Battery Chargers

[Mike Rapoport]

I have recently converted from NiCad to lead acid batteries which are supped
to have a life of 2-3 yrs. The batteries cost about $1500 for the pair and
I am interested in maximizing their life the extent practical. I have heard
about "pulse chargers" that reportedly reduce sulfate on the battery plates.
Would using one of these make a meaningful difference in battery life? I
plan to connect the charger through the external power recepticle. Any
thoughts/ideas/sources?

I am also interested in a larger source of DC power so that I can use the
cabin lights and have things turned on while cleaning/troubleshooting ect.
Again I plan to connect through the external power recepticle. I ahve 120V
and 240V availible. I am not looking to spend $000s on a GPU type cart.

Thanks for any input!

Mike
MU-2

[JDupre5762]

>I am also interested in a larger source of DC power so that I can use the
>cabin lights and have things turned on while cleaning/troubleshooting ect.

Why not make a battery cart with large truck or tractor batteries? I have used
several of those over the years most home made. One even used a marine rotary
switch that when wired correctly allowed the user to select either 12 or 24
volts. That one used just two batteries mounted on a welding bottle cart. It
also had a battery charger permanently mounted and connected. When not in use
we kept it plugged in.

John Dupre'

[mikem]

Mike,

Here is something I recently wrote on this topic on the SWPC email list:

> From: "Adolph . . ."
>
> As I looked at the latest Popular Mechanics, there was an ad for
> a company that makes a "smart" battery charger. One claim is
>
> "Reconditions sulfted batteries using electronic pulse technology that
> reverses sulfate buld-up on battery plates, improving charge-carrying
> capability."

Will it "float" a lead acid battery and keep it from
self-discharging? Yes.

Will it recharge a run down battery that just needs to
recharged? Yes, if you are willing to wait long enough.
A 10A Sears model will do it a lot faster and cheaper

Will it substantially increase the AH capacity of an old battery
which has already lost capacity? No.

> Not that I'm in the market for a charger, but if it can do that, it would
> be a significant improvement. Anyone have one, or know anything about
> these?

I built a computer-controlled battery charger/discharger which
acurately measures the AH capacity of batteries. The device is
used routinely by my AP/IA to evaluate aircraft batteries for
continuing airworthiness.

I researched the "pulse charging" desulphating techniques, read
the patents, built a prototype, and did some carefully
controlled experiments where I measured the before and after
Amp-Hour capacity of some flooded cell SLA, automotive, marine,
and aircraft batteries.

I found no improvement in AH capacity that lasted. There was no
difference in the capacity of the battery if it was charged with
pure DC, or with "pulses"!!!

That said, can a case be made for sophisticated chargers which
have several operating modes? Certainly. A good example of what
is out there is at

http://batterytender.com/technical.php

(I have no connection with them, but they explain the
fundamentals well). Read "battery charging basics".

IMHO, the "pulse charging" stuff is snake oil...

MikeM (PhD EE)
Pacer '00Z
Skylane '1MM

Mike Rapoport wrote:
> I have recently converted from NiCad to lead acid batteries which are supped
> to have a life of 2-3 yrs. The batteries cost about $1500 for the pair and
> I am interested in maximizing their life the extent practical. I have heard
> about "pulse chargers" that reportedly reduce sulfate on the battery plates.
> Would using one of these make a meaningful difference in battery life? I
> plan to connect the charger through the external power recepticle. Any
> thoughts/ideas/sources?
>
> I am also interested in a larger source of DC power so that I can use the
> cabin lights and have things turned on while cleaning/troubleshooting ect.
> Again I plan to connect through the external power recepticle. I ahve 120V
> and 240V availible. I am not looking to spend $000s on a GPU type cart.
>
> Thanks for any input!
>
> Mike
> MU-2
>
>

[mikem]

Here is yet another (I hope) relevant posting from the other list:

Subject: Re: Battery Chargers

> What charger, amp size, etc., would you recommend to slightly
> charge or maintain a std lead acid 35 series aircraft battery?

By "maintain", I assume you are concerned about what happens to
the typical G35 aircraft battery during times when the aircraft
is not flown regularly (say bi-weekly).

The answer is complicated. As long as the aircraft is flown
once every couple of weeks, assuming that the generating
capacity in the aircraft exceeds the current being drawn by the
instruments, avionics and lights, (so that the reserve capacity
is available for charging the battery), and that the voltage
regulator gets the battery voltage up to 14.2+ Volts for the
duration of a flight, then you dont need to do anything
involving external chargers.

