I am wondering if I can connect a 120 volt DC battery as input voltage to charge my 24 volt system. I have numerous A123 bus batteries at 40 volts and I have a inverter that runs on 120 volts DC so I am putting 3 bus batteries in series to make 120volts and charging that with solar panels through a charge controller capable of controlling 120 volts DC.
I want to take some voltage off the battery bank to run my 24 volt inverter and battery bank. SO I am wondering if the 250 classic configured to run on Constant voltage would do the trick or would the classic run out of control and pull too many amps.
Are you asking if you can use the Classic to charge a 24v battery pack from a 120v battery pack ?
Answer is yes if you don't exceed the Classic voltage limits - check the specs. Just keep in mind that the larger the voltage difference between the voltage source and the battery voltage the less efficient the Classic would be - so mean it gets warmer. So have good ventilation around the Classic . But if the voltages are in the design limits then should be no problem. You can limit the input amps and the output amps from the Classic if you want to .
If you are talking about running an inverter on 24v directly from the Classic with no battery pack I would say no - you need a 24v battery .
Larry
Do you have an inverter/charger in the system ? That is the best way to use the system or if not, a 24V battery charger
meant to operate from 120 VAC.
The Classic is made to operate from PV solar modules and arrays, not a low impedance source like the grid.
Some have made what you are talking about work but is a kludge and is not supported by MidNite.
boB
Morningstar rates it's MPPT as being able to downconvert from a battery to another battery. I don't know if they thought of such a high voltage battery though, I suspect most of their testing was done with 48V and 12V batterys
Quote from: ClassicCrazy on February 18, 2019, 11:42:05 AM
Are you asking if you can use the Classic to charge a 24v battery pack from a 120v battery pack ?
Answer is yes if you don't exceed the Classic voltage limits - check the specs. Just keep in mind that the larger the voltage difference between the voltage source and the battery voltage the less efficient the Classic would be - so mean it gets warmer. So have good ventilation around the Classic . But if the voltages are in the design limits then should be no problem. You can limit the input amps and the output amps from the Classic if you want to .
If you are talking about running an inverter on 24v directly from the Classic with no battery pack I would say no - you need a 24v battery .
Larry
Thanks for the reply,
Yes I want to charge a 24 volt battery bank with my classic 250 as a charge controller using the input voltage from a 120 volt DC battery. The 120 volt is within voltage requirements and I have noticed there is a constant voltage option I can turn on for input voltage. My concern was the classic may pull too many amps as with PV we are limited to a certain wattage which would keep the amps down, whereas the 120 volt dc battery would have unlimited watts.
The pv I have now is 2400 watts from 8 panels 2 strings of 4 on an outback VFX3524 inverter and on sunny days in the winter it max's out the classic at 61 volts (1700 watts) and I get a warning. By feeding it from a controlled voltage I could make use of my other inverter which is 120 volt DC which I would have on the separate 120 volt battery bank. Sounds confusing but I would have 240 volts AC and twice as much AC available with two inverters the outback on the 120 volt AC panel and the other inverter on a 240 volt AC panel.
I just didn't know if the classic would accept that many amps, you say I can set the input amperage so that is the answer if the classic try's to pull more amps than it is supposed to.
Quote from: mike90045 on February 18, 2019, 03:30:29 PM
Morningstar rates it's MPPT as being able to downconvert from a battery to another battery. I don't know if they thought of such a high voltage battery though, I suspect most of their testing was done with 48V and 12V batterys
Thanks for reply
I have an old Tracer 4215 20 amp Mppt -BN series 24 volt limited to 1040 watts. It will take up to 150 volts but the algorithm will track past it's limit if there is amps available but I have been told they will run away with the amps and burn up which is why I wondered about the classic 250.
Quote from: boB on February 18, 2019, 01:26:48 PM
Do you have an inverter/charger in the system ? That is the best way to use the system or if not, a 24V battery charger
meant to operate from 120 VAC.
The Classic is made to operate from PV solar modules and arrays, not a low impedance source like the grid.
Some have made what you are talking about work but is a kludge and is not supported by MidNite.
boB
Thanks for the reply
Yes I can charge the 24 volt battery bank from the grid using the VFX3524 but I want to use the pv array to charge and I also want to use my other inverter which is 120 volts DC so my idea was to charge the 120 vdc battery from the array and then bleed of some voltage for the 24 vdc system.
First I will say that things can go wrong so use at your own risk.
That said, Dont use a Classic 250 use a Classic 150 or 200 if you must. Now the issue you will have is the current available from the 120v battery.
I would use a 1-2 ohm resistor in series on the Battery positive lead on the 120v battery into the classic
I would use one of the manual modes, likely manual hydro mode with the voltage fixed so it doesnt try and sweep the voltage down
I would set the INPUT current to something small in the beginning and work up on it.
All in All it should work ok the issue you could have is if just wired up like PV and set in solar mode it will try to track down to the 24v battery and the current inrush may damage something, thats why the resistor in series it acts as a shock absorber
Thanks