Bav 30 House Battery

[Sadlerfin]

Looking like the house battery on my Bav 30 is near the end if it's life from fully charged this weekend it was dead within the afternoon at anchor all be it with the fridge running.

The boat is still relatively new to us so I'm assuming the domestic battery is the larger (140A) on the port side of the cabin. Can anyone recommend a suitable replacement and where to source it?

Thanks

Derek

[sunshine]

Recently changed mine to a 180Ah Bosch from alpha batteries. When you factor in P&P the cost is almost identical to Tayna.

A few things to note:
New one is flat sided (no "toe") so the existing clamps have nothing to hold so you might need a new securing method
The sizes quoted online are for the top of the battery, not the foot.

If you want a straight sea 140Ah with no mucking about then check the footprint and toe of any replacement.

I made up a restraining foot plus straps, see photo

[Baddox]

Our boat had a pair of those fitted and I've just replaced them after much consideration...

The S5 Bosch batteries look good and are made by the same company that brand the Varta batteries which appear identical
Our 140Ah batteries sat side by side in the same orientation as yours and still had an inch of room at the side before the hull curved up.  There was space above too.

For not much more you could get the 180Ah battery but that is bigger and wouldn’t fit as a pair.

Checking the power demands suggested we wouldn’t need all that power anyway.  So we ended up buying a pair of Hankook 110Ah batteries from Battery Megastore via ebay, which still cost less than a single140Ah Bosch, rationalising that we were left with space to add another one or two later if needed.

[Salty]

If you have only a single 140ah domestic battery, and depending on how long your fridge was running and whether the battery was fully charged prior to running the fridge, then it may have been asking a lot of that battery.
Batteries are often forgotten until they are really needed, and then they let you down. Do you know if your battery is one requiring no maintenance that basically you fit and forget, or is it one where the individual cells can be opened to permit the density of the liquid to be checked. If it can be checked, and don’t answer this, when did you last check it? Is the level of liquid sufficiently above the tops of the plates? Have you left the batteries on charge for long periods where you have the mains lead plugged in to your boat and the charging system is running continuously, this causes the liquid level within the battery cells to become depleted, and then as they gas off, the gas released can trigger a carbon monoxide alarm even though it’s not CO gas!!!.
Normally I check the density of the liquid in my batteries at least once a month, noting also whether any of the cells need to be topped up with de-ionised water, and I keep a record so that I can check over a period of time if the density readings are getting lower or if I need to top up more often.
As for getting new batteries, well you pay your money and you make your own choice. Generally the better quality batteries will cost more, but you can pay more than you should depending on whether the salesman can sell you a good story. You can buy from your local battery retailer or you can buy from the likes of eBay. Wherever you buy from, make sure that the battery you choose has the same securing arrangement or facility or you will find yourself having to make a new securing arrangement. One thing you don’t want are loose batteries charging around while your boat is rolling heavily at sea.

[Yngmar]

Try https://www.alpha-batteries.co.uk/boat-batteries/ - they specify typical lifetime in cycles, which is the most important thing on boats. Forget brand names, they don't matter. A lousy FLA (flooded lead-acid) will have just 70 cycles at 50% DOD (depth of discharge), a quality FLA about 200, an AGM three times that. Based on that and the additional safety factor (no need to have a spill-proof enclosure around the batteries), I'd usually go with AGMs.

50% is by the way as far as you should discharge most conventional batteries regularly if you want them to have a long life, so the available capacity is half of what's written on the label (and diminishes over time).

Make sure the new batteries fit the space and have matching terminals (with same alignment +/-) so they can be fitted without major reworking of the battery locker.

[Symphony]

The choice of battery depends on how you use the boat and what means of recharging you have. As already stated for long life it is best to keep discharge to 50% of capacity, so your current battery will give you a useful capacity of 70AH. Leaving your fridge on overnight will use at least half of that. On the other hand your engine will not be able to recharge that in the typical hour or 2 motoring at the beginning and end of the day. So, if you are a typical weekend sailor you will need alternative charging sources such as solar to recharge during the week or shorepower.

So, worth getting a battery monitor so that you can get an idea of your usage pattern to determine how much capacity you need, but would say 140AH is pretty much the minimum. As to type of battery the main choices are between flooded lead acid or AGM. The advantages of the latter are that they will take a higher rate of charge and usually have greater discharge cycles, but at a cost, and are more attractive to people who spend a lot of time on their boats.

For weekend plus summer holiday sailors deep cycle lead acid are probably the best value and are what was fitted on the boat originally. On my last boat a 2001 B37 I replaced the original 140AH with two 115AH deep cycle with a similar footprint, mounting and terminal location as the original Bosch. this type is commonly available and when choosing look carefully at the expected number of cycles and the weight. Generally the greater the weight in relation to the capacity the longer they will last.

[Ricd]

If your battery bank is dead in half a day it is dead and cannot be revived. As Symphony says your batteries should never be taken below 50% charge thus your 140Ahr bank has only a usable 70Ahr capacity which is pretty low.  As a rule of thumb, a fully charged battery (not being charged) should read 12.8V and at 50% charge it will read 12.2V so when it appraoches 12.2V its time to start the engine and charge the bank. 
Running the fridge for half a day is not a significant factor.  We run our fridge continuously while on board/at sea.  It draws I think about 3/4A when running but of course it only runs every now and again, say for about 10 to 15mins max in every hour. 

[Sadlerfin]

Thank you all for your replies.

A new battery it is...

Just so I am certain, when i leave the boat connected to shore power on my berth i generally switch the power off at the panel except in winter when a dehumidifier is connected. Am I correct in assuming that as long as the keys are out then no charge is going into the batteries?

