What external battery do I pair with the Icom IC-705?

I typically pair my IC-705 with a 6 aH Bioenno LiFEPo battery pack (the blue battery between the transceiver and tuner above).

Many thanks for QRPer reader, Ron, who writes:

Dear Thomas, thank you for the great videos and information on POTA and QRP work. I’m very inspired.

Thomas, I received an Icom 705 recently and I was wondering about power. In your videos, is your battery 12 volts? This works okay? I wonder because of the 13.8 volt requirement in the manual.

Thank you for your time. I’ve already picked out a park that I will try to activate one day when I’m up to speed on POTA. 72 Ron

Thanks for your question, Ron. I’m very happy to hear you find the videos useful.

I almost exclusively use Bioenno LiFePo 12V batteries which actually output closer to 13-13.5 volts in use and can even briefly be a bit higher immediately after charging.

Most amateur radio transceivers (including the IC-705) typically have a bit of voltage flexibility and will operate a below 12 volts and tad higher than 13.8 volts. QRP radios especially. You’re wise, though to always check (the MTR-3B is a notable exception as it prefers a max of 12V).

In fact, I just checked the IC-705 specs and its voltage requirements are 13.8 V DC ±15% (12V – 15.87 volts). The IC-705 can actually run on much lower power because the Lithium Ion pack that is supplied with the IC-705 (BP-272) is only 7.4 VDC when charged.

I would suggest you check out a 4.5 or 6 aH LiFePo battery like this one at Bioenno. Either would have the capacity to carry you through a few hours of heavy use.

Of course, there are many, many more battery options out there, but I’m a fan of LiFePo batteries for their longevity, capacity, and stability.

Hope this helps!

16 thoughts on “What external battery do I pair with the Icom IC-705?”

  1. Can I connect the aforementioned batter directly to the radio or do I need to run it through something else first?

    1. Hi, Christopher,

      Since the power cord that accompanies the IC-705 has two in-line fuses, you can connect directly to the battery. I typically bring a small Powerpole distribution panel so I can connect other 12V devices if needed.


  2. Dead wrong.
    That radio will default back to 5w transmit if there is not enough power.
    It wants a 16v battery.

    1. Actually, Brad, the IC-705 wants 12 VDC +/- 15% to run a full 10 watts. 16 volts is *way* over the amount the IC-705 can handle and could very well damage it if overvoltage protection doesn’t kick in.

      All of the Bioenno packs I mention are 12 volts, so ideal for the IC-705 and most of the portable transceivers on the market today. The amp hour rating has everything to do with capacity and nothing to do with voltage.

      The IC-705 will also run on 7.4 V DC with the BP-272 battery pack, for example, but maximum output power is decreased to 5 watts.

      Please don’t try to feed your IC-705 16 volts. You might let the smoke out.


    2. Be careful when making comments like “dead wrong” when you are the one that’s incorrect. That’s how bad information spreads.

  3. Hi Thomas.
    As far as I know we can’t get Bioenno batteries in the UK. Do you use a dedicated Bioenno charger? I ask because I’ve spotted 6Ah Bioenno equivalent but it’s not clear how I would charge it.

    I really appreciate your brilliant site and the effort involved in putting it together.
    Thanks, Bern G8KVM

  4. Brad, have you used the IC-705 with a 16V battery? I would assume the HI Voltage warning would show on the starting screen?

  5. Hi folks. I am having a weird issue with my 705; after I finished charging the Bioenno 12V 6Ah battery (BLF1206A), when using the PO scale on the 705, it would switch rapidly between 5W and 10W on receive. This wasn’t the case a few days ago. Any ideas?

  6. Good day…So first thank you for all the good information. I am looking at purchasing the 12v battery you are using with your Icom 705 for 10 watt operation in the field. Can you tell me if I can use the Icom 705 DC charger to also charge the Bienno external battery to full capacity? I believe the Bienno charger is 2 amps, the Icom is 6 amps , connectors are both DC. I am trying to eliminate extra gear to carry. Thank you

    1. Hi, Frank,

      This would be a question for Bioenno. You might contact them. I’m not familiar with the Icom charger you’re mentioning, but I can tell you that the Bioenno battery is LiFePo4 and has its own internal BMS (battery management system) that expects a certain amount of charge voltage. The Icom battery packs are much lower voltage.

