question

brow01 avatar image
brow01 asked

Blue flashing light - different readings between bluetooth and multimeter

I have recently installed a SmartSolar 100/30 MPPT charger in my caravan. I have 240w of solar (2 panels in parallel) and 2 x 120amphr AGM batteries (which are only 4 months, have not been below 11.9v when they did their one and only trip for 2 days, otherwise they are kept on mains power charge).

My SmartSolar charger flashes the blue light every 4 seconds. The Victron Connect app tells me there is 12.63v coming into the charger, but when I check the wires coming from my panels, my multimeter tells me there is 21.4v running through the wires.

When I select the "Why is the charger off?" in the app, it tells me the panel voltage "must be 5v above the battery voltage". My multimeter tells me my batteries are at 12.79v. If my multimeter is correct (don't know why it wouldn't be) there is an 8.61v difference.

I have disconnected and reconnected everything. Even had an auto-electrician come and look at it and neither of us can identify the issue.

2 questions - Why is there a difference between the charger and my multimeter? and How do I fix this please?

Any help is greatly appreciated.

MPPT Controllers
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
JohnC avatar image
JohnC answered ·

Hi @Brow01

When you tested with the multimeter the panels would have been disconnected, so you get an open-circuit V, no Amps.

When connected to the mppt, it's then 'processed', trying to find the best Vmp to produce current at. In poor light that can drop quite low, but you don't say what conditions are.

You could try your panels wired in series.

4 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

brow01 avatar image brow01 commented ·
Cheers John. My conditions were perfect for solar (I would have thought). Cloud free skies and a balmy 30deg C. Panels have been cleaned.

It's weird because I left the batteries under (some) load overnight and the voltage dropped from 12.8 down to 12.4. We have another day like yesterday (cloud free - full sun) and have had roughly 3hrs of full sunlight so far (it's 10:30am AEST). The batteries are still under load (fridge still on, drawing about 3amps) and are showing 12.66v (at the terminal, on the multimeter) and 12.56v through the Victron app. Does that mean there must be some charge going into the batteries from the controller?

0 Likes 0 ·
astrayan avatar image astrayan brow01 commented ·
There should be current from solar and current to batteries, listed in the app. Some of the voltages you mention indicate small charging going on, but not a lot.
0 Likes 0 ·
astrayan avatar image astrayan brow01 commented ·

Those types of panels are notorious for being fake rated, because nearly everything is grid 60 cell panels these days, so Dr dodgy sells 12V ones on ebay etc. Victron makes some quality ones. Just say they were real rated, at 120W, you would expect the MPPT to find a power point around 16V (midday), and a current of about 6 amps each = 12A. When you pull the solar input wires out of the charger and flick them together, you would expect to hear a healthy click or fizz. If you use your ammeter on ONE panel, you should get 6-7 amps. If you use it on both, it will blow up.

0 Likes 0 ·
JohnC avatar image JohnC ♦ brow01 commented ·
@Brow01

12.6V on AGMs certainly suggests they're getting some charge. Maybe while your back was turned. :)

You could try setting up Trends in VictronConnect to watch it over the day. Good data is key to troubleshooting, and indeed optimising your system.

It's likely you could do better with your panels strung in series. Gone are the days of '12V' panels (like your 21Voc units) and PWM controllers. Your 100/ panel V mppt is designed for longer strings, and the only reason for paralleling them is to deal with selective shade. In practice, on a van, this won't happen often. And do you really want to be parking your van in the sun on a hot day when there's a shady tree handy? With a series string, shade will surely affect output, but won't cut it to zero.


0 Likes 0 ·