Lensun MPPT has to be isolated from frame

Maybe. I posted last month about deciding which MPPT controller to install on my trike:

• MPPT controller for custom trike — September 13, 2024

...chose the Lensun. I very much doubt the Lensun company claim that it is both a buck and boost controller, as it says nothing in the documentation supplied with the controller, other than it is a boost controller. The Lensun website shows a photo with the front panel in English; however, the one that they sent me has Chinese characters on the front panel and Chinese User Manual. Here is the manual:

Page two:

I figured out basic usage. In the above table, you can see the value "58.4" -- that is for a nominal 48V LFP battery with 16 cells. That is what the charging voltage has to be set to. I already knew that, and figured out that the "+" and "-" buttons have to be held down together to put it into output-voltage-setting mode, then the "+" and "-" buttons can be used to set the voltage.

As can be seen in the earlier blog post, installed it on the trike, bolted underneath the solar-panel frame.

All seemed good, until a few days ago I was able to translate the manual to English. EasyOS has gImageReader, installable via PKGget (only recently added to the repository, see blog post). This is an OCR (Optical Character Recognition) app, which produces output as Chinese text. I then fed that to translate.google.com and got English.

It is all OK, except for this paragraph:

5. When installing this controller, it is best not to install the controller directly on the metal bracket.

...very interesting statement! My guess is that the power switching transistors are bolted to the controller heatsink frame with electrical-insulation. In ye olden days, this might have been a thin sheet of mica. It might be that they are not guaranteeing this isolation, hence covering themselves with the above statement.

Or, maybe they have only made that statement to reduce vibration.

Anyway, I decided to remount the controller isolated, on a small piece of plywood. Used plywood intended for internal use, so painted it for some external protection. Only two spray cans to choose from; black or red enamel. Choose red. Intended for metal, but reckon OK on the plywood. Put on three coats. Here it is mounted:

...quite easy to remove, convenient for testing the other controllers.

Ah yes, removal. First time bolted on, I used Loctite (medium strength) and locknuts. Only m4 bolts, but just about impossible to undo. Have used this combination all over the place on the trike, but as I discovered, the combination of Loctite and locknut is just too much. Got them undone, but was amazed that the bolts didn't sheer.

Those bolts are good quality. I bought plastic flip-top boxes of assorted lengths of bolts/nuts/washers and allen-key from Aliexpress, very handy. Bought m4, m5, m6, m8 boxes. They are 304 stainless steel -- that is not "marine grade".

The complete English translation is here: page 1, page 2

In the previous blog post, I mentioned a MPPT controller on Aliexpress that looks like the Lensun, but a fraction of the price. Yeah, I couldn't resist. Bought it ....and it looks identical to the Lensun. Don't know about internally. Do plan to test my collection of MPPT controllers on the trike sometime in the future.   

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