Re: Almost had a battery fire!

 wrote:


Not at all.  I'm considering fusing each one now.  Might have lost the
whole house.

What does one fuse each link at?  A lot of current can flow initially.



Kirk

"There's a lot to be said
 for a blow to the head", BOC.

www.sandpoint.net/captkirk
www.stormyacres.com

 
The first line of business is arranging the wiring where the current
draw off of each bank will be equal to the current on the others.
(Witch is a good idea in any situation.)

Then fuse each link to equal 2 times the maximum normal draw.

4 banks on a system that pulls a 100A maximum will require
a 50A fuse on each bank.

8 banks with 100A total draw will require a 25A fuse on each one.

The system should be able to operate at maximum load
with half the battery system disabled.

And when the complete battery system is operating, the
bank can stand large surges without blowing the fuses
unnecessarily.

It is preferable to have the fusses in battery holders.

Use the normal class k fuses that you can get at your
home improvement store.
They are rated at 10,000A dc interrupt and they are
readily available.

And cheap!!!!!!!
about $0.95 to $1.15 a piece.
as compared to $20+ for a class T fuse.

And they are fully enclosed so they won't ignite any
vapors when they blow.

 Reading this has me thinking about implementing this on our system. We
live far enough out that everyone we have called is reluctant (and flat
out refusing) to insure us.

I am wondering however, in our system we have 12 L16HC's running into a
SW4024. I have each string wired so it would be very convenient to add
the fuse. Would we fuse at the max draw of the inverter? Or our maximum
anticipated draw?

To date we have never come close to the capacity of the SW4024. I think
the max we have ever read on our trimetric was just under 40 amps. We
are in a very light power situation right now but when we finish the
main house it will be a bit more but we are guessing not a lot.

Mark

N9WOS wrote:

 

It is your decision.
If you had a 200A breaker for the inverter.
I would put a 100A fuse in each string.
That would give me a total of 300A current draw
before the fuses will blow.
If the current level reaches that, you know the main breaker
has failed.
The only problem is the battery failure will have to reach
severe proportions before the fuse to that bank will go
when you have a 100 amp fuse on each one.

The smaller the fuse size, the lower the failure level
the batteries will reach before the link will blow.

You could put a 30 or 40 amp fuse on each one and
get a total system current of 90A or 120A but...
The fuses will blow before the main breaker trips.
And replacing all the fuses is a pain.

Normally you will fuse them so your main breaker
will trip before the fuses will blow.
The fuses on the individual battery strings are normally there as a last
resort.
If everything else fails and the S*)+ hits the fan, they will save your
butt.

If the breaker fails to open on a massive overload, they will blow.
If the wires that go to the breaker short, they will blow.

And when you have a bunch of small fusses in the individual strings,
instead of one big one after you combine all the strings.
You will protect the batteries from each other.
Batteries can fail just like any other piece of equipment.

And since they are NOT something that a normal user will
deal with under normal operation, the requirement of having
the fuse disconnected from the circuit for replacement, doesn't apply.
Anyone that works on them should know what they are doing.
If they blow, the cause of them blowing should be answered before they
are replaced.

It isn't something like the main fuse or breaker.
where, if you overload the system with you new toy,
you just put a new fuse or reset the breaker.
If you blow the ones in the strings, you have got serious problems.

Another added feature of fusing each string is, you can electrically
isolate each string for maintenance work.

(ie)
Remove the fuses for that string to remove the current on the wiring.
That way, you can repair or replace connections on that string without
shutting down the system.

And if you totally mess up and hook one battery up backward in
A string, it will save you from total destruction.
And finally last but not least,
If your battery room has a lot of metal stuff that
Can possibly short directly to the battery stings in question.
Or there is a good possibility of things shorting from one string to
another.
It would be a good idea to put a fuse in the negative end of the strings as
well.

If people think I am paranoid, I have one thing to say.
YOU BET I AM!!!!!!!!!!!!!!!!!!!!!!!
I am alive and I intend to stay that way!!!!!!!!!!!!!

 

I have seen varying results with different brands of fuse holders.
Some are better than others.

I'll let you in on a trick to get a "SOLID" connection with
that type of fuse no matter how many years they are in use.
Two words, "OX-GARD"
Conductive anti oxidant grease.
lightly coat the two copper ends of the fuse and put it in place.
It will maintain a solid connection for years and years.
Be it wind or rain or acid, the connection will stay true.


A good point
They are a definite winner in the reliability category.