Domestic battery capacity ?

[lasse36ip]

Something to fix after first sailing season with SO36i in Finland.
I have 2x70Ah in domestic side and the experience is that it is way too little for our purposes. Average consumption is more than 2Ah per hour, thanks for enormous fridge...
Engine runs less than hour per day and we stay as much as possible in nature harbors without shore power.

Two main ideas
1.) Increase capacity to over 200Ah, need to move batteries also to port side (3-cabin version)
2.) Fixed solar panel for continuous charging (hope that there is more sunshine in next summer

Any comments, what solutions you have in use?

[Zanshin]

Having sufficient or excess battery capacity is great thing, reducing wear-and-tear on the battery bank and giving a comfortable feeling with reserves. I think that the most important single instrument on my past boats has always been the battery monitor. The first thing in the morning would be to stumble to the instrument panel and turn off the anchor light and check the remaining battery capacity. Even now with my huge bank the procedure is the same.
My wind generator did a good job but that is in the tropics with the trade winds blowing even at night. Note that the last 10% of the battery capacity is very slow to charge and usually going below 50% charge is considered bad. Thus one only realistically has 40% of the rated capacity to use - in your case (140Ah * .4 = 56Ah) which is very little - unless you have an LED anchor light you should have full batteries before going to sleep and need to charge in the morning.

[rene460]

I certainly agree that the two x 70 amp hour batteries is inadequate for what you propose, especially as one is reserved for engine starting.

I suggest that first you need some charging I.e.solar panels, as much as you can afford and find space for. Top of Bimini is a good location.

Second some extra battery capacity will help you survive overnight, but difficult to add enough. Occasionally you will have to run the motor solely for charging, with hot water as a bonus. Install a digital voltmeter so you can monitor the battery and not go too low.

Third practice some power conservation - put a solid ice block in your fridge before you leave port, then switch off fridge overnight (use a fridge thermometer to keep a check that you do not over do it), change to LED lights for your most used cabin lights, use a candle or oil light for you anchor light (nearly as important as fridge!). The ice block trick works for several days in our Southern hemisphere summer, it will work even better at your latitudes. A few of those gel packs also "store a bit more cold" when the fridge is running. Our ice box seems very well insulated. Turn thermostat a bit colder for when the fridge is running and always run it when motoring - power used as generated is much more efficient than power stored and used later due to battery efficiency!
All of us who camp on our boats away from shore power have these issues, so let us know how you get on and any more ideas.
Rene460

[sailbleu]

I have close to 300 amps and consider this still too little capacity even though I can also rely on my bowthrusters battery of 220 amps.
But my windgenerator and 2 big solarpanels are sometimes not up to the task to keep the batteries full. Maybe I'm using far too much energy , but my wife and I like a bit of luxery on board.
All my lights are leds mind you.
By next season I will have installed more solarpanels on the sprayhood and bimini.
And yes sometimes my generator has to chip in too, I just dont like the hours on the main engine only to charge up the batteries you see.

Regards

[Zanshin]

- Sailbleu: While we are chest-thumping about on-board battery capacity: I have 1320Ah and still feel like I could add more

See www.sv-zanshin.com/modifications/batteries.php

[dublin]

2 by 70Ah is just not enough. No matter what method you choosecto recharge them you must add more capacity. We have 3 by 120Ah and that gives about 3 days without recharge - ie not using engine at any time in that period.
Looked at adding wind but the the experts worked out that it would not be enough to replace the drain and the batteries would discharge over about 5 days instead of the 3. Decided it was not worth the cost. Also looked at solar and came to the same conclusion. It s fine to think of fixing on Bimini etc but they'd don't work efficiently if any part of the panel is shaded as the cells run in sequence. With mast, shrouds stays etc there is always some element of shading. Remember fitting fixed panels will require pushpit, Bimini etc ) I.e. wherever they are to be affixed to be beefed up. Also if you put them on the Bimini it is then not easy to remove Bimini when big winds foecast.
Also looked at increasing capacity and changing to agm which due to their deeper discharge facility allow more power to be extracted before they are destroyed. In reality your 140Ah only give your usable 56Ah. This is because they will very seldom be more than 90% charged and you should not discharge below 50%. So you only have access to 40% of the nominal value from each battery.
You should not run the engine just to charge the batteries except in emergencies as it will cause costly damage to the engine.

I finally bit the bullet and bought a Honda suitcase generator. I did not want to plumb in a fixed generator. This recharges the batteries with minimal fuss and at minimal cost. If you only use it to charge the batteries and occasionally run some small electric equipment you will only need the small 1kv one at a cost of about €800. If you want to run more heavy duty equipment you will need 2kv model. The bigger one has no more noise. They are no more noisy that a wind turbine.

