[AT] Battery Chargers

[Ralph Goff]

This was interesting reading. Some batteries do stand a lot of abuse and
still keep coming back for more.
 I have had a truck battery completely discharged (dome light
stayed on), and the battery was partially frozen as a result. After thawing
and a slow re-charging at 2 to 4 amps that battery went on to serve a long
and useful life in the truck.
Recently I had another mysterious battery rundown on the 970 Case. It had
sat out through some rainy weather and when I went to start it the batteries
were absolutely dead, not even a flicker from the lights. Turns out that the
cab fan that had not worked for years suddenly began working while the
tractor sat out in the rain for several days and this killed both 12 volt
batteries.. I discovered this when I connected the booster cables and heard
the fan start up.
I was able to start it with booster cables off the other tractor and drive
the 970 to the yard where it received a few hours of re-charging off the
small 6 amp charger. A month later the batteries seem to be working fine.
Unfortunately, the cab fan has once again gone into dormancy. Temp is
supposed to hit 80 today.
Ralph in Sask.
http://lgoff.sasktelwebsite.net/

----- Original Message -----
From: Matthew <matthewx at dogod.com>
To: <at at lists.antique-tractor.com>
Sent: Sunday, June 27, 2004 7:50 PM
Subject: RE: [AT] Battery Chargers


> This is from another list, but has a lot of good info on charging
> battries.  This info is from John, credit att he bottom.
>
> --Matthew
>
>
>
>
> Batteries - one of my areas of expertise.  I putz around with EVs and with
> my motorhome.
>
> About the deep discharge batteries.  You will kill conventional wet cell
> deep cycle batteries in just a few, perhaps less than 10, complete
discharges.
> Wound electrode AGMs (Orbitals, exides) fare a little better but not much.
> Hawker's pure lead electrode AGMs can take it but they're expensive and
the
> largest is only about 60 ah.
>
> I once had a set of motorhome batteries killed with ONE full discharge.
Some
> vandals unplugged my MH while it was parked and the batteries fully (0
volts)
> discharged before I found it.  Using standard rescue techniques (high
voltage,
> desulfator pulser, reverse charging, EDTA in the electrolyte, etc) I
managed
> to get them to accept charge but the capacity never rose to more than
about
> 30% of their ratings.  I replaced them immediately but took them to my lab
> to see just how much I could recover a completely killed battery.  Answer:
not
> much.
>
> With a conventional wet cell battery, you never want to pull it below
about
> 80% depth of discharge or about 10.75 volts.  80% DOD will give you
perhaps
> 400 cycles.  The cycle life vs DOD goes down FAST below 80%.
>
> You can use your vehicle's generator or alternator to partially charge the
> battery but it won't work very well.  A car's system is in effect, a
trickle
> charger.  The voltage is too low to fully or rapidly charge the battery.
> The car system will fairly quickly restore up to about 50% charge IFF the
> interconnect wire is heavy enough, the alternator voltage is high enough
> (14.0 at least) and you use an interconnect relay (looks like a starter
relay
> but with a continuous duty coil) instead of that battery isolator thing.
> Problem is, chronically undercharging the battery will kill it only a
little
> slower than fully discharging it.
>
> The correct way to charge the battery is the three stage method.  This is
as
> follows:
>
> Bulk -  This stage converts the bulk of the active material on the plates.
> It represents a state of charge from wherever to about 70 to 80% charge,
> depending on the exact chemistry and plate construction.  This is
accomplished
> with a constant current charge of up to about C (C is the amp-hour
capacity)
> amps.  This phase ends when the terminal voltage reaches about 14.75 volts
> on a wet cell battery.
>
> Absorption - this stage converts the deeper active materials in the
plates.
> It takes time for the acid to diffuse out of the plates so this takes more
> time.  This is a constant voltage charge regime, 14.75 volts normally.
This
> stage represents the state of charge from wherever bulk ends up to about
> 90%.
>
> This stage ends somewhat arbitrarily when the current drops to about 2% of
> the constant current bulk charge value.  The current is dropping rapidly
at
> that point so anything in the 1-10% range works fine.
>
> Float - This stage puts the last bit in.  It is done at a constant 13.9-14
> volts or thereabouts.  This is usually a timed stage and lasts a couple of
> hours.  At some point during this stage the battery becomes fully charged
> and gases.
