Average 260-300 watt peak output from 640 watt flat mounted array?

[C-Cat]

Yeah I see all kinds of different numbers online for the drop in power production due to the 'angle of incidence' being high.

I saw some numbers around 50% loss when offset by 45 degrees. 

But, most everyone compensates for this, either by installing more panels, or tilting the ones they have.

Yes, I definitely think so... but commercial tilt mounts seem to be awfully expensive for the bit of metal... I wonder if I could fashion my own with pieces from the hardware store!

 

[John61CT]

Lots of DIY mount HowTos out there

 

[C-Cat]

Do you ever get to Float before evening?

How about true 100% Full, looking at endAmps? Likely need shore charging for that right?

How old are the batts? Cycled daily?

Float only when the coach was stored for a few days. On my regular days (using my inverter with that average 120 watt load) I never even see the absorption stage... I always have to run my generator at the end of the day to get a full charge. And yes, I cycle the battery bank down to around 12.25 volts (well, that is under load, maybe around 12.40 after the load has been removed) every night. The batteries are about 5 month old.

 

[C-Cat]

Lots of DIY mount HowTos out there

Cool, gotta look into that. Do you have any particular one that you can recommend?

 

[tx2sturgis]

Yes, I definitely think so... but commercial tilt mounts seem to be awfully expensive for the bit of metal... I wonder if I could fashion my own with pieces from the hardware store!

Well that's exactly what I did on my old Class A....I built up a couple of aluminum 'struts' to tilt my panel up in the winter. 

Cost was maybe $10 (aluminum stock and stainless hardware) and an hour of time measuring, cutting, drilling, and then smoothing the corners and edges.

 

[John61CT]

Wow, here's a tip will change your life.

Or at least double your batt life.

Run that genny in the AM before solar starts.

For now up to 80-85% Full.

Later on batts aren't accepting output, wasting fuel.

You should also be putting a 100A absolute minimum rate charger on 500A AGM. 200+A would be better.

 

[John61CT]

If you see you're getting to 100% Full a bit early, you can start shortening your genny runtime a bit.

You should be doing this 100% Full thong at least several times per week, or you'll be buying a new bank much more frequently.

You likely have already lost a few hundred cycles lifetime treating them this way. A good Battery Monitor would help, voltage is a very poor estimate of SoC.

You probably need 800-1000W panel input to minimize genny usage.

 

[C-Cat]

Wow,  here's a tip will change your life.

Or at least double your batt life.

Run that genny in the AM before solar starts.

For now up to 80-85% Full.

Later on batts aren't accepting output,  wasting fuel.

You should also be putting a 100A absolute minimum rate charger on 500A AGM.  200+A would be better.

Interesting... my current charger (from AC or Generator source) is actually build into the inverter and can supply 50a max which is what, like ~600 watts. So you're saying to rather connect a more powerful charger on the AC side of the generator and charge the batteries with that? Not a short term solution for me right now, but something to keep in mind for sure! Buit I can definitely run the genny in the morning to give the system a head start...

-Chris

 

[John61CT]

I can definitely run the genny in the morning to give the system a head start

Yes, just that change will help, as would running it whenever you have bigger loads.

And anything you can do to reduce consumption, especially getting away from using an inverter. Is that a desktop computer?

But do start saving up for a 200A charger, your bank will thank you.

 

[C-Cat]

If you see you're getting to 100% Full a bit early, you can start shortening your genny runtime a bit.

You should be doing this 100% Full thong at least several times per week,  or you'll be buying a new bank much more frequently.

You likely have already lost a few hundred cycles lifetime treating them this way. A good Battery Monitor would help,  voltage is a very poor estimate of SoC.

You probably need 800-1000W panel input to minimize genny usage.

Well, I don't think (I hope) I abused them that much, since I at least did charge them to full every late afternoon / evening...

I did plan to add more panels too in the future...

 

[John61CT]

I at least did charge them to full every late afternoon / evening.

Really, or so you thought?

Running the genny 4-5 hours minimum?

100% Full for those means holding Absorb until trailing amps falls to 5A, around 2A would be better, or in that neighborhood with current showing no change for a full hour.

Hardly worth burning dino juice for that "long tail" rate

Which is why you want solar doing that end, only use the genny for bulk, and maybe first 2-3 hours of Absorb, as I said, get to 85% before the solar day starts.

And you should monitor your SC make sure it isn't dropping to Float before that endAmps point above is reached.

 

[frater secessus]

Sounds like it's designed really well; lots 'o panels, nice controller, nice batteries.

Oh, oh, could be batteries be in their break-in (commissioning? can't remember the term) period? I seem to remember some of the high-end batts take a few dozen cycles to reach full capacity.

