Help With a Charge Controller

[BobW55]

I have a 6X10 Enclosed trailer. I am planning on installing 2X 100 watt panels on the roof, to either Golf cart batteries or some sealed lead acid type. (still searching on the batteries)
The set up will be use to recharge RC Aircraft batteries. Most are small but I do have a few 6000Mah ones. The charger I will be using has a low voltage cut off so I will not have to worry about taking the storage batteries below 50%. I may only fly once/twice a week so plenty of time for the system to recharge the storage batteries, trailer will be parked in full sun when it shines.
I also want to install a small roof vent fan that only needs to run durring the day.
A few options I have are:
1) A separate solar vent fan, but most do not have good life expectancy, or will only work in full sun.
2) Tap directly off one of the panels to drive a small computer fan. not the best option.
3) Find a charge controller that will turn something on only durring the day (BEST OPTION)
4) Use a timer or some other relay function that will shut the fan off at night, or when the panel output falls too low.

Does anyone know of a CC that would turn a load ON durring the day as opposed to night as most do?
We are talking a 6"- 8" DC Brushless fan, just needs to move enough air to keep the trailer from becoming an oven. Trailer is white.

[Sunking]

Bob I fly RC aircraft 3D FWIW. Unless you plan to camp out and use the batteries for more than 1 day, no solar is required. At 200 watts on a pair of 6-volt golf cart batteries doe not do much.

You did not mention what voltage the 6000 mah cells are but if I assume 4S and you run them down to 70% DOD will require roughly 130 watt hours to recharge. Realistically with 200 watts of panels you are talking recharging 4 times in a day.

Now with a pair of 6-volt 225 AH Golf Cat batteries charged at home, and your LiPo's charged up at home before you go, the golf cart batteries can recharge a 4S 6000 mah pack 12 times to 50% DOD, and a max of 18 going to 75% DOD. Look at getting a pair of Trojan T-105 batteries.

[BobW55]

I have some 4S 6300mah batteries, and 5S 6000 Mah batteries. The rest are all 2-3 S.
Reason wanting to put in solar is to keep the storage batteries charged, so I don't have to remember to do so before I leave for the flying field.
Although I currently charge hooked up to my car battery, you can only do so many before you have to run the car. Had to get a jump once.
Plus I have a feeling when I build the charging station into the trailer, others will want to use it. If I were to charge 2 at a time we are talking 6 amps each for my largest batteries.
I am still doing the math on total capacity needed so I can figure how big of storage I would need.
I am more concerned with venting the trailer durring the summer, some of my aircraft are foamies, and they don't like ovens.
I am pretty good with electronics and may just build a voltage monitor to watch the output of the panels and switch them onto a fan, just thought it would be more convenient to let the CC do the work.
I still have to buy the trailer first, but that is this weeks task.

[Mike90250]

some of the high end, $500 controllers have some programmable output channels that could activate a fan. But what I would do, is find a RV solar roof vent fan, and buy a couple of them, use 1 now, and keep the others as spares. I would NOT want the fan dependent on the batteries working right.

[BobW55]

Id love to have one of those RV style solar fans. Most of the reviews I have read on them are dismal.
They are usually using too small of a panel unless in 100% direct sun, or the brushed motors burn out quickly.
I have a small 12 volt 4 watt panel here that has the same issue. Need about a 15 -20 watt panel to drive a computer muffin fan in partial sun.
Only need the fan to run if the sun is out. On cloudy days or night time there would enough passive ventilation to keep inside the same as outside.
I agree, I do not want to add batteries to run the fan. I may just get a smaller panel just for the fan.
Still have to get the panels, batteries, and CC for the charge station.

[BobW55]

After much consideration, I am going to use my little 40 watt panel to drive the vent fan, Been playing with it all day and it drives a 6" computer fan just fine. I was worried that it would not cold start, but it does. Does not take full sun to start either.
Going to get two 100W 12 volt PV panels. I have a line on two 6 volt 230 amp golf cart batteries. I totaled up the worse case I had to charge all my Lipo batteries from zero, I only need 37 amps of capacity. So far have only had to recharge at the field 4 times, more due to the PITA to do so. I am sure other will want to use it too. I would rather be over capacity then just enough.
I am also adding a 100 Watt inverter should I need to charge a radio of something else that requires AC.
I am left with choosing a charge controller. I would like to go with a 30 Amp MTTP to allow for future expansion if needed. This is the part I am stuck on. Not sure who to buy from. I see many reports of knock offs being sold on Amazon, makes it hard to tell if you are getting the real deal. I would prefer one that has a display, not just LED's. Save me from wiring separate voltage and amp meters.
Any Suggestions for a controller?

