Load balance
Total load current = sum of continuous loads. The alternator must supply the loads plus battery charging current.
Alternator output at idle is lower than its rated maximum.
Automotive
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Alternator Output Calculator
Sum vehicle electrical loads and estimate the alternator headroom at idle.
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List continuous loads, add a charging allowance and compare with alternator rating.
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Assumptions and limits.
- Educational load-sum estimate at operating RPM; alternator regulation, temperature and pulley ratio are not modelled.
Frequently asked questions
Does a bigger alternator always fix dim lights?
No. Wiring, grounds, battery condition and pulley ratio also affect charging performance.