Battery explosion [RE-wrenches]

Bruce Geddes b.geddes at clear.net.nz
Fri Dec 3 02:05:18 PST 2004


 

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On the subject of charge controlers versus c rate.  I will never put a
panel, even 5W, onto a battery that is likely to be unattended and ignored
for any length of time.  The resultant loss of performance from drying out
is simply not worth it.  I have an old 450Ah/C5 traction cell battery
running with one of the old Siemens M65's (33 cell 43W) and that will cause
very audible gassing when charging.   It runs through a c-controller even
though it only drives an electric fence.  Electrolyte needs topping up
around twice a year.

Now consider 2.95A into 450Ah (535Ah C20) is near to 1/200 and can cause
gassing.  How would 5W go onto a smallish starting battery?  For the cost of
a sunsaver it is simply not worth compromising a job to save a few bucks.

I guess the answer to the question is really to consider the self discharge
of the battery.  If your panel is only marginally above sd rate it probably
won't have enough grunt to gass.  If it is capable of bringing the battery
up from a low state of charge, even over a period of days, it can gass the
battery dry (over days or weeks or months).

An interesting and very topical thread as I am currently putting a system
into a holiday cottage that is rented out so needs a high degree of
automation (so visitors don't push the wrong buttons).  The gen set may not
run for months, then be expected to burst into life if needed.  A 10W panel
with a sunsaver will ensure it can as well as run a DC fluoro in the
generator shed from the starting battery for maintenance purposes.

Bruce Geddes
PowerOn

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