Danny G Posted October 21, 2019 Share Posted October 21, 2019 My plan for the aux battery is to run my amp, sub, fog lights and eventually a run to the rear bumper for my trailer winch. This is something I do not understand, this isn't the first time I have seen this. If your batter is set up where the main and spare battery share a positive and negative connection that battery is wired directly in parallel and at that point it makes no difference where you tap to power what. It's the isolator that makes the difference in the diagrams and the reasoning. It allows the aux battery to be used without draining the main. Got it, that makes sense. If you have it isolated from the main to run like a house battery in a RV or whatever terminology applies lol. BUT this should not be a big deal if 1) your alternator is sufficient to charge both batteries, and 2) you have identical batteries in parallel. When you have batteries with different stats the stronger battery will attempt to charge the other battery to balance out the circuit. If the main is the powerhouse in this case then it will drain itself to charge the auxiliary. Link to comment Share on other sites More sharing options...
kramttocs Posted October 21, 2019 Author Share Posted October 21, 2019 Got it, that makes sense. If you have it isolated from the main to run like a house battery in a RV or whatever terminology applies lol. BUT this should not be a big deal if 1) your alternator is sufficient to charge both batteries, and 2) you have identical batteries in parallel. When you have batteries with different stats the stronger battery will attempt to charge the other battery to balance out the circuit. If the main is the powerhouse in this case then it will drain itself to charge the auxiliary. You are correct - if the truck is running. Gary has the use case(s) correct. It's when the truck isn't running that the isolator allows you to use the aux without worry. Because they will be joined shortly after the truck starts and ideally stay that way until the truck is killed, they will be a matched set to avoid the issue you mentioned. Link to comment Share on other sites More sharing options...
Danny G Posted October 21, 2019 Share Posted October 21, 2019 I think Scott is going to use a relay with electronics that senses battery voltages and won't parallel the two until one or the other gets to a preset value, showing it is getting charged. This makes sense to me if you are running a large draw with the key off to protect the main battery from getting too low to start the truck, but if the truck is running, with a sufficient amperage alternator it should keep the batteries charged enough to power all the auxiliary items without having the engine to rev up to compensate. Unless I am just that tired and missing something that requires me to look at a schem of what he is talking about to spark that "Ah-ha" moment. In the RV I had there was a battery isolation switch so when you were parked, engine off, the house battery was manually disconnected from the charge circuit. When you were up and running, you put the house batter back in the circuit and the alternator charged the main and house batteries, which is in essence what using a relay to put them in parallel would do automatically and for sure would be more ideal route to go if you planned on using batteries of differing capacities or with the engine of. That also makes sense why I was confused because like you quoted from my original post when I have seen people wire batteries directly in parallel then run a bunch of wires tapped of the (+) battery post trying to just drain that specific battery, which makes no sense. In that type of set up one would be better served taking a the same gauge wire as the positive to a fuse block then running an appropriately gauged wire to each device from the block. Link to comment Share on other sites More sharing options...
Danny G Posted October 21, 2019 Share Posted October 21, 2019 You are correct - if the truck is running. Gary has the use case(s) correct. It's when the truck isn't running that the isolator allows you to use the aux without worry. Because they will be joined shortly after the truck starts and ideally stay that way until the truck is killed, they will be a matched set to avoid the issue you mentioned. I'm tracking now lol. I was confused on the original intent. Link to comment Share on other sites More sharing options...
Danny G Posted October 21, 2019 Share Posted October 21, 2019 Steve 83 - "Solder is MUCH better than crimping in this application, for several reasons." If that is the case, then why don't the factories use soldered connections? If you really want to see something interesting, un-wrap and remove all the goo from a Detroit factory multi-wire splice, it's welded. Probably because hot/cold welded joints are more stable and less susceptible to heat. If you have a tin coated copper terminal or wire soldered to another tin coated wire you have copper, tin, silver or lead all in the joint and they all have different thermal and conductive properties contracting and expanding at different rates which can lead to failure. Second a weld like that can be done quickly with repeatable quality vs a solder joint. Speed with quality is a key driver in manufacturing. The solder we use has even been idiot proofed (raychem solder sleeves) you take your shields, or your ground wire and zap it with a IR gun it melts and you move on after you make sure the filet flows, there is no excessive tinning up the shield and the the sleeve isn't burnt. you cant over or under solder, make the shield/wire brittle by wicking too much up it etc. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted October 21, 2019 Share Posted October 21, 2019 I have worked in aviation/aerospace both military and for a major company in the industry. The wiring on those products goes through more vibration, intrinsic and extrinsic heat, rapid environmental changes, lightning strikes, corrosive fluid exposure (hydraulic, fuel, oil, coolants), and physical stress from flexing than any automotive or typical ground install. Sometimes all of the above at the same time, and they do it with crimps across the board. Your attention to detail and understanding of the matter really shows! The military certainly works in the most extreme environments. From the bottom of the sea to the top of the world, and beyond our atmosphere. (radiation in space is especially harsh) And EVERYTHING is mission critical! WAY back in the day my father used to design and prototype electronics for a bunch of military contractors and 'agencies'.... Norden, Raytheon, Sikorsky, Hamar, Perkin Elmer, NASA, you name it, easy of the Mississippi. Link to comment Share on other sites More sharing options...
