Today's Message Index:
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1. 09:22 AM - Re: Battery Cap Tester (jonlaury)
2. 12:17 PM - Re: Re: Battery Cap Tester (Robert L. Nuckolls, III)
3. 04:21 PM - Re: Re: Battery Cap Tester (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Battery Cap Tester |
nuckolls.bob(at)aeroelect wrote:
> Bob,
>
> ...snip
> Yesterday, after 24 hours on the XC-10, votage was at 14.67v. After disconnect
and about 1.5 hrs, it was at 14.04v.
>
> That's not a 'bad' value. There is a period of time
> after charger disconnect until the battery terminal
> voltage falls to its nominal resting value. There
> are small variations between lead-acid technologies
> but they'll generally fall into this range of values.
>
> [img]cid:.0[/img]
>
> These values are accurate only after a considerable 'resting
> interval' for removal of either a charger or a load . . .
> a 6-hour rest before measurement is probably reasonable.
>
> The fact that it will deliver 4 cranking cycles suggests
> that the battery is not seriously degraded . . . but a new
> we tested a new 18 a.h. battery on a high compression
> competition engine at 6 or 7 robust start cycles.
>
> Sounds like your battery is wounded but still serviceable.
>
> The self-discharge rate seems excessive . . . a reasonable
> hypothesis is that it's a symptom of the 'wounding'. Unless
> your design goals dictate that the battery support a
> e-bus for several hours, this battery may service your needs
> for some time.
>
>
> > I'll check it todayand I'll do the lamp test across the terminals too, and
report.
>
> Good move. Have you established an endurance load requirement
> for how you use your airplane?
>
>
> Bob . . .
Bob,
2 hour 75 watt (parts on hand) load result:
Begin test voltage: 13.6 (down .44 from previous day)
End test voltage , lamp connected: 12.4v
After 2 hour rest: 12.97v
All-electric airplane 97% VFR
Electrical power: 60a alt, 40a stby alt, 18ah PC 680
Minimum electrical load at 75% power = 15.5a (load decreases slightly at lower
power setting) EFI 3.5a, 1 Ignition 2.5a, 1 pump 7a, EFIS 1a, Xpdr 1.5a
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=404670#404670
Message 2
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| Subject: | Re: Battery Cap Tester |
Bob,
2 hour 75 watt (parts on hand) load result:
Begin test voltage: 13.6 (down .44 from previous day)
End test voltage , lamp connected: 12.4v
After 2 hour rest: 12.97v
Sounds like your battery's capacity is not seriously
hurt.
All-electric airplane 97% VFR
Electrical power: 60a alt, 40a stby alt, 18ah PC 680
Minimum electrical load at 75% power = 15.5a (load decreases slightly at
lower power setting) EFI 3.5a, 1 Ignition 2.5a, 1 pump 7a, EFIS 1a, Xpdr 1.5a
With dual power sources I think the risks
for continued use of this battery are low.
I'm at a loss to explain your observation of
accelerated self-discharge.
Bob . . .
Message 3
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| Subject: | Re: Battery Cap Tester |
>
>Bob,
>
>2 hour 75 watt (parts on hand) load result:
>
>Begin test voltage: 13.6 (down .44 from previous day)
>End test voltage , lamp connected: 12.4v
>After 2 hour rest: 12.97v
Hmmmm . . . according to data right from the horse's
mouth, a 75 watt load on a new PC680 should take
it down to 10.00 volts in about 2.2 hours. This corresponds
to a current of about 9A.
Emacs!
I'm pretty sure that Watts and Amps are CONSTANT values applied
by a 'smart' load . . . which resistors and lamps can only approximate.
Nonetheless, the fact that you were still above 12.4 volts after two hours
raises some questions. At first blush it appears your battery
is in REALLY good shape.
Bob . . .
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