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Old 09-08-2015, 14:49   #16
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Re: Battery issues

If a decent battery charger has been installed, then there should be a charging link to both battery banks. Same with alternator.
On the B 473, the battery charger was connected to both engine and house banks. The alternator charged both banks via a diode splitter.

The problem is with linking both banks through the positive switches is that if the house bank is bad, that bank will drag down the engine start battery if you have no charge source connected i.e. when sailing.

I found this out on the first night of owner ship, in January, a mile of Dover, in a Force 8. All the lights dimmed, chart plotter and AP shut down, and I could not start the engine.

Fortunately, the previous owner had installed a bow thruster, and I was able to drag a BT battery from out under the V berth, and connect it to the engine starter.

Since then, I have taken a very keen interest in battery systems

Edit to add: The link will be between the two switches.

Like someone else said, Nigel Calders book is an excellent source of information. If you are getting a hydrometer, get a decent digital multi meter as well, that really helps.
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Old 09-08-2015, 14:57   #17
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Re: Battery issues

thanks again Nigel - will take a look next weekend and see what I can find out...
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Old 09-08-2015, 15:19   #18
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Re: Battery issues

I have been through many banks of battery's in past years.... Fridges and electric toilets flatten battery's real quick.

If you don't have the correct charging systems solar/wind while off shore power your battery's will suffer and there life span will shorten.

Most deep cycle battery's only carry a 12 month warranty and most deep cycle battery's on my vessel die after around 2 years.

A battery shop can do a load test on your battery's and I think you will find they will need replacing.

You can also load test them yourself by loading them up with all your power whilst in the marina and time how long it takes till below 12 volt.

I use Catapiller 100amp deep cycles they are around $190 each and I believe one of the best on the market.

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Old 09-08-2015, 15:23   #19
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Re: Battery issues

P.s The problem with a hydrometer is that if your battery's are charged from your battery charger it will show good charged readings. The best way to test them is with a load testing.


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Old 09-08-2015, 15:29   #20
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Re: Battery issues

you need a battery monitor like a vitron 700. to monitor the batteries. you have probably been droping below %50 and that has killed your batteries in only a few years.


you've probably already killed these ones. but it'll help you maintain the next ones.


140ah is pretty small. if you are drawing 6-9 amps all day long. you probably either need bigger batteries, solar, or run the engine more often while sailing.



you only have 70ah usable battery. which would be 10amps for 7 hours with a brand new battery. or 7 amps for 10 hours. at which point you must be running the engine or plugging in. since you are only getting 3 hours sounds like your batteries are down to ~30% capcity


around here an avg battery size for a 34' sailboat is 4 golfcarts or about 440ah. 3x what you have. boats should be able to go for 2-3 days on batteries. which woulld about right on yours.
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Old 09-08-2015, 15:31   #21
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Re: Battery issues

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Originally Posted by southace View Post
I have been through many banks of battery's in past years.... Fridges and electric toilets flatten battery's real quick.

If you don't have the correct charging systems solar/wind while off shore power your battery's will suffer and there life span will shorten.

Most deep cycle battery's only carry a 12 month warranty and most deep cycle battery's on my vessel die after around 2 years.

A battery shop can do a load test on your battery's and I think you will find they will need replacing.

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Actually most batteries are murdered at around two years. A good quality deep cycle battery well looked after will last far longer than 2 years.

Further to the link I provided above there is lots of excellent information on Maine Sail's site.
Compass Marine How To Articles Photo Gallery by Compass Marine How To at pbase.com
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Old 09-08-2015, 15:39   #22
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Re: Battery issues

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Most deep cycle battery's only carry a 12 month warranty and most deep cycle battery's on my vessel die after around 2 years.
Trojan lead acid golf carts last about 10 years. sounds like you are murdering your batteries.
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Old 09-08-2015, 15:45   #23
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Re: Battery issues

Yes I agree murdered by fridges, toilets and water pressure pumps.

Basically I believe the amount of charge you take out of your battery should be replaced with the equal amount of charge that goes back into the battery.......that is the only way you will get 10years.


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Old 09-08-2015, 18:07   #24
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Re: Battery issues

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Basically I believe the amount of charge you take out of your battery should be replaced with the equal amount of charge that goes back into the battery.......that is the only way you will get 10years.
There is far more to it than that though.

There are many types of batteries. The common types are gel and water lead acid. After that there are sealed lead acid and regular "water" lead acid. The voltages used to charge them are different.

