100 Watt HQST Panel Comparison

[brorob]

Hello everyone. I am getting ready to order 4 panels for a camper setup and have decided on HQST panels based on reviews and price. They have two different 100W mono panels that have different dimensions, one is 20" x 42" and the other is 26" x 32". The shorter/taller panel has higher operating and short circuit volts but less operating and short circuit current than the other panel. Either panel will work with my setup but I'm wondering if I will get better output with one based in their output.

Thanks for any light you can shed on this.

 

[Short_Shot]

Personally I'd get the higher voltage ones.

But they'll both pretty much do the same job.

 

[Whinny]

If you will be using a PWM controller go for the higher amp panel. If MPPT it doesn't matter as much, but if you want the panels parallel because of shading issues use the higher voltage. If you are going MPPT larger 200-300 watt panels are usually cheaper per watt but can be problematic for installation real estate....

 

[brorob]

If you will be using a PWM controller go for the higher amp panel. If MPPT it doesn't matter as much, but if you want the panels parallel because of shading issues use the higher voltage. If you are going MPPT larger 200-300 watt panels are usually cheaper per watt but can be problematic for installation real estate....

Thanks for all the info. I have the 40A Epever Tracer MPPT controller and was planning on running 4 panels in parallel since my battery setup is 12V and since my power usage will be fairly small. Our biggest power drain will be an efficient 12V fridge.

I would prefer larger watt panels but most of them are 24V. I understand that MPPT controllers can charge a 12V battery even if 24V panels are connected to it, but does a setup like this result in power loss that would cancel any advantage to this?

 

[Whinny]

No disadvantage at all with an MPPT controller using a higher voltage panel, it is usually more efficient.

 

[RCinFLA]

Second panel says 64 cells but it is actually 64 half cells based on Vmp.

This makes it a 32 series cell panel. 18v Vmp on 32 series cells is a stretch, more likely yielding 15.5-16v Vmp under heating of full sun and may not work well with a 12v LFP battery using a MPPT controller. It may not have enough overhead voltage above battery voltage for MPPT controller.

First panel is 33 cell panel, a little better but still marginal for MPPT controller.

When there is not enough overhead voltage from panel, an MPPT controller will just drop back to PWM mode of operation. If you plan to run an MPPT controller on a 12v battery should go for at least a 36 series cell panel, or run two panels in series.

 

[brorob]

No disadvantage at all with an MPPT controller using a higher voltage panel, it is usually more efficient.

Ok, thanks. This will make me rethink my setup, I'd prefer going higher voltage into my controller so I might do a series-parallel setup.

 

[brorob]

Second panel says 64 cells but it is actually 64 half cells based on Vmp.

This makes it a 32 series cell panel. 18v Vmp on 32 series cells is a stretch, more likely yielding 15.5-16v Vmp under heating of full sun and may not work well with a 12v LFP battery using a MPPT controller. It may not have enough overhead voltage above battery voltage for MPPT controller.

First panel is 33 cell panel, a little better but still marginal for MPPT controller.

When there is not enough overhead voltage from panel, an MPPT controller will just drop back to PWM mode of operation. If you plan to run an MPPT controller on a 12v battery should go for at least a 36 series cell panel, or run two panels in series.

Thanks. Should I still try to stick with 36 or more cells if I'm going to use 4 panels? I may hook them up in series-parallel since I learned I can input 24V to my controller even if my LFP battery setup is 12V. I'm assuming the first panel is 32 cells and 33 was a typo.

 

[Whinny]

Series/parallel can be better if you don't have shading issues, you may get an earlier start to charging voltage and it may go later in the day. One panel partly shaded will bring both series panels down, not so much in parallel. Generally larger panels are higher voltage with multiple diodes to try to offset some shading problems, and are also cheaper. I just purchased a 315 watt cut cell 40ish volt panel for $220 to replace my 2x 100 watt panels. 100 watt panels go for $115-125 or so here...

 

[chrisski]

Any real difference in those two 100 volt panels will be insignificant. If the higher volt one is more efficient in a MPPT controller, perhaps charging will finish 10% quicker, or 6 extra minutes for every hour of sun. If you’re worried about that much efficieincy, time to get another panel, or get a SCC to add a ground array to supplement the roof panels.

One graph I looked at showed the 10% extra coming when MPPT panel voltage was twice the battery voltage. You’d come in a little less than 10% gains because you’d want the panels at 28 volts, if that graph holds true.

Avoiding any shadows from vents and air conditioners and tree limbs and parking the right way will yield you way more than any difference between those two panels. Like Whinny mentioned, a bigger panel, purchased perhaps off Craigslist, may make the Rooftop Puzzle better.

I have 950 watts of panels on the roof and 400 watts of suitcase panels. Because of shading on the roof and my portable panels are angled at abe then moved to point at the sun three times a day, I get more power from that portable panel bank.

 

[brorob]

After thinking about the replies I received I'm considering purchasing 2 of the HQST 190 watt panels instead of 4 of the 100 watt panels. The larger panels have 36 cells, which it sounds like the MPPT controller will like better. I'll reduce my overall potential power by 20 watts but if this is a better setup for my controller then I don't mind. I'm also oversizing my solar power a bit so 380 watts will still be plenty for our needs.

 

[brorob]

I'm now convinced, from everyone's feedback, to purchase a couple of 200 watt panels. With a 12 volt LFP battery setup and an MPPT controller, would it be more efficient to purchase 12 volt or 24 volt panels?

