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Battery charger with solar panel

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  Battery charger with solar panel gm <notmy@mail.com> - 2017-02-04 21:41 +0100
    Re: Battery charger with solar panel Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 13:49 -0700
    Re: Battery charger with solar panel Baron <baron@linuxmaniac.net> - 2017-02-04 21:39 +0000
    Re: Battery charger with solar panel rickman <gnuarm@gmail.com> - 2017-02-04 17:05 -0500
    Re: Battery charger with solar panel mike <ham789@netzero.net> - 2017-02-04 14:42 -0800
      Re: Battery charger with solar panel Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 16:00 -0700
        Re: Battery charger with solar panel mike <ham789@netzero.net> - 2017-02-04 16:35 -0800
          Re: Battery charger with solar panel Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 17:38 -0700
          Re: Battery charger with solar panel rickman <gnuarm@gmail.com> - 2017-02-04 19:42 -0500
            Re: Battery charger with solar panel Jasen Betts <jasen@xnet.co.nz> - 2017-02-05 04:22 +0000
              Re: Battery charger with solar panel mike <ham789@netzero.net> - 2017-02-04 23:26 -0800
                Re: Battery charger with solar panel rickman <gnuarm@gmail.com> - 2017-02-06 19:55 -0500
              Re: Battery charger with solar panel rickman <gnuarm@gmail.com> - 2017-02-06 19:54 -0500
                Re: Battery charger with solar panel Jasen Betts <jasen@xnet.co.nz> - 2017-02-07 03:55 +0000
                  Re: Battery charger with solar panel rickman <gnuarm@gmail.com> - 2017-02-06 23:41 -0500
          Re: Battery charger with solar panel Jeff Liebermann <jeffl@cruzio.com> - 2017-02-04 18:17 -0800
            Re: Battery charger with solar panel rickman <gnuarm@gmail.com> - 2017-02-04 22:36 -0500
              Re: Battery charger with solar panel Jeff Liebermann <jeffl@cruzio.com> - 2017-02-05 01:03 -0800
    Re: Battery charger with solar panel Don Y <blockedofcourse@foo.invalid> - 2017-02-04 22:02 -0700
    Re: Battery charger with solar panel dakupoto@gmail.com - 2017-02-04 22:25 -0800
    Re: Battery charger with solar panel boB <boB@theresnoplacelikehome.com> - 2017-02-05 16:38 -0800

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#446149 — Battery charger with solar panel

Hi to all.

Did someone try this approach:
http://cds.linear.com/image/314_circuit_1.jpg

when designing solar charger ?
Power consumption will be under 75Wh per day..

Other infos:
- solar panel 15W
- battery 12V / 7Ah

GM

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#446151

On Sat, 4 Feb 2017 21:41:51 +0100, gm <notmy@mail.com> wrote:

>Hi to all.
>
>Did someone try this approach:
>http://cds.linear.com/image/314_circuit_1.jpg
>
>when designing solar charger ?
>Power consumption will be under 75Wh per day..
>
>Other infos:
>- solar panel 15W
>- battery 12V / 7Ah
>
>GM

Easy enough to do with a comparator, see

"OverAndReverseVoltageProtection.pdf"

on the S.E.D/Schematics page of my website.
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#446162

gm prodded the keyboard with:

> Hi to all.
> 
> Did someone try this approach:
> http://cds.linear.com/image/314_circuit_1.jpg
> 
> when designing solar charger ?
> Power consumption will be under 75Wh per day..
> 
> Other infos:
> - solar panel 15W
> - battery 12V / 7Ah
> 
> GM

I've done exactly that using an LT8490 and the circuit on the data
sheet. My panel is a 300W 42V 8.5A. feeding two 110 Ah wet cell
leisure batteries.

-- 
Best Regards:
                      Baron.

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#446166

On 2/4/2017 3:41 PM, gm wrote:
> Hi to all.
>
> Did someone try this approach:
> http://cds.linear.com/image/314_circuit_1.jpg
>
> when designing solar charger ?
> Power consumption will be under 75Wh per day..
>
> Other infos:
> - solar panel 15W
> - battery 12V / 7Ah

Wouldn't that be a pretty inefficient design?  The panel output voltage 
is dragged down by the shunt regulator wasting power both in the solar 
panel and the shunt regulator.  You can find any number of converter 
circuits on eBay and elsewhere for cheap.  Or you can build your own 
like Baron.  The LT8490 looks like a pretty Cadillac chip at over $15.

