Alternating Battery Banks (Odd/Even, or?)

[Captain Kimo]

I have been using a different methocd of alternating two identical deep cycle batteries, charged through the now relatively standard three switch system using a voltgage sensitive relay.

I switch the batteries from house to starting duty each year.

Agree with Chip. While the alternate day (Odd/Even) has logic, for my situation with two WEST MARINE SeaVolt Dual-Purpose 12 V Batteries, I change the multi connection house wiring terminal fixture at the start of the season to the other Dual-Purpose battery. I try to forget what day of the week it is much less, if the day is odd or even,

Use two 5 Watt rated solar panels to keep them trickled charged up. Have Nano-pulsers on each to keep the plates from getting a build up of lead-sufate crystals on them and thereby get long life from them http://www.pulsegenetech.co.jp/en/what/index.html. Switch to both batteries after starting motor and warm up.

[Chip Hindes]

Since with the three switch system my batteries are essentially wired directly to the house and motor loads, I have to physically take mine out and move them to the other location. As well, my house battery is located forward and short wired directly to a high power inverter (through a high power fuse, of course) so just changing the wires to the switches wouldn't work either.

[Frank C]

... In mine and many situations the alternate arrangment will not work as they can drop below the desirable voltage quickly thus shortening their life, besides I have other things to do without fiddling with batteries, if I could remember. I would not think of going from dark to daylight with only one 90amp hour battery as by morning it could be well below the danger point even if fully charged unless of course we were on shore power.

WADR, the quoted problem violates a basic tenet of the alternating scheme ... as in, each battery bank must be able to support a single session's energy demands, or that bank is too small (i.e., the total capacity of each Bank is about 2x session demand). If combining a pair of batteries adequately provides for a single session's demand, then THE PAIR is required as a minimum bank, and TWO PAIRS is required for an Alternating scheme.

If it's impractical to fit duplicate "2-pair banks" you'll need to resort to a single large House Bank and a small Starter Bank as fail-safe for the motor.

This entire thread is based upon the premise that most Macs are carrying a Starter and House bank of similar capacity, and that capacity is ample for a daily session. In such case, the Starter bank is grossly over-sized for the cranking demands of our tiny motor. But, though over-sized for starting duty, it's ample as an alternate House bank. Therefore, you can better deploy your battery investment (in both weight & cost) to an alternating scheme, while also providing improved life-cycling of both batteries.