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I have a system with a 12 V lead acid battery, a charger (plugged into the wall outlet), and an invertor, which generates AC power from the 12 V battery.

I am also using the following battery charge/discharge control unit to protect the lead acid battery:

https://www.amazon.com/EC-Buying-Discharge-Discharging-Protection/dp/B0C73DXJF7/ref=sr_1_2?crid=11M56WIWTLTHT&dib=eyJ2IjoiMSJ9.BQM0ULvUaSbHeK2WwVhnKEMLw9TOUIPfxJbm-dlb8dcA73Qy5rh7eJFE3CRhsPF-.rvRzWw2UFdwGj98t1SegwTWyfryKbSa3gGiCxERMZm0&dib_tag=se&keywords=XY-CD60&qid=1708249807&sprefix=xy-cd60%2Caps%2C229&sr=8-2

This is a useful device in that, while charging the battery, it provides overcharge protection, and while discharging the battery, it limits discharge to 50% of battery capacity, which is critical for battery life for lead acid technology.

The device operates in two modes: P1 charge and P2 discharge. Based on the mode, its Vin and Vout connections need to be configured as follows:

enter image description here

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With use of two DPDT rocker switches, I can configure the Vin and Vout connections to correspond to the two modes:

enter image description here

enter image description here

However, in the solution above, I need to manually/simultaneously press the two DPDT rocker switches correctly, which is not ideal. If one of the switches was not thrown correctly, the configuration would not make sense. (For example, both DPDT 1 annd DPDT 2 could be connected to the battery.)

I understand there could be a mechanical solution that moves the two DPDT switches lockstep (although I have not seen one during a rudimentary search).

My question: Other than such a mechanical solution, is there some other, possibly more elegant solution that would swap Vin and Vout among three entities, namely the battery, the charger and the invertor?

Thank you.

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There are four pole double throw switches available, but they may not be avialble with the current rating you require.

You could use a single switch to control a 4PDT relay, or two DPDT relays, depending on your current requirements.

Since these things are only $10, perhaps you should use two of them, one for charge control, and one for discharge, then you won't need to do any switching.

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  • \$\begingroup\$ I agree about your idea of adding a second controller, I did think of it, but first wanted to ask here if there was any other way, for both frugality and to make sure I did my due diligence. I think that's the way I'll go. The two DPDT relays controlled by a switch is an excellent idea. I will pursue that as well in parallel, to be ready for a future implementation. Many thanks. \$\endgroup\$
    – Sabuncu
    Feb 19 at 5:33

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