I found one guy who is already making boards and sharing the design.

http://www.mictronics.de/tag/lt8490/

-- 

Rick C

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#446170

On 2/4/2017 12:41 PM, gm wrote:
> Hi to all.
>
> Did someone try this approach:
> http://cds.linear.com/image/314_circuit_1.jpg
>
> when designing solar charger ?
> Power consumption will be under 75Wh per day..
>
> Other infos:
> - solar panel 15W
> - battery 12V / 7Ah
>
> GM
The devil is in the details.

You seem to be focused on the isolation diode loss.

Are you in a location where you can reliably
get 75Wh/day out of a 15W panel in winter?

Depending on the time of load, you may be running
the battery flat every day.  Not a good idea.

Charge efficiency is not 100%.

Overdischarge management?

Overcharge management?

Depending on available insolation, time of load
and the characteristics of your panel,
you may be better off with a way bigger battery,
way bigger panel and a MPPT controller.
The MPPT is quite simple to build with a
microcontroller.  It also solves all your
charge management issues.

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#446175

On Sat, 04 Feb 2017 14:42:31 -0800, mike <ham789@netzero.net> wrote:

>On 2/4/2017 12:41 PM, gm wrote:
>> Hi to all.
>>
>> Did someone try this approach:
>> http://cds.linear.com/image/314_circuit_1.jpg
>>
>> when designing solar charger ?
>> Power consumption will be under 75Wh per day..
>>
>> Other infos:
>> - solar panel 15W
>> - battery 12V / 7Ah
>>
>> GM
>The devil is in the details.
>
>You seem to be focused on the isolation diode loss.
>
>Are you in a location where you can reliably
>get 75Wh/day out of a 15W panel in winter?
>
>Depending on the time of load, you may be running
>the battery flat every day.  Not a good idea.
>
>Charge efficiency is not 100%.
>
>Overdischarge management?
>
>Overcharge management?
>
>Depending on available insolation, time of load
>and the characteristics of your panel,
>you may be better off with a way bigger battery,
>way bigger panel and a MPPT controller.
>The MPPT is quite simple to build with a
>microcontroller.  It also solves all your
>charge management issues.

Looks like the ideal solution to keeping my pick-em-up truck battery
charged, since I drive it only every few weeks.

And in Arizona we certainly don't lack for sunshine ;-)
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#446192

On 2/4/2017 3:00 PM, Jim Thompson wrote:
> On Sat, 04 Feb 2017 14:42:31 -0800, mike <ham789@netzero.net> wrote:
>
>> On 2/4/2017 12:41 PM, gm wrote:
>>> Hi to all.
>>>
>>> Did someone try this approach:
>>> http://cds.linear.com/image/314_circuit_1.jpg
>>>
>>> when designing solar charger ?
>>> Power consumption will be under 75Wh per day..
>>>
>>> Other infos:
>>> - solar panel 15W
>>> - battery 12V / 7Ah
>>>
>>> GM
>> The devil is in the details.
>>
>> You seem to be focused on the isolation diode loss.
>>
>> Are you in a location where you can reliably
>> get 75Wh/day out of a 15W panel in winter?
>>
>> Depending on the time of load, you may be running
>> the battery flat every day.  Not a good idea.
>>
>> Charge efficiency is not 100%.
>>
>> Overdischarge management?
>>
>> Overcharge management?
>>
>> Depending on available insolation, time of load
>> and the characteristics of your panel,
>> you may be better off with a way bigger battery,
>> way bigger panel and a MPPT controller.
>> The MPPT is quite simple to build with a
>> microcontroller.  It also solves all your
>> charge management issues.
>
> Looks like the ideal solution to keeping my pick-em-up truck battery
> charged, since I drive it only every few weeks.

