Tristar -60 MPPT not as advertised?

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Tristar -60 MPPT not as advertised?

Postby kemills1 » Sat Aug 29, 2015 8:22 pm

Five days ago I purchased a Tristar 60 MPPT charge controller. I researched long and hard for a controller that would fit my needs and according to the specs and operation manual, this seemed to fit the bill. Having used it now for five days and having spoken to Morningstar, I not so sure.
The problem started when I noticed every day an alarm event would occur (high array voltage current limit). Concerned, I contacted Morningstar who initially told me it was current limiting the battery amps to 60A as this was the internal limit set by the controller. I pointed out the array was 1400Wp and the max current I'd observed was no more than 45A at which point they asked for the log files which I duly sent. What they then told me was that because the array voltage was above 115V (Voc is 126v), the controller was cutting back on the amps and this was when the alarm was triggered.
This reply contradicts what's written in the operation manual which show, in the deratings section, a graph showing full current up to an array voltage of 140v. The same section also shows derating for heatsink temp which starts at 80C (mine gets up to 60C).
Has anyone had a similar experience with this controller?

Kev.
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Re: Tristar -60 MPPT not as advertised?

Postby Gordon-Loomberah » Sat Aug 29, 2015 9:41 pm

kemills1 wrote:This reply contradicts what's written in the operation manual which show, in the deratings section, a graph showing full current up to an array voltage of 140v.


I'm assuming you have a 24V battery.
Looking at figure 8-7 Battery Current vs Array Voltage on p60 of the manual, current is de-rated for voltages over 115V, which you appear to have. Current is limited to 40A @125V. The 150V so prominently displayed throughout appears to be the maximum voltage it can withstand without damage, rather than an operating voltage. It appears to be performing to spec, so if you can operate at a lower array voltage, the current limiting problem should disappear.

How do you have your panels configured, and what are their specs?
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Re: Tristar -60 MPPT not as advertised?

Postby kemills1 » Sat Aug 29, 2015 10:55 pm

Hi Gordon,
we must have different manuals as fig 8-7 on page 60 shows 60A until Array voltage reaches 140V.

Document ID on the back page is MS-ZMAN-TSMPPT-01 v02 12/2009. What's yours?

Kev.

Just looked at the online manual and yes, derating starts at 115V.
I'll get the specs for my panels....
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Re: Tristar -60 MPPT not as advertised?

Postby Gordon-Loomberah » Sat Aug 29, 2015 11:07 pm

Hi Kev, I don't have one myself, I was looking at the online version, which you have now seen.
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Re: Tristar -60 MPPT not as advertised?

Postby kemills1 » Sat Aug 29, 2015 11:47 pm

Hi Gordon,
I have 7 panels arranged as

String 1: 4 X Conergy Panels Vmpp = 29V Voc = 36V, Impp = 7.8A == 116Vmpp 144Voc
String 2: 3 X Luxor Panels Vmpp = 35V Voc = 43V, Impp = 5.0A == 105Vmpp 129Voc

This was the best configuration I could get with the panels I have. I would have thought the combined Vmpp would have been within the 115V limit of the controller.

Kev.
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Re: Tristar -60 MPPT not as advertised?

Postby Gordon-Loomberah » Sun Aug 30, 2015 9:15 am

kemills1 wrote:String 1: 4 X Conergy Panels Vmpp = 29V Voc = 36V, Impp = 7.8A == 116Vmpp 144Voc
String 2: 3 X Luxor Panels Vmpp = 35V Voc = 43V, Impp = 5.0A == 105Vmpp 129Voc


60 cell and 72 cell panels don't generally go together very well in parallel short strings. In cold weather Vmp can be higher than rated, although I don't know where you are, so that may or may not be contributing.
However, you are going to have problems with that mix and arrangement of panels in cold weather, but you may avoid the derating problem when the panels are hot, although it is still far from ideal, with a 10% Vmp mismatch.

I'd think about changing the Conergys to 2 strings of 2 panels, and having a string of 2 Luxor panels in parallel with that. It will avoid the high voltage derating, but you will have a panel left over, and you still have the 60 -72 cell panel mismatch problem.
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Re: Tristar -60 MPPT not as advertised?

Postby kemills1 » Sun Aug 30, 2015 5:38 pm

Hi Gordon,
I've configured the panels as you've suggested so we'll see how it goes, maybe I'll actually harvest more power if the controller is not derating.
I was wondering though if you know of a charge controller which doesn't derate so much with array voltage as I may be able to return the Tristar.
It does get pretty cold here (around-10C) in the winter and I had planned on fitting a voltage clamp to the array to prevent it going over 145Voc

Kev.
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Re: Tristar -60 MPPT not as advertised?

Postby Gordon-Loomberah » Sun Aug 30, 2015 6:36 pm

Outback FM60 or FM80 will both work at Voc up to 145V, and Midnite Solar models do 150, 200 and 250V max.

I think we have some FM60s on clearance ATM.

Make sure you use temperature compensation on the voltage set points if you get temps that low and the battery temp can vary by more than ~5C from 27C.
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Re: Tristar -60 MPPT not as advertised?

Postby Privatteer » Sun Aug 30, 2015 8:22 pm

600V version.
Have not looked into it much so the Outbacks might be cheaper.
http://www.morningstarcorp.com/products ... mppt-600v/
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Re: Tristar -60 MPPT not as advertised?

Postby kemills1 » Sun Aug 30, 2015 8:30 pm

Hi Privatteer,

I've looked at the 600V version but it's a bit pricy for me.

Kev.
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