Dual battery set up help

[stevemid]

Turned isolator off, than disconnected fuse that feeds switch panel, dropped voltage from 12 to 9v from negative to boat frame. This boat will be the end of me haha

Did you have both isolator switches turned off when you measured this 9v? I'm assuming the negatives of all the batteries are still tied together even though you had removed the neg leads from the motor?

[Mischief Maker]

Aux batteries both brand new. Found my issue with volts on neg to boat was the dual volt metre gauge, I had the neg off from it but the gauge doesn't go through isolator from positive. So I confident I sorted that. What I also found which I curious about is, from beg bus to boat hull I get circuit so one at a time I took each neg off, I tracked it down to the VHF frame/bracket is connected to hull, now I find this interesting because when I originally turned the system on we tried turning the VHF on and wouldn't work (could I have f---Ed it) because originally that bus bar only had a neg fro batteries coming from back to run everything but now I have introduced a power in source (charger,solar) could this be using the neg to aux battery and also this wire back through hull to create circuit, also could this be why this volt/amp metre fluxuates all over joint causes there's not just one path to negative through shunt but also a path back through radio neg then chassis back to battery ??

[scottar]

It is a possibility that that was happening. Is the radio in it's cradle or is it flush mounted. Does the radio actually work now or is it dead? Best bet would be to try and isolate the mounting somehow - starboard or similar.

[Mischief Maker]

Yeah that's the plan I'll try and isolate it or buy a new one with plastic mount, keep you posted

[Mischief Maker]

Connected back up seemed to run ok charge ok., but now after few minutes it went out on alarm on gmi20 gauge and motor cut out, the alarm was "low system voltage alarm" it all seems to charging sweet when measuring voltage, I even took relay out which cuts new aux set up out, I did take all negs off but got them all back on, I had it running on the muffs when it did it, any ideas, starting to wish I didn't touch it haha,

[scottar]

I think you are pretty quickly approaching the "call the guy" stage. The guy would either be a decent marine leccy or Zuk tech or both. Other than that the best thing to do would be to draw up an accurate connection diagram for starters.

[Mischief Maker]

Yeah will check connections to start with I didn't have gmi20 on to start with then turned on and it started so will try connections, pretty we'll come to conclusions I hate auto electrics