If the aircraft generation capacity or regulation is suspect,
then instead of tinkering with chargers, you really should fix
the root cause (which is install enough generating capacity,
adjust the voltage regulator to produce said 14.2+ V, fly the
airplane an hour or two every two weeks, etc.)

The reason for the "every two weeks" statements above are based
on the physics of flooded-cell batteries. There are two parts to
prevent degradation of a battery which is sitting unused for
periods of weeks to months. Lets call this "battery
maintenance". Note that "maintenence" only needs to be done when
the aircraft is not regularly flown, as in the winter months.

First, you need to keep the battery from discharging itself even
after disconnecting anything that draws current, which should be
the case if you turn off your Master. Second, you need to
periodically stir the acid in battery to prevent the acid from
stratifying with the lowest specific gravity on top.

All lead acid batteries loose charge just by sitting around. at
100 deg F, a G35 will loose 10%-20% of its capacity per month.
In cold weather, the self discharge rate is much lower. So if
you want to maintain a battery near full capacity, you have to
replace the charge lost due to self discharge. It requires only
~ 0.25A to make up for the leakage.

Preventing self discharge is usually accomplished by "floating"
the battery using a voltage-limited charger, which puts out 13.5
+-0.1 V open-circuit. Most commercial automotive chargers such
as you would get at Sears or Checker are not voltage limited
accurately enough to leave them connected to a battery for more
than 24 hours!!! They are suitable for recharging a run-down
battery, but they must be manually disconnected after a few
hours.

The better models of the automotive chargers have a time clock
shutoff which means you dont have to drive back to the airport
to shut off the charger. If you have the disipline, you can
"maintain" an unused battery through the winter months by giving
it an 4-6 hour charge every 30 days or so, relying on the clock
in the charger to shut it off, otherwise you have to drive back
to airport to disconnect the charger.

One of the primary causes of loss of capacity of batteries is
sulfation of the lead plates; Sulfation happens when the battery
is allowed to sit around in a partially or totally discharged
state for long periods; sulfation is minimised by keeping the
Specific Gravity of the acid high (fully charged) see:

http://www.sierrasolar.com/design/b_leadbattery.htm

The acid in a stationary battery (not being sloshed around in a
car, boat, motorhome, airplane) will stratify, meaning that the
Specific gravity at the top of the battery will be much less
that at the bottom. Due to low SG at the top, the top parts of
the plates will sulfate first, reducing the capacity and cold
cranking amperage of the battery.

The solution to stratification is to mechanically stir the acid,
which happens normally if you take your battery for a ride in
the car, or for a flight in the airplane. However, if the
airplane/car is parked for six months, what then?

A good substitute for mechanical agitation is to periodically
(once every two weeks or so) connect the battery to a charger
whose voltage is set to 14.4+ V for a few hours. In the industry
this is sometimes called "equalization", but the primary benefit
comes from charging the battery hard enough to evolve gas
(hydrogen at one plate, oxygen at the other). The bubbles rise
through the acid, stirring it as they go, mixing the weaker acid
with the stronger.

So, for total automatic unattended maintenance of batteries, the
charger has to float at 13.5V continuously, and every two weeks
or so, it needs to bump up the voltage to about 14.4V while
delivering a few amps for a few hours, and then revert back to
the float mode. If the aircraft is flown regularly, then you
dont have to bother with equalization.

> Is it feasible to leave the master switch "on" to activate the
> solenoid and charge/maintain the battery thru the cigar
> lighter circuit?
> Do you think this might create any unforeseen
> problems such as overheating the solenoid if left unattended
> for several days at a time etc. Or is this just a plain bad
> idea?

Its just a bad idea. Overheating of the solenoid shouldn't be a
problem, because the solenoid is rated for it. However, your
charger has to deliver approximately 1.5A to the coil in the
solenoid, plus whatever unswitched loads there are in the aircraft (like
the fuel gauges)

Suppose someone unplugs your charger? Now the solenoid/gauges
will kill your battery. Its not hard to wire in a fused
connector which will allow direct access to the battery with the
master off.

>Is it possible to overcharge a battery with today's low
> amp chargers?

Yes.

You have to buy a charger specifically made for "float
charging", like the BatteryTender

http://www.batterytender.com/

If in doubt, connect your charger to a battery for 6 to 12
hours. Use an accurate digital voltmeter to measure the voltage
between the battery terminals with the charger still charging.
If the measured battery voltage after a few hours exceeds 13.6V,
the charger is not suitable for long term float charging.

