A word about NASA MARINE

[boatmike]

Er, think you've misunderstood the purpose and installation of the BM1.

It's meant for monitoring the leisure bank, and shouldn't see massive start up currents if wired in correctly.

The latest model will also measure the voltage of the starter battery, but not the current.

OK so what happens if your engine start battery goes dud and you need to switch over to the service battery to aid starting? Also in this day and age of inverters etc are you convinced that you wont even momentarily pull higher amps? Depends on the boat of course but on mine with twin alternators of 70 amp capacity each I would worry at all that current going through a 100 amp shunt. Mine is 500 amp and even then only fitted to service battery bank. Tend to agree it's at best marginal and at worst dangerous.

 

[Trundlebug]

OK so what happens if your engine start battery goes dud and you need to switch over to the service battery to aid starting? Also in this day and age of inverters etc are you convinced that you wont even momentarily pull higher amps? Depends on the boat of course but on mine with twin alternators of 70 amp capacity each I would worry at all that current going through a 100 amp shunt. Mine is 500 amp and even then only fitted to service battery bank. Tend to agree it's at best marginal and at worst dangerous.

I think NASA state that temporary instances of over 100 amps (e.g. when bridging across and using as starter) won't cause any damage.

Other than that, if your service batteries are routinely seeing discharges of over 100amps for any period, I would be worried. Something badly designed / seriously wrong somewhere, you'd be better off with a big 240v genny.
Your service batteries won't last long at that rate, minutes rather than hours regardless of capacity

 

[Jonmendez]

Nasa ok with me!

We have had NASA - separate speed and depth for the last 6 years on our school boat, boat is out most weeks and never an issue save for a new spindle on the log after we tried to anti foul it to death!! Very pleased and like the simple no nonsense approach - not to much for people to fiddle with and break.

Jon