So this is something that I should probably know but don't.

I've got a significant amount of 12 volt battery backup power for my shack.  I occasionally run everything (radio, computer, peripherals, etc.) off of battery power just because I can.

I've noticed with the IC-7300 (probably because the features of the radio make it easier) that I'm not getting near as much power out on phone or digital with the settings I run when operating off of the power supply at 13.8V.  Now I can crank up the "drive" on, say, Winlink and get more power, but I am concerned that I may be getting some distortion due to lower voltages.  On SSB with my settings that I normally get ~100W peak, I get around 50W Peak.  Again, I can crank up the mic gain, but I'm not sure that is the optimal solution.

What do you guys do to get peak power (close to 100W peak SSB) running on batteries?

I've got plenty (well over 1 killowat hour) of high performance batteries in parallel using 3/0 copper cables, so low voltage and battery sagging is definitely not the issue.  Talking 12.8V with a fresh topped off battery bank here.  Now I'm running about 5 ft of 10 AWG stranded to the power supply, then through the provided (way too long) radio power cables, so the voltage drop there may be in play.  I've ordered the parts to make a much shorter radio power cable, as I'm weird and don't want to modify the stock ones, like I'll ever sell a radio .

Whatcha got for me, Arfcom?

MFJ-4416B.

Yeah. It's MFJ. sigh.

Designed to solve this exact problem.

ETA: I guess it's now up to rev C: http://www.mfjenterprises.com/Product.php?productid=MFJ-4416C

Thanks for the input.  Have you ever run one or have any opinion on the product?  The efficiency looks better than an inverter.

$180 is pretty steep, though, and I hope it is RF quiet.  I was hoping someone would save me some $ and just say "turn up the turbo encabulator" or something.

If this works and is the best option, I'll likely buy one.

I have one in the shack specifically for when I run on backup power.

I'd noticed the same issue as you when I did a battery power net. Obviously I don't run
the KPA500 on battery, but I saw a big enough hit on the TX power I wanted to fix it.

The 4416 works as advertised. It has a couple modes, one is on all the time and the
other is TX switched (so it only boosts on transmit.) I've never tried the TX switching,
which requires the coax to pass through the unit.

Since I have a 7300, I just did a quick test:

100 AH SLA battery attached to my SEC-1223BBM power supply via about 6' of
10AWG, and then the output from that into the 4416, and from there to my DC
power strip. I have some wierd RF issues in the shack so I can't test digital at
any significant power, and didn't want to dig in the junk box for a key, so
hopefully AM carrier testing is OK:

Icom 7300, AM carrier power at 50% RF output
Battery only: 5W
SEC-1223BBM: 15W
4416 on battery or via SEC-1223BBM: 20W

Because of the boost function allows much higher current draw from the
battery, if the battery has any significant internal resistance full power will
make it drop out pretty hard. I didn't have any issues with a brand new SLA
but mine's like 4 years old now, sitting on the SEC-1223 most of the time,
and it was not happy about this test at all. Looks like it's time to replace it.

If you have any issues with your batteries, they will show up running this
thing. You're looking at 20A or so at full power.

Note you can adjust the 4416 to take the output up to the very top of the
rated voltage of the rig, meaning that indeed you'll get more power out
than a standard power supply if you want it and are willing to push things.

As it stands, it will abolutely deliver the exact same performance as an
AC power supply will while on battery power.

No noticable RX noise from using it (which is actually fairly impressive.)

Thank you very much for the detailed review.  It seems like this is what I need to do what I want to do.

Questions:

1. Do you have this at the radio end or the battery end of your power wiring?
2. Have you noticed any increased RF noise from this unit when on? (edit: saw you answered this)

The "auto switching" isn't a big deal, I figure if I need to use it I can put it in mode manually.  I also have inverters that could solve the power problem, but they have some RF hash that I don't want.

Battery internal resistance isn't an issue, I'm running 5 of these wired with 3/0, so it shouldn't be a problem.

