Hello and Solar Question!

[highwaypirate]

Hello all! I'm Karen, new to the forum, but living with solar for a few years now. I have a question regarding adding more solar:

Currently,.. I have an RD1 CR-V with an Armada 200 watt panel (ARM-200) and a (rather cheap, but super reliable) Canada Proof 30A PWM charge controller. Since I run a diesel heater for winters (-30c is also a good time to camp) and a desktop inside the Honda, I'm looking into upgrading my solar system. The 200W is mounted on top of the vehicle (it's just small enough for one), but I want to add a second 200W panel and have it slide inside the vehicle (installed cross-bars to support the 200W from an earlier setup). My question is... since finding an Armada panel has become impossible in Canada, could I use a 200W panel which has close-ish specifications of my current one? I would like to only use one CC, but will consider getting a second one if it'll make it easier.

Here are the specs of my 200W panel:
Model: ARM-200
Vmp: 19.0V
IMP: 10.53A
Voc: 22.5V
Isc: 11.40A
Max System Voltage: DC715V

Would it be harmful to parallel a 200W panel with slightly different specifications? Thank you!

 

[MisterSandals]

could I use a 200W panel which has close-ish specifications of my current one? I would like to only use one CC, but will consider getting a second one if it'll make it easier.

Yes. Do you know if you will be connecting the second panel in series or parallel? What is max input voltage of your SCC?

If in series, similar amps has less loss (lowest amp panel amp used). In parallel, similar volts has less loss (lowest voltage used).

 

[Rocketman]

Because you have a PWM Charge controller - you need to parallel.

In parallel the amps add and you use the lowest volts.
You only gave the panel specs for the old panel - so we can’t figure the penalty for putting those two panels together (but I would bet the penalty will be small).
Use the Vmp for volts (19.0) and the Imp for amps (10.53a).

Is the PV wire 10awg?

If you paired it with this panel: (I just picked one from Amazon)
Newpowa 9BB Cell 200W Monocrystalline 200 Watt 12V Solar Panel High Efficiency Mono Module RV Marine Boat Off Grid https://a.co/d/6qYMQPx

Vmp 18.6v Imp 10.76a

That would give Vmp (lowest) 18.6v and Imp (add) 21.29a
Giving 18.6 times 21.29 = 396 watts - the penalty for these two panels is 4 watts.

You have a much bigger penalty using a PWM charge controller. If you switch to a good mppt you will get more watts in the battery. Like a Victron Smart Solar mppt 100/30.

 

[highwaypirate]

@MisterSandals I would like to connect the second panel in parallel, although my CC is rated for 30A the manual says to never go over 400 watts (20A), which makes sense to leave some extra room (I like to only use 55-60% of what the CC is rated for).

Just thinking outloud... last winter my 200W panel was hitting 12.9A due to the cold, so maybe a second 30A CC should be used to keep it safe?

As for the maximum voltage... the manual does not have that information.

@Rocketman Yes, parallel is what I'd like to do. I over-sized my wires in the beginning and am using 8AWG wiring (I assumed I'd be upgrading later on). I've looked into MPPT but l like the simplicity of PWM; even at the expense of not squeezing all the power out. But I will consider looking into that link you attached!

 

[MisterSandals]

although my CC is rated for 30A the manual says to never go over 400 watts (20A), which makes sense to leave some extra room (I like to only use 55-60% of what the CC is rated for).

What SCC do you have? Can the charging amps be throttled (set lower than max)?

 

[highwaypirate]

@MisterSandals Its a re-branded Canada Proof 30A PWM (model: CP12V30A); the only way I can throttle down is by changing battery chemistries (AGM= 14.4V; LPO = 14.0V; GEL = 14.1V, etc), but the amps can't be throttled. I'll also look into a CC that is capable of having its settings modified (It's just one of those cheap plug-n-play ones).

 

[Doggydogworld]

I would like to connect the second panel in parallel, although my CC is rated for 30A the manual says to never go over 400 watts (20A),

400W is roughly 30A on a 12V PWM system. Until the battery is nearly full it will pull the panel voltage down to roughly 13-14V. Panels that can put out more than 400W at 13-14V would exceed 30A. That's where the 400W limit comes from.

Your single panel puts out 200W at 19V and quite a bit less at 13-14V. Maybe 150-160W at 25C. So two of them would be 300-ish Watts and something like 22-25A in full sun.

As long as your Isc spec is less than 15A I think you'll be OK with two in parallel. The only gotcha might be cold temps, but that mostly affects Voc and Vmp.

 

[highwaypirate]

@Doggydogworld Ok! That makes sense! Now I'm just wondering... if the 200W panel on top of the vehicle was not tilted during the winters, but the second 200W panel was tilted, would that help keep the panels from pulling over 400W? (with a parellel connection, I mean). This could also make it possible to not have the roof panel tiltable, but permanently mounted instead. For sure to be on the safe side, I'll grab a couple extra CCs in case the power ever does become too much.

I don't mind losing some power while charging; as long as I'm able to get 90% of what the panels are rated for, that'll definitely keep things going.

 

[highwaypirate]

I'd also like to add all of this information is very helpful! Thank you everyone for your inputs! I've had solar for a few years now, but only did a basic setup/install. The extra knowledge is always great to have, especially when living on the road full-time!

 

[MisterSandals]

would that help keep the panels from pulling over 400W?

Its overly optimistic to worry about getting full wattage anywhere let alone up yonder.

as long as I'm able to get 90% of what the panels are rated for, that'll definitely keep things going.

90% might even be optimistic...

I'll grab a couple extra CCs in case the power ever does become too much.

I'd consider gettin an MPPT that will function better with over paneling than a PWM. I am a believer in quality SCCs because its the heart and brains of ever solar system.

 

[Doggydogworld]

@Doggydogworld Ok! That makes sense! Now I'm just wondering... if the 200W panel on top of the vehicle was not tilted during the winters, but the second 200W panel was tilted, would that help keep the panels from pulling over 400W? (with a parellel connection, I mean).

I don't think you'll get near 400W with a PWM controller, even one a cold day with both panels tilted. But yes, keeping one flat would reduce output even more.

If you do buy an extra SCC, consider a MPPT. It'll get you closer to that 400W. Plus you could do some back-to-back tests and share the results here!