Do you really need 75Wh/day?
http://www.harborfreight.com/15-watt-solar-battery-charger-68692.html
For $12, it's hardly worth walking all the way to the lab to
turn on a soldering iron so you can spend way more than that
making one.
>
> And in Arizona we certainly don't lack for sunshine ;-)
> 		
>                                          ...Jim Thompson
>

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#446193

On Sat, 04 Feb 2017 16:35:25 -0800, mike <ham789@netzero.net> wrote:

>On 2/4/2017 3:00 PM, Jim Thompson wrote:
>> On Sat, 04 Feb 2017 14:42:31 -0800, mike <ham789@netzero.net> wrote:
>>
>>> On 2/4/2017 12:41 PM, gm wrote:
>>>> Hi to all.
>>>>
>>>> Did someone try this approach:
>>>> http://cds.linear.com/image/314_circuit_1.jpg
>>>>
>>>> when designing solar charger ?
>>>> Power consumption will be under 75Wh per day..
>>>>
>>>> Other infos:
>>>> - solar panel 15W
>>>> - battery 12V / 7Ah
>>>>
>>>> GM
>>> The devil is in the details.
>>>
>>> You seem to be focused on the isolation diode loss.
>>>
>>> Are you in a location where you can reliably
>>> get 75Wh/day out of a 15W panel in winter?
>>>
>>> Depending on the time of load, you may be running
>>> the battery flat every day.  Not a good idea.
>>>
>>> Charge efficiency is not 100%.
>>>
>>> Overdischarge management?
>>>
>>> Overcharge management?
>>>
>>> Depending on available insolation, time of load
>>> and the characteristics of your panel,
>>> you may be better off with a way bigger battery,
>>> way bigger panel and a MPPT controller.
>>> The MPPT is quite simple to build with a
>>> microcontroller.  It also solves all your
>>> charge management issues.
>>
>> Looks like the ideal solution to keeping my pick-em-up truck battery
>> charged, since I drive it only every few weeks.
>
>Do you really need 75Wh/day?
>http://www.harborfreight.com/15-watt-solar-battery-charger-68692.html
>For $12, it's hardly worth walking all the way to the lab to
>turn on a soldering iron so you can spend way more than that
>making one.
>>
>> And in Arizona we certainly don't lack for sunshine ;-)
>> 		
>>                                          ...Jim Thompson
>>

I was talking of others... I plan to buy that the next time I'm near
the Mesa Harbor Freight store.
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#446196

On 2/4/2017 7:35 PM, mike wrote:
> On 2/4/2017 3:00 PM, Jim Thompson wrote:
>> On Sat, 04 Feb 2017 14:42:31 -0800, mike <ham789@netzero.net> wrote:
>>
>>> On 2/4/2017 12:41 PM, gm wrote:
>>>> Hi to all.
>>>>
>>>> Did someone try this approach:
>>>> http://cds.linear.com/image/314_circuit_1.jpg
>>>>
>>>> when designing solar charger ?
>>>> Power consumption will be under 75Wh per day..
>>>>
>>>> Other infos:
>>>> - solar panel 15W
>>>> - battery 12V / 7Ah
>>>>
>>>> GM
>>> The devil is in the details.
>>>
>>> You seem to be focused on the isolation diode loss.
>>>
>>> Are you in a location where you can reliably
>>> get 75Wh/day out of a 15W panel in winter?
>>>
>>> Depending on the time of load, you may be running
>>> the battery flat every day.  Not a good idea.
>>>
>>> Charge efficiency is not 100%.
>>>
>>> Overdischarge management?
>>>
>>> Overcharge management?
>>>
>>> Depending on available insolation, time of load
>>> and the characteristics of your panel,
>>> you may be better off with a way bigger battery,
>>> way bigger panel and a MPPT controller.
>>> The MPPT is quite simple to build with a
>>> microcontroller.  It also solves all your
>>> charge management issues.
>>
>> Looks like the ideal solution to keeping my pick-em-up truck battery
>> charged, since I drive it only every few weeks.
>
> Do you really need 75Wh/day?
> http://www.harborfreight.com/15-watt-solar-battery-charger-68692.html
> For $12, it's hardly worth walking all the way to the lab to
> turn on a soldering iron so you can spend way more than that
> making one.
>>
>> And in Arizona we certainly don't lack for sunshine ;-)

I believe that is only 1.5 watts.  That's barely enough to trickle 
charge a car battery.  I've used a 2 watt, 15 volt wall wart to trickle 
charge a car battery and that's just barely enough running 24/7.

