I need a schematic for 36v Solar Charge Controller, or do I?

Each battery + controller + panel is designed to drive some 12V load. So, build one system with one battery, one panel, and one controller. It has two wires coming out to drive the 12V load.

Build two more. Then, take the ground wire of one, and hook it to the hot wire of the next one, etc. Attach the actuator across the final two pairs.

Regards, Bob Monsen

You're overthinking it. hook the panels to the battery and put a zener across it to limit the voltage to whatever float voltage your batteries require. If the panels don't already have isolation diodes, you'll probably want one of those too.

Yebbut ... why do you consider series-connected panels and series-connected batteries is a cause for abandonment?

Connect each panel/reg to one battery, then series the three of them. Draw it on paper first as described above.

(i.e. go with Bob's suggestion.)

Does the actuator have enough torque to open the gate at 12V? It's worth the experiment before you sweat out a more complicated design.

Having a real swinging professionally installed gate, I suspect this will be a more complicated project than you think. [In my case, two swinging gates, but you get the idea.] If you get tired of the project, I suggest Door King. The competition (which unfortunately I own) is very buggy. I'm getting really good at repairing the gate. Better than the service call from the gate installer (about $150 each visit). The Door King gear doesn't need constant tweeking.

The gate needs a microswitch to turn off the motor. This involves a cam that need adjusting. Why adjusting? Well, the wind moves the gate arm and disturbs the cam. The Door King scheme has a self adjusting cam scheme. Elite (what I own), doesn't have this scheme. Without the self-adjusting cam, the other alternative is an electromagnet to keep the doors still as the wind blows. Clearly not an option for your remote gate.

A real electric gate has a number of safety features. There are a number of loop sensors to insure the gate doesn't swing and hit a vehicle. There is a torque sense scheme so that if it does hit something, it stops. There is the issue of entrapment zones. You need to insure the as the gate swings, there is no way to trap someone behind it.

There is quite a bit of hard knocks engineering in these products.

--- I think you can do this with your existing panels: (View in Courier)

If not, then this should work:

Hi Miso,

Thanks for the reply, yes there is enough power at 12v but it takes about 2.5 minutes to open the gate. At 36v it is a around 40 seconds.

My nearest neighbor is 1 mile away and if anyone gets trapped in the gate it will be easier to shoot them for trespassing. Kidding, I appreciate to your suggestions but being somewhat stubborn I will proceed. I currently use a garage door opener on it but the closing is pretty fierce at the end as the mechanical advantage swings in favor of the motor.

I use limit switches to stop the gate at each end.

Dave

Bob,

Thanks for the reply, but wouldn't that mean the second in line controller is seeing 24v and the third 36v?

I can see that across A-B =12v, but wouldn't the output components of the second controller see 24v as in A-C. Likewise the third controller's output components see 36v as in A-D?

This is reaching beyond my understanding of electronics so forgive me if that is a dumb question.

Dave

I'm pretty sure this answer has already been given but just connect 1 solar panel to 1 charge controller to 1 battery, do that for all 3 batteries, then connect the 3 assemblies (solar panel, charge controller, battery) in series.

The only problem I can think of with doing that would be if one battery goes bad, the good battery(s) could try to reverse charge the dead battery. You can use a rectifier reversed across each battery so it will start conducting and prevent a voltage reversal on the charge circuit. The charge controller may be able to handle a reverse voltage since some are designed that way in case someone connects the polarity backward.

RogerN

Here's a better ASCII art...

A-B = 12v A-C = 24v A-D = 36v

Even though the batteries are series, so are the output components of the second and third controllers. Or even worse, would all of the controllers have their output components at 36v?

The more I think the more confused I become. :)

Dave

each controller and battery only sees 12v. This is because they are unreferenced to anything else. A-D sees 36 volts but the difference between each set of battery terminals is still only 12 volts - I make this statement on the understanding that you will not do anything silly like bolting all the "grounds" (0v terminals) to a steel roof or anything like that.

Actually, I've been caught in the entrapment zone when a driver tripped the far loop. [I share that gate with one other house.] The pro gates swing fast, though I could have darted out of the way had I not known about the safety zone.

You need some wiggle in the limit switch mount if the wind is going to blow the gate, or something springy before it hits the limit switch. There is also the issue of fire department access, which involves a Knox box. FD charges you for the gear. This way they get a key for the gate but it's not like they need a key for every freakin' gate in town.

My gate has it's own address. Yes, really. It gets it's own power billing, which reguired a pedestal for power distribution and the meter. I even had to run it past the traffic engineer to insure I don't cause any issues. [Access is from a cul de sac, so this was really overkill.] It is nice to have at least one car length of level ground on the street side approach to the gate, especially if you will have a keypad.

Getting back to your motor, if the 12V hardware exists and you like it, I'd look at boosting the voltage to the motor with a DC/DC. I can't say I've seen any high power boost designs (first hand), but I don't see any fundamental reasons why it can't be done. The advantage to boost the motor is all the other stuff is COTS. Charge controllers have lots of hard knocks engineering in them too. All good engineering has it's basis in thing that failed in the past. Toyota will probably make a damn good drive by wire throttle one day. ;-)

...but don't burn up the Zener on a hot, sunny day. I'd use a current limiting resistor in the discharge path. You call still bleed off the excess charging current, but dump the heat into a resistor, not the Zener.

I agree. You probably don't need anything too complicated here.

Or, just use conventional 12 volt cells, charging system and a cheap buck boost converter to up the voltage for the motor when initiated.

That's why they invented math. You can't get any meaningful dissipation in a resistor (in series with a zener) while maintaining tolerable overcharge of the batteries.

The panels only put out 4.5W on the best day of their lives. That's not a very big zener. A fuse sometimes helps.

Of course, you can design a more complicated system that works "better".

r.

l be

There can be a problem with this sort of design not starting up nicely if the voltage rises slowly. I assume you are suggesting power MOSFETs as the transistors since you only have 2 resistors in the design. Just as the panel starts making enough voltage to bias the MOSFETs on, the current can rise quit high with the MOSFETs passing that current while seeing the panel voltage.

If you use bipolar transistors, you can do it without the capacitors. When the collector current passes the amount that the base drive can support, the circuit toggles to the other state. It requires 4 resistors usually.

at

Wouldn't be much cheaper and simpler to use a single 12 volt panel and battery system? Make a very basic multivibrator circuit to boost voltage to the motor.. Only needs to be on when needed.

P.S. I've done this before using a control xformer so that I would operate a series 120V motor from a 12V battery and it works fine along with it being simple and cheap.

I suppose one could make a toroidal powered iron xformer and run at a higher freq.

Jamie.

Use Courier font:

In this circuit, if each panel consists of a single string of solar cells, a narrow shadow from a tree branch etc falling on a _single_ solar cell will drop the current output for the whole constellation of panels.

What happens, if the middle panel is in shadow producing only a small current and small voltage and the other two panels are in full sun light, does the controllers handle the situation properly, without destroying the controllers ?

Why not spend a few dollars and by a 12 volt version? They are used on trailers, in place of the hand cranked trailer jacks. 36 to 42 volt jacks were used on Sat dishes because of the I/R losses in the wiring.