      Again, perhaps you can look up the specs and output of your Icom charger, then contact Bioenno.

      1. Thank you for the quick reply, and yes you are correct in your suspicion, after contacting Bioenno they confirmed the 705 charger would not work to charge their battery.

  7. Is it possible to charge the battery and operate at the same time?

    Chinese LiFePo battery pack has a charger that creates a 59+ noise on HF when plugged into mains.

    1. Yep! Either through the USB connector, or the barrel connector – both will work. There’s a setting in the radio that controls this, so you may need to change that setting if it’s not working for you. If using USB, you’ll stay at 5W max TX power. If you power/charge through the barrel connector (and maintain 10V minimum), you can get the full 10W TX power.

  8. How about an Anker Prime 27,650mAh Power Bank (250W)? The USB-A port puts out 1.5A at 12V or 6.5A at 10V.

  9. I realize this post was from a few years ago, but this information should still be useful to 705 owners. Icom states the input voltage should be 13.8 +/- 15%. That’s 11.73 to 15.87 volts. I’ve done some testing and found that as long as you maintain 10V (on TX), the radio will stay in full power mode (10W). A 4-cell LiFePo4 pack is right in the perfect range for this and should provide 10W TX power pretty deep into the discharge range, until the voltage starts to drop below 10V on transmit. It’s better for the battery to not discharge it quite that low, however.

    I’ve run my 705 some interesting ways:

    -Internal battery only, but with a small folding 30W solar panel that provides 12-14V. That gives pretty much unlimited run time at 10W in the sun, only occasionally dropping to 5W if a big cloud rolls in. I use a 12V USB PD trigger from my solar panel’s USB output, into the 706’s barrel connector (needed to tell the panel’s USB connector to put out 12V, not the default 5V. This is also needed if you run a USB battery pack, or it will also default to 5V output.)

    -External 4Ah LiFePO4 battery for constant 10Ws, with the solar panel keeping it topped up. In this mode, I use the un-regulated 14.4V (max) output from the panel’s barrel connector. It’s the perfect voltage for charging a LiFePO4. The panel adds weight to the rig, but results in generally unlimited run time.

    If you look on Amazon you can find 4-6Ah LiFePO4 batteries for $20. You can run it as-is, or if you want to save some space you can disassemble it and you’ll find a 4 cell pack with a BMS attached, and a bit of empty space. Attach new leads with PowerPoles and you’re good to go. I have a pack I pulled out of a 4Ah Timeusb battery that’s now the same size and shape as a Bioenno 4Ah pack (it uses the same size battery). It cost me $18 and works like a charm. Not all hams are electronics tinkerers though, so when in doubt, you can’t go wrong with a nice Bioenno.

    Li-ion cells aren’t quite as convenient as LiFeP04 because their cell voltage just doesn’t get us into the right range. A 3-cell pack has a nominal voltage of only 11.1V, and drops below 10V too quickly, while a 4-cell pack’s voltage can be well over 16V when fully charge; a bit too high for comfort over the maximum specified input voltage for the 705 (and most “12V” radios).

    1. Correction: I run a 15V USB PD trigger. My solar panel happens to be limited to 12V USB output., and the PD trigger simply negotiates the highest voltage it can, 12V in this case. Also note, PD triggers are not DC-DC converters; they contain a small IC that communicates with the USB power supply (or USB battery pack, solar panel, etc) to request a voltage higher than the default 5V, as per the USB Power Delivery standard. Any RF noise from external portable power will be from the DC-DC converters in the battery pack or solar panel, not the PD trigger. You just have to test anything you plan on running. A 4-cell LiFeP04 should give you clean, direct power with out any switching noise, but I’ve also been lucky with any solar panel or USB pack I’ve run.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.