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Andrew Aikman avatar image

MPPT 75/15 - Consumption - why is consumption high when there is no load?

Hi all,


I am new to solar and need some help. I have a simple solar set up two 300w panels, victron MPPT 7/15, victron phoenix 24v 250 inverter and two 140ah AGM batteries in series. Attached to the MPPT load I have a USB charger to power a mobile phone. I also have a blue tooth dongle attached to the inverter to link to the phone / app.

I have a breaker in between the panels and the MPPT and fuses between the MPPT and batteries and between batteries and inverter - all on the live wire.

When everything is off - no load on either the USB or inverter (inverter is switched off) the Victron app is showing consumption of 50Wh.

The system ahs been running for around 2 months. Initially consumption was no more than 40wh but in last week or so it has been over 100wh (but with load - laptop / two monitors c100w - 140w).

Questions I have are:

1. Is this normal / typical?

2. If not normal what could be causing it? Problem with MPPT / batteries / connections / panels / fuses?

Any help / advice greatly appreciated.

MPPT - Solar Charge Controllermppt smart solarmppt charging
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3 Answers
TrinasGarden avatar image
TrinasGarden answered ·

The other thing I see is that your system might be going in and out of bulk/absorb/float too soon? That would require some playing with settings in your mppt. Are you using a battery monitor at all?

If not, seriously consider it. You can get really cheap tiny things on-line that will give you at least some good info the mppt does not if the bmv isn't in the system plan.

I'd say it's a critical tool having a good battery monitor.

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TrinasGarden avatar image
TrinasGarden answered ·

Woah

How are you using two 300w panels with a 75/15? Even in a 24v setup that"s overloading it most of the time unless your panels are really old and put out at best 1/2 or even 1/3 the rated amps ever.

600w /34 stc probably and at least 8-9a ?

Convert that to 24v with losses and still WAY over that 75/15a output rating. You could blow the 2nd stage in your controller if those panels ever come close to spec on a cold day!

I'd get a 30a or 40a controller soon and swap out. Or just a second 75/15 for the other panel (if your panels don't do much amps out anymore) and completely split your array and set the MPPT's the same (you can link them to share a saved settings file I think?) as they won't fight each other at all as long as they have the same settings.

Just sayin'

Unless you made a typo or I misread something.


P S.

-0.10a draw then x20÷ hours @ 24v~27v system is how many watts? There's your phantom draw in the screenshot. Is that load running in difference from usual?

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If I had to guess, looking at the history they are 300w eBay panels that are really only 180-200w maximum.

To the OP, I wouldn’t worry about 50wh consumption.
so long as your batteries are reaching full charge each day and going into float you should be fine.


mrseas avatar image
mrseas answered ·

Turn off “load” in the CC settings. Problem solved.

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