More Solar for "Us"

[MrWizard]

Ok, I went off.the deep end?
Bought 3 used 37watt uni-solar panels and a blue sky 2000e controller for the hefty price of $400,
They were being listed as 75w panels, they are not

The tested open circuit voltage was 21+, short circuit amps 2.9
I tested each panel multiple times tilted into the sun and laying flat on the ground , got the same readings each way, that was the deciding factor, they appear to put out full power while laying flat, I will try to mount them tomorrow before it gets hot, right now 104°F
I will use the existing wiring until I buy & install the new wire

[CA_Traveler]

Almot wrote:

Yes, lower cost of PWM is TAD offset by the number=cost of panels and a bit more wiring pains. What annoys me is that PWM are not as "automated" as MPPT.

It's been awhile since I compared larger RV solar systems. So here is todays comparison:

Solar PWM vs MPPT Cost comparison 1-23-17

PWM
Cynergy 160W $115, 5 panels 800W $575
TriStar TS-60 $183
Installation cost over MPPT $100
Total $858

MPPT
Amerisolar 250W $163, 3 panels 750W $489
TriStar MPPT 60 $483
Total $972

Wow my 750W system cost $1400 without the remote display in 2014!

Based on this I'd make the same decision favoring MPPT today.
.
There are of course many other factors to consider. It seems clear to me from numerous posts that many start with a smaller solar system and PWM is much more cost effective for smaller sizes. And then with upgrades to more solar there is just no practical starting over.

[red31]

wiz, what did ya harvest today :B

[Almot]

CA Traveler wrote:

no brainer choice. ie The MPPT controller cost vs the lower PWM cost was offset by more and smaller 12V panels and installation. Parts cost only was considered. About 500W was the crossover point.

Yes, lower cost of PWM is TAD offset by the number=cost of panels and a bit more wiring pains. What annoys me is that PWM are not as "automated" as MPPT. I'm not enjoying tinkering around my solar, this is not what I'm paying her for :)...

No personal experience with PWM though. From what I see, tapered volts in PWM are "disconnected" from the output amps, not same flexibility as MPPT when it comes to "smart" switching btw Boost/Abs/Float, i.e. auto-adjusting amps and Abs time. Or they don't want to invest in programmability when the goal is to lower the cost and increase sales volume. Can't beat Grape price, and it seems to be real thing unlike ubiquitous $20 Ebay babies.

CA Traveler wrote:

What about MS PWM controllers? No personal experience, just curious.

Those little black boxes with blinking green/yellow lights? They exist and popular, mostly in systems under 400W.

[pianotuna]

CA Traveler I'm impressed with the Grape Controller. My panels were $5.50 per watt in 2005. Lowest retail price I've seen is $0.34 cents per watt.

[CA_Traveler]

My 250W panels dropped $50 in 2 years - ie now about $150.

Haven't seen any drop in quality controllers however.

In 2014 the cost of a PWM system equivalent to my 750W panels with MS MPPT 60 was only $100 more, so no brainer choice. ie The MPPT controller cost vs the lower PWM cost was offset by more and smaller 12V panels and installation. Parts cost only was considered. About 500W was the crossover point.

[CA_Traveler]

Almot wrote:
Don - not "all", but "all this" - meaning things mentioned in the BFL13 post. Shorten the Vabs stage when necessary, adding amps in the Float stage when demand increases. My Rogue MPPT does this. MS MPPT 45, 60 (and 30?) do this. Probably some others too.

What about MS PWM controllers? No personal experience, just curious.

[Almot]

Rogue 30 is too small these days when people install 500+ on their rigs. MS MPPT 45/60 aren't bad too.

About 600W not being enough in winter.
Baja Norte, not much difference from SoCal in latitude, fewer clouds, no such thing as marine layer.
Neighbor on the right - tilted fixed 160W solar, 9 months a year living, older propane fridge without electronic thermostat, laptop, propane heater. No generator. Washer/drier trips to the village once a week. I told him to add more watts so that he could at least run some big fan in summer, he said he'll "think about it". Old people, old installs, they still think of 300-400W as of something big and expensive (it was back then, yes).
Neighbor on the other side - same thing, two people there.
Neighbor across the street - tilted 350W, rotated twice a day to follow the sun, same loads plus satellite TV and i-net.

[pianotuna]

Hi Almot I liked the Rogue. Too bad it is no longer made.

[Almot]

Don - not "all", but "all this" - meaning things mentioned in the BFL13 post. Shorten the Vabs stage when necessary, adding amps in the Float stage when demand increases. My Rogue MPPT does this. MS MPPT 45, 60 (and 30?) do this. Probably some others too.

But, when you can't get "enough", you need to add solar. Or - reduce the load, or run a generator. With 120V fridge in SoCal I would say, at least flat 700W in winter full-time for a single person. No mismatched panels 😉

[pianotuna]

Hi Almot,

Which one "does it all"?

Almot wrote:

...or you can get a controller that will do all this for you. Grape doesn't.

[Almot]

BFL13 wrote:
Some days you want a shorter Vabs time if the batts are bubbling too much, and other days you can't get enough with all the clouds. You have to pay attention every day what is going on with the batteries and how to play the solar settings.

...or you can get a controller that will do all this for you. Grape doesn't.

The situation when you can't get enough is best remedied by getting more solar (plus, a proper controller, there is no way around this) - controller would divert the excess energy to loads when they are bubbling too much.

[MrWizard]

Another note to THIS situation
There is considerable wire between the batteries and the solar controller
And voltage drop between them with loads etc..
To actually get to 14.8v at the batteries , I have to use the adjustable boondocker converter,

[pianotuna]

Hi brulaz,

The batteries in question are sealed surplus acid AGMs so gassing voltage needs to be avoided.

I used to trigger equalization late in the day.

brulaz wrote:
Never thought elevated voltages (upto 14.8V Vabs) to be much of a problem as long as you watch the water in the batts.

Our MPPT can stay in Abs and over 14V for long periods when we're using much electricity during the day. Also it's easy to force into mppt mode, which I'll often do late in the day to get batteries as full as possible before night fall.

[brulaz]

Almot wrote:

BFL13 wrote:
If the controller drops to Float voltage before you want it to, it is very frustrating trying to get it back to Bulk, since the batts have to get down to 13.2 (eg) which can take a long time.

Yes, it would have to go through Absorb again.
No, it won't take a long time if controller is smart enough to shorten the Abs stage accordingly to the current and/or voltage at the beginning of this "new" Abs stage. Those cost more than Grape though.

BFL13 wrote:
If you can program Float to be near the same higher voltage as Bulk, then you are good all day.

Why keeping batteries all day at elevated voltages is good?
...

Never thought elevated voltages (upto 14.8V Vabs) to be much of a problem as long as you watch the water in the batts.

Our MPPT can stay in Abs and over 14V for long periods when we're using much electricity during the day. Also it's easy to force into mppt mode, which I'll often do late in the day to get batteries as full as possible before night fall.

[red31]

Rolls has a simple abs time calculator

4.2 hrs for 10% (10% of C20) charging.

http://support.rollsbattery.com/support/solutions/articles/428-state-of-charge-charging-flooded-lead-acid-batteries