 

[chrisski]

No such thing as a 12 volt or 24 volt panel. If you have a “12 volt panel” it will output around 18 volts. If you have a 24 volt panel it wil output around 33 volts. You may find a Craigslist special or Sant Tan solar panel that does not match those voltages but works just fine. Especially higher wattage panels. They tend to have iutput no more than 10 amps, but voltage goes up so wattage goes up on the bigger panels.

You want to be at lest 17 volts for a 12 volts system, and 29 volts for a 24 volt system. With an MPPT controller you can go over and its fine. There’s an ideal output to match with MPPT to battery, but IMO, its not worth chasing a few minutes less of battery chargign to hit peak output.

 

[brorob]

No such thing as a 12 volt or 24 volt panel. If you have a “12 volt panel” it will output around 18 volts. If you have a 24 volt panel it wil output around 33 volts. You may find a Craigslist special or Sant Tan solar panel that does not match those voltages but works just fine. Especially higher wattage panels. They tend to have iutput no more than 10 amps, but voltage goes up so wattage goes up on the bigger panels.

You want to be at lest 17 volts for a 12 volts system, and 29 volts for a 24 volt system. With an MPPT controller you can go over and its fine. There’s an ideal output to match with MPPT to battery, but IMO, its not worth chasing a few minutes less of battery chargign to hit peak output.

I know that but when you purchase a solar panel they don't list a panel that outputs 17 volts as an 17 volt panel, they list it as a 12 volt panel.

So to be more specific, is it more efficient to use 24 volt panels (that put out 37 volts) than it is using 12 volt panels (that put out 24 volts) for my 12 volt LFP setup?

 

[Short_Shot]

Efficient? Not really.

Higher voltage is more likely to enable the charge controller a bit sooner in the day though. By that metric you might see a slight improvement.

If you're using an mppt controller anyways. You have little choice with pwm and would need the "12 volt" panel.

 

[chrisski]

So to be more specific, is it more efficient to use 24 volt panels (that put out 37 volts) than it is using 12 volt panels (that put out 24 volts) for my 12 volt LFP setup

With my portable setup, I am finding putting as many “12 volt” panels in series asI can without exceeding MPPT SCC limits gets me the best real results, even though there is a lab most efficient rate.

There is a sweet spot for MPPT, and I can’t find that chart now but I remember my MPPT controller being 10% more efficient at twice the voltage. Might have been 2%. I wish I could find that chart again.

I also found that when I put panels out, often they are shaded Which effects the voltage Down. Three of my panels in series put out between 40 volts and 60 volts. When its ideal conditions and the panels are producing almost rated power, the voltage is closer to 55. Takes me 3 “12 volt” panels in series to get those voltages.

The MPPT controller also needs 5 volts over battery to start, and 1 to continue to charge. My 24 volt battery voltage can get to 28 volts, so it would need 33 volts to start charging.

Most of the time, two ”12 volt “ panels in series would work, but I would lose some early morning charging or some late afternoon charging.

 

[Short_Shot]

I guess I stand corrected on efficiency. That makes sense as petty much any power supply has a certain efficiency curve based on voodoo magic and wizards with long beards and big calculators.

 

[Mia]

Second panel says 64 cells but it is actually 64 half cells based on Vmp.

This makes it a 32 series cell panel. 18v Vmp on 32 series cells is a stretch, more likely yielding 15.5-16v Vmp under heating of full sun and may not work well with a 12v LFP battery using a MPPT controller. It may not have enough overhead voltage above battery voltage for MPPT controller.

First panel is 33 cell panel, a little better but still marginal for MPPT controller.

When there is not enough overhead voltage from panel, an MPPT controller will just drop back to PWM mode of operation. If you plan to run an MPPT controller on a 12v battery should go for at least a 36 series cell panel, or run two panels in series.

How does one set up 2 pairs of solar panels ( in 2 series and 2 parallel configuration) for a 12 v system and only one solar charge controller (and we also have a dc dc charger and the inverter and generator, everything is 12v…) - is this possible or would we need another solar charge controller?

 

[Mia]

How does one set up 2 pairs of solar panels ( in 2 series and 2 parallel configuration) for a 12 v system and only one solar charge controller (and we also have a dc dc charger and the inverter and generator, everything is 12v…) - is this possible or would we need another solar charge controller?

I’m continuing to learn so much more of the finer details after the fact and after the initial purchases that might not have worked out as well as what we initially had expected…

 

[Mia]

I’m continuing to learn so much more of the finer details after the fact and after the initial purchases that might not have worked out as well as what we initially had expected…

We stuck with 12 v system as that’s what was already in place. But now I’m wondering if that’s really the best option, as the panels are not generating anywhere close to what we had anticipated. And with the very limited rooftop space on the truck camper, and the investment in the 520 amp hr battery capacity we now have, I’m thinking that the solar is not capable of keeping the batteries topped off let alone give us the ability to use the dc electric while the suns out. (Thankfully, we have been driving a lot, and the dc dc charger has been working awesome! We are running the fridge off of it much of the time and the batteries seem to be staying at 100%.) But the plan was to stay at a place for a month at a time and not need to use shore power if we can avoid it since we had installed solar. Right now we only have installed 2 100 watt HQST panels in parallel…but it’s no where close to even generating half of the expected watts (its not even reaching 80 watts let alone 180 watts) and we have 2 additional 100 watt panels we can add, so maybe if we do 2 series and 2 parallel that will help … plus we can’t go over 400 watts as that’s the limit of the Epever tracer 30 amp SCC we have currently…