Energy Systems & Design, MN Classic, and LiFePO4 batteries

[skylineelectrical]

Hey all,

I've got a question for you all.

Small micro hydro with a Energy Systems& design unit that puts out around 500w continuous. My client wants to swap to lithium and integrate a midnite controller. 24v battery and inverter.

What equipment and settings would I need to have 600w diversion load between the batts and controller. I know i'd need to use the aux port, I believe AUX2 with one of the last two settings mentioned in the manual, either high or low volt actuation.

Any help greatly appreciated

[ClassicCrazy]

You would need a relay or contactor to switch on the load from the aux port.
The load could be resistance heater or water heater .
There are other options for the Classic aux ports such as diversion, waste not, SOC, etc.
I was using the Classic to switch PV input around the controller to my resistance loads.
I also used AUX 2 waste not to pwm AC inverter power  via SSR but that was on a lead acid system. Probably not useful with lithium where just on off would work okay.
If you have a Whizbang on Aux 2 then you are limited to Aux 1 on the Classic. Aux 1 doesn't do any pwm - just on off.
Larry

[skylineelectrical]

You would need a relay or contactor to switch on the load from the aux port.
The load could be resistance heater or water heater .
There are other options for the Classic aux ports such as diversion, waste not, SOC, etc.
I was using the Classic to switch PV input around the controller to my resistance loads.
I also used AUX 2 waste not to pwm AC inverter power  via SSR but that was on a lead acid system. Probably not useful with lithium where just on off would work okay.
If you have a Whizbang on Aux 2 then you are limited to Aux 1 on the Classic. Aux 1 doesn't do any pwm - just on off.
Larry

What is the PWM function of the Aux 2 exactly?

The dump load my client has is just a resistive heater. What kind of relay do I need to do this, can I use a simple auto relay rated for 30v. I would connect the control wires for the relay to the aux lugs, and then have the resistive load setup as the switched load on the relay? Is there anything I'm not seeing?

[Rob Linschoten]

Assuming a 24VDC dump load a 30V/25A relay will be adequate. Some people use diodes across the coil and the load terminals for transient control. Aux 2 can be programmed to put out a relatively low frequency pulse width modulated square wave for precise voltage control (0.1v increments). It is likely the Lihium batteries are not that delicate, so on/off will be less of a pain to program.

[ClassicCrazy]

You can look at DC rated solid state relays with the specs for your voltage and current. Also get a heatsink  and it doesn't hurt to put on the snubber that Rob mentioned.
Make sure you check that the jumper for the Classic Aux is set for 12v out instead of dry contact.
Or look for a DC rated contactor.
You need to find something that will run on the voltage and current output of the Classic Aux. Specs for that are in the manual.
Larry