When would you switch to Battery 1?

[wristwister]

I've got the 2 battery setup on the Tartan, Battery 1 is the starting battery and 2 is the house battery. These are connected to the basic battery selector switch with Off, 1, 2 and Both.

It struck me the other day that I've never had the switch on 1. When starting the engine and under engine power, the switch is at Both. This puts full juice to the starter, and also uses the alternator to charge both batteries. When the engine is off and using juice for lights, instrumentation, whatever, I switch it to 2, so 1 is always fresh for engine starting.

When would someone want to have the switch in the 1 position? Why?

[DaveC]

When battery 2 goes dead. If you put it in both at this point then you drain battery one into battery 2, especially if battery 2 has a shorted cell or something, which reduces or eliminates the energy to start the motor.

I always start on one or the other and then only switch to both when the engine is running.

[jongleur]

Here's my answer:

1/BOTH/2/OFF Switches Thoughts & Musings | SailboatOwners.com Forums

[NewMoon]

Here's how we've done it, for 17 years and 6,500 engine hours:

We have a single main engine and two battery banks. No VSR/ACR, and no generator. One bank is "starting" type (high Cranking Amps, but low Amp Hour capacity). The other "House" bank is "deep cycle" type (modest Cranking Amps, but high Amp Hour capacity).

Everything in the boat, except for bilge pumps and propane sniffer, runs off whichever bank the main battery switch (1-BOTH-2-OFF) is connected to.

We stay switched to the House bank 99+ percent of the time. When we want to start our diesel, we switch to the Start bank. After the engine is started and we've retrieved anchor with the windlass (another high current draw), we stay switched to Start for maybe 10-15 minutes, so that the start bank gets well recharged.

Then we switch (through BOTH, not through OFF) back to House. After an hour or two with the engine running, the House bank is well recharged. We don't do any other switching, until the next time we need to start up. This is not too difficult to remember, so we haven't felt the need for the more automatic VSR/ACR.

We've never had dead batteries. We've had to use BOTH to start only occasionally, when the Start bank was beginning to get old, or maybe not recharged well enough.

[Oceandeep]

Richard,

You make a great point about being careful when you switch from Battery 1 to Battery 2. I've been told by an Electrician in the Boatyard that switching thru the Off position can cause an electrical surge that could blow out your regulator or other electronics .

[NewMoon]

Can indeed - did that once with engine running, and blew one of the alternator's diodes. Fortunately I carried spares.

[Chuck Hawley]

When I worked at West Marine, we had a lot of customers who would have a two battery system, but would still end up with one of the following problems:

1. Both batteries dead; can't start engine.
2. Damaged alternator.

I would argue that the primary problem is one of having to switch the battery switch at almost any time in the boat's existence. It's too easy to forget and leave the switch in the Both position, and too easy to turn it one click too far and leave the alternator open-circuited.

The answer, I believe, is to use a voltage controlled relay like the Blue Sea ACR (Automatic Charging Relay) or the variety of other products from BEP or Mastervolt that accomplish the same thing. High voltage? Batteries are paralleled. Low voltage? Batteries are isolated.

On a "simple" boat (one engine, two battery banks, no generator, etc.) this is best accomplished with the Dual Circuit battery switch, which allows the engine battery to be connected to the engine/starter, and the house battery to be connected to the house loads, but with no interconnection. Use the ACR to charge both banks when there is a charger (alternator, inverter/charger, solar, shorepower) in the circuit.

I know the purists will worry that you shouldn't charge batteries in parallel, but in the real world, on boats that are common in harbors around the U.S., this system really works.

Cheers, and smooth seas,

Chuck Hawley

[Cheechako]

When would someone want the switch in # 1 position?
Just to charge #1, or if you need the combined voltage from both banks for some reason.
Personally. I would start the engine on the house bank, let the initial 15-20 minutes of high amp charging go there and after maybe 1/2 hour or so then switch to all or just #1 for a bit to recharge the start battery.
As mentioned above there are cheap small devices that allow automatic charging of the starter battery without having to switch. Remembering to switch can sometimes lead to problems. Like: you forget to switch to All after anchoring etc. The fridge pulls both batteries flat overnight.

[hamburking]

I never change the battery switch with the engine running (charging)...ever! Argue all you like, but I won't be blowing any diodes. Its a simple rule to remember and follow.

I never switch to BOTH. The bad battery will drain the good. Both is just for the rare emergency when neither battery has enough juice to start the engine. My goal is to never get to that point.

I use one battery for everything, and keep the second fully charged as a backup, for when the first might be dead, short, or fail. Once in a while I'll use the second battery for a bit, then fully charge it, just to be sure its working too.

I constantly monitor the volts, both under load and under no load. That way I know what the volts should be, and I'll know when there's a problem before I get into trouble.

In general, the second (backup) battery lasts a year longer than the first. The last thing you want is both batteries ending their usable lives at the same time.

LED lights help...kids like to leave lights on all night. I almost never plug into shorepower, and I have no solar or wind power...the engine makes more than enough power for me.

