[Nut-upsuser] Eaton 5PX 3rd party batteries

[Greg Troxel]

Dan Langille via Nut-upsuser <nut-upsuser at alioth-lists.debian.net>
writes:

>> On the website, they say 5.73 pounds (5 lbs 11.6 oz).
>>
>> Two of the batteries were 5 lbs 11 oz.  The rest were all 10, 9, or 8 oz.
>>
>> See my bar chart at https://bsd.network/web/@dvl/113555334752647203
>
> The batteries are all within 3% of the expected weight. Seems good enough for me.
>
> I gave some thought as to how to distribute those 16x batteries within the UPS (4x) and the external battery unit (12x).
>
> In the following, I'm omitting the 5lb part of the weight and mention only the ounces.
>
> Not that I think it will make much difference, but I'll put all the four equal batteries into the UPS (4x 10oz batteries).
>
> That will leave the following for the external pack:
> '
> * 2 x 11
> * 1 x 10
> * 7 x 9 
> * 2 x 8
>
> The other choice I'd make: put 2 x 11 and 2 x 10 in the UPS, leaving the external battery
> unit with:
>
> * 3 x 10
> * 7 x 9 
> * 2 x 8
>
> I don't know enough to know if this matters and I expect I'm merely overthinking this.

You are definitely overthinking it :-)  Perhaps you've previously been
diagnosed as a nerd!

But, I would either put the 4 strongest in the UPS, or the 4 weakest,
making the external pack better, since it is more important.

I would suggest that you get a West Mountain CBA, if you want to
continue to overthink this.  We are assuming that more lead is more
capacity, but there are also weak cells, not clearly related to missing
lead.   What really matters, IMHO, is how many Ah one can pull out of
the battery, and measuring that directly seems more direct.

There's also the question of discharge rate.  I used to use standard
rates of 1 A, larger for bigger bateries, smaller for little ones.  This
is contrary to industry norm which is a 20h rate.   Then I had batteries
I wanted to return, and realized I really needed to test at the
specified rate.

So now i do 20h rate, which which means nameplate capacity / 20h, so 450
mA for a battery specified at 9 Ah.  With end-of-test at 10.5V, which
you'll find on the spec sheet.

Of course, the actual time will not be 20h, and one could attempt to
find the rate which leads to 20h, but I don't think that's a sensible
thing to do.   Basically, if I get > 8.5Ah when discharging a 9Ah at 450
mA, I call it good.   And > 8 Ah I call it ok, sort of they are making
an 8 Ah battery and the marketing people call it 9.

I will probably be getting some new batteries over the next few months
and will test  them on intake, and weigh them too.

Thanks for posting about your journey; it has been illuminating to me.