Myles,
This topic is not often discussed here and so it is about time. I suggest each of us with electric boats take the time to examine your electrical setup and ask whether fuses are located in the right places and have appropriate values. Also, newbies should take this issue seriously and incorporate proper protection at the right places.
In my case, I have 2 Class T fuses installed (each 150amp I believe)---one in the main power leg very near the battery bank POS and the other attached to one of the battery posts of the other half of my pack. I suspect this is adequate for my 36v setup, but looking at failure modes and effects might point out some other risk.
You should have one of these fuses associated with and located closely to each of your battery packs or sub-packs.
So as example, if you have a 2P6S golf cart battery configuration (2 parallel strings of 6 batteries in series) with batteries bundled in 4 groups of 3, you should have 4 Class-T fuses.
My 1P6S configuration should have just 1 fuse, but I have the series pack split into 2 groups of 3 and so have a 2nd fuse on the other pack---the 2nd fuse is actually legacy from when I had 2P6S with 2 groups of 6 batteries in series---but it turns out that it's good to have that 2nd fuse given the pack is still split despite it not being a 2P configuration.
In case this helps-
-Myles Twete, Portland, Or.
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Kirk McLoren
Sent: Saturday, September 24, 2011 7:55 AM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Over-current protection
If the source impedance is low (such as a battery bank) short circuit current can be huge. AC breakers fail as well as DC. When the utility company improved their pole pigs a lot of fires resulted.
As a result the code was changed that fuses were required on any load above 2 horsepower. Thus your central air has a fused disconnect.
Terrible helpless feeling to watch a meltdown and unable to stop it. A fuse is much cheaper than a new boat or house.
May you be in heaven a half hour before the Devil knows your dead.From: Tom <boat_works@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Friday, September 23, 2011 10:17 PM
Subject: [Electric Boats] Over-current protection
The Oct/Nov issue of Professional Boatbuilder magazine has an article on
the design and installation of large battery banks.
In a side bar, the author discussed protection of large banks with Wayne
Kelsoe, VP of electrical engineering at Blue Seas Systems. Among the
author's conclusions is that Class-T fuses are preferred over circuit
breakers for protecting large battery banks.
..."a common failure mode after a short-circuit fault is for the
contacts to fuse when reset. How many of us have reset a circuit breaker
without investigating the cause? If the fault still exists, and the
over-current protection is compromised, a fire could result. At the very
least, the breaker will be internally damaged, and will not reset,
allowing the circuit to remain open. Boat operators often carry spare
fuses, but how many carry spare primary circuit breakers?"
Anybody in the group had any experience with the type of circuit breaker
failure that Wayne is talking about?
-Tom
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