Thanks again for the recommendation.

1 ) definitely put it on the radio end. The whole point of the thing is to pick up the voltage
due to sag, and if you put it at the battery end, you're not really helping it much.

2) On the noise, I can run the radio on normal power and then plug in the battery to the
4416 and I see/heard absolutely no change. There may be birdies somewhere but
not where I'm at on the band. My shack isn't completely RF-quiet, so I'm sure if I
was in a DC environment out in the boonies with no other RF sources it might be
noticable.

If you're talking about that wideband hash you get from fake sine wave inverters,
crap LED lamps, plasma TVs, etc, no, there's nothing at all like that with this unit.

As I said, I don't use the auto switching, I just leave it in the "always on" mode.
Higher power draw on RX but that's minor compared to everything else.

Sounds like your battery bank is fine and you're just dealing with the nominal
battery voltage being below 13.8V enough to matter.

It's not a cheap device, but like I said, it does work as advertised. I was as surprised
as anyone given it's MFJ. AFAIK no one else makes anything like this, really.

Now, whether it's worth $200 to get 20-40W more watts out of the radio is going
to depend on the user.

Awesome, thank you again.

As for the last statement, you Arfham turds are responsible for getting me into ham radio for "Only $30!!!".  Yes, I fell victim to the original Bao-thing thread.  Now, several thousand dollars later, what's a couple hundred bucks between friends?

That seems super wierd. How long is your wire total? Does you radio have a built in voltmeter you can check? Alternately check it with a VM at the radio end while TX. Also have tried using the radio power cable directly to the battery? Another thing to consider is that 12.8V isnt 13.8V many radios dont care, maybe the icom does.

Also you shouldnt be running 100w for winlink. Probably 50w avg power. Crest factor on winlink isnt great.

Both my IC-7200 and IC-7300 have the same issue as far as TX power and input voltage.

I suspect it's common for anything but QRP rigs, and probably has more to do with battery
voltage than the cabling.

None of my Yaesu rigs have this issue, maybe its an icom "feature"... Come to think of my 706 might do this too..

I haven't noticed it on my FT-857, but the power meter is tiny and I only use it portable  (rarely digital) anyways, generally turning down the max power to start with as I'm using smaller batteries.

I know for sure the IC-7200 and IC-7300 do it.

Need to check the Kenwood TM-V71a and see if it has any issues with decreased power or distortion on the "High" power setting.

Yeah the yaesu 817/57/87 seem to work fine with more variable power off batteries. My 897 puts out full power no problem at 12 or even 11.x volts on tx. The 817 works fine to 9v.

Realistically I dont think the icom rigs were meant to be used in the field like the older yaesus were.

To be fair the 897 was designed to run off batteries and probably expected a lot
of drop during operation.

I think you're right in the sense that I doubt Icoms had the same design goals in
mind outside of something like the 703.

Drok 150watt buck/boost voltage regulator
$51 at Amazon

https://www.amazon.com/DROK-Adjustable-Regulator-Stabilizer-Transformer/dp/B00C9UAE28/ref=mp_s_a_1_26?ie=UTF8&qid=1536033887&sr=8-26&pi=AC_SX236_SY340_QL65&keywords=drok+boost+converter

I have run my IC-7300 and my FT-891 off a 75 Ahr  SLA battery and the only time I have seen this issue has been because the power connectors had a crappy connection.

The first thing I would do is check the IC-7300 connection to power and all power cable connections. If you are using slide banana plugs that could very well be the issue. I have had problems with those.

If you are, instead of sliding them tegether, put them in perpendicular in the hole and tighten them down.

If you are using some other type of connector, inspect them and make sure they are making a solidly tight contact.

The amount of wire you describe should not have any voltage sage at all.

You said this:

What power supply? Why are you not running the radio directly from the batteries?

I run the IC-7300 using the factory power cables and with a good connection, is not an issue and get full power.

