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| I run a 12 volt trolling motor. I have two batteries in the compartment. When one gets weak, I unhook it, and hook up the other one. I want to have two batteries in parallel.I have a Guest, two bank charger.Each bank hooked up to each battery.My question is. Can I run the two batteries in parallel, and still have each battery with a bank? I'm sorry for the details, but I know nothing about wiring. Thanks Doug |
| I disagree and here's why: having both batteries in parallel makes them, in effect, one battery. Hooking up two banks to this parallel set up is the same as hooking the outputs of two banks to one battery. The charger regulator in each bank will see the charging output from the other bank and both banks can not be depended upon to charge your batteries. To do this with a bank hooked to each battery and get successful charging is to install a small but suitably sized to carry the necessary current (50+ Amperes) knife switch in the jumper cable running between the positive posts of the two batteries. Open this knife switch in order to create two distinct batteries and then turn on your onboard charger. The two banks will now regulate and properly charge the two, independent at this point, batteries. Otherwise, hook just one bank to the two batteries connected in parallel without opening up the jumper connection. It will take longer but the regulators won't fight each other. I recently switched from a 36 V trolling motor to a 24 volt and switched to 31 series batteries in series. I have the wires from my unused bank just insulated and doing nothing, rather than try to double the charging rate.
Keep in mind that if you hook the two in parallel, you will not have a fresh reserve battery. Both batteries working together will be drawn down equally. These batteries you want to hook in parallel should also be same size (27 or 31 series, let's say) and of the same age. If you get a battery that develops an internal short it will run down the good battery as well. You might consider putting a permanent jumper between only the negative posts and investing in a selector switch which allows you to run either battery at a time or both together. My starting batteries are in this configuration and I have to select the switch to off when I want to turn on the two bank charger hooked to these.
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