[jongleur]

Originally Posted by NewMoon

Here's how we've done it, for 17 years and 6,500 engine hours:

We have a single main engine and two battery banks. No VSR/ACR, and no generator. One bank is "starting" type (high Cranking Amps, but low Amp Hour capacity). The other "House" bank is "deep cycle" type (modest Cranking Amps, but high Amp Hour capacity).

Everything in the boat, except for bilge pumps and propane sniffer, runs off whichever bank the main battery switch (1-BOTH-2-OFF) is connected to.

We stay switched to the House bank 99+ percent of the time. When we want to start our diesel, we switch to the Start bank. After the engine is started and we've retrieved anchor with the windlass (another high current draw), we stay switched to Start for maybe 10-15 minutes, so that the start bank gets well recharged.

Then we switch (through BOTH, not through OFF) back to House. After an hour or two with the engine running, the House bank is well recharged. We don't do any other switching, until the next time we need to start up. This is not too difficult to remember, so we haven't felt the need for the more automatic VSR/ACR.

We've never had dead batteries. We've had to use BOTH to start only occasionally, when the Start bank was beginning to get old, or maybe not recharged well enough.

There are still many "break before make"
switches out there. If you choose to do
this procedure all the time (I don't know
why you would), make sure your switch
is "make before break."

[Lokiyawl]

Lots of good points being discussed. As long as I am aboard and monitoring, I keep the battery switch in the Both position. It is possible to have a bad #1 and not know it if you don't use the battery. Though the batteries are combined I would still notice that there was something wrong with the #1 via the voltage drop, . It happened once in the past that I switched to my #1 to use as a backup and found that the battery had deteriorated to the point that it did not have enough remaining capacity to start the engine. Fortunately the house bank though down was plenty to start the engine. I do think that a system that forces you to test all batteries on a regular basis is a good idea. My engine battery is about 1/3 of the total capacity and batteries prefer not being discharged deeply, hence using all batteries should extend the life some. Now if I know that the house bank has been deeply discharged, I will start on the house bank and let it charge separately for a while before switching to both. I do this to reduce the alternator heating.
One other thing I might mention. It does not take a large Lithium battery to start a diesel. My engine battery went bad and I finished the season with just the house bank and a few charged 3S lithium poly batteries which I had tested to verify they would indeed start the engine. I really hope that the pricing of the Marine Lithium batteries drops, the capacity increase for the same weight is awesome.

James

Originally Posted by wristwister

I've got the 2 battery setup on the Tartan, Battery 1 is the starting battery and 2 is the house battery. These are connected to the basic battery selector switch with Off, 1, 2 and Both.

It struck me the other day that I've never had the switch on 1. When starting the engine and under engine power, the switch is at Both. This puts full juice to the starter, and also uses the alternator to charge both batteries. When the engine is off and using juice for lights, instrumentation, whatever, I switch it to 2, so 1 is always fresh for engine starting.

When would someone want to have the switch in the 1 position? Why?

[DaveC]

Originally Posted by DaveC

When battery 2 goes dead. If you put it in both at this point then you drain battery one into battery 2, especially if battery 2 has a shorted cell or something, which reduces or eliminates the energy to start the motor.

I always start on one or the other and then only switch to both when the engine is running.

To clarify, I don't leave it in both. I just only switch to both when the engine is running to charge both banks. I use battery 1 for a couple weeks, then use battery 2 for a couple weeks, just so they both get used. My boat is wired so everything runs off whichever battery is selected via the switch. The starter terminals I connect directly to the battery I'm using currently, bypassing the switch. Once I start the motor, I switch to both to give the dormant battery some charging as well. Before I stop the engine I switch back to the battery I'm currently using.

-Dave

[boeing1]

I have a two battery system, both batteries are the same group 27, I use battery one, for house on my first day of sailing , them I use battery two for house the next time I sail.
seems to work for me....

[Rustic Charm]

Originally Posted by NewMoon

Here's how we've done it, for 17 years and 6,500 engine hours:

We have a single main engine and two battery banks. No VSR/ACR, and no generator. One bank is "starting" type (high Cranking Amps, but low Amp Hour capacity). The other "House" bank is "deep cycle" type (modest Cranking Amps, but high Amp Hour capacity).

Everything in the boat, except for bilge pumps and propane sniffer, runs off whichever bank the main battery switch (1-BOTH-2-OFF) is connected to.

We stay switched to the House bank 99+ percent of the time. When we want to start our diesel, we switch to the Start bank. After the engine is started and we've retrieved anchor with the windlass (another high current draw), we stay switched to Start for maybe 10-15 minutes, so that the start bank gets well recharged.

Then we switch (through BOTH, not through OFF) back to House. After an hour or two with the engine running, the House bank is well recharged. We don't do any other switching, until the next time we need to start up. This is not too difficult to remember, so we haven't felt the need for the more automatic VSR/ACR.

We've never had dead batteries. We've had to use BOTH to start only occasionally, when the Start bank was beginning to get old, or maybe not recharged well enough.

this is basically my set up as well, with the exception that I've installed an ACR which takes care of the charging for the 'starter/reserve' battery without me having to leave the battery switch to the starter.

[Sunsetrider]

In my opinion of you don't use an ACR with an on-off switch you are just guessing as to the charging of the batteries and taking an unnecessary risk. The variety of opinions here on which position to use and when is an indication of the guesswork going on.