I’ve added the “professional” tag as a bit of sarcasm.
DIYers, here’s a tale of woe that might save your system, or your house, or your life.
This pair of photos of an MC4 connector shows a crimping job done by an electrician who didn’t have the correct MC4 tool. In this case, the fallout was very very minor - the customer paid for 6 panels that never contributed anything for 2 years.
Not long after the system was installed the customer noticed that out of 3 controllers, each with identical 6s2p arrays, 2 would be consistently pulling double the power of the 3rd system, however nothing was done about it as the panels were difficult to get to.
When the system had additional batteries added recently, the panels were pulled up to find the fault. The fault was an extremely poor crimp that would pass full current for about 10 to 30 seconds when first turned on, but then drop back to almost zero current. The MC4 connector showed signs of being hot, and had become brittle.
This connector could have easily caused a fire, and given that there were 36 panels in a block, all 36 would have been burnt, and the fire could have possibly caught the timber frames under the roofing iron alight, which would have torched the whole shed.
A proper MC4 tool, even in New Zealand (where almost everything is imported) costs around $500 for the super fancy tools that a professional would use and calibrate annually, down to about $30-$50 for a tool that is not expected to last a lifetime, and can’t be re calibrated, but should crimp to the required pressure reliably.
There are only 3 tools you really need; a good screwdriver for ensuring terminals are tight, a lugging tool for cables such as battery and inverter supply cables (say, 16mm up to 70mm, depending on your system), and an MC4 tool.
- The screwdriver is mandatory - you can’t use a kitchen knife, even if you are “The No. 8 wire champ”.
- The lugging tool is optional - if you are on a super tight budget, building a small system, you probably need 8 lugs done (inverter x2, breaker x 4, battery x 2) and most friendly installers will crimp your cables/lugs for you if you bring them donuts or beer. A passable manual/hydraulic lugging tool is about $50, but an electric/hydraulic will result in a much more reliable lug, and the cables are usually removable, so taking them somewhere to be lugged is generally easy. It might also get you a 5 minute chat with an expert, so you might get an opportunity to run your project past them for some advice.
- The MC4 tool is practically mandatory - many MC4 make-ups will have to be done in place (because of conduit, or they are on the panel’s leads, etc), so for the sake of everyone, get yourself an MC4 tool, and learn how to crimp MC4 connectors. Its a skill for life, and MC4 isn’t going away this century.
DONT learn from youtube idiots - but it’s very hard to know which ones are idiots, so i’ll help you here. If a youtuber disassembles the MC4 (other than to demonstrate the rubber glands), they are an idiot.
Many of the “experts” on youtube, even the ones with very very successful channels, do idiotic things like strip off way too much insulation, or disassemble the connector, or slap it together without the crucial steps of inspecting the strip and crimp before assembly.
On a crimp that is expected to last more than 30 years, there is no benefit to following a youtuber’s homemade methodology, or making up your own methodology.
It won’t be faster, it won’t be easier, and it won’t be safer.
Here’s a method to follow that will enable you to make a crimp that is known and proven to be fast, easy, safe, and meets international specs; (from Stäubli, the original MC4 manufacturer). You don’t need the fancy cable stripper - a stanley knife works fine provided you still inspect to check you haven’t cut any conductors.
RP>
