Re: (ET) new batteries

[Christopher Zach <cz alembic crystel com>]

Michael S Briggs wrote:
> Under-load voltages are largely meaningless. THe voltage drop across the 
> internal resistance depends on the current being pulled from the battery 
> pack. So, you can get a pretty low "under-load" voltage from a fully 
> charged battery if the current is high enough. And likewise, if you are 
> only pulling a very small current from the batteries, a battery that is 
> fairly dead can still have a decent voltage across it if the current is 
> minimal.

I beg to differ: Under load voltages are the only ones that really 
matter since that's what we use our tractors (and cars in my case) for.

The floor voltage is 10.5 volts per battery on a 12 volt battery, or 
5.25v on a 6 volt battery. Draw it lower than that under load and your 
battery will be in danger of going bad. Some batteries can go to 10v 
(5v), but you don't want to draw it much lower than that.

On my car (50 batteries, 2 strings) I am happy if the pack is above 11.5 
vpb when driving around at a 60a draw and 11.0v while accelerating 
(120-150a draw).

A 12v battery is considered "dead" when it can't deliver it's C rating 
with a voltage >10.5v.

Chris