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Τρίτη, 9 Φεβρουαρίου 2016

Battery Banks for Handheld Radios

A Battery Bank is a useful addition to one’s radio gear ‘cos it extends the use cycle away from the grid.
Depending on how you radio charges there are ready-made or DIY solutions, and these we will explore in this article.

Radios that Charge by USB

The Baofeng UV-3R MkII and the Yaesu VX-3 (AFAIK) radios charge by a USB power source. So things are easy in this case. You just use a modern USB powerbank.


Some buying guidelines:



- Buy name brand powerbanks. The Anker, Xiaomi and Blitzwolf ones are safe choices, but the power bank world does not end there. Just be cautious of the cheap, inefficient ones.
- There are many charging protocols out there. Samsung, Apple, the generic DCP, etc. Modern powerbanks automatically recognize the protocol, so buy ones with this feature. This will not be required by the radio, but it helps buying once and covering your cell phone needs.

Radios that Charge and Operate by 12V straight on the Radio

You will have to research your model. My Kenwood TH-F7(6) does, and my research shows that the FT-60R also does.
In handheld radios actual maximum input voltages range from 13.6 to 16-19V DC so check before you buy.

Enter the 12V powerbank.


Yes, there are powerbanks that output 12V DC, courtesy of the modern power hungry devices like tablets and small laptops. Just search Amazon for "12V powerbank"
Their power output ranges from 1.5 to 4.5amps (and a lot higher for the car starting models). This is well ahead of the HT radios charging Amp draw and within specs of the HT draw on transmit (2A for the TH-F7 and 1.5A for the FT-60R).
The Anker Astro Pro2 series are a tried and used option. It also powers the FT-817D QRP radio.


(note: I did not had the chance to try one on use. If the HT has some peak draw over the spec'ed I do not know how the powerbank will act, like tripping a fuse or a protection circuit, etc).

On 12V  powerbank wiring.
Most 12V powerbanks have a female DC connector of 5.5x2.1 or 5.5x2.5. Radios have a female jack of either 3.5x1.1 or 3.5x1.35. You will need an adapter cable or better yet, make your own with quality 0.5-1mm cable like I do.

DIY 12V Powerbanks.

There are some ways to have 12V DC current on hand.

Recipe 1:
The classic RC Li-Po battery at 14.4-14.8 volt. You will have to make your own wiring probably. But this is where my knowledge stops.

 



Recipe 2:
In short, a lithium ion battery pack (4series at 16.8V) + a DC-DC step down converter + wiring. The writeup for mine is here.


Recipe 3:
Ten rechargeable AA batteries in a battery case plus the necessary wiring. The writeup on a build is here.

Radios that Charge by 12V on the Cradle.

Most of the Chinese radios and the Yaesu FT-60R do.

In this case things are the same like above, but you will have to carry the cradle around.
DC sockets usually are 5.5x2.1mm, so you will be able to find a ready made cable to connect to your 12V powerbank.

The Bicycle Lights 7.2V Powerbanks.

There are some crazily bright bicycle lights out there and most use a remote battery pack of 2Series-2Parallel rechargeable Lithium-ions at 7.2V nominal (8.4V real). This is what most HT radios use for battery voltage.

 
So you get a battery pack like this or this and a AA/AAA battery pack for your specific radio model. You prepare the connecting wire, pass it thru a slit cut on the battery holder and terminate it on the + & - poles of the battery pack by soldering.
You are practically making a power adapter like the 12V battery eliminator for your HT radio.
If you want to maintain the use of AA/AAA batteries at the same time, you will make fake batteries out of wood and screws, like I did for my Kenwood.
You cannot get more redneck hacking than this!

A Note on Power Capacity.

Lithium batteries pack a bunch of power and contrary to the SLA ones, all the stored power can be drawn.
Assuming a 1/2 capacity use of a 7A SLA battery, my DIY powerbanks carry the same amount of stored energy at a fraction on the weight and size (somewhere around two packets of smokes and at a weight around 2/3rds of a pound).


So there you have it. A small guide on portable power for your HT. You have the options, use them!

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