thatphilbrettguy avatar image
thatphilbrettguy asked

Solar charging affected by high inverter loads


I've got a SmartSolar 150/35 with a string of panels totalling 600W. I've a couple of 110AH TN Power LiFePO4 batteries in series so running at 24V.

I've also a Phoenix Inverter Smart 24/3000. Both the charger and inverter are connected in parallel to the batteries via fuses etc. Cables to the inverter are 50mm2 copper and 16mm2 to the charger.

Generally on its usual load (around 150W) everything is fine. The 'fun' starts when I charge the car....

I've set that rate to 1.3KW which the inverter is fine with and it charges nicely. One of the batteries gets a bit warmer than the other but nothing to worry about. But the yield from solar drops right down from say 400W to under 200W. I note that the panel voltage also drops from around 95V to 50V as well. It's almost like the MPPT tracking has gone wrong somehow. Stop charging in the and it all recovers.

Ripple up the DC to the charger upsetting it? Something else obvious I've missed?



solarinverter current draw
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1 Answer
texan avatar image
texan answered ·

Hi Phil,

unfortunately I do not have a solution for your problem but I can confirm that I do see the same effect with my setup.

I do have 2 Solarpanels (190Wp each) hooked up to a Victron Smart 100/30 and a Li Battery. Everytime when I switch on the AC unit the solar yield drops by about 30-40%, starts to fluctuate heavily but does not return to its previous yield. As you already said it seems that the MPP tracking gets out of line.

Hopefully, one of the experts does have an answer for us.


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thatphilbrettguy avatar image thatphilbrettguy commented ·

I’m running mine at 230v (I’m in the UK) and one thing that is a concern is with a multimeter on AC there’s 58v of AC wave on the DC input. Not ideal.

I haven’t got an oscilloscope at this property to see what it looks like or what frequency it is but it must be more than ripple.

I've probably not got the system properly bonded or earthed so that’s today’s task!

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thatphilbrettguy avatar image thatphilbrettguy thatphilbrettguy commented ·

Well I've earthed everything to one point, cases, battery negative the lot and.... better sadly. What does worry me is the apparent level of AC on the DC terminals. Over 50V of something.

I can't believe it's just us that has this or are we unlucky and both have faulty inverters? It's definated the inverter pushing the AC on to the DC.

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thatphilbrettguy avatar image thatphilbrettguy commented ·

Well some more info. One of my Li batteries let go, so my local solar supplier lent me a couple of lead acids whilst we waited for a replacement. The effect was MUCH less with these. Now the Li batteries are back in place the issue is back to the same as it was. All very strange.

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