Thanks again

Derek

[Sadlerfin]

What I meant by my previous post is could I overcharge them by leaving them on charge when away from the boat?

[Salty]

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Just so I am certain, when i leave the boat connected to shore power on my berth i generally switch the power off at the panel except in winter when a dehumidifier is connected. Am I correct in assuming that as long as the keys are out then no charge is going into the batteries?

Thanks again

Derek

I’m fairly sure that unless you have a switch that positively turns off your mains battery charger, then all the while your 240 volt system remains live, that your battery charging system will remain enabled. Normally your charging system should sense when your battery is charged and should modify its feed to one that does nothing more than maintain your battery at an optimum charge level. If you have one less than perfect cell, then the charger will attempt to bring the battery as a whole up to optimum level which will cause the less than perfect cell to gas off. Couple that with the dry atmosphere within your main cabin from your use of a dehumidifier, and you have a recipe over time that can lead to the drying out of individual battery cells.
My B36 (2002) did not originally have a specific isolating switch that would switch off and isolate the battery charger from the 240 volt mains supply until one night when one or more cells began to gas off and my carbon monoxide detector began to make a bit of a fuss. It was winter time and I was staying overnight, and it was pretty cool outside during the early hours of the morning while my half asleep mind tried to figure out why the CO detector had gone into alarm when nothing else on the boat was actually in use, let alone any heating system that might have given off CO.
So unless you have an isolating switch for your mains battery charger, then most likely it will remain on all the while you have a live mains plug connected.
I have since fitted an illuminated isolating switch into the mains circuitry so that I can have mains power on but battery charger off, or on according to my choice at the time.
As for my dehumidifier, well since all the water leaks have been stopped, it’s become another piece of unused junk to clutter up my garage !!!

[Ricd]

The only point in having shore power on while away from the boat is to run the battery charger (and de-humidifier in winder while boat laid up).  My current batteries (basic FLAs) are now 11 years old and still in great condition...I have the battery charger permanently running while on shore power and shore power  is connected at all times while in marina.  Having said that, my battery charger ( a A Sterling multi stage charger) connects to shore power via a 13 amp plug so if I wished (and i never have) I could isolate it by unplugging it but why would I do that?  it would not then charge and maintain the batteries.

Buy some new batteries and keep them well charged, never let voltage drop below 12.2 volts.

[dawntreader]

...I have the battery charger permanently running while on shore power and shore power  is connected at all times while in marina.  Having said that, my battery charger ( a A Sterling multi stage charger) connects to shore power via a 13 amp plug so if I wished (and i never have) I could isolate it by unplugging it but why would I do that?....

....you would disconnect to prevent leakage current and possible galvanic action - this 'eats' anodes. Fit a galvanic isolator to prevent this happening and use solar/wind if possible to keep batteries topped up. However, this won't help with the de-humidifier (unless you're on the hard and then it won't matter).
For info: http://petersmarine.blogspot.com/2009/04/galvanic-corrosion-what-is-it-and-how.html

[Ricd]

Dawntreader this has been my set up for over ten years and there is no evidence of galvanic action consuming anodes excessively either on my boat or adjacent boats. I change saildrive anode once a years (last year only 40g consumed).  Also have a pear anode now on 3rd season. The whole point of the installed battery charger is to charge the bats so they are ready to go when we arrive at the boat.  My engine use is minimal, out of marina and back in again or onto anchor/buoy somewhere.

What circumstances would cause current leakage?

cheers

[dawntreader]

Read the document on the link at the bottom of the page for information about how galvanic erosion is caused. I am not saying you will have an issue but you could have. I have a galvanic isolator fitted. I have only the ring anodes behind the propeller. I changed my anodes for the first time in 2016 @ 75% original weight. This was because erosion had begun to weaken the securing screw fittings (found out this can be prevented by painting). Those anodes were 10 years old. I know others on this forum have reported losing anodes in one season

see this thread: http://bavariayacht.org/forum/index.php/topic,1879.msg11577.html#msg11577

[Salty]

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 The whole point of the installed battery charger is to charge the bats so they are ready to go when we arrive at the boat.  My engine use is minimal, out of marina and back in again or onto anchor/buoy somewhere.
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On a slight change of tack, it’s interesting to read how others treat their battery systems, and I’m not saying that what I do is right, wrong or otherwise, but I don’t keep my engine start battery on charge while I’m away from the boat, and don’t normally charge it up when I visit the boat at weekends unless I start the engine first and run it for a while. I keep my boat on a swinging mooring where there is no shore power to connect to for running the charger anyway.
Over winter while the boat is ashore the mains power supply is always turned off between weekend visits, but is turned on while I’m onboard for one or two days. During that time the battery charger will only be turned on if I think the house or engine batteries need a bit of a boost, but not otherwise.
I do have a 100w solar panel, but this only charges the house batteries and a couple of others that are onboard for specific purpose and are not connected to the engine or house batteries.
I do also have a switched emergency power supply from the house battery for use in the event of the engine start battery going flat, but that system is permanently switched off except in such emergency when it then has to be switched on to be used.
The batteries I have onboard have all been renewed within the last two years or so, but what they replaced had probably been onboard since the boat was new in 2002. I bought it in January 2010, and continued with the same Bosch flooded lead acid batteries until 2015/16.

[Ricd]

Hi Salty
I have an Sterling battery charger that is specifically designed to sense and charge both battery banks independently.  It senses the battery condition and cycles them between charging, float and a desulfation modes over several days in order to maintain optimum battery health.  It only does this if the batteries remain connected to the unit and the unit remains on shore power. If an electrical issue occurs while on shore power either the boat RCD or the shore power RCD will trip.

I guess on a swinging mooring you have little choice.