Correct batteries for a 2005, 36 cruiser

[Bob Mechem]

Can anyone help with the correct battery numbers for a 36 cruiser
The last owner has fitted Halfords, yes Halfords, batteries which are too small and don't fit the clamps so want to go back to original.
We don't have a windlass set up.
Any help gratefully received
Thanks

[Rampage]

Don't think that there's any such thing as a 'correct' battery for boats.  There's the battery that was fitted to the boat when it was first commissioned but that was probably put in by the folk who commissioned the boat, not Bavaria.  Nothing wrong, in my opinion, with a Halfords battery for the engine battery; we have the cheapest one I could source at about 60/70 amp hours for ours (Bavaria 38).  As regards the domsetic batteries, the item fitted in in the boat by the original owners was a wet cell battery of about 120 amp hours; it was inadequate for us, as we live aboard the boat.  In addition, it was under the setee in the saloon, well off to starboard.  I have replaced that with 2 AGM batteries of 180 amp hours each and moved them into the locker in front of the chart table, much closer to the centre line.  These batteries enable us to cruise for about 48 hours without using the engine under the autopilot.

The engine battery is remains under the sette; it was not quite the same size as the original, so I simply moved the clamps to fit it.  The domestic batteries are retained by a couple of ratchet straps with a board over the top of the batteries; this prevents them breaking loose should we be knocked down.

Hope that helps.

[Symphony]

Yes, the original would have been an engine start of 75AH or so and a house battery of 110-120AH, probably Bosch branded. However as said you can change that as you think fit - usually the aim is to increase the capacity of the house bank. In my 37 I was able to get 2*135AH side by side because I found ones that were slightly longer and narrower but with the same terminal locations so that I did not have to change the cables.

[Sweet As]

We fitted 2x150Ahr AGM batteries in our 2004 Bav36. We have also installed a smart regulator that allows the standard 60A alternator to pump them up quickly if they are in need of charge once the engine is running.

A battery monitor has been the other worthy investment. It allows us to keep an eye on the charge level and more importantly get a good understanding of where the demand is coming from.

We have changed all the lights to LED. The next step is to tackle the fridge efficiency (Odysseus has posted good information on this work). I'm struggling to figure out how to most easily and effectively increase insulation levels around the fridge. It is a particularly awkward area of the boat to work in.

[Odysseus]

I have 3 domestic and 1 engine, the engine is 70 AH the domestic are 140AH wet type.

these keep me going for 24 hours sailing after this we are down to 12.2v.
Wet batteries do not like heavy discharge it is better to keep them over the 12v mark the batteries called deep cycle need to be understud as to what the recommendations are, you will be surprised on the limitations that are in the specs. For information batteries were significantly redesigned in the 1950s when lights were no longer mandatory at night for parking cars, so over half the lead was taken out this made the plates weaker therefore prone to buckling during heavy and prolonged discharge. So you need to buy very specialised batteries or remember the limitations of any general wet battery. You should get 5 years out of a set of domestic batteries if you are not you are probably the reason.

Smart chargers, the design and efficiency is very good However can the alternator stand up to this, put your hand on it when it has run for a bit, it gets very hot. I was the manager of the first alternator factory making 40,000 per week (Lucas) and remember well the issues around smart chargers, yes they work but at what cost and do the alternator manufacturer say you can use one? Sorry to be down beat, just still have the scars.

Odysseus

[PhilB]

As previous posts there seems to be no standard. On our Bav 36 we have 4 batteries; 1 engine, 2 domestic and 1 for bow thruster/windlass. I replaced the engine and domestics last year with the following parts from ManBat LFD140 x 2 (140Ah) and D15, both VARTA. These have been perfect and run everything for at least 24 Hrs without significant voltage drop (as has been said most batteries are not very tolerant to being deeply discharged), including diesel heating. I have 2 smart chargers and splitting devices which charge all batteries from shore power or engine. Alternator current is limited by these devices so dont have any overheating issues. I built a battery monitor that monitors all 4 batteries from an onboard PC via USB and displays graphs in realtime which helps to see what is happening - didnt want to pay the extortianate costs of marine kit to do this :-).  Best of luck...

[Anthony]

As said, there are no absolutes about batteries, so long as you have 12v and a reasonable size of amp hours.
I recently replaced my battery bank using 6 golf buggy lead-acid batteries, each being 6volts. Therefore they are mounted in series/parallel to provide 12volts and 270 amp hours in total. Mounted in a 3x2 matrix they fit perfectly in the battery compartment ahead of the nav desk on my Bav40.
I was recommended the golf buggy batteries by a marine electrician as they are designed for heavy duty deep cycle work and being smaller and lighter, do not break your back when fitting or removing them! Retention in heavy seas is achieved by extra saddles screwed into the floor of the compartment,*** obviously be careful with screw length here***, and hardwood timber strakes across the top of the batteries secured with screws to the underside of the seat base.
I also installed a battery monitor giving me % state of charge and replaced all lighting with led's.
All working a treat!

[gtang]

How to determine if a battery went dead?
My battery went low in voltage, I've check and refilled with battery fluid, charge it up to 12.5~13v. but it went low again very quickly.  Is this a sure sign for replacement?

[Odysseus]

A fully charged battery with no drain, should remain above 12.6v  after 48 hours, if it's not, it's duff.

Better to disconnect + to make sure no drain.

Odysseus