I've set electric vehicle parallel strings up like this too. Once a
month I charge each string separately. At higher charge/ discharge
rates, the problems of unequal batteries increases dramatically. BTW,
single strings are not the magic bullet either; I've had single strings
with equal current through each battery, but some batteries would be at
15.5 volts, while others next to it would be at 13. The charge
controller shuts off when the sum of the voltages hits the bulk charge
V, but meanwhile some cells are chronically overcharged or undercharged.
(parallel strings no where to be seen)
Manzanita Micro makes a device that shunts current past batteries that
hit full charge in a string. This monitoring of each individual battery
is the state of the art right now for Li+ batteries in EVs.
I agree, we need much better battery management and safety devices for
solar. Its ridiculous some of the mundane issues we discuss here
sometimes, while hundreds of huge battery packs are just waiting for one
of us to drop a wrench across the terminals, with zero safety to
interrupt it, and its all NEC compliant.
Batteries themselves need to have a current limiting device built into
the positive terminal. Possibly the same device that controls charge
current to it too?
Dreaming up future BOS equipment,
Ray Walters
On 6/2/2011 7:44 PM, d...@foxfire-energy.com wrote:
What I like best about Mark's set up (the retired phone co. dude w/
half a hand), is that he can select individual strings at random. he
can eq an individual string, or top off a few strings and park them.
he can even run strings of T 105s, or even nicad (individually of
course) in the same system as L-16s and the like.. he just reprograms
the chargers (and logs it). I think he got the design from his days in
the Navy.
So boB, how about a controller that can be user programed to charge
multiple battery configurations with a soft switch? i.e. Bank A, Bank
B...? and while you're at it, maybe a multiple string DC box?
Something with a shunt and a breaker for each string? A four string
set up would be nice.
I could use 2% of your first million.
db
Dan Brown
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