I really doubt it is a wire run issue. I think it is either a 'power supply' ( please tell us what you are using here ) or a connector issue to include a not so tight fuse holder.

ICOM says

Power supply requirement 13.8V DC ±15%
Power Consumption

Tx: 21A (at 100W output power)

Rx: 0.9A typical (Standby), 1.25A (Maximum audio)

That is 11.73 - 15.87  VDC

Here is a voltage drop calculator.

voltage drop calculator

At starting voltage of 12.8 DC ( full battery )and 21 amp draw, it says through 15 feet of 10 AWG ( your stated 5 feet plus the OEM power cable 9.8 feet of 10 gauge wire)

the end voltage is 12.17 VDC.

While this is close to the bottom of the min operating voltage, any kind of drop due to a not so great connection could put it below 11.73. I would check for tight connections at all connections including the OEM fuse holder holding the fuses on the OEM cable and any other inline fuse holder.

Good question, Mach.

The power supply is a Samlex SEC 1223 BBM. Just turning off the power supply and leaving the battery hooked up to the integrated charger.

I didn't think to try it wired directly to the battery. I'll have to try that when I get home to see if that makes any difference.

Connections are all properly crimped power poles, but I'll check again for tightness, especially at the power supply.

I always crimp, solder and glue my PPs... Ask me why

Yeah, if the PS is inline that may be a problem.

I also crimp & solder most of the time, but I didn't want to kick that hornets nest

That power supply is maxed out at 23 amps. It also has short circuit, over load, and thermal protection circuits that will limit voltage and current. It might be getting warm and restricting less than the max rated current.

The IC-7300 needs 21 amps.

That might be the bottle neck.

But I am not familiar with that supply. It appears to be not just a supply but when connected to a battery, is a UPS. It might be limiting your current to less than 21 amps which is what the IC-7300 draws on transmit at full power.

My first step would be radio direct to battery and see if that fixes the problem

If it does, you can go from there.

Another way to do this would be power supply to solar charge controller to battery.

Then hook up the radio directly to the battery.

When there is power, the battery is charging even when you are using the radio and when there is no power you are using the battery.

Not sure what that UPS is giving you since you are powering a DC radio.

It won't. (Same PS here.)

I really think it comes down to 12.8V =/= 13.8V, and the fact that the Samlex will regulate under load to keep it
at 13.8V and the battery is going to drop under load to something lower.

If the power supply is max 23 amps.

The radio max current draw is 21 amps at 13.8 volts.  So 290 watts.

The radio wattage remains constant, correct?

As soon as voltage drops below 12.6 volts, max current (23 amps) on the PSU is exceeded.

The radio can handle the lesser voltage but the PSU cannot.  So the PSU is cranking out as much as possible, but voltage is sagging so the radio puts out less watts.

right / wrong?

I just noticed this.

turning off power supply and leaving battery hooked up.

is this how it is supposed to be run? I dont know anything about this particular UPS but I would think it would have to be on to work properly. try keeping it on and unplug it from AC ( simulating power failure which is what it is made for ) so it can do its thing. Turning it off might be limiting current through it depending on the circuits.

What Mach said... Again, I'm not sure how your UPS is supposed to work, but I would just try it direct on battery power, even a 20 dollar 7ah SLA should work if you don't want to dick with the wiring on the UPS, and will tell you if you can get full TX power out of a SLA at lower voltages.

Okay, you guys were right.

I disconnected the radio from the power supply and hooked it directly to the battery and am getting nearly 100% power output as compared to on the supply.  Running digital modes on the same settings to keep things "apples to apples".  This also increased my SSB peaks as well.

Just an extra note, unplugging the supply and leaving the radio and battery connected to their respective terminals did not make any difference than before.  I tightened the screw connections on the terminals and no difference.  I may have to make up a new set of wires/powerpoles for the battery terminal on the power supply and see if that makes any difference.

Thanks as always for your help!