However equally important is how the plates are made. A plain old car battery has many very thin lead plates with high surface area. The high surface area provides a lot of area for the process of creating current and is used for STARTING an engine, which takes a MASSIVE current draw for a very short time (usually a few seconds).

A "Marine" battery is often used to start outboards and thus also needs SOME thin plates to provide that high current for the short time the engine is starting, however it also has some thicker plates.

A "golf cart" or "true deep discharge" battery has a few very thick plates. Furthermore to that point, when you use 6V deep discharge batteries, the entire amount of lead is used for only half as many cells (6 v instead of 12 v) and thus you get even more lead per cell, more thicker plates.

This matters because the lead plates are literally eaten away over time. Thin lead plates are consumed faster than thick lead plates. Car batteries will simply die, VERY quickly, if used as a "deep discharge" battery. Marine batteries will last longer, but nowhere as long as the true deep discharge batteries.

So starting batteries are designed to provide a huge current for just a few seconds, but NO long term current draw. Marine batteries are designed to provide a huge current for a short time but still provide a medium current for a long period. But they are a compromised design as a result.

So a house battery is best server by pairs of 6V "golf cart" batteries, DESIGNED specifically to provide a medium amount of current for long periods.

IN ANY case, you should never draw more than 50% of your current before recharge, and you should absolutely NEVER leave a battery in a partially discharged state for long periods of time, and you should absolutely NEVER EVER leave a battery low on water, as the part of the plates exposed to air will very quickly be permanently damaged.

They actually make a little device that measures the current out and in to a battery. They use these typically for solar systems so that you can know with some certainty what the "charge level" of a battery (or bank) is. IOW you drew X out and put Y back in, the charge state is Orig - X + Y.

BTW. trying to determine the true charge state by reading the voltage is not very accurate, or at least is difficult. After charging, the voltage remains artificially high, and requires a small current draw for a half hour or so, OR you must allow the battery to sit without charging or being used (no current in or out), for about 24 hours to really be able to use the voltage as a reliable indicator.

My point is that "replacing the charge" isn't as simple as it sounds. You could use 1/2 of the current (theoretically OK for deep discharge batteries only), leave the boat for a month and then put that 1/2 charge back in. You have "replaced the charge", but would likely severely damage the battery in the process.

And finally, a battery will "self discharge" over time. So you can damage a battery simply by leaving the battery in storage for 6 months without a smart charger on it.

Believe it or not, You can also damage a battery by over charging it, which is why smart chargers were invented. They are designed to put out a "bulk charge" voltage (14.5 V for open lead acid) and MEASURE the current into the battery. A fully charged battery will not accept much current. The smart charger figures out the charge state by the current that can be "forced" into the battery at the bulk charge state and then either leaves the battery to bulk charge (if very discharged) or cuts the voltage back to a lower voltage to top off, or to trickle charge the battery. All the while monitoring the current going in so that it can decide when to adjust the charge voltage (up or down) to correctly charge and maintain the battery.

Perhaps more than most people want to know, but we need to know this stuff if we don't want to buy new batteries every three years (or less).
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Old 09-08-2015, 18:36   #25
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Re: Battery issues

Hello,

Not a silly question at all! I think that you are getting some good information here and I second the opinion that you really should increase the size of your battery bank..preferably a lot! There are a lot of different kinds of batteries and solutions out there. I personally have had really great luck with the German built Prevailer gel batteries. The house 8-D in my own boat is over 15 years old now and the last time I checked the capacity it was still within 5% of stock. I do take care of it to an extent but it has been discharged to the 50% level many many times and recharged. The acid can't leak out of these batteries even if you drill a hole right through the case…which my Dad did by accident. (grin) He just put some caulking over the hole and the battery is still alive 5 years later. Battery acid when it gets out is really nasty stuff, I have repaired a lot of damage on boats from both regular wet cell lead acid and even one case of AGM's leaking. I am not a battery expert, these are just my opinions from working on and owning boats over the years. Best of luck to you.

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Originally Posted by Peterangell View Post
Hi there, this is my first post... I have a problem with my batteries on my Beneteau Oceanis 34 which is 3 years old and hope someone can help (probably very simple...)

I have 3 batteries, 1 for starting the engine which I don't have a problem with. The other 2 are for the other systems on the boat, and I keep these on trickle charge whilst on the pontoon - they show 14v or thereabouts when on charge, and drop to about 12.9v once off the charger.

