MX60 capacity question.

gomango · May 2012

I have an opportunity to purchase 12 more solar panels to add to my system and they are from the same pallet that my original 12 came from. I checked the history on my charge controller and the most I have put out in the last year was 34 amps. My question is if I double the solar array am I going to be OK with the FM60 I am running or do I need to consider an upgrade to an 80Amp controller?

ywhic · May 2012

Re: MX60 capacity question.

I believe anything over 60 amps will just be cutoff.. thats what Cariboocoot told me IRT my Morningstar TS45 controller when I asked about that same thing..

I'm sure he'll be along to claryify this andsome other issues.. like maybe VOC maximums and such..

Cariboocoot · May 2012

Re: MX60 capacity question.

Right now you've got 720 Watts of panel on a 24 Volt system. The FM60 can take double that without issue (60 Amps * 24 Volts = 1440 Watts). It will not output over 60 Amps, and that much panel could produce more than 60 (as you've seen with output from your existing array) but this would only be under certain conditions (cold and clear). The extra power would just be lost (although I think that like its MX predecessor it can be programmed for 70 Amps output).

Likely output: 1440 @ 77% / 24 Volts = 46 Amps

According to the numbers I found, your 6-125-13 batteries are 1182 Amp hours. Is this right? If so, even 46 Amps is not going to be enough to keep them going for long. That would only be about 4% charge rate. I hope I'm wrong about that battery bank size.

gomango · May 2012

Re: MX60 capacity question.

Cariboocoot wrote: »

According to the numbers I found, your 6-125-13 batteries are 1182 Amp hours. Is this right? If so, even 46 Amps is not going to be enough to keep them going for long. That would only be about 4% charge rate. I hope I'm wrong about that battery bank size.

That was one question I had way back when I purchased them. (Had not found you guys at that time) The bank is rated at 750AH at the 6 hour rate, and the MFG suggested that this is the number used to calculate charge rates. I must admit, I have struggled with charging. I bulk them in the winter using the generator at about 55 AMPS. Bulking takes about 3-4 hours to reach voltage and then I hold them at bulk voltage for two hours. In the summer the AGS never runs. If I manually start the generator it will run for about an hour and AGS shuts her down because the solar is able to maintain voltage. I get about 4-6 hours of float a day with the panels I currently have, but the power demands are about to increase in my life. I'm going to buy a washing machine.

I will be adding more panels in the future, but I have to get some things payed off before I can afford another pallet of panels to add plus another charge controller. So for now, I play power cop, and do what I can afford. Adding the other GSA60 panels will allow me to double the current charge current at a price I can afford at this time. I understand from reading in this forum that I will need to grow in capacity a bit more.

niel · May 2012

Re: MX60 capacity question.

i have to ask if it is the mx60 or the fm60 because there is a difference between the 2. the mx60, which is now discontinued, can be software modified to go to 70a. the newer fm60 can't do that.

i'm going to assume it is the fm60 you are referring to and say to go ahead with your pv expansion in any case. if you find the controller hitting max current often and very long then you can get another cc later to reap some of what you are losing if so you choose to do so. remember most pvs will not output their rated max power very often due to the paradox that the solar intensities referenced at stc usually has the effect of raising the pv temperature and stc uses 77 degrees f as that reference. long story short is that you loose power due to heating. other factors could also further effect the lowering of the overall power seen by your pvs so you will have the opportunity to see if another cc will be needed at all.

Cariboocoot · May 2012

Re: MX60 capacity question.

Outback gives the maximum array size for the FM60 as 1680 Watts, so you're safe there no matter what.
I suspect you're getting away with your small array on big batteries because you're not discharging them very deeply. If you were to use them around their full 20 hour capacity (which is the number usually used for RE applications) you'd be in trouble.
Reference to the battery size: GB Industrial http://gbindustrialbattery.com/Forklift_Battery_Sizes_and_Specifications_Zone15.html
The 6-125-13 shows 1182 Amp hours @ the 20 hour rate.

If I were you I'd re-evaluate the battery bank size based on your actual power needs. It might be more prudent to buy different batteries rather than more panels.

The other thing that needs mentioning is that you are piling up a lot of panels. That means a lot of fuses on strings (don't know how you have them configured) and with this plan where you will double the array size you need to check the wire from where the two arrays will combine to the controller as you are about to double the current there. The output current as well.

Aside from that, will the two arrays be pointing in relatively the same direction? If they're too far off it can confuse the MPPT function and you won't get optimum harvest.

Buy large numbers of small panels is a false economy, btw. You could get the same power from three 235 Watt panels @ $1.50 +/- per Watt as from twelve 60 Watt panels. Easier to hook up too.

gomango · May 2012

Re: MX60 capacity question.

The two arrays will be pointing in the same direction and at the same angle. The wires running from the combiner box on the first array is #4 THHN and is running about 60 feet to the charge controller. The second array would need to be about 15' further away.

As for the battery bank side of things... I agree with the notion that I oversized the battery. I have been lucky up to this point and have not had to much of a load to offer it. I am not apposed to downsizing to a more apropriate size, but now I have two hunks of lead sitting here with no home to send them to. This will take some pondering.

Cariboocoot · May 2012

Re: MX60 capacity question.

gomango wrote: »

The two arrays will be pointing in the same direction and at the same angle. The wires running from the combiner box on the first array is #4 THHN and is running about 60 feet to the charge controller. The second array would need to be about 15' further away.

The other thing that matters here is how the array is configured, i.e. what Voltage it's operating at. Those panels probably have a Vmp of around 17.5 so you could in theory run six of them in series * two parallel strings for 105 Volts @ 6.8 Amps +/- ?
If so, doubling the array to provide about 14 Amps @ 105 Volts would still work with 4 AWG over 60 feet.

But much depends on how it is wired now.

gomango · May 2012

Re: MX60 capacity question.

Cariboocoot wrote: »

Those panels probably have a Vmp of around 17.5

The VMP is not given and Im not sure how to calculate the value.
Here is what is given...
Nominal peak power 60
Guaranteed minimum power 57
Nominal voltage 67
Nominal current 0.90
Open-circuit voltage 96
Short-circuit current 1.19

At the moment I am set up in parallel at the nominal voltage. If I went in series with two I could in theory exceed the 150v max on the charge controller.

Cariboocoot · May 2012

Re: MX60 capacity question.

Oh no; those panels. :roll:

Carry on as you were.

gomango · May 2012

Re: MX60 capacity question.

hmmm.... thats not to encouraging.

SolaRevolution · May 2012

Re: MX60 capacity question.

Oh yes, the Kaneka GSA 60.
Great clearance price per watt . Great STC to PTC ratio.
Three times the area. Three times the racking. Three times the labor. Six times the wiring to the combiner panel.

westbranch · May 2012

Re: MX60 capacity question.

perhaps you might want to return to your earlier question of 'do I want to consider an upgrade on the controller'? Look to the Midnite classic, the smallest one is 150V input rated and there are 2 larger models , 200 and 250v models. They are not quite as efficient as the 150 though.

hth

MX60 capacity question.

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