solar charging regulators - Electronic Circuits Projects Diagrams Free

Thunderchild · 15th March 2009, 03:11 PM

I bought a couple of panels on ebay that are 20 watts and listed as 12 volts but they are actually 17.5, now I'm aware that i will need more than 12 volts to charge lead-acid batteries but surely 17.5 is a lot. do charging controllers work with switch mode cicuitry ? so that the voltage can be dropped and the amperage increaased a little ? or am I best just using a proper smps to do it ?

ericgibbs · 15th March 2009, 03:59 PM

Quote:

Originally Posted by Thunderchild

I bought a couple of panels on ebay that are 20 watts and listed as 12 volts but they are actually 17.5, now I'm aware that i will need more than 12 volts to charge lead-acid batteries but surely 17.5 is a lot. do charging controllers work with switch mode cicuitry ? so that the voltage can be dropped and the amperage increaased a little ? or am I best just using a proper smps to do it ?

hi TC,
Was that the off load voltage.?
Solar panels have a highish output resistance, about 5R or so.

So at 1amp you may only get ~12.5v

You may require a reverse blocking diode if the panel is connected to a battery.

Thunderchild · 15th March 2009, 04:12 PM

well its 21+ volts no load and on the back says 17.5 volts, if I count up the cells and calculate them all in series @ 0.5 V each (36 cells X 0.5 V) its 18 volts so thats about right

ericgibbs · 15th March 2009, 04:17 PM

Quote:

Originally Posted by Thunderchild

well its 21+ volts no load and on the back says 17.5 volts, if I count up the cells and calculate them all in series @ 0.5 V each (36 cells X 0.5 V) its 18 volts so thats about right

You can charge SLA 12V batteries at 13.8V or 14V for cyclic use.

Have you an ebay link to panels.?

Thunderchild · 15th March 2009, 04:33 PM

Brand New 20 Watt Solar Panel on eBay, also, Solar Panels, Gadgets, Consumer Electronics (end time 14-Mar-09 15:23:40 GMT)

on the back of the panel it says 17.5 volts and 1.15 amp well I got up to 1.25 amps shor circuit and 21.5 volts open circuit

HarveyH42 · 15th March 2009, 04:33 PM

A charge controller is a good investment, unless you get free batteries. A 5 amp controller cost around $20, an new 10 AH battery is around $40...

ericgibbs · 15th March 2009, 04:55 PM

Quote:

Originally Posted by Thunderchild

Brand New 20 Watt Solar Panel on eBay, also, Solar Panels, Gadgets, Consumer Electronics (end time 14-Mar-09 15:23:40 GMT)

on the back of the panel it says 17.5 volts and 1.15 amp well I got up to 1.25 amps shor circuit and 21.5 volts open circuit

hi,
As Harvey says a charge controller is required.

from your link

Code:

Electrical Specs:
Max Power: 20WP
Open Circuit Voltage (V): 21.88 + 2
Short Circuit Current (A): 2.49 + 0.4
Max. Power voltage (V): 17.64 + 2
Max. Power Current (A): 1.135

nickelflippr · 15th March 2009, 05:12 PM

Take a look at how the RV industry handles charging lead acid battery's. For instance, the Progressive Dynamics Converter/Charger. Using a 14V-14.1 is a little low for flooded lead acid type, and is usually the setpoint for gel and maybe some AGM type of batteries. Also its good if a charge controller has an equalizer cycle, if the battery's are flooded lead acid type, either manual or automatic.

Going with a lower end solar charge controller, like the Morningstar Sunsaver/Sunkeeper, are usually just an analog pwm device. The upper end controllers out there use MPPT, and are of the programmable type.

Thunderchild · 15th March 2009, 05:42 PM

ok so do these controllers just dissipate the 17.5-12.5ish volts or convert it reducing voltage and oncreasing amps ?

nickelflippr · 15th March 2009, 07:24 PM

Quote:

Originally Posted by Thunderchild

ok so do these controllers just dissipate the 17.5-12.5ish volts or convert it reducing voltage and oncreasing amps ?

The impression I get is that you would lose some efficiency with a straight PWM controller (depending on temperature, overcast conditions, etc.). What kind of voodo electronics goes on, that makes MPPT better, haven't a clue. The MPPT thing probably just not worth the effort or expense for a small solar array?

Thunderchild · 15th March 2009, 07:32 PM

what is MPPT ?

