low voltage alerts
Posted: Sun Feb 19, 2012 5:41 pm
See below.
On Tue, Nov 3, 2009 at 5:28 AM, Ken <klehman@albedo.net> wrote:
FYI - I use the low voltage warning device from Perihelion Design (
http://www.periheliondesign.com/lvwaabm.htm) which triggers at 12.7 VDC
+/-0.15 V. It works very well. Although it's a little pricey ($82) it can
also function as an auxiliary battery management device (or external circuit
switch on alert) if desired. The unit is fully enclosed, very lightweight &
basically bulletproof. Perihelion tech support is excellent. (I have
modified the suggested external circuitry somewhat for my needs.) Highly
recommended.
Of course, most modern EFIS's will also give low voltage alarms, with
adjustable trigger points. Mine is set to warn at 13.1 V, as a redundant,
earlier warning.
Perihelion also sells a simple, easy to install low voltage warning light
(only) that trips at 13.0V, for $39. (See http://tinyurl.com/yj7g5jh) If
anybody wants one of those, I believe I have an extra one I'll sell for
less.
...
As Ken suggests, with AGM batteries it's important to use the correct
charger. It is not enough that a charger is described as "automatic" or
"multi-stage" or "will not overcharge", etc., because correct charging rates
and transitions between charge rates, are also important. Bob Nuckolls has
tested several chargers and written on this subject as well.
Ron
254R
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On Tue, Nov 3, 2009 at 5:28 AM, Ken <klehman@albedo.net> wrote:
...Most instruments and avionics start failing below about 11 volts at
which point the battery is already 90+% depleted and the engine won't
run for more than a couple of minutes. I believe I have my alarms set
for about 12.8 volts. As Ron mentioned, Bob Knuckols at aeroelectric.com
is the trusted authority. Some of the EAA info is very inaccurate. By
the time a battery is noticeably poor at starting an engine, it has long
since lost much of its reserve capacity to supply energy after an
alternator fails.
FYI - I use the low voltage warning device from Perihelion Design (
http://www.periheliondesign.com/lvwaabm.htm) which triggers at 12.7 VDC
+/-0.15 V. It works very well. Although it's a little pricey ($82) it can
also function as an auxiliary battery management device (or external circuit
switch on alert) if desired. The unit is fully enclosed, very lightweight &
basically bulletproof. Perihelion tech support is excellent. (I have
modified the suggested external circuitry somewhat for my needs.) Highly
recommended.
Of course, most modern EFIS's will also give low voltage alarms, with
adjustable trigger points. Mine is set to warn at 13.1 V, as a redundant,
earlier warning.
Perihelion also sells a simple, easy to install low voltage warning light
(only) that trips at 13.0V, for $39. (See http://tinyurl.com/yj7g5jh) If
anybody wants one of those, I believe I have an extra one I'll sell for
less.
...
...I have seen a few AGM (odysey type Absorbed Glass Mat) batteries fail
but they all had been fully discharged for some reason and they could
not be recharged. Their other annoying feature is that they don't
tolerate over charging well and have a short life if the charging
voltage is high.
As Ken suggests, with AGM batteries it's important to use the correct
charger. It is not enough that a charger is described as "automatic" or
"multi-stage" or "will not overcharge", etc., because correct charging rates
and transitions between charge rates, are also important. Bob Nuckolls has
tested several chargers and written on this subject as well.
Ron
254R
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