Re: [electricboats] Grounding.

Keeping the 48 VDC system entirely separate (or virtually so) from both 12 VDC and any AC systems just makes logical sense to me.  And I don't disagree with your thought on fusing "both legs" (which I take to mean both positive and negative sides of the battery pack), but I'm still pondering the thought experiment of lighting striking an electric auxiliary sailboat.  Are you thinking that fusing off both sides may prevent or minimize damage in the event of a lightning hit?

If fusing both legs, what's your opinion on fusing both plus and minus of the cables between the on-board charger(s) and where they interconnect with the batteries (separate buses presumably)? 

I'm still thinking about a couple of further design points.  Trying to keep the 48 VDC and 12 VDC systems completely apart is complicated where a stand-alone 12 VDC battery pack is provided to drive boat accessories & instruments and also for battery monitoring and charger controller where the designer wants to avoid using the traction battery for anything except driving the motor.  [In my test-bench setup, I'm pulling 12 VDC from the traction batteries through a step-down transformer, but once installed and operational, I think driving the monitoring and charger control circuits from a separate 12v battery pack, as is done in automobiles, makes sense, though it does require an additional charger on board.]

And dockside, charging from shore power, the 48 VDC and AC systems are certainly connected through the chargers.

My setup is pretty simple, with no inverter, no generator, and no AC usage except while dockside.  Folks with generators, inverters, and lots of AC-powered conveniences have a much more complicated life!

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On Sun, Dec 6, 2020 at 1:24 PM James Marcroft-Clark <greenlinepcs@gmail.com> wrote:

Thanks, good to know. Since I only saw it in one place and you got word straight from the horse's mouth, I think you're probably right. I think it still makes sense to make it a floating system, because of galvanic corrosion and the rest to those in the water in varying saline conditions. I think it's only a matter of time, and perhaps it's even happened already, that an electric sailboat will be struck by a lightning and current from the lightning bolt will reach batteries and cause a catastrophic failure. I think it just makes sense to follow the precautionary principle and fuse both legs.

On Sun, Dec 6, 2020, 09:08 THOMAS VANDERMEULEN <tvinypsi@gmail.com> wrote:

James:

I was quoting the ABYC standard when I stated that E-30 applies to 60 VDC systems.  Also, as mentioned, I had directly confirmed with ABYC that it would NOT apply to the 48vdc (nominal) system I would be installing.

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