>
> At that point the charger is either removed or turned down to the
> maintenance/trickle voltage of 13.7 or pulse maintenance.  The preferable
> maintenance is a pulse algorithm where there is no charge current until
the
> voltage drops to about 13.5 or 13.6.  At that point, a low current charge
is
> supplied until the voltage rises to around 14 volts.  Typically the ~5 amp
> pulse will last 5 seconds, repeating every few minutes.
>
> You can operate for a few cycles in the bulk charge range.  That is,
charge
> the battery to the end of the bulk stage (in an hour or less if your
charger
> can output C amps), then discharge to 20% charge.  Every 4 or 5 cycles the
> battery needs the complete cycle to prevent hardening of the sulfate
> crystals
> on the plates which is what ultimately kills the battery.
>
> The above voltages vary with temperature (about 0.1v/10dC for wet cells)
and
> are approximately correct for 70 deg F.  The best chargers are temperature
> compensated.
>
> I do this when dry camping (no hookups to shore power) in my motorhome.  I
> designed and built an engine-driven "cordless battery charger" that is
> capable
> of 150 amp output.  Not quite 1C for my 220 amp-hour battery pack but
close
> enough.  I can go for several days of 60 to 80% DOD with just an hour a
> day's
> charging.  My CBC has a smart digital controller I designed that does the
> full
> multi-stage routine as described above.  It is temperature compensated via
a
> sensor that clips to a battery post.  Here's are some photos of a very
early
> prototype using a commercially available analog 3-stage charge controller.
> It
> is significantly different now but I haven't gotten around to making new
> photos.
>
> http://bellsouthpwp.net/j/o/johngd/files/rv/cordless_battery_charger/
>
> I don't know of any commercially available cordless chargers but there are
> some line and vehicle engine operated ones.  These are all very expensive
> but
> I'll mention them anyway.
>
> This company:
>
> http://www.amplepower.com/
>
> Makes a very nice line of 3 stage regulators that will turn the vehicle
> alternator into a 3 stage charger.  This is normally used on a boat that
is
> equipped with two batteries.  One battery supplies the boat while the
other
> is
> charged.  This is necessary because the near-15 volts at the end of bulk
> charging is hard on 12 volt stuff like lamps.  It is also used on
> motorhomes.
> Typically the motorhome will have two alternators, one for the chassis
> (regulated conventionally) and one to charge the house batteries,
controlled
> by this type of regulator.  I plan to go this route on my MH when I get
> around
> to fabricating the necessary brackets to mount a second alternator.  This
> will
> mostly, if not completely replace the CBC.
>
> Xantrex.com (formerly Cruising Equipment Company) makes an analog version.
> That is what is pictured in my photos.  It works but is inferior to the
> Ample
> Power unit because it is analog and relies on fixed timers to end the
> absorption and float stages instead of actually measuring the battery
> condition.  It's a LOT cheaper though.
>
> Xantrex, IOTA, Progressive Dynamics and a few other companies make 3 stage
> charger/converters designed for RVs.  They're designed to be built-in and
> are
> expensive.
>
> Fortunately there is exactly one company that makes an affordable,
portable
> 3
> stage charger.  This is the Vector VEC1093 40 amp charger.  Here it is on
> Amazon:
>
>
http://www.amazon.com/exec/obidos/tg/detail/-/B00009RB0T/qid=1088231265/sr=8
> -2/ref=sr_8_xs_ap_i2_xgl60/103-2822418-6348618?v=glance&s=home-garden&n=50
78
> 46
> http://tinyurl.com/3h33t
>
> I have one of these and wrote a very extensive review of it for
> rec.outdoors.rv-travel a couple of months ago.  When I looked around to
buy
> one, every price I found on the net was 109.99 so I bought it from Amazon.
> Northern Tool stocks the 20 amp version in their stores but not the 40
amp.
>
> This charger does a textbook-perfect three stage charge, does pulse
> maintenance and includes a desulfator to help recover capacity in sulfated
> batteries.  Only two things I don't like about it.  It's too big (that
whole
> pod on the bottom serves only to contain an EMI filter) and the clips are
> flimsy.