I'm guessing that I do not need straight 17.5 volts to charge a 12 volt battery and so there being a good 25 % over voltage a decent switch mode controller will conver the 4-5 volts extra into extra current making it a bit more efficient. ok so I can't connect the battery straight to a smps as it still needs to be "charge controlled" what sort of charge controlling goes on ?

ericgibbs · 15th March 2009, 07:43 PM

Quote:

Originally Posted by Thunderchild

what is MPPT ?

I'm guessing that I do not need straight 17.5 volts to charge a 12 volt battery and so there being a good 25 % over voltage a decent switch mode controller will conver the 4-5 volts extra into extra current making it a bit more efficient. ok so I can't connect the battery straight to a smps as it still needs to be "charge controlled" what sort of charge controlling goes on ?

hi TC,
If there isnt an internal blocking diode, then an external shottky will lose another 0.45V.
You could use a shunt reg but these are wasteful.

There maybe some decent controller designs on the web.

I would be interested on seeing your results when you have it running.

Thunderchild · 15th March 2009, 07:53 PM

well the panels came with a 10 amp standard diode (I suppose just for the sake of it) I'd prefer to used a skottky one.

If I'm to build my own I need to know the "logic" of charging batteries, I'm sure it can be done with comparators and possibly some digital logic (ok ok a pic can do the lot but my pic skills go as far as knowing the wonders they could do for me if I knew how to program them).

As for the diode well, if i was designing my own I'd be using the panel to power the SMPS first so that surely would act as a block anyway from the battery discharging into the panel. So I'd step down the voltage hopefully increasing the current by about 20 % and charge the battery via the appropriate "logic" which as far as i know is when "x" voltage is reached its charged but I'm sure i need to know more than that....

ericgibbs · 15th March 2009, 08:02 PM

Quote:

Originally Posted by Thunderchild

well the panels came with a 10 amp standard diode (I suppose just for the sake of it) I'd prefer to used a skottky one.

If I'm to build my own I need to know the "logic" of charging batteries, I'm sure it can be done with comparators and possibly some digital logic (ok ok a pic can do the lot but my pic skills go as far as knowing the wonders they could do for me if I knew how to program them).

As for the diode well, if i was designing my own I'd be using the panel to power the SMPS first so that surely would act as a block anyway from the battery discharging into the panel. So I'd step down the voltage hopefully increasing the current by about 20 % and charge the battery via the appropriate "logic" which as far as i know is when "x" voltage is reached its charged but I'm sure i need to know more than that....

hi,
Do you need any help with a charger design, I have used 12V SLA 7AH and 20AH battery chargers on a number of projects.?

nickelflippr · 15th March 2009, 08:44 PM

TC said:

Quote:

What is MPPT?

I believe it is what you are trying to describe, in that excess panel to controller charge voltage is turned into increased current. Maximum Power Point Tracking Charge Controller

Quote:

well the panels came with a 10 amp standard diode (I suppose just for the sake of it) I'd prefer to used a skottky one.

You are correct in thinking that a properly designed charge controller would do away with the external panel mount diode.

ecgibbs said:

Quote:

hi,
Do you need any help with a charger design, I have used 12V SLA 7AH and 20AH battery chargers on a number of projects.?

Curious about a programmable type myself, and would start another thread if TC has no interest.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar
Title	Starter	Forum	Replies	Latest
Charging EEE pc from a solar panel?	things	General Electronics Chat	3	5th December 2008 05:47 PM
Solar charging	jaycool1995	Electronic Projects Design/Ideas/Reviews	7	19th August 2008 05:13 AM
charging NiCd from solar cells	mettam	General Electronics Chat	21	1st October 2006 04:14 AM
Charging a 12v battery with Solar panel..	barrymons	Electronic Projects Design/Ideas/Reviews	11	21st April 2006 01:44 AM
Charging System of Solar Car	devonsc	General Electronics Chat	3	21st December 2004 05:43 AM

15th March 2009, 03:11 PM	#1
Thunderchild	solar charging regulators I bought a couple of panels on ebay that are 20 watts and listed as 12 volts but they are actually 17.5, now I'm aware that i will need more than 12 volts to charge lead-acid batteries but surely 17.5 is a lot. do charging controllers work with switch mode cicuitry ? so that the voltage can be dropped and the amperage increaased a little ? or am I best just using a proper smps to do it ? __________________ I AM the exeption that disproves the rule in many ways but the rules still apply (unfortunately) www.simonsphotography.org.uk/ - My other hobby www.rushdenrotaract.org.uk/ - make a difference and have fun ! Never buy "Trust" products, all mine broke !!!

