Off - 1 - Both - 2 switch

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mikebikeboy
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Joined: Mon Aug 09, 2021 10:13 am
Boat Type: Cape Dory 27

Off - 1 - Both - 2 switch

Post by mikebikeboy »

I have a Cape Dory 27 and I'm currently changing the house battery to Lithium, but keeping the AGM starting battery. I'm looking to change as little as possible about the current standard wiring configuration. My plan is to never combine the two batteries. I'll hardwire the alternator to only charge the AGM, and the AGM will charge the Lithium via a Victron DC-DC charger.

So my question is, if I quickly flip the old original "Off - 1 - Both - 2" switch between banks 1 and 2 (engine not running of course), it briefly will be in the "Both" position. As I do not want to combine these two different batteries I hope the millisecond of being in the "Both" position will not cause any issues. I don't think it will but just wondering if anyone knows something about that. Seems any big discharge between the banks, if one battery is low, would be so brief would not be long enough to heat up wires.

Another option would be to figure out a way to disable the "Both" position entirely in the switch, but not sure if that's possible.
CapnK
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Re: Off - 1 - Both - 2 switch

Post by CapnK »

I don't think that a momentary 'Both' would hurt, especially if both were at the same or near the same voltage.
My understanding is that the reason the two should be on separate circuits is mostly due to difference in charging regimes needed, due to different chemistry.

That said, I am not an electrician. :)

Changing the switch to this one (if it isn't already) would allow you to not have to pass thru the "Both" position when switching to 1 or 2. Because of that design, I think it would also be able to be modified easiest to remove Both as an option, should you choose that.

Keep us posted!

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mikebikeboy
Bottom Paint Application Technician
Posts: 22
Joined: Mon Aug 09, 2021 10:13 am
Boat Type: Cape Dory 27

Re: Off - 1 - Both - 2 switch

Post by mikebikeboy »

Thanks, that's very helpful. That switch would definitely ease my worries. But I may just go ahead and keep things as they are and see if any problems arise. somehow I don't think a millisecond of being connected could possibly be an issue but maybe I'm very wrong.
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