Hi mark.

25-Apr-03 22:26:14, mark lewis wrote to Matt Mc_Carthy

 ml> i've been looking at this and thinking about how to prevent problems
 ml> with the charging system in the UPS'... my current thoughts are to
 ml> use some diodes of sufficient size to allow the batteries to supply
 ml> power but not accept the charge from the UPS... instead, i'd use a
 ml> charger for the batteries... maybe even one per battery... i'm going
 ml> to try an ascii drawing..

 ml>        ===== + buss bar ======Z----+-----------
 ml>       /                             \ +        \
 ml>   ups                                battery    charger
 ml>       \                             / -        /
 ml>        ===== - buss bar ======-----+-----------

 ml> Z is a diode... but which one? and i only need one on the positive side,
 ml> right?

one rated 60A or so from an autoelectrician,

but with a silicon diode you lose between 0.6 an 1 volt in passing through
it and that's 5% of your batteries output.


ifthe UPS is designed to cut out when the battery voltage drops to a set
level you'll not have the full capacity of the batteies available either.

you could use a FET I guess but I don'y know where yuo can get one that
size and you can't eaily parallel FETS for increased current,

a better (if slightly more complex) solution is to use a relay in there.

if you can't find a high current relay with normally closed contacts
you can use a starter motor relay with a low power NC relay to activate
it, and run it off a wallwart to detect the power failure...

    replacement for "Z"

          ~~T~~
   ====---O | O---+------------------
            | ____|               (+)
            #(_
      RL1   #(_         O----.
            #(__     _-~     |
                ~---~ | O--  |     to external batteries
                   __ |      |
                  | _)#      |
  from    --------' _)# RL2  |
 wallwart ---------__)#      |
                             |    (-)
  =====----------------------+-------

 ml> i found a sticker i hadn't noticed before on the plastic casing
 ml> holding them all together..

 ml>   0820-2016/12v-25AH/2297W

 ml> if that W number at the end is wattage, whoa! >

you could probably get 2.3KW out of the the pack, once atleast.
it's only about 200A , which would be no problem for a car battery.

 ml> 15min    60min    90min    5hr     10hr
 ml> 54.3     19.3     14.0     4.85    2.55

however it is about 4 times the highest discharge rate listed so it could
damage something internal to this battery...

 ml> i'm guessing that these numbers are pretty good but i don't know exactly
 ml> what
 ml> they are representing, ATM..

how long the battery can supply the stated current for before being totally
discharged

 ml> my biggest problem is going to be determining what charger to use on
 ml> these
 ml> packs..

if they're all hooked in parallel a 2A or 4A charger with an automatic
cutback to trickle mode would be ideal  (amd probably available from an
automotive tools place)

 ml> possibly it'd be better to take a look at doing this with marine
 ml> batteries with
 ml> the same attention to adding them in but charging externally as we've
 ml> talked
 ml> about..

They'll probably want venting too unlike the gell cells.

 -=> Bye <=-

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