diy solar

diy solar

Renogy MPPT Solar Charger Connection Sequence.

MorePower!

New Member
Joined
Apr 27, 2022
Messages
1
Renogy MPPT Solar Charger Connection Sequence. The manual states that the battery power must be connected first, then the solar array power, or you will damage the controller. Can one apply both battery and solar simultaneously via relay without damaging the controller?
 
Charge controllers should always have battery power supplied and given a chance to power up fully before PV is connected. For some SCCs this is only true the very first time power is ever applied to the SCC. For some this is true every time power is restored to the SCC.

Renogy is telling you the proper sequence it needs and that violating that sequence will damage the controller. If you want to experiment and risk having to buy another controller, then give it a try. But I wouldn't go against what the manual is telling you.

Out of curiosity, why are you trying to setup a relay to restore both power and PV at the same time? What problem are you trying to solve?
 
I'm trying to do the same thing in my travel trailer. I use a disconnect switch at the battery due to some phantom loads in the trailer (it's stored indoors), so wanted a way to ensure that the panels were never connected to the controller when the battery was disconnected.

I use a Wanderer 10 currently, with a 12VDC relay (10A contacts) wired from the "load" terminals, and set the load terminal setting to "15" (manual). The external relay contacts break the + from the PV.

When the CC's powered on, the load terminal is always off. Pressing the Enter button on the front energizes the load terminals, closing the contact on the relay, and thus connects the PV panel to the charge controller. I've found no ill effects from using the battery disconnect while the PV was active (i.e. - cutting battery and PV power to the CC at the same time). BUT, this has only been in service for a few trips so far, so proceed with caution.
 
wanted a way to ensure that the panels were never connected to the controller when the battery was disconnected
There's no need for this.

When you first connect power to the SCC the PV should not yet be connected. But if both are connected, it doesn't really matter which one gets disconnected first. An SCC might lose power for many reasons while the PV is connected. A fuse might blow, a BMS might shutdown, a user may turn off a master disconnect switch, etc. None of these will hurt the SCC. Just be sure to disconnect PV before restoring battery power.
 
There's no need for this....

I think we're saying the same thing. The intent is to prevent an SCC-PV connection without a battery-SCC connection. That's what the relay does in my circuit.

Without power to the SCC, the relay is open, and there is no connection from PV to SCC. Once powered, the load terminals can be energized (using the Enter button), powering the relay contacts closed, and connecting the PV to the SCC. Could also use a latching relay, but since that functionality's already built into the controller for the Load terminals, I used it instead.
 
It seems illogical that a solar charge controller should fry itself if PV is connected before DC, clearly is this not a design flaw in all controllers? They should be designed to deal with DC & PV regardless of connection / disconnection sequence.
 
It seems illogical that a solar charge controller should fry itself if PV is connected before DC, clearly is this not a design flaw in all controllers? They should be designed to deal with DC & PV regardless of connection / disconnection sequence.
Many SCCs autodetect system voltage the first time it gets any power. If PV is connected first, many SCCs will end up seeing the wrong voltage.

Many SCCs have no problem with PV being connected first, after that initial determination of system voltage. But since some SCCs are cheap and dumb, it's always safer to tell everyone to ensure the battery is always connected first. It cuts down on risk.
 
If I were to try and rig up something like is being discussed, I would want the relay between the PV and solar charge controller to be on a delay so that it engaged x seconds after the solar charge controller was powered up. It may be unnecessary but I would want the solar charge controller online, not in a startup state, when the PV power is presented.

That said, I wouldn't do this in my system. I'm a firm believer in the KISS principle and this is unnecessary complexity. My solar charge controller is rarely powered down. In the past two years I think I cut off power to it three times. That's the solar charge controller for my rooftop panels. The solar charge controller for the ground deployed panels is a different matter. PV power to that solar charge controller is cut either at the breaker or when I disconnect the panel wires. My normal procedure is to flip the breaker first, but I've been known to forget. (MC4 connectors aren't supposed to be disconnected under load.)
 
Back
Top