I know this is a stupid battery question, but I cannot find the answer!

[sailorman]

My 5 boat batteries and my car batteries, apart from the daily runabout, are all on permanent intelligent charge. The boat batteries are all 10 years old and still going strong and I've just changed the car batteries after 10 years.

Walking around my marina in winter in involves avoiding tripping over all the shore power cables powering battery chargers.

Richard

Not powering heaters then

 

[dom]

Your batteries are well up now, why the need to keep them on charge

If batteries were chemically stationary there would be no need. Except they’re not in that all naturally discharge over time, deep cycles often being the worst given their chemistry. The link I referenced above tells us that the OP’s batteries will self discharge to 91% after 3 months and 82% after 6. Trouble will follow if they are left in that state for an extended period of time. BTW loads of batteries in alarm installations, etc. are almost permanently left on a temperature compensated float charge.

 

[sailorman]

If batteries were chemically stationary there would be no need. Except they’re not in that all naturally discharge over time, deep cycles often being the worst given their chemistry. The link I referenced above tells us that the OP’s batteries will self discharge to 91% after 3 months and 82% after 6. Trouble will follow if they are left in that state for an extended period of time. BTW loads of batteries in alarm installations, etc. are almost permanently left on a temperature compensated float charge.

The OP is away for 2 weeks

 

[Kukri]

There’s a history; whilst the boat was laid up for sale the house bank was brought down to 11.1v by the hard wired gas detector over a period of several months.

http://www.ybw.com/forums/showthread.php?504956-A-battery-as-flat-as-Norfolk&highlight=

Hence my fussing over these batteries.

The ex boat with a smaller and simpler set up of two truck batteries and an 8 amp charger was left “plugged in” all winter when laid up because the charger was hard wired to the shore power connection.

 

[dom]

The OP is away for 2 weeks

Sorry, I was combining OP’s post with your marina comments!

Still, leaving isolated batteries for 2 weeks is fine assuming the batteries were fully brought up to a near 100% SOC and this takes time. If not, they’ll be much happier being cycled up and then left on an appropriate temperature compensated float as the OP has now done.

 

[Kukri]

Sorry, I was combining OP’s post with your marina comments!

Still, leaving isolated batteries for 2 weeks is fine assuming the batteries were fully brought up to a near 100% SOC and this takes time. If not, they’ll be much happier being cycled up and then left on an appropriate temperature compensated float as the OP has now done.

Yes, I brought them up in stages, not all at once. Thanks for the encouraging words!

 

[RichardS]

Not powering heaters then

Errrrr ...... it's Croatia. Perhaps you've never heard of it?

Richard

 

[RichardS]

Do you trust a charger left to its own devices in your absence :disgust:

The OP is away for 2 weeks

Ahhhh ..... now it's clear that you meant that it's perfectly fine to leave batteries on permo-charge for longer than 2 weeks. It's just that precisely 2 weeks creates a sort of glitch in the spice-thyme continuum which transmogrifies all batteries into a fifth dimension. :encouragement:

Richard

 

[Kukri]

I think the reason for not leaving paralleled batteries on float charge is that one “bad” battery will cause the charger to “sense” that it “needs” to increase the voltage.

 

[dom]

I think the reason for not leaving paralleled batteries on float charge is that one “bad” battery will cause the charger to “sense” that it “needs” to increase the voltage.

If worried I'd certainly test the batteries independently and also check all of the connections. Depending on the charger algorithm the risk you describe is certainly a possibility. Does your charger have the option to lock it into float mode when you leave the boat?

 

[sailorman]

I think the reason for not leaving paralleled batteries on float charge is that one “bad” battery will cause the charger to “sense” that it “needs” to increase the voltage.

But