the volatile nature of 18650s so I am leery about making this without talking to someone who has already successfully built and used one. When the power goes off don't just sit around at home waiting for it to return. Instead find a battery, fire up the FT-817/FT-818 and savour the temporary pleasure of exploring the unusually quiet bands. The bad points outnumber the good points. Whilst some allowance must be made for the FT-817's small size and portability, especially with regard to ergonomics, several of these criticisms could have been averted using existing technology.A surprising number of FT-817/FT-818 owners use their rig on HF, and maybe VHF/UHF FM repeaters, but not on VHF/UHF SSB. Only 2.5W on battery power. The FT-817 is advertised as a 5W radio. But on battery power the maximum output power is normally 2.5W. This can be overridden, but bearing in mind the limited battery capacity this may not be a good idea. But it's disappointing. Let's face it, out portable you are probably going to be using a pretty inefficient antenna, so being limited to 2.5W as well isn't going to help. I recently received one of these and installed it in my 818 last light. It is now going though a "full time receive" cycle and so far the battary lasts significantly longer - let's see after a few cycles. The most comprehensive computer control program for the FT-817 is FT-817 Commander. This program is the predecessor to Ham Radio Deluxe, but it has many features specific to the FT-817, such as memory management, which HRD does not. Although FT-817 Commander is unsupported, and does not claim to support the FT-817ND, it appears to work, although I have not used it a lot.