Switching battery banks with engine running - Page 4 - SailNet Community
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post #31 of 67 Old 09-29-2008
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The best systems i have seen have a group 24 or 27 starting battery and a compleatly indepedent house bank

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post #32 of 67 Old 09-29-2008
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Am I the only one who does not have a typical battery swich?
This subject comes up a lot and I was wondering if my system is any better or worse or what you guys think.

Our boat does not have a battery switch as it is commonly reffered to, we have (3) T-Handles mounted down in the aft berth. (1) for the Gound, (1) for Battery 1;starting, and (1) for Battery 2; House Bank. I have tried to find a photo but I don't have one and I can't find an example of the set up anywhere on line.

With the handle in the Vertical position the battery is off, and in the Horizontal position the Battery is on.

I always leave the House on and use that to start the engine, when I want to charge the starting batt I flip the lever to Horizontal. No problems and it seems a lot less confusing than the typical 1, 2, Both. I simply have to remember to NEVER switch off both batteries or to flip both the handles to the Vertical position when the engine is running.

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post #33 of 67 Old 09-29-2008 Thread Starter
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My problem is two fold. First I'm laboring under the belief (from an article I read long ago) that is not good to combine dissimilar batteries. Second, I use only the starter battery to start the engine....charge it for short while and then swithch to the house bank to keep it charged. If there is no problem in combining dissimalar batteries then I have no problem....just put the swith in BOTH and don't forget to take the starter battery out of the system when you shut down. I think we have settled the idea that it is ok to switch from 1 to BOTH to 2 as long as there is no disconnect. So that just leaves the theory of combining dissimillar batteries. Perhaps there is no dissimilarity between a "engine starter battery" and deep clycle house battery. Any thoughts on this?
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post #34 of 67 Old 09-29-2008
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HNS...the reference to TYPE of battery is not between deep cycle and starting. It refers to the chemistry...generally WET CELL (flooded), Gel Cell or AGM.
For example...if you need to add water to all batteries...you may safely charge them all using wet cell parameters and thus just leave the switch on BOTH.

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post #35 of 67 Old 09-29-2008
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Alex-
"was I lucky? or is my engine good?" Your engine is immaterial. The facts are that there are over 50 alternator designs in the general market, they are internally different with different electronics in the regulators.

A cheaper or older design can burn out in 15 seconds or less if the voltage SENSE lead is disconnected from the batteries, resulting in the alternator going to "battle speed" and staying there, i.e. 17+ volts output.

Note that I said "sense lead", not "primary output". You should be able to disconnect the primary output without any problem. Except, many boats tie the sense lead TO the output, in a variety of ways, because that's cheaper than tying the sense lead to each battery bank (which is proper engineering) and arranging to switch it as you switch the banks.

So, with all those alternator types complicated by all the kuldge wiring...there's no telling what is safe unless you can detail your installation AND your alternator construction. For the past 30-40 years, there have been alternators available with internal regulators that will safely shut down the output during a fault condition, instead of burning themselves out. The necessary "heroic" regulator chip is typically a one dollar part. That makes it totally unaffordable for many engine suppliers, who are bidding on contract for the cheapest parts.

Switching the battery banks while the engine/alternator is running? Perfectly safe IF everything was designed well, installed well, is working well. The only question is, does the prudent mariner rely on "IF" ? Using a battery combiner, or dual knife switches, instead of a rotary battery switch, takes out the "IF". As does getting the technical information on your alternator, directly from the maker.
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post #36 of 67 Old 09-29-2008
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Quote:
Originally Posted by sailingdog View Post
Most of the 1/2/both/off battery switches I've seen are rotary and can go from 1-both-2-off or 1-off-2-both... I prefer the Dual Circuit plus design, which reduces the problem, but you do need either a battery combiner or echo charger with it.
Coincidentally, most, no make that all, the switches I've had on my boats over the years are not rotary and look like this:


Maybe I've been lucky that the original owners chose wisely, maybe this is the one that is just commonly used in South Africa. But my present boat was built in the US and has one like the above as well.

The one that you're referring to obviously looks like this:



Like I said in my first post, if you have one like this, change it ASAP. Why would anyone choose this option? The instruction re the OFF position is clear enough on both switches but no doubt not many people have noticed that.


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post #37 of 67 Old 09-29-2008
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Don't know how to tell you, Andre, but both of those switches ARE ROTARY.

The only difference is that one turns 90 degrees per position and can go from "all" to either single battery, while the other one is more restricted about how it can switch, and moves maybe 15 degrees per click.

From the "STOP ENGINES" warning label on your switch, it would appear to be the most dangerous kind--the kind that does not "make before break". While the lower switch bears the same warning--that style of switch is available both ways, the larger range of motion allows "make before break" with larger contacts. A "make before break" type with auxiliary field disconnect contacts is the safest type.
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post #38 of 67 Old 09-29-2008
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Quote:
Originally Posted by SEMIJim View Post
Maybe I'm missing something obvious (it wouldn't be the first time), but why would you need to do this? By "this" I mean: Switch battery use while under way under motor?
Not saying the following is right or OK but what we do is.

Start engine on 1 (starting battery). If engine starts switch to All to change both batteries while motoring to channel.
Turn off engine and switch to 2 (House bank).
Before starting engine switch to 1 (starting battery)

This is old-school keeping one battery for starting and one for house but requires switching from 1 to All while running.

The only dangerous step is to remember to switch the battery after changing on all. If you leave it on all and run your GPS, Lights etc too much you could kill both batteries and not be able to start.

So to protect against this we keep a changed NAPA starting battery under a bunk just in case. It will start the engine we have tested it.

Last edited by davidpm; 09-29-2008 at 11:38 PM.
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post #39 of 67 Old 09-29-2008
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Hey Alex,

I remember that broken battery lead. I'm still amazed that nothing went bang as a result but there you go. With only two batteries, how long to you run you engine each day for charging ?

We have the standard rotary (as in rotates through 360° not just through a narrow arc which is I'm sure what Andre meant by non rotary). I've never managed to turn it through off when going from one battery to others or all but I like the limited rotation version.

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post #40 of 67 Old 09-29-2008
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Yes they are both rotary but I think the point Andre was trying to make is that the top one only rotates from off - 1 - all - 2 and back to the off position THE SAME WAY

The label says to stop engines before turning off, not turn off engine before switching....fine to switch between batteries while the engine is running


Quote:
Originally Posted by hellosailor View Post
Don't know how to tell you, Andre, but both of those switches ARE ROTARY.

The only difference is that one turns 90 degrees per position and can go from "all" to either single battery, while the other one is more restricted about how it can switch, and moves maybe 15 degrees per click.

From the "STOP ENGINES" warning label on your switch, it would appear to be the most dangerous kind--the kind that does not "make before break". While the lower switch bears the same warning--that style of switch is available both ways, the larger range of motion allows "make before break" with larger contacts. A "make before break" type with auxiliary field disconnect contacts is the safest type.

Last edited by GBurton; 09-29-2008 at 10:52 PM.
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