flippineck
- Sep 8, 2013
- 349
- Joined
- Sep 8, 2013
- Messages
- 349
It's a question about my solar energy setup again.
I used to have a cheap ebay MPPT charge controller to regulate the power coming from my solar panels into my 2 leisure batteries configured as a nominal 12V parallel pair.
Discovered it wasn't MPPT, it was a PWM design.
Went out and bought a true MPPT controller having studied reviews.
Great, all's working with the real MPPT now fitted.
BUT.. the old PWM jobby used to do a good job of switching off the load output when the battery voltage fell below a certain level, and then switching it back on again when the level rose back above a certain slightly higher level. The hysteresis seemed just about right.
The new controller just keeps the load on all the time until the battery voltage falls to inverter cut out level. Whereupon the 240V output from the inverter fails, but the load output from the MPPT controller is still 'on'.
There are a whole bunch of settings for different modes of load output control but they all seem to be more concerned with the timing control of the output, relative to dusk/dawn, for a solar powered 'street lighting' type setup. Nothing really to do with battery content monitoring.
I wanted to use the load output from the controller to switch a relay, to automatically switch between appliances using the inverter output or grid mains, depending on how full the storage battery was.
It now seems I can't use the new charge controller to switch the inverter output like this.
So, it looks like I need to build a seperate, standalone battery voltage monitoring circuit. The requirements would be as follows:
- operating / monitoring current as low as possible.
- when battery voltage falls below say 11.0V, make the control output 0V
- when the battery voltage rises back above say 12.0V, make the control output equal to the battery voltage.
The output would be fed to a relay: http://www.maplin.co.uk/p/round-base-10a-relay-12v-dc-3pdt-jg62s
120 ohm coil, 100mA @ 12vdc
I'm thinking, transistor / potential divider type circuit? What part numbers would be suitable? All I really remember from control tech 101 was 2 resistors feeding the base of a generic transistor, whose collector was wired into the relay coil.
I used to have a cheap ebay MPPT charge controller to regulate the power coming from my solar panels into my 2 leisure batteries configured as a nominal 12V parallel pair.
Discovered it wasn't MPPT, it was a PWM design.
Went out and bought a true MPPT controller having studied reviews.
Great, all's working with the real MPPT now fitted.
BUT.. the old PWM jobby used to do a good job of switching off the load output when the battery voltage fell below a certain level, and then switching it back on again when the level rose back above a certain slightly higher level. The hysteresis seemed just about right.
The new controller just keeps the load on all the time until the battery voltage falls to inverter cut out level. Whereupon the 240V output from the inverter fails, but the load output from the MPPT controller is still 'on'.
There are a whole bunch of settings for different modes of load output control but they all seem to be more concerned with the timing control of the output, relative to dusk/dawn, for a solar powered 'street lighting' type setup. Nothing really to do with battery content monitoring.
I wanted to use the load output from the controller to switch a relay, to automatically switch between appliances using the inverter output or grid mains, depending on how full the storage battery was.
It now seems I can't use the new charge controller to switch the inverter output like this.
So, it looks like I need to build a seperate, standalone battery voltage monitoring circuit. The requirements would be as follows:
- operating / monitoring current as low as possible.
- when battery voltage falls below say 11.0V, make the control output 0V
- when the battery voltage rises back above say 12.0V, make the control output equal to the battery voltage.
The output would be fed to a relay: http://www.maplin.co.uk/p/round-base-10a-relay-12v-dc-3pdt-jg62s
120 ohm coil, 100mA @ 12vdc
I'm thinking, transistor / potential divider type circuit? What part numbers would be suitable? All I really remember from control tech 101 was 2 resistors feeding the base of a generic transistor, whose collector was wired into the relay coil.