question

Make sure the MPPT is up to date on firmware, its settings are correct and the BMS is actually allowing the charge. In order for the MPPT to start, the PV voltage needs to be battery voltage +5V. After that it needs to be +1V to continue charging. What was VictronConnect saying about the charger status? And of course, you actually need a battery connected to the MPPT in order to let current flow.

My guess is, either your battery is fully charged, or two panels are not enough in order to start a charge cycle. 110W at 18V feels like older polycrystalline. Should still work, but dont expect wonders from them.

Chrigu, thank you for the reply. It's dark now so I can't get some answers till there's sun tomorrow. What I can answer is:

The firmware is updated. Each controller has not been used till today and each updated twice with no issues.

I selected Smart Lithium LiFePO4 in the battery preset menu, 12V. When I clicked on expert mode it suggested the default works for most installations. This battery is new, uncharged except for being connected today. It has BMS, as does a 2nd LiFePO4 battery that has a 25 AH rating. The smaller battery has been running a fan for several hours & has not been charged in the last week. It needs charging.

I connected to both batteries with the same issue of higher volts reducing to that on one panel.

The panels are fairly new, using Maxeon cells. These are the SPR-E-Flex-110 panels. The specs are on this page. https://sunpower.maxeon.com/int/sites/default/files/2019-10/sp_E_Flex_110W_UK.pdf

The charger status said it was in the Bulk state.

----

Specs for the 100AH battery are:

Nom V: 12.8

nom Capacity: 100AH

Energy: 1280WH

Charge V: 14.6

Charge current standard charge: 20A - Rapid charge:100A

Discharge cut-off V: 10V

Overcharge protection V 14.8V (Adjust charging V to below 14.8 to resume charging)

Over discharge protection V 9.40 +/- 0.32V

Charge method CC/CV

Internal resistance <30m ohms

The reason I decided to try the two panels in series was to always have the PV be > 5V higher than the battery. I can't imagine why the high voltage drops back to single panel stats in roughly 10 seconds after being connected to the controller.

Why the higher voltage of the two series panels registers properly initially, and then drops to the voltage on one panel in approximately 10 seconds is beyond me.

Ah, these are flexible 32cell panels. I hope youve seen the max system voltage of 45V in the datasheet. Seems a low figure to me, but that might be due to being flexible panels. So two in series max in practical terms. I cant advise to connect more in series to get a higher voltage.

Let the system work for a bit, theres a 10min intervall at which the MPPT drops the panel voltage down to search for a better MPP, maybe it didnt notice that its got an additional panel and used the previous voltage level?

Chrigu, thanks for the thoughts. FWIW, today the controller was showing the correct V for the two panels in series. Initially it showed the correct V & then like yesterday dropped down to 18V. A few minutes later it started showing higher V till it reflected accurate voltage. Once doing so it remained apparently correct throughout the day. Perhaps there was some internal recalibration and after the 10 min interval you mentioned,now it's happy?

I've had both panels since new. I played with it with a nice controller that has no Bluetooth and only worked with lead acid. One panel suited my needs and the other was unboxed. Going with the Li battery I saw I could do more with it and as the controller works with the > 5V requirement, I unboxed the spare which I was going to sell and put it in series to give a constant higher V output, not to mention greater charging power. I have an Aliner and one will go nicely on each side to catch the sun in both directions.

These really are perfect panels for camping & take so little space for their respective output. I would consider 3 of them, I don't think the V would damage them. However, they're hard to find today and more expensive than I'm willing to pay for $/Watt. So 220W max is what I'll have with these.

Thank you for your help, I appreciate it.