2023-03-13, 01:05 AM
(2023-03-12, 05:09 PM)HeviiSailor Wrote:(2023-03-12, 02:55 PM)Techstyle Wrote: ...I decided to get a different one and bought 300A ones from Aliexpress... Is your plan to use one for all the low side or one for each battery?...
Hey, that's my Chinese shunt!
Even at 300A I'm a bit concerned. As mentioned earlier, this concern is driven by the shunts used by Victron et al. However those have probably been sized very conservatively for monster power-boats with all the accoutrements of a modern-day condo. My 30' sailboat, mostly running a few led lights and old B&G instruments along with the Rpi, hardly competes. Nevertheless, I'll throw an ammeter around the main lead during cranking to see just what's being drawn.
If I have enough capacity, I'll monitor the entire system from the low side.
I read somewhere that a Cracking Yanmar 3GM30 is a maximum of 460A - that seems a lot. That would be split across 3 shunts for me, so the original shunt would have been about a 75mV drop, the new one would be about 37.5mV. Either one I think would be fine, but when I am in a long distance race and using 5A, for gauges, instruments and nav lights, the drop would be 1.25mV for the 300 and 2.5mV for the 150 and I just hope there is enough resolution. like you said, there is some testing coming up and if the current draw is much lower, I could always cut off one of the 3 resistors from the shunt!!