simulate this circuit – Schematic created using CircuitLab

I have 3 AGM 12v batteries in parallel. Between Battery 1 and 2 I have a BlueSea SI-ACR Automatic Charging Relay - 12/24V DC 120A; I also have an anderson pole connector (SB175) on the last battery3.

I want to hook up a battery charger to the system.

Should I be doing this @ battery1 acting as the alternator does; or Battery2 since the ACR has already cut power between 1-2 (woundn't this unbalance the charging) or on Battery 3 where I have the anderson pole connector (this is where Iwould prefer to connect the charger though Isuspect this will only balance 2-3 and not 1 since it is isolated with the ACR.

diagram https://1drv.ms/i/s!AmOoj1nayk49jcdVgFRUGvoiW9gjig

enter image description here

  • 4
    \$\begingroup\$ Draw. A. Schematic. \$\endgroup\$
    – winny
    Feb 7, 2018 at 19:19
  • 1
    \$\begingroup\$ Are the batteries in series, to make a 36 volt battery bank? If so, you need a 36 volt charger. Please show a schematic of your system - I can't figure out the connections from your description. \$\endgroup\$ Feb 7, 2018 at 19:19
  • \$\begingroup\$ Sorry my mistake the batteries are wired in parallel. + to + and - to - throughout. \$\endgroup\$
    – spreckoak
    Feb 7, 2018 at 19:27
  • \$\begingroup\$ 1drv.ms/i/s!AmOoj1nayk49jcdVgFRUGvoiW9gjig is a link to the diagram \$\endgroup\$
    – spreckoak
    Feb 7, 2018 at 19:32
  • \$\begingroup\$ Colorful, but gibberish. Use the built in schematic editor. Click on edit followed by the schematic symbol. \$\endgroup\$
    – winny
    Feb 7, 2018 at 21:28

1 Answer 1


If the batteries are connected in parallel, you can connect the charger to any battery, and they will all be charged.

  • \$\begingroup\$ I powered from the 1st battery. The concern for the 2nd/3rd is that these two batteries would charge but the automatic cutoff between 1 and 2 would prevent the flow back upstream, leading to the three batteries not being in balance. The 1st battery seemed to do the trick. \$\endgroup\$
    – spreckoak
    Feb 11, 2018 at 17:57

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