LVD override or work around

[RJT4054]

My company sells and installs solar systems for electric fence chargers and other AG related applications (water systems, lights etc) During the winter months (NE Ohio) we are loosing the power on our fence chargers. #1 The fence chargers have an auto shut down if the battery drops below 11.2 volts. #2 The draw on the battery is ~200 ma. The cause of the shut down is a lack of power from the solar panel caused by #1 long nights, #2 Cloudy days, #3 snow on the panels. On a sunny day with snow on the panel the charge is less than 1/2 of a panel with no snow! The controllers we use have a LVD @ 11.2. How can I get the controller to allow the panel to charge the battery when the voltage drops below the LVD.?

[bcroe]

I would suggest that using a SERIOUS grid tie size PV panel (250W) would allow you to make adequate
power even under clouds. Mount that panel in landscape at a 90 degree elevation and your snow problems
will be hugely diminished. And a continuous drain of 0.2A at 12V sounds like an extremely inefficient fence
charger to me, remember the ones that ran on a 6V dry "fence battery"? Bruce Roe

[SunEagle]

Your problem is trying to raise a dead horse. Once that battery has gone below 12volt just about nothing is going to get it back to what you want.

As Bruce stated you probably need to go with a larger solar panel for the Winter months or find a way to manually charge the battery if you go more than a day without sunshine.

[Sunking]

Are you joking, or just that uninformed? The LVD has nothing to do with charging the battery. The battery never gets disconnected from the controller. Only way that could happen is if you connected the battery to the load terminals.

FWIW your system is poorly designed if the battery cannot keep power on for 4 days without SUN.

[PNjunction]

A lot of people don't realize that the usual 10.7 to 11.7v LVD voltage, is NOT to be used for normal disconnects, but merely as a dead-man switch to protect a battery that is already fully discharged from going further and causing immediate physical damage.

When it trips, you must recharge to full immediately, and not with an unreliable source of solar power. That LVD voltage is a battery-saver IF you recharge. However, "saved" does not mean you haven't given the battery a heart-attack and cycle life has been adversely affected.

Under normal use, this LVD should be MUCH higher. In your case, about 12.2v roughly estimating about 50% DOD.

Even worse, is not recharging to full pronto. Your buyers have had their batteries sit around sulfating in a totally discharged state, so that compounds the problem. Not enough solar. Not enough capacity. Too low of an LVD voltage destroying batteries with repetetive partial-state-of-charge conditions.

The next thing you do is figure out why your *primary* LVD, which should be much higher has failed. For your little agm's, that would be around 12.2v under load, NOT the dead-man 11.2v catch.

If we knew what size your panels are, and what capacity your battery is, I'll bet that a minimum of quadrupling your panel power and at the very least doubling your battery capacity is called for. Get ready to recycle every one of your existing batteries.

Your system needs a major redesign.