I bought a brand new battery last nov. At the time it ran just lights, sounder if I used it, socket to charge phone and stereo. It's a large deep cycle ( can't recall the ampeg as I lay in bed here rockin around)
All was fine until I added the fridge.i guess I get about 2 hours of fridge only use- as in using nothing else until the battery drops below 12. Now it seems that everything - even the things that weren't draining the battery - do drain it- like radio. Cabin lights. Socket charger. I know I need more batteries but I'm wondering what's more likely. Have I stuffed this battery or have I got a dud. I'll come to the boat after a week and the volt meters normal but after some usage it'll get pretty low- like below 10. I've been on the boat the last 7 nights and have had to run the engine every night to just charge my phone. It just doesn't seem to be holding a charge. I took it back to battery world about 6 weeks ago and they kept it for a week and charged it. The said that if I had anymore problems they would replace it. I don't know much about batteries obviously. Is it possible that the battery was a bit of a dud? Did the addition of the fridge just weaken it?keep in mind that I'd run the fridge for 30 min only. Just long enough to have a few coldies ready but now this isn't really possible. I can't even really use the fridge unless the engines running.

Mate it depends on what type of battery it is and how old it is. If it is from Battery World, still in warranty and they have offered to replace it at no cost, why not go with that??

Then you can start afresh with how you maintain the battery.

The fridge is a heavy drain for any type of battery and engine alternator charging is just not going to keep the charge up unless you are motoring all day every day.

I am just spit balling here but say the fridge is efficient and about 60 litre capacity, I think you will need about a 120 amp hour deep cycle battery to run it and a minimum 80 watt solar panel to keep the battery charged.

That battery should be dedicated to the fridge. Then you need another battery for start and house load. If you have all LED lighting a 100 amp hour battery should be ample.

Boat batteries sit idle for long periods and benefit from being charged up with a battery charger as often as possible. It appears you do not park your yacht on a marina often so lugging the battery ashore for charging is necessary. Your battery charger should be a minimum 8 amp unit.

A C-Tek 10 amp charger will cost you $370 if you shop around and get trade price and a 15 amp unit is only a little more. These are "Smart Chargers" which is mostly all you can buy today as opposed to transformer chargers.

Battery World sell an "AusCharge" unit, 1 to 8 to 12 amp charger, one of which I have just bought, that through them carries a 5 year warranty for $219.

The thing to keep in mind with batteries is that no matter which type they are, fully discharging them buggers them big time. My mate who lives aboard quite a lot has Century Marine batteries of which he speaks highly describing then as a cross between a start battery and deep cycle.

Marine electrics is all done with smoke and mirrors.

Pm sent if you look up the part number it will give you the measurements

Hi Steve,
I've got a 60ltr fridge and 4 x 100ah batteries. I have a separate 80ah battery for the engine. I forgot to connect the shore power one day and had the fridge still on. I got down the boat 5 days later to realise my mistake. The fridge was still cold (still frost inside) and the battery bank was flat, ie: 11volts. That meant I got 5 days of power with no solar panel or other charge during that time , admittedly I was not opening the fridge during that period.
Based on that, I'd guess yours has been discharged too far and is stuffed. I had a similar prob to you on the last boat, without a fridge then, went and bought a bigger battery and lived happily ever after .
Hope this might help as a reference!

Perhaps you should also check out your charging circuits, make sure your alternator etc are working correctly.

I have a Century house battery (from Battery World) and can vouch for them. It is now just over a year old, gets run down, but not flattened, most weekends and will easily start the engine (if it is still warm). I don't have solar or wind generators, but have a 'smart charger' at home if required.

As per Cisco, the plan is to add another house battery in the next 12 months dedicated just to the fridge, and run the electronics off the other one. Just need to find room in the engine box for the starter battery.

I've only the better one left Steve
it's been charging in the solar panel ever since it was on the boat 14.2 volts
it runs my Engels when needed
it's free if you get down here

Hi steve
10volts its beyond dead flat , 11.8-12 is considered flat with a 12v battery

knowing your battery capacity is important if you have 20ah battery it would be normal for it to run flat quickly but a with 100ah battery there would be a problem .

