[RE-wrenches] Programmable Battery Charger

Wed Dec 17 06:45:32 PST 2014

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, boB at 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.Venalainen at 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 at schneider-electric.com_ 
>> <mailto:jarmo.venalainen at 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 at starlightsolar.com_ 
>> <mailto:larry at 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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