[BobW55]

Finally just about finished my build.
Went with 3x 100Watt 12 volt panels (GMA Solar of Canada), a EPEVER CC 30amp.
The CC allows you to program an on/off time, so I have it kick on at 8:00am and kick off at 8:00pm. Have the vent fan running durring those hours, don't need it at night. It is just a small 120mm 70 CFM fan, but it keeps the trailer from becoming an oven. Have the lights (LED) hooked direct to the battery for times I want to work in there at night. Still have to run the wires from the fuse panel to the RC Battery charger. Have to build the work table in the V nose first. My 750 Watt inverter is direct to the battery, it has it's own 30 amp fuses. Only need that for a soldering iron, and a iron for heat shrink covering.
I ended up with a 100 AH deep cycle battery, the golf cart batteries I wanted were way too expensive. I am hoping to stress test it tomorrow, charge up everything I have with the solar disconnected and see how long it take to charge back up and at what rate.
Will report back.

[Sunking]

My 750 Watt inverter is direct to the battery, it has it's own 30 amp fuses. Only need that for a soldering iron, and a iron for heat shrink covering.
I ended up with a 100 AH deep cycle battery, the golf cart batteries I wanted were way too expensive. I am hoping to stress test it tomorrow, charge up everything I have with the solar disconnected and see how long it take to charge back up and at what rate.
Will report back.

30 amp fuse on a 12 volt 750 watt inverter? Where did you come up with that?

A 750 watt Inverter requires 80 amps at full power. However really does not make much difference because a 12 volt 100 AH battery cannot supply 80 amps of current anyway. You Inverter is way over sized for your panel wattage and battery. In addition 300 watts of panels is too much for a 100 AH battery. Fine for a pair of golf cart batteries, but way too much for 100 AH.

[BobW55]

Typo on my part. Should have been 3 amp fuses. Old inverter I had laying around. As for the batteries. It is what I have for now.

[Sunking]

Typo on my part. Should have been 3 amp fuses. Old inverter I had laying around. As for the batteries. It is what I have for now.

Huh? 3-amp fuse on a 12 volt 750 watt Inverter? That is nonsense. Me confluzed.

[SunEagle]

Huh? 3-amp fuse on a 12 volt 750 watt Inverter? That is nonsense. Me confluzed.

If that was a 3 amp fuse on a 750 watt inverter 240 volt output side it makes sense otherwise something is a miss.

[Sunking]

If that was a 3 amp fuse on a 750 watt inverter 240 volt output side it makes sense otherwise something is a miss.

Maybe but I kind of doubt it because Inverter Outputs are not normally fused. Inverters cannot generate enough fault current to operate most OCPD fast enough or enough fault current to damage wiring. GFCI they have, but smaller units under 2000 watts rarely have OCPD.

[Sunking]

Does anyone know of a CC that would turn a load ON durring the day as opposed to night as most do?

Controller No. However there are tons of 12 VDC Photoelectric Switches for sale from $3 to $10. Most will handle 5 to 10 amps.

[ThisBigRoadTrip]

Hi

Registered but unable to create a new thread for some reason so please accept my apologies for posting here. I am in Baja and a bit stuck with a Charge Controller issue.

I re-wired the solar panels to charge controller with 8awg cable and also the connections from the controller to the battery. Switched the system on, everything works fine. Got a good charge, nothing unusual happening.

This morning I woke up before daylight, hit the inverter button on my Magnum Battery Monitor Kit display and switched my AC kettle on. The Go Power Solar controller display was showing the moon icon, indicating night, and 0.0 amps indicating no current from solar. When I switched the kettle on the Go Power dislay volatge dropped - normal I think - battery percentage dropped from 90+ to 60%-ish. But I git an audible beeping alarm, seemed a bit sporadic but regularly beeped. Also, very occasional a POL code appears on the display.

When the sun came up a few minutes later, the sun symbol appeared on the display and the display register 1.1a or so of charge. I turn on the Magnum inverter and kettle, the voltage / percentage charge on the Go Power display drops . but this time no alarm and no POL error.

I re-created night by putting a tarp over the panels. Moon symbol re-appeared and 0 amp charge showed. Switched on the inverter and kettle, got the same issue. Beeping and very occasional POL code. Removed the tarp, daylight symbol showed, the display showed charging amps at expected volume and kettle boiled without an alarm (Go Power voltage and charge percentage still dropped though)

I assume the Go Power only reads battery voltage for percentage so the drop in voltage and percentage is to be expected?

But the alarm beep and POL code shouldn't appear and strange tat it only appears when night symbol and 0.0a of charge is showing on the controller.

Any ideas?

Apologies again for thread interupt.

[Sunking]

Any ideas?

Apologies again for thread interupt.

Yep quit using voltage as indicator of charge. You can only use voltage if the battery is rested and open circuit voltage. What you are seeing is normal. Hit the battery with a large load like a Kettle or Coffee Pot early in the morning is going to drag voltage down and set off alarms. Might be an indicator of a battery getting ready to fail if it is a large battery.