Re: (ET) Fully charged pack voltage

["David Roden" <etpost drmm net>]

On 23 Apr 2009 at 11:42, Christopher Zach wrote:

> Under load, you can go down as far as 10.66 volts per 12 volt battery 
> before you run the risk of damage. 

That sounds like a Hawker specification.  A more standard number, nominal 
for flooded batteries, is 1.75 volts per cell *under load*.  This is where 
you should stop as soon as possible to avoid the risk of reversing one or 
more cells.  

Open circuit voltage is largely useless for this purpose.

> 
> Note also that these numbers are per *battery* not the whole pack.

Actually, it would be better still if you'd look at each *cell*.  Your 
battery's capacity is limited by its weakest cell.  When the first cell in 
the entire pack hits 1.75 volts, it's time to pack it in.  

It's perfectly possible for your golf car battery to read 5.3 volts and 
still have a cell at, say, 1.6 volts.  

Alas, measuring the voltage cell by cell isn't ver practical, given the 
construction of modern golf car batteries.  (Other old timers will 
probably 
remember the days of batteries with external intercell connectors, readily 
accessable on top of the battery.)  This is why you should equalize every 
10 
cycles or so.


David Roden - Akron, Ohio, USA

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