Question for all you solar experts

[69_Avion]

I have ordered a 250 watt Sharp 24 volt Solar panel. Now for my question. I would like to use a Morningstar Sun Saver 15 MPPT controller. The problem is that the sales person said that the 15 amp MPPT Sun Saver controller isn't large enough for my panel. Does anyone have experience with this? I don't want to have to go to a 45 amp controller unless I absolutely have to.

[ktmrfs]

69 Avion wrote:
I have ordered a 250 watt Sharp 24 volt Solar panel. Now for my question. I would like to use a Morningstar Sun Saver 15 MPPT controller. The problem is that the sales person said that the 15 amp MPPT Sun Saver controller isn't large enough for my panel. Does anyone have experience with this? I don't want to have to go to a 45 amp controller unless I absolutely have to.

He's correct. 250/13=20A that's what the controller will try too dump as a maxx into the batteries. I have the sunsaver 15 controller,wonderful controller but not for a 250W panel.

[brulaz]

I vote for the Rogue 30A
Designed and manufactured in Oregon
I've always wanted one. Maybe someday ...
Rogue MPT-3048

[69_Avion]

westend wrote:
The Morningstar MS-MPPT-15 will clamp output at 15 A. If you exceed the input up to 70 V, IIRC, the maximum output will still be 15 A. With two 24V nominal panels in series you may be exceeding the high voltage rating, depends on panel voltage maximum and if you connect them in parallel or series.

I use this controller with a single 235W panel. It performs excellently. The RS232 interface is a seamless way to adjust charge voltages and observe charging characteristics. When I plotted my system, I took into consideration adding another panel. I decided I could, at that future point, add another controller if needed. As it has turned out, the single panel meets my charging needs. One surprise to me is that these polycrystalline modules will still be harvesting power on the shoulder hours of the day. Mine harvests even at sundown, albeit at very low amperage output. It is "the little controller that could".

I wish that it was a 20 amp controller. The solar supply salesman said it was too small for my panel. I may try the Eco-Worthy just to see if it will work.

[westend]

The Morningstar MS-MPPT-15 will clamp output at 15 A. If you exceed the input up to 70 V, IIRC, the maximum output will still be 15 A. With two 24V nominal panels in series you may be exceeding the high voltage rating, depends on panel voltage maximum and if you connect them in parallel or series.

I use this controller with a single 235W panel. It performs excellently. The RS232 interface is a seamless way to adjust charge voltages and observe charging characteristics. When I plotted my system, I took into consideration adding another panel. I decided I could, at that future point, add another controller if needed. As it has turned out, the single panel meets my charging needs. One surprise to me is that these polycrystalline modules will still be harvesting power on the shoulder hours of the day. Mine harvests even at sundown, albeit at very low amperage output. It is "the little controller that could".

[69_Avion]

JiminDenver wrote:
Do you go up in altitude? My 230w panel sees a increase of over 50% at altitude, you may be loosing more than you think.

I've had good results using the Eco-worthy 20a MPPT controller with a single panel. I was hoping one of the really low cost ones would at least functions but no luck so I'll be getting a second Eco-worthy for the inverter bank.

Jim, how has your Eco-Worth MPPT controller been working? It is the only one that I can find in the 20 amp range. It appears that it will work well with my 250 watt, 24 volt Sharp panel. The price is certainly better than the others as long as it actually is reliable and it works. Let me know what you think.
I may buy two panels since there is no extra shipping for the second panel and then just buy a second Eco-Worthy MPPT controller. I like the fact that it is reasonably sized. When you go to the Morningstar TriStar MPPT 45 amp controller, it is huge for RV usage.

[KD4UPL]

Strictly by the numbers (250 watts/ 14.4 volts = 17.36 amps) that controller is not large enough.
In the real world it will probably work fine since it limits the output to protect itself. The drawback is that during periods of intense sun and/or low battery you will be loosing power.
Morningstar makes some great charge controllers. I've got two of the their 45A models installed at 2 different off grid cabins. I've had no problems from either. Blue Sky is another brand you should investigate. I've got even more of their controllers installed, also with no problems.

[time2roll]

69 Avion wrote:
Lets hear from the folks that have the Morningstar Tri Star 45 amp MPPT controller.

I have the 60 amp driven by three 225w panels. In hindsight the 45a would have been fine even though Morningstar recommended the 60a. I really like the programmability of the 60a so all is good.

[2oldman]

69 Avion wrote:
With two of these panels working at optimum level, what size 110 volt inverter could it power through the batteries with minimal loss from the batteries during the optimum level?

34 x 13= 442w. It will power any size inverter, but it will not support more than 442w draw from that inverter.

So I guess you could say about a 500w inverter. The easier way is to simply think of it as having 2-250w panels for a total of 500w.

[JiminDenver]

Do you go up in altitude? My 230w panel sees a increase of over 50% at altitude, you may be loosing more than you think.

I've had good results using the Eco-worthy 20a MPPT controller with a single panel. I was hoping one of the really low cost ones would at least functions but no luck so I'll be getting a second Eco-worthy for the inverter bank.

[69_Avion]

I may just order two panels since the second panel has free shipping. Has anyone used the Morningstar Tri Star 45 watt MPPT controller? If one 250 watt 24 volt panel is good for about 17 amps then two should be good for 34 amps which means with two of these panels I should just go right to the 45 amp MPPT controller.

Lets hear from the folks that have the Morningstar Tri Star 45 amp MPPT controller.

With two of these panels working at optimum level, what size 110 volt inverter could it power through the batteries with minimal loss from the batteries during the optimum level?

[SteveAE]

I use the Morningstar 15 MPPT with 300 watts of panels. This usage is permitted by Morningstar. Maximum output is just under 15 amps. Works great for me as am looking to optimize low light output and could care less about losing a few amps when the sun is high and bright. The controller is even more efficient at the higher (24) volt input. Should be a great system for you as long as you are happy with ~15 Amps.

Steve

[2oldman]

harold1946 wrote:
The MPPT controller receives the 24 volt input from the panel and adjusts it to 12 volt without reducing the amps.

It would have to increase the amps, right? If it doesn't, better get a better controller.

[harold1946]

2oldman wrote:

CA Traveler wrote:
MPPT controllers take the input voltage and current and convert it to the output voltage and current. He can possibly get 17A output

I think I'm confused in that he's charging at 12v, not 24, so the 15a still holds.

To say it in another manner;
The MPPT controller receives the 24 volt input from the panel and adjusts it to 12 volt without reducing the amps.
Thats the readers digest version. It would take several pages to cover everything involved.
Read Handy Bob Blog.

[2oldman]

CA Traveler wrote:
MPPT controllers take the input voltage and current and convert it to the output voltage and current. He can possibly get 17A output

I think I'm confused in that he's charging at 12v, not 24, so the 15a still holds.

[hmknightnc]

The MS Sunsaver MPPT automatically clams itself to 15 amps max output. You can put whatever size 24 volt panel you want to it. The technical libary on the MS website has a very good description of this capability and even provides examples of where exceeding the controllers nomimal max input solar power is a good thing.

Go For it, the controller is designed to do exactly what you are looking for