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I have a small compressor that I'd like to run off a deep-cycle battery which will be connected to a couple of solar panels through a charge controller. There will be an additional microcontroller of some kind to control the cycling of the compressor, monitor voltage, turn the compressor off at night and offer some hysteresis.

I'm reading that for any reasonable DC load that it's no probem to connect the charge controller and load across the same battery and things will be ok, but I'm not finding much on running a motor as a load. I know motors are an inductive load, and could potentially damage components not rated for the high-current on motor startup and motors sometimes have capacitors in their starters to fix the phase problem, but I can't figure out how to either buy or build the components I need to make sure I won't kill the charge controller or other components.

Here's some specs:

  • Compressor, 12V motor, 23A max, 228 Watts
  • Deep Cycle 12V battery
  • 60A 4-stage PWM Charge Controller, compatible with 12 or 24V systems
  • 2 solar panels, each 275W, 38V open, 32V rated, 8.7A

The plan is to run the compressor on a cycle to maximize run-time with the available power coming from the panels. Will the motor loading kill the charge controller? Is there a capacitice starter circuit I can use to make this work, or is there a better charging management system I should be looking for? Should I be looking at MPTT or some other difference in charge controller type to make this work?

Feel free to tell me if I'm way off on any part of the system.

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  • \$\begingroup\$ if you have full control over the compressor, then disable the charge controller whenever you issue the start command to the comoressor controller \$\endgroup\$
    – jsotola
    Jun 11 at 23:12
  • \$\begingroup\$ Temporarily, or for the duration of running the compressor? I'd really like to be able to use the capacity of the panels to their max if I can. \$\endgroup\$ Jun 12 at 0:20
  • \$\begingroup\$ not for duration of run ... only when the compressor is starting, because that is when it is probably drawing the most current \$\endgroup\$
    – jsotola
    Jun 12 at 0:22
  • \$\begingroup\$ See what the data on the charge controller tells you about this. If it is not there contact the manufacturer. I do not see a reason this could not work but it is dependent on the charge controller which we have no idea of what you are using. \$\endgroup\$
    – Gil
    Jun 12 at 3:18
  • \$\begingroup\$ I'm using this one, but happy to consider something better. amazon.com/gp/product/B085VQN5RK It works for charging, but I'll need to dig deeper into if I can get better data out of it. I can isolate with some diodes, but haven't checked whether it can provide data to a micro or not. \$\endgroup\$ Jun 12 at 3:23
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The compressor is no different than the AirCond compressor in an automobile running off the alternator but with low impedance offered by the ESR of the battery. The difference is you need a larger battery as you intend to run it when there may be go PV current generator.

There may be some sag from the ratio of of the compressor winding resistance, Rs and the battery ESR so (ESR/ESR+Rs)* 100% is the % drop in Vbat and also flyback voltage when turned off so as in automotive when the battery is weak with high ESR, accessories must be able to handle surge voltages for some duration in mJ energies handled by sufficiently large MOV’s or better , TVS.

But you must determine what tolerance and protection is needed for electronics on the battery. But I suspect the charge controller must have a spec.if you ask the supplier.

There are no start caps for DC motors as their is no AC phase in the source.

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