Forums

Battery charger with solar panel

Started by gm February 4, 2017
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
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.
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.
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
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.
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.
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 >
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.
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
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