Danny G Posted October 21, 2019 Share Posted October 21, 2019 You are correct - if the truck is running. Gary has the use case(s) correct. It's when the truck isn't running that the isolator allows you to use the aux without worry. Because they will be joined shortly after the truck starts and ideally stay that way until the truck is killed, they will be a matched set to avoid the issue you mentioned. Are you wiring your auxiliary items off the battery positive or the isolation relay. If wired like the schematic from Ford, that relay goes hot in accy/run connecting the aux in parallel whether the engine is running or not. I think this may been what Steve was hinting at with key off time. So basically if you stereo requires you to turn the key to accy, your not protecting the main battery. Looks like the aux was originally designed to run lights with the keys out of ignition. ***EDIT *** Added thought, It may actually be better to isolate the main battery while the key is in ACCY mode, then when the key is turned to run, juice that relay pulling the main back into the loop to start/run the engine. That way if you turn the key to ACCY you can run the stereo off the aux battery and protect the main from draining. Link to comment Share on other sites More sharing options...
Danny G Posted October 21, 2019 Share Posted October 21, 2019 I have worked in aviation/aerospace both military and for a major company in the industry. The wiring on those products goes through more vibration, intrinsic and extrinsic heat, rapid environmental changes, lightning strikes, corrosive fluid exposure (hydraulic, fuel, oil, coolants), and physical stress from flexing than any automotive or typical ground install. Sometimes all of the above at the same time, and they do it with crimps across the board. Your attention to detail and understanding of the matter really shows! The military certainly works in the most extreme environments. From the bottom of the sea to the top of the world, and beyond our atmosphere. (radiation in space is especially harsh) And EVERYTHING is mission critical! WAY back in the day my father used to design and prototype electronics for a bunch of military contractors and 'agencies'.... Norden, Raytheon, Sikorsky, Hamar, Perkin Elmer, NASA, you name it, easy of the Mississippi. That sounds like a pretty sweet gig. My goal is to move over to the space side of the house with my company, just waiting for the right opening. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted October 21, 2019 Share Posted October 21, 2019 I have worked in aviation/aerospace both military and for a major company in the industry. The wiring on those products goes through more vibration, intrinsic and extrinsic heat, rapid environmental changes, lightning strikes, corrosive fluid exposure (hydraulic, fuel, oil, coolants), and physical stress from flexing than any automotive or typical ground install. Sometimes all of the above at the same time, and they do it with crimps across the board. Your attention to detail and understanding of the matter really shows! The military certainly works in the most extreme environments. From the bottom of the sea to the top of the world, and beyond our atmosphere. (radiation in space is especially harsh) And EVERYTHING is mission critical! WAY back in the day my father used to design and prototype electronics for a bunch of military contractors and 'agencies'.... Norden, Raytheon, Sikorsky, Hamar, Perkin Elmer, NASA, you name it, easy of the Mississippi. That sounds like a pretty sweet gig. My goal is to move over to the space side of the house with my company, just waiting for the right opening. I wish you luck. There is certainly a lot of room to grow, and with cheaper access to space the growth looks exponential. Link to comment Share on other sites More sharing options...
Danny G Posted October 21, 2019 Share Posted October 21, 2019 I wish you luck. There is certainly a lot of room to grow, and with cheaper access to space the growth looks exponential. OK someone double check my work here on isolating the main vs the aux for wanting to run a stereo etc. If you use the "Run" part of the ingition to actuate the a relay connecting the main battery back into the power circuit, this means you can put the ignition in ACCY and run everything, with the engine off, from the auxiliary battery without risking the main battery. In the pictures below, putting this relay anywhere between splice S208 and the starter relay would accomplish this. Then you would take power from the "Run" signal either at S401 or S216 to the relay to bring the main battery back into the circuit. If you do this between splice S101 and the starter relay it would allow the auxiliary battery run lights as well while having the added bonus of allowing your ammeter/voltmeter to show drain/current voltage of the main battery. Even if your aux was on its last legs, in the "Start" position it is only responsible to activate the starter relay, the starting power to the starter would still come from the main battery. Heck while your at it you could whack out all these fuse links and install a fuse box. Link to comment Share on other sites More sharing options...
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