No problem when I am out for a couple of hours, but when I am on a long passage, say 10 hours or so, then the battery alarm goes off after about 3 or so hours, and shows about 10.9v on the display - I then run the engine for half an hour or so, it goes back up to 12.9v, and then they are fine for maybe another hour until the alarm is coming on again....

The display is showing that I am usually drawing about 6 to 9A whilst sailing (with the Fridge, radio, autopilot etc.), although in rough weather I have seen that undulate momentarily up to about 28A with the autopilot on.

The 2 batteries are 70Ah each - I am wondering if they are basically dead and need to replaced or should I revive them somehow... they have lasted 3 years and have been on trickle charge all that time - was this the problem?

Thanks for your help, sorry if I this is a silly question...
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Old 14-08-2015, 14:07   #26
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Re: Battery issues

Ok I have managed to get to the boat, I have 3 batteries which are exide excel EB705 - they are ones you can add water to and the level was quite low so I have topped them all up. They are now charging and they initially showed 12.9v after a week of sitting here not being charged, and then went to 14.2v when I put the charger on, after 10 mins they have dropped to 13.7v (still being charged). I will leave them on overnight and hope that having topped them up with about 1.5 litres between the 3 batteries that I get longer than 3 hours out of them tomorrow....


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Old 14-08-2015, 16:23   #27
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Re: Battery issues

Keeping the batteries topped off, using good quality deep cycle batteries and all the other suggestions are excellent. One other item I don't believe I've seen mentioned is the wiring. Are the battery terminals corroded, all the connections tight? It takes a surprisingly small amount of resistance in the circuit to eat up amps.

As suggested by others, a decent book on DC electrics is an excellent choice. Additionally I believe a multimeter is an essential piece of ships gear. I carry three, one of which is the clamp type ampmeter.

With fully charged batteries disconnect charger power, turn off everything using power, wait about half an hour, measure current draw from the house bank. I believe it should be zero or very low. If it shows say an amp or more, you have a power thief somewhere on board. The fun part will be finding it.

It's been a long time since I've had this problem, feel free to correct any errors in this post. Right now I have a nominal 400 amp house bank. On a good day after a long shore power charge that gives me roughly 200 usable amps. I've also changed out virtually every light on board to LED. Sips just a tiny bit of power and no extra heat generated in cabin.

Good luck, this is part of the learning process that we all go through.

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Old 14-08-2015, 17:10   #28
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Re: Battery issues

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Ok I have managed to get to the boat, I have 3 batteries which are exide excel EB705 - t
Those are not "deep cycle" batteries, which is what you need for your house bank. Those are standard car batteries. They are useless for a boat that will spend nights (or even a day) away from shorepower.

I believe you are are already convinced that you need a bigger (in Ah) house bank. Add to that the right *type* of battery (deep cycle vs engine-start battery) .

You can take as a reference the house battery setup for Sunsail/Moorings´s smallest boats in the Caribbean (33 or so ft), which have a single 4D-size Lifeline AGM battery with rated capacity of 210Ah or so.

If I was in your position I would find out what sort of battery does Sunsail/Moorings use in a boat like yours. They are very clever in finding neat places to install large batteries.

You have not told us how you use the boat, if you can be a bit specific the forum can give you more tailored help.
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Old 15-08-2015, 02:40   #29
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Re: Battery issues

thanks again for all the help on this - I am convinced that I have the wrong type of battery plus also not enough Ah... I use my boat mainly for days ailing, but am building up to long passages and have done a few 12 hours plus crossing the channel etc... my aim is to take the boat down to the med in a few years time, (probably take about 3 weeks) but in the meantime want to sail to the channel islands etc probably next year which will be 18 hours, so will need more capacity... having bought the boat 3 years ago I now realise that I have neglected my batteries and am now grateful that I still get 3 hours out of them (perhaps more now that I have topped them up), but now is the time to invest so will be looking at a few options....
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Old 14-09-2015, 14:44   #30
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Quick discharge of service battery

Dear friend,
I have a Beneteau 373 since 4 years. I changed my batteries 4 years ago. I have one OPTIMA 75 Amp Yellow top battery for engine start and one 140 Amp battery for service. I have serious problem with my service battery. After disconnecting from shore power the service battery drop to 9 - 9,5 volts in 30 minutes.
When I start the engine it takes 30 - 40 min. to recover and the voltage arrive to 11 V then suddenly 13,5 V.
I checked the battery and they said it is OK.
Another problem is the anode. I changed it 4 months ago and it was totally finished laat week. I changed it again.
Do you have any experience with similiar problems?
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