Tuesday, June 22, 2010

She Cannae Take the Power Cap'n!


Automotive blade fuses... PAH!

Don't use 'em.

I had my new batteries connected to the main bank with an in-line blade fuse holder and a 30A fuse.  Not a cheap-o rubbish fuse holder but an RS one.  It was the day after the longest day today and the sun was beating down after I'd more than half drained the batteries watching movies last night.  Pulled 6.4kWh from the system :D.

Today though, the secondary bank was very greedy and spent quite some time sat at about 25-30A charging.  The poor little blade fuses couldn't hack it.  Two of them melted (the plastic holders - not the fuse wire!).

So I replaced the in-line fuse holder with an old 32 Amp MCB breaker that I got at a car boot sale a while ago.  It's better that way any way as it can disconnect the battery if there's a fault and it also serves as an isolation switch.
The rest of the afternoon's sun was soaked up without further melting or burning of plastic / rubber / fingers...


  1. Check not all MCB's will operate at DC.
    Ones that are rated at DC (often 12V to 125V DC)
    also do not trip at rated current but at factor of 1.5 ( ABB parts ) So the 32A part will not trip untill 48A.

  2. Yeah, they vary a bit but this one was fine and when the battery was a bit too greedy for charge it used to trip after a couple of minutes at a sustained 38 Amps or sooner if over 40A. The cable was rated to about 50A, so no problem there.

    Now I'm using a 100A double pole breaker with the poles in parallel for the lithium battery bank as a 200A disconnect switch. The charger and loads are actually fused with AG / ANL DC fuses.

    I just thought it was ironic that it was the plastic blade fuse that was going to catch fire before the wiring it was supposed to be protecting :/