How big is your battery in a/h ?
Solar size ?
Alternator output ?

Its sounds to me like you may have a really small battery or a dud
A fully charged 105ah battery for example will run a 50L waeco fridge for 2 days with no charge input by then battery volts are at about 11.8-12v
so something isn't right

you hear your battery rocking around I'm assuming its a wet cell then , have you checked the water level's?

What H28Kurt said is right, 10V is potentially a killed battery. A 12V battery is 6 x 2V cells in series. If one of them fails completely you cant cure it and wind up with a 10V battery. But if lucky just all the cells are depleted and max charging can save it.

To judge if an AGM or lead acid battery battery can do its job in a given situation you can estimate that the power you can get out of the battery will be 85% of what you put in.

Using "Amp Hours" approximately works. If you charge your 12V battery for 10 hours at 4A you have put in 40 amp hours (less 15%) in. ie. You have reversed the chemical reaction inside the battery to that extent. If you then put a 1A load on it for 40 hours you will go past the 40AH that you put in and the battery will be badly flattened. Sometimes they can be recovered. In AGMs especially.

I'm still learning by trial and error re my batteries, but what a lot of liveaboards do that i've been meeting is have a generator on board that they plug in to charge the batteries rather than run the engine and charge via the alternator.

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McNaughtical said..
I'm still learning by trial and error re my batteries, but what a lot of liveaboards do that i've been meeting is have a generator on board that they plug in to charge the batteries rather than run the engine and charge via the alternator.

Running the main motor to just charge batteries is to be frowned upon, the motor needs to subjected to a decent load or you will glaze the bores. the generator idea is to be applauded, it will be more economical and on the noise front not be as annoying.
Use the main engine for charging when you are using the engine for boat propulsion or if you have an engine driven water maker.

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LooseChange said..

McNaughtical said..
I'm still learning by trial and error re my batteries, but what a lot of liveaboards do that i've been meeting is have a generator on board that they plug in to charge the batteries rather than run the engine and charge via the alternator.

Running the main motor to just charge batteries is to be frowned upon, the motor needs to subjected to a decent load or you will glaze the bores. the generator idea is to be applauded, it will be more economical and on the noise front not be as annoying.
Use the main engine for charging when you are using the engine for boat propulsion or if you have an engine driven water maker.

It's a combo of low revs and low load that glazes the bore, if you keep the revs up there is no prob. Above 1500 on a typical high speed diesel.

BTW, measuring a battery voltage only tells half the story and does not reveal a batteries true state of charge (soC). I've had batteries on their way out that still read 12V, but nevertheless could not take any significant load. Treat yourself to a proper batter analyzer like the one in the photo.

Also, +1 for dual-purpose batteries, which have the advantage of tolerating deeper discharges that would wreck most pure starter batteries, and typically last longer as a result. I've been happy with the Ultimate UL-100 AGM batteries from Battery World. Of course, no lead-acid battery tolerates complete discharging for long.

As an aside, the flow batteries now on the market for household energy storage do tolerate routine discharging to 0%, but they have not yet been adapted for marine use. Google Redflow.

Battery voltage is an ok indicator of state of charge but it's only a very rough guide and varys from battery to battery and meter to meter too. Some devices (i.e. some of the mastervolt chargers) can give you a state of charge quite accuratley though. i'd bet my money on the fridge. What fridge is it and what battery capacity do you have? What size is the boat? Motorboat/sailing yacht? How many amps does the alternator produce? If it's a deep cycle battery it won't get ruined at all from running it flat occasionally.


Just as an example: If the weather is warmish my 2L Bmw will usually still start if the meter reads 11.4 volts at rest... A 2L engine needs quite a lot of cranking power to start... In theory that means the battery has about 10-15% capacity left, however, a good 90ah lead acid battery probably needs around 40% or more to start a 2L engine...


Imho all boats should have an amp meter wired to the voltage regulator/alternator output (alternativley at the battery output, but that is not as good). That means that you can experiment with how much current your electric devices use once the battery is full and therefore get a good estimate of how long you can run devices and how much they use. People always seem to think that that stuff like computers and Radar or instrument panels use a lot of current but in real life it's usually fridge/freezers from the 90s and the autopilot.