-- 

Rick C

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#446240

On 2017-02-05, rickman <gnuarm@gmail.com> wrote:
> On 2/4/2017 7:35 PM, mike wrote:

>>> And in Arizona we certainly don't lack for sunshine ;-)
>
> I believe that is only 1.5 watts.  That's barely enough to trickle 
> charge a car battery.  I've used a 2 watt, 15 volt wall wart to trickle 
> charge a car battery and that's just barely enough running 24/7.

How can you tell it's just barely enough?

-- 
This email has not been checked by half-arsed antivirus software 

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#446260

On 2/4/2017 8:22 PM, Jasen Betts wrote:
> On 2017-02-05, rickman <gnuarm@gmail.com> wrote:
>> On 2/4/2017 7:35 PM, mike wrote:
>
>>>> And in Arizona we certainly don't lack for sunshine ;-)
>>
>> I believe that is only 1.5 watts.  That's barely enough to trickle
>> charge a car battery.  I've used a 2 watt, 15 volt wall wart to trickle
>> charge a car battery and that's just barely enough running 24/7.
>
> How can you tell it's just barely enough?
>
My truck draws 9mA.  As I recall 6mA is the radio.
All I need is that plus whatever self-discharge is going on.

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#446539

On 2/5/2017 2:26 AM, mike wrote:
> On 2/4/2017 8:22 PM, Jasen Betts wrote:
>> On 2017-02-05, rickman <gnuarm@gmail.com> wrote:
>>> On 2/4/2017 7:35 PM, mike wrote:
>>
>>>>> And in Arizona we certainly don't lack for sunshine ;-)
>>>
>>> I believe that is only 1.5 watts.  That's barely enough to trickle
>>> charge a car battery.  I've used a 2 watt, 15 volt wall wart to trickle
>>> charge a car battery and that's just barely enough running 24/7.
>>
>> How can you tell it's just barely enough?
>>
> My truck draws 9mA.  As I recall 6mA is the radio.
> All I need is that plus whatever self-discharge is going on.

The self discharge is not trivial.  Or I should say the trickle current 
to maintain a car battery.  Without rereading all the post to find what 
size battery you are charging, it *is* a regular car battery, right?  Or 
do you have one of those sealed gel cells?

-- 

Rick C

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#446535

On 2/4/2017 11:22 PM, Jasen Betts wrote:
> On 2017-02-05, rickman <gnuarm@gmail.com> wrote:
>> On 2/4/2017 7:35 PM, mike wrote:
>
>>>> And in Arizona we certainly don't lack for sunshine ;-)
>>
>> I believe that is only 1.5 watts.  That's barely enough to trickle
>> charge a car battery.  I've used a 2 watt, 15 volt wall wart to trickle
>> charge a car battery and that's just barely enough running 24/7.
>
> How can you tell it's just barely enough?

You clipped my example.  It would take a full day to charge a slightly 
run down battery.  If it was fully down it would take three days.  I've 
measured the current it supplies and I see very little difference when 
it is run down or fully topped off.

-- 

Rick C

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#446594

On 2017-02-07, rickman <gnuarm@gmail.com> wrote:
> On 2/4/2017 11:22 PM, Jasen Betts wrote:
>> On 2017-02-05, rickman <gnuarm@gmail.com> wrote:
>>> On 2/4/2017 7:35 PM, mike wrote:
>>
>>>>> And in Arizona we certainly don't lack for sunshine ;-)
>>>
>>> I believe that is only 1.5 watts.  That's barely enough to trickle
>>> charge a car battery.  I've used a 2 watt, 15 volt wall wart to trickle
>>> charge a car battery and that's just barely enough running 24/7.
>>
>> How can you tell it's just barely enough?
>
> You clipped my example. 

Huh? I quoted all that arrived here.

> It would take a full day to charge a slightly run down battery. 

"barely enough" is, to my mind less than twice the self discharge rate.

> If it was fully down it would take three days.  

If the vehicle can sit for 4 weeks (without the battery being fully depleted) 
and then recover on that charger in only 3 days, I'd say it's got
at-least 8 times excess capacity (for for the task of preventing unattended
discharge)

> I've measured the current it supplies and I see very little difference 
> when it is run down or fully topped off.

That is not unusual in a constant-current charger.

