Battery Advice

[magicaltrout]

7 minutes ago, Jonathan said:

magicaltrout,

If your lights are "older" style incandescent or fluorescent, then each may be using between 8 to 24 (or 32) Watts.  The newer LED bulbs use less energy.  If you have several lights on, the fridge and the TV, then you might be using 10 Amps (120 Watts).  Over 4 or 5 hours that's 40 or 50 Amp-hours, which will hammer a battery and use almost half of its capacity.

|f one battery has been discharged more than the other, then switching to "both" is likely to cause current to flow from one to the other, and that will detract from their ability to start the engine. 

It may be true that the batteries need replacing, but unless you understand how the batteries are wired and how much energy you are taking from them, you may find that new ones are not much better.  Would it be possible to get advice from someone local to your mooring who understands boat "electrics"?

 

Thanks, due to issues cranking when leaving the marina, I deliberately switched everything off and went for a few hours cruising, fridge was off, lights are LED and no TV, I've done the calcs for usual load and I agree, but this was one evening with just lights & radio.

I'll replace the batteries and if it continues as someone that knows! :)

[Paul]

Just testing the voltage of a battery doesn't give a true indication of it's condition. Often a battery will show an output of 12.6 - 12.8v but then when put under load will drop. A decent yard should be able to put a proper tester across them for you in a couple of minutes and see if they need replacing. 

[rightsaidfred]

While not having any expertise where batteries are concerned voltage is largely irrelevant its the drop in amps under load that's more important caused by either a dead cell or in some cases a drop through inadequate cabling, a proper drop test is the way forward.

Fred

[Gordon]

I think you need to break this down a bit

Unparallel the batterys  do them one at a time. What are they showing with no charging. You will be looking for about 12.6V. You will need to then look at the output from the mains charger, it may need a battery to give a voltage but it could bring the voltage up tho over 13 volts if working. Then do the same with the alternator. If all is well measure the other side of the switch with a load, lights etc. That switch could be the villain of the peace  After that you are looking for poor connections early in the circuit. I personally would not be happy with the starter sharing the batterys.

Remember batterys can die in two ways loss of caoacity so the no load voltage might look ok  Or one one more cells short circuit so look for a minimum of 12.6 and at least 13 with either alternator or charger connected.  Slow logical faulting is the way forward.

[StillCruising]

One of the first jobs I did on our boat when we bought it was to upgrade the wiring, Change the batteries and fit a Sterling digital charger. The previous owner had written the date on the batteries and they were only 18 months old but failed due to constant undercharging and probably over discharging.

[annv]

It is also important to check electrolyte level, many so called sealed batteries have a filler cap hidden under the label on top of the battey. John

[Gretzky]

I have a Bayliner with the same config, i.e. a 1-2-both-off master switch. The battery charger when on shore power charges both battey banks. On side 1 I have 3 x 110 Ah batteries and on 2 just a single 110 Ah battery, we bassically just just bank one all the time, but should we ever run that bank too low, I just switch to bank 2 to fire up the engine. Having said that once I upgraded to 3x110Ah batteries I have never run the bank so low I could not start the engine, even after a cold winters night with TV, heating, lighting and fridge on. I found just 1 110 Ah battery just wasnt enough for us.

[magicaltrout]

Thanks @Gretzky

Yeah with 2 single 110Ah batteries its running fine, but I can see how it'd run out of juice pretty quickly. I'm tempted to stick a second battery in as well and run them in parallel on one bank. I'm not sure how I'd get a bank of 3 in there around the engine bay, but worth looking at!

Tom

[annv]

Hi It is best practise to have a automotive battery just for the engine and leisure batteries in one or more banks for everything else, using a split charging system both banks get charged at the same time with most going to leasure bank then no likelihood of forgetting to switch switches,  the engine battery can't then run flat, you will always be able to start the engine. John