Charging battery solar

kestak

Newly Enlightened
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Nov 19, 2009
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18
Greetings,

I have what I think very simple questions for the pros here:

I got a Parmax electric fence with solar panel. Sadly, I cannot get it to full day full sun. So my solution is to simply add a solar panel to the circuit to get more juice into the battery.
I plan to buy a 6v 3watts solar panel to add to the curcuit.
1- can i just connect my red/black wires of the new pannel at the same place where you see the diode and the connectors on the picture?
2 - do i need to put a diode between the new panel and the connector with the diode on the panel red wire (or black wire)?
3 - i cannot see the whole number on the diode. If i need to buy a diode per question 2, what should i buy?

Thank you




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KITROBASKIN

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Give this thread another post:
Hopefully another will give some more concrete advice. I suggest a complete disconnect to the integrated panel. Maybe more power from a remote panel; kind of depends how sunny your area is, and the panel placement.
 

Dave_H

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Agreed that if you use external panel(s), disconnect internal one unless you can get identical ones. Dissimilar panels most likely won't work out well. 6v panels are less common that 12v.

For blocking you should be OK with 3A Schottky rectifier such as 1N5820/21/22, or 1N5823, one per panel. Regular silicon rectifier would have slightly higher drop, not the best at lower voltage i.e 6v. Wire each diode in series with panel +ve (red) wire, and connect all diode cathodes (banded ends) together at the screw terminal.

Panels will be rated at peak watts which is ideal output i.e. directly facing overhead sun on sunny day; decreasing with sun angle, cloud cover, blockage etc.

Do you know how much battery capacity is used per day i.e how much solar charging is required to add per day to keep things running? 14Ah battery looks a bit much for the panel that size, except maybe ideal solar conditions.

What is the active area (sq. in.) of existing panel ? (hard to see due to glare). It is possible to run a ballpark estimate of how much panel you will need.

Some useful info:

- sun impinges about 1000W per square meter under ideal conditions.
- efficiency of crystaline silicon panel is 14-18% (140-180W peak per square meter).
- amorphous panel is only about 8% efficient (80W peak per sq. m.)
- power delivered will be less than above unless charge controller is smart (MPPT)(unlikely) (expensive)
- charger and battery charging efficiency further reduce energy stored (harder to estimate).

Dave
 

KITROBASKIN

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Good stuff Dave H.
I might add that rated watts of panel yields about 80% actual, under clear, bright skies.

I once destroyed an economy multimeter while trouble shooting a friend's electric fence ages ago; turns out the amperage is really low but the volts are very high. Unless individuals are getting hammered (shocked) regularly or there is a malfunction, I understand electric fences do not use much power.
 

Dave_H

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Ottawa Ont. Canada
This fencer brand and models identical/similar this one appear available locally here (OTC), might be able to see one at Lowes/Rona or other chains.

Panel looks to be roughly 30-36 sq. in. crystaline silicon; array appears to be two paralleled groups of 18 cells. At 0.45v per cell that would give around 8v which is`reasonable for linear charging of 6v SLA battery; but not certain without examining a unit.

Vendor claims operation up to 21 days on full charge, with no sunlight. This likely assumes no/minimal contacts, good battery with low self-leakage, and not too much leakage from fencing due to moisture/dirt etc. if that matters.

Rough estimate is existing panel could charge at up to 0.5A (ideally), more likely 0.25A-0.35A peak, would take several days of good sunlight for full charge. A larger battery is not likely to help.

Dave
 
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Dave_H

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+

This may be more than you wanted to spend,
wiring in a voltage converter (9V~35V input to 6V output) to a 50W panel would work.
..a 50W panel will give about 35~40W in perfect conditions.

Figuring your Parmak has some kind of charging controller built in.

about $70 total


A 6v SLA needs more than 6v to charge, tops out somewhat below 7v.

Output from external dc-dc converter is not going to behave like a panel connected to the fencer input.

My crude estimate for panel is around 3-4W peak, 50W is large overkill. A 10W, 6v panel should work. Granted, lots of good deals for 12v panels out
there, but 6v are available e.g. Amazon for $20-$30.

Dave
 

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