In summary, if all you own is the typical Sears 10A charger with
the time clock, then while the aircraft/motor home/boat is not
being used, hook the charger to the battery with the time clock
set to 6 hours. Go back and do it each month. That is the best
you can do to prevent the battery from loosing capacity while
inactive. During the six hours, the charger will put back the
self discharge, and then it will bubble the battery just enough
to stir the acid. This regemin is way better than just letting
the battery sit idle for six months.

MikeM (Batteries r us)
Pacer '00Z
Skylane '1MM

[Mike Rapoport]

Thanks that is a great idea.

Mike
MU-2


"JDupre5762" > wrote in message
...
> >I am also interested in a larger source of DC power so that I can use the
> >cabin lights and have things turned on while cleaning/troubleshooting
ect.
>
> Why not make a battery cart with large truck or tractor batteries? I have
used
> several of those over the years most home made. One even used a marine
rotary
> switch that when wired correctly allowed the user to select either 12 or
24
> volts. That one used just two batteries mounted on a welding bottle cart.
It
> also had a battery charger permanently mounted and connected. When not in
use
> we kept it plugged in.
>
> John Dupre'

[Mike Rapoport]

Thanks, it will be a lot easier to choose a charger without considering the
pulse types.

Mike
MU-2


"mikem" > wrote in message
...
> Mike,
>
> Here is something I recently wrote on this topic on the SWPC email list:
>
> > From: "Adolph . . ."
> >
> > As I looked at the latest Popular Mechanics, there was an ad for
> > a company that makes a "smart" battery charger. One claim is
> >
> > "Reconditions sulfted batteries using electronic pulse technology that
> > reverses sulfate buld-up on battery plates, improving charge-carrying
> > capability."
>
> Will it "float" a lead acid battery and keep it from
> self-discharging? Yes.
>
> Will it recharge a run down battery that just needs to
> recharged? Yes, if you are willing to wait long enough.
> A 10A Sears model will do it a lot faster and cheaper
>
> Will it substantially increase the AH capacity of an old battery
> which has already lost capacity? No.
>
> > Not that I'm in the market for a charger, but if it can do that, it
would
> > be a significant improvement. Anyone have one, or know anything about
> > these?
>
> I built a computer-controlled battery charger/discharger which
> acurately measures the AH capacity of batteries. The device is
> used routinely by my AP/IA to evaluate aircraft batteries for
> continuing airworthiness.
>
> I researched the "pulse charging" desulphating techniques, read
> the patents, built a prototype, and did some carefully
> controlled experiments where I measured the before and after
> Amp-Hour capacity of some flooded cell SLA, automotive, marine,
> and aircraft batteries.
>
> I found no improvement in AH capacity that lasted. There was no
> difference in the capacity of the battery if it was charged with
> pure DC, or with "pulses"!!!
>
> That said, can a case be made for sophisticated chargers which
> have several operating modes? Certainly. A good example of what
> is out there is at
>
> http://batterytender.com/technical.php
>
> (I have no connection with them, but they explain the
> fundamentals well). Read "battery charging basics".
>
> IMHO, the "pulse charging" stuff is snake oil...
>
> MikeM (PhD EE)
> Pacer '00Z
> Skylane '1MM
>
> Mike Rapoport wrote:
> > I have recently converted from NiCad to lead acid batteries which are
supped
> > to have a life of 2-3 yrs. The batteries cost about $1500 for the pair
and
> > I am interested in maximizing their life the extent practical. I have
heard
> > about "pulse chargers" that reportedly reduce sulfate on the battery
plates.
> > Would using one of these make a meaningful difference in battery life?
I
> > plan to connect the charger through the external power recepticle. Any
> > thoughts/ideas/sources?
> >
> > I am also interested in a larger source of DC power so that I can use
the
> > cabin lights and have things turned on while cleaning/troubleshooting
ect.
> > Again I plan to connect through the external power recepticle. I ahve
120V
> > and 240V availible. I am not looking to spend $000s on a GPU type cart.
> >
> > Thanks for any input!
> >
> > Mike
> > MU-2
> >
> >
>

[Paul Sengupta]

Jim Weir had a design to bring sulphated batteries back to life.

I would guess that you don't need to do it if the battery is ok in
the first place.

