[Nut-upsdev] Re: Changes to megatec.c

[Frank van Wensveen]

Hi, Charles,
On Wed, 2 May 2007 07:58:08 -0400, you wrote:

> > Will that be enough to make it useable as a contribution? I believe
> > the more sensible values for 36V UPS'es will be useful to other models
> > than the one I have, too.
> 
> Sounds good, but I don't think I saw it hit the list yet...

I now have the following in megatec.c:

static BatteryVolts batteries[] = {
	{ 12,  9.0, 16.0,  9.7, 13.7 },   	/* Mustek PowerMust
600VA Plus */
	{ 12, 18.0, 30.0, 18.8, 26.8 },   /* PowerWalker
Line-Interactive VI 1000 (LB at 22.3V) */
	{ 24, 18.0, 30.0, 19.4, 27.4 },   /* Mustek PowerMust 1000VA
Plus (LB at 22.2V) */
	{ 36,  1.5,  3.0, 1.64, 2.31 },   /* Mustek PowerMust 1000VA
On-Line (LB at 1.88V) */
	{ 36, 32.0, 42.0, 33.0, 40.8 },   /* Mecer / Mustek 2kVA
ME-2000 - Added FvW 1 May 2007 */
	{ 96,  1.5,  3.0, 1.63, 2.29 },   /* Ablerex MS3000RT (LB at
1.8V, 25% charge) */
	{  0,  0.0,  0.0,  0.0,  0.0 }};  /* END OF DATA */

You will notice that I made the following guesses:

- A 36V UPS should have a battery clamping voltage of between 32 and
42V. Assuming the possibility of a 'low' reading being reported by the
UPS, it should at least be 32V or more. The float charge voltage of
13.62-13.64V as recommended by sealed lead acid battery manufacturers
should keep it under 42V. Overcharged or worn batteries might have a
highere clamping voltage, but more than 42V will move it into the
regions of 48V power supplies.

- Battery manufacturers recommend a minimum of 10.8V for a 12V battery
as the cutoff discharge voltage (further discharge will cause battery
damage) but the UPS is likely to shut off before that, so I
guesstimated 11V for a 12V cell to be a reasonable "empty battery"
voltage. 

- The float charge (clamping) voltage for a fully charged 36V battery
if 40.9V but I've subtracted 100mV to allow for tolerances



Kind regards,
    Frank van Wensveen

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