Since we moved here I have wanted to make the station or at least the radio, solar powered. I have been collecting the bits and pieces since we moved here. Originally I had been using a 7 AH gel battery to float across the 12 volt bus but it was charged by the Kenwood 25 amp power supply that I generally use for the radios. I contemplated eventually buying one of the little 1 or 2 watt solar chargers to keep the battery topped up but never seemed to get around to it.
Last winter, Harbor Freight had their 5 Watt solar module on sale. I jumped at it since it was relatively inexpensive … made in China! They captioned it as a battery charger but I suspect that it is too big for my 7 AH battery since the rule of thumb is 3.5 Watts of solar power for each 100 AH of battery. The 5 Watt solar charger definitely would be overkill for a 7 AH battery.
Over last summer I went searching for a small charge controller since the charger was too big for most any battery I would likely buy, I found a small 3A solar controller at All Electronics. It was cheap enough and it would ease my mind about overcharging a small battery.
In the mean time the 7 AH battery died as did my 3.5 AH battery so I had an unmounted solar charger and no batteries to charge.
Last week, I decided to just do it and went on line to see what batteries were available. I had in mind a gel battery of about 15 AH. After looking through pages and pages of battery specs and costs I went to Batteries Plus and looked at their stock. I found a AGM battery 35 AH for a reasonable price. My math indicates that I should meet my objectives of 2 hours per day running 25 Watts PEP as in PSK. That means roughly 2 amps during transmit and .84 amps during receive. Using these figures I believe the weighted agerage is somewhere around 1 amp assuming 40 minutes of receive for every 20 minutes of transmit. At 1 amp / hour, I need 2 AH of battery for my nightly session. In fact, it should be sufficient for running all day and night during an emergency or for Field Day.
I did not find this solar system calculator until after I had purchased everything. It shows that I am not in good shape on the solar side of the power system. To recharge the battery in one day I need to replace almost 25 Watt Hours of energy. At 15 Watt Hours per day during the winter (3 good sun hours at 5 Watts or some combination of sun equaling 15 Watts) I can expect to recharge the battery in a little less than a day and a half. To recharge the system in one day, I will need roughly two 5 Watt solar panel or one 10 Watt array. So when I find a sale on a 15 or 30 watt arrays I will look into upgrading the solar side of the system otherwise for each day I use the system I need to recharge using the Kenwood power supply and can only expect the solar charger to work as a float charger on the days I do not ue the radio. Evidently the 3.5 watts per 100AH of battery is for float service only; We will see what happens. I have the battery on the solar charger now and am waiting to see how long it takes to bring it up to 13.2 volts, my estimate of the float voltage. I had it on the float charger last night but it never came up to 13.2 Volts … so we will see what happens.
