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DC Battery Bank

Enter the load, system voltage (12/24/48 VDC), autonomy and depth of discharge and I compute the required capacity (Ah), the battery array (series for voltage, parallel for capacity) and the C-rate.

W
V
h

How much of the battery you use. Lead-acid 50 %; lithium 80–100 %.

Wiring and DC conversion losses. Typical 90 %.

Usable capacity vs. temperature. Cold uses 0.90; at 20–25 °C 1.00.

Bank battery
V
Ah

Specs of one battery. They go in series for voltage and in parallel for capacity.

Examples
redzilla.cl — bank 
 
  
 
 
Required capacity
 
—
 
at system voltage
 
 
 
Total batteries
 
—
 
series × parallel
 
 
 
Required energy
 
—
 
on the bank
 
 
 
Discharge C-rate
 
—
 
current / capacity
 
 
  
 
 Ah req. —  
 
 Array —  
 
 Batteries —  
 
  
 
Bank array
 
 
 — in series · — in parallel — 
 
 
 
—
 
  
 
Calculation breakdown
 
 
  
ItemValueDetail
   
 
 
 
 How it is computed · Wh, Ah and array 
 
 1. Required energy:
Wh = load_W × autonomy_h. If the load is AC downstream
            of an inverter, divide by the inverter efficiency.

 
 2. Capacity at the system voltage:
Ah = Wh / (Vsys × DoD × efficiency × tempDerate)
(DoD, efficiency and temperature as fractions).

 
 3. Array with batteries of
Vbat / Ah_bat:
series = Vsys / Vbat (for voltage) and
parallel = ceil(Ah_req / Ah_bat) (for capacity).
            The total is series × parallel.

 
 4. Discharge C-rate:
C = (load_W / Vsys) / Ah_installed. A high C-rate
            (> 0.5 C on lead-acid) lowers the real capacity via the Peukert effect.

 
 ! This is a sizing estimate.
            Check the maximum discharge current the battery allows, the balance of
            the parallel strings and the actual operating temperature.

 
 
 
 
 
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