Author Topic: Ham gear does not run well from 12 volt batteries...Here is a fix  (Read 5739 times)

Offline Carl

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Most Ham radios made for 12 volts actually require 13.8 to run at full power and potential and many discover the problem when attempting to work PORTABLE. The radio's often have stability problems at 12 volts and quit operating at 11.7 or so...that just will not do. I have found at least one ,reasonably priced, answer to that problem...a stable 13.8 volts at 18 Amps from this device on a battery.

https://www.amazon.com/9V-13V-Converter-Waterproof-Supply-Inverter/dp/B01N44ATHL/ref=sr_1_685?s=electronics&ie=UTF8&qid=1482715336&sr=1-685&keywords=12+volt

Offline Alan Georges

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #1 on: January 02, 2017, 08:29:37 AM »
Thanks Carl, I'm going to try one.  $33 sounds a lot better than MFJ's $160 for something that purports to do the same thing: http://www.mfjenterprises.com/Product.php?productid=MFJ-4416B

No reviews at Amazon though, and the description is kind of Engrish-y.  Have you got one, or any friends who use these?  (either way, you're about to know somebody with one!  will post a few comments after it comes in)

Even if it's not in regular use between the battery bank and radios, it'll be good to have for a possible Very Bad Day when I've got to stay on the air but unable to recharge as soon as the batteries would like.

Offline Carl

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #2 on: January 02, 2017, 09:49:42 AM »
I have a slightly lower power one with 14 amps at 13.8 regulated output and use about 5000 MFD worth of capacitors to handle 100 watt peaks on HF and NOW this new one shows up...I actually answered a question weeks ago as to what output Hams needed...guess we were targeted with technology.

Offline ID_Joker

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #3 on: January 02, 2017, 10:44:59 PM »
Please humor my stupid question....( and YES I do believe there is such thing as a stupid question!)

I have always run my rig off ac.  I have a power supply that the radio is connected to.  If i want to run off dc, this device you linked to would replace the power supply, right?  Ie it wouls be wired in between the battery and the transceiver.

Offline Carl

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #4 on: January 03, 2017, 04:47:04 AM »
That is correct, A Ham radio ,these days, is most often designed to run with 13.6 to 13.8 volts power
as is common with an auto battery while the auto is running. The radio will often produce lower power
and become frequency unstable at just about 12 volts ,while a 12 volt battery is 12.6 to 12.8 volts or so
when at rest and drops when under load of a typical 100 watt transceiver .

Modern 100 watt HF transceivers require 20 amps peak ,and more, to operate and most wet cell batteries ,
when not being charged by a alternator or charger , do not produce this level of power without voltage
sagging a bit and the instability show up. A 100 amp hour battery is RATED at a 20 HOUR discharge  rate
and a few are 10 hour rated for charge or discharge rate as the CHEMISTRY is designed ...
Another "BUG" in the setup is that batteries are not designed to produce more than 50% of their rated
power in AMP HOURS (even when used at the 20 hour ,low current rating)

So a 100 amp hour battery (twice the rated capacity of most auto batteries) is designed for only a 10 Amp rate of discharge!


### The device above in the link allows the radio to operate at full output power and stable at 13.6 to 13.8 volts
when the battery drops to below 11 volt ...but don't do this unless you have to as the battery will still suffer...

Most battery users will be well served with using LOWER OUTPUT POWER (I often only use 25 watts unless they have trouble hearing me)
and you learn little without LISTENING more than talking.

ANOTHER OPTION for battery use ,when a power supply is available....use a 120 volt power inverter (at near the same cost,often under $30)
to run the power supply and the radio will be at it's desired 13.8 volts also,though slightly less efficient ,this option allows one to not have
to carry a heavy battery when locating a radio to other locations and operating.

Always happy to explain why I do what I did, mine aren't the only answers ,but are what works for me,and others,and are often
designed by economy and ease of operation.
While they often appear to work OK,Radio output suffers quickly as the battery is used and often does not last as long as one
would guess

Offline Smurf Hunter

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #5 on: January 03, 2017, 11:37:17 AM »
Besides radios, what are the pros/cons of using this between a battery and AC inverter? 

This seems like something I could leave on the battery bank and simply attach any 12vdc load appliance.

Offline Carl

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #6 on: January 03, 2017, 03:07:24 PM »
Besides radios, what are the pros/cons of using this between a battery and AC inverter? 

This seems like something I could leave on the battery bank and simply attach any 12vdc load appliance.

I would use the 13.8 volt device for any voltage sensitive equipment ,like radios and run other equipment direct like lights,12 volt fans and such.
An inverter and power supply will allow for a radio to be well powered from a battery as an option that allows for other uses and easy use
of extension cords for utilizing convenient location of equipment and persons.

I would not use the DC power unit between a battery and inverter as inverters often demand too much current for the device to provide.

Offline LodeRunner

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #7 on: November 05, 2017, 06:33:09 PM »
A 100 amp hour battery is RATED at a 20 HOUR discharge  rate
and a few are 10 hour rated for charge or discharge rate as the CHEMISTRY is designed ...
Another "BUG" in the setup is that batteries are not designed to produce more than 50% of their rated
power in AMP HOURS (even when used at the 20 hour ,low current rating)

So a 100 amp hour battery (twice the rated capacity of most auto batteries) is designed for only a 10 Amp rate of discharge!


