PV bypass charge controller direct to heater when batteries are full.

I show how I automatically bypass PV input from charge controller to direct into a resistance baseboard heater. I used an auxiliary contact on a Midnite Solar Classic charge controller to switch a contactor. But it could also be switched manually or with some other device.

[@JxH]

I've been tempted to simply wire-up some panels directly into a heater. Since my house is heated with electric baseboard heaters, the solar powered heater would come right off the top of my heating bill, saving money. Payback would be about 'several' years (3-5 roughly). Payback is helped by skipping all the costs and lifespan issues surrounding batteries.

[@LarryKapp1]

There are lots of used pv around that would work perfect for that application . They should be inexpensive . Although there are supposed to be rebates this coming year for air sourced heat pumps that might pay for the whole thing ( if you are in usa).

[@FRESNEL_COOKING_SOLAR_OVENS24]

You just need dc heating elements 24v wired directly to solar panels to heat water in insulated barrels.
You only 24v 350w solar panels wired individually to each 24v 300w heating element.
Solar water heating is best to be separated from your house power. No point for that headache with relay just because you have too many panels installed on the solar inverter and is charging your battery quick.
Just unplug few panels and make a separate system. When water reaching 60°C, use a relay to send power to your house lighting 24v or floor heating. Why would you put stress and cycle on batteries??? Reduce their cycle usage by spend ling extra solar for water heating directly. Water first, is more efficient.

[@LarryKapp1]

In the short days of winter and on overcast days I need the extra power into the batteries. I don't think the lithium batteries mind if they fill up quickly or not . There is no extra cycle use on the batteries because once they are full for the day they don't charge any longer. I get what you are saying about direct PV to hot water but don't have room for all those barrels of water. the other factor is the proximity of the pv to the load - with the panels wired for 240v there is little voltage drop to where the power is used . The relay isn't a headache at all and only cost $35 used. I also have another system where I do heat water directly from PV but I still need some kind of control to keep water from over heating. I get if I sized everything just right with enough water you could do it without regulating water temp but I don't have the room for that kind of system. Thanks for your comments.

[@FRESNEL_COOKING_SOLAR_OVENS24]

@@LarryKapp1 to controll water temperature there is temperature thermostat relay 240v that shuts off the power when water reaches your desired temperature.

[@LarryKapp1]

@@FRESNEL_COOKING_SOLAR_OVENS24 I use a digital thermostat in series with the control line of the IGBT that is rated for DC - works fine and if I wanted to I could expand up to something like 1200v dc and 500 amps ! Not that I am going to though. So basically using a transistor instead of a switch to control power.

[@offgridwanabe]

Why not just use Mppt float and set the relay to the voltage you want to start heating

[@LarryKapp1]

You mean via the Aux ? If you mean via the aux of my controller -- I guess that would work too. For lead acid it would work better using waste not since that gets the extra power from both absorb and float. But with lithium float should work since there is no extra power at the absorb stage of charging.

[@offgridwanabe]

@@LarryKapp1 Ya with the aux and with lithium the top 10% of soc is not very productive so it works well as long as you have enough solar to keep the battery charged.