Glider Batteries and Chargers

On Aug 24, 7:08*pm, brianDG303 wrote:
More about Glider Batteries:

My club's gliders use Gel batteries, probably because they fit the
mounts so well, but mostly the private gliders use a battery type with
many names, I guess it's an SLA (Sealed Lead Acid) except it's not
really sealed. I started to call it an AGM (Acid Glass Matt) which it
has, but suddenly it started to be called a VRLA (Valve Regulated Lead
Acid). Anyway they are very interestingly made. Although they look
sealed many of these have a separate and tightly fitting top which is
glued on only at the short sides, (the Valve Regulated gas being
allowed to escape through the unglued long sides) and this cap can be
pulled off pretty easily exposing the sub-assembly consisting of small
recessed nipples rising from the center of little 'moats' that have a
fabric packing in them, I guess to absorb any acid that gets out of
the valve. Each of these little nipples has a rubber cap which forms a
one way valve. Pictures of this can be found he

http://picasaweb.google.com/BrianDG3...laneBatteries#

As far as I can tell the battery exhausts gas (and/or liquid) whenever
the internal pressure rises very much beyond the ambient, but seals
tightly when the internal pressure is lower than ambient. When the top
is removed the caps are dished down into the nipple from negative
pressure and when you pull the cap off there is a considerable hiss of
air flow into the battery. So, although they are valve regulated I
don't think they 'breathe' much, at least not in.

Also in that group of photos is a housing I've made, different from
but based on an example I saw Darryl Ramm make, that forms a handle,
protects the battery terminals, holds a Klixon aircraft rated circuit
breaker and two Anderson Powerpole connector sets. Using clear Lexan
for the top is a trick from hospitals, they will sometimes make
electrical devices out of clear polycarbonate- you can inspect the
terminals that way and see a failure developing. Also makes it easier
to work on. Having two outputs is very useful as well.

Brian

SLA == VRLA == AGM it is all the same stuff.

But why use a TLA when you can use a LFLA :-)

Some VRLA batteries are also referred to technically as recombinant,
or valve regulated lead acid recombinant, or lead acid recombinant
batteries. All basically the same stuff.

Most situations where glider pilots are referring to "gell cell" they
turn out to be VRLA batteries.

There really is no benefit of the old gel cell technology (electrolyte
gelled with a silica powder) and some disadvantages, including
repeated deep cycling and rapid charging causing gas pockets in the
gel. VRLA construction tends to be a bit more robust against
misshandling - with the plates really solidly packed in a compressed
sandwich that gel cells, but both are pretty robust.

The neoprene valves that Brian describes hold a slight over pressure
of the battery and prevent gas escaping under normal charge
situations. The valves will vent if the battery gets hot and/or is
overcharged. This why its normally OK to operate a VRLA battery in any
orientation but just don't charge them when upside down or they can
blow out a few drops of acid with the venting gas (even if they have
absorber designed to catch that acid).

Darryl

"brianDG303" wrote in message
...
More about Glider Batteries:

My club's gliders use Gel batteries, probably because they fit the
mounts so well, but mostly the private gliders use a battery type with
many names, I guess it's an SLA (Sealed Lead Acid) except it's not
really sealed. I started to call it an AGM (Acid Glass Matt) which it
has, but suddenly it started to be called a VRLA (Valve Regulated Lead
Acid).

Perhaps I am calling what I use the wrong name.

What kind of battery is it, that is widely available form RC shops, 7 amp
hour, that does not care which side is mounted up, and has two male slide
terminals on it, side by side at one end of the battery?
--
Jim in NC

On Tue, 24 Aug 2010 18:35:48 -0700, Darryl Ramm wrote:

Its not "omitting" peak-detection, peak detection does not work with
lead-acid batteries and so is irrelevant.

That was a bad short-hand, menat to cover all chemistries.

Lead acid chargers will at
least use a constant current bulk mode, then hopefully a constant
voltage (or current limited constant voltage) absorption mode and then
maybe a float mode. Working out what many of these RC chargers do from
their marketing datasheets or manuals can be a challenge hard.

Fair comment - and as these things don't have a 'current on' lamp or show
the actual current supplied as opposed to the setting. Its quite possible
mine just shut off without me noticing.

Must see what the Vencon does next time I put an SLA on it.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On 8/24/2010 6:07 PM, Martin Gregorie wrote:
I would, however, take issue over there being many RC chargers without a
float mode. I've not yet seen a multi-chemistry charger that didn't have
some sort of float mode for all chemistries: its essential for Li-poly
and for high-rate charging of NiCd/NiMH and anyway these charger/cyclers
are all microprocessor based, so leaving it off is inexcusably cheap
design. Did you mean that some just omit peak detection for lead-acid
batteries?

