Northstar or Odyssey for trailer/solar application? Other options to consider?

[dwh]

Well, it is sort of old. Latest revision was 2011. That's probably when they converted it to .pdf. I remember it from years before that and I don't think the orinal was .pdf.

Wouldn't surprise me if the tech support guy hadn't heard of it.

 

[ajmaudio]

Re the operating temperature of the Morningstar Sunsaver Duo, here is the response I received today from Morningstar Tech Support:

I had a discussion with Engineering about your proposed use of the Sunsaver Duo. As stated in the Datasheet the maximum ambient temperature for operation is 113F. This particular controller does not have a derate on the charging as it gets hotter. What this means is that the controller would charge at the maximum potential it could based on the supply from the solar input up to the 113F and then it would stop charging. The 113F value is based on maximum charge amperage of 25A. Since you would most likely be charging at lower amperages you would probably see charging at temperatures a bit higher than 113, but exactly how high we could not predict.

Since the controller shuts down the charging once the max temp is reached, the likelihood of the controller being damaged by higher temperatures is very small and highly unlikely. We feel you would be fine to proceed with this installation, knowing that your controller would not charge when it was at the hotter temps.

So, it should work except when I am out in the desert running the fridge, which is when I'd really like it to work. I'll probably try it, because even a few extra ah is better than none. The regular Sunsaver (single) is rated up to 140F, but to properly charge both battery banks I'd have to have two panels and two controllers and that quickly eliminates the simplicity I'm looking for, space considerations aside. But that may be my fallback plan if the Duo just does not cut it.

Hmmm... interesting. I am curious what part of the unit restricts it to 113 degrees. Thats much lower than typical operating temps for transistors etc that would make up the guts of the unit. They say anything that might shed some light here?

 

[dwh]

Hmmm... interesting. I am curious what part of the unit restricts it to 113 degrees. Thats much lower than typical operating temps for transistors etc that would make up the guts of the unit. They say anything that might shed some light here?

Here's a clue, from the manual, Section 4.3 Protections

Damaged Local Temperature Sensor - The local ambient temperature sensor is shortcircuited or damaged. Charging stops to avoid over- or under-charging. This is a critical error.

Damaged Internal Temperature Sensor – The internal heatsink temperature sensor reading is damaged. This is a critical error.

 

[Ducky's Dad]

They say anything that might shed some light here?

Nope. I have had live t-cons with pre-sales support and with tech support, but nothing yet directly with engineering types. There seems to be some level of confusion, or at least uncertainty, about these temp limits. They could not explain why the regular Sunsaver is good to 140F, but the Sunsaver Duo is only good to 113F. My uninformed guess without examining a unit is that the Duo has more stuff packed into a similar case, so less room for cooling. They did tell me to mount with cooling fins vertical to aid in heat dissipation. The sales guy suggested I call one of their big dealers in AZ to see what they recommend, and the dealer said, "we don't know, we just sell the stuff." I also called HandyBob's favorite RV solar installer and they had no suggestions. Could be that no one knows anything because it's not really a problem. Or maybe none of their customers are dumb enough to go to the desert under those conditions. Hmmm...

 

[Ducky's Dad]

My uninformed guess without examining a unit is that the Duo has more stuff packed into a similar case, so less room for cooling.

I just looked at the spec sheets, and external dimensions are a little larger for the Duo compared to the Sunsaver. Sunsaver maxes at 20amps, Duo at 25amps.

 

[dwh]

Both the Sunsaver and the Duo have two internal temp sensors. One to sample ambient for the temp compensated charge voltage adjustment, the other to monitor the heatsink temp.

Looking at the manual for the regular Sunsaver, it says it will disconnect solar/battery when the heat sink temp reaches 85c, which is 185f, and reconnect at 80c.

The manual for the Sunsaver MPPT mentions the temp sensors, but doesn't mention what the temp limits are.


I strongly suspect the 40c number in the Duo manual may be an error.

You could also install a 12v computer fan powered by the LVD load terminals and controlled by a bimetal "snap disk" thermostat.


And, having slept on it, it came to me that the two controllers/one solar trick won't work for you because the single Sunsaver are not programmable and bulk only to 14.4v. Fine for the Optimas, not for the Odyssey.