idle drops when headlight/foglight is on

[Kratos4age]

when driving at night..i just noticed my rpm drops to 600 and sometimes 500 when i switch on my headlights and foglights..when i turn it off it goes back up to 800rpm..whats do u think is wrong?my lights doesnt dim and the engine doesnt stall and everything is normal..strong acceleration..strong ac..it just drops whenever i turn on my headlights and fogs..
need your inputs
and btw my battery is motoloit 2sm gold which is 4 years old na

[jick.cejoco]

when driving at night..i just noticed my rpm drops to 600 and sometimes 500 when i switch on my headlights and foglights..when i turn it off it goes back up to 800rpm..whats do u think is wrong?my lights doesnt dim and the engine doesnt stall and everything is normal..strong acceleration..strong ac..it just drops whenever i turn on my headlights and fogs..
need your inputs
and btw my battery is motoloit 2sm gold which is 4 years old na

Kratos4age,
your battery has come of age. its capacity is diminishing that causes your voltage regulator to increase the dwell or on time versus of time. the transistorized voltage regulator does this on-off cycle several thousand times per second (hertz or cycles per second or cps) and the on time is more prolonged when the charging demand is higher adding load to the engine.
jick

[speed unlimited]

Bring it to battery Shop for test regarding the charging rate when the aircon , headlight and all accessory on they can easily tell weather the battery is weak or there problem regarding the alternator. They will not charge you for check up. I think thats the best way to solve your problem . They are expert regarding there product . A four year old battery need to be check.

[1D4LV]

4 year old battery? its the battery alright. one of these days, hindi na lang magstart yang oto mo.

[p_borj]

WOW! As in WOW! 4 years old battery, ako nga kahit Motolite Gold pa hindi umaabot ng 2 years.

Tingin ko battery rin ang culprit. Why? Ang alternator ang nagsu-supply ng power sa sasakyan. Pero ang alternator kapag madaming load, ito ay kumukuha na ng extra power from the battery itself. Lalo na sa gabi tapos maulan (headlights on, wipers on, aircon on, radio on), yung mga dagdag na load na iyon ay hindi kaya ng alternator itself so dito pumapapel ulit si battery.

Try to test the battery, kung for example below 50% nalang ang power niya (which is I'm quite 95% sure dahil 4y/o na battery mo), that might be your problem.