FAQ
TL;DR: Only 11.8 V open-circuit voltage leaves ~20 % charge, enough to stall most starters (Battery University 2023), and as one expert notes, "should be over 14 V while running" [Elektroda, adamkowalski431,#16794032]. Replace the sulfated 5-year-old battery; alternator readings are within spec.
Why it matters: A weak battery masks other faults and strands you at the worst moment.
Quick Facts
• Healthy alternator output: 13.8–14.4 V at 1,500 rpm [Bosch, 2021]
• Fully-charged 12 V lead-acid battery: 12.6–12.8 V open circuit (Battery University 2023)
• Self-discharge: ~1 % per day at 25 °C; doubles every 10 °C rise (Battery University 2023)
• Typical parasitic draw for 1999-2002 Lanos: 30–60 mA [Haynes, 2019]
• Average costs (Poland): new 60 Ah battery 250–350 PLN; used alternator 150–300 PLN; swap labour 50 PLN [Elektroda, andrzej20001,#16794048]
What alternator voltage should I see on a Daewoo Lanos?
Measure across the battery with engine at 1,500 rpm and lights off. You should read 13.8–14.4 V. Below 13.5 V indicates weak charging; above 15 V means the regulator overcharges [Bosch, 2021]. Marta’s 13.9 V idle reading is acceptable [Elektroda, marta443,#16793998].
Why did the battery die after a 3-week parking break?
Lead-acid batteries self-discharge around 1 % daily at 25 °C; three weeks can drop a 60 Ah unit by 12–20 Ah, leaving <50 % state-of-charge (SOC) [Battery University 2023]. Deep discharge causes sulfation that permanently cuts capacity [DOE, 2020].
How can I separate battery faults from alternator faults in 5 minutes?
- Measure battery at rest: ≥12.6 V means charged. 2. Start engine; note voltage. Rise to 14 V shows alternator works. 3. Switch headlights and blower on; voltage must stay ≥13.8 V. Drop to 12 V points to alternator or cabling issue [Elektroda, tzok,#16794489].
My meter showed 9.8 V during a start attempt—what does that mean?
Cranking voltage below 10 V signals at least one shorted cell or heavy sulfation. A healthy 12 V battery should stay above 10.5 V under starter load [SAE J537]. Replace the battery; further charging won’t restore lost capacity [Elektroda, marta443,#16796901].
What standby (parasitic) current is acceptable on a Lanos?
30–60 mA is typical; values under 80 mA rarely drain a 60 Ah battery in under two weeks [Haynes, 2019]. Marta’s measurement of 0.5 mA was likely a meter range error; re-check using the 10 A port and wait 5 minutes for modules to sleep [Elektroda, enhanced,#16794771].
Can loose clamps really stop the engine from starting?
Yes. High-resistance clamps drop voltage during starter peaks (150–200 A). Even 0.05 Ω can rob 10 V (V=IR), leaving electronics dead. Cleaning and tightening restored Marta’s starts for a week [Elektroda, marta443,#16793998].
Is 14.8 V right after cold start harmful?
Momentary 14.8 V is normal on cold mornings; regulators lower to <14.4 V as the alternator warms. Sustained >15 V boils electrolyte and can fry ECUs—an edge-case to monitor with a voltmeter [Delphi, 2022].
How long should I charge a 60 Ah battery with a 6 A charger?
At 80 % efficiency, you need about 11 hours to move the 40 Ah required from 0 % to full SOC: (60 Ah ×100 %) ÷ (6 A ×0.8) ≈ 12.5 h. Stop when current falls below 1 A or voltage reaches 14.4 V (constant voltage phase) [CTEK, 2021].
What does labour and parts cost to swap an alternator on a Lanos in Poland?
Used alternator: 150–300 PLN; new aftermarket: 400–600 PLN. Average labour: 50–80 PLN because it’s a 30-minute job with basic tools [Elektroda, andrzej20001,#16794048].
How do I measure parasitic draw with a multimeter?
- Turn ignition off; close doors. 2. Set meter to 10 A; place in series between battery positive post and cable. 3. Wait 5 minutes for control units to sleep, then read amperage. Values above 80 mA mean a "current thief" [Elektroda, enhanced,#16794066].
Could a failing diode in the alternator mimic a bad battery?
Yes. A shorted diode reduces charging current and can leak reverse current overnight, draining 0.5–2 A—enough to flatten a 60 Ah battery in 1–2 days. It also produces AC ripple that ages batteries faster [Bosch, 2021].
When is it smarter to scrap than repair a 19-year-old Lanos?
Add expected costs: battery 300 PLN, tyres 900 PLN, suspension 800 PLN. If the sum exceeds 60 % of the car’s market value (~2,500 PLN) it is economically wiser to sell or scrap [Polish Auto-Trader, 2023].
I take measurements, they are ok. Unfortunately, before the exchange, I did not measure the energy consumption - I read it too late, anyway, the exchange was very quick, after the store was closed. I will let you know but the measurements are different than with the transverse battery - higher values after turning off the engine and it does not drop so quickly, I also think that a good move. I will measure for some time because it is a pity to discharge the new battery.
