Solar Power and Radio
I see this coming up a lot and would like to take a minute to offer some tips on the subject as they can be a good match for the Low Power operations. I have been involved with both Grid Tied and Off-Grid Battery systems for about 10 years in the design build biz for Cellular Telephone and Small Business now for about 10 years and much can be applied to ham operation.
For 12 volt DC operations with 200 watt or less HF transmitter power off-grid solar battery systems can be used without tremendous expense and minimal equipment requirements. Required equipment is a Solar Panel, Charge Controller, and Battery. It is especially useful for field operations, not so much for stationary ham shacks because you can do the same thing better and less expensive with just your DC Power and a battery. Legal limit systems using amplifiers is quite a bit more expensive an dthings get a bit more complicated with using low 12 volt equipment and batteries delivering some 2000 to 3000 watts to a inverter.
When designing for off-grid battery systems with everyday use gets fairly involved with calculations of daily Watt Hour usage and location, so I will not go into that depth of detail. But for the intermittent use of ham radio operating at 12 volts there are some good Rules Of thumb you can use to provide all the power you need.
So here we go for panel wattage, battery capacity, and charge controller relationship size of 12 volt battery systems. For each 1 watt of panel wattage
- 1 AH of battery capacity
- 0.8 Amps of Charge Controller.
The minimum size IMO should be a 100 watt panel, 100 AH AGM battery, and 10 Amp Charge Controller for a 100 watt HF Transceiver with a couple of caveats depending on what Battery and Charge Contoller type you select.
A 100 watt HF Transceiver operating at full power using FM is around 16 to 20 amps continuous and is the worst case scenario for the battery to deliver. There are two basic battery types of Flooded Lead Acid (FLA), and Sealed Lead Acid (SLA). Your battery type and selection is the MOST critical component of a battery system being either Solar of just a DC power supply.
I have discussed this elsewhere in detail so I will not go into depth of batteries. What I will say here is do not use Gel batteries which is in the SLA family. The preferred types to use are FLA or AGM. Lead acid batteries come in three classes of Deep Cycle, Hybrid (Marine, RV. Golf Cart), and Starting/Cranking. DO NOT USE STARTING/CRANKING BATTERIES.
OK so this leaves you with FLA or AGM. Which do you chose? Depends on your budget and how long you want the battery to last. Each type has Prosí and Conís.
FLA batteries are the least expensive, very rugged and can take abuse, and last longer than AGM. The down side is they cannot take as high of a Charge/Discharge rate as AGM,s because of their higher internal resistance, and do not lend themselves well to transportation or mobile applications for field operations. The Charge/Discharge rate is important. Max recommended rate is C/8 where C= the 20 hours discharge rate Amp Hours of the battery. Example a 100 AH battery you would not want to charge or discharge the battery more 100 AH / 8 Hours = 12.5 Amps. So if you have a 100 watt HF rig you really want a 150 to 200 AH minimum battery. That means a 150 watt panel and 15 to 20 amp charger controllers. NOTE: You can use lower wattage panel and smaller controller but the minimum charge current on FLA you want is C/12.
AGM batteries have much lower internal resistance so they can be discharged up to a C/4 rate which means for a 100 watt HF rig you can use as low as a 80 AH battery with a 80 watt solar panel. AGMís are very portable and can be mounted on their side if needed. The down side is for a given AH and voltage they are about 100 to 200% more expensive than FLA. In addition they do not last as long as FLA and cannot take the abuse of overcharging or Equalization.
Well that is a start, Questions, Comments, and Flames are welcome.
Thanks, that taught me a lot of info I'll be able to use for my future camper with solar cells!
Well do not get too excited because the approach I just took is not the proper method for daily reliance and use. Using Solar on radios is not demanding or taxing on the panels and batteries. You had best go read THIS THREAD on another forum to design a Off-Grid Solar Battery System. Otherwise you will likely spend a lot of money and go dark. For daily use you need to know how much energy you will use in a day, location, and time of year use. Then design a system to work around the parameters. RV's can use Solar with limited results, very limited results. RV's just do not have much room for panels or batteries. FWIW you will get a lot more power using the vehicle alternator to recharge batteries for 30 minutes per day, than what a 200 watt panel can generate in a day.
Originally Posted by WX7G
I agree I spent quite a while using a Kill A Watt meter to measure the use on my computer and radio gear. Did the TV and stereo too. Total average draw is 400 watts, stuff runs about 10 hours a day most days. about 20 amps at 24 volts from my battery bank so minimum 200 amp hour use. Figure 5 hours a day for peak charging on the average system. I am going to end up with a 928 amp hour battery bank and 1,100 watts of solar panels by the time I finish. Have 4 more panels shipping this week, will grab 4 more batteries next time I get to town.
MPPT Charger Controler
I purchased a 10A MPPT Solar Charge Controller Regulator Tracer 1215RN 150V input 12/24V from a source on E-Bay. It appears to work as advertised. But unfortunately it generates 30db harmonics plus lots of other trash accross the entire HF spectrum. Sending it back to China will cost me about 50% of what I paid for it. So I am going to try and reduce/eliminate the EMI with chokes on the 12V feed to the battery system. I don't know how successful I will be. Anyone have any experience with MPPT charge controllers?
My Morningstar MPPT-45 charge controller only has a couple birdies to deal with. It is quiet rf wise.
Ken sorry to hear about your problems. I do have a fair bit of experience with both PWM and MPPT controllers. I looked at your unit and see some Red Flags that indicate what you have is more than likely a PWM controller. There are a lot of complaints about the quality of solar products coming in from China. To give you an example as a comparison a comparable sized MPPT unit from MorningStar cost around $240 for the MorningStar 15 amp SunSaver, and the PWM version is $80.
Originally Posted by W8JVP
To address your problem you can certainly attack the battery side, but more than likely the problem is coming from the input side from the panels where the switching is taking place, and is radiating into your antenna. Pretty easy to tell by just disconnecting your antenna and see if the noise goes away. If the noise stays when you disconnect the antenna, then it is entering via battery power input.
Dereck: Your right! The EMI is coming in on the antenna. By all indications the device is MPPT. The DC to AC converter is running at 55 Khz.I have harmonics every 55 Khz on all bands. Upon inspecting the device I discovered that the PC board is mounted on an aluminum heat sink and the cover is plastic, So no shielding! The negative battery and solar panel terminals are not grounded to the heat sink chassis.
Originally Posted by KF5LJW
I installed the device in a metal box. Ran the battery and solar panel leads through ferrite toriod with multiple turns. Grounded the negative leads to the heat sink and the metal box then to earth ground. Approach eliminated the EMI trash and reduced the 55 Khz harmonics significantly - S3 on 20 meters. My IC 256 Pro III eliminates the balance. I used mix 77 toriods. Might try mix 43 and see if I can improve the suppression
Last edited by W8JVP; 08-08-2012 at 01:52 PM.
Reason: Incomplete response