Noisy Boysie avatar image
Noisy Boysie asked

250/100 on a solar divert

Odd question I know but trying to find a solution to charge an off grid power bank with excess solar energy

In my house i have 4kw solar setup with a solar diverter to heat hot water when excess solar energy is being created

Can I use that output of this solar diverter which will vary in watts @240v into a 250/100 charge controller to then charge a power bank? When the power bank is full I could relay back the power to the immersion heater?

uk power is 220-240 so in theory the 250max input and varying watts would work?

my other issue is the battery bank will be a li-ion chemistry and I'm not sure if the charging can be manually set to accommodate the CC-CV charging profile as i see it only supports LifePo4

as uk power does flux a little I would prob need some thing to keep the V down below 250V but that shouldn't be to hard to work out.

Any other suggestions out there? cant find any products that seem to give me any other solutions where both hot water and battery charging can be supported in the same device with the battery being offgrid. eg not part of the feed in

An example use could be to store power while there is excess and then heat the water when the water needs heating preventing the use of gas needed if some one empties the hot water tank while there is no solar. Priority of hot v storing energy would have to be worked out eg heat water first then store after that or store then heat water for example.


MPPT Controllers
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1 Answer
wkirby avatar image
wkirby answered ·

No, you cannot connect 240V AC (350V Peak) into the input of a MPPT controller. It is not designed for this.

Those solar diverters are designed to drive passive resistive loads (heating elements) only. They vary the output power by a form Pulse Width Modulation by triggering on the leading edge or trailing edge of the AC waveform. An active load (like a battery charger) would not be able to cope with this form of power control and would likely be damaged.
Also, even with a varying Voltage at the input of a mains charger (like the grid Voltage varies) the charger will always try to maintain the set charging power.

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