Full Sun but Power from Batteries?

[pda1]

I'm new to this and my 1 kW (24v) system is running very well.

Here's a curiosity- though there's full Sun and the batteries are charged to Float, when I put a load on the system of 90w, through the inverter, I'm running totally on batteries UNTIL the battery voltage drops to about 27v and then the Panels starting putting power back into the system.

Is there any problem that's occurring in this? It would be nice to run off the panels through the SCC (Victron 150/60) when the batteries are in float?

Thanks,

Peter

 

[upnorthandpersonal]

This is normal - float mode means that the charge controller monitors the battery voltage and only starts charging again when it is below a set voltage. Are you using LiFePO4? In that case (if your charge parameters are correct) the amount of power that will be drawn from the battery is minimal before the charge controller comes back. For example with a 24V system, set absorption to 29V and float at 27.2V. These two represent cell voltages of 3.625V and 3.4V respectively, with 3.4V being just slightly below typical resting voltage. It takes very little to reach float because the amount of energy between 3.65V and 3.4V during discharge is practically nothing:

 

[rmaddy]

I'm not positive on this but this may have to do with the "Re-bulk voltage offset" expert setting for your SCC. The idea is to keep the SCC from trying to bulk charge the battery too soon.

What is your "Float voltage" setting? 27.2V? The "Re-bulk voltage offset" defaults to 0.2V which means it won't start bulk charging until you get back down to 27.0V.

 

[MisterSandals]

through the SCC (Victron 150/60

Can you post screenshots of your settings?

 

[pda1]

Without going into the details, all of the SCC settings are correct per Battle Born so I have no concerns about them. I have 2 Battle Born 12v-100ah in Series for a 24v-100ah "power supply".

 

[efficientPV]

This is the reason I run everything I can directly from the panels. My charge controller spends a lot of time just figuring out what it will do next.

 

[pda1]

This is the reason I run everything I can directly from the panels. My charge controller spends a lot of time just figuring out what it will do next.

How in the world do you do that? Originally I wanted to do the same without any sort of controller, but, I didn't know what I was doing and now understand that a SCC is necessary.

 

[fratermus]

I'm running totally on batteries UNTIL the battery voltage drops to about 27v

...

Note that float is defined as 27v:

View attachment 80794 View attachment 80795

The controller is doing what you've told it to do. {edit: longer answer}