what size Victron SmartSolar charge controller 15amp (1 Viewer)

[colyboy]

Last couple of days have been looking around the Peterborough show. Talking to retailers who sell solar panels and equipment !

I have had mixed replies to my questions!

have already 110 solar panel and two lithium batteries Connected a VictronSolar Charger, which is 15 amp. i am told that if I fit another panel of about the same size I will have to obtain another Victron Solar Charger of 20amps of 30 amps . What would you suggest?

 

[Tombola]

Yes, the 75/15 will take 220 w,
its unlikely you will ever get full wattage so suck it and see, then jump up the the 30 if you feel the need that will take 440w and gve you some future proofing.
If you dont need it future proofing then the 20 will do for the saving 290w

 

[RogerIvy]

As Tombola says it’s highly unlikely that your 220w panels will push more than 15A into your battery. Theoretically possible but highly unlikely.

Actually, it’s the voltage you need to be careful of. The controller will simply drop excessive “amps” or “watts” down to it‘s max that it’s capable of.

I don’t recall seeing whether you‘re connecting the new panel in series or parallel. Parallel would mean you keep the voltage down.

I believe the controller you’re using is a 75/15 (I think you only mentioned the 15A), which means you’re meant to not exceed 75v but the 15A is not as important (you just waste power).

The question is: what happens if you exceed it only by a bit? Probably nothing. And this would probably only happen if you were in ideal conditions in with the sun bright and directly overhead. Combine this with the fact that your panels would then probably be quite hot and therefore not pumping out the full voltage anyway (thereby bringing you under the threshold). But if you were in cold conditions with very strong sunlight (especially if you were parked at an angle facing the sun) your panels could generate a high voltage. Enough to damage the controller? Victron don’t specify their margin for error, I’ve not found a study that tells us what it is.

Sorry my answer is a bit waffly but thought I’d give you more info.
Most of us would suggest an upgraded or additional solar controller just to cover ourselves in case things went very wrong. Your decision is basically based on a theoretical but highly unlikely event vs total peace of mind. The next size up would be a 100/20 Victron controller costing roughly £130 - the cost of peace of mind?

This from the Victron site:

5. Troubleshooting Guide - MPPT

www.victronenergy.com

5.3.5. PV voltage too high​

The PV voltage should never exceed the maximum rated PV voltage of the solar charger. The maximum PV voltage rating is printed on the front or on the side of the housing of the controller, and in the product specification sheets.

The solar charger stops charging if the PV voltage exceeds the maximum rated PV voltage. At the same time, it will display an overvoltage error #33, and will fast blink its absorption and float LED.

Charging will not recommence until the PV voltage has dropped 5V below the rated maximum voltage.

When investigating a high voltage issue, also look at the history of the VictronConnect app, solar charger display or GX device. Check the highest PV voltage for each day (Vmax) and also look for past overvoltage warnings.

VictronConnect: screenshot of an Error #33 and a screenshot of the history indicating an error
Check the open circuit voltage (Voc) rating of the PV array. Ensure that it is less than the maximum rated voltage of the solar charger. Use the MPPT sizing calculator on the solar charger product page. In case the PV array is located in cold climates or if the night temperature drops close to or below 10°C the PV array can output more than its rated Voc. As a rule of thumb, keep an additional 10% safety margin.

An overvoltage event can damage the solar charger, depending on how much the maximum PV voltage was exceeded. This damage is not covered by warranty.