solar panel controller and IRF1404s

I'd use something like an LM317 adjustable voltage regulator...cheap, reliable simple.
OK it may waste a bit of power, but it can be set up to regulate volts or current (They have good application notes). If you use a current sensing resistor you can switch in different voltage setting resistors as the battery volts increases to provide two levels of charging.

Main thing is to use the battery manufacturers data to ensure best charging conditions for optimum battery life.

I'd avoid FETs as they gan go s/c for no obvious reason...if you really need low volts drop use a relay.

Del

Hi moomoo

I don't know your level of electronics so I'm going to wing this one. I would use a SMPS to convert 12 to 6 you will also get the benefit of more current to charge the batt. How often is the pump used and when? What are the electrical spec's on the pump, current or watts? What kind of sunlight have you have there? Location? You would need 7.2 volts to chg the battery Don't overcharge or discharge below 5.25 volts! it gets very unhappy. Use a search engine for electronic circuits to guide you on.

http://www.radiolocman.com/

http://www.zen22142.zen.co.uk/schematics.htm

http://ourworld.compuserve.com/homepages/Bill_Bowden/

http://www.epanorama.net/schematicsforfree/index.php

Some samples

Hi Maddy..

Hope u dont mind me calling u maddy! You dont sound mad from your writing.

My grasp of electronics is up to cert level only.

Ok, Let me tell u the specification of the system and the working

Description : Water lilly plant fountain powered by a small 6v submersible pump attached at the underside of the liily plant. The system is supposed to run 24 hours a day. During daytime,the lily flower pump is powered by the solar panel. The solar panel also charges the lead acid battery ( 6V,5AH) and when the charge is full the solar controller circuit board which interfaces the solar panel and the pump and battery is cuts of the current to the battery charger. When sun goes down the controller will activate the battery to drive the pump. So in this manner the fountain runs 25 hours a day.

Just the other day, controller board gave up Smoke while i was moving the solar panel to determine the optimum location to capture max sunlight. Opened up and saw a smt resitor ( total fried ). Dont know the value! Got any idea how to determine the value? I have only one unit of this.

Suspecting that there may be other causes that caused the tiny resistor to smoke, i did in circuit resistance check almost on all suspect components, such as the two IRF Mosfets, silicon diodes M7, two glass envelop dioes ( maybe zener>) and a host of othe small resistors. Couldnt find any abnormality. Of course i understand that his may not be the best method, but is a quick check to determine gross failure of suspect. I suspect the MOSFETs too as DEL the CAT had sniffed it 8000 miles away!

The ciruit construction looked worst that a schoolboy soldering. Bought the system from China. Thats why i want to construct a controller of my own with my meagre knowledge from standard circuits and with the help of experts like u.

I wonder if there is some standard circuits which i can duplicate. BTW, what is SMPC.?

Thanks for your suggestions...

Hello again moo

No prob with maddy Interesting project you got there. Is it once off or landscaping for commercial purposes? Reason why i ask is effort in to rewards out. I started taking gimmicks apart some 25 years ago to see how and why they work...then started modifying the circuits. If you have the controller it might be quicker and easier to repair /modify it.

The burnt out resistor: at 6 volt supply I would guess your resistor value between 330 to 1k The footprint is a give away 1206 0805 ? 1/8 and 1/16 watt respectively Ohms law is a winner ha ha. However it could be on the 12v solar cct. Or a dump resistor for the solar panel. Burnt out probably means something shorted out elsewhere in the cct.

The MOSFETs: Vdss 40 Id 162A n channel probably used to switch the motor on cos of its current rating the solar panel can't deliver that kind of current. The other I'm not sure?!?

The best thing to do is try trace out the circuit to determine the path from the resistor to outer devices or take a digital pic and mail it me maybe a closeup might be enough to work it out.

If you suspect high amount of controllers required it would pay to design your own.

SMPS: Switch mode power supply

Regards

Hi there Maddy,

Thank you for your inputs. Initially the system sold was just a fountain without the rechargable battery. It just works as long as there is sunlight. I wanted the supplier to provide me a chargeable battery so that the system could work 24 hours to provide oxygen to my Koi fishes on this little pond in my house. And so the supplier provided me the battery and the controller.

