Electrical question

[BobA]

I know that it may seem obvious to some of you guys who have had a boat for a long time, but, to me, just starting out on the "Great Expense of boat ownership" I am unsure of how I can charge my batteries.

Explanation --- I have a starter battery ( I think it is 75amphrs) there isn't a lable on it) and I also have two 110amphrs for domestics.

At the moment I am removing the batteries to charge them individually but this does cause a bit of a problem when SHMBO has to sit waiting for me to set them up again before we can get out on the water not to mention the hassle of lugging them about - hence my previous post on shorepower.

This is all set up now but I am still unsure of how to charge all the batteries.

I was planning on connecting the battery charger to the domestic bank and leaving the 1-2-both switch in the BOTH position to allow the charger to charge both banks simultaneously.

Question 1 - would this work?
Question 2 - will it cause any problems with me leaving the boat"on charge" for up to 10 days at a time? - I often have to work away from home and cannot get to the boat.

I am using a Halfords Leisure charger which according to the "blurb" is ok to leave on for extended periods. But it does say that if you are unable to remove the batteries then you should disconnect the negative terminal. I would think that that would then stop the charging of the other two batteries and defeat the object.

Your suggestions would be appreciated.

Bob

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[Joe_Cole]

As a one off it should be OK, but from your post it sounds as if you are planning on doing this routinely. Are you not charging from the engine? Wouldn't this save all the messing around?

Joe


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[Stemar]

In the absence of anyone more expert, here's my 2 penny'th.

IMHO, Yes it should work, with the proviso that unequally discharged batteries won't charge equally, and you may find that the most charged bank discharges to the level of the least charged before they start to charge.

You'll also need to check the electrolyte level regularly in all the batteries, and you may find they don't last as long as if you had a more sophisticated charging system.

I assume you have an engine, which has some sort of charging system - alternator or dynastart, and that this charges - or tries to - the batteries via the one/two/both switch. I'd be tempted to rely on this to charge your engine battery. It'll probably keep it up to snuff, as long as you run the engine for at least 20 mins each time you start from cold. I'd then use the charger to charge the domestics, with an occasional top up for the engine battery if necessary.

On my Snapdragon I have a dynastart with, I think, about 9amps output into a single 110Amp hr battery. Getting out of the harbour means a half hour run, and I tend to motor sail to windward; in spite of the inadequate charging output, I had no problems last season, in spite of never having shore power and never taking the battery home.



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[BobA]

Yes the outboard has a 13amp regulated alternator which charges while it is running, would that be enough to keep the starter battery up to charge, if so then i would only need to connect the domestic bank directly and ignore the 1,2,both switch unless i wanted to top up the starter battery

My reading of what is being suggested

1 Engine charges starter battery when in use.
2 battery charger charges domestics with 1,2 both switch in OFF position
3 if needed to charge all batteries switch 1,2,both switch to both

??????????

Bob

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[Althorne]

IMHO what you have said in your last post is reasonably okay however charging 3 x batteries = 285AH seems a bit high to me and could overload your O/B alternator so check it's output first or you could have a very expensive repair on your hands. Details should be in maual or O/B dealer.

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[Joe_Cole]

Bob,

13 amp's isn't a lot but it should certainly keep your starter battery topped up with a bit bit left over for your domestic batteries. As always though it depends on how you are using your boat. How much of the time is the engine on? What are you running off the batteries? Do you use the boat overnight?

You've actually got quite a generous battery bank. It may even be worth considering getting rid of one of the batteries, but it does depend on what you are asking of it.

Joe

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[Sunnyseeker]

The outboard charger will be fine chucking out 13 Amps all day, as long as you dont short curcuit it then supplying to a battery bank the voltage regulates the supply of current up to 14.5 ish Volts, what you could look at is a split charge that prioritises the start batterry, when this is up to 14.5 then it will start charging the domestics.
I assume your running your mains charger on shore power? again this will be fine but generally speaking only chucking out 4-5 Amps? could have boost higher rates. the only thing to be carefull of is over charging I have found that some cheapish mains chargers will run up to 17 + volts with batterries bubbling away which will prematurely age them.
Are they sealed? if not get a hydrometer and then you wont over cook them.

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[TrueBlue]

Another two penn'orth.

The Halfords charger may well do a wobbly if asked to "see" both batteries at once, and as the engine battery will be recharged very quickly in use - provided that you don't have any other devices connected to it which you haven't mentioned, then you shouldn't need to top it up unless you leave the boat for extended periods.

However, your domestic batteries will need topping up - or even a really good charge. You might care to consider fitting an isolator switch and connecting the Halfords unit on the battery side of that.

As to some units not being very good quality, yo could get a digital volt meter and see what the charge voltage is both when topping up and when it gets to the end of the cycle - if you are prepared to wait that long. If it drops back to 14 volts or less then you are OK.

Any secondary (rechargeable) cell likes to be charged slowly, so taking a long time is not an issue. However, overcharging is and will kill a lead acid battery fairly quickly.

I use Alkaline cells (probably the only one that I am aware of), and they don't have any of these problems. haha.

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ICOS X: Stop what you're doing and wait my signal

 

[Birdseye]

Your problem is that the system is out of balance - you have too large a battery capacity for the outboard of a sailing boat to deal with. Its not just a matter of the capacity of the o/b, its also a matter of how long you want to run the engine, and the cost of long runs given the price of petrol. Like you would need to run the engine for something like 10 hours if you discharged the batteries only by half.

