Solar Panel Voltage Regulator

Precisely.

Cheers, James Arthur

I knew who it was, I just didn't want to broadcast him on the internet.

And you *could* home-brew a charger. Just set it for 2.35V/cell, temp-compensated, and terminate charge when the current drops to

10-20% of full.

Hysteresis should then inhibit charging until the voltage drops below a certain threshold, but without measurement or data, I'm not sure what to recommend.

A switch that lets Harry equalize the battery (2.50 V/cell) twice a year or so would extend the battery's life. (Or shorten it, if Harry forgets and leaves the switch on!)

Sounds plausible. A swamp cooler isn't much more than a fan, load-wise.

Works like a bandit in low humidity. It's a great solution if you're in a desert with water to burn, and a waste of electricity in humid areas where water's aplenty.

(They used swamp coolers in the San Fernando Valley when I was a kid, now banned because of their high water usage.)

"Water, water every where, nor any drop to drink."

Cheers, James Arthur

MPPT helps reduce cell heating, which may prolong their useful life.

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Confusion huh.

NT

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e lead acid cell tempco per cell is -2mV/oC, his macro-threshold gets divid ed by 12, will be hard to be off a few hundred mV cell from the 2.4V full c harge and it won't amount to a hill of beans. You think the cheap controlle r is temperature compensated? Really? Show me the thermocouple probe that c omes with them.

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Battery University is about as credible as Trump University, i.e. credibili ty rating of zero. Things have changed considerably, there are several vari eties of battery construction and operation out there for solar. The best p ractice is to comply with the specifications of the manufacturer whose batt ery you're using. Looks like the new most common tempco is -5mV/cell, and l ike I said, the real solar installations have controllers with RTS= Remot e Temperature Sensors attached to a representative battery in the pack. The n depending on battery type, the per cell full charge nominal voltage may b e as high as 2.6V, but most are 2.4V.

ordinately long time to charge the batteries, if not, it makes no differenc e whether you're operating on the MPP or not. Since as things stand now the panel overcharges and ruins the battery, there is a good chance the MPP is doubly a non-consideration.

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The lead acid cell tempco per cell is -2mV/oC, his macro-threshold gets div ided by 12, will be hard to be off a few hundred mV cell from the 2.4V full charge and it won't amount to a hill of beans. You think the cheap control ler is temperature compensated? Really? Show me the thermocouple probe that comes with them.

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If you have a more accurate graph or a specific correction, a link would be more useful than a random ad hominem.

construction and operation out there for solar. The best practice is to com ply with the specifications of the manufacturer whose battery you're using. Looks like the new most common tempco is -5mV/cell, and like I said, the r eal solar installations have controllers with RTS= Remote Temperature Sen sors attached to a representative battery in the pack. Then depending on ba ttery type, the per cell full charge nominal voltage may be as high as 2.6V , but most are 2.4V.

PowerSonic's technical info is quite good, but I'm not sure it fully applie s to El Raton's car batteries. PowerSonic shows a dual-rate charger schemati c using jelly-bean parts that Bill could easily get.

Manual-Lo.pdf

I tried finding car-battery technical info on Johnson Controls' site, but gave up.

Cheers, James Arthur

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y construction and operation out there for solar. The best practice is to c omply with the specifications of the manufacturer whose battery you're usin g. Looks like the new most common tempco is -5mV/cell, and like I said, the real solar installations have controllers with RTS= Remote Temperature S ensors attached to a representative battery in the pack. Then depending on battery type, the per cell full charge nominal voltage may be as high as 2.

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HomeDepot sells this for $16.47, should be on the shelf in most stores- dam med thing does hardly anything:

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They also carry a 250AH 12V SLA for $800...WTF???

Maximum power point tracker.

Clifford Heath.

What's an MPPT?

Hul

snipped-for-privacy@yahoo.com wrote:

Doesn't change the charge control algorithm, but you might want to consider a shunt regulator. If you have something to do with the excess power, like bank it in a water tank for heat recovery at night. If you ever want to add wind power, wind generators don't like to be unloaded in high wind. Local radio repeaters had several wind generators disintegrate before they switched to shunt regulation.

The desert rat has 10 of those 180 watt panels (1.8kW total) which is more than my electric bill living in the city. He has four 12 volt batteries at

190AH each or 380AH at 24 volts. The swamp cooler draws 1.3 amps at 120 or 156 watts which sounds low to me but not sure how he measured that. But he has plans to distill water from his well which requires lots of heat. Not sure of the energy requirement for that, but the rat is a physicist, so he can probably do the math. He tried one of those cheap solar panel regulators from wherever and it failed, so he doesn't trust them. .

I assume he'll use solar power to distill, it would make no sense to use electricity for that.

NT

Did you see the PowerSonic literature I linked? It has a schematic for a decent lead-acid charge controller built from a (boosted) LM317, page 17.

(It looks a little over-complicated compared to its description, might want to scrutinize it.)

Cheers, James Arthur

I took a look at it but it's not real clear. I guess the diode D2 (1N4148) does the temp compensation. And resistor R3 would be a fairly low value of maybe 140 milliohms for a current of 5 amps. And what about the temp compensation for the drop across D1 which is in series with the battery? Does D2 take care of that also? And D3 and R6 are confusing. It looks like if you have enough current to turn on Q2, the voltage on R6 will rise which raises the output voltage. So, yes, it is complicated. If it were me in the desert, I would make the system reliable first, simple second, and efficient last.

applications like that seem ideally suited to a heat pump, but yeah direct solar may make more sense.

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Concentrated solar is far cheaper than a heat pump running on PV power.

NT

Yes.

Yes.

Yes.

Correct. That's how a heavy current demand selects "topping" voltage. When the battery's full & current falls, the charger falls back to "float" voltage.

Here's how to understand it-- The charger shifts between topping voltage and float voltage based on the battery's current draw.

When current is high (battery empty), Q1 conducts, which raises the output voltage by switching R6 in parallel with R1.

When output current drops below i=isw (battery full), Q1 cuts off, R6 is disconnected, and Vfloat is selected.

R4 turns the LM317's adj terminal into a current source, passing 1mA through temp. compensation diode D2, and resistor R5. That creates ~1V of drop, with D2's mV/C. The LM317's reference voltage is now effectively a temperature-compensated 2.5V, and Vfloat ~= 2.5V multiplied by divider (RS+R1)/(R1).

Overall current limit is set by R3-Q2, as you described.

Cheers, James Arthur

Maybe for now- and care to explain how you use "concentrated" solar to cool?

That's for line operation, not solar, and you're not going to get an Energy Star rating for it either.