Battery charger with 1-2-both switch

webcraft

webcraft

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I plan to leave our new boat in a marina for extended periods plugged into shore power. Domestic bank will be 2x110AH and there will be a separate engine start battery. The two 'banks' will be wired into a 1-2-both switch (no, don't tell me not to . . . )

There will be shore power sockets, so batteries will really only need to be kept topped up ready for the occasional voyage.

My thinking is to leave the batteries switched to 'both' and use a 15A charger permanently plugged/wired in. Any problems with this? (Bearing in mind I am an electrical numpty).

- W
 
Although not an electrical numpty I do like primitive simple solutions where possible so like.a 1:2:both switch on the boat I sail solo.

I prefer to leave batteries fully charged and disconnected to everything so they only self discharge very slowly (I often leave them 5 months over the winter and batteries last 10 years or more). Once there is any connections at all then you need a charger eventually and I personally wouldn't use the both switch for long periods - here is where an expensive charger, VSR etc will keep things healthy.
 
Ideally you'd charge the house battery first, then switch to both and let the charger 'float' them all together.
But as you will only 'occasionally' be connecting the nearly fully charged engine battery to the house battery while it's still bulk charging, I don't think you will shorten its life significantly.
You want to be sure:
*The charger does not get switched off, disconnected, need resetting after a short power outage etc etc (but if it does, the batteries will only slowly go flat together)
*The charger drops to a float voltage acceptable to all the batteries.
*All batteries are in good health. If one goes short on one cell for instance, it will drag the others down.
*The charger will shut down in the event of a battery fault like a short cell. Basically a reputable charger which is intended for long term unattended operation.

Edit. Not disagreeing with RupertW
 
Presumably your starter battery is a lot lower capacity than 220Ah. You're going to subject it to the same charging cycle as the 2 X 110Ah batteries. If you're happy with that fair enough.
 
Does your charger not have more than one output so that you can connect to both banks without having either connected to the boat's system?

That is how mine is wired (3 banks actually) and each is charged independently, although I never leave it on for more than a few hours because the self discharge on the AGMs is very low. Last time I had it on it fully charged all batteries overnight after being left for 3 months.
 
I use a Cetrek type charger ( a cheaper clone). This is hard-wired into the back of the 1-both-2 switch. When I think a bit of charging is necessary I point the switch at the one that needs charging and set the charger. I never put it on both. This has worked perfectly for ten years.
 
Simplest way to do it and a convenient connection point!

MoodySabre said:
I use a Cetrek type charger ( a cheaper clone). This is hard-wired into the back of the 1-both-2 switch. When I think a bit of charging is necessary I point the switch at the one that needs charging and set the charger. I never put it on both. This has worked perfectly for ten years.
Click to expand...
 
If it were me, I would fully charge the batteries and disconnect them from any load before leaving the boat. On return, maybe many months later reconnect and charge up before use. Shouldn't take too long to bring them up to charge.

However, if you are going to keep an electric bilge pump as a safety net (although how long it will actually keep the boat afloat for....) ignore my suggestion.

Donald
 
MoodySabre said:
I use a Cetrek type charger ( a cheaper clone). This is hard-wired into the back of the 1-both-2 switch. When I think a bit of charging is necessary I point the switch at the one that needs charging and set the charger. I never put it on both. This has worked perfectly for ten years.
Click to expand...

Yes, me too - different charger, but otherwise the same set-up. Usually, when on the berth it's pointed at the domestic bank as the engine start battery is re-charged by motoring in, but it can charge the latter if necessary. Simple, logical and effective (like the 1-2-B-0 switch IMO).
 
webcraft said:
.
I plan to leave our new boat in a marina for extended periods plugged into shore power. Domestic bank will be 2x110AH and there will be a separate engine start battery. The two 'banks' will be wired into a 1-2-both switch (no, don't tell me not to . . . )

There will be shore power sockets, so batteries will really only need to be kept topped up ready for the occasional voyage.

My thinking is to leave the batteries switched to 'both' and use a 15A charger permanently plugged/wired in. Any problems with this? (Bearing in mind I am an electrical numpty).

- W
Click to expand...

Leave the boat with the 1-2-B switch in the off position. If you leave it set to both and a battery fails you could arrive at a boat with all flat batteries. Connect the charger directly to the batteries, either at the battery or at the battery connections to the 1-2-B switch.

If you want the engine battery charged as well, fit a two output model.

If you want to be able to run your electrical equipment in the marina, without depleting the batteries, fit a charger that will operate in "power supply" mode, that has enough output for all of your loads.

Take a look at Victron chargers.
 
Forget the charger. You don't want mains connected whilst away for an extended period.

Get a small solar panel - 10W should be enough to keep the batteries from going soggy.

Leave the switch 1-2-B 'off' (I don't like leaving my boat for extended periods of time with the electrics connected).

Connect the solar panel directly to the two batteries using a link wire between them - effectively paralleling them. I do this over the winter; works fine.
 
Minchsailor said:
Forget the charger. You don't want mains connected whilst away for an extended period.

Get a small solar panel - 10W should be enough to keep the batteries from going soggy.

Leave the switch 1-2-B 'off' (I don't like leaving my boat for extended periods of time with the electrics connected).

Connect the solar panel directly to the two batteries using a link wire between them - effectively paralleling them. I do this over the winter; works fine.
Click to expand...

Works fine until one battery fails and you arrive to all flat batteries.

I hope you have fused the link wire at both ends ?

A battery charger will not only keep the batteries charged whilst you are away, it gives you plenty of power whilst you're in the marina. But, if you don't want a mains charger and you want to rely on solar to keep them topped up whilst away (nothing wrong with doing that), buy a pair of 10w panels and connect one to each battery/bank.
 
Something to consider. Lead acid battery self discharge is, at a first approximation, about 5% per month. It's actually exponential so the discharge will actually reduce with time. So you might lose 10% in the first month but less than 5% on a battery at half charge if that makes sense.
 
As previously suggested; do not leave your boat connected to mains when you are absent for extended periods.
If your batteries cannot retain a good charge for several weeks when isolated then they probably need replacing.
Connect to mains and turn on on a good quality charger when you return to the boat.
An alternative is wind or solar charging.
 
I used to leave the batteries on charge for extended periods but horror stories on here of batteries being fried by defective chargers and practically catching fire made me rethink. Now I never leave the batteries on charge when we're away for long periods and according to the Smartguage they lose charge at 3-4% per month. No problem at all!
 
The problem comes when you leave a boat after a weekend trip and the batteries are low.
You don't want to leave them in that state for a fortnight, or wait 12hours for them to be fully charged.
I can understand why some people fit a high quality automatic charger for this circumstance.
 
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