How can I estimate the heat generated by the battery pack / charger with the below specifications?

1 no. 48V/40A Constant Voltage Battery Charger


Input volts:                 230 volts, single phase, 50 Hz
Input VA:                    3400VA
Output volts:                48 volts 
Charger nominal rating:      40 amps 
Charger ‘Peak Load’ rating:  Three times nominal
End of discharge:            42 volts
Output ripple:               200mV (with battery connected)
Ambient temperature range:   -5°C to 40°C

Type:         Sealed lead acid
Capacity:     180Ah (1 string of 4 blocks)                      
No. of cells: 24 
Float volts:  54.48V    
Boost volts:  N/A
Battery MCB:  100A
  • \$\begingroup\$ Those weren't designed to work with each other, were they? \$\endgroup\$ May 26 at 12:53
  • \$\begingroup\$ it seems like a traction battery system… for the battery you could estimate that about 30% of the power you put it is dissipated; for the charger it's difficult to say but the instruction manual usually has pointers for cooling and ventilation \$\endgroup\$ May 26 at 13:05
  • \$\begingroup\$ Good info: batteryuniversity.com/articles \$\endgroup\$
    – rdtsc
    May 26 at 13:16
  • \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    May 26 at 14:38

1 Answer 1


the edits in question clearly indicate ESR if tested during 40 A.

200mV / 40 A = 5mohm and 8 Watts of heat

The battery is capable of delivering 8kW of external heat if CCA tested with a 5V drop from 12.5V per pack.

This is near theoretical MPT for a shorted pack. with shorted jumper cables matching battery ESR with matched impedances.

The CCA rating for a new battery pack is designed to meet the rated spec near H2O freezing. The room temp CA rating is higher and increases with temperature but decreases with aging slowly and rapidly below 10% SOC.

ESR is inversely related to CCA @ T for a 5V drop from ~ 12.5V (100% SOC) thus new cold \$ESR =5V/ I_{CCA}, Pd = I_{CCA}^2*ESR \$

e.g. CCA = 1000 A then ESR = 0.005 Ohms and Pd= 5 kW during CCA test for each battery.

But for CC=40A charge rate , Pd= 8W if CCA = 1kA, 80W if CCA = 100A from aging test for a 5V drop. etc. **Compared to power transfer 8W/(14V40A)100%= 1.4 % Loss This obviously rises with Depth of Discharge, DoD, and Voltage overcharge above 14V causing outgassing from kinetic energy.

This CCA test or cold car start is rated for 30 seconds time limit, in case of a bad 2V cell and outgassing of explosive H2, as battery warms up.

  • Always measure Specific Gravity for battery health in each 2V cell if possible and record from new to end-of-life (EOL).
  • BMS systems help but must dissipate 10% of charge power in case of imbalance or 10% * 40A * 14.2V = 57 W.
  • 5W @ risetime <= 100 ns @ > 20 kHz pulse charging only during DC charging can replace a BMS system and greatly extend the life of motive power batteries and re-balance S.G. within 1 week of use.

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