>
> Here are some photos and data that accompanied my test report on RORT:
>
> http://bellsouthpwp.net/j/o/johngd/files/rv/Vector%20battery%20charger/
>
> In particular,
>
>
http://bellsouthpwp.net/j/o/johngd/files/rv/Vector%20battery%20charger/First
> %20test%20cycle.jpg
>
> Shows the charge cycle on a set of 220 ah golf cart batteries.  I recorded
> the
> AC INPUT amps to the charger because I didn't have a DC amps stripchart
> recorder handy.  The input current rises during the bulk charge stage
> because
> at a constant output current and constant input line voltage, it takes
more
> input amps as the output voltage rises.
>
> This pair of 6 volt batteries in series has about twice the capacity of a
> single 12 volt deep cycle battery.  The bulk stage took about 4 hours here
> so
> it would take about half that (2 hours) for a single battery.
>
> You can use this charger two ways.  You could plug it in at night when you
> park the van.  Or you could install a suitable 120vac inverter in your van
> and
> plug the charger into that.  Sounds kludgy but it actually works quite
well.
>
> I have a 1000 watt inverter in my MH (Costco, $79) that powers my electric
> refrigerator and my microwave when I'm dry camping and don't want to crank
> the
> main generator.  It also powers the Vector quite nicely.
>
> When I take long travel (as opposed to camping) trips in my MH, moving to
a
> new place every night or two, I use this lashup to charge my house
batteries
> (225 ah) while I'm driving.  I simply open the battery interconnect relay,
> flip the inverter over to the engine alternator system and let the Vector
do
> the charging.
>
> That taken care of, let's look at the neon side.  Every 12 volt supply
I've
> tried (I like the Tech-22 ones the best) has a low voltage cutoff.  The
> problem is, this doesn't work like you'd think it would because of the
> battery's characteristics.
>
> When the voltage drops to the trip point, the supply turns off.  With the
> load
> removed from the battery, the voltage recovers until the supply comes back
> on
> again.  In a few seconds, the voltage drops, the neon supply trips and the
> cycle repeats.  You end up with an annoyingly flashing sign.  Now you may
> WANT
> flashing but this will be irregular and ragged.  Not attractive.
>
> What is required is a latching undervoltage relay that will break the
> connection on the first trip.  Such relays are available commercially but
> are
> expensive.  There is one in this picture:
>
>
http://bellsouthpwp.net/j/o/johngd/files/rv/Vector%20battery%20charger/First
> %20test%20cycle.jpg
>
> of my battery discharge tester.
>
> I make a simple relay for my own use.  I take a conventional relay like
the
> one in the center of that photo and cut away the coil.  An Exacto knife
> makes
> quick work of it.  I then wind sufficient turns of heavier wire around the
> armature so that the relay will pull in when the coil is hooked in series
> with
> the neon driver.  In other words, I convert the voltage operated relay to
a
> current operated one.  This is simple and easy, requiring less than 50
> turns.
>
> I connect the relay's normally open contacts in series with the coil and
in
> series with the neon supply.  I hook a momentary contact, normally open
> pushbutton in parallel with the relay contacts.  (or just drill a hole in
> the
> case so I can manually push in the contacts.)
>
> To turn the unit on, simply press the button.  That starts current
flowing.
> The current causes the relay to pick up, closing the relay contacts and
> sealing it in even after the button is released.  When the neon supply
trips
> off the first time from undervoltage, the relay opens, removing all power
> from
> the supply.  No cycling possible.
>
> One thing that makes the TECH-22 supply stand out from the crowd is the
> quality of his dimming.  It dims smoothly right down to zero with no
> flickering.  He pulse width modulates the full high voltage instead of
> reducing the voltage.  The is the reason for no flickering and the
> smoothness.
>
> If you decide to dim (recommended to extend battery life), you have to
take
> that into account when you're winding the latching relay.  The current
drawn
> by the supply drops linearly with dimming.  A lot of dimming requires more
> turns on the relay.
>
> Hmmm, looks like I wrote another book.... Time to go to bed :-)
>
> John
> ---
> John De Armond
> johngdDONTYOUDARE at bellsouth.net
> http://bellsouthpwp.net/j/o/johngd/
> Cleveland, Occupied TN
>
>
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