Service Battery capacity.

[ICENI]

I posted earlier regarding the replacement of my two 140ah service batteries in a Bavaria 32 that has been laid up for five years or more before I purchased her..

I recently have recycled the old and heavy batteries despite the difficulty of getting them ashore via rubber dinghy and having to make an telephone appointment with my local recycling.   (Covid 19!!!)   I take recycling seriously but sometimes wonder why I bother!

However, I digress.   My new to me Bavaria sailboat, lays on my swinging mooring in Suffolk UK and although I have improved alternator charging and have a generator on board,, I am aware I will have difficulty in keeping the batteries at or above the desired 12.6volts.   I intend to visit her every 2 weeks during the season.

Having gone through many batteries during my quite long time cruising yachts, now I have returned from Greece to the UK and as I mentioned before she is on a swinging mooring, I am giving a lot of thought to battery capacity.   The refrigerator and coolbox being my biggest concern.   I intend fitting up a gantry with additional Solar energy over this Winter to help.

It would be good to hear from others who are 'off grid' most of the time how they manage.

Bearing in mind the 60amp Valeo alternator can only give so much energy, would it be better to have a second battery bank so I can swop over when needed or add a little more (say 2 more 80ah batteries at this time when the existing two service batteries (connected in parallel) are new?

[Symphony]

If you are planning to keep the boat for a reasonable amount of time then suggest you invest in AGMs, at least for the service bank. Capacity in the region of 200-250 AH is adequate - my 33 has 3*95AH AGMs and I never get near 50% discharge, even running the fridge 24 hours when cruising. Well stocked with bottles of cold water to fill the empty space, the fridge uses around 2.5amps on average, so 60 in 24 hours. The 60amp alternator is not really a constraint as the bank if well charged to start with is limited in its ability to take charge. Even though I have a 115amp alternator, I rarely see more than 25 amps charge. AGMs have very slow self discharge, so leaving them for 2 weeks is not an issue and solar will enable you to recharge during the time away. The only times capacity becomes an issue is if you spend long periods at anchor with no other charging source other than solar, but that does not seem like the way you are going to use your boat.

For the engine start a normal car type battery of around 70AH is more than adequate, although my choice would be a Red Flash 1200. This is small enough such that you could fit 3*AGMs alongside in the battery compartment.

If you don't want to spend that kind of money then a pair of 110AH deep cycle lead acid will fit alongside your engine start battery. I had this on my last boat (a 37) and even with that never experienced capacity problems in "weekend" type sailing.

Worth fitting a battery monitor so that you can keep a check on your usage, as well as adopting power saving things like LEDs for all lights.

[ICENI]

Thankyou Sympathy,

I much appreciate your comments although having just paid out for 2 lead acid, I feel having AGM s now I will do some of your suggestions.

In an earlier post you suggested I remove the original diode block and replace with a BEP cluster.

I intend doing that with possibly an additional switch when I could now add AGM’s in another service bank.

I would appreciate your feelings on this please?

[Symphony]

What capacity are the two batteries you have just bought? Are they big enough as one bank to give you decent capacity? Do you already have a start battery as well?

A gantry just for solar is perhaps overkill on a 32. A simple 100w panel on the coachroof in front of the hatch should be all you need to keep your service bank topped up, even in winter.

[ICENI]

Hi Symphony,

Sorry for the delay in replying.   The two lead acid service batteries are each 140A and as I said, are brand new.

My main concern is the coolbox and fridge which when in the Ionian I found consumed a lot of my battery capacity.   I am aware that now I am in the UK I probably will not find these cooling units will require as much energy, but on a check on the Bavaria galley fridge found the current drain to be around 5 amperes!   The Waeco freezer/coolbox is similar.

I like the Waeco CF50 and it has served me well enabling me to freeze food ready for a week's cruising, taking it down to my boat in my campervan (also with a service battery) so the food is frozen when I go on board.   I use the fridge for milk, cheese etc and fill the unused space with plastic foam.

The fridge at the moment is not functioning, so I am using the Waeco whilst I test for the fridge problem.   It was OK earlier this year and when last functioning was really cold with frost on the cooling unit.   I hope I have not lost coolant and will short out the two thermostat terminals when next at the boat to test the thermostat firstly.

As I am now back on my East Coast swinging mooring and not much chance during the Summer months to use my mains charger, this is why I have the energy concern.
 
I am taking your earlier advice and replacing the Bavaria fitted diode block with a VSR cluster so that will help on the few occasions I am motoring and am definitely going to add Solar panels to bump up my 12 volt capacity and top up the batteries when the boat is left on the swinging mooring.