poorfish88 Posted September 27, 2014 Report Share Posted September 27, 2014 i would like to add another battery that can start my vehicle by itself and have it isolated from the system so its ALWAYS at 100% charge just in case i drain my front batteries or on those really cold days when its hard to start up. i currently have about 480A of stereo equipment and 2 group 49 batteries up front. what are our thoughts on isolating a 3rd battery in back for dedicated starting? If you keep them all together it's a lot better. Why isolater robs some voltage, 2, if you isolate the batts and if one gets really run down your punishing your alt. Alts are made to maintain a charge, not Charge a dead batt. The alt would work some OT. and it's life span will be shorter. Plus all your batts together are stronger than I single batt. Technically charging... WRONG big diff in maintain a charge and charging. I don't think you're using the right terms. When you start a car the battery voltage goes down, once the engine is running the alt will "charge" the batteries back up to a certain voltage and THEN "maintain" it there. It is still technically charging it. Think alt maintaining charge to (walking) an alt charging to (running). They don't charge at full power all the time. Link to comment Share on other sites More sharing options...
biscuitownz Posted September 27, 2014 Report Share Posted September 27, 2014 Think alt maintaining charge to (walking) an alt charging to (running). They don't charge at full power all the time. Any voltage higher than the current battery's voltage is considered charging it. Nonetheless it is still charging, whether it be slower or faster.. Link to comment Share on other sites More sharing options...
SLYentist Posted September 27, 2014 Report Share Posted September 27, 2014 The starter is likely pulling most of its current from the battery closest to it because of lowest resistance. To keep it to one system, just connect all the batteries in parallel (neg to neg, pos to pos ). The current will be distributed between all 3 unless you want to have two charging systems. With an isolator, you probably need to keep a charger on the rear battery. Cables and wires almost never fail; the terminations do. Link to comment Share on other sites More sharing options...
poorfish88 Posted September 27, 2014 Report Share Posted September 27, 2014 Think alt maintaining charge to (walking) an alt charging to (running). They don't charge at full power all the time. Any voltage higher than the current battery's voltage is considered charging it. Nonetheless it is still charging, whether it be slower or faster.. Your with me now. Would you rather run 10 miles. Or walk run 10 miles Link to comment Share on other sites More sharing options...
biscuitownz Posted September 27, 2014 Report Share Posted September 27, 2014 Think alt maintaining charge to (walking) an alt charging to (running). They don't charge at full power all the time. Any voltage higher than the current battery's voltage is considered charging it. Nonetheless it is still charging, whether it be slower or faster.. Your with me now. Would you rather run 10 miles. Or walk run 10 miles I'm done. Link to comment Share on other sites More sharing options...
ncc74656 Posted September 29, 2014 Author Report Share Posted September 29, 2014 it is not that i drain my batteries down regularly but if they are not at a high charge (+80%) its very hard to start the engine when its cold. so this is how it works, lets say its -15F and i go to start. it will take about 20 seconds or so before the wait to start light goes off, during this time the heater core is pulling 250-300A of current for the duration. after that i turn the key to start and the starter draws about 700A at this lower temperature and it will need to crank for up to 10 seconds before a start will occur. thus i am looking at buying a tractor battery from caterpillar (the 8D) to put in the back and have it dedicated to teh starter. currently i have both my front batteries going to a distro block and the starter connected to that block. so if i isolate a battery it will need to be a diode isolation so that the alternator can charge it but the amps or stereo cant pull from it, right? so that would mean that i would require an isolator that could block up to 700A or so of current to prevent the stereo pulling from it? is that how it works? nothing, gutted Link to comment Share on other sites More sharing options...
ncc74656 Posted September 30, 2014 Author Report Share Posted September 30, 2014 so for an isolator, it would need to include a diode to accomplish what i want right? if so that diode needs to be equal to or greater than the maximum draw the batteries might see right? nothing, gutted Link to comment Share on other sites More sharing options...
Kyblack76 Posted September 30, 2014 Report Share Posted September 30, 2014 SMD SUPER SELLER The Burban Build Blazer Build sold Acura trunk build sold Link to comment Share on other sites More sharing options...
ncc74656 Posted September 30, 2014 Author Report Share Posted September 30, 2014 please elaborate on the "fuck it im done" gif. thanks. nothing, gutted Link to comment Share on other sites More sharing options...
SLYentist Posted September 30, 2014 Report Share Posted September 30, 2014 heater core pulling 250-300amps? and 700 amps through a starter? Is your truck a big diesel? Cables and wires almost never fail; the terminations do. Link to comment Share on other sites More sharing options...
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