If you live in sunny Australia there is no excuse to have flat batteries unless you have a lot of heavy electronics on the board.
Have deep cycle consumer batteries, lead acid starter batteries (just in case, you should generally start via the consumer batteries), add some solar panels and you are good to go. No need for windmills and that rubbish, doesn't produce anything. If you sail a lot and at good speeds a generator attached to the propellor and some solar panels mean you basically never run the engine.

I agree that for (non-engine) battery charging, solar panels are the way to go in Australia. Install as many as you squeeze in.

Another option, for cruising, is a tow generator. As kit2kat says, a prop shaft-driven alternator is another option, unless you have sail drives.

BTW, compare to being at anchor, wind turbines relatively useless when cruising as the apparent wind is usually too small to produce useful amounts of power.

if you could fit an idler shaft running off your prop shaft you could a decent ratio to spin up a regular alternator as a alternative pending of course that your gearbox is OK to spin when sailing

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HG02 said..
if you could fit an idler shaft running off your prop shaft you could a decent ratio to spin up a regular alternator as a alternative pending of course that your gearbox is OK to spin when sailing

There is still no such thing as a free lunch, prop drive alternators cause a lot of drag, in part because they use the wrong curvature of the prop to generate power so poor hydrodynamics.
It's true that wind turbines are not great when you are sailing because there is often not enough apparent wind, but in practice they are not bad - I had 500 watts of solar on Lyra and found that the wind generator often put in as many amp-hours because it was often working when there were poor solar conditions. And upwind they go really well.

I took the battery off today and to it back to battery world for the second time. It's. 55ah Mercury. Never really worked properly. Of course it I fully charged, but once you start using any power, you see the meter go down fast. I'd only run the fridge fr 30min. But now anything flattens the battery. Sounder, lights, radio. I only use things as I need them and when not in use they're off at the mains. Battery world say that my charging system isn't working, but this isn't true. The battery is a dud, doesn't hold a charge. Never really did. I admit that my panel is to small at 40watts and my battery too small also, but I should still get more than what I've been getting from the battery. So battery world are testing the battery again, but they're now being a holes about it and don't wanna replace it As they say that the warranty doesn't cover me running it so low.

55 amp hours is very small running a fridge,lights and radio flat overnight Or the next day.. Look at a 120 amp battery with 80 watt solar panel If you want a long weekend away..

do you think 400watts of panels and 150ah plus the 55ah, 200 total is overkill??
I am getting the boat ready for QLD and beyond and i dont wanna run out of power! i also want the comfort of the fridge, plus ill be running ais, tiler pilot and maybe some other stuff!

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Kit3kat said..
Battery voltage is an ok indicator of state of charge but it's only a very rough guide and varys from battery to battery and meter to meter too. Some devices (i.e. some of the mastervolt chargers) can give you a state of charge quite accuratley though. i'd bet my money on the fridge. What fridge is it and what battery capacity do you have? What size is the boat? Motorboat/sailing yacht? How many amps does the alternator produce? If it's a deep cycle battery it won't get ruined at all from running it flat occasionally.


Just as an example: If the weather is warmish my 2L Bmw will usually still start if the meter reads 11.4 volts at rest... A 2L engine needs quite a lot of cranking power to start... In theory that means the battery has about 10-15% capacity left, however, a good 90ah lead acid battery probably needs around 40% or more to start a 2L engine...


Imho all boats should have an amp meter wired to the voltage regulator/alternator output (alternativley at the battery output, but that is not as good). That means that you can experiment with how much current your electric devices use once the battery is full and therefore get a good estimate of how long you can run devices and how much they use. People always seem to think that that stuff like computers and Radar or instrument panels use a lot of current but in real life it's usually fridge/freezers from the 90s and the autopilot.


