How to divert power from the solar to the 12V heater when the batteries are charged.

Hello,
I have a 100W panel, 50Ah battery, 20A charge controller.
The max power indicated by the controller is about 7A
The battery charges quickly on summer sunny days and it's a bit of a waste of that energy.
I would like to reheat the water in the barrel. I have a 12V ordinary car heater, the kind for a cup.

QUESTION:
What circuit, checking the voltage on the battery, when it reaches 14.8V will switch on the heater for a specific time (e.g. 10 minutes).

My idea:
The circuit tests the voltage, turns on the heater connected to the battery. Then the tested voltage drops, but the circuit, once switched on, should only start measuring the voltage after the specified time, so that it does not switch it off when it drops after the load on the heater.

Regards,
Marcin from Kalpapada
http://kalpapada.wixsite.com/kalpapada/single...ika---energia-elektryczna-ze-s%C5%82o%C5%84ca

Power is not specified in amperes (A).

Good idea but connecting the heater to the batteries and not instead of the batteries is a poor idea. Batteries wear out as they charge and discharge, so such a duty cycle may reduce their life. You can use a relay that will switch the current for us. Instead of time, you could give a hysteresis so that the switch-on and switch-off thresholds are different. A simple circuit with a comparator should suffice.

This is true. In Amps we specify the current .
...and the fact that the battery loses its life.
And could I ask you to draw a wiring diagram of such a circuit?
I'm out of electronics school and connecting the components won't be a problem. Worse with the design and selection of components. Maybe there are ready-made circuits of this type on the web with a schematic diagram and a list of components.
Regards,
Marcin

.

This can of course be done in many ways but this one should work.
As IC1 you can give a TL431, optocouplers of any kind e.g. from any switching power supply. Transistor can be BC547 or other NPN. A relay, e.g. a car relay with a changeover contact. The voltage from the battery is applied to a divider with resistor R1, zener diode D1 and potentiometer R2. When the voltage rises and the slider is above 2.5V, the optocouplers are switched on and the zener diode is cut off, the voltage on the potentiometer increases by 2.5V. This will give the necessary hysteresis so that the relay does not vibrate. The recharge voltage will therefore be 2.5V lower than the voltage at which charging stops.
Instead of a zener, you can give ordinary silicon diodes and select the hysteresis by their number, but switch them in reverse, assuming 0.6 - 0.7V per diode.

We switch the relay contact so that its switching on causes the cell to overvolt the heating circuit. The LED is not mandatory but indicates the operation of the heater.

Wow! Thank you! Now I'm in for a big reminder of my electronic school days to get it all together and running!
One could close the topic, but....
...since there are many ways to solve this conundrum, maybe someone else can throw up some?

In my search for a quicker way (shortcut) and an easier/ready solution, I came across this video:
https://www.youtube.com/watch?v=XINhR-3XWUA

This controller I already have .
ebay
12V-Voltage-detection-control-delay-Upper-and-lower-voltage-range-control-switch-/
here are the instructions:
http://vi.vipr.ebaydesc.com/ws/eBayISAPI.dll?...amp;cspheader=1&oneClk=2&secureDesc=0

Moderated By ANUBIS:

3.1.18. Do not send links that become inactive after a certain period of time. This will cause the discussion to lose any meaning.

.

I will write how I manage to configure this so that if 14.8V is detected it will switch on the 12V car plug heater for a few minutes.

Any suggestions?