Probably the value of the "fried" resisitor could be obtained whence the circuit has been traced!

I am still "hunting" for a reasonable circuit from the various websites you sent, and also trying to buy off the shelf controllers that might work for my system.

Joy to u

Moomoo

Hey moomoo, did you look at the data sheet, here's the pdf
It has tons of good circuit ideas.

Del

Hi Del,

I had a look at the PDF file. Yes there are a number of circuits. I need a circuit that would charge the battery during sunlight ( need at least 6 8 hrs min ) while powering up the dc pump. The circuit must also stop charging when battery voltage is reached ie 6V. And when sunset, the battery takes over to drive the pump the whole nite. Solar panel generates 12V on a good day ( I mean a hot day!) . AS i am not a competent designer, i have to really look all around the websites to get a near enough circuit.

Well If anyone out there has an available circuit onhand, that would be nice...

In the meantime, i have to try building one with my meagre knowldege, hope it works.

Thanks DEL the CAT...

Moomoo

Ok...maybe I can draw up a simple, but good, circuit for you, (with explanation of how it works) but some questions first.

1. If you connect the solar panel straight onto the pump does it run it ok, or do you think the voltage from the solar panel needs limiting?
2. Do you have any details on the battery so we can check charge details?
3. Can I assume you have a digital multimeter to set up the circuit.
4. Have you got access to components suppliers?

Del

Hi Del,

Thanks alot indeed.., thats very kind of you..

To answer your questions..

1. The pump is rated 6V and yes, if connected directly to the panel , it runs well. The rating of the solar panel at the back is written as Pmax 6W and Voc 10V.

2. The battery is a lead acid accumulator type, similar to the motorbike battery. with a rating of 6v, 5.0AH.

3. yes, I have a fluke digital desktop multimeter to setup the circuit.

4. Yes, I have also access to some local component suppliers. Worst case, i can request RS or Farnell to get for me.

moomoo

Is the battery a sealed gel type? Is there a manufacturers name & model number?
One more question...With the solar panel running the pump in bright sunshine what is the voltage reading across the pump?

I should be able to come up with some sensible circuit values...with this info.

Del

Hi Moomoo,
Here is a simple single rate charger.

The Voltage at 'V' is set up with the battery removed, it is adjusted by the variable resistor (potentiometer or 'pot' as it's generally known) .
I checked a battery manufacturers website and they quote a float voltage per cell of about 2.3v thus the voltage at V is set to 6.9 volts.
They quote the maximum charging voltage as 2.4v per cell, this would give a voltage at V of 7.2v but there would be some chance of overcharging.

My guess is that you'll be fine setting it to 7.2v.

Once it's set you can reconnect the battery.
The diode is a Schotty diode, these have a low voltage drop (about 0.25v where an ordinary diode will waste 0.7v) it is there to stop the power from the solar cell going straight to the battery while it (the solar cell) is running the pump.

I don't know if the other diode is needed to stop current leaking back from the battery through the solar cell at night (shown blue in the diagram) maybe someone else can tell us?

Please fellow CR4ers don't tell me how 'over simple' this circuit is... it will hopefully do the job...if not we can add complexity later...it is hopefully buildable by someone with not much experience.

The connections on the LM317T are input on the left, output on the right and the 'adjust' pin on the bottom, refer to the previous link for the pin location. The other resistor is 240Ω (the Ω symbol is a bit scribbley...it's not easy to use a graphics tablet with paws)

I hope this makes sense.
Del

(Ideally you would build a 2 rate charger which would charge at maximum current upto a specific point and then reverte to a trickle charge, but this gets more complicated...)

Hi Del,

The battery dimension is 10cm x 7cm x 4.5 cm , manufactrer name J-Power , I think model number is FM650, and it is a sealed Lead acid battery.Full name of manufacturer is Jin Power Battery Co. Ltd. China.

Also solar panel open circuit voltage is about 10V at bright sunlight. I havent tried connected directly for fear that it might burn out the pump ( rated at 6V).

If u need any more details , let me know, i will furnish as much details u require.

thanks

moomoo

If there is any other measurements u want me to carry out or details let me know.

I'm now confused.

I havent tried connected directly for fear that it might burn out the pump ( rated at 6V).

