Ham Radio with backup power

[visseroth]

I have a project I'm working on where I'm setting up a ham radio node.
I'd like this node to be tied to a 12v battery being charged by a AC smart charger and the 240W worth of solar panels that I have. This is pretty simple to setup as I just need to tie the smart charger and the solar charge controller into the battery and they will charge as needed and the node will draw off the 12v battery.
The problem I'm running into is I'd like any extra power that is not needed by the node or battery to be sent to a grid tie inverter to feed back into the house. Granted I would doubtfully see much reduction on my power bill with ~240W (peak) being fed back into the house, but the idea is to gradually grow the system, more panels, some more batteries for emergency power but primarily grid tie.

Would anyone be able to help point me in the right direction to achieve such an objective on a budget?

[bcroe]

You need a permit, and construction final approval to feed power back to the grid. That system is too small to be considered, and
grid tie systems don't lend themselves to easy growth. You might look around for an appliance that might be directly 12V powered
by your surplus. The economical backup is a generator. Bruce Roe K9MQG

[PNPmacnab]

Really bad economics to grid tie. If you have an electric water heater, why not send the power there. Normal heat loss is about 150W which is what you have. No chance of overheating but you do need to operate at power point.

[PNjunction]

I'd like this node to be tied to a 12v battery being charged by a AC smart charger and the 240W worth of solar panels that I have. This is pretty simple to setup as I just need to tie the smart charger and the solar charge controller into the battery and they will charge as needed and the node will draw off the 12v battery.

Be careful with the smart charger. In fact, a regulated 13.8v power supply would be the best idea if this is going 24/7. Reason being is that if your load pulls an appreciable amount of power during the dark, the "smart charger" will never finish the absorb stage (CV stage), and hold the batteries in the absorb mode all the time. In other words, overcharge. Use the 13.8v supply if you are going to be in a constant float-charge scenario during the dark.

If you are just going to do a top-off or maintenance charge say during the weekends or long periods of no sun to keep the battery maintained, that's a different story.

Granted I would doubtfully see much reduction on my power bill with ~240W (peak) being fed back into the house, but the idea is to gradually grow the system, more panels, some more batteries for emergency power but primarily grid tie.

No significant reduction in your power bill. What little it might save is totally overriden by the fact that operating from batteries is about 10 TIMES more expensive overall than running from the poco. Not to mention the problems that can arise from an illegal grid-tie setup, usually with cheap junk at this stage. Both the poco, and um, insurance agencies are not in the dark when it comes to these diy hacks.

Growing from a 12v standpoint is cost-innefective. Basically you'll be replacing ALL of it with higher voltage systems when you get serious, but now that the budget is blown on 12v toys, the interest in solar goes bye bye.

Would anyone be able to help point me in the right direction to achieve such an objective on a budget?

As an amateur, make full use of your multimeters, ammeters, perhaps a P3 Kill-A-Watt meter to measure your power draw over time. Look at the solar-insolation charts to make sure you can recharge in proper amount of time with usually no more than 50% DOD. Less is preferred. Take into account your days of autonomy to help you size the battery, and the solar array *in the winter* hours.

This is a whole lot more fun than just buying things from off the shelf and seeing if it "sticks".

[visseroth]

Sorry it's taken so long to get back. I've been busy and mulling over what everyone has said and if I'm understanding things correctly it may be best to just put the node on a 12v power supply that's connected to a AC battery backup and forget about the solar panels OR strictly put the node on the 240W worth of solar panels and monitor the batteries closely to make sure they are getting a full charge.
Since I estimate up to 20 Amp draw from time to time (transmit) and a idle draw of about 1.5 amps and currently only having daylight for about 10 hours due to it being late fall, I don't know if a 100 AH battery will get close to being completely charged though I suspect I'll see the battery get to about 90% and I suspect my node will idle ~90% of the time.

I suppose my best bet is to hook up the solar panels, test, see how the battery does, watch it closely and if it doesn't hold well then switch to AC.

The idea was to have a high availability node that will stay online when power goes offline and run even if the power is out for long periods of time.

Does that sound about right? Does anyone have any suggestions as to the best and safest way is to go about this?

[Sunking]

KF5LJW here. Tap the breaks. If you have access to good commercial power last thing you want is Solar mucking things up causing you problems. Practice what every commercial operator does like cell towers. Much less expensive than Solar and actually works great. I do this for a living,..

First there is no legal or economic way to Grid Tie. Forget it. You have no need for the solar. All you need is a DC Power Supply that can be used as a Float Battery Charger with a properly sized battery to carry you through outages.

Second you are way over estimating power usage. I assume you operate SSB? Or FM? If SSB yes you peak 20 amps but once you factor duty cycle of voice average is 1/8 of peak. I use to be stupid and worked weekend Contest. With a pair of Trojan T-105 batteries we operated two full days (Sat and Sun) using a 100 watt D857. Got home, charged the batteries to find out they were only roughly 50% discharged. You could not ask for better design as you never want to discharge more than 50% of the battery capacity.

Point I am driving at a pair of golf cart batteries can run a 100 watt Transceiver for 24 hour straight in a STUPID CONTEST or 2 full days. More than enough for most hams. All you need to do that and in reality you will get more than two days run time without power. is a 30 amp DC Power Supply, set to 13.6 volts and float a pair of golf cart batteries. No solar needed.

