Why did my motorcycle rectifier/regulator fail when testing with a Variac?
Asked by HardcoreTraveler89
I'm in the process of converting my 6V Suzuki moped to 12V with LED lights, and I bought a reasonably priced rectifier/regulator from Amazon. Unfortunately, it arrived damaged with some broken cooling fins because it was shipped unprotected with my new SLA battery. To test if it still works, I connected the output to the battery and the input to my Variac set at 18VAC. However, the Variac blew its 8A fuse and the insulation on my alligator clips melted. Since the rectifier is rated for 20-60VAC, I thought the input should be fine. Could this failure be because the rectifier/regulator expects a high impedance AC source, while the Variac offers low impedance? Should I risk trying it on my bike, or might I damage the stator wiring?
Answers
Given the shipping damage and the failed electrical test, I would be cautious about installing it on your bike just yet. Visually and electrically, it seems like a gamble. Although your test didn't hold weight completely, I'd suggest at least doing a thorough check for any lingering damage before you connect it to your bike's system. If you still feel uncertain about its functionality, returning it might be a smart move.
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The problem seems to stem from how you're inputting power. When you rectify 18VAC, it peaks at about 25V DC, which could push too much current into your 12V battery without a current limit. This is likely what blew the fuse. Even if the rectifier/regulator should manage the output voltage around 14.3V for charging, the initial surge from the Variac was probably too much. You might want to reconsider testing it outside the bike again. It could be worth bringing it directly onto your bike where the wiring setup can handle it better.
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