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Posted

Good morning all

I have a Synapse 12v  2.4 kw inverter connected to two hubble 12volt batteries in series and two 455 watt panels on the roof.

The mppt charger has a maximum of 1000watts

In the middle of the day I get about 800w from the panels.

If I add another 455watt panel, my panel watts would increase to about 1400watts, that is more than the mppt charger limit.

My question is: If I use for ex. 700 watts from the inverter with appliances in the house, and I get maybe 1300watts from the panels, the excess is about 600watts.

Because this 600 watts is below the mppt charger limit, will the charger use this full 600watts to charge my batteries while i use 700watts AC in the house?

Or will I just lose everything that is above 1000watts?

Thank you for any replies

Redge

Posted
2 hours ago, Redge said:

I have a Synapse 12v  2.4 kw inverter connected to two hubble 12volt batteries in series

I hope you mean a 24 V inverter, or that the two 12 V batteries are in parallel.

2 hours ago, Redge said:

The mppt charger has a maximum of 1000watts. ...

Or will I just lose everything that is above 1000watts?

You will lose everything above 1000 W. Both battery charge power and load power from solar have to go through the MPPT, and it has a maximum power rating.

You could get around this by using a small external MPPT for your extra panel(s). This MPPT would connect directly to the battery. If this external MPPT is rated for say 500 W (e.g. 80 A @ 12.5 V output), then you have effectively increased your solar charge controller capacity from 1000 to 1500 W.

Posted

Thank you Coulomb

I did make a typo, my system is 24Volts not 12V but your answer would still apply.

I already have a 20A  24V solar charge controller, could I also use that directly on the batteries with an extra panel?, I know it less efficient than MPPT.

If I do it like this, does the size of the extra panel matter?

Thank you for your help

Posted
4 hours ago, Redge said:

I already have a 20A  24V solar charge controller, could I also use that directly on the batteries with an extra panel?,

Yes, sure.

Quote

I know it less efficient than MPPT.

Some people claim that a PWM system, properly configured, can be more efficient than an MPPT, since there are no switching losses most of the time. I disagree. But a PWM system, especially in a situation like yours where your MPPT is already maxed out, can be quite effective.

Quote

If I do it like this, does the size of the extra panel matter?

Obviously, your external solar charge controller has to be sized for the panel, but yes, the size of that won't be affected by your other system's limits.

There can be some unwelcome interaction between the two solar controllers, but I found I could avoid that my having the smaller system cut out at a slightly lower voltage than the larger system.

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