cheap meter or measuring device for solar energy from panels.

What Softdown recommended (DC Current Clamp DMMs) are great for debugging and understanding how your system works, but not for permanent installation/monitoring. Here are a couple of examples of DC+AC current clamp DMMs:

https://www.amazon.com/gp/product/B0772FYF5M/ref=ox_sc_saved_title_1?smid=A3PUZ24ZTJP3C5&psc=1 (less expensive)
https://www.amazon.com/gp/product/B019CY4FB4 (mid priced)

-Bill

Regarding where to put the meter... Make sure that the meter is rated for the maximum voltage you expect from the array (i.e., Voc-array = 80 volts, then the meter should be rated >80 volts).

Note that digital meters use electricity to make their readings/store values/etc.... Some may draw directly from the input power, others may have separate (or separately) DC point to the electronics (i.e., meter goes blank at night, forgets daily harvest, etc.--Or with separate power input from (example 24 volt battery bank), shows zero power/volts/current and saves current WH/AH harvest numbers). The meters probably draw almost zero Watts/Amps from DC power source (when compared to the 100s+ Watts from solar array).

You can have issues... Many digital devices have common DC ground references (i.e., the negative wire from the solar array is "bonded" to the Negative DC remote power input--As an example). You can get into issues of "stray current flow" between the array negative and the battery bus negative... Just do your research. Isolated DC power input (vs measured load connections) are usually better (safer), but tend to be more expensive (to manufacture an onboard isolated power supply).

Sorry to be so wordy--This can be a big issue, and I have never "played" with these devices before to know their ins and outs.

REgarding is a 10 amp PWM controller not as good as a 30 Amp controller... To a degree, it is just cheaper (less copper, smaller transistors, etc.) to build a 10 amp controller vs a 30 amp controller. If you never plan on needing more than 10 amps, then a 30 amp controller (if more expensive) is not a great help. Note that electronics do age/fail with temperature... A 30 amp controller should be cooler than a 10 amp controller, when both carrying a 10 amp load. For this side of the argument, a larger controller running cooler should last longer (assuming both good quality controllers). Good ventilation (good cooling) is always important with power/electronics.

Downside with larger controllers--May draw more energy to run the larger parts (PWM controllers typically do not draw that much power anyway--MPPT controllers use more power). So, a "too large" controller can waste energy on a smaller system.

For 60 Watt panels, assume Vmp~18 volts:

• 60 Watts / 18 volts Vmp = 3.33 Amps Imp per panel
• 10 amp controller * 0.80 NEC solar derating = 8.0 Amps nominal max current
• 8.0 amps derated controller / 3.33 amps = 2.4 panels ~ 2 panels (120 Watt array) maximum

As always, read the charge controller manual. The 0.80x NEC derating, if the controller is rated for 10 amps, then you should be able to use 10 amps (in my humble opinion)--The NEC derating would seem to be a bit bogus (here). There are times when you can get more solar energy (clouds can "focus" extra sunlight/energy on array)... So, the derating is not totally bogus.

And, I like to use the NEC 1.25 / 0.80 deratings for wiring/switching/circuit breakers/fuses/etc... For example, NEC type fuses/breakers are typically rated to blow at 1.0x or higher than rated current, and not blow at 0.80x rated current. So for a 15 amp branch circuit (wiring/breaker):

• 15 amps * 0.80 derate = 12 amps maximum continuous rated current (suggested by me, NEC also uses for continuous current--Like Gym Lighting that runs 8+ hours per day)

If you want to run 15 amps, then:

• 15 amps * 1.25 NEC derating = 18.75 Amps ~ 20 amp rated wiring/breaker/fuse

-Bill