Your answer 1 in post #9 contradicts this statement, but never mind.
10v certainly won't burn out the pump unless it was run for a loooong time, so it's fine for a quick test.
If you do this test it will help provide more info and I can tweak the circuit to run the pump from the regulated voltage too if it's necessary.
We may need to add an extra capacitor across the solar cells..I dunno what the output impedance of a solar cell is, but that's half the fun of electronics. The capacitor would be there to provide a stable supply for the regulator.

Circuits seldom work perfectly first time, software never does.

Del

Hi Del,

Sorry for the confusion. What i meant was the pump works well when connected to a 6V supply( external PS). I did that earlier because i want to rule out the possibiliity that the pump is not working. I also checked separately the solar panel and it gave an ouput of 10V under midday sun. But after going through the controller this 10V is attenuated to 2v. the output of the controller should be around 6V. So the board must be bad.

Based on your suggestion, I connected the pump directly to the solar panel and the vdrop across the pump was around 9.6V. I guess the .4v drop is across the 10 ft cable connected to the pump.

Is there a way for me to measure the output impedance of the solar cell from the spec of the solar cell. Can i calc. using the spec available as follows..?

The solar panel is rated 9V with 6W, so using V squared/R formula, can we calculate R?. In this case it works out to be 9x9/6 = 4.5 ohms.? Is this the right way?

thanks.

Moomoo

Hi Del,

Can i test the circuit using a stabilised PS as the input? instead of the solar panel, because i dont want to cause any silly mistakes to spoil the panel during evaluation.

By the way, the current controler has a comparator ic LM393, i guess this is for autostart the charging process when battery voltage gets low and stopping charging when battery is fully charged.

moomoo

Yes you can set it up on a power supply.
The comparator is the next stage if we wanted to make it a two stage charge based on a a current limit to switch from fast charge to trickle.
We can do that later...I always like to start simple and build up...got to go play golf...

Del

Typing 'Jpower FM650' into google brings up the J power website...one more click gives the data sheet There you can see the charging voltages.

To run the battery and pump off the same voltage just remove that top wire and diodes from the diagram. Give it a try, the next stage of complexity is quite a big jump, so it's worth giving the simple things a go first...simplicity often also equates to reliability.

The potential problems/question

The LM317 may get hot and shut down (it is internally protected).
This is easilly tested (with a finger) While driving just the pump we can assume it will be dropping the volts from about 9 to 6 which is 3volts at 0.5 A this is only 1.5W so it should be ok...
Is that 3v available enough to allow the LM317 to run propperly? Hmm the spec sheet says it needs 4v input to output differential so it may be a bit tight. It will probably still work but the output voltage may drop below the set value....this won't do any harm as the regulator is there to stop over volts on the battery.

I'd still give it a try...or ask that nice Mr Google for a low dropout voltage adjustable voltage regulator....which gives us this one LT1086CT, this would be better as it will be wasteing less power, (the connections are just the same).

Del

Hi Del,

Currently the battery output is 4.2 V, can i start charging at this voltage once i complete the circuit. I have all the components except the Diodes. Or do i have to wait for the charge to go down flat! and then charge. Please advise.

Don't wait...just go for it.

Your battery is more than flat already (assuming a 6 volt lead acid battery!) and unless it is a leisure battery (that may be deeply discharged without damage), will be damaged by being so deeply discharged!! That is, its life will be severely shortened. Design in that the battery cannot be discharged below the correct point if you can....

Other (rechargeable!) cell types also do not like being discharged below around 1 volt per cell as an average rule either........! Naturally it is dependant upon the cell type, but take 1 volt as being not too far from the truth!!! (for lead acid types take 2.1 volts per cell as a safe low other than of course "leisure" LA batteries, as mentioned already.)

Furthermore, in any battery of cells, one cell will be discharged first and this one gets reversed polarized by the other cells which damages that one cell even further, it is similar to charging it with the wrong polarity!!!

For anyone reading this, if you have a battery made up of single separate cells, do yourself a favor and always only use chargers that charge each battery separately and do not "over" discharge them first!

Only NICADS need an occasional deep discharge to bring back full capacity if recharged when still not "empty", but a good well designed modern charger, discharges each one first automatically anyway and then the so called "memory" effect does not take place......