Morningstar Relay Driver

tnhunter · September 2007

I am looking to possibly purchase the Morningstar Four Channel Relay Driver to start my two wire start genset.

If I am wanting to use a relay to start the generator, would I be able to control the relay via channel 1 with channel 2 or 3 via monitoring the battery bank voltage? The relay would close, the generator would start and then at the end of the charge cycle the relay would open, thus turning off the genset?

I have attached a drawing of what I am proposing. Will this work?

crewzer · September 2007

Re: Morningstar Relay Driver

Tnhunter,

I'd say you're on the right track, but some adjustments are required. One is that the power supply voltage must be at or above any measured voltage input. So, if you're looking to monitor "48 V", you'll need a corresponding power supply voltage. Also, a port must be "disabled" for it to be used as a voltage input.

I don't know how much you've studied Morningstar's Relay Driver documentation. Accordingly, I strongly recommend you download and study both the manual and the application guide. You can also download (free), install, and play with the programming software before you buy the unit.

HTH,
Jim / crewzer

tnhunter · September 2007

Re: Morningstar Relay Driver

Crewzer:

My genset has a two wire start that I am currently using a simple switch to control. Join the two wires together it starts, disconnect it stops.

Using a 48vdc relay can I using channel one on the driver to "close" the switch when certain battery bank voltages are reached, then use the other 3 channels to control the same relay when other battery bank voltages are met? Would this damage the driver or do I need to have multiple relays?

Does Wind and Sun sell 48VDC relays that would accomplish this?

crewzer · September 2007

Re: Morningstar Relay Driver

Tnhunter,

My take on the RD is that the stand-alone GenStart function will only respond to one control variable. So, if you connect your relay to Channel 1, you could set up the RD to respond according to voltage levels on Channel 2.

But, I see no reason why you couldn’t connect another relay to Channel 3 and have it controlled by voltage level input on Channel 4.

48 V relays might be a problem to find. If you have a 12 V power supply you want to use, you might consider running the “48 V” from the battery through a resistive voltage divider and then into the RD. Just remember that a “48 V” battery can operate at 60 V or so, so you’d have to factor that issue into your divider design.

For example, you could build a network that looks something like this:

+60 V / +48 V
R= 62 K / 5%
Tap
R= 15K / 5%
Common

With 60 V at the top of the divider, the tap voltage would be ~11.69 V. This should be OK if below the 12 V supply’s actual voltage. If you want the generator to turn on at 48 V and off at 50 V, the “Turn On Threshold” setting would be 48 V x (15 K / (15 K + 62 K)) = 9.35 V, and the “Turn Off Threshold” setting would be 9.74 V.

Actual resistor values may require you to tinker with the exact voltage and delay settings. The current drain through the divider would be ~50 V / 77 K Ohms = ~0.6 mA. This shouldn’t be a problem for the batteries.

NAWS sells 12 V relays and sockets for two-wire generator control. See: http://store.solar-electric.com/regest12vosi.html Don’t forget an anti-kickback diode for the relay coil!

Note that an automatic generator start function is a potentially dangerous operation, as things, animals, or people could be near, on, or in the generator. Please proceed with caution.

HTH,
Jim / crewzer

tnhunter · September 2007

Re: Morningstar Relay Driver

Please comment.

Using the Morningstar Relay driver and after reading it through multiple times.

I would like the supply voltage for the relay driver to come from the battery bank of 48 volts nominal at pwr connection.

Have channel 1 monitor the battery voltage via jumpering from pwr connection to channel one terminal, (disabled per instruction manual).

Have channels 2, 3 and 4 monitor channel 1 voltage and activate at different levels of battery charge state.

Wire channels 2, 3 and 4 into SEPARATE 12 volt relays supplied by a separate 12 volt power supply.

Have each relay above go to the two wire start genset. (Close to start, open to stop).

Would this work??? Morningstars documentation says that the relay coil voltage must match the Relay Driver supply voltage.

I have been looking at 48 volt relays and all have stated that the maximum voltage is 110%, which would make it 53.28 volts max. With this voltage as max I never could bring the battery bank up to a full charge much less equalize it using the generator.

Am I missing something or does this sound workable?

crewzer · September 2007

Re: Morningstar Relay Driver

I agree with you that a voltage measured at Channel 1 could be used as the common control variable for relays connected to Channels 2, 3, and 4.

I see in the instruction manual (pg. 47) where it says: “CAUTION: The relay coil voltage must match the Relay Driver supply voltage.” I suspect that applies to the schematic shown on that page, where the RD and the relay share the same power supply.

Page 49 includes the following statement: “CAUTION: If using a power source other than Relay Driver power, the source voltage must be less than or equal to the Relay Driver power voltage.”

Accordingly, I believe that you could power the relay drive from a “48 V” source, use the same source as your Channel 1 control variable, and then use Channels 2, 3, and 4 to “sink” 12 V relays connected to a separate 12 V power supply, just as you've described. The 12 V supply and the 48 V supply would have to share the same common.

HTH,
Jim / crewzer

Morningstar Relay Driver

Comments

Categories