Looking at a Grid Doctor 300 to run some radios when the power is out , up on a mountain just testing or field day etc. This "generator" has a 320 wh battery . how long will it run a 10 watt radio' assume 25 percent of the time transmitting and the 75 percent receiving so 15 mins transmitting and 45 receving out of 1 hr. I would think it could run it a few hours ? 3 or 4?? tks
Solar Generator
- Thread starter MackinNC
- Start date
How much current does the radio draw when transmitting at 10 watts output?
My guess is around 10-13 hours figuring a two Ah draw. Much depends on the power draw during TX and RX. With a 100W solar panel connected, you’re going to have energy to spare and will re-charge the battery while you have sunlight. Figure 4 Ah from the solar panel in angled and plenty of sunlight. That gives you two Ah to power and two Ah towards charging. With five hours of direct sunlight you’ll push 10 Ah back into the battery the next day. Also, you noted “radios”, so there’s more amps being drawn.
One of my smaller solar generator systems is:
- Ecoflow River 2 Max 512 Wh LiFePO4 battery ($400)
- 100W flexible solar panel ($80) a bit more if you need folding
- Cable to connect solar to battery ($25)
The River 2 Max comes with a 12v DC power cord, so you can charge it while driving to top it up as well. I recommend a LiFePO4 (LFP) battery over a Lithium Ion in whatever solar generator you buy.
One of my smaller solar generator systems is:
- Ecoflow River 2 Max 512 Wh LiFePO4 battery ($400)
- 100W flexible solar panel ($80) a bit more if you need folding
- Cable to connect solar to battery ($25)
The River 2 Max comes with a 12v DC power cord, so you can charge it while driving to top it up as well. I recommend a LiFePO4 (LFP) battery over a Lithium Ion in whatever solar generator you buy.
Thanks, a little more hours than I thought but good to know. I fiqured it as drawing 2- 2.5 watts but didnt want to say as to see what others thought.
I would only run 1 radio at a time.
so now I wonder if I get 10 hrs out of a 10 watt radio then a 50 watt will cut run time to just a couple hours??
You have answered your question. The battery has a capacity of 320 watt-hours. How many watts does the radio consume when it is keyed up? If a radio operates at 50% efficiency, it will consume 20 watts of power when transmitting at 10 watts.
The calculation is straightforward: 320 Wh divided by 20 watts = 16 hours of transmitting. This means you can key the mic for 16 hours. With a 25% duty cycle of 15 minutes of transmission (TX) and 45 minutes of reception (RX), the operation time would be less than 60 hours, or around 2 days.
To get more accurate, measure the power the radio uses during receiving. For example, if it uses 4 watts and runs 45 minutes = 4 watts x .75 hours = 3 wh hours. 20 watts for 15 minutes = 20w x .25h = 5wh. You would consume 8 wh per hour. 320 wh / 8wh/h = 40 hours.
Remember that:
Watt Hours = Watts x Hours
Amp Hours = Amp x Hours.
Now go getter done.
The calculation is straightforward: 320 Wh divided by 20 watts = 16 hours of transmitting. This means you can key the mic for 16 hours. With a 25% duty cycle of 15 minutes of transmission (TX) and 45 minutes of reception (RX), the operation time would be less than 60 hours, or around 2 days.
To get more accurate, measure the power the radio uses during receiving. For example, if it uses 4 watts and runs 45 minutes = 4 watts x .75 hours = 3 wh hours. 20 watts for 15 minutes = 20w x .25h = 5wh. You would consume 8 wh per hour. 320 wh / 8wh/h = 40 hours.
Remember that:
Watt Hours = Watts x Hours
Amp Hours = Amp x Hours.
Now go getter done.
Last edited:
JDKelley
Just call me "Sparks." Or "Lucky."
"Watt-hours" is exactly that - figure it to be the number of watts the battery will deliver for one hour. So, 320W-h means 320W for one hour.
Now, you can play with that - any combination that multiplies out to 320 will work. So, 80W x 4 hours, for instance. Or 20W for 16 hours.