[oasis36i]

I too am in my first season with a 3 cabin 36i. My plan for next season is to buy an extra battery for engine starting and hopefully fit this just next to the battery charger, and then use the existing 70ah battery in parallel with the other two to give 3x70=210ah. This should increrase the capacity a bit without too much disruption. This is a trick I have seen elsewhere on this forum. I am also fitting a simple NASA battery monitor.

I found on my previous boat that the NASA unit worked wonders to show me my actual current drain of various items. The fridge is naturally the biggest drain, but I could run it for nearly a week with 220ah because all my lights were led (drawing 0.1 amp each) including the anchor light. I turned off inessentials when I knew just how much they draw. For example, the non led reading lights burned 2 amps each, so it was actually better to turn on 10 led lights and not turn on any reading lights. I also discovered that the stereo was drawing current when apparently turned off, so I disconnected it. It really wasn't a chore to turn things off, and really helped to see the current flowing out.

[rxc]

I second all of the recommendations made, but would also suggest that you look carefully at the batteries you are going to buy, and make sure that you buy deep cycle ones for the house bank, and stay with a conventional automotive starting battery, which is only used for starting the engine. Golf cart batteries are particularly suitable for house loads, because they are usually widely available, at a reasonable price, and give you a lot of capacity in packages that are not too heavy to lift. The biggest problem is finding a place to put them.

On my old 34ft boat, I had 4 golf cart batteries, and one starting battery. I have a similar setup on my 43DS, but with 3 other batteries for engine, genset, and windlass/thruster. They must be actively managed. I would like to have 2 more golf cart batteries, but don't have anywhere to put them.

Oh, and don't try to just add another battery. It will be newer than the old ones, and they will charge/discharge one another, and die a premature death. Make sure all batteries are similar age and chemistry.

[MartyB]

oh dear,
not sure I would want to know how some of you would get by with a single size 24! hen it died, I modified the storage space and put in a single size 31 that is 105AHr by itself. But having had a few land RV's, it does not take too long to wear out some sizes of batteries. 6V have generally speaking last longer from a size to size vs a n equal size 12V. As they have more lead, which is the key. Some places have tha ability to get a higher Ahr of equal size. My old 24 was an 85 ahr vs the std 25 a 75 or there abouts. it did cost me a few more dollars, but worth it.

I do know of some small AGM tyles that hae more ahr to them, but do come at a BIG price. You would probably have to go to a different alternator, too, as they accept upwards of 40% of he Volage drop vs lead only at 25%. So you could blow up the alternator going with an AGM style.

Good luck wih choice, almost as highly contested a what should I do as anchor options!

Marty

[tedp]

On my SO32 I replaced the 75Ah house battery with a 105Ah deep cycle battery. I kept the 75Ah starting battery. The reason was I once used the heater and the fridge when at anchor and I was left with a flat house battery next morning. The space in the SO32 is limited so I made a new battery box from plywood and epoxy. Epoxy is resistant to battery acid. This replaces the original polythene battery boxes which sat in a small space under the bunk in the aft cabin, next to the engine:



I also replaced the anchor light and most of the saloon lights with LED lamps like rene460 suggests. Since then I can easily do without shore power for over 24 hours, and indeed I often do so as we also like to stay overnight in quiet places.

The main thing not yet changed is fitting a diode bridge to the alternator charging circuit to replace the bridge relay. This means I can charge the house battery under engine, but not up to its full capacity due to the different sizes of the starting and house battery. The 230VAC battery charger will top them up fully however.

[SO 36i - Penelope]

We also discovered that 2x70ah is way too little for our SO36i. This year we installed 3x75ah deep cycle semi traction batteries. Which work good. Over 24 hours in warm weather (>25c) and still no batterie alarm. The standard fitted jeanneau batteries are start batteries which are not suiteable for service like fridges, navigation and lights. These deep cycle batteries sink faster to a lower level of voltage but maintain that for a long time. The standard fitted Cristec 25a charger needed to be adjusted to different programm (1 minute job) but gets them easily filled up again

[Anwen (Deep Joy)]

I still have 2 x 70Ah on my SO32 , with one battery dedicated to engine starting. I have done some modifications to help manage this. The first thing was to replace the anchor light with an LED bulb. The original housing wasn't tall enough so I had to fit a new housing as well as the LED bulb. I have also fitted a Sterling smart regulator charger, and replaced the voltage sensitive relay with blocking diodes. This has made a huge difference to how quickly the house battery is recharged by the alternator and would recommend this as a first step.

