Anyone see a problem with paralleling a temp sensor between 2 controllers?

cupcake

Anyone see a problem with paralleling a temp sensor from one Morningstar MPPT-60 to another?  will look like:

temp sensor in battery box ---> controller one ----> controller two.

The leads on the temp sensor wire are hella thin and the screw lugs on the first controller can easily fit an extra 2 wires in them to carry on to the second controller... what sayeth the forum?

-- cuppy cakiey

mcgivor

To the best of my knowledge you cannot share a single RTS with 2 controllers, each must have its own sensor. Morningstar website support has a document that I have seen that points this out.

cupcake

Well I'll be!  Let me check the MPPT-60 manual to see if it will cite you..

mcgivor

This will save you the bother of searching.

cupcake

http://www.morningstarcorp.com/wp-content/uploads/2014/02/RTS.IOM_.Install_sheet.07.EN_.pdf

No mention of it being a problem in the link (manual) above..

So can anyoen verify if its ok to parallel one sensor to signal two controllers?

?

cupcake

Fudge... found my answer:
"A single RTS CANNOT be paralleled or shared between multiple controllers."
SOURCE: http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/

CASE CLOSED!

mcgivor

The PDF states the diagram is for all Morningstar controllers,  See Notes, 3

softdown

Now the curious are wondering why a single BTS cannot serve two controllers.

I also wish they would use sturdier wire on some BTS. There is no way that I am going to try push a telephone jack through my labyrinth of wire going through 12" of various wall materials.

BB.

Generally, they are PTC or NTC (positive or negative coefficient) thermistors (thermal resistor).

Basically, the controller outputs a set current and monitors the voltage. V=I*R... The measured resistance changes with temperature.

If you put two controllers in parallel, then current is 2x higher. I would assume that the calibration would be wrong. Also, as you pump more current into the resistor, you would get self heating too.

-Bill

Dave Angelini

Adding to Bill   If the controllers are on a network, generally most brands Outback, Schneider, and the Morningstar mppts usually need only one BTS. Sometimes they discourage multiple sensors!
 The diagram does not mention a network connection. Maybe Mike can update this as he uses Morningstar.

BB.

With "systems" (charge controllers, inverters, etc.) that are networked together (Outback, Schneider, and others), they "digitally" share the sensor data--Not the actual physical analog (voltage/current) interface to the sensor.

If digitally sharing sensor, double check the programming is correct--It is very possible to think that the multiple devices are sharing temperature data and find out they are not.

-Bill

Dave Angelini

Disagree Bill,  with Schneider and Outback systems. There is not programming to do this BTW. If you remember back in the day people with these systems were saying that only one device had the correct temp. They would then place a sensor on each device and sometimes this caused unexpected results. The manuals clearly tell you that only one sensor is required if networked.

One of the unexpected results was it caused some overshoot during absorption in AGM's that really upset some folks.

The word doc below is the only way I know to verify that a system is sharing temp data other than a BMS that looks at each cell in the Outback and Schneider Li-ion systems in mid 2017. One would verify this data with AGM's yearly to make sure they do not overvolt these batteries.

cupcake

..just got done setting up mah 2nd morningstar mpt-60 and both controllers have their own separate RTS - and ALL IS GOOD!

mike95490

mcgivor said:

To the best of my knowledge you cannot share a single RTS with 2 controllers, each must have its own sensor. Morningstar website support has a document that I have seen that points this out.

I've not seen that doc, but I've not found any setting that allows sharing of a single sensor,  so Morningstar needs 1 sensor for each controller.

mcgivor

The information about not sharing was from reading all documentation relevant to Morningstar controllers, as that is what my system uses, thought it was a good way to educate myself. The PDF on post #4 is where it stated use seperate RTS for each controller and applies to all Morningstar controllers, other controller manufacturer's may differ.

cupcake

mike95490 said:

mcgivor said:

To the best of my knowledge you cannot share a single RTS with 2 controllers, each must have its own sensor. Morningstar website support has a document that I have seen that points this out.

I've not seen that doc, but I've not found any setting that allows sharing of a single sensor,  so Morningstar needs 1 sensor for each controller.

SEE the link in post #6 for the source...

-- cc