The Multiplex LN5014 and it's clones do not have a float mode for
lead-acid (Pb in their terminology). The Multiplex manual states that
explicitly, saying it's not needed because their self-discharge rate is
so low. They are right about the self-discharge, and my LN5014
definitely shuts off when the current drops to 10% of the set charge
rate (no peak detection is used for lead-acid). It does have a trickle
charge for some of the other chemistries.

I have no idea if other chargers offer float mode for lead-acid; in any
case, float mode for lead-acid seems unnecessary for a charger powered
by a battery, as it's not really practical to leave it running for long
enough to make any difference. It's not a feature I'd bother to look for.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

"Martin Gregorie" wrote

The only place I've been happy to use untimed chargers is with low
capacity NiCds. My favoured approach there is to use a "1% charge rate",
i.e. charge at 0.01C, and leave the battery permanently on charge unless
I'm flying the model its installed in. NiCds are frequently used as low-
maintenance emergency batteries and these are invariably left on charge
at the 1% rate for years at a time so they like this treatment. Its
really convenient: put the model box back on its rack after a contest or
trimming session, open the lid, connect the charger and forget about it
until next time you go flying.

My strategy for RC NiCads is to charge them with peak charger after flying,
then hook them onto a power strip with all of the other factory chargers or
equivalent which is powered by a 7 day charger. I set it to come on for 2
hours, once per week.
--
Jim in NC

On Wed, 25 Aug 2010 00:03:09 -0400, Morgans wrote:

"Martin Gregorie" wrote

The only place I've been happy to use untimed chargers is with low
capacity NiCds. My favoured approach there is to use a "1% charge
rate", i.e. charge at 0.01C, and leave the battery permanently on
charge unless I'm flying the model its installed in. NiCds are
frequently used as low- maintenance emergency batteries and these are
invariably left on charge at the 1% rate for years at a time so they
like this treatment. Its really convenient: put the model box back on
its rack after a contest or trimming session, open the lid, connect the
charger and forget about it until next time you go flying.

My strategy for RC NiCads is to charge them with peak charger after
flying, then hook them onto a power strip with all of the other factory
chargers or equivalent which is powered by a 7 day charger. I set it to
come on for 2 hours, once per week.

I found a really simple circuit for building a fixed constant current
circuit plus 'current flowing' LED indicator from an LM358 dual opamp, an
output transistor, a reference Zener and about 4 resistors. I have a
small plastic box containing a row of these, one per model, and simply
run it off a big old 24v mains supply box I built years ago. The circuit
is in the SAMS 'IC OP-AMP Cookbook' but I don't know if thats still in
print.

This works very well indeed for 4 and 5 cell 50 mAh NiCd batteries. They
get fed 900 uA because the dethermaliser timers they drive are always on
(no switch, charging socket in the timer faceplate) and these draw 80-300
uA unless they're releasing the tailplane, when they pull 500mA for 15 mS.

I have one or two higher rate versions sculling round too for other jobs,
such as charging a connection-free 1/2A starter I built, which contains a
set of six NiCd C cells.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Aug 24, 6:49*pm, Darryl Ramm wrote:
On Aug 24, 7:03*am, Grider Pirate wrote:

VSLA? A123? Cycling chargers?? *I think this subject should have it's
own thread. *Unlike transponders, we almost all need them.

Some comments below, in general and picking up a few things in other
posts/threads and reposting some things I've said elsewhere recently.

Most "smart" chargers are really pretty dumb ...clip...

I would add to this informative long post that desulfating chargers
are very helpful in extending the life of, and restoring, lead-acid
batteries. (Google "battery desulfation" or read
http://www.chargingchargers.com/tuto...sulfation.html as
an example)

Schumacher makes 2 desulfating chargers, available in auto stores or
via Internet for about $75. I use their model WM-6000A on my stored
automobiles, and have used it to quickly resuscitate my 12-v gel-cell
glider batteries, as well as to restore 2 batteries to usable
condition this summer after leaving the master on in the trailer for a
week. (They were all but shorted out.)

VDC Electronics seems to have the broadest line of desulfating
chargers. ( http://www.batteryminders.com ) I use their Concorde-
specific charger with my Mooney, which is designed for that battery
and is temperature compensated.

Their desulfating BatteryMinder Plus model 12117 can be had on the web
for about $45 plus shipping, and will maintain up to 5 batteries. A
summary of their non-aviation-specific chargers is in pdf format at
http://www.rvupgrades.info/batterymindermanual.pdf

They also make a solar desulfating charger available with either a 5-
watt or 15-watt panel My glider has 2 electrical systems, and I
mounted 2 15-watt desulfating chargers on the trailer roof, which is
very nice. I only wish they would work by moonlight.