A standard multimeter does not show how much current the battery can deliver during engine startup. Even with a reading of 12.6 V, a worn battery may experience a major voltage drop under load. That is why at our service station we also test the battery with a digital battery tester that measures internal resistance and cold cranking current.<\/p>\n
If the battery is more than 4\u20135 years old, it is already in the risk zone. Even a battery that appears to be working normally may fail during the first severe frost.<\/p>\n
Why Does the Battery Die While the Car Is Parked?<\/h2>\n
If a fully charged battery becomes discharged after 1\u20133 days of parking, there is most likely a parasitic current drain. This is electrical consumption while the vehicle is switched off and locked.<\/p>\n
For most vehicles, normal parasitic draw is approximately 20\u201350 mA after all electronic control units have entered sleep mode. On modern vehicles, this usually happens 20\u201340 minutes after the car is locked. Anything significantly above this level will gradually discharge the battery.<\/p>\n
The most common causes of parasitic drain include:<\/strong><\/p>\n Finding a parasitic drain yourself can be difficult. To measure it correctly, you need to wait until all electronic modules enter sleep mode and avoid waking them by opening the doors. At our service station, we use an ammeter and disconnect fuses one by one to identify the circuit responsible for the current draw.<\/p>\n Start the engine and measure the voltage at the battery terminals.<\/p>\n On vehicles equipped with start-stop systems and \u00absmart\u00bb alternators, voltage may vary from 12.5 to 15 V. On these vehicles, the charging system should be assessed using scanner diagnostics rather than voltage readings alone.<\/p>\n A multimeter will not reveal a failed diode in the alternator rectifier bridge. In this case, the alternator may still produce sufficient voltage but allow AC ripple, which can discharge the battery. We check this with an oscilloscope, which displays the waveform.<\/p>\n If the alternator is faulty, we can repair it by replacing the brushes, voltage regulator, diode bridge, bearings, or overrunning pulley. A complete alternator replacement is not always necessary.<\/p>\n At Autopark-Service, we can test the battery, measure parasitic current draw, and check alternator performance under load during a single visit. If necessary, we repair the alternator and locate current leaks in the vehicle wiring.<\/p>\n Book an appointment with an auto electrician in Lviv: +380 91 481 9004, 60 Kiltseva St. We are open 24\/7, so you can bring your vehicle in during the evening. Learn more on the auto electrician<\/a> page.<\/p>\n If the battery is healthy and fully charged, there is no need to remove it. Removing the battery only makes sense if it is old or if the vehicle will be parked for a week or longer.<\/p>\n It is not recommended. A frozen or extremely cold battery does not accept charge well, and frozen electrolyte may damage the battery. Bring the battery into a warm room for several hours before charging it.<\/p>\n Usually 4\u20136 years. Frequent short trips, deep discharges, and a faulty alternator can significantly reduce its service life.<\/p>\n If the battery loses charge while driving, the alternator is likely responsible. If it discharges while the vehicle is parked, a parasitic current drain should be investigated. Current measurements and alternator testing at a service station can identify the exact cause.<\/p>\n Yes. If there is a parasitic drain or the alternator is not charging properly, a new battery will also discharge. That is why the charging system should be checked first.<\/p>\n Read also: car is difficult to start in winter<\/a>, electrical wiring faults<\/a>, oscilloscope diagnostics for cars in Lviv<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":" In short: a healthy, fully charged battery should show 12.6\u201312.7 V at rest, while voltage with the engine running should…<\/p>\n","protected":false},"author":5,"featured_media":4332,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-4331","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-article"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/posts\/4331","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/comments?post=4331"}],"version-history":[{"count":3,"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/posts\/4331\/revisions"}],"predecessor-version":[{"id":4336,"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/posts\/4331\/revisions\/4336"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/media\/4332"}],"wp:attachment":[{"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/media?parent=4331"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/categories?post=4331"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/autopark-service.com.ua\/en\/wp-json\/wp\/v2\/tags?post=4331"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\n
How to Check the Alternator<\/h2>\n
![\"1.](\"http:\/\/autopark-service.com.ua\/wp-content\/uploads\/2026\/09\/akumulyator-sidaye-vzymku-perevirka-akb-generatora-2.webp\")
<\/p>\n\n
What to Do Before Freezing Weather<\/h2>\n
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Battery and Alternator Diagnostics in Lviv<\/h2>\n
Frequently Asked Questions<\/h2>\n
Should I Remove the Battery Overnight in Freezing Weather?<\/h3>\n
Can I Charge a Car Battery in Freezing Temperatures?<\/h3>\n
How Long Does a Car Battery Last?<\/h3>\n
How Can I Tell Whether the Alternator or a Parasitic Drain Is Discharging the Battery?<\/h3>\n
Can a New Battery Still Go Flat?<\/h3>\n