If the Halfords charger is OK to leave connected, it will most likely be OK for periods of 10 days. I use a similar system on my bike, and leave it on for months in the winter.

But none of this gets round the time wasting. To do that you need to do two things (three if you count changing over to an internal diesel engine). Firstly, you need to have a battery isolation switch which still leaves the batteries interconnected and the battery charger connected, but disconnects the other boat systems. This will allow you to leave the battery charger on, and still get away quickly. Second thing to do is to reduce your electricity demand and do away with at least one of the batteries. What are you running that you need so much battery capacity. Wont your O/B start with a cord? You have as much battery cap as I have on a 10m cruising catequipped for long distance with fridge, windlass, ssb, vhf etc etc. Try oil lamps.

<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[alahol2]

Just for info, I kept two 100Ah batteries charged with a Yam 9.9. We didn't overuse the engine (it was on a sailing yacht) but we were as frugal (miserly) with the electric as possible. No fridge, paraffin lamps when not reading etc.

<hr width=100% size=1>I really would rather be sailing...

 

[Wiggo]

Bob,

the Halfords charger is probably a recipe for cooked batteries in the long run, and the 1-2-both switch will prevent proper charging anyway.

IMHO, the minimum you can get away with is a splitter diode (about £30-40) and a proper three or four stage charger. Most chargers should have more than one output, so the engine battery gets one feed, and the domestics get the other. The charger can charge the banks independently, allowing the domestics to charge gently without boiling the engine battery. It is also designed to be left on for very extended periods (ours is only off when the boat is in use).

With a single alternator, connect the output to the input terminal of the diode block, and the outputs of that to each battery bank. That allows the alternator to charge each bank properly, too.

Finally, seriously consider fitting a Sterling or Adverc regulator - it can give you a huge increase in usable battery capacity.

<hr width=100% size=1><A target="_blank" HREF=http://homepage.ntlworld.com/graham.wignall/boats/eulimene600x800.jpg>The old and the new</A>

 

[halcyon]

Why go to all that cost and trouble.
Fit a bi-drectional split charge relay £50 / £60, ( no volt drop so you do not need the alternator regulator save £ 150 / £250 ), and fit a chargestat to the Halford charger £50 / £60, ( stops any overcharge, and turns the charger when not needed, no need for 3 stage charger, saving £ 200 / £300 )
Fit a Hella isolator as well as the selector switch and you have link start and fully auomatic charging .

Brian

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[Joe_Cole]

I think that we need to hear from Bob about what he is running from his batteries! It's quite possible that he's got quite a simple set up that only needs a bit of battery power; after all his engine is only capable of 12 amps. (Better than mine though; I only get 6 amps!).

What you are suggesting may well be over-engineering; we just don't know.

Joe

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[halcyon]

The reply was to Wiggo's response and Bob's worry about overcharging from his Halford battery charger.

Brian

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[Joe_Cole]

Sorry, I wasn't getting at you. Honest!

If Bob doesn't tell us more though we can't be much help to him.

Joe

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[halcyon]

OK I believe you.
All ways puzzels me why watever the problem, fit a smart alternator reg and 4 stage charger, must prove someones marketing is working.

Brian

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[Wiggo]

Not marketing, just personal experience. We may be atypical mobos in that we like to spend time away from marinas, and battery maintenance is important. We currently have just under 600Ah capacity...

The alternator regs really do make a huge difference.

<hr width=100% size=1><A target="_blank" HREF=http://homepage.ntlworld.com/graham.wignall/boats/eulimene600x800.jpg>The old and the new</A>

 

[BobA]

Hi Joe,

You ask what is running off the domestics - I suppose not alot really - a 600watt inverter (got to make a cup of tea and SWMBO thinks the gas kettle is a bit slow) - VHF (I think is a necessity) - lights, 12volt coolbox to keep the wine cool, Chart plotter (so she knows where we have been) and that is about it.

Bob

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[Joe_Cole]

Bob,

Odds are that you’ll get enough electrical power out of your engine to drive most of what you need (starting, VHF, lights and plotter). If you were just using those then you could probably be independent of external charging.

The real drain on resources is the inverter and cool box.

Your cool box is probably using around 6 amps (it should say on the label exactly how much). I.e. nearly half the electrical power coming from the engine at top speed. (Remember that the engine will only produce the full 13 amps at top speed. At lower revs it will churn out significantly less than 13 amps.)

The inverter will use even more. If your kettle is using the full 600watts (again the label will say) then your battery will theoretically be using 50amps (in practice it will be considerably more because of the inefficiencies of inverters). Granted the kettle is only on for a few minutes, but a few cups of tea during the day and you’ve used a lot of battery power. Incidentally, I’m surprised that you say that the electric kettle is quicker than gas; are you sure that you are heating the same amount of water? You may be filling the gas kettle more than the electric kettle. (It happens; I know we do). Personally I would do away with the electric kettle, if the gas is no good I would look at getting a better hob.

With your current set up you haven’t got much chance of being independent. I also think that you arguably have too much battery capacity; certainly your engine will never be able to keep all those batteries charged. Many people would operate a boat like yours with just one battery. It’s certainly better to have one or two batteries properly charged than three inadequately charged.

It’s easy enough to find another way of heating the water. Keeping the wine cool is another matter!

Mind you. If you have easy access to shore power you can forget all this. Just plug in at the end of the day!

I hope this helps. I just don’t envy you lugging those batteries around all the time!

Joe



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