I've chosen a different way around this problem.  I don't use "12 Volt" batteries for bulk power storage anymore.
Instead I use an "8 Volt" plus a "6 Volt" golf-cart battery in series.  so the quiescent voltages of each battery 'string' are 14 V when dead, and 15.2V when fully charged.   The specific models I use are a SLIGC8V (8V/165AH) and SLIGC125 (6V/235AH).  Because there is a disparity in the AH rating you have to make sure you condition the batteries when you buy them, before pairing them into a "string" and then always keep them as a string for all charging/discharging. 

Golf Cart batteries are designed for sustained high-current loads, so they're much better than typical "marine deep discharge" batteries for powering heavy loads such as HF radios that typically draw 20+ amps when transmitting.

Even under the heaviest load, the voltage of a string never drops below 13.4 volts.  Of course, I had to build a few shunt-regulators (see below) to prevent my radios from seeing too high a voltage, particularly when I'm charging the batteries.  The charging voltage is 16.4~17 volts, which I have two sources of - first is my home solar system, which is 18V maximum under load (the panels are 22V ~ 24V "open-circuit" depending on the sun).  The second is a "15 Volt/40Amp" DC supply that is "adjustable" up to 10% - so at max voltage, it gives 16.5 volts - enough to bulk-charge a string of batteries (but not enough to top them off - for that I use a 5Amp Variable voltage bench supply if I have to).

Each 'string' of batteries is good for 160+ AH, and I have several strings, so I don't ever have to power radios from the same string as inverters and other RF-noisy gear.  Load isolation and noise isolation are good to have!

The down-side is that each string of batteries weighs about a hundred pounds.  But when I take them anywhere -- Field Day, going 'Rover', etc. -- I'm always 'vehicle portable' so it's not a problem for me.

When I go back-pack portable I take one or more of my 12V/7AH Gelcells, but that's a totally different scenario than on-going SHTF operation at a semi-permanent location.

The shunt-regulators are easy to build - the primary components for each are a pair of High wattage resistors: 1 Ohm / 30 watt and a 0.5 Ohm 50 watt, two high-current HEXFETs such as the IRFM360 (23 Amps Continuous Drain Current) -|- IRF540/IRF640 FETs can substitute for low~medium current loads, in which case you can also substitute a 2 Ohm resistor for the 0.5 Ohm -|- a handful of small signal transistors (2N4401, etc) a 12V Zener diode, a few various 1/4 watt resistors and small electrolytic caps, and two 10K potentiometers. 
The power resistors are in series with the positive lead of the load, and each has a FET across it to shunt it out of the circuit as needed.  As the load increases so does the voltage drop, which switches the 2N4401s (set up as difference detectors) on in sequence.  Each 4401 switch on one of the FETs, thus shunting its associated power resistor out of the circuit (the 1 Ohm is taken out first, then the 1/2 Ohm if/as needed).  The electrolytic caps are necessary in each of the voltage-sensing loops, because otherwise the differential voltage sensors may (will) try to oscillate at some values of load current.  Heat-sinking of the power resistors and FETs is required for the medium and high current versions.

For low-current loads, you have a choice - use two 1 ohm/5 watt resistors and build as the above, which is fine for HTs and other general-purpose comms gear, or;

Use a single 2 Ohm/10 watt resistor and IRF640 FET, with one differential voltage sensor run in linear mode.  In this instance you're running the FET in linear mode instead of switch-mode, to give better (finer) voltage regulation at the cost of some power efficiency.  This is a good solution for high-performance receivers, which should have an isolated power circuit of their own anyway.  The IRF640 requires a small heat sink in this configuration (it will dissipate between 3 and 10 watts).

~~~Go Build Something~~~

Cheers


Offline Carl

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #8 on: November 06, 2017, 04:56:39 AM »
  Sounds easy...

Offline Smurf Hunter

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #9 on: November 06, 2017, 09:15:39 AM »
  Sounds easy...

Emergency stuff should be simple and lend itself well to field service.
Can you do this:
wet, cold, in the dark, stressed, tired?


Offline Carl

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #10 on: November 06, 2017, 09:25:33 AM »
Emergency stuff should be simple and lend itself well to field service.
Can you do this:
wet, cold, in the dark, stressed, tired?

I have.....

Offline LodeRunner

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Re: Ham gear does not run well from 12 volt batteries...Here is a fix
« Reply #11 on: November 06, 2017, 04:16:29 PM »
Emergency stuff should be simple and lend itself well to field service.
Can you do this:
wet, cold, in the dark, stressed, tired?

EXACTLY.  That's why we all need to plan, prepare, and practice now, while things are normal... to be ready for the time when things will be abnormal, and we'll all be running on a triple dose of "idiot".  The "Prepare" portion of this requires us to work out all the kinks in our desired 'systems' and idiot-proof both equipment and process(es) for ourselves. 

Cheers