Solar Discussion

[wavery]

My diode is inside the electrical connection box under the panel. The typical diode voltage drop is 0.7V but I may be dropping that twice if I have another one in the controller.
 
I wouldn't want to bypass my diode and charge controller completely. My panels can crank out over 17V at around 4.5A each. I would feel like I had to watch it too closely. I can understand doing it on a boat, hard to plug in the TV or take the battery elsewhere when you are on the water.
 
Oh yea.......
My $@*#&% laptop died and I think I lost all of my bookmarks. I pulled the HD out and hooked it to my daughters PC through a USB HD box. I clicked on Mozilla Firefox on the drive that came from my laptop and it acted like it was performing a new install. When I looked at my bookmarks, there were only the default ones in there like when you install a new browser. Looks like I should have copied the bookmarks before starting any programs. Will have to get all of the solar sites back that I once had.

The voltage on the solar panels is really irrelevant unless the batteries are fully charged. It is the amperage that is important. Some solar panels are capable of over 30v with no load. However, if you measure the voltage at the battery when the solar panel is at max output, it will not exceed 14.5 unless that battery is fully charged. That is when the voltage becomes a concern. Even then, the voltage is much lower than the "no load" rating of the solar panel. Many wind generators are equipped with 36v motors. Same theory applies. The resistance dictates the speed of the rotating blades on the wind generator. If the wind is very strong, the voltage may spike to 15v but that is rare and only happens for a few seconds at a time. The same is true from the solar panels. The output voltage is dictated by the resistance. At zero resistance, the output is higher. In the case of the wind generator, if you disconnect the generator from the battery (eliminating the resistance) the blades may spin so fast (in a stiff breeze) that they will destroy themselves. They call that going "Super sonic".

The reason that hard wiring through a toggle switch is handy is because you may NEVER achieve a full charge on your batteries from solar panels unless your panels far out-way your storage capacity. That is very rare and in that case, I would increase the storage capacity. Otherwise, you are waisting $ on solar panels.

The obvious exception would be if your trailer is sitting in storage or the batteries have been freshly charged. In that case, you switch over to your charge controller and forget about it. Once your batteries drop below 13v, you could have the option of going to a direct charge if you have a switch. You wouldn't have to check the voltage on the battery more than once in a 24 hour period, at peak sunlight. In the real world, that rarely happens though. That extra .5A is nice, especially when you paid for it and aren't getting it.

[chasd60]

The reason that hard wiring through a toggle switch is handy is because you may NEVER achieve a full charge on your batteries from solar panels unless your panels far out-way your storage capacity. That is very rare and in that case, I would increase the storage capacity. Otherwise, you are waisting $ on solar panels.
 
The obvious exception would be if your trailer is sitting in storage or the batteries have been freshly charged. In that case, you switch over to your charge controller and forget about it. Once your batteries drop below 13v, you could have the option of going to a direct charge if you have a switch. You wouldn't have to check the voltage on the battery more than once in a 24 hour period, at peak sunlight. In the real world, that rarely happens though. That extra .5A is nice, especially when you paid for it and aren't getting it.

I have 2 Group 27 batteries that have a total of 220AH capacity. My panels are 80W each and I do use an MPPT charge controller. I guess I may have seen a few times that this would come in handy. Mostly after a few non-productive days and there is no danger at all of achieving full charge even if I had 10 hours of full sunshine and I achieved full theoretical output. This year I am going to rewire the panels in series to take better advantage of the MPPT controller which would give me a nominal 24V panel output.
 
I had wondered why they put a resistive load on windmills that some use for heating water. It must be to control the speed of the blades after full charge?

[wavery]

I had wondered why they put a resistive load on windmills that some use for heating water. It must be to control the speed of the blades after full charge?

That's correct. You can't put a voltage regulator on a wind generator because the voltage regulator disconnects the generator from the battery when the battery reaches full charge. That gives the generator zero resistance and allows it to free-wheel and the blades can reach super-sonic speeds. When I was in Hawaii, I had a wooden propeller explode in about 50kts of wind (because I ignorantly disconnected it from the battery). It through shrapnel everywhere at horrendous speeds. Fortunately, there was no one on deck because they may have been killed..

The proper way to set-up a wind generator is to put it on a 14.5v relay so that the current is either diverted to ground or to something that supplies a load. I used our 25g hot water heater. If the wind was too strong over long periods of time, I simply shorted the contacts. That put so much resistance that it would almost stop the blades. That allowed me to stop them by hand and tie them off to keep them from turning.

So that you don't get the wrong idea, I only experienced that about 3 times in a 3 year period. Wind generators are only as efficient as the wind that it is exposed to.

I had an in-line digital amp meter on my solar panels and my wind generator (when they were not by-passed). I have seen the wind generator put out 30amps in 30kts of wind (in gusts).