question

michael7s avatar image
michael7s asked

Can a charge controller 'pass through' power?

I'm curious if a charge controller can pass through 'supplemental' power when the batteries can't keep up. Most answers in other forums suggest that the charge controller will 'only charge the depleted batteries' and there is no concept of 'pass through' power. That's a head scratcher for me.

So. A thought experiment:

Let's say my solar panels are sending down 5000 watts ( 50vdc 100a) to my 100a MPPT charge controller. Let's say the load on the battery/inverter side is constant 1200 watts. This quickly depletes a tiny 12 battery (for this thought experiment, let's suppose a 14ah motorcycle battery feeding a capable inverter) . Or even no battery? Again this is just a thought experiment to understand the process.

Since the battery can only take so much charge (6 amps?), and there appears to be plenty of surplus power available, I'd hope that my 1200 watt load would be supported by some of the 'surplus' power that isn't sent to the battery.


Does it work that way?

MPPT Controllers
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
wkirby avatar image
wkirby answered ·

The charge controller cannot detect what sort of loads are downstream from it, be it a battery, inverter, light bulb or compressor.
It simply has Voltage targets to aim for and do use whatever PV power is available to maintain that target Voltage. Target Voltages are Absorb or Float for example.
If a 2KW load comes on and there is 5KW of PV available, then the MPPT will produce 2KW in order to maintain its target Voltage.
If the battery Voltage is below the targe Voltage, the MPPT is in Bulk producing 5KW of charge power to the battery and a 2KW load comes on, then 2KW would go to the load and 3KW will go to the battery.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

michael7s avatar image
michael7s answered ·

Thanks @WKirby

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.