I have four batteries connected in parallel, I have seen diagrams showing where the output terminals are both coming off of the last battery and the parallel connection. I've also seen ones where the output terminals are on each ends of the entire battery. Which would be the correct terminals to use as output? Are there any benefits to either one?

Using opposite terminals Using opposite terminals

Using the same terminals enter image description here

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    \$\begingroup\$ Electrically they are the same. \$\endgroup\$ – mike65535 Sep 22 '20 at 18:19
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    \$\begingroup\$ No they are not. There first picture balances wire resistance between the battery stack. The second picture does not, the last battery has more wire resistance than the first battery. \$\endgroup\$ – Justme Sep 22 '20 at 18:37
  • \$\begingroup\$ So I'll basically have more current by using the end terminals of a single battery? \$\endgroup\$ – Couch Mango Sep 22 '20 at 18:44
  • \$\begingroup\$ Justme makes a good point, but no, you won't get more current. \$\endgroup\$ – mike65535 Sep 22 '20 at 18:59
  • \$\begingroup\$ Not really, it just makes one single battery to be the first one to provide current and get charged and that is the one wear out fastest because all other batteries are behind their own wires so they can't participate equally. By using the opposite terminals, there is equal wiring resistance to each battery so they all participate equally. Boat and RV electrical systems are designed like the first picture to keep all batteries healthy. \$\endgroup\$ – Justme Sep 22 '20 at 18:59

The proper way is the first way, where from the load, there is equal length of wiring to each battery, so the batteries have equal wiring resistance to load. This is a standard way to install boat and RV batteries in parallel.

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    \$\begingroup\$ Perhaps good practice for high current draws considering practical wire degradation issues with environmental/corrosion impacts. But for your run-of-the-mill AAA's - I'd surmise that it makes no difference. \$\endgroup\$ – Chris Knudsen Sep 22 '20 at 19:21
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    \$\begingroup\$ While I can see the reasoning behind the "opposite corners" connection, if the jumper cables between batteries are of reasonable size, and short, the voltage drop in the cables should be insignificant, so there should be no significant difference in performance for either connection method. I'd just connect things whichever way is most convenient. On my boat, I don't use either method - I have equal-length jumpers from each positive terminal to a common bus bar with all loads connected to the bus bar, and likewise for negative. \$\endgroup\$ – Peter Bennett Sep 22 '20 at 19:48
  • \$\begingroup\$ It is just the preferred method stated in many diagrams to achieve optimal performance. It is also how batteries "should" be connected by Australian accredited clean energy installers. So, if you don't already know about the subject and have to ask what is the best way, then this is the best answer. For more experienced people, this may not be the only answer. \$\endgroup\$ – Justme Sep 22 '20 at 20:08
  • \$\begingroup\$ I wonder if there are other practical reasons for diagonal connections. Perhaps to put the the utility connections far apart so wires/wrenches/watches are less likely to produce shorts during servicing? I have to admit that this geometry, at the very least, pleases my sense for symmetry. \$\endgroup\$ – Chris Knudsen Sep 22 '20 at 20:37

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