If you live in sunny Australia there is no excuse to have flat batteries unless you have a lot of heavy electronics on the board.
Have deep cycle consumer batteries, lead acid starter batteries (just in case, you should generally start via the consumer batteries), add some solar panels and you are good to go. No need for windmills and that rubbish, doesn't produce anything. If you sail a lot and at good speeds a generator attached to the propellor and some solar panels mean you basically never run the engine.

i bet youre right. the problems started when the fridge arrived! its a waeco 30litre, fridge freezer. works very well, but drains the 55 ah battery fast so i only use it for 30 min to cool my beers down on a day sail. Ive also realised that my inverter uses alot of power, and 1 time i accidentally left the inverter on with nothing plugged in, but after i did this i drained the battery. its a 25 foot tophat. i have a depth sounder, cabin lights, radio, cig lighter(that i plug fridge into) 240v inverter. My outboard is wired up to the battery and charges battery very well . the solar panel is only 40watts. I have no inboard motor and dont crank any engine with battery. i have a 8hp mercury with cables going to the battery(not directly) i do have a volt meter on my electrical panel, fused etc..it all works well, but ive gotta sort this power out if im too venture north next year. il also be adding to the power draw a tiller pilot and ais/gps.

My experience is slowelly telling me more solar than battery has too be achieved for full sustainability. You will never win unless you use candles and ditch the fridge!

I'm interested in running a primary battery bank and solar just for the fridge/ freezer and then use my remainding battery's charged from engine and surplus solar and wind.

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Sectorsteve said..

Kit3kat said..
Battery voltage is an ok indicator of state of charge but it's only a very rough guide and varys from battery to battery and meter to meter too. Some devices (i.e. some of the mastervolt chargers) can give you a state of charge quite accuratley though. i'd bet my money on the fridge. What fridge is it and what battery capacity do you have? What size is the boat? Motorboat/sailing yacht? How many amps does the alternator produce? If it's a deep cycle battery it won't get ruined at all from running it flat occasionally.


Just as an example: If the weather is warmish my 2L Bmw will usually still start if the meter reads 11.4 volts at rest... A 2L engine needs quite a lot of cranking power to start... In theory that means the battery has about 10-15% capacity left, however, a good 90ah lead acid battery probably needs around 40% or more to start a 2L engine...


Imho all boats should have an amp meter wired to the voltage regulator/alternator output (alternativley at the battery output, but that is not as good). That means that you can experiment with how much current your electric devices use once the battery is full and therefore get a good estimate of how long you can run devices and how much they use. People always seem to think that that stuff like computers and Radar or instrument panels use a lot of current but in real life it's usually fridge/freezers from the 90s and the autopilot.


If you live in sunny Australia there is no excuse to have flat batteries unless you have a lot of heavy electronics on the board.
Have deep cycle consumer batteries, lead acid starter batteries (just in case, you should generally start via the consumer batteries), add some solar panels and you are good to go. No need for windmills and that rubbish, doesn't produce anything. If you sail a lot and at good speeds a generator attached to the propellor and some solar panels mean you basically never run the engine.

i bet youre right. the problems started when the fridge arrived! its a waeco 30litre, fridge freezer. works very well, but drains the 55 ah battery fast so i only use it for 30 min to cool my beers down on a day sail. Ive also realised that my inverter uses alot of power, and 1 time i accidentally left the inverter on with nothing plugged in, but after i did this i drained the battery. its a 25 foot tophat. i have a depth sounder, cabin lights, radio, cig lighter(that i plug fridge into) 240v inverter. My outboard is wired up to the battery and charges battery very well . the solar panel is only 40watts. I have no inboard motor and dont crank any engine with battery. i have a 8hp mercury with cables going to the battery(not directly) i do have a volt meter on my electrical panel, fused etc..it all works well, but ive gotta sort this power out if im too venture north next year. il also be adding to the power draw a tiller pilot and ais/gps.

That's a lot of gear to try run. Doesn't matter what size battery you use you have to get all those amp hours back in and you wont do it from an outboard alternator. To run all that think 200 amp hour battery bank and think in terms of a 24 volt 200 watt solar panel charging through a MPPT controller. And you will still need to run the engine at times. It's a big ask on a Top Hat.

