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!

11 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.

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