15th March 2009, 04:12 PM	#3
Thunderchild	well its 21+ volts no load and on the back says 17.5 volts, if I count up the cells and calculate them all in series @ 0.5 V each (36 cells X 0.5 V) its 18 volts so thats about right __________________ I AM the exeption that disproves the rule in many ways but the rules still apply (unfortunately) www.simonsphotography.org.uk/ - My other hobby www.rushdenrotaract.org.uk/ - make a difference and have fun ! Never buy "Trust" products, all mine broke !!!

15th March 2009, 04:33 PM	#5
Thunderchild	Brand New 20 Watt Solar Panel on eBay, also, Solar Panels, Gadgets, Consumer Electronics (end time 14-Mar-09 15:23:40 GMT) on the back of the panel it says 17.5 volts and 1.15 amp well I got up to 1.25 amps shor circuit and 21.5 volts open circuit __________________ I AM the exeption that disproves the rule in many ways but the rules still apply (unfortunately) www.simonsphotography.org.uk/ - My other hobby www.rushdenrotaract.org.uk/ - make a difference and have fun ! Never buy "Trust" products, all mine broke !!!

15th March 2009, 04:33 PM	#6
HarveyH42	A charge controller is a good investment, unless you get free batteries. A 5 amp controller cost around $20, an new 10 AH battery is around $40...

15th March 2009, 05:12 PM	#8
nickelflippr	Take a look at how the RV industry handles charging lead acid battery's. For instance, the Progressive Dynamics Converter/Charger. Using a 14V-14.1 is a little low for flooded lead acid type, and is usually the setpoint for gel and maybe some AGM type of batteries. Also its good if a charge controller has an equalizer cycle, if the battery's are flooded lead acid type, either manual or automatic. Going with a lower end solar charge controller, like the Morningstar Sunsaver/Sunkeeper, are usually just an analog pwm device. The upper end controllers out there use MPPT, and are of the programmable type. Last edited by nickelflippr; 15th March 2009 at 05:17 PM. Reason: qualify equalizing charge to lead acid type

15th March 2009, 05:42 PM	#9
Thunderchild	ok so do these controllers just dissipate the 17.5-12.5ish volts or convert it reducing voltage and oncreasing amps ? __________________ I AM the exeption that disproves the rule in many ways but the rules still apply (unfortunately) www.simonsphotography.org.uk/ - My other hobby www.rushdenrotaract.org.uk/ - make a difference and have fun ! Never buy "Trust" products, all mine broke !!!

15th March 2009, 07:32 PM	#11
Thunderchild	what is MPPT ? I'm guessing that I do not need straight 17.5 volts to charge a 12 volt battery and so there being a good 25 % over voltage a decent switch mode controller will conver the 4-5 volts extra into extra current making it a bit more efficient. ok so I can't connect the battery straight to a smps as it still needs to be "charge controlled" what sort of charge controlling goes on ? __________________ I AM the exeption that disproves the rule in many ways but the rules still apply (unfortunately) www.simonsphotography.org.uk/ - My other hobby www.rushdenrotaract.org.uk/ - make a difference and have fun ! Never buy "Trust" products, all mine broke !!!

15th March 2009, 07:53 PM	#13
Thunderchild	well the panels came with a 10 amp standard diode (I suppose just for the sake of it) I'd prefer to used a skottky one. If I'm to build my own I need to know the "logic" of charging batteries, I'm sure it can be done with comparators and possibly some digital logic (ok ok a pic can do the lot but my pic skills go as far as knowing the wonders they could do for me if I knew how to program them). As for the diode well, if i was designing my own I'd be using the panel to power the SMPS first so that surely would act as a block anyway from the battery discharging into the panel. So I'd step down the voltage hopefully increasing the current by about 20 % and charge the battery via the appropriate "logic" which as far as i know is when "x" voltage is reached its charged but I'm sure i need to know more than that.... __________________ I AM the exeption that disproves the rule in many ways but the rules still apply (unfortunately) www.simonsphotography.org.uk/ - My other hobby www.rushdenrotaract.org.uk/ - make a difference and have fun ! Never buy "Trust" products, all mine broke !!!