Charge 48 volt battery bank by 96 volt battery bank? Possible?

[chromeaccent]

Hi All,

I want to charge a 700 Ah 48 volt battery bank(Forklift battery) by using a Classic 150 or 200 drawing power from a 96 volt 700 Ah(Series two 48 volt bank) battery bank, 96 volt battery bank will be charged by high voltage solar array. Is this possible or even recommended?

Thanks.

[Ron Swanson]

I believe we know of one person doing something similar with a 60 volt to 48 volt battery system, and as far as I know it has been working for years.  I will try to check up on this.

[KyleM]

Hi All,

I want to charge a 700 Ah 48 volt battery bank(Forklift battery) by using a Classic 150 or 200 drawing power from a 96 volt 700 Ah(Series two 48 volt bank) battery bank, 96 volt battery bank will be charged by high voltage solar array. Is this possible or even recommended?

Thanks.

Theoretically this is possible. DC current is DC current to charge controllers. As long as the voltage is high enough to trigger the MPPT charging cycle  ( 130% of 48 volts in this case = 62.5 volts)

I would probably use the Solar mode or Legacy P&O.

This does fall outside of Midnite's support parameters so if it doesn't work you will be on your own for Support.   Well I am sure you will find some people here that would be willing to help. 

Good luck
Kyle M

[mike90045]

I recall that the Morningstar MPPT controllers are able to charge from batteries or a stiff power supply. Might be tough on it, but they claim it works

[ClassicCrazy]

I used my Midnite Kid to charge 12v battery  from 24v battery pack . It worked fine.  I don't see why the Classic wouldn't do the same thing. You can adjust the current output if you want to via settings on the Classic if you need to to keep the Classic happy ( not too hot ) .

Larry

[chromeaccent]

Thanks for your feedback guy's.

I believe we know of one person doing something similar with a 60 volt to 48 volt battery system, and as far as I know it has been working for years.  I will try to check up on this.

Ron, let me know what you find.
  I will try and discuss my plans with Midnite... just in case they have another view on the matter as I don't want to risk torching a Classic.

[CDN-VT]

One thing I would think / do is have the 96Vdc trip a relay to feed the 48Vdc feed like solar came alive , then you know the night reset could be a timing factor to start to tune in the settings . anoter thing is the make sure the 48Vdc will not drain the 96Vdc feed , hence a breaking of input. With Amps governed to the 48Vdc.

I use a few adjustable 12Vdc Buck transformers on times , set to 14.7Vdc .

VT

[FNG]

The issue is the stiff source and the fact it is not current limited like a pv module, You would want to use Hydro mode and slowly drop the fixed MPPT voltage down until you get some current flow. Also make SURE you have the current limit set to a lower value to start and get things working. Last thing I could suggest is a large 1 or 2 ohm resistor in series in the 96 volt positive line to soften it some.'

Also be aware this will void your warranty most likely

FNG

[Ron Swanson]

Ron, let me know what you find.
  I will try and discuss my plans with Midnite... just in case they have another view on the matter as I don't want to risk torching a Classic.
[/quote]

Sorry I forgot to update here.  Anyway I asked about it.  This was a system designed by an EE with no outside help apparently.  He has a 60V bank in the shop and a 48V bank in the house.  Apparently this was done because he ran too small of wire to the house for direct DC to be able to fill batteries in a reasonable time.  Don't ask.

Anyway it works, using an Outback CC I believe and no special hardware.  Maybe the length of wire serves to soften the stiff battery source, I don't know.