12/30/2023 0 Comments 2015 chevy equinox battery jumpWhile many people like to say 12.75v is 100% as absolute fact, actual full charge resting voltage varies quite widely across different batteries and the climate they were intended to be used in.Īctual full charge resting voltage would ideally be figured out when the battery was spanking new, fully charged, and its temperature recorded as well, and all future voltage readigs can then be compared to this initial recording, and hopefully the battery temperature is similar too. Voltage is only accurate as to state of charge on a battery which has not seen any charging or discharging currents for a long period of time, the longer period of time, the more accurate it is. Starting a load test with a less than fully charged battery, is throwing a monkey wrench into the test, unless the state of charge of the battery is the same at the beginning for the tests, which is also not easy to determine as voltage is not the fuel gauge that people assume it is. If the loads are known, and they are applied for a known amount of time, then that is a load test, comparable to future load tests using the same loads and durations. Charging a batery from 80% to 100% takes no less than 3.5 hours, assuming mid 14 volts can be attained and held for thoe 3.5 hours.ĭo not expect your vehicle to hold mid 14's even if you are to drive 3.5 hours.ĭo not assume the voltage your vehicle allows after start up, is the voltage it always holds.ĭo not trust your dashboard voltmeter to actually represent true battery terminal voltage. One kept 75 to 85% charged, subjected to medium high average ambient temperatures, and never ever allowed to reach true 100% charged will be lucky to last 2 years.ĭo not assume your vehicle can or does fully charge the battery. One kept in the 85 to 95% charged range never fully charged 100%, and subjected to high average temperatures, might be extremely lucky to last 4 years. Any data can help educate those guesses, but with no data or experience with the same vehicle, there is not much point in guessing.Ī 4 year old battery kept cool and is fully charged at all times, or very nearly so, could easily live 4 more years. So unless the loads on the battery are known as either wattage or amperage, then judging how long a battery powers a load before it no longer has the ability to start is pure conjecture. Painting all vehicles with the same brush as to the amount of this parasitic draw would be overwhelmingly asinine, without actual data on a specifc vehicle. The ACC Key position can have other quiescent/parasitic draws even if the stereo is off. It can be turned on with the remote and still connect to my bluetooth phone when the stereo is off, so its 0.3 amp draw when off, is a bit excessive. If my stereo is turned off, but its ignition switched wire is still on, it is drawing 0.3 amps. spinning the CD player uses more amperage than bluetooth or using the Aux input. Turned on volume all the way down my stereo draws about 0.8 amps, volume about 1/4 the max and amperage is about 3.2 amps. Subwoofers are Vampires, even at low volumes. ![]() Additional amplifiers vastly increase the amp draw. My stereo which is a simple pioneer head unit that claims 50w x 4, draws about 10-12 amps at max volume playing a song with pumping base. I have NO FREAKING IDEA, for your vehicle. What is the reasonable amp draw on a battery, when the key is in ACC, and the stereo is on, at say 1/3 of max volume? If 4 hours of stereo at 2 amps of draw caused a no start, then unless that 50 battery were otherwise discharged by other means, i would not have much faith in its remaining capacity, as depleting 8AH of its when new 50AH capacity (ignoring peukert) should still allow the engine to easily start. ![]() So if 4 hours of stereo listening caused a no start, it would be reasonable if the stereo was pulling 10 amps and the battery only had 50Ah capacity when new. ![]() ![]() The bigger the load, the less overall capacity the battery has to give, so states Peukert's law, and batteries will have different peukert numbers and these numbers will change for the worse as the battery ages, and as its capacity is also declining. This DOES NOT MEAN, a 100 AH battery can provide 100 amps for 1 hour though. IThe 77f/25c battery, earns that 100 amp hour capacity rating providing 5 amps for 20 hours before voltage falls to 10.5v, which is considered 100% discharged. Generally the biggest group 31 car jar/ automotive batterym which is 13 inches long, 9 inches tall, and 6.75 inches wide and weighs ~54 lbs and hopefully more, has about 100 Amp hours possibly as high as 130AH most car batteries are far smaller with an equal reduction in capacity. I mean if it is using 10 amps average, for 4 hours, that would be 40 amp hours. Do you have any idea how much amperage your stereo uses at the volume you listened to it at?
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