boB and Jarmo, thanks for great explanations.......So, let's dump that
idea and go back to square one: a programmable 1.5kW charger for 12 volt
batteries. I have been checking with all the charger manufacturers I can
find and no one makes this product. Argus said no, Pro Charging said no,
a few others, no.
Brian, an inverter/charger and remote will work great but that still
represents $1000 cost and about $1350 to my customer for a 100 amp
charger. But, so far, this is my only option.
A few years ago Magnum Energy told me they were working on a stand alone
programmable charger but nothing yet. It probably does not cost much
less to build than the inverter/charger does.
Thanks to all for the answers.
Thank you,
Larry
On 12/16/14 2:19 PM, b...@midnitesolar.com wrote:
Jarmo, you are absolutely correct. This is another great reason NOT
to use an MPPT charge controller
as an AC sourced battery charger. Also, if my instructions are not
followed to a TEE, the CC WILL blow up !
The input capacitors are going to wear out MUCH sooner than a real
charger because of the 60Hz or 120
Hz ripple shown in Jarmo's graph. Capacitor ripple abuse was one
answer to one of Larry's questions about long term
reliability.
Also, if the input diodes short, you are applying AC directly to the
input capacitors and
will go POOF as well as the power section.
And you would NOT know that you needed an input power resistor first
or possibly where
to even find one of the correct resistor values and power ratings if
the input source is stiff.
This is the scariest problem in my mind.... Too high of input max
power voltage, overcurrent
and then, battery voltage regulation will overshoot without that resistor.
I would just spend the extra money and do this right in the first
place and don't try to
cut corners on price.
Brian Teitelbaum had the best idea I think... Just buy an inverter
with a power factor corrected
charger like the newer Schneider SW inverter/charger (I think that was
the one ?) or one of
the MSW Magnums. Or, a decent charger if one exists. Haven't seen
the Argus/Alpha one.
MPPT charge controllers are really just NOT designed for this.
(although they might work for a while).
In fact, Ryan from MidNite Solar blew up several Classics at first.
But knowing that some folks are going to try this, I thought it best
to give at least some directions.
Thanks,
boB
On 12/16/2014 12:34 PM, jarmo.venalai...@schneider-electric.com wrote:
Hi:
I'm enjoying learning many new ways of looking at things and of
practical solutions on this forum. In that spirit, the only thing I
would add to this discussion is that the power factor as seen by the
AC source will be very poor. In that regard, the larger the caps,
the more stable the "DC" voltage, but the poorer the PF.
This will show up as much lower charging efficiency due to the way in
which AC current is drawn by the bridge rectifier/capacitor circuit.
Here's an actual graph of how a bridge rectifier connected to a
capacitor draws AC current,
The graph is from my past life a couple of decades ago back when I
was studying. It's not a conventional phase-shift PF problem, but
rather a form factor PF problem. It shows the current drawn by a 13"
PC monitor of that era, before PF correction was mandated for all new
products. In this example the 'crest factor', (peak current as
measured versus what it could have been if the current was drawn
throughout the AC pulses, was about 4x). Depending on the size of
capacitor, it can be as high as 7x.
The practical effect on the wires and devices including the diodes
and charge controller, is that a lot of heat is generated in their
power components. The source of the energy for that heat is the AC
source and in cases where the AC source is a generator that
translates to much higher fuel consumption, (in some cases over 30%
more).
Out of my tests back then, I also discovered one practical
recommendation.
If you are using bridge rectifiers connected to capacitors, do not
have any length of wire and in particular no loop area in the wires
between the bridge rectifier and capacitors. Having wire/loop area
introduces inductance into the circuit which behaves somewhat like an
ignition coil due to the high speed reverse recovery period of the
diodes; and this happens four times every AC cycle. Given the right
conditions the voltage spikes caused by that inductance/ignition coil
like effect will make short work of the diodes and other components
which are on the circuit.
The voltage spikes wont be a problem if the bridge rectifier is as
close as possible to the capacitors, but due to reverse recovery
effect, you'll still be stressing the parts and heating wires.
In my opinion, its ok to do this, but I wouldn't push power levels to
anywhere near the limits of components and devices.
JARMO
_____________________________________________________________________________________
*
Jarmo Venalainen* | *Schneider Electric ** | Solar Business* |
*CANADA* | *Training & Development Specialist - Senior* *
Phone:* +604-422-2528 | *Fax:* +604-420-1591 | *Mobile:*
+604-505-0291 *
Email:* _jarmo.venalainen@schneider-electric.com_
<mailto:jarmo.venalai...@schneider-electric.com> |
*Site:*_www.SEsolar.com_ <http://www.sesolar.com/> | *Address:* 3700
Gilmore Way, Burnaby, BC V5G4M1
------------------------------------------------------------------------
Larry, Pitfalls ?
The biggest pitfall I would say is if you have a VERY stiff grid.
If your Voc is say, 170V DC and the CC current limits it output at
say, 169 V DC,
they you are going to need to add an input power resistor of a couple
Ohms to
help cushion the input to be more like a PV module. A lot of times,
the grid is
not nearly this bad, especially generators.
Also, If you are going to do this, I would NOT use Solar mode but
instead try
Hydro mode set to Manual MPP voltage. First start the MPPV at
something just
less than Voc or maybe, say, 160 VDC. Then, from main STATUS screen,
you can
adjust the input voltage up and down by pressing the Soft-Right or
Soft-Left
keys respectfully. (upper right and upper left keys). Then you can
manually get
a feel for what it should be set for.
The Classic 200 is the only CC of ours that I would use. The 250
would work but the
200 is much more suited. I wish there were a real charger that one
could buy that was
isolated, and we have never really advocated MPPT charge controllers
for this but
in a pinch, they always seem to work find. Never did add a "DT" mode
(after Daryl
Thayer of course), but this hydro mode seems to work OK.
If you want to let it sweep but setting it to 3 minutes (or higher)
that will also work.
If you do that, set the minimum input voltage. Something like 140V
or so will keep
it from dropping the input voltage too low and either bogging down
the input source
and the rectifier bridge (especially generators)
You can also set the INPUT current limit in the LIMITS menu. This
was for hydro
in particular. Either limit can help reduce Isc or bogging down issues.
The other pitfall is that it is NOT galvanically isolated so you
should be very careful.
We use an X240 equivalent transformer to keep the batteries going in
our burn in
rack using 2 Classic 200s and it works great.
Also, use a nice and strong full bridge rectifier so that it applies
120 Hz instead of
60 Hz to the input. That is much easier on the input capacitors and
things and just
makes it work smoother. There are input capacitors (filtering) on
most charge controllers.
Again, in a pinch this seems to work but watch that input max power
point voltage to make
sure it is not too high compared to the Voc. If there isn't enough
voltage spacing between
the two (stiff AC source) then the control isn't going to be very
smooth and might risk
letting the smoke out.
What ever you do here, be very careful what you touch !
boB
This has been discussed on this list in years past. It is possible to
use an outback charge controller as a battery charger. You need to
put the 120 AC into a bridge rectifier, then feed the 120 DC into the
controller’s PV input. So you’ll have an 80 amp battery charger.
On Dec 15, 2014 4:01 PM, "Larry" <_larry@starlightsolar.com_
<mailto:la...@starlightsolar.com>> wrote:
Wrenches,
Does anyone know of a 120/12 volt battery charger that can be
programmed for absorb and float voltage and time in absorb mode? I
have been needing this product for many years but I can only find it
in inverters with built in chargers from Magnum, Outback, and Xantrex.
--
Thank you,
Larry Crutcher
Starlight Solar Power Systems
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