Feeding Midnite Classic with multiple car chargers

H2SO4_guyH2SO4_guy Solar Expert Posts: 213 ✭✭✭
Is there any merit in taking 9 car battery chargers of the 10 amp variety, wire them in series into a Midnite Classic, limit the input to 10 amps, and be able to charge a 12 volt battery bank at a higer amperage and control the voltages to what they need better than a typical car charger. I would stay below the Voc limit of the Midnite. Some questions arise as the output will look a bit different to the charge controller than panels would, so would that have any affect?

There are 3 Crown CR-185 in parallel for 555 AH @ 12 VDC @ 20 hr rate.. Crown suggests a 25 amp charge each, so 75 amps is the target charge rate. (C-7.4)

I have tried wiring 5 chargers in series into a Trace C-40 to charge a 48 volt system, but probably due to the PWM circuit the amp meters on the chargers went from 0 to max back and forth. There was no way to limit the current either so I suspect it made the chargers overheat also.

I am trying to get by on the cheap using junk batteries until I can afford a large and decent pack but also want a charger setup for prolonged sunless days. The Classic is such a cool piece it seems logical to use it when the sun isn’t shining too!
12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Feeding Midnite Classic with multiple car chargers

    Take a look at this thread, towards the end: http://forum.solar-electric.com/showthread.php?17151-Do-any-battery-chargers-actually-do-it-all-right
    A MidNite Classic would make a very expensive battery charger. You know you can just parallel those auto chargers directly and the Amps will add up if needed? And their built-in regulators should (not going to vouch for quality here) allow them to play nicely together. They will not do the higher Voltage Absorb stage of course, but they would be capable of a decent Bulk charge.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Feeding Midnite Classic with multiple car chargers

    i will say that you can't do that without violating the warranty and you could possibly damage the classic too in the process with no guarantee the classic will function with those chargers as few have regulation circuits and none of those non-regulated chargers have the proper filtering that would allow the classic to possibly work.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Feeding Midnite Classic with multiple car chargers
    niel wrote: »
    i will say that you can't do that without violating the warranty and you could possibly damage the classic too in the process with no guarantee the classic will function with those chargers as few have regulation circuits and none of those non-regulated chargers have the proper filtering that would allow the classic to possibly work.

    That is certainly true. Most auto chargers have only 1/2 wave rectification and zero filtering. They really don't need it as they expect to be used as battery chargers not power supplies; the battery provides the 'filter', so to speak.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Feeding Midnite Classic with multiple car chargers
    H2SO4_guy wrote: »
    Is there any merit in taking 9 car battery chargers of the 10 amp variety, wire them in series

    Let's see:
    1. 9x14 volts = 126 volts, and without filtering that could go as high as 180 volts or more on peaks.
    I, for one, would not trust the secondary insulation on the chargers to be good for 150 volts. But it might be.

    2. If the chargers are really half-wave rectifiers (and I am not sure they would be. It would reduce cost and reduce the diode voltage drop though), then you would have to be careful to get the AC input plugs of each unit lined up the same way so that they are all producing output at the same time.

    3. An MPPT controller is going to try to drag the voltage down by increasing the current it draws. Depending on how the output of the chargers is current limited, it could hurt itself trying.
    SMA SB 3000, old BP panels.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Feeding Midnite Classic with multiple car chargers
    inetdog wrote: »
    2. If the chargers are really half-wave rectifiers (and I am not sure they would be. It would reduce cost and reduce the diode voltage drop though), then you would have to be careful to get the AC input plugs of each unit lined up the same way so that they are all producing output at the same time.

    You don't seriously think you can plug in any two given transformers and have their output in phase do you? :p

    Really; you ought to open one of those things up some time. After your initial gasp of horror you'll laugh.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Feeding Midnite Classic with multiple car chargers
    You don't seriously think you can plug in any two given transformers and have their output in phase do you? :p

    Really; you ought to open one of those things up some time. After your initial gasp of horror you'll laugh.

    Good point! I guess it will either take trial and error or a voltmeter. :-)

    At least there are only two choices.
    SMA SB 3000, old BP panels.
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