Series PV with 12v Battery

[porkchopmountain]

Newbie question. Can you wire up two solar panels that have an "optimum operating voltage: 20.4v" (so 40.8v) in a series with a 100/30 mppt controller to a 12v battery? I would guess the controller converts that 40.8v down to 12v for the battery?

I ended up purchasing two renogy 100watt panels this past week and a Victron SmartSolar 100/30 MPPT controller. I'm trying to figure out if I should wire them up in a series or parallel. They will be used for camping (panels on the ground, not on a roof) so I will be able to reposition them if needed. I bought the stuff to make them parallel but not sure which route to go. My plan was to have the mc4 y connectors near the panels, plug that into a breaker, run a 10awg wire 10' to the mppt, then have a 2' from the mppt to the battery.

I'm just not sure if the MPPT controller automatically converts the more than 12v from the panels down to 12v for the battery.

Thanks in advanced!

 

[MisterSandals]

I'm trying to figure out if I should wire them up in a series or parallel.

There will likely be little difference other than series getting up to startup voltage (battv +5v) sooner and on low light conditions. Parallel better suited of uneven shading.

I'm just not sure if the MPPT controller automatically converts the more than 12v from the panels down to 12v for the battery.

Yes, of course. This is one of the primary features of MPPTs. Its designed to take up to 100V (not to ever be exceeded) and charge up to 30A (30A x 14V charging = 420W usable).

 

[Pi Curio]

Newbie question. Can you wire up two solar panels that have an "optimum operating voltage: 20.4v" (so 40.8v) in a series with a 100/30 mppt controller to a 12v battery? I would guess the controller converts that 40.8v down to 12v for the battery?

I ended up purchasing two renogy 100watt panels this past week and a Victron SmartSolar 100/30 MPPT controller. I'm trying to figure out if I should wire them up in a series or parallel. They will be used for camping (panels on the ground, not on a roof) so I will be able to reposition them if needed. I bought the stuff to make them parallel but not sure which route to go. My plan was to have the mc4 y connectors near the panels, plug that into a breaker, run a 10awg wire 10' to the mppt, then have a 2' from the mppt to the battery.

I'm just not sure if the MPPT controller automatically converts the more than 12v from the panels down to 12v for the battery.

Thanks in advanced!

Yes, you can wire these two in series no problem. There's even room for more in series if needed, as long it's about 20% ish below 100V limit of the MPPT just to keep it safely below the limit during low temperatures. Also, if you wire them in series, you won't need the Y-MC4 harness used for connecting the panels in parallel.

The MPPT will indeed convert the Solar Voltage down to the selected system voltage, that is, if you set your 100/30 for a 12V battery.

 

[MisterSandals]

Newbie question. Can you wire up two solar panels

Make sure you always have a battery connected before solar and similarly disconnect solar before disconnecting battery.

Think of it as the battery powering the SCC and determining system voltage.

 

[740GLE]

Only down side of series is shading. If both panels aren’t in full sun at the same time out put will be reduced. For a mobile application such as camping I’d say try one panel and see how your usages is.

You running a TV, K cup machine and microwave while camping?

 

[740GLE]

Make sure you always have a battery connected before solar and similarly disconnect solar before disconnecting battery.

Think of it as the battery powering the SCC and determining system voltage.

Not needed for victron, but is great practice in general

 

[MisterSandals]

Not needed for victron, but is great practice in general

Just curious, what happens if i connect a 30V array first (with new unit set to auto battery detect)?
Does it startup as a 24V battery/system?

And then connect a 12V battery, would it switch on the fly to charge in the 14V range?

I'm not surprised the Victron would survive but if the 12V battery gets charged (unknowingly) with 28V, that would be bad and not fall under "not needed for Victron".

 

[740GLE]

Just curious, what happens if i connect a 30V array first (with new unit set to auto battery detect)?
Does it startup as a 24V battery/system?

And then connect a 12V battery, would it switch on the fly to charge in the 14V range?

I'm not surprised the Victron would survive but if the 12V battery gets charged (unknowingly) with 28V, that would be bad and not fall under "not needed for Victron".

The battery voltage is set by the battery or programing, now if you connected a dead 24v that’s showing 18v it may be tricky but I’m guessing it’ll set it for 24v.

 

[porkchopmountain]

Only down side of series is shading. If both panels aren’t in full sun at the same time out put will be reduced. For a mobile application such as camping I’d say try one panel and see how your usages is.

You running a TV, K cup machine and microwave while camping?

Lol, no. I have a 100ah lifepo4 battery. It lasts a good while but I did buy a diesel heater this year. I haven't gone out with it just yet, and I'm not exactly sure how long it will last. It uses at most 4amps an hour on high, so that gives me at most 25 hours, not including glow plug time. I figured that the lifepo4 battery won't work as well in the cold, so it would be nice to top the battery off. My battery does have a heater built into it.
I'll also be using other things than the heater; fridge, but that won't be on much, and charging devices like phones. I also don't expect to keep the heater on high the entire time.

I bought two panels because my calculations shows a little more than 7 hours of sun for a full charge. I would have to double that with just one panel. I may have oversized, who knows...