-- 
This email has not been checked by half-arsed antivirus software 

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#446602

On 2/6/2017 10:55 PM, Jasen Betts wrote:
> On 2017-02-07, rickman <gnuarm@gmail.com> wrote:
>> On 2/4/2017 11:22 PM, Jasen Betts wrote:
>>> On 2017-02-05, rickman <gnuarm@gmail.com> wrote:
>>>> On 2/4/2017 7:35 PM, mike wrote:
>>>
>>>>>> And in Arizona we certainly don't lack for sunshine ;-)
>>>>
>>>> I believe that is only 1.5 watts.  That's barely enough to trickle
>>>> charge a car battery.  I've used a 2 watt, 15 volt wall wart to trickle
>>>> charge a car battery and that's just barely enough running 24/7.
>>>
>>> How can you tell it's just barely enough?
>>
>> You clipped my example.
>
> Huh? I quoted all that arrived here.
>
>> It would take a full day to charge a slightly run down battery.
>
> "barely enough" is, to my mind less than twice the self discharge rate.
>
>> If it was fully down it would take three days.
>
> If the vehicle can sit for 4 weeks (without the battery being fully depleted)
> and then recover on that charger in only 3 days, I'd say it's got
> at-least 8 times excess capacity (for for the task of preventing unattended
> discharge)

Yeah, well I'm not sure there is any meaning to that calculation.  This 
unit barely will put current into the battery.


>> I've measured the current it supplies and I see very little difference
>> when it is run down or fully topped off.
>
> That is not unusual in a constant-current charger.

Who said it was a constant current charger?  It's a tiny wall wart that 
barely charges the battery.  Even a 2 amp charger will fully charge a 
battery overnight.  This thing takes days because there is very little 
excess capacity compared to the minimum current required to keep the 
thing up.  But then again, I guess it is constant current considering 
that the battery always draws the full load it is capable of delivering. 
  It's a 15 volt power pack and once attached to the battery it never 
gets above 13.5 volts.  So it does put out a constant current under 
those conditions.

I don't think charging a lead acid battery is a zero sum game.

-- 

Rick C

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#446207

On Sat, 04 Feb 2017 16:35:25 -0800, mike <ham789@netzero.net> wrote:

>Do you really need 75Wh/day?
>http://www.harborfreight.com/15-watt-solar-battery-charger-68692.html
>For $12, it's hardly worth walking all the way to the lab to
>turn on a soldering iron so you can spend way more than that
>making one.

Argh.  That's an amorphous silicon solar panel.  Low efficiency (about
7%) but cheap to produce and works in low light and shade:
<http://www.solar-facts-and-advice.com/amorphous-silicon.html>
<http://energyinformative.org/amorphous-silicon-solar-panels/>
In full sunlight, open circuit voltage = 20v and short circuit current
= 0.1A or 2 watts.

I have two solar panels similar to the Harbor Freight model.  I used
them in the distant past to keep the battery charged when I had a
collection of dead vehicles parked in front of my house.  
<http://802.11junk.com/jeffl/pics/home/slides/cars.html>
A dead car in front is considered a status symbol and indication that
I own the house as no landlord would let a tenant collect dead cars.
During the winter, I had to top off the batteries every week with a
boost from a conventional battery charger:
<http://802.11junk.com/jeffl/pics/drivel/slides/dead-battery-chargers.html>
as the solar panels were insufficient.  I eventually went to a 12v
1.5A "battery maintainer" powered by the AC line.  They worked quite
well until someone stole both of them.

I also have an ICP Solar 04021 Battery Saver Plus 5w, which is about
twice the size of the Harbor Freight model, and allegedly delivers
twice the power:
<https://www.amazon.com/ICP-Solar-04021-BatterySaver-Plus/dp/B00008IHTV/>
Oddly, I've never tried to use it.

Incidentally, you can purchase a ready made solar powered battery
maintainer.  Just add a solar panel:
<http://products.batterytender.com/Accessories/Battery-Tender-Solar-Controller.html>
<http://products.batterytender.com/021-1162-man.pdf>
Or, get it with a 5w, 10w, or 15w panel built in:
<http://products.batterytender.com/Chargers/>  (near bottom of page).



