ncc74656 Posted September 26, 2014 Report Share Posted September 26, 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? nothing, gutted Link to comment Share on other sites More sharing options...
poorfish88 Posted September 26, 2014 Report Share Posted September 26, 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. Link to comment Share on other sites More sharing options...
biscuitownz Posted September 26, 2014 Report Share Posted September 26, 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... Link to comment Share on other sites More sharing options...
ncc74656 Posted September 26, 2014 Author Report Share Posted September 26, 2014 i want to have the rear battery isolated beacuse i do not want the stereo to pull any current from it. my front two batteries are more than enough to handle my stereo by them selves. the reason i want the rear batt isolated is it will not be an AGM. i was looking at buying a #D8 battery for the rear as i think it is the smallest battery i can use to crank with, any smaller and i would need 2 batteries back there. i want to ensure that regardless of what i do up front, i can always start up. I have a mechman 370 so im not worried about over driving the alt, i am concerned with the front batteries not always being at 100% when i shut the truck off. i do lots of short drives and massive electrical pulls with on board power, stereo , and such so if i have front batteries that are at 70% and go to start it the next morning when its -35F im worried i wont have hte power to crank. nothing, gutted Link to comment Share on other sites More sharing options...
poorfish88 Posted September 26, 2014 Report Share Posted September 26, 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. Link to comment Share on other sites More sharing options...
poorfish88 Posted September 26, 2014 Report Share Posted September 26, 2014 i want to have the rear battery isolated beacuse i do not want the stereo to pull any current from it. my front two batteries are more than enough to handle my stereo by them selves. the reason i want the rear batt isolated is it will not be an AGM. i was looking at buying a #D8 battery for the rear as i think it is the smallest battery i can use to crank with, any smaller and i would need 2 batteries back there. i want to ensure that regardless of what i do up front, i can always start up. I have a mechman 370 so im not worried about over driving the alt, i am concerned with the front batteries not always being at 100% when i shut the truck off. i do lots of short drives and massive electrical pulls with on board power, stereo , and such so if i have front batteries that are at 70% and go to start it the next morning when its -35F im worried i wont have hte power to crank. JESUS, don't mix AGM and SLA either. STOP. That Mech will fry a hell of a lot soon if you don't treat it right. It keeps the batts. topped off... Not charged from a dead or low state. Link to comment Share on other sites More sharing options...
poorfish88 Posted September 26, 2014 Report Share Posted September 26, 2014 Mixing the lower resting rate SLA with the high resting rate AGM will lower the life of your AGM batts. The SLA batts will keep draining the higher resting AGMS. Link to comment Share on other sites More sharing options...
ncc74656 Posted September 26, 2014 Author Report Share Posted September 26, 2014 if the batteries are isolated they will not be mixed, that is the exact reason im looking into isolation. i want power to only flow into the 8D in back to charge/maintain and then ONLY allow power to flow out when cranking. that is all it will be there for. i can not find any large AGM batteries to do what i want so the lead acid is my only route. i tried using a single group 31 diehard marine battery last year (agm) and it was not able to crank the engine over at around 12F. nothing, gutted Link to comment Share on other sites More sharing options...
poorfish88 Posted September 26, 2014 Report Share Posted September 26, 2014 if the batteries are isolated they will not be mixed, that is the exact reason im looking into isolation. i want power to only flow into the 8D in back to charge/maintain and then ONLY allow power to flow out when cranking. that is all it will be there for. i can not find any large AGM batteries to do what i want so the lead acid is my only route. i tried using a single group 31 diehard marine battery last year (agm) and it was not able to crank the engine over at around 12F. 100, right on the iso. My bad. But I'm a 100 percent about not using an iso at all. Alts maintain batts, not charge them up. I would'nt over and over dain my batts and have the alt charge them. They are made for toping off batts not to charge them. I'm trying to help you so you don't ruin your alt. How do you drain them so low? Running wince or something? Cause the Mech should maintain 480 amp dynamic draw just fine, while driving. Like when your driving your voltmeter show your droppin to what volts? Link to comment Share on other sites More sharing options...
biscuitownz 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. Link to comment Share on other sites More sharing options...
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