I have a 24v/3000w Multiplus. It is about a year old. We are finding, using a clamp meter to confirm, that there is a 17-20 watt draw from it when the physical switch is turned to the off position. Is this normal? It does not seem right....
asked
Should there be a power draw from the Multiplus when the switch is in the off position?
Yeah. I'm the same guy from over at DIY Solar, and you answered my question here. :P
This doesn't seem correct. I have 2X 48V/5000 Quattros operating in 120/240V split phase. When I turn them off, BOTH my Batrium and BMV-702 report about 21W. That 21W is powering 1) A wireless access point, 2) a MiniPC running Win10 and the Batrium toolkit, and the Batrium itself as well as a small 5V fan continuously cooling the WM5 heatsink.
My Quattros, which normally pull about 30W EA when on, would be pulling more than your stated 17-20W.
If you're using a meter that measures very high current relative to the < 1A you're measuring, in addition to making sure it's zeroed out before and after readings, you need to check its accuracy. Even reasonably accurate meters can get a lot of error stacking when trying to measure very small values compared to their max. My neighbor and I chased an issue as to why his HVAC unit was continuously drawing about 70W 24/7 while completely off at the thermostat. He was showing a 0.3A draw on his 240VAC line. The margin of error on the meter at that current level was 3X larger than the value measured. No other part of the system suggested that load was real. Once we checked it on the 24VDC supply side, there was no measurable difference in DC current when the breaker to the unit was switched on and off.
I have a CL800 that can measure 60A or 600A of AC or DC current. Stated accuracy is ±(2.0%+5).
When in 60A mode, that means any reading can be ±1.2A. The "5" means the least significant digit can also vary by 5. The meter reports 0.00A accuracy on that setting That means there's an additional 0.05 error pushing the absolute error range to ±1.25A on any reading, which is larger than the approximately 0.8A you're reading on your meter.
What does your Batrium shunt report?
MisterSandals knows his stuff, so I don't want to second guess him. My eye-opening experience with ammeter low current (in)accuracy compels me to investigate.
Please confirm:
- Inverter power switch in the OFF position - no AC inverting or charging possible.
- Batrium reports 17-20W load.
- You don't have DC loads that can account for #2.
What confuses me is your comment about the fridge/freezer. If this is AC, the inverter power switch must be in the ON position to draw AC power, and thus a 17-20W draw in the ON position, but with no loads, would be normal.
Pulling the inverter (+) cable would definitely isolate the inverter from the situation.
Hey hey Snoobler.... thanks for the feedback here. You were a huge help at the beginning of my design/build of this system over on Will's forum.
While I understand some of what you're saying above regarding the meter and it's accuracy in measuring a small draw, much of it is lost on me. I went down to Mister Sandal's place here in the Bay Area, and he used a clamp meter he had to get the readings of the draw from the MP. And, the shunt is confirming that that draw is constant. And, the battery depletion by morning more or less corresponds to support the draw though that's somewhat nebulous. There's a fridge/freezer running on the system, and it's draw depends on night temps.
I'm thinking I might just pull the positive cable from the batteries to the MP, and see how that changes things. That would be the most absolute way I can think of to confirm this one way or another.
I did the test today but, in my usual scatterbrained manner, it all got a bit muddled and as I try to recount it here, I realize my memory isn't making sense. I'll do it again tomorrow and record but, it appears possible that the fridge/freezer is the culprit (that still doesn't explain Mr Sandal's clamp meter readings at the MP but, I'll come back to that after test. I don't own a clamp meter (yet.) The fridge is 24Vdc and, my muddled test today showed the possibility that it is drawing even when the compressor is not actually running. I'll step by step test tomorrow, and report back here. But, answers to 1-2 above are both yes, with certainty.
Any test results?