Bear in mind that listed power on a radio is transmit power, not power draw. This means that your 10W radio will put out a 10W PEP signal, but it will consume slightly more 'leccy generating it and pushing it out - I'd not be surprised if your consumption figure weren't closer to 13-14W. So, figure 16W (to make the maths come out even,) for 20 hours. 16W x 20h = 320 W-h. YMMV, TANSTAAFL. Bear in mind that there are inversion and conversion losses, for instance, so you're not going to get the full 320 W-h. But, since you're not drawing the full 16W you're using to figure your battery longevity, that's essentially a non-issue, you can probably still count on 20h runtime. Longer, with the solar panel - unless it gives you a good 20-30W charge current, it will at least slow down the draw loss by partially replacing what you're taking (keeping the maths simple, say you've got a 10W panel. You're drawing 16W from your radio. 16 W - 10 W = 6 W, so that's what you're drawing from the battery. Or, since batteries themselves are rated in Ampere-hours, let us apply Watt's law, and 6 W / 12 VDC = 0.5 ADC. If you can somehow make up that half-Ampere of charge, you can keep your battery static. Perhaps a wind turbine? A water wheel, if you've got a stream handy? Be creative!)
Ohm's Law: E = I x R. E = Volts [V] (Electromotive force.) I = current [A] (I don't know why.) R = Resistance [ohms]. "AC" or "DC" is usually specified, as in "VAC" or "ADC." Resistance doesn't care.
Watt's Law: P = E x I. P = Power [W] (Watts. Doesn't care what sort of current.) E = Volts [V] (Electromotive Force.) I = Current [A] (Again, I don't know why they use "I" for this.)
These two are often combined as: P = [I x R] x I, or P = I^2 x R. Engineers use this combined form a lot when figuring transmission lines (when they're figuring "I-squared-R" losses.)
If you're going to get into any sort of electronics, or bone for your ham ticket, tattoo those two formulae on the inside of your eyelids. As they told us in training: "Gentlemen, you will see this material again." (This was your cue to write. It. Down. If I say that, find a notebook.)
Now, you can play with that - any combination that multiplies out to 320 will work. So, 80W x 4 hours, for instance. Or 20W for 16 hours.
Bear in mind that listed power on a radio is transmit power, not power draw. This means that your 10W radio will put out a 10W PEP signal, but it will consume slightly more 'leccy generating it and pushing it out - I'd not be surprised if your consumption figure weren't closer to 13-14W. So, figure 16W (to make the maths come out even,) for 20 hours. 16W x 20h = 320 W-h. YMMV, TANSTAAFL. Bear in mind that there are inversion and conversion losses, for instance, so you're not going to get the full 320 W-h. But, since you're not drawing the full 16W you're using to figure your battery longevity, that's essentially a non-issue, you can probably still count on 20h runtime. Longer, with the solar panel - unless it gives you a good 20-30W charge current, it will at least slow down the draw loss by partially replacing what you're taking (keeping the maths simple, say you've got a 10W panel. You're drawing 16W from your radio. 16 W - 10 W = 6 W, so that's what you're drawing from the battery. Or, since batteries themselves are rated in Ampere-hours, let us apply Watt's law, and 6 W / 12 VDC = 0.5 ADC. If you can somehow make up that half-Ampere of charge, you can keep your battery static. Perhaps a wind turbine? A water wheel, if you've got a stream handy? Be creative!)
Ohm's Law: E = I x R. E = Volts [V] (Electromotive force.) I = current [A] (I don't know why.) R = Resistance [ohms]. "AC" or "DC" is usually specified, as in "VAC" or "ADC." Resistance doesn't care.
Watt's Law: P = E x I. P = Power [W] (Watts. Doesn't care what sort of current.) E = Volts [V] (Electromotive Force.) I = Current [A] (Again, I don't know why they use "I" for this.)
These two are often combined as: P = [I x R] x I, or P = I^2 x R. Engineers use this combined form a lot when figuring transmission lines (when they're figuring "I-squared-R" losses.)
If you're going to get into any sort of electronics, or bone for your ham ticket, tattoo those two formulae on the inside of your eyelids. As they told us in training: "Gentlemen, you will see this material again." (This was your cue to write. It. Down. If I say that, find a notebook.)
