PV Gap

Christy Said:

Electric Fence Question For Anyone That Has One or Knows This? Please?

We Answered:

Hi, No offense meant in this, but curiousity. I was raised on a 100 acre farm and we had horses, though never electrified a fence.

Might there not be some monitoring system, similar to an alarm system in a house, that would alert you of any disruptions in service? One might be in the barns/stalls, while the other is in the house?

Certainly the mechanics for electrifying the fence have to be accessible somewhere.

I am in a position as a building maintenance Mgr. to have access to the alarm system. On the keypad for example, one sets the alarm with a code. If the doors open, which are on Mag Locks, (Closing or opening a circuit) the alarm beeps; for a specific amount of time, until and unless it's disarmed with a code.

Miriam Said:

Solar charger circuit question?

We Answered:

Possible. You need to do some calculations.

1. You need to know the capacity in mA-hour of the battery.

2. Measure the short circuit current output of the solar panel with a multimeter, it will be somewhere around 200-400 mA.

To avoid damage, you should not charge the battery at a faster rate than C/10. So if this is a 500 mA-hour battery, the fastest charge rate should be 50 mA. If the solar panel is capable of more than that, you need a series resistor to limit the current to that value. It should take 15 hours to charge the battery under these conditions.

You can charge a a faster rate than C/10:
Using a timer it is possible to charge at C/3.33 for 5 hours. This is a little risky, since the battery should be fully discharged before charging. If the battery still has some of its capacity left when the timer starts you would have a good chance of damaging the battery.


Series resistance calculation. The short circuit current test above will determine the internal resistance of the panel, as Ri = open circuit voltage / short circuit current.

If the charge rate is Ic (C/10) then R = [ (14–7.2–0.7) / Ic ] – Ri
(0.7 volt is for the diode)

For example, under the conditions above, if short circuit current is 300 mA, Ri = 14/0.3 = 47 ohms
Series R = (14–7.2–0.7) / 0.050 – 47
R = 75 ohms, 1 watt.

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