Why Do some Batteries Connected in Series Heat Up? Causes, Safety Risks, and Prevention Tips. Internal resistance of the battery is explained.
To understand this, let’s solve a quiz.
Higher resistance dissipates more power in a series circuit:
Two lamps. 40W and 100W are connected in series. Which one will give more light?
Popular to the misbelief that having more wattage, 100W, will give more light.
No, exactly apposite, 40W will give more light. Why? Because a 40W bulb has more filament resistance than a 100W bulb.
In a series circuit, the current remains constant, so the I^2 x R product, i.e., heat, is greater for a 40W lamp than for a 100W lamp, hence producing more light.
Batteries are connected in series for the Inverter and UPS:
Why all this rant? Because batteries are commonly connected in series, especially in UPS systems.
Every battery has an Internal resistance:
Why do some batteries have more internal resistance? It depends on the age of the battery and the brand.
Are you mixing old and new batteries?
Old battles have more internal resistance than new ones. So they heat up.
Conclusion:
The moral of the story is always connect fresh batteries of the same brand in the series. Periodically check the internal impedance of the battery and replace those with more resistance with a new one, as batteries (connected in series) do not wear out evenly over time.
FAQ Set:
Q1: Why do batteries connected in series heat up?
Batteries heat up in series due to internal resistance, overcurrent, or mismatched battery characteristics, causing energy to dissipate as heat.
Q2: What is internal resistance in a battery?
Internal resistance is the inherent opposition inside a battery to the flow of current. High current causes a voltage drop and heat generation inside the battery.
Q3: How does a series connection affect heating?
In a series, the same current flows through all batteries. If one battery has higher internal resistance or lower capacity, it can overheat faster, leading to imbalance and potential failure.
Q4: What are the safety risks of overheating batteries?
Leakage of electrolyte
Swelling or rupture of the battery casing
Fire or explosion in extreme cases
Q5: How can heating be prevented in series battery connections?
Use batteries of the same type, age, and capacity
Avoid drawing excessive current beyond the battery rating
Monitor battery temperature during charging or use
Include fuses or current-limiting devices for protection
Q6: Can series-connected batteries recover from slight overheating?
Minor heating may dissipate after resting, but repeated overheating reduces battery life and can cause permanent damage.
Q7: Are there alternatives to a series connection to reduce heating?
Parallel connections can share the current load
Use battery management systems (BMS) in rechargeable packs to balance charge and prevent overheating
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