How to maximize my Morningstar SunSaver 15 Amp MPPT Solar Charge Controller?

MaineCabin

Hi,

I'm looking for some advice as what solar panel(s) to buy to maximize my Morningstar SunSaver 15 Amp MPPT Solar Charge Controller? Right now I've got a couple of 20+ year old Solarex panels feeding it. They are wired in series and put out 6 amps on a good day. The charge controller feed a 12V golf cart battery bank (4 batteries).

Would it make sense to just retire the old Solarex panels - or - try to add to them?

Basically, I'm finding that the existing panels are not keeping up with my use and would like to get as much panel as the charge controller can handle.

Thanks in advance,
Rich

Cariboocoot

Re: How to maximize my Morningstar SunSaver 15 Amp MPPT Solar Charge Controller?

You've got a problem. Namely four golf cart batteries @ 12 Volts totals about 440 Amp hours. The most the MS 15 MPPT can handle is 15 Amps of current, and that's only about 3.4% peak charge rate. That is not going to work no matter what panels are on it.

The controller itself will take about 200 Watts on a 12 Volt system. It doesn't matter what ones, so long as the input Voltage is above 17 or so and below the maximum 75.

But really you need around 44 Amps @ 12 Volts from about 685 Watts of panel for those batteries, and that requires a different controller all together (or two).

MaineCabin

Re: How to maximize my Morningstar SunSaver 15 Amp MPPT Solar Charge Controller?

Cariboocoot wrote: »

You've got a problem. Namely four golf cart batteries @ 12 Volts totals about 440 Amp hours. The most the MS 15 MPPT can handle is 15 Amps of current, and that's only about 3.4% peak charge rate. That is not going to work no matter what panels are on it.

The controller itself will take about 200 Watts on a 12 Volt system. It doesn't matter what ones, so long as the input Voltage is above 17 or so and below the maximum 75.

But really you need around 44 Amps @ 12 Volts from about 685 Watts of panel for those batteries, and that requires a different controller all together (or two).

Thanks for the response.

Could you explain why I really need 44 amps @ 12V? You mean for an ideal system? I'm trying to learn as much as I can.

I've been using this system for the last 3 years with great results. This system is set-up in a summer camp I use on weekends. The solarex panels will have the batteries charged when I get there on a Friday and the battery power will last all weekend.

I've just recently installed a hot water heater (gas) and started using the water pump more. So I was just thinking about adding as much panel as I could. Any specific brand/model you would buy if it was your system?

Thanks.

Cariboocoot

Re: How to maximize my Morningstar SunSaver 15 Amp MPPT Solar Charge Controller?

Yes: the 10% peak charge current is a good "target" to try for. It usually brings everything else in-line, providing the batteries aren't discharged too much (works best with a 25% DOD). From your first post:

Basically, I'm finding that the existing panels are not keeping up with my use

There you have it in a nutshell; not enough panel to provide charging and power use at the same time.

Although your existing panels can recharge while you're away, once you're there they can't keep up with the first day's demand, let alone the second. Right now your charge rate is less than the recommended minimum of 5%; even bringing it up that far would be a help. It is a shame to put in a big system for occasional weekend use.

An alternative solution is to have a larger battery bank so that it can "power you through the weekends" and enough panel to hit the 5% minimum during weekdays.

Another solution is a small, portable generator that can boost the batteries as needed.

What is the Wattage of your existing panels?

As for specific brands of panels, there are very few that are actually "bad". Mostly it's a matter of how much $ per Watt and staying within the parameters you can use (there are a lot of GT panels that have "oddball" Vmp which don't work well on off-grid systems without an MPPT controller, but that is not as much of a problem for your case).

MaineCabin

Re: How to maximize my Morningstar SunSaver 15 Amp MPPT Solar Charge Controller?

Cariboocoot wrote: »

Yes: the 10% peak charge current is a good "target" to try for. It usually brings everything else in-line, providing the batteries aren't discharged too much (works best with a 25% DOD). From your first post:



There you have it in a nutshell; not enough panel to provide charging and power use at the same time.

Although your existing panels can recharge while you're away, once you're there they can't keep up with the first day's demand, let alone the second. Right now your charge rate is less than the recommended minimum of 5%; even bringing it up that far would be a help. It is a shame to put in a big system for occasional weekend use.

An alternative solution is to have a larger battery bank so that it can "power you through the weekends" and enough panel to hit the 5% minimum during weekdays.

Another solution is a small, portable generator that can boost the batteries as needed.

What is the Wattage of your existing panels?

As for specific brands of panels, there are very few that are actually "bad". Mostly it's a matter of how much $ per Watt and staying within the parameters you can use (there are a lot of GT panels that have "oddball" Vmp which don't work well on off-grid systems without an MPPT controller, but that is not as much of a problem for your case).

Thank you!.....