Battery Problems

[andrewkirton64@gmail.com]

Mirabeau is a Bavaria 32 (2002).  I've owned her for over 10 years.  I recently experienced, for the first time, a drain on the service batteries.  I think the batteries drained because I left her for over a week with the drinking water pump switched on, with very little water in the tank.  The battery drain occurred despite being hooked up to shore power.  I've recharged the batteries from the engine alternator.  My questions are embarrassingly entry level.

1. Should I expect the batteries to be recharged from shore power?  Is there a problem if this doesn't happen, or is it normal?
2. If the batteries are drained, shouldn't I expect shore power to power the lights and instruments nonetheless? 

I've been under the impression, ignorantly?, that shore power powered all both AC/DC circuits, and recharged the batteries. 

Not wishing to complicate the above, but a previous owner did fit a battery charger/power pack, which I've only attempted to use once.  I switched it to on, whilst connected to shore power, and tripped the shore power fuse on the pontoon. Any guidance on how to use the charger would be gratefully received.

Many thanks.

[symphony2]

If you have a battery charger it should come on automatically when you plug into shorepower unless the installer wired in an on/off switch.

From the way you describe what happens (or rather does not!) suggests you do not have a battery charger. Most chargers make a noise from the fan when they are running so pretty obvious. They are also rather large bits of kit, usually locate in the battery locker or under the chart table. If you have not found it in 10 years, suggests it is not there!

If you do fit one then you need a minimum of 20 amps, although most go for a 25 or 30 for service banks up to around 25 amps. These usually have 3 independent outputs so will charge both the service bank and the engine start battery. Worth fitting a battery monitor at the same time so that you can keep a check on charge and usage.

[fjoe]

How old are your service batteries? Ten years or more would be very old and should be replaced.

To find the failure you should measure the voltages at the battery posts:
- When batteries are charged: VRLA-batteries (AGM or Gel) between 14.4 and 14.8 V, flooded batteries (liquid electrolyte) min 14.8 V,
- Disconnect "fully charged" service batteries, wait 7 hours or more, measure the voltage ("open circuit voltage").
If the battery is in a good condition OCV should be around 12.7 V. If on battery is showing around 10V or less then it has a short in one cell.

Is it possible to check the acid level and acid density of each cell? 
The acid level must never be below the min mark.
A fully charged and healthy cell should have around 1.28 g per cm3 (could be a little less by other physical effects)  A cell with short circuit will show around 1 g/cm3.

[ICENI]

After ten years, even if your batteries have been kept at over 50% charge all the time which is difficult on a sailing boat, I would expect that they are really in need of replacing.   

As Symphony 2 points out there are several excellent 240v battery chargers available for the marine market.   Sterling being one of them and as he stated they will keep both your service bank and the engine battery charged when connected to shore power.

I endorse what Symphony says and get a good battery monitoring system.   I use a Victron BMV712 which is an excellent piece of kit which I wish I had had on board my boat many years ago.
Battery sulfation  is a real problem.  A battery monitor will give you the state of charge of the batteries so you can look after them so much better.

[tiger79]

If you decide to buy a new battery charger, I'd avoid Sterling and buy a Victron.  The Victron BlueSmart IP22 charger is excellent.  A 12v 30A 3-output version is about £200, much cheaper than the Sterling.  It's virtually silent, and you can download the free Victron app so you can monitor the charger on your phone.  It's also less than half the size of the Sterling, so is easily located.

[andrewkirton64@gmail.com]

Thank you to everyone who has responded to my post;  very helpful.

To the question of whether the batteries need changing;  the original batteries were changed some 6-7 years ago, and appear to be in reasonable condition.  I recharged the service batteries from the engine alternator, and have since been sailing.  The batteries are holding their charge.

What I can't get my head around is how the Sterling battery charger/pack works.  As I mentioned in my earlier post, I've only attempted to use it once.  There is an on/off switch.  When I flicked the switch, it tripped the shore power fuse.  This can't be normal can it?!  I've searched google for instructions for the Sterling, but can not find anything that remotely resembles it.  The scant notes that I inherited from the previous owner are not operating instructions.

I will post some photos of the Sterling, to see if anyone can help identify what it is, how to operate it, and why it doesn't agree with the shore power connection.

[dgmultimedia]

The Sterling manuals are here:- https://sterling-power.com/pages/instruction-manuals
but if turning it on trips the Shorepower breaker on the pontoon I suspect the unit either has a fault or is wired incorrectly ( Neutral and Earth swapped maybe )