Voltage setting Diversion relay

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Voltage setting Diversion relay

Postby Tytonegro on Sat May 14, 2016 7:46 am

Hi,

I have seen a lot of topics about using the diversion relay in the MX60, but I have never seen my question answered.

First of all I will explain the setup and how I want to use the diversion relay:

We use the MX60 in a setup with solar panels and a small hydro turbine that works with its own controller and dumpload. The hydro controller has a set bulk voltage of 28.8 Volts. When the MX60 tries to equalise the batteries, the hydro controller will desperately try to dump all energy in the dumpload to prevent the voltage from rising above 28.8 V. Of course this is not what we want. Therefore we want to use the diversion relay option in the MX60 to signal when the MX60 gets above 28.8 V (for example when equalising) to disconnect the hydro from the battery, dumping its excess energy to its own dumpload, without interfering with the MX60.

My question is:

The manual talks about setting the threshold voltage *relative* to the bulk-float-equalise voltage. Euhh... ? Yes, but which of the three??? In our setup the volages are set as follows:

Vbulk = 29.5 Volt (Rolls specs)
Vfloat = 27.2 Volt
Vequalise = 30.5 Volt

What does the relative voltage setting do? When will the relay switch when Vrel= 0.0 V ? At 29.5, 27.2 or 30.5 ?

I'm kinda puzzled that I haven't seen this question been asked and answered before.

Thanks,

Tom
Tytonegro
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Re: Voltage setting Diversion relay

Postby mbruvry on Sat Feb 10, 2018 11:29 am

Dang Tom,
No replies! I have the exact same question... After 22 years I have finally got everything setup, except for this part.
Did you ever get your question answered?
Did you give up on getting answer and figure it out?
Regards,
-Marc
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My RE system: 6- 280Watt solar panels, 8- L-16's, MX-80, Trace 4024, Harris 'old style' (with brushes) Pelton Wheel, EnerMax controller (with dump load), Ananda Power Center distribution panel. 24V system.

Re: Voltage setting Diversion relay

Postby Tytonegro on Sat Feb 10, 2018 12:12 pm

mbruvry wrote:Dang Tom,
No replies! I have the exact same question... After 22 years I have finally got everything setup, except for this part.
Did you ever get your question answered?
Did you give up on getting answer and figure it out?
Regards,
-Marc

Nope, no answer.
Since I did not own the mentioned installation, I did not bother that much about finding the answer.
I your case: when you have this setup, could you not just try and play with different settings and see what happens?
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Re: Voltage setting Diversion relay

Postby mbruvry on Sat Feb 10, 2018 4:50 pm

Hi again Tom,
Yeah, I guess that's what I'll have to do. The way I have it now is the EnerMaxer is set about 0.1v above the absorb voltage on the MX80.
When I leave I'll just turn off the Pelton wheel input and divert the water into the river. I shut everything off when I go, so there is no drawdown and the solar can easily keep everything up to snuff.
Thanks for your reply.
Best,
-Marc
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My RE system: 6- 280Watt solar panels, 8- L-16's, MX-80, Trace 4024, Harris 'old style' (with brushes) Pelton Wheel, EnerMax controller (with dump load), Ananda Power Center distribution panel. 24V system.

Re: Voltage setting Diversion relay

Postby gtarolli on Wed Feb 14, 2018 9:35 pm

I did some experimenting with the Diversion relay mode. I didn't hook anything up to the relay, but was just observing how it works. I will soon use it to control an electric hot water heater to pre-heat my water once my batteries are charged and run AC and/or dehumidifiers.

What I found was that the diversion relay turns on once the controller is in Absorb, Float, or EQ mode and the voltage is Vrel above (or below if negative) the respective Absorb, Float, or EQ voltage. Unfortunately, as I reported in another thread, the "Charged" or "Silent" state does not count as one of these modes, so if you have multiple controllers and one is in Silent mode, this might mess things up. What I have done is set one controller to be in Absorb mode 6 minutes longer than the other. That controller is almost always the one that goes Silent as the other transitions from Absorb to Float a few minutes earlier and then the charge controller coordination switches the laggard to float and then to Silent.

So getting back to the question, let's say Vrel =0.1v, then for your example voltages below, the relay would turn on Delay time after you are in either Absorb, Float, or EQ modes and also .1 volts above that voltage. If the voltage then drops Hyst volts the relay will shut off (after HOLD time).

Vbulk = 29.5 Volt (Absorb voltage)
Vfloat = 27.2 Volt
Vequalise = 30.5 Volt

So if Hyst is .3 volt, and Vrel=0.1v then the relay should first turn on when you are in Absorb mode and the voltage reaches 29.5+.1 or 29.6v. If the voltage drops below 29.3v in Absorb mode then it should turn off. I do not know if it will turn on again after it turns off, I have not done that experiment.

After your absorb time limit is reached, the system should switch to Float mode, and the relay should be on if you are above 27.3 volts which should easily be met since the voltage would have been 29.5 or above in Absorb mode and when it switches to float, the voltage will slowly drop down approx 2 volts over a number of minutes. Then if the voltage drops below 27.0v the relay should shut off (allowing the hydro to help the PV array to get back to the float voltage).

In your comment, I think you wanted to say when the MX60 gets above 30.5v when equalising you want to disconnect the hydro from the batteries. This diversion mode should do that, but you should verify that if the PV output drops and the voltage drops and the relay turns off, that it will turn back on again.

Note you can test this out without hooking up a relay - the Mate3 shows you the state of all the relays (1 in each charge controller, 2 in each inverter, and 1 in FlexnetDC), so you can observe them.
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