Solar charger schematics
mugur
Posts: 105
Hello. I've bought 6 solar panels with these properties:
Voltage:2volts, Current: 150mA
What i need is to have them charging a batery (7,2V or 8,4V) using a charging circuit. Is there any simple one i can build myself using a prototype pcb, but still to be current effective and reliable also? I know it will take a lot to fully charge a battery even if it is a 1500mA one, but will do for what i need.
Thank you for any help.
Voltage:2volts, Current: 150mA
What i need is to have them charging a batery (7,2V or 8,4V) using a charging circuit. Is there any simple one i can build myself using a prototype pcb, but still to be current effective and reliable also? I know it will take a lot to fully charge a battery even if it is a 1500mA one, but will do for what i need.
Thank you for any help.
Comments
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- Stephen
And if your pack is 7.2V @ 1500mAH this = a 1/10C Charge rate .
This is just about right for a NiCd or NiMh Batt pack ..
I would use a LM7805 and Lift it like so ( see attachment)
Each Diode ads .69 Volts to the 5V 7805 ..
a 7875 is ideal but are not as easy to find IMHO ..
BTW if you add a diode in series on the output it Drops .69 V (silicon)
Germanium is . 3 I think .. so use a combo too get the V Out you want
it would be hard to cook the pack during initial charge with such a small panel so
as long as the current tapers off as the Batt gets to the full charge then it would be self regulating...
I would aim for a Output from the Reg to be at 7.3
BTW I have a solar backpack from voltaic systems that I use with my cell phone ..
I uses a 7.2V 2500mAH NiMh RC pack as a storage pack . the OCV on the Panels is 10V @ 400mA so I just run the panel output to the pack
and I have never had a issue with over charging ..No Reg ...
I then run the pack to a SMPS to buck it to 5V to run the cell ..
Simple " Dumb charger" .
Peter KG6LSE
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"Carpe Ducktum" "seize the tape!!"
peterthethinker.com/tesla/Venom/Venom.html
Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S.
LOL
Peter, i will use that schematic for now. Thank you very much for your detailed explanations.
I was a little confused about the statement here: "Since we are only using a one volt solar panel, it will take a while to recharge two 1.5 volt batteries, but they will get a full charge in time."
www.philstewart.org/blog.php/2008/03/how-to-build-a-solar-powered-battery-charger-for-really-cheap/
So basically if i use 3+3 of my panels (3 in parallel with the other 3) i will get 6V output voltage but higher current?
This will still charge a 7,2V batery ?
Post Edited (mugur) : 1/16/2010 10:04:36 AM GMT
So no sadly a 6V Panel will not " fully " charge a 7.2V Batt directly .
The only thing it will do is charge the batt to 6V .
Then when V Batt is = V Solar current will stop flowing ..
Thus Charging will stop too.
From the site you Linked to .
"QUOTE""I went with a 5.1 volt diode since this is more voltage than the batteries and the price was right. I am pretty sure the voltage rating of the diode won't matter so long as it is more than the combined voltage of the batteries you intend to charge.""
Sounds like a Zener Diode .
I have never seen a Zener being used in series like that .. Zeners are shunt Regs ..
Peter KG6LSE
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"Carpe Ducktum" "seize the tape!!"
peterthethinker.com/tesla/Venom/Venom.html
Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S.
LOL
so the last few 100mV could take days to soak up .
BTW I have bean assumong this whole time that 2V is the" loaded voltage " for your panels.
if its the OCV then you will might more panals
what kind of charger you use depends on how long you want your pack to live ..
If replacing a pack due to a slight over charge once a few years then your idea is ideal !
but It will Over charge ... just not too much ..
I normlay dont go over a 1/10C Charge rate ever on a dumb charger .
By going to 2 banks in parrrell of panals you are close to a 1/5C charge rate
this Could ruin your Pack in a few months .
Its not the main charge current I worry about ,
Its the constaint trickle that comes from a 8V panal going in to a 7.2V batt..After ts fully charged .
This can boil your Batts ..
But as I stated above If you could some how make a 7.2V Panel it would charge very slow in the end ..
How fast do you want the batts to charge ???
Peter KG6LSE
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"Carpe Ducktum" "seize the tape!!"
peterthethinker.com/tesla/Venom/Venom.html
Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S.
LOL
The sollar panels are 2V+ the loaded voltage is 2V. So i was thinking if i charge my battery with 1/3C and they holds already for several months maybe it will not be ruined charged at 1/5 C...
I will like to be efective enough with the charging but i do not have a "time frame" for this. Just i though if i will double the charging current and will provide enough voltage i will be able to charge the 7,2V (niMH) battery optimal enough...
So If you are able to "un plug" the batts from said Panels soon after they reach Full charge ..... Then direct charge at 1/3C is Great!
I just worry about leaving the panel on it forever like in a solar light application ..
And in realty it wont completely fry the batts the first time you forget .. it just makes them last shorter in there overall life span .
Peter KG6LSE
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"Carpe Ducktum" "seize the tape!!"
peterthethinker.com/tesla/Venom/Venom.html
Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S.
LOL
So, i have to create a charging circuit wich will stop the charge, like the laptops do with their batteries. Well, then it means this is the kind of circuit schematics i have to find [noparse]:([/noparse]
the Batt just "eats it" and makes heat ,, the more overcharge the more heat hence why 1/10 C is about right .
Example a 1 Amp 12v Un Reg Wall Wart ran right to a large car batt has a super low chance of super harmfull over charge because the batt is so large in compared to the charger . think of a garden hose filling a pool .. there will be overflow but most of it will be soaked up in the lawn LOLs.
now at high over charge Venting can occur and in the case of a sealed NiCd Or NiMh cell once you let the smoke out you cant recover it .. but as in the car Batt Just add some DI water once in a blue moon and Life is good ..
The reason My solar backpack system at around 1/4C charge rate does not smoke it self is that its never in the sun for very long ..
So stick with 1 string of panels at 8V or so Volts and let er rip! but you should still add a Diode [noparse];)[/noparse]
EDIT : With Info from Wiki (not my favorite source to quote)
{Trickle charging
Some equipment manufacturers consider that NiMH cells can be safely charged in simple fixed, low-current chargers with or without timers, and that permanent overcharging is permissible with currents up to 0.1C/h.****= 1/10C***** According to the Panasonic NiMH charging manual, extensive trickle charging can cause battery deterioration due to overcharging, and it is the least preferred charging method concerning battery performance. If it is used, the trickle charge rate should be limited to between 0.033C/h and 0.05C/h for a maximum of 20 hours to avoid damaging the batteries.}
Peter KG6LSE
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"Carpe Ducktum" "seize the tape!!"
peterthethinker.com/tesla/Venom/Venom.html
Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S.
LOL
Post Edited (Peter KG6LSE) : 1/17/2010 5:35:57 AM GMT
i know what i have to do.