Improve this solar controller?

MikeMl · Jan 16, 2015

EccentricDyslexic said:
Thanks! I notice you are using a TIP32c not a TIP30c, are they interchangeable? i only have tip30c handy.

Cheers!

Steve

Exercise for the student: Down load and study both data sheets. What is the difference?

EccentricDyslexic · Jan 16, 2015

Thanks, Mike. I did look at the data sheets and it looks like the tip30c has minus voltages instead of positive on tip32c, but I don't understand how to take account of this in the circuit.

I have built the circuit with the tip30c, but it doesn't work as it should, the tip30c draws a fair current and gets warm below the threshold where it should start to trigger.
Will look into minus v a bit more to see if I can figure it out though.

Cheers

Steve

EccentricDyslexic · Jan 17, 2015

Not getting anywhere. I must have had a duff data sheet with regards to negative voltages. I think the difference is to do with how much drive is needed to turn them on?

I cant find tip32c or tip30c on ltspice, where did you get your tip32c and the lt431 models from?

cheers

steve

killivolt · Jan 17, 2015

Try here (Yahoo Groups)

They had some extended libraries that other people have modeled.

Good Hunting.

kv

killivolt · Jan 17, 2015

Here... I found this .zip I understand there are 8 to choose from. Not sure how to help you pick which one.

Thats just a test not the actual Model

killivolt · Jan 17, 2015

Not sure if these will work or not.

EccentricDyslexic · Jan 17, 2015

Thanks kv, hope to get to play with these in the morning.

Cheers all

Steve

EccentricDyslexic · Jan 18, 2015

I am thinking I will buy tip32c and be done with it lol

If I make mikeml revised circuit, I don't want the whole of the battery's current shunted to ground as it will blow the circuit won't it? So I need to get rid of about 5w of power(the solar panels capacity). Am I right at in thinking I need a 40ohm 5w min resister will do ok?

The other. Thing is, can I use same circuit to control a 20w panel? But with a large resister power obviously?

Steve

MikeMl · Jan 18, 2015

My reading of the two data sheets is that they are interchangeable for this application.

TIP30
TIP32

Are you sure you wired it up right?

killivolt · Jan 18, 2015

MikeMl said:
My reading of the two data sheets is that they are interchangeable for this application.

TIP30
TIP32

Are you sure you wired it up right?

View attachment 90279 View attachment 90280

Hi, Mike. Can you upload that Shunt Regulator file. I'd like to play with some of the values.

I've been thinking about charging a small battery I have with a solar panel.

kv

EccentricDyslexic · Jan 18, 2015

great, got it working, yes i had wired the e and c backwards! works a charm, but gets very hot on the test bench power supply trying to drain far more than it will in practice.

silly newbie question again- rather than let the tip30c take all the heat from the 14ah battery, if i wire it just to the solar panel side of the blocking diode, then only the solar panel's current will be shunted at voltages higher than 14.2v? this is correct isn't it? in practice this will only happen when the battery is full and its a sunny day.

Thanks!

Steve

MikeMl · Jan 18, 2015

I left out the diode because it is not needed. If a 6cell SLA battery has been sitting unloaded for more than a few hours, its terminal voltage will be <13.6V. If you connect that to the shunt regulator which turns on at 14.2V, then only the four or five hundred uA will leak from the battery. The diode will not have any appreciable effect on the power dissipated in the power transistor.

If your test bench power supply has a current-limit knob, set the max current to ~300mA, set the open-circuit voltage to ~15V, and then hook it to the shunt regulator. The power transistor and its small heatsink should get hot to the touch, but not hot enough to burn your hand. Under this condition, the power transistor would be dissipating P=IE = 0.3*14.2 = 4.2W.

If your bench supply puts out 3A, then the power transistor would be dissipating 42W, and it will brand you...

ronsimpson · Jan 18, 2015

The last time I needed a 12 volt high wattage load (with out being branded) I used a car headlight. (turning signal light if you want a smaller wattage load)
I used a tail light in my tractor battery charger.
42 watts in a transistor...........probably will burn out.

Nigel Goodwin · Jan 19, 2015

ronsimpson said:
42 watts in a transistor...........probably will burn out.

No one has suggested any such dissipation, read the thread again

EccentricDyslexic · Jan 19, 2015

If this is connected directly to a 7ah 12v what kind of wattage will be dissipated? I mean if the solar panel has charged the battry to14.2.

jjw · Jan 19, 2015

EccentricDyslexic said:
If this is connected directly to a 7ah 12v what kind of wattage will be dissipated? I mean if the solar panel has charged the battry to14.2.

P=U×I = 14.2× current of the panel

jjw · Jan 19, 2015

MikeMl said:
I left out the diode because it is not needed.
....

Do all panels have the diode inbuilt ?
If not, then the battery drains trough the panel, when the panel is in the shadow.

Nigel Goodwin · Jan 19, 2015

jjw said:
Do all panels have the diode inbuilt ?
If not, then the battery drains trough the panel, when the panel is in the shadow.

Doesn't matter if the panel has one built-in or not - you can't leave it out as the dummy load is then draining the battery rather than stopping it overcharging.

EccentricDyslexic · Jan 19, 2015

jjw said:
P=U×I = 14.2× current of the panel

Not the current of the battry? 7ah?

Steve

jjw · Jan 19, 2015

EccentricDyslexic said:
Not the current of the battry? 7ah?

Steve

The current which the panel provides at 14.2V

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