Can I mix panels of different voltages?

[jedics]

Does the sbms120 care if I add more panels to my existing 40v panels that might be up to the maximum 47v of the sbms?

I have 6 filling the roof of my truck which isnt enough in winter so I want to add two more of the largest I can carry myself that are deployable.

cheers

[Dacian Todea (electrodacus)]

I'm assuming now have 60 cell panels now and want to add 72 cell panels and that should work with no problems but the extra 12 cells will not help you with battery charging so you are wasting space compared to 60 cell panels for no gain.

[jedics]

When you say wont help charge my battery, if I have 2x 575w 72cell panels then 1150w is the theoretical max it will put in at any moment which is the almost the same as if I bought four 60cell 300w panels?

[jedics]

Another advantage is the deployed panels can be angled correctly for winter sun instead of flat on the roof which is roughly 10% more energy by itself.

[Dacian Todea (electrodacus)]

4x 300W panels could put in ideal conditions 1200W in to battery.

The 2x 575W  72 cell panels could put in ideal conditions 920W in to battery. So they will work but not be working at the max power point.

So if you get two 460W 60 cell panels they will do the same work as 575W 72 cell panels so the point is that the extra 12 cells in each panel will not contribute with anything just take extra space.

I'm fairly certain you have no problems in a sunny day no matter if it is summer or winter.

In a cloudy / overcast day the fact that panels are flat on the roof will not make much of a difference as light is diffuse trough the clouds.

Question is if you have problems 5 to 10 day per year in winter or you do not have enough energy almost all winter.

[jedics]

I thought that if the sbms could handle the voltage then it would also recieve the wattage.

Anyway your telling me Im not going to get more from a higher wattage panel then I will stick with 60 cell which all seem in the 300w range.

The worst 2 months of winter is certainly more than 10 days of not enough sun for my evening wants which regularly uses 30% of my battery.

I was thinking if I had two panels at the best winter angle and faced towards the morning sun, then rotated to face the evening it would be a meaningful amount more energy.

I have thought about putting my existing 6 panels on sliders so I could push them out horizontally with a motor exposing another panel underneath each of them. The only reason I haven't done this already is that another set of regular panels would make them sit higher on the roof making them quite visible from the road (reducing my current high level of stealth factor) so I was hoping for some thin flexible panels to come out that make even vague sense financially to be available but see none.

Any suggestions welcome

[jedics]

Another idea while on the subject was to put roughly 2000w of thin film panels on the left and right side of the truck so if I orientate the front of truck north I will get the max from my system without overloading the sbms eg. up to 2000w from each array but never the max from more than one array at a time...Eg. up to 2000w in morining from right wall array, then at midday up to 2000w from roof array with a little from left and right arrays and then up to 2000w from left wall array with a little from the roof in evening....Does this theory seem like it would work?

[Dacian Todea (electrodacus)]

It will make no sense to have the panels oriented East and West in winter when sun is very low in the sky and mostly south (assuming northern hemisphere).

Think film are super inefficient so you will need about 2x the area for same nominal power.

In winter panels mounted on one side of the wan will work best but that side should be facing south.

If you have cloudy (overcast) days then your 6 panels could produce as low as 600Wh so if your daily needs are higher than that you will start discharging the battery. 

Doubling the size of the PV array will slightly improve that to 1200Wh but if that is still significantly less than you are using in 24h it will  still not solve your problem.

You can find 60 cell panels that are larger than 300W is all about panel surface area. A 600W panel will be 2x as large as a 300W one and almost 2x as heavy.