jza800 Posted September 23, 2014 Share Posted September 23, 2014 i have been having a battery problem for a while, so i did a charge test on it, i have now charged the battery, and when it have sit a while it stayes stady at about 12.6 to 12.8.. when i start the car and everthing is off, i can messure 14.1 to 14.3 volt at the batteri.. but if i turn everything on all the lights/radio/subwoffer/ac/heater it goes Down to 11.8 to 12.0 volts, but if i raise the rpm to 1200 - 1500 rpm, it goes to 13.8 volts whitin 30 to 45 sec.. but if i let i idle Again, the volts drop to 12v... Quote Link to comment Share on other sites More sharing options...
Mk4Gaz Posted September 23, 2014 Share Posted September 23, 2014 Sounds like the voltage regulator might be playing up? Quote Link to comment Share on other sites More sharing options...
jza800 Posted September 23, 2014 Author Share Posted September 23, 2014 but is the voltage regulator not in the alternator? because i have triede with another one, with same result... Quote Link to comment Share on other sites More sharing options...
Shane Posted September 23, 2014 Share Posted September 23, 2014 Sounds like the battery is either under rated for the application or shot and not capable of delivering the required current being asked of it. Quote Link to comment Share on other sites More sharing options...
jza800 Posted September 24, 2014 Author Share Posted September 24, 2014 I dont think it is a battery problem, it is on 70 amps. Quote Link to comment Share on other sites More sharing options...
Shane Posted September 24, 2014 Share Posted September 24, 2014 I dont think it is a battery problem, it is on 70 amps. What do you mean "It is on 70 amps"? If you want to eliminate it instantly from the equation, connect another known good battery in parallel with yours using thick jump leads, emphasis on the thick as it will make a difference at high loads. Quote Link to comment Share on other sites More sharing options...
jza800 Posted September 24, 2014 Author Share Posted September 24, 2014 (edited) The battery is not that old, it hold 12.6 to 12.8 when it has sit overnight, so the battwry should be fine, the battery has this SPEC 12v 70 ah and 640en Edited September 24, 2014 by jza800 (see edit history) Quote Link to comment Share on other sites More sharing options...
Shane Posted September 24, 2014 Share Posted September 24, 2014 The battery is not that old, it hold 12.6 to 12.8 when it has sit overnight, so the battwry should be fine, the battery has this SPEC 12v 70 ah and 640en I see. Your first post to me sounds a bit like this: You start your car and with minimal load on the alternator at low revs its fine, as soon as you load the supply at low revs the voltage drops at the battery because a) the alternator is not running fast enough to produce the current being asked of it and b) your battery doesn't have the current capacity you need in reserve at no or low revs. As you will know from ohms law voltage and current are proportional. You then wind up the revs and the alternator is creating bags of current and makes up the shortfall from the battery. I haven't done the maths but I presume you have totaled what the current draw would be with all the AC, sub, lights switched on have you? It could well be close to to what the battery can provide, don't forget that the 70Ah rating will be in the right conditions. If the battery has a high internal resistance then your current rating stated on the side of the battery is now meaningless. Quote Link to comment Share on other sites More sharing options...
jza800 Posted September 24, 2014 Author Share Posted September 24, 2014 yes, with everthing on it never goes under 11.5 volt when the car idle, if you hold it, lets say 1500 rpm, the voltage raise to 13.8 volts and not higher than that, and if you let i idle Again it drops to 12v.. but as soon i turn everthing off, the voltage raises to 14.2 - 14.3volts at idle Again... but another ?, if i take the positive and the negative off the battery, when the car is on, the car can hold idle with everthing else off, but do i turn on the light, the car dies, sholuld the alternator not produce enough power so the car not goes out??? or am i wrong... Quote Link to comment Share on other sites More sharing options...
jza800 Posted September 25, 2014 Author Share Posted September 25, 2014 bump Quote Link to comment Share on other sites More sharing options...
Shane Posted September 25, 2014 Share Posted September 25, 2014 (edited) yes, with everthing on it never goes under 11.5 volt when the car idle, if you hold it, lets say 1500 rpm, the voltage raise to 13.8 volts and not higher than that, and if you let i idle Again it drops to 12v.. but as soon i turn everthing off, the voltage raises to 14.2 - 14.3volts at idle Again... but another ?, if i take the positive and the negative off the battery, when the car is on, the car can hold idle with everthing else off, but do i turn on the light, the car dies, sholuld the alternator not produce enough power so the car not goes out??? or am i wrong... What you have described to me just sounds like the battery, I don't think that you want to hear that. The fact that it rises to 14 volts after you have increased the revs is down the fact it has just had a boost from the alternator, I am thinking that this 14v level wouldn't last long. Disconnecting the battery while running isn't the best thing to do. I see what you are trying to prove, that the alternator is capable of running everything, but it's a sure way to kill your ecu. However, if you can run the headlights with the battery not connected I would say its putting out what it should, I wouldn't think it is up to running everything you quoted in your first post though. In fact I am sure that some models have a larger alternator than others to cater for heavier loads/car specs. Have a search as am sure I read that on here. One of the functions of your battery is as a reservoir for high current demands. Even then in some applications it's not enough, this is why some larger amps have big electrolytic capacacitors strapped across their supply rails to provide the high current demands when wound up. Edited September 26, 2014 by Shane (see edit history) Quote Link to comment Share on other sites More sharing options...
jza800 Posted September 25, 2014 Author Share Posted September 25, 2014 i can not turn on the light, if i do that, the car goes out right away, maybe because i run xennon light.. so what you are saying is that my battery is not working correct anymore, and i have to buy another one??? if yes,what should the spec be on the battery??? Quote Link to comment Share on other sites More sharing options...
machman Posted September 26, 2014 Share Posted September 26, 2014 The thing you should be concerned about is how many Amps all your systems are drawing, sound systems draw lots of Amps (currant/power) particularly when cranked up! The alternator supplies the power so when you demand more power it puts load on the engine hence the tick over goes up because the ECU compensates so the engine doesn't stall. The battery is there to store electricity and stabilise the power supply. You will have to install a bigger alternator if you are drawing more than the standard alternator can supply ! Quote Link to comment Share on other sites More sharing options...
Shane Posted September 26, 2014 Share Posted September 26, 2014 i can not turn on the light, if i do that, the car goes out right away, maybe because i run xennon light.. so what you are saying is that my battery is not working correct anymore, and i have to buy another one??? if yes,what should the spec be on the battery??? I wouldn't just right the battery off, I would buy, beg steal a set of really thick jump leads (not the crap you see in most garages and cheapie shops made from bell wire) and try connecting another battery to yours in parallel, that will tell you a lot. Be careful doing this though as I have killed a Supra ECU in the past from spiking the supply. As for the spec on the battery, you really need to do some basic calcs/research. The thing you should be concerned about is how many Amps all your systems are drawing, sound systems draw lots of Amps (currant/power) particularly when cranked up! The alternator supplies the power so when you demand more power it puts load on the engine hence the tick over goes up because the ECU compensates so the engine doesn't stall. The battery is there to store electricity and stabilise the power supply. You will have to install a bigger alternator if you are drawing more than the standard alternator can supply ! Yes this, and hence why I said this : I haven't done the maths but I presume you have totalled what the current draw would be with all the AC, sub, lights switched on have you? It could well be close to to what the battery can provide, don't forget that the 70Ah rating will be in the right conditions. If the battery has a high internal resistance then your current rating stated on the side of the battery is now meaningless. Quote Link to comment Share on other sites More sharing options...
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