 

[C-Cat]

In any case, I will run the genny also in the mornings now to get the batteries a head-start and I will look into mounting my panels so that they can be tilted (and test them individually). I'll get there eventually, I'm sure...

 

[John61CT]

And test for actual problems as you get a chance as listed above, current sure seems lower than it should be to me for Bulk stage.

 

[willprowse]

Your batteries might be full. Put a large load on the batteries. Discharge them down to like 60% and then put your solar array into full sunshine. Make sure those panels are nice and clean. See how much they produce in that situation.

Feel all wires between the battery and the solar array. If they are warm, you need thicker wires.

Do the solar panels have adequate ventilation?

Honestly most solar panels I test produce only 50-75% of their watt rating in full sunshine.

 

[C-Cat]

Hi Will,

Big fan of your Youtube channel!

Thanks for your feedback, but I think we mostly figured it out... since you mentioned 50-70% of the panel max output rating - that is pretty close to what I'm experiencing, particularly considering these are currently flat mounted and thus can't be tilted for optimum angle (yet... I'm planning to change that in the future ). There is definitely an air gap (double the thickness of an MC4 connector I would say), so temperature shouldn't be the issue. Also, now that I'm running the genny in the mornings too (as John61CT suggested), I am getting through absorption and float by early afternoon when I watch my load. I started this evening fully charged (12.91 volts at rest) and could probably go all night without running the generator again. So all that is working as I would expect it to. I think I just need to add more panels and tilt mounts and I'll be set....

-Chris

 

[willprowse]

Seems about right. My 600 watt system could typically only produce 340 watts in full sunshine here in California. If you are next to the equator, wire gauge is correct and all connections are cool to the touch during charging, I would expect 90% of rated wattage at most. I have never seen a panel produce its rated wattage. They measure the wattage figure in a laboratory.

 

[willprowse]

Hi Will,

Big fan of your Youtube channel!

Thanks for your feedback, but I think we mostly figured it out... since you mentioned 50-70% of the panel max output rating - that is pretty close to what I'm experiencing, particularly considering these are currently flat mounted and thus can't be tilted for optimum angle (yet... I'm planning to change that in the future ). There is definitely an air gap (double the thickness of an MC4 connector I would say), so temperature shouldn't be the issue. Also, now that I'm running the genny in the mornings too (as John61CT suggested), I am getting through absorption and float by early afternoon when I watch my load. I started this evening fully charged (12.91 volts at rest) and could probably go all night without running the generator again. So all that is working as I would expect it to. I think I just need to add more panels and tilt mounts and I'll be set....

-Chris

Thanks man!!! Oh yeah. I just put another reply just now, but just saw your comment. Ohhh I see. Great point about tilt mount for optimum angle. Oh very nice!! Yes let us know how that works out for you! More panels and angle mounts. Nice

Oh that sounds like a good air gap! Gotcha

A fun thing to try is reflecting light onto the panels to increase output. I would build giant mirrors with plywood covered with aluminum foil, and during the winter I produce quite a bit more! Getting the right angle was tough.

 

[John61CT]

If this was a realistic idea for increasing actual charging output, I suspect we'd have been seeing more examples out there. But science projects are fun!

Just realize if you do this, you need good headroom between panel max specs and what the SC will tolerate.

For example an MPPT controller rated for 75V should not have more than 65Voc rated panels attached for normal conditions.

If concentrating sunlight on the panels, voltage may spike much higher and fry your controller, so do your experiments with say 30Voc panels, and even then, no guarantees.

 

[C-Cat]

If this was a realistic idea for increasing actual charging output,  I suspect we'd have been seeing more examples out there. But science projects are fun!

Just realize if you do this,  you need good headroom between panel max specs and what the SC will tolerate.

For example an MPPT controller rated for 75V should not have more than 65Voc rated panels attached for normal conditions.

If concentrating sunlight on the panels,  voltage may spike much higher and fry your controller,  so do your experiments with say 30Voc panels,  and even then,  no guarantees.

Yes, I have also considered reflecting more sunlight onto the panels. As a thought experiment it sounds pretty good and it may even work for winter days when the sun is low, but there are 2 problems: the angle of the sun constantly shifts and building a mirror that you don't have to move every 5 minutes would be gigantic and hugely impractical, not even considering wind loads. Second, there is definitely a possibility for damage, maybe not so much the voltage, but the panel could overheat and take a toll physically. I'm with John here... cool idea, but much less practical than tried and true tilt mounts...

Now engineering a good, cheap tilt mount from off-the-shelf Home Depot parts... that's my next challenge! (Who wants to help? We could document this here and on Youtube! 

-Chris