T&T: Battery monitor

[Truelove39 at aol.com]

Hi Steve,
 
I believe you'll be OK with the standard 500A shunt. I have a Link 2000  
which I'll soon install and it has a 500A shunt standard as well - I won't be  
changing it even tho' our starter draws almost that.
 
A shunt should not be sized to carry maximum expected load. Standard practice 
is to size it so that it carries a continuous load  of no more than 2/3 of 
its rating. Exceeding this will likely  change the accuracy of the shunt and may 
eventually destroy it. Short-term  loads such as starters which draw or even 
slightly exceed maximum rating  are allowable as long as the shunt temperature 
doesn't exceed 80C. It's  unlikely that typical trawlers have starters which 
exceed 500A although they may  be near to that. Most windlasses for boats our 
size seldom draw more than  150A. I don't know anything about thrusters except 
from time to time I  wish we had one! It would be best to locate a shunt 
outside the engine room and  outside the battery locker too if you have lead/acid 
batteries, as the  fuseholder terminals will likely corrode otherwise.
 
Regards,
 
John
"Seahorse"


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