I would concur the best course is to avoid higher voltages and stay below 48V. There is a good reason why the standards change dramatically above 48V and if you're operating in a salt spray environment on a vehicle with a lot of relative motion that could easily promote wire chaffing scenarios you have a formula for disaster and death with high direct current voltages. IMO (Not to mention what could happen if you're boat is sinking)
My understanding is the problem with chassis grounding your higher voltage systems, especially 120VAC, on your boat is the potential for galvanic corrosion if you develop a partial ground fault in ANY of your equipment or appliances that's not big enough to trip the breaker. This allows current to leak from your boat and can ruin anything bonded to your ground thruhulls, prop, shaft, etc. That's why I would prefer the use of a dedicated dyna plate for a high voltage ground. Another good but also expensive solution is a GFI protected main breaker but the objection to this is often nuisance trips.
While I do NOT recommend it to others, my high voltage systems on the Arc are not grounded because of a fear of galvanic corrosion within the steel mesh of the ferro cement hull that might slowly dissolve my boat from the inside out. If I had the extra cash I would definitely install a dyna plate and that is my intention at some point in the future.
Capt. Carter
www.shipofimagination.com
On Thursday, March 1, 2018, 10:11:36 AM EST, James Lambden james@electroprop.com [electricboats] <electricboats@yahoogroups.com> wrote:
The Resistance monitor provides any necessary bleed path.
Its my understanding that any differences in potential between the 48 volt bank and ground have very little energy and are at most static buildup charges. Even in a lightning strike that hits the grounds of the boat, the potential difference is very small.
What is more of an issue is if the 48 volt charger fails and puts AC line voltage onto the battery pack. At that point, the Ground Fault Monitor should disable any AC charging source. Since AC is grounded, the Resistance monitor will pick up this fault.
James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
On Mar 1, 2018, at 6:10 AM, Chris Morriss chris.morriss@ouroboros.myzen.co.uk [electricboats] wrote:
Certainly float the ground, and use double-pole breakers, but I suggest you add resistive bleed paths from the + and - feeds to the boats hull or other metalwork to prevent a potential difference building up.
You could also use symmetrical transient absorbers (Transorbs or similar) to ensure that any PD doesn't exceed SELV safe limits.
On 01/03/2018 13:12, king_of_neworleans wrote:
Good answer, makes sense. I know you have repowered quite a few boats, James. Have you tried doing any with grounded banks, and actually seen electrolysis become a problem?
---In electricboats@yahoogroups.com, <james@...> wrote :
At 48 volts, The reason why we float the ground is to prevent possible corrosion of the through hulls and propeller. At higher voltages, the ground is floating for safety and reliability purposes.
Floated ground systems can be monitored for ground faults, whereas grounded systems cannot.
Floated Ground Systems require double pole breakers throughout. The negative is treated as a live wire requiring circuit protection.
I like isolating the 48 volt battery (floated ground) because it makes it easier to troubleshoot and to monitor. When you add a Resistance Monitor, you end up having an on board megger for every circuit.
__._,_.___
Posted by: Carter Quillen <twowheelinguy@yahoo.com>
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a New Topic | • | Messages in this topic (12) |
Have you tried the highest rated email app?
With 4.5 stars in iTunes, the Yahoo Mail app is the highest rated email app on the market. What are you waiting for? Now you can access all your inboxes (Gmail, Outlook, AOL and more) in one place. Never delete an email again with 1000GB of free cloud storage.
.
__,_._,___
No comments:
Post a Comment