1

I have five Inerstate DCM0100 wired up to give 12 V, 500 Ah. I have a Renogy 40A MPPT Rover Charge Controller. I have a Jarxioke 4000 watt inverter I purchased today.

  • Precursor this knowing that I most likely did damage to my batteries some time ago as I am still learning.

I powered my RVs 120 V system from my battery bank via the inverter purchased today. I turned on the microwave and the inverter is telling me it uses about 2100 watts and ran just fine. Looking at my charge controller, I see that my batteries IMMEDIATELY dropped to about 63% as the microwave was going and it was slowly going down from there. As soon as I turned the microwave off, my batteries, which are currently getting full sun at the panels, returned to 100% within 10 seconds.

I think there’s potentially several issues and would love input on this.

  1. I think my batteries may be damaged.
  2. I think I may be trying to pull to much power.

I am not sure but am hoping some of y’all can shed some light on the situation and/or offer some advice/troubleshooting.

Thank you all in advance.

11
  • 3
    what drops to 63% of what,
    – Jasen
    Oct 12, 2022 at 21:52
  • 2
    I don't see that an electrical engineering answer is really possible, it's as much of a usage question as if you'd ask why your light bulbs dim when you turn on the stove.
    – pipe
    Oct 12, 2022 at 21:55
  • 1
    it could be that the charge level is not being measured correctly.
    – Jasen
    Oct 12, 2022 at 22:10
  • 4
    The battery is undersized for pulling up to 400 amps from it. Even ~200 amps is causing it to lose power due to internal resistance. Get another 500 A-h battery and put it in parallel; this would last much more than twice as long. Oct 12, 2022 at 23:33
  • 4
    If your "% charge" meter only looks at the battery voltage, then at best it can only give you a meaningful readout at one value of current. If it goes down to 60-some percent when you switch the load on, and back up to 100% when you switch the load off, then that's probably what you're dealing with: a calibrated voltage meter. A real state of charge meter monitors voltage, integrates current, and maybe also monitors battery temperature. Maybe even models how charge/discharge cycles "age" the battery. IDK for sure. Batteries and battery management are somewhat of a black art IMO. Oct 13, 2022 at 2:10

1 Answer 1

1

I have five Inerstate DCM0100 wired up to give 12 V, 500 Ah. I have a Renogy 40A MPPT Rover Charge Controller. I have a Jarxioke 4000 watt inverter I purchased today.

So I guess that is 5 pieces of DCM0100 in parallel. you have about 6000 Wh of battery and a 4000 W inverter. If you actually use 4000 Watts you will run out of battery very quickly. As one commenter said, even 2000 Watts is a lot for that battery. But it should be able to do it for a short while. enter image description here Note that the 5 minute constant power output of the battery is 460 Watts. Since you have 5 of them, that is 2300 Watts. So you can do that for 5 minutes at which point the battery voltage will be 1.6 x 6 = 9.6 V. Your inverter may shut down before the voltage gets that low.

Precursor this knowing that I most likely did damage to my batteries some time ago as I am still learning.

I powered my RVs 120 V system from my battery bank via the inverter purchased today. I turned on the microwave and the inverter is telling me it uses about 2100 watts and ran just fine. Looking at my charge controller, I see that my batteries IMMEDIATELY dropped to about 63% as the microwave was going and it was slowly going down from there. As soon as I turned the microwave off, my batteries, which are currently getting full sun at the panels, returned to 100% within 10 seconds.

I glanced at the manual for the charge controller. It appears that it has a "load" output rated for 20 Amps. Obviously you are not using that. So it seems to me that the charge controller has no way of knowing how much current is going into the load. So the only way it can estimate state of charge is by looking at the battery voltage.

I think there’s potentially several issues and would love input on this.

  • I think my batteries may be damaged.
  • I think I may be trying to pull to much power.

I am not sure but am hoping some of y’all can shed some light on the situation and/or offer some advice/troubleshooting.

Your charge meter is ESTIMATING the remaining charge in the battery based only on the voltage. When you use 2000 Watts of AC from the inverter you are going to be using 200 Amps from the 12 V battery (more or less). The battery voltage will temporarily sag. Since your charge meter is the "dumb" type which only looks at voltage, it thinks that the battery charge has dropped.

When you turn off the load, the voltage recovers (and having 40 Amps of charge current helps with that too). So the charge returns to 100 percent.

In summary, you shouldn't expect your charge meter to be very accurate in this situation. The best time to look at it would be early morning before the sun comes out. Assuming there is no load on the battery and the charge controller is not charging, the reading may be approximately accurate.

3
  • Battery bank, even if not damaged, is far too small to run that inverter for any reasonable load/time. If damaged, its actual capacity is less. And this load will be damaging it further, so new battery bank time is coming soon.
    – Ecnerwal
    Oct 16, 2022 at 17:50
  • @Ecnerwal, the fact that the inverter ran the microwave at all is proof that the batteries are not too far gone yet.
    – mkeith
    Oct 16, 2022 at 18:52
  • @Ecnerwal, I do agree with you that the battery bank is too small to supply a 4 kW inverter. That is why I posted the datasheet. The maximum constant power discharge time shown is 460 W for 5 minutes. However, it is not at all clear to me that the batteries will be damaged by supplying 2 kW for 1 or 2 minutes. That is a rapid discharge, but not a deep discharge. Reviewing all the comments I see nothing but endless negativity and no helpful information or explanation about what is going on except from Solomon Slow and Jasen.
    – mkeith
    Oct 16, 2022 at 19:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.