Note:Even when set to OFF a bilge pump, propane sniffer, stereo memory or VHF may still be direct wired to the house bank so the vessel may still have live 12V wires. OFF = Both battery banks are isolated/OFF What Bank Selection and Charge Directing Mean:īank 1 = DC loads are drawn from bank #1 and alternator charging goes to bank #1īank 2 = DC loads are drawn from bank #2 and alternator charging goes to bank #2īOTH = DC loads are drawn from BOTH banks and alternator charging goes to BOTH banks This means what ever position you have the switch set to, is where your on-board energy comes from, and where the engines alternator sends its charge current.
The 1/2/B switch, as wired by most builders, becomes a Bank Selection and Charge Directing switch. Technically, and accurately speaking, you have Bank 1 & 2 and each of those positions do both house and starting duties simultaneously. As you read on you see more of what we mean by this. This is still actually incorrect terminology, but a bit more accurate. It is for this reason that we refer to the banks, with a 1/2/B as HOUSE and START/RESERVE. Starting and House services cannot be isolated from one another with a 1/2/B unless you add another ON/OFF switch.
In the #1 or #2 position each bank serves both starting and house purposes. it may feel like you have a START & HOUSE bank but you really don’t. If you wish to continually move the switch from 1 to 2 then 2 back to 1 etc. A “START” battery, by definition, is really dedicated to only starting an engine, no house loads. Sure, you can assign a switch position to HOUSE and START but they are really EVERYTHING banks. One of the most common misconceptions is that you have a Start Bank and House Bank. START & HOUSE Banks – Like anything in the marine market the 1/2/B can develop it’s own levels of myth & lore.
#Blue sea marine battery isolator install
Why? It’s really not necessarily due to the switch itself, but rather due to the way most builders install them, and the way many boat-owners have used them.ĭespite the bum rap, the 1/2/B switch remains a versatile & redundant single-switch battery selector. The switch, I believe, has gotten an undeserved bad rap over the years. Over the years most all boat builders, of both sail and power, have installed the simple and redundant 1/2/B switch. Please DO NOT connect DC neg to a 1/2/B switch!!ġ/2/B – A battery switch that has position 1, 2 OFF and a paralleling feature often called BOTH, COMBINE, ALL or 1+2Ĭ Post – The “C” Post is the COMMON post which is also referred to as FEEDER, COMMON or OUTPUTīoth – When the switch is set to 1 +2, BOTH, COMBINE or the ALL position both battery banks are now physically wired in PARALLELġ/2/B Switch a Very Common Factory Wiring Configuration: The 1/2/B is switching only the DC positive conductors and has nothing at all to do with DC negative. If I had a dime for every-time this question was asked, I’d not be writing this article. “But RC where does DC ground connect to on the 1/2/B?” A 1/2/B switch has just three terminals and four positions. One area of confusion we see fairly routinely is a boat-owner misidentifying the 1/2/B switches terminals. MHT Recommended Products Affiliate Disclaimerġ- Bank Isolation – The ability to isolate a battery bank from both loads and charge sources in the event of a bank or battery failure.Ģ- Cross-Connection Use – The ability to use either on-board battery bank as the sole use bank, meaning it serves as starting and house load bank in an emergency, This design criteria should always include #1.ģ- Ease of Use – A battery switching design is no good if the boat owner does not understand it. Many boat owners don’t have the luxury of starting from scratch and the existing switch can usually be re-used/re-purposed easier, and in a less costly way, than converting to an entirely new switch configuration. This article is only intended to showcase how the 1/2/BOTH switch can be used in an easier and often less confusing manner. Let me be clear on this point this is not our preferred method, it is simply a method.
Preface: I’ve seen & read many on the internet suggest that “The 1/2/BOTH is RC/Rod’s/Compass Marine’s preferred switching method”.
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