-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

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#446218

On 2/4/2017 9:17 PM, Jeff Liebermann wrote:
> On Sat, 04 Feb 2017 16:35:25 -0800, mike <ham789@netzero.net> wrote:
>
>> Do you really need 75Wh/day?
>> http://www.harborfreight.com/15-watt-solar-battery-charger-68692.html
>> For $12, it's hardly worth walking all the way to the lab to
>> turn on a soldering iron so you can spend way more than that
>> making one.
>
> Argh.  That's an amorphous silicon solar panel.  Low efficiency (about
> 7%) but cheap to produce and works in low light and shade:
> <http://www.solar-facts-and-advice.com/amorphous-silicon.html>
> <http://energyinformative.org/amorphous-silicon-solar-panels/>
> In full sunlight, open circuit voltage = 20v and short circuit current
> = 0.1A or 2 watts.

Not sure why you are multiplying these numbers, but assuming this is the 
potential power output from the panel is a faulty deduction.  Is this 
just a convention for rating a panel?

-- 

Rick C

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#446262

On Sat, 4 Feb 2017 22:36:45 -0500, rickman <gnuarm@gmail.com> wrote:

>On 2/4/2017 9:17 PM, Jeff Liebermann wrote:
>> On Sat, 04 Feb 2017 16:35:25 -0800, mike <ham789@netzero.net> wrote:
>>
>>> Do you really need 75Wh/day?
>>> http://www.harborfreight.com/15-watt-solar-battery-charger-68692.html
>>> For $12, it's hardly worth walking all the way to the lab to
>>> turn on a soldering iron so you can spend way more than that
>>> making one.

>> Argh.  That's an amorphous silicon solar panel.  Low efficiency (about
>> 7%) but cheap to produce and works in low light and shade:
>> <http://www.solar-facts-and-advice.com/amorphous-silicon.html>
>> <http://energyinformative.org/amorphous-silicon-solar-panels/>
>> In full sunlight, open circuit voltage = 20v and short circuit current
>> = 0.1A or 2 watts.

>Not sure why you are multiplying these numbers, but assuming this is the 
>potential power output from the panel is a faulty deduction.  Is this 
>just a convention for rating a panel?

Nope.  You're correct but I didn't want to get into the details.  The
data sheets sometimes use the simple arithmetic I used.  However, the
real power output is about 20% less.  The difference is called the
fill factor.  Measure Voc (Voltage open circuit) and Isc (Current
short circuit) and plug it into the calculator below.  Multiply and
you get Pt (theoretical power), the maximum power that an ideal solar
panel can deliver.  Multiply again by the approximate fill factor and
you get a more realistic value for Pmax (maximum power):
<http://www.ni.com/white-paper/7230/en/>
<http://www.pveducation.org/pvcdrom/solar-cell-efficiency>
<http://www.pveducation.org/pvcdrom/fill-factor-0>
<http://www.pveducation.org/pvcdrom/short-circuit-current>
<http://www.pveducation.org/pvcdrom/open-circuit-voltage>
Everything else causes the power output to decrease.  Output drops
when the panel gets hot, the angle of the sun is less than
perpendicular, dirt on the glass, voltage drop from series diodes,
reflections, weather, clouds, panel aging, etc.



-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

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#446235

On 2/4/2017 1:41 PM, gm wrote:
> Hi to all.
>
> Did someone try this approach:
> http://cds.linear.com/image/314_circuit_1.jpg
>
> when designing solar charger ?
> Power consumption will be under 75Wh per day..
>
> Other infos:
> - solar panel 15W
> - battery 12V / 7Ah

Google "MPPT"

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#446253

On Saturday, February 4, 2017 at 3:41:40 PM UTC-5, gm wrote:
> Hi to all.
> 
> Did someone try this approach:
> http://cds.linear.com/image/314_circuit_1.jpg
> 
> when designing solar charger ?
> Power consumption will be under 75Wh per day..
> 
> Other infos:
> - solar panel 15W
> - battery 12V / 7Ah
> 
> GM

A very simple charger can be constructed with
a few current limiting resistors and forward
biased diodes. The reverse breakdown voltage
of the diodes must be larger than the maximum
battery voltage so that the battery does not reverse discharge into the solar panel, after 
sundown. 

Ideally, the maximum charging current should
be 700 mA, i.e., (battery AH rating)/10.0 --
current limiting resistors ensure this, as
well as ensuring that the maximum forward 
current of the diodes is not exceded. Also
note that the solar panel power output rating 
is what has been measured under ideal testing conditions of the manufacturer -- on site 
daily power output will vary will depend on 
that day's weather conditions.  

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