Two hot wires from alt vs. battery to battery

[sideways]

Have not seen this question in all my digging through posts.The reason I'm asking is the distance from my alt. to where the second battery would have to go is much shorter than it would be to connect the batteries. Just wondering if there is any been there done that blew that up advice out there.LOL

Questioned several different mech (some auto some alt shop) and from the elec system standpoint none could see a prob.. My line of thinking is that the pos to pos is still there,the length of wire will be shorter. thanks and 73's

[mopar2ya]

I would say that it depends on the use that the battery will see. If the load the battery will see will regularly be more than the alternator can provide, I would attach it battery to battery. I would run the heaviest gauge wire that I could reasonably run from both positive and negative on the original battery. If the alternator is sufficient to handle the load, then do whatever you want.

Mopar

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[Phyco_Radio_911]

The nice thing about dual alts is that if your out somewhere and your vehicle alt dies your not stranded, happen to me, just dug out a wire and connected the bats and to the shop i drove, sorry AAA not this time lol

[Seminoles]

Here is the problem when you start the car/truck the starter can draw up to 400 amps (bad connections, worn starter, and so forth) with two battery's not isolated the current will divide between the two the 8 or 10 gauge wire from the alternator will not handle this leading to a possible melt down of wires and alternator leading to fire and or a battery explosion. Now if one battery is used just for accessory's like radio and amp then you can run a wire from the alternator to the second battery using an isolator it will keep the current from drawing from the second battery though the alternator during starts or a relay wired to turn off when starting or just a simple discount switch just remember to turn it off when starting. But yes it can be done just be careful and smart/safe. Good luck.

[sideways]

I wasn't planning on a second alt(even though it would be nice), I just put in a 200 amp alt.. I was going to run a second 4ga. wire to the vech. battery and the radio would stay there also. The second battery would be for my amp., a TS 667 so I shouldn't have amperage issues if I have been reading all the posts correctly ( and yes Phyco I'm a beginner so be nice). In a pm from one of our sponsors I was told my original 105 amp alt. should have been enough ,but my alt. was going anyway so I upgraded. The sponsor also told me that in a battery to battery connection the second battery (s) would not receive a full charge or maybe it was not receive a full charge quickly.The disconnect would be cheaper than the isolator and the info about starting was helpful , hadn't thought about that. Thanks for the input guys still building and have all the wire and fans etc. priced and chomping at the bit to get-er-done. Thanks and 73's Steve

[Sheriff Bart]

if you're only using one alternator I would do it this way. The 10 ga. wire that's connected between the alternator and stock systems would remain in place. However I would add a heavier ga. wire at the alt. output to the second battery because your toys will have a higher amperage draw.

73's

[rev ike]

i used one alt. and two extra batts in the back of my e150 van i hooked a 4 ga wire from the alt to the two batts which were also joined with 4 ga wire worked great had no problems i was considering heavy duty circuit breakers in case of shorts to isolate system to prevent fires but i sold it

[sideways]

Thanks guys, since I want power in the back for "other" reasons also I have an isolator installed and waiting for final hook-up, based on the start up info, toys draw etc..... The final hook-up confusion point is a yellow wire the isolator came with that they want hooked to the S terminal in the alt. plug. and run to the battery#1. I believe it is for a different type alt. since the existing alt. does not use the S term in the alt plug. Bought both alt . and the isolator from the same place and will run her there on mon. prior to applying power for clarification on that %%$ yellow wire , then isn't so-long mudduckville,lol. Thanks again for all the help, 73's Steve