debianxfce wrote on Aug 24^th, 2015 at 3:22am:
The CMP is working when you get to something like 14.5 to 14.9V (depends on unit) and then it starts backing off, meaning the little green LED will start turning off. When it does this it opens the (-) side from the solar panels so if you measure across that you would start reading voltage (that is pulsing to start out so your meter won't like that).

Also, just recently I put more panels on one of these that I "beefed up" as you see in the pictures below with thicker traces and a extra heat sink off to the side.

It went up to 26A at one point when I had the "cloud effect", so that was only maybe 15 seconds, and the temp of the mosfet was up to 177F. I regularly run it at 150F and about 20A is typical. It seems to handle this OK. This is on a 24V battery system.

mike s. wrote on May 8^th, 2015 at 7:06am:
I haven't seen a spec for the max voltage on this controller.

But when your batteries are fully charged, the "charge" LED is off and so are the charging mosfets.

Which means your solar panels are not loaded so they are around their open voltage, which could be close to 40V for 24V panels.

When diagnosing a problem like that you don't want to start with the most costly method first, you would want to check things with your DVM first, check connections, check for shading at the panel (weeds / plants), clean the battery contacts, check the specific gravity of the battery (charged), maybe put it under a known load and watch it (you should already have an idea of what a good battery does under that load), check your gate motor to see if maybe it's pulling more amps than normal (crap in the gears, old grease, binding up, wheels rusted) or maybe running when you are not watching.

The LEDs are a general indication of charge, use your meter.

Batteries will run down a little at night, they have their own internal resistance, but it's not that much.

The Walmart Auto Center has a nice battery checking meter thing, some auto parts stores do too, not saying buy one even though you can buy a simple load tester, this is a nice one they use at the store. You can always take your battery in and ask nicely to have them check it, it will put the battery under load.

The bottom line is, use your meter. If the LEDs did go bad you should be able to tell what is going on.

When Lead Acid batteries are old and sulfated, generally they charge up fast but then run down fast. That is why I said do a load test.

That generally happens at about 5 years on the low cost deep cycle batteries (like walmart) and some people have reported 10 years on the expensive made for off grid type deep cycle batteries.

I am looking on an MPPT, which has a good efficiency, and when I search the Google for a while. coming out some Mppt, do you know how to choose a solar charge  controller. any instructions?

I took some pictures of my heat sink and beefed up traces mod.

I've been running this for more than a year now and have seen it being pushed to 20A. It works at 15A regularly every day. I monitored the heat sink temp and even when the room is over 90F it only goes up to about 115F at around 15A with this small extra heat sink on it.

The heat sink is a old CPU heat sink that is probably from the old 386 / 486 days. It's small enough to not put a big weight on the original heat sink which is held in place by the mosfets only.

I don't know if the beefed up traces are needed since they are pretty wide but it only took a few minutes and seemed like the thing to do. Notice I only beef up the important parts where the big current flows.

A lightning storm came overhead and took out the CMOS chip U2 "HEF40106 Hex Inverting Schmitt Trigger" so I am now using my spare CMP 12/24 (with heat sink mod, same thing) but I will simply replace the chip and I am sure it will work and then it will be my spare. You should always have a spare for equipment this important and at this price, why not?

CMOS chips are known for being sensitive to static discharges and surges can cause them to latch up.

How do I know it's the CMOS chip? Because it's melted in the center where the internal chip IC die is located. If you look close you can see it in the pic. This is normal for a latched up CMOS chip gone haywire.

The voltage the chip runs on varies but never goes above 15V and I checked that so it wasn't a over voltage problem and all it needs is a new chip. Mosfets all check out OK!

This is why I like simple stuff like this, it's easy to fix yourself.

Yes, my panels are grounded and also sit on the ground, the wires are buried, but that doesn't always save you. Lightning is crazy and you never know what it might do. It produces a EMP, a RF pulse(s) of very high magnetics, which can inductively couple into your wire UNDERGROUND or simply travel as RF down a wire. Lightning is very high power. I looked and it wasn't a direct hit as far as I can tell, no burn marks I could see, but small "streamers" are known to scatter around a lightning hit.


UPDATE: Replaced U2 and everything functions OK again.