The SO32 doesn't have a lot of room for additional batteries. One option I have been considering is to use a Red Flash battery for the engine which can be located in the engine bay and convert the old starting battery to an additional house battery. I also turn the thermostat up on the fridge at night - I found that I was running the fridge way too cold most of the time, and it really didn't need to be. Of course, if you boat is in a warmer climate, then having ice in the icebox is probably more important.

Oh, and I fitted a BEP battery monitor, which has helped to manage battery drain. Any of the smart meters with a shunt would be a worthwhile addition in my opinion.

[tedp]

Thanks, Jon - I am thinking of fitting a smart regulator to the alternator as well. There is indeed very little space for extra batteries in the 32, that's why I made a dedicated battery box having space for a bigger battery. But being able to recharge faster and effectively should be a great improvement. And using LED lights makes a big difference.

Ted

[rene460]

Hi Ted,
That is a great battery box you have built, but where do you fit it, and why did you replace the individual plastic boxes?
On our 30i, our house and engine battery are just near the charger in the rear cabin but no extra space closeby to even enlarge a battery. I am not sure how this compares with your SO32. As you can see from above we definitely need more capacity despite our managing with conservation measures so far. They will not be adequate once our capacity starts to drop, and an hour or so of TV may have passed the limit already!
Does anyone have any suggestions for best place for additional batteries in a 30i? I am thinking of front cabin in front of water tank, rear cabin port side aft space (occupied by fuel tank on port side) or even in cockpit locker on floor beside holding tank. The latter is easiest for handling as boom and main sheet could be used. Other locations make lightweight batteries essential, not good for big capacity. The plan is for at least two new batteries to replace current 70 ah house battery, and preferably each larger.
Rene460

[MalcolmP]

Sept 28, 2012 8:16:28 GMT rene460 said:

Does anyone have any suggestions for best place for additional batteries in a 30i? I am thinking of front cabin in front of water tank, rear cabin port side aft space (occupied by fuel tank on port side) or even in cockpit locker on floor beside holding tank. The latter is easiest for handling as boom and main sheet could be used. Other locations make lightweight batteries essential, not good for big capacity. The plan is for at least two new batteries to replace current 70 ah house battery, and preferably each larger.
Rene460

Hi Rene
Not 30i specific, but bear in mind that it is preferable to keep cable runs as short as possible (and/or keep cables as large as possible) I would avoid weight in the extreme ends, particularly the bow due to impact on performance

If you have loads of money how about a fuel cell, the weight on the methanol is negligible compared with lead... but in the UK at around £3.5k may not be sensible

Malcolm

[Anwen (Deep Joy)]

Rene, I would look at using a compact battery for the engine starting, which can be located in the engine compartment, possibly near the gearbox and prop shaft. I think these are used for motorcycles and are AGM type batteries. They are very compact - less than half the size of your current 70Ah ones, and can be fixed with a simple bracket as they are sealed for life. Red Flash is the brand I looked at. This will then allow you to use the current batteries in parallel to double your domestic bank.

I would also look at a smart charger to replace the standard Jeanneau voltage sensitive relay control for the alternator. The smart charger will get you that extra few % into the battery when it is nearly full, as well as speeding up the early part of the charge. I fitted Sterling as these are very cost effective, but there are other brands out there. You need to install a blocking diode system as well. Ignore people who warn you about the voltage drop over the diodes - the regulator installation accounts for this.

If I had kept Deep Joy, I would have added the Red Flash starting battery this winter.

[rene460]

Hi Malcolm, if I had loads of money I would probably have a larger boat, a 33i perhaps. But clearly fuel cells have dropped in price and I can see them coming in as a preferred auxiliary generator. The fuel is safer than petrol and they are silent.
In the mean time I will increase my battery capacity to get through the night (probably still with an ice block in the fridge) and some more solar cells. My current panel is 12 years old and only 55 watts. A new 80 or 120 watt panel will be smaller, and still fit neatly on top of the Bimini. I am also planning doubling up the main supply wire while the voltage drop on the original is within spec, I would be prefer lower loss.
Jon, I like your idea of a smaller starting battery, easier to locate and leaves the prime space for two house batteries. I am looking into what batteries are locally available as the local guy's support is invaluable, and I do not like mucking with engine voltage regulators. Multiple 5 MW alternators, I can handle but those little black boxes they put on engines? Totally mysterious!
Rene460