mppt vs pwm

brulaz wrote:

BFL13 wrote:
The $102 Eco-Worthy MPPT 20a controller has an adjustable high set point to reach Vabs, an adjustable Float, and the voltage that triggers a return to MPPT is not adjustable but is 13.2v.
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When the trailer is in storage or on 110V, I set the float back to 13.2V (the same float V as the Progressive Dynamics charger when on 110v). That seems to work fine with little water loss over long periods although I think my batts call for 13.1V

But when boondocking, I appreciate being able to set the float higher (13.6V) so MPPT kicks in earlier at a higher voltage. Have been told that the higher "float" voltage should not be a problem for the batteries as they'll be all night without any charging.

So far this has worked well. But I suppose it could set it even higher when boondocking and the Rogue kept in MPPT as much as possible.

I don't follow. If you are camping, when would you ever want to be at a Float (to me that means a non-camping maintenance level) voltage during daylight hours? You are in Bulk from morning till you get the batts to your Vabs, then the MPPT drops out of play and you go into (call it whatever your controller calls it--Absorb or Float--means the same thing to some) till dark, then voltage falls off for the night.

Now the issue while camping after you get to Vabs, is what voltage do you want till dark and how long will that be?

If you can control that and know what the batteries "need" that's what you set. Or the controller might only let you set the voltage for that period (called various names, but we say Absorption Stage) Or the controller might have a fixed charging profile like the EP Solar ones do (LandStar PWM and Tracer MPPT) which is to get to 14.6v, hold that for two hours, and drop to 13.8 till dark, no adjustable anything. (Actually I had the LandStar and that profile was pretty good since it usually never got to the 13.8 part before dark in my situation)

I have no idea what this concern about falling out of MPPT early is due to clouds coming in. Impossible. You are in MPPT till you get to Vabs. If a cloud goes by setting you back in voltage, you are still in MPPT because you never got to Vabs yet If it happens after you get to Vabs then you are already out of MPPT until voltage drops to 13.2 or whatever yours is, when MPPT kicks back in.

So anyway, IMO you set the voltage and the time for your Absorption Stage to what you need it to be (even if the controller setting for that is called "Float" and never mind actual Float Stage voltages until you finish camping and now just want to maintain the batteries. Now you can set the voltage for that job until you go camping again.