Charging 24 volt forklift battery with large 12 volt charger?

softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭

Purists may be spitting up a bit but it is working quite well. Once again, my outdoor battery connections have "gone south". Recharging at 65 amps and doing six cells at a time. Gets a pretty good electrolyte boil going.

It is a service garage type Shumacher charger with 20, 40, 65, and 225 amp selections. The voltage isn't very high, about 13.4ish or so. I may charge five cells (10 volts) at 13.4ish for equalization purposes once a full charge is achieved. Which will take awhile with a 1652 pound battery.

Can't seem to find my 24 volt charger...

Far too distracted to fix the system - yet again. Besides the battery needs to be equalized.

When truly off grid, improvisation can be ones best friend.

First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries

Comments

  • softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭

    Ongoing problems with outdoor battery connections - and a long story.

    Can't I just ground the negative from the charge controller? That would be one less outdoor battery connection.

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • BB.BB. Super Moderators, Administrators Posts: 32,331 admin

    Yes, you can use your ground reference negative cable for both current and safety grounding (i.e., grounding the case of the charge controller and carrying the negative current from the charge controller to the battery bus).

    The idea was for safety grounds to never carry current in normal operation, only in fault conditions. You can get into some really strange issues with using a conductor for both heavy current and ground bonding.

    Besides the issue of where does lightning current "go" (not sure that 2 wires to controller or 2 wires + ground wire makes a huge difference in this case), you could end up with (for example), your return cable may have upwards of 1 volt of voltage drop on it. And if your controller (or inverter) was mounted to copper treated wood, or other metal structure, you now have energized random pieces of metal with respect to ground and can cause corrosion/electrolysis.

    If you are working with larger (expensive) cables, the safety grounding cable does not have to be the same diameter/AWG as the power cables--It just has to be heavy enough to trip the fuse/breaker for those heavy cable circuits (6 AWG "fuses" at ~600 Amps--It normally will trip a breaker/fuse rated upwards of 200 Amps--I believe that is what NEC uses for safety ground for up to 200 Amp mains panels).

    If you are thinking of using smaller AWG cables--And have a copy of the NEC, you (or somebody here) can find the ground cable references.

    Another issue to watch for. Some Solar Charge Controllers are true 4 wire devices (+- PV in / +- BATT out). Schneider 60 MPPT controller is one of these (don't know about others). And if you somehow connect PV - to Batt- terminals together, you bypass the internal current sense shunt inside the controller and will get it terribly confused.

    And--If your charge controller uses the NEC DC GFI Ground Fault sensing fuse (or circuit breaker), connecting Chassi/green wire ground to negative Return anywhere in your system will bypass the DC GFI sense fuse/breaker and render it inoperative or at least unreliable.

    On my system, I would run DC +/- power on its own cables, and a separate (albeit smaller AWG) cable for safety ground. And tie Negative Return bus and Safety Ground in one place. It makes it much easier to find wiring/connection faults this way--Rather than have your grounding system carrying your high current connections.

    In things with "moving parts", running significant current through bearings, bushing, and hinges was a quick way to cause early mechanical failures.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭
    edited April 2019 #4

    I'm going to look like an idiot for saying this but that was never deterred my explorations.

    AC carries negative current - often in a white line. I'm not convinced that DC carries any current in a negative line. My memory is not what it used to be.

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • BB.BB. Super Moderators, Administrators Posts: 32,331 admin

    Whatever current flows out one cable, the return cable carries and equal and opposite current flow.

    DC... The current flows in one direction only. Hence "direct current".

    AC, the current flows "back and forth" (sine wave, 1/2 the time in one direction, and the other 1/2 of the time, the other direction--60 cycles per second).

    With 120/240 VAC north American split phase current, we have a center tapped transformer. With L1, L2, and the center tap Neutral.

    So, if you have 120 VAC, the current flows from L1 to Neutral. Or L2 to neutral. The Neutral being the ground referenced return.

    However, if you are flowing 240 VAC, the current flows out L1 and returns on L2 (or, if you like, flows out L2 and returns on L1). And there is no current flow in the Neutral. So, you are correct that when you have a L1 to L2 240 VAC load, there is no current in the Neutral.

    And this is also true if you have L1+L2+Neutral going to a pair of 120 VAC loads... One load on L1 to neutral, and a second load on L2 to neutral. If the two loads are "matched" (like two 100 Watt light bulbs), there is very little current flow on the Neutral--All the current flows "out" L1 and "back" on L2.

    AC or DC, in itself, does not matter. If you had two 12 volt batteries and grounded the "middle" of the bank. One battery supplies +12 and return (aka "the neutral"). And the second battery supplies -12 and return. If you connected a load from L1 to neutral, you would get +12 volts and current in the return (neutral) line. If you connected a 24 volt load between +12 and -12 lines, you would not have any current flow in the Return/Neutral wire.

    Off hand, I cannot think of any consumer power system today that use +12/-12/Neutral "return" output (or similar DC voltages) from a central power supply. In older tube type audio systems and op-amp based amplifier systems, we do have "ground referenced" + and - supplies around ground. This allows the amplifiers to output power + and - around ground referenced neutral. But these days, this is normally a +/- power system inside the black box (radio, audio amplifiers, etc.), not powered from an external power system--And usually not from a battery system. There are (where) other digital logic systems that use negative voltage (ECL) and translators to positive digital logic systems ("what we normally" use today).

    When you have +/- referenced loads from "Two center tapped Batteries", we get into the old issue of the problems with tapping 12 volts from a 24 volt battery bank--Unbalanced draws from "low" and "high" battery bank means you basically need two charging sources--One for the low bank and a second for the high bank of batteries to keep them "equalized".

    With AC power, we have the "simple" center tapped transformer that can supply split phase power (L1, L2, Neutral) very easily, no "batteries" or electronic DC to DC converters required.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭

    In any circuit, be it AC single phase or DC it's a closed loop, just because one leg is grounded, be it neutral or negative, doesn't mean it has no current flow, it simply means the current flow is common to earth/ground. We often here of ballancing loads in a split or three phase system to limit the unbalanced load from traveling through the neutral, this is undesirable because there is a loss between the two or three windings of a transformer or generating source, it's not a 100% closed loop.

    For the purposes of single phase AC, or DC circuits ,the electrons just want to return home to complete the loop, the purpose of grounding a leg, be it negative or neutral, is to provide a path for electrons to flow in the event of a wiring misadventure, which will in turn overwhelm the overcurrent protection device, rendering the circuit safe.

    There are no stupid questions, by the way, curiosity is the window to enlightenment.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • TecnodaveTecnodave Registered Users Posts: 437 ✭✭✭✭

    BB,

    one more controller that is 4 wire .....p.v. Negative cannot be connected to battery negative....it measures current in the negative.......The MidNite Kid...all versions. They get confused as it cannot "see" p.v. current if PV negative goes to battery negative. I have two early beta kid controllers and am in kid beta test program.

    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
Sign In or Register to comment.