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Author Topic: Maintaining full output power on batteries  (Read 189 times)

AD0AR

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Maintaining full output power on batteries
« on: April 23, 2020, 11:01:03 AM »

So for about 4 years I've been using (6) 12v AGM batteries as a backup power supply.  I initially had them on a AC 35 amp automatic charger but recently transitioned to solar power for charging them. 
  Now that I've been using the renewable energy for normal operations, I noticed that I'm not getting the full output out of my IC-7600 on ssb.  The output meter on the radio doesn't ever go to the end, even in FM mode into a dummy load.
  Using an AC power supply measured at 13.5v it does achieve full output so nothing wrong with the radio.
  I have a mobile HF setup that I took out of the car for the winter and I use a boost regulator system for the radio and HF amp.  It works splendid in the car so I figured why not try it on the solar charged batteries? 
  Other than the hassle of making some 6 gauge jumper wires to connect to the lug nuts on the boost regulator to get it integrated into the power circuit, all is well and the radio is back to it's 100 watt output.  Plus I can always add my 12v HF amp to the circuit as well and get full power out of that as well as the radio at the same time. 
 Obviously this boost regulator is much larger than the ones being marketed to the amateur radio crowd- this one sports a 10 mosfet circuit so it can handle much higher continuous output, much more robust and more efficient.   
Harrison Labs makes this unit under the product name Fluxcap. 
https://www.hlabs.com/products/fluxpower/index_files/MobileApplicationofFluxCap.htm
They have them available in 3 sizes- a 50 amp, 100 amp, and 200 amp design. 
The 100 amp unit is the one that I am using to run a IC-7600 and a SGC SG-500 at the same time. 
  I've also noted that it also increased my run time on batteries too.  Before I really could not let the batteries drop below 11.8v or I'd see a large reduction in power output- the IC-7600 will continue to run as low as 10.5v but much decreased output. 
 Now I can discharge the batteries deeper if needed (like an emergency) and know that even if my batteries are at 11v this unit will still put out 14.7vdc and prevent me from causing splatter on the bands and may be the difference that lets me get that radio contacted I needed.
  I haven't put it to the test to see how much longer I can run using the boost regulator yet.  I'm waiting for a long power outage to really put it to the test.

  It does draw more current to boost the voltage while delivering the rated current into the load so you aren't getting something from nothing. 
  For instance my radio can consume up to 20 amps @14vdc.  Using the boost regulator to boost from 11vdc to 14.7vdc, it can draw in excess of 27 amps from the 11v battery to compensate for the low voltage condition. 
  The lower the battery voltage, the lesser efficient the unit can become converting to the higher voltage. 
  Speaking of efficiency, I conducted a power test of my sgc amp into a dummy load with this boost regulator to see if it gets real hot. 
I was impressed!  After running a 10 minute test 10 seconds on/ 10 seconds off @ 450W PSK modulation the heatsink of the boost regulator was under 110 degrees Fahrenheit while running off my AGM batteries @ 12.3vdc or less. 
The amp was much hotter!
If you want to be able to run much longer on battery at full power or are just having the low power blues like me, maybe this is a solution that will work for your station as it worked well for mine  ;)


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K1VSK

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Re: Maintaining full output power on batteries
« Reply #1 on: April 23, 2020, 12:03:30 PM »

There is an old saying which goes something like this - batteries don’t die; they are killed.

If you draw down these batteries below 20% SOC, you affect their number of cycles (duty cycles) regardless of what you connect them with/to. Always monitor battery voltage.
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W9IQ

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Re: Maintaining full output power on batteries
« Reply #2 on: April 23, 2020, 12:53:39 PM »

If you draw down these batteries below 20% SOC, you affect their number of cycles (duty cycles) regardless of what you connect them with/to.

I don't think you said this correctly. You can never draw them down to 20% below SoC. SoC is an initialism for state of charge which indicates its remaining capacity compared to its fully charged capacity. This makes SoC a moving target as current is drawn from the battery. Perhaps you meant DoD - depth of discharge in which case 80% DoD is typically the maximum level of recommend discharge for an AGM battery.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

K1VSK

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Re: Maintaining full output power on batteries
« Reply #3 on: April 23, 2020, 01:50:47 PM »

If you draw down these batteries below 20% SOC, you affect their number of cycles (duty cycles) regardless of what you connect them with/to.

I don't think you said this correctly. You can never draw them down to 20% below SoC. SoC is an initialism for state of charge which indicates its remaining capacity compared to its fully charged capacity. This makes SoC a moving target as current is drawn from the battery. Perhaps you meant DoD - depth of discharge in which case 80% DoD is typically the maximum level of recommend discharge for an AGM battery.

- Glenn W9IQ
its common to refer to SOC as a function of capacity when fully charged and is the accepted standard among all battery monitors (as the DOD is always a moving target) but my point is clear to not deplete the battery by using a voltage booster or anything else below the threshold level regardless of what you call it. 
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W9IQ

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Re: Maintaining full output power on batteries
« Reply #4 on: April 23, 2020, 03:33:25 PM »

Not at all. SoC is an indication of the relative percent of discharge. A 20% SoC means that the battery has been drawn down to 20% of its full charge. So you are chasing your tail when you say don't exceed 20% of or below SoC.

- Glenn W9IQ
« Last Edit: April 23, 2020, 03:42:56 PM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

AD0AR

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Re: Maintaining full output power on batteries
« Reply #5 on: April 23, 2020, 04:56:00 PM »

In an emergency anything goes, so that's why I haven't fully tested the run time as I know that running these deep cycle AGM batteries to more than 50% DoD will shorten their life. 
The coulomb counter I use for monitoring battery capacity can give an accurate time to whatever discharge level I specify and I have specified 10.9vdc as a minimum to discharge to even though I know I could set it to a 10.5vdc level, I do not wish to degrade my battery bank aimlessly by deep discharging them. 
  We've always used DoD as a metric for AGM sealed lead acid.  For flooded cells in the Navy, we'd use specific gravity and used the SoC metric for that. 
I guess it's whatever you got schooled into you on the job. 


   
 
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W9IQ

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Re: Maintaining full output power on batteries
« Reply #6 on: April 23, 2020, 05:21:18 PM »

It is a question of correct usage of the terminology. What does 20% below SoC mean? If the SoC is currently 40%, 20% below SoC means 32% SoC. But as soon as your reach 32% SoC, 20% below SoC means ~26% SoC. See the problem?

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

AD0AR

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Re: Maintaining full output power on batteries
« Reply #7 on: April 23, 2020, 06:09:35 PM »

I agree it is relative.
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