mad_pete Posted March 23 Share Posted March 23 So mad rush to get on with it, I might have ever so slightly connected my new battery slightly back to front. Bit of spark and popped it round the other way. Alternator is still putting out 13.7, stereo blew the fuse but is back after replacement and engine still good to start so while I wouldn't recommend it seems that I did come away somewhat okay from that. 1 Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted March 23 Share Posted March 23 It happens, it is in part what fuses are for! Quote Link to comment Share on other sites More sharing options...
mad_pete Posted March 24 Author Share Posted March 24 When I did it I was like oh no all the permanently on electrics… that I don’t have. Still if the megasquirt had died that would be sad face. 1 Quote Link to comment Share on other sites More sharing options...
Escape Posted March 24 Share Posted March 24 Most electrics can handle reverse polarity, it's only when electronics are involved it becomes a problem. Like the radio. Luckily most other stuff is not permanently live, not on a simple/older car anyway. The MegaSquirt is only powered when you switch on the ignition, by then the sparks would have told you something was wrong so you would have corrected it (like you did). Glad it was just a reminder and no harm done, we've all been there. 😉 Quote Link to comment Share on other sites More sharing options...
TSD Posted March 24 Share Posted March 24 (edited) Megasquirt has (or did in early versions anyway) reasonable reverse polarity protection. If properly fused and wired, it would (or should anyway) just take out the fuse without further damage. I think the ISO specs covering auto electronics include 60 seconds of reverse polarity without damage as well as brief pulses of much higher voltages, e.g. load dump to -100V caused by removing the power supply to an inductive load, like a motor. Electronics generally has to be designed with 'finger trouble' in mind, because given the chance, most semiconductors will happily sacrifice themselves to protect the fuses Edited March 24 by TSD cant type 2 1 Quote Link to comment Share on other sites More sharing options...
Ed Poore Posted March 28 Share Posted March 28 On 3/24/2024 at 11:48 AM, TSD said: I think the ISO specs covering auto electronics include 60 seconds of reverse polarity without damage as well as brief pulses of much higher voltages, e.g. load dump to -100V caused by removing the power supply to an inductive load, like a motor. Pilfered from an app note by LittelFuse but shows some of the stuff the electronics is meant to survive. It's actually pretty simple these days to design electronics to handle automotive stuff and reverse polarity etc., there's quite a few chips these days that do it all in one. 1 Quote Link to comment Share on other sites More sharing options...
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