I've got a 300mA 13.5V top-up thing I bought, just a constant
trickle charge, and I've actually found that I've brought a couple
of "dead" batteries back to serviceable condition by leaving that
on for a couple of weeks (car batteries).

Paulu

"Mike Rapoport" > wrote in message
ink.net...
> I have heard
> about "pulse chargers" that reportedly reduce sulfate on the battery
plates.
> Would using one of these make a meaningful difference in battery life?

[Paul Sengupta]

http://www.rst-engr.com/kitplanes/KP0204/KP0204.htm

I read it in Kitplanes.

"Paul Sengupta" > wrote in message
...
> Jim Weir had a design to bring sulphated batteries back to life.

[Jim Weir]

"Paul Sengupta" >
shared these priceless pearls of wisdom:

->http://www.rst-engr.com/kitplanes/KP0204/KP0204.htm
->
->I read it in Kitplanes.

So of course it HAS to be true.

{;-)


Jim



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Ron Rosenfeld]

On Thu, 20 Nov 2003 21:05:24 GMT, "Mike Rapoport"
> wrote:

>I have recently converted from NiCad to lead acid batteries which are supped
>to have a life of 2-3 yrs. The batteries cost about $1500 for the pair and
>I am interested in maximizing their life the extent practical. I have heard
>about "pulse chargers" that reportedly reduce sulfate on the battery plates.
>Would using one of these make a meaningful difference in battery life? I
>plan to connect the charger through the external power recepticle. Any
>thoughts/ideas/sources?
>
>I am also interested in a larger source of DC power so that I can use the
>cabin lights and have things turned on while cleaning/troubleshooting ect.
>Again I plan to connect through the external power recepticle. I ahve 120V
>and 240V availible. I am not looking to spend $000s on a GPU type cart.
>
>Thanks for any input!
>
>Mike
>MU-2
>

I read this and thought I was on the Homepower NG <g>.

I don't know how well the pulse chargers will work on starting type
batteries. They are helpful for deep discharge cells, though.

For the type of battery you have, they are designed for starting. They can
produce a large amount of current for a short period of time. However,
they are NOT designed to be deep discharged. So you should take care not
to discharge them to any lower than about 20%. In other words, they should
always retain at least 80% of their full state of charge, and be maintained
at full charge as often as practical -- certainly at least every two weeks.

If you are going to run cabin lights and other appliances for any length of
time, you really should be using deep discharge batteries. These can
tolerate repeated 80% depth of discharge (DOD). Depending on your power
requirements (which can be calculated), you may be able to use second hand
fork lift or golf cart batteries. These are available inexpensively
through Sam's and other discount places, as well as at battery dealers.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[Stu Gotts]

Paul;

I picked up a couple of those little trickle chargers from Harbor
Freight. You need to watch the catalogs, as the price varies from
$8.99 to $14.99 for the same thing!!! These are a must have for those
gas recombant (sp?) batteries everyone things are so good.

The batteries may have come up in voltage, but were they able to take
a load and bounce back in a reasonable amount of time?



On Fri, 28 Nov 2003 13:30:02 -0000, "Paul Sengupta"
> wrote:

>Jim Weir had a design to bring sulphated batteries back to life.
>
>I would guess that you don't need to do it if the battery is ok in
>the first place.
>
>I've got a 300mA 13.5V top-up thing I bought, just a constant
>trickle charge, and I've actually found that I've brought a couple
>of "dead" batteries back to serviceable condition by leaving that
>on for a couple of weeks (car batteries).
>
>Paulu
>
>"Mike Rapoport" > wrote in message
ink.net...
>> I have heard
>> about "pulse chargers" that reportedly reduce sulfate on the battery
>plates.
>> Would using one of these make a meaningful difference in battery life?
>

[Paul Sengupta]

Yes, absolutely, that was my measure. One of my cars
has an electrical fault which runs down the battery in a
few days, so it's a good test! :-) Haven't had time to
track down the fault yet.

Another I let run on empty for a while as I was abroad
for a few months a couple of years ago. I thought I was
going to be back so I didn't disconnect the battery. They
stopped the flights home! So. I came back four months
later to a completely dead battery. Normal charging did
nothing, it wouldn't keep a charge. I bought a new battery
and put the old one on trickle charge for a few weeks (!)
after which it was as good as the new one.

Paul

"Stu Gotts" > wrote in message
...
> The batteries may have come up in voltage, but were they able to take
> a load and bounce back in a reasonable amount of time?