24 volt inverters -- tapped off of a 48 volt battery bank

mrleemus1

Here's what I think I want to do. My existing system consist of 2 of the Trace 24 volt inverters that run off of (2) large 24 volt battery banks; that are controlled by 2 OUTBACK 60 amp controllers. The PV array is @ 1,500 watts for each controller (3,000) watt total system.

I want to install another 3,000 watt PV array. Can I series the batteries up to 48 volts -- tap off the bank at 24 volts for the inverters and wire the controllers to the 48 volt taps.

Would save me over $1,000--- the cost of two new mppt controllers.

Lee

BB.

Highly recommended not to draw 24 volts from a 48 volt battery bank. You will (usually) unbalance the two battery banks and one will be under charged and the other over charged (assuming 48 volt charge controller).

Another issue that can really mess you up... You now have a ground at 0 volts and a second ground at 24 volts (for the inverter and, if configured, the "high bank" 24 volt solar charge controller).

Having "hot grounds" is always ripe for confusion (if you use RS 232 communications, dry contact relays, etc. that usually reference "local ground"--It makes for interconnecting hardware confusing, and potentially short circuits 1/2 your battery bank). Also, "hot grounds" need their own fusing/circuit breakers to protect the "high bank" "ground" runs.

If you have both 24 volt (high and and low bank) battery chargers, and a 48 volt battery charger--It can work, albeit inefficiently to ineffectively (can you split your loads so that the two 24 volt battery banks discharge at roughly the same rate so that your 48 volt battery charge can recharge/rebulk your battery bank, and then let the high/low 24 volt charge controller "balance" that two banks during absorb/float/equalization charging?).

I humbly suggest that you do not do this. Either pick 24 volt battery bank, or pick 48 volt battery bank and get some new AC inverters/AC chargers (assuming you use genset/grid power to recharge during times of bad weather/heavy loads).

Looking at the system level wiring, if your "final" 24 volt battery bank is >800 AH (and your solar array + AC inverter usage is >~4,000 Watts on the 24 volt battery bank) or so, then you probably want to look at going to a 48 volt battery system anyway. Details about your energy needs and system configuration details do matter.

I humbly ask that you do not do the split bank system. In the best of times, it is just an accident waiting to happen.

-Bill

Raj174

I believe uneven loads on the inverters would destabilize the 48 volt bank.

Rick

Dave Angelini

As above from Rick and Bill, Don't do this

mrleemus1

Bill -- thanks so much for your expertise -- knowledge -- and willingness to help me out. I will discontinue all thoughts of doing that-- and start looking for a couple new 24 volt mppt controllers

AGAIN THANKS - I do appreciate it

Lee