c-40 battery charging [RE-wrenches]

Matt Tritt solarone at charter.net
Sat Oct 11 14:53:25 PDT 2003 

Greg,

I'd bet that the people who spec'd-out and installed those large UPS
would have included string fusing regardless of the cost (considering
the over-all cost of all those batteries) if it were actually needed.
After all, they are undoubtedly the result of the bidding process, which
would include all the requirements of the buyer, no?

All this discussion further emphasizes the desirability of using large
flooded industrial batteries in one string.

Matt T

-----Original Message-----
From: Greg Egan [mailto:gegan at renewalaska.com] 
Sent: Saturday, October 11, 2003 11:09 AM
To: RE-wrenches at topica.com
Subject: Re: c-40 battery charging [RE-wrenches]


Matt,

I've only worked on 30 or so large battery back ups for emergency 
lighting applications. I've never seen any of them fuse each string 
either. My guess is cost. It's not required by UL, and these banks were 
not in dwelling units like mine are. The other reason may be that these 
strings were all enclosed in metal cabinets.

I've never seen an AGM or any other battery catch on fire but I believe 
the wrenches on this list who say they did. Maybe fusing each string is 
overkill. However, none of the banks I've installed are in metal 
cabinets, and most of them are in peoples' homes.

Personally, the only reasons I can think of to fuse each string 
individually would be if it's mission critical equipment or it's in a 
dwelling unit.

Best,

Greg



Matt Tritt wrote:
> I see your point. I suppose my question would be related to what I've 
> seen in large battery installations in various crirical off-grid and 
> backup installations; that is, if fusing individual strings seems to 
> be such a good idea, why isn't it a standard procedure in large 
> arrays? Buss bars are.
> 
> Matt T
> ----- Original Message -----
> From: "Greg Egan" <gegan at renewalaska.com>
> To: <RE-wrenches at topica.com>
> Sent: Friday, October 10, 2003 11:23 AM
> Subject: Re: c-40 battery charging [RE-wrenches]
> 
> 
> 
>>Matt,
>>
>>Unless I'm missing something, the buss bar doesn't prevent one string 
>>getting overcharged by the other strings. The way I understand it, if 
>>string "A" has some kind of a short, parallel strings B & C will try 
>>to charge it. If we only have a fuse between the buss bar and the DC 
>>disconnect, it doesn't protect against overcurrent when one or more 
>>strings are charging the shorted string.
>>
>>Greg
>>
>>
>>
>>Matt Tritt wrote:
>>
>>>I think that with multiple strings the buss bar plan is the way to go

>>>to avoid having to fuse each string. If there is no reason for any 
>>>one string to take too much current the need for an individual string

>>>to have a fuse is negated. This is so weird. I used to connect all my

>>>parallel strings to a common buss until just a few years ago. A big 
>>>battery guru told me it wasn't necessary.
>>>
>>>The more things change the more they stay the same.
>>>
>>>Matt T
>>>
>>>-----Original Message-----
>>>From: William Miller [mailto:wrmiller at slonet.org]
>>>Sent: Friday, October 10, 2003 1:38 AM
>>>To: RE-wrenches at topica.com
>>>Subject: Re: c-40 battery charging [RE-wrenches]
>>>
>>>
>>>Learned Colleagues:
>>>
>>>
>>>Would it be advisable to install a class T fuse between strings?
>>>
>>>William Miller
>>>
>>>
>>>
>>>
>>>At 08:39 PM 10/10/2003 +1300, you wrote:
>>>
>>>
>>>>I have seen the result of an AGM meltdown.  It was a telecom 
>>>>installation and one block went bad, the rest discharged into it and

>>>>the result was an unbelievable mess.  One string is the way to go.
>>>>
>>>>Cheers,
>>>>Bruce Geddes
>>>>PowerOn
>>>>
>>>
>>>
>>>__________________________________________________________________
>>>William Miller
>>>Miller Power and Communications
>>>PO Box 50, Santa Margarita, CA 93453
>>>Voice :805-438-5600     Fax: 805-438-4607
>>>email: wrmiller at slonet.org
>>>http://millerpowerandcomm.com
>>>License No. C-10-773985 
>>>_____________________________________________________________
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>>>                                    H. L. Mencken 
>>>__________________________________________________________________
>>>
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>>
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>>981 Gold Mine Trail Fairbanks, Alaska 99712
>>Phone: 907-457-4299; Fax: 907-457-4290; Email: gegan at renewalaska.com
>>URL:  http://www.renewalaska.com
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