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Old 03-05-12, 09:44 AM   #1
creeky
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Default mppt controller question

I'm getting ready to head back to the great white north ... and I'm replacing my pwm controller with mppt. (see my solar shed post)

any thoughts about which controller I might buy. currently the morningstar ts-mppt-60 is in the lead.

it'll be running 1000 watts solar into a 12v battery @ 480 amp hrs. with plans to go 2000 watts w/ 48v battery @ 480 amp/hr.

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Old 04-03-12, 09:41 AM   #2
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Well. I was hoping somebody would have some favorite controller options to tout. Have the TriStar MPPT 60 sitting in a box by the solar shed. Will install tomorrow.
How do I delete this thread?
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Old 04-18-12, 03:21 PM   #3
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What was wrong with the PWM controller?
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Old 04-18-12, 03:39 PM   #4
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The PWM worked fine. Only I have 48 volt panels and a 12 volt battery bank.
I am not sure I'm upgrading my battery bank.
So, to get the most out of my panels I needed a mppt controller.
On this note, I now regularly pull 865 watts out of my 1k array and the old PWM only ever saw a high of 335 or so.
I know now that going to a 48 volt battery bank is the most efficient use of my resources (panels, wire, batteries etc). The problem is it comes with the need for more batteries and a new inverter. A good 48 volt inverter/charger is 2000 bucks after taxes and shipping etc.
And the system is working really well. I cannot use all the power I'm generating. Even after two cloudy days: with visitors for supper and using the microwave and watching the hockey game I went out the next morning thinking ... uh oh. Still cloudy. I probably need to cut back. And my panels were making over 300 watts under dark cloud.
I have discovered the disadvantage of L16 batteries. They charge at 15.4 in absorb mode and my Ramsond inverter specs say to go to 15 max. I'm hoping there's some wiggle room there. It's working but am I damaging anything?
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Old 04-18-12, 07:30 PM   #5
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I've seen some 48v inverters specs that would shut them off at 50v..
My 48v bank is up well over 50v in the middle of the night..
Of course, I hardly ever use back-up power.

Hard to say if you are going to damage your inverter. It might be best to keep an eye on it's temperature.
Just try not to run it up near max load, and it might work just fine.

If you do get a 48v bank, then you will have to re-wire your panels to supply the MPPT unit with 96 volts..
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Old 04-19-12, 05:03 PM   #6
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That's one thing I worry about. at 15.4 is the inverter going to turn itself off? There goes my fridge and freezer.

<Speak of the devil. My system just went into “equalize” mode for the first time with the mppt controller. 16Volts for L16s. They are gurgling nicely thank you. Inverter went into OVP and the cottage lost power. Oh. by the end of the cycle they were fizzing every so slightly. neat.>

Temperatures must be okay as the fan rarely comes on. It's a 3000w pure sine (my load peaks 2000? - heater, stove fan and microwave run at once). I'm actually pretty impressed with the Ramsond. I know nothing about their reliability etc, but the inverter appears to be working well. I leave it on 24/7 and the 30 amp line runs my "cottage" nicely.

To the point:
I think Morningstar has some efficiency specs on running higher voltage into a lower voltage battery set up. See the manual p 61/62.
52 vmp to 48 is 99 and a bit efficient at my ideal 1600-2000 watts of solar input. 66 to 48 is 97.8 eff. 98 to 48 is 97.5. So there is some loss in controller efficiency. I would compare that to reduced line losses and copper savings, but I'm lazy. When I look at the chart with my set up I’m well under 2% losses with my wire sizes).

The specs show me to be 95 efficient, drawing my 48 to 12.

I used 6 gauge from the panels to combiner box (8ft). And 2 from there (4ft) with 2/0 for the battery to the inverter (3ft). I wonder if I don’t loose more to connector loss ...

So: I can add 2 batteries and buy a new inverter at 24v for 1400 bucks. Allowing me to add two panels sitting in my trailer and go to 1500w (and increase eff. to 97.5).

Of course it's a simple battery connection to go to 48 (99% eff. @ 48v). But that's a 2600 upgrade with the inverter. I'm not sure I need that size system yet (of course, build it and the demand will come). Beer fridge!

really should be working on my eco toilet, water system and shower ...
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Old 04-19-12, 07:10 PM   #7
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Same problem at 48V.. I set my PWM Morning Star for manual “equalize” mode.
I don't won't it running during a power failure, just when I really need the juice!

I find it kinda funny that inverter makers set up their over-voltage protection circuits
so low, that you have a hard time changing the battery from solar..

AND, even worse they set up the low-battery voltage Shut down to voltages so low,
it's almost sure to damage your battery..
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Old 04-19-12, 08:06 PM   #8
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I hear that. I don't know if it was a typo, but I saw an ad that said the low voltage cutoff for their inverter was 10.9. That's gotta be almost flat.

looking forward to downloading some power logs from the mornignstar. as opposed to my. wow. 11 a.m. and I'm already in "absorb" mode.

the 15v issue came as a shocker to me. I mean really. Solar inverter folks have to know that a lot / most / many? "real" working solar systems are on L16s. Why wouldn't they have made adaptations to allow this use?

Anyway, it's a change to dip switch 7 for me.

(for those without access to a morningstar manual, dip switch 7 will turn equalization from auto to manual)

any new solar gizmos coming out of Xringer labs?
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Old 04-19-12, 09:38 PM   #9
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I think that a lot of these 12v units are made for car batteries.
So, they set the OVP/shut-off at a voltage that's hardly ever seen on a car..
Maybe when they started doing 24, 36 & 48 volt chargers, they just multiplied x 12..?.

I wonder if you could put 6 or 8 diodes in series with your Inverter, to drop it's supply input a bit?? Have to be hefty ones..

My guess is, a very small percentage of the 12V inverters sold are ever used in a PV system.

I have a bunch of stuff on the bench now. Most of it deals with making hot water..
It's going to be a long time before I get to the soldering iron again.

My Solar stuff is working right now, so I'm not going to mess with it.
Just need to repair one blown inverter..

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