Tim: Have you looked at moving your positive inverter lead so that it draws through all the batteries equally?
This way the starting loads don't go through the 150 amp rated bus bar but rather through the higher rated 500 amp shunt.
The starter loads should NEVER be run thru a shunt.
1. too small a load over time,
2. a shunt is basically a measured resistance,
A FUSE is a measured resistance .
Just do what 100% of the boats do and forget about measuring start amperage on the OC.
Timjet is correct. FF is pretty much wrong on on all counts.
It is just fine to run starter loads through a shunt provided the shunt is rated to carry the current. A shunt is a measured resistance, but so small of a resistance that an engine starter will never see it. A 500 amp, 50mv shunt like most all of these monitors use only cause a 50mv drop with 500 amps of current. If you are starting from this house bank, and don't run the start current through the shunt, you have lost accurate measurement of the battery bank. I've started my 135 Lehmans through a 500 amp shunt for almost 13 years with no ill effects. Mater of fact, I've installed many, many shunts in starter circuits (properly sized) and have NEVER seen a shunt failure.
A fuse IS NOT a measured resistance. It is a fusable link.
100% of boats DON'T forget about measuring start current. I've seen many that do, including mine. Generally, if they have a separate start battery it doesn't get measured, but if they are started from the house, and they have a properly wired battery monitor installed, they do.
That's not a breaker/ fuse I would use it won't handle high inrush currents.
Bill
bglad wrote: What is not good is to have an inverter connected to the DC battery bank without a switch to shut it down if it starts smoking or other silliness. Much quicker to toggle a switch than find your tools or fuse puller...(endsnip)
Exactly correct. As I mentioned before, I've installed dozens of inverter / chargers, mostly 2000 to 3000 watt. I always install the proper size fuse and wiring, based on the Inverter manufacturer's recommendations, and always install a dedicated switch just for the inverter where you can switch it off without interupting the house circuits. I also only use the class T fuses because of the high current capacities of the battery banks normally associated with inverters, and the chance of an inverter failing with a direct short. An inverter is the only high current device that I've ever seen fail that way (direct short) and I've seen it happen twice.
A FUSE is a measured resistance ..
psneeld wrote: So why recommend additionl switching..which the manufacturers don't always recommend when the class "T" fuses did their jobs? (endsnip)
Well, this has been explained several times, but the switch is to isolate the inverter incase of a fault, or just for maintenance / testing. If you don't want to pony up the extra $25 on a $2,000 job to make it a better, safer installation, don't. I'll continue to do things right.................
Good grief, this thread is getting ridiculous. I think I'm done.
After all this discussion, I'm still curious as to why a simple stand alone 12V starting circuit is felt by some to need "protection" beyond good wiring and logical cable runs.
It seems I'm not alone.
In electronics and electrical engineering, a fuse (from the French fuser, Italian fuso, "spindle"[1]) is a type of low resistance resistor that acts as a sacrificial device to provide overcurrent protection...........
Fuse (electrical) - Wikipedia, the free encyclopedia
What's ridiculous is not answering a simple question...
IF the fuses did what they were supposed to....then why the extra switch when not called for by the manufacturer?
Wikipedia is a source for school children to find information without doing actual research themselves. It is not a reliable source for technical information.
I used that stuff for many years on a daily basis. Of course I updated it when necessary.Yeah, but it is a lot easier to post a link from Wikpedia than scanning those 50 year old EE text books on my shelf.