But let's say you use only the fridge in the day for 3 hours A day while there's sunlight. 200ah batteries 400watt solar. Whilst fridge is on everything else is off except the sounder if I need it. I'd use ais only at night and tiller pilot most the time, but sometimes not if I can sheet to tiller/hand steer.at night I'd use the cabin lights and stereo. I do have these great Ikea solar lights that work sooo well. They charge real quick and last all night. Bright too.

ikea solar lights. bright, run for ages, also charge AA batteries really well too. $12.

your best wet cell house battery is a trojan 6 volt x two makes 12volt and add two more as you go .
At work both our scrubbers use 9 trojans each from memory . there used every day and there volts are up and down like a yoyo and they take it for years. There not cheap but work really well. There the best house wet cell battery around Price I think there around the $250 mark each

I guess there classed as golf cart batteries

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southace said..
My experience is slowelly telling me more solar than battery has too be achieved for full sustainability. You will never win unless you use candles and ditch the fridge!

I'm interested in running a primary battery bank and solar just for the fridge/ freezer and then use my remainding battery's charged from engine and surplus solar and wind.

i plan to use a 150ah for fridge(only running a few hours a day) tiller pilot , ais(when needed) and the 55ah for cabin lights , stereo and sounder. Alot of the time there wouldnt be anything draining any power at all.

THe bluebird i had was soo simple. i rigged it with a 20 watt panel and a 20ah battery. the battery NEVER died. i would go away on the bluey for 2 weeks sometimes. I only powered the radio which was on all the time and used the 12 volt socket to keep my phone/ipad charged. THat battery only went flat after nearly 2 years when it was worn out. i had a really good esky, that keeps things cold without ice its that good! I used those ikea lights.

Im still tryna keep it simple. theres more on the tophat, but alot of the things that require power are off unless i need them - like the sounder whilst going up port hacking last week. Couldnt even really use the fridge, but i tried as i had milk etc...
So surely if i up the batteries , use things only as needed, have more panels, it should be ok!

Hi Steve,
I did it again. Didn't throw the switch on the shore power. 60l fridge was on, 400ah batteries, 6 days later I get down the boat, still had 12.2v. The fridge was still nice and frosty. We charged it for an hour, then sailed all day with the following on:
Fridge
Computer
Nike auto helm and electronics
Radio (charging and playing an I phone)
Wireless access point
Cabin lights (thanks kids)
Water pump
I don't have any solar panels or win vane, we came home with 12.4 v. Structures recommended I upgrade from the standard 200ah to 400ah when I opted for the hot water, so regards battery capacity, to me 200ah should be plenty i would have thought!

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Shaggybaxter said..
Hi Steve,
I did it again. Didn't throw the switch on the shore power. 60l fridge was on, 400ah batteries, 6 days later I get down the boat, still had 12.2v. The fridge was still nice and frosty. We charged it for an hour, then sailed all day with the following on:
Fridge
Computer
Nike auto helm and electronics
Radio (charging and playing an I phone)
Wireless access point
Cabin lights (thanks kids)
Water pump
I don't have any solar panels or win vane, we came home with 12.4 v. Structures recommended I upgrade from the standard 200ah to 400ah when I opted for the hot water, so regards battery capacity, to me 200ah should be plenty i would have thought!

THanks Shaggy., wow, you are running alot and still your batteries are good!, good to know :) So you only charge using shore power and engine/genny?

Yep. I like clean uncluttered lines so no bimini, and I didn't want solar panels underfoot. I almost got a watt and sea hydrovane, till we worked out I could charge using the diesel for over 4 weeks on one tank.
If I was going to spend 30+ days off shore with no refuelling option , I would have gone for the hydrovane, but no plans yet for this duration os...yet!

lead acid batteries are very different to the batteries in your phone/tablet/laptop.

they don't take kindly to being overcharged, deeply discharged, or being left sitting discharged. if you regularly ran the battery down low then you have most likely prematurely killed the battery.

what you want to do is to calculate the power usage of all your gear. once you have that number, a rough rule of thumb is to have 3-4 times that capacity in your battery bank so that you can avoid deep discharges.

Not suggesting hydrogenerators are worth the cost unless long haul trips are planned, but they have come a long way , this is a neat install of a W&S 600w on a 12.50.