Wow! It is great news...

electron ... thanks for looking into these little controllers. My question (if you have time to answer):
Do you think that the load (bulb) outputs of 2 or more of these controllers could be connected to the one inverter load? I run a very low cost solar system and the hardest and costliest thing is the batteries. I don't like running batteries in parallel, particularly second hand ones so would it work if I had separate pv panel(s) and one of these controllers for each 12V battery bank? Then take the outputs of each controller to the one inverter. Would they interfere with each other?
I suppose an alternative to connecting the outputs could be isolating diodes between the positives of the banks and the inverter input. The diode voltage drop would be a problem and maybe it would interfere with the battery voltage sensing by the controllers.
What do you think?
At the moment I have 3 banks of 2x6V 200Ah batteries. These 3 banks in parallel worry me as if one cell goes it will take out the lot if it happens when I'm not there for a while. So I'd like to have 3 sets of panels running 3 controllers into three seperate 12V (2x6V) banks.
cheers
John

soundbyte wrote on Jul 15^th, 2012 at 9:31pm:

There's two main mosfets for charging, look at the bottom of the circuit board and you can figure out which two are in the charging part on the (-) leads. The other one is the same type of mosfet but it's used for the "light bulb / load" output.

There's your spare mosfet!

Check the mosfets with a ohm meter, they mostly fail SHORTED, so it may be easy to find the problem.

Do some basic stuff, check the transistors and diodes on the board, they would be the easiest to replace. The surface mounts chips are a pain to replace and hardest to figure out if they are bad unless they are totally dead.

Sometimes with a little patience you can bid these at $5 with free shipping so there comes a point where it's not worth messing with and just call it spare parts.

If you do find out what went bad you want to think about why it went bad so it doesn't do it again, did you have a surge? Is there something in the circuit that could send higher voltage pulses down the wires?

It may help to add a capacitor near any device that you think may be sending spikes down the line.

I ran a test with this charge controller and a 300W Grid Tie Inverter connected to the same solar panel and the results are good.

I hooked the GTI up as usual, direct to the solar panel. The grid tie is the 14V to 28V input type.

I also hooked the charge controller to the same two wires from the solar panel, it was now in parallel with the GTI.

The 12V battery was hooked up to the two terminals for the battery. ALWAYS hook up the battery first!

When you do this what happens is the battery will go to about 14.7V (or where you adjusted it with the little POT inside the controller) and any leftover energy will now go to the grid!

Some energy is always required to keep a battery charged so this is cheap way to keep a battery charged for emergencies. The rest can lower your power bill.

If you run down that battery, GENERALLY the solar power goes to charge it up first, because the GTI won't kick in till it sees about 14V. BUT.....

SOME IMPORTANT POINTS:

The GTI tends to pull on the battery too much in the mornings so you DO NOT GET A GOOD CHARGE FIRST THING IN THE MORNING which is not good for sulfation! Once the GTI pops on it will actually pull it down to a lower voltage than 14.7V

At 14V the GTI does not perform well, would be better to run it at 24V.

The battery (-) is switched on and off by the solar controller, so the battery can NOT be connected to your whole system if the solar panel is also part of that system.

So if you do this that battery and any loads you want to drive with it should be separate, or your panel has to be separate. I hope that makes sense.

Second thing, depending on how you set up your earth grounds, you want to check and make sure the GTI's ground and (-) are separate and floating, they generally are but just check that and make sure if you going to have the solar panels separate from the ground on the battery.

Third thing, you should use a 50W or better solar panel so the voltage can come up enough even with the GTI running that there is some voltage left to put a little into the battery to keep it topped up.

This is not the BEST way to do this but it's better than nothing. If it's confusing, just draw it all out.

Bought one of these circuits to regulate the battery charge for a old diesel AC generator with a 24volt control panel, the rectified "DC" supply voltage was to high and blow the two controlling IC, so I reversed engineer it by drawning a schematic of this PCB to find out how it work, I replaced the IC U2 (Cmos schmitt trigger NOT gate x 6) and U3 (Oprational Amplifier x 4) to get it working again. I found that the U2 component was a high-voltage gate that only Texas Instruments make, its rated up to 20volt and the U3 rated to 32volt max, the way they get round this is to use 15volt breakdown diodes "zener diodes" to adjust Q2 base a NPN transistor which supply the IC with there power.

The pot W2 adjust the supply isolation voltage turning the charging N-Channel mosfet Q6 off by turning on NPN transistor Q1 on via an optical coupled isolator transistor U1..

This forum I found when I when looking for a schematic without success, so desided to share my finding for anybody else that may be having problems, in short make sure your supply doesn't go above 28 volts otherwise may get some problems.. if it does you could try adjusting the the supply mosfet to isolate at lower potential from 28volts its mean't to isolate at, the charge LED will pulse then go out when it is fully isolated..

wow its really nice. thanks for the post.
tell me how far is it feasible?