As AK9R initially questioned, what is the current draw at 10W? Knowing how much your radio draws during TX as well as during RX will provide more accurate numbers. I have a Yaesu 991A that is a power hog, compared to purpose built QRP radios. While it will draw no more than 8 amps at 5W using FM mode, it draws 1.25A while just receiving. She's a thirsty one. Contrasting to that, a Yaesu 817ND draws no more than 1.5A during 5W transmit on FM and no more than 0.35A during RX. That is a big difference between the two radios.
What radio model are you using? Perhaps we can figure out the current draw knowing that if you don't have something to measure it.
What radio model are you using? Perhaps we can figure out the current draw knowing that if you don't have something to measure it.
10 watt output radio pulled 3 watts on receive and 25 watts on transmit.....unit showed 13 hrs it could go for on tx.
50 watt output radio drew 2 watts on receive and 50 plus on tx and showed 6 hrs plus on tx
so this unit will do exactly what I need. rec hours on the units were for 2 and 3 days.
Of cours lower watt radios especially on receive should pull less.
50 watt output radio drew 2 watts on receive and 50 plus on tx and showed 6 hrs plus on tx
so this unit will do exactly what I need. rec hours on the units were for 2 and 3 days.
Of cours lower watt radios especially on receive should pull less.
JDKelley
Just call me "Sparks." Or "Lucky."
8A @ 5W? Do they not build these for efficiency? That's hefty at anything 1 volt or higher!
Assuming 12VDC, that's 8A x 12VDC = 96W just to send out a 5W signal? Wow...
EDIT - Afterthought: I thought civilian radios were made better than that...
For Field Day last June we ran five stations in Class AB (battery). Each of our batteries had a solar panel for charging. But first we wanted to know exactly what each of our radio's power consumption was, both in receive and in any given transmit output power. We put PowerPole connectors on the flying leads of these and placed them inline in the 12VDC supply with each radio to determine power consumption. Worked very well, and we came out as the #2 ranked Category AB site in North America -
https://www.amazon.com/HTRC-Precision-Analyzer-Battery-Voltage/dp/B06XPVKY13/ref=sr_1_2_sspa?crid=27Y4DA773GPM6&dib=eyJ2IjoiMSJ9.VLhqNngJBZg16suj5uFSqBNjFb-PgfZ0urJyxai9xrqFmhNT9AwtwPjlyqqHQcSFN_nuT6muYuvn5tw3t0NzqjLxe5tMz0rTRvps490qu5ujvWYOG8KKaLESjN7qaCjQ-Jwnd9OPaY98SDUf5daV4GF48y2fAugxTJuV_ayS_SeovU2sRstDqZblydyTYpGI8zX-uAGDeiKVU1D1711GJutsYrmEw8n8hNHbxx3uurkZrkaKUK6rn7jSmU6G6vc1x-fB2aXgnrog8xAiaODEbVdTtPhz42li2RSrVQ-HjOw.WF59YRqQxs40tGffMgkn1vJAsPv2jUl8tiGcH2ibmH8&dib_tag=se&keywords=inline+dc+power+meter&qid=1732880714&sprefix=inline+dc+power,aps,343&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1
https://www.amazon.com/HTRC-Precision-Analyzer-Battery-Voltage/dp/B06XPVKY13/ref=sr_1_2_sspa?crid=27Y4DA773GPM6&dib=eyJ2IjoiMSJ9.VLhqNngJBZg16suj5uFSqBNjFb-PgfZ0urJyxai9xrqFmhNT9AwtwPjlyqqHQcSFN_nuT6muYuvn5tw3t0NzqjLxe5tMz0rTRvps490qu5ujvWYOG8KKaLESjN7qaCjQ-Jwnd9OPaY98SDUf5daV4GF48y2fAugxTJuV_ayS_SeovU2sRstDqZblydyTYpGI8zX-uAGDeiKVU1D1711GJutsYrmEw8n8hNHbxx3uurkZrkaKUK6rn7jSmU6G6vc1x-fB2aXgnrog8xAiaODEbVdTtPhz42li2RSrVQ-HjOw.WF59YRqQxs40tGffMgkn1vJAsPv2jUl8tiGcH2ibmH8&dib_tag=se&keywords=inline+dc+power+meter&qid=1732880714&sprefix=inline+dc+power,aps,343&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1
John_S
Member
A lot depends on what mode you operate. Carrier based modes will draw much more...SSB is more gentle on this. Building a back up system that works well is all about finding enough capacity to operate enough without drawing it down too much and having to wait for recharging. I've been running a Xiegu G90 20 watt radio along with a solar/lifepo battery system for the last 9 months or so. The panel is rated at 50 watts and I use 2 30 amp batteries. This seems to run fine. The only issue I had was noise from the first charge controller I used. For anyone going this route, I can easily recommend Genasun controllers. No noise whatsoever.
John_S
Member
You can generally assume about 40 to 50% efficiency. Much of any variation from this figure depends on how many other circuits are used in the radio such as processors and displays. The 817/818 series radios are minimal for these compared to the bigger radios.
JDKelley
Just call me "Sparks." Or "Lucky."
I'm familiar with design of power backup systems (I've done a couple generator systems, a couple PV/battery systems, and I'm in the middle of a - paid - ambulance decommission and refit into a travel rig,) I was just surprised that there was that much "overhead" in power consumption! I know military radios positively suck on consumption/transmit ratio, I just thought civilian radios were designed better than that, that's all.
John_S
Member
I think most designers take current draw/demand for granted to an extent. They stick the user with the capability to power the equipment no matter what. As people do more portable ops...SOTA, POTA, etc...more ham gear becomes sensitive to lower current draw. The G90 is a good example...only needs 6 amps max for 20 watt carrier modes...700 ma for Rx. Bigger radios are using a lot of processor circuitry and they need the extra juice.
The Yaesu 991A is not a purpose built low power draw radio. It has features that draw much more power than the Yaesu 897D that I previously owned. Both are all band all mode radios that can do 100 watts. The 897D used 1Ah less on receive, if I recall correctly. People must research and not expect anything. I have battery and solar solutions to easily handle the 991A. I also typically have sunshine 300 days a year.
Project Farm recently did a video on this and his conclusion was that the Jackery was the best overall of the models he tested.
One thing I REALLY dislike about these "solar generators" is that you can't get "raw" 12V out in the form of a PowerPole or something. Most only give a cigarette lighter output at best. I love the formfactor of these, but the lack of a decent power output for 12V is a non-starter for me.
One thing I REALLY dislike about these "solar generators" is that you can't get "raw" 12V out in the form of a PowerPole or something. Most only give a cigarette lighter output at best. I love the formfactor of these, but the lack of a decent power output for 12V is a non-starter for me.
Be careful with the Jackery. I have the Explorer 1000 which I use mostly for truck camping/off-roading. I have used it occasionally for portable ham radio usage and hope to do more so once the season closes. It is noisy, (QRM-wise) especially if you are using it to power the AC outlet. This was with a IC-705 and a variety of SDR's. I went back to the battery I use for the ham but would consider the JE-1000 as a rough Plan B. Getting a longer cord and then placing it beneath my truck helped and when I get the chance I'll snap some ferrites on it and see what that does. It does most of what I want for camping and with solar panels I have gone a week easily off of the grid. Also, X2 on what Exkalibur said regarding having only a 12V cigarette lighter port.
One would think that with all the ham radio social media influencers giving these "solar generators" positive reviews, that one of the manufacturers would put a high-current 12 VDC output on them. Maybe that's what concerns the manufacturers. They may not want someone drawing 20-30 amps from their products.
Drawing 20 Ah at 12v using a 100Ah LFP battery is just at a MFG’s recommended 0.2C charge/discharge rate for thousands of cycles. I recommended that change to Ecoflow as an improvement on their next version for battery boxes that size. Until then I have battery boxes I built that allow for that power draw via a powerpole strip using LFP batteries. Well, on 100Ah or more battery boxes. (1280Wh)
I can run four 100W solar panels 2S2P into an MPPT controller in order to charge that battery box back to full as quick as I can while keeping the longevity using the 0.2C rate.
I can run four 100W solar panels 2S2P into an MPPT controller in order to charge that battery box back to full as quick as I can while keeping the longevity using the 0.2C rate.
JDKelley
Just call me "Sparks." Or "Lucky."
Bloody near building PCs into radios.
Anyone know of any decent "low-overhead" units, offhand?