In fact you would be a very unhappy camper is you used Solar. Anytime the sun is shinning, you will not hear squat except bacon frying in the speaker from all the NOISE the charge controller makes. Especially cheap PWM controllers are the worse. There are only two known ham friendly Charge Controllers, and you have to pay up for them, 3 digits up. Even they still need more filtering. If you ggo solar, you have to turn it off while operating, or operate at night when it turns itself off. You think Solar Flares are noisy, wait until you try Solar Power

The only trick is sizing the batteries to DC Supply. At a minimum your radio needs 20 amps. That means the minimum capacity of the Power Supply has to be 20 amps. A 20 amp DC Supply can charge a battery sized from 120 AH up to 200 AH battery. Golf Cart batteries are 225 AH and would really need a 25 to 40 amp Power Supply. So do no tlet the balance of Amps to Amp Hours get out of range.

For every 100 AH of battery, you need 8 to 12 amps of charge current. Stay in that ratio.

73's

[visseroth]

I know another gentleman mentioned the same thing. Hooking the power supply directly to the battery but I thought I charge controller was needed in the middle. I didn't realize you could connect a 12v power supply directly to the battery. At least I didn't think it was safe. I guess it makes sense since the voltage of the battery would rise high enough to keep the power supply from pushing any more electrons into the the tank.
As for the node my plan was to put in on the 440 band, later also connecting it to he 2m band and 6m band as 6 meter isn't used much up here.
I hadn't thought about a mppt controller (my preferred controller) causing noise, particularly in the 6m band.

[PNjunction]

Just be careful about power supplies since they are not really battery chargers, but there is a solution.

Here is the catch 22 with your typical Astron:
You power it up. Attach to battery that is not totally dead. Charge commences.
Later, if you power down the Astron with the battery still attached, ZAP - it smokes the crowbar circuit, as it is not expecting a battery with voltage as a load, really.
OR, if you do actually lose power to the building, again - ZAP. You continue on with your battery, but when power is restored, you find the Astron smoked.

So it really should be something tested if you are going to use a random supply.

One way to get around this is to use something from PowerWerx to act as an automatic protective switch between a normal power supply and a battery.

OR, if you are familiar with Samlex, use one of their yellow/black "SEC" series of battery chargers (not just their more well known amateur power supplies) set to the supply mode of 13.6v. You may even use the dip switches to initially charge the battery stand-alone at say 14.4v for agm or flooded, and when done, change the switch to 13.6v for your float-charge long-term node operation. The SEC series can do BOTH charging, float, and serve as a stand-alone supply if you wish. VERY handy all around for the amateur.

[Sunking]

I know another gentleman mentioned the same thing. Hooking the power supply directly to the battery but I thought I charge controller was needed in the middle.

Don't be silly. A Battery Charger is a DC Power Supply. They are the exact same thing. In order to use a DC Power Supply as a battery charger is the DC Supply needs current limit and adjustable voltage. I use my Astron to do the job. Me and thousands of Hams have been doing that for over 30 years.

That is exactly how all commercial radio operators, banks, data centers, military, , call centers, 911 operators, telephone, or any application with mission critical systems operate.

[bcroe]

The current limit is pretty important, to avoid damage with a rather low battery. On small stuff I have done the limiting
with a series car bulb. At higher current the bulb lights up with higher resistance to limit current. As full charge voltage
is approached current drops, the bulb dims out, and bulb resistance drops by an order of magnitude to complete charge.
Bruce Roe

[Sunking]

The current limit is pretty important,

It is the most important part as is equally important voltage regulation. DC Power Supplies and Battery chargers are basically the exact same thing. Not all DC Power Supplies can used to charge a battery, and not all Battery Chargers can be used as a DC Power Supply.

As PNJuncttion said you have to be careful using a DC Power Supply as a battery charger. Great example is any of the Astron Power Supplies which is the preferred default choice of Ham Radio Operators. They are made like a Brick Chit House a Brute Force Supply. They make excellent Float Chargers but need a simple modification and Ham or Hobby Electronic enthusiast can do. You can control both voltage from 11 to 16 volts, and adjust current limit from 0 to Full ratted Amps. Today they even sell them with Battery Revert which is exactly what the OP is looking for.

As a Ham Radio operator I can tell you from a lot of experience, you DO NOT WANT A SOLAR SYSTEM to charge your batteries. There are 3 very good reason pros do not use Solar.

1. To expensive,
2. Poor performance, the nose generated by the Controllers is Unacceptable
3. Unreliable

Using a DC Power Supply or Rectifier is a lot less expensive to install and more importantly long term cost, great noise characteristics, and rock solid reliability. Solar is like Nobama, he is a cool cat, but a useless empty suit occupying valuable space.

[PNjunction]

In regards to #2 above, I have found that unless you drape your transmission line right on top of the simple pwm controller, there is very little radiated noise across the 3-30mhz spectrum. Yes, you may find a spike or two with an analyzer if you go hunting for it, but it is not a broadband hash.

Some units had switches in case this noise was noticeable, but that is mainly for a controller mounted within a cramped box with wiring inches away from the controller.

To this day, some amateurs are still using the older "ping pong" syle (cheap 5-buck HF, Coleman, Sunforce, etc controllers ) which are less efficient hysteresis controllers from the 70's, fearing the pwm will automatically be noisy.

What I'm referring to are the simpler pwm like Morningstar Sunsavers / Xantrex - Schneider units that don't incorporate a buck/boost mppt circuit. Other simple pwm controllers are similarly quiet unless you start to do things like tie-wrapping your transmission line to the controller wires themselves.

Once you are a few inches away, the vast majority of pwm controllers I've tried are pretty quiet for most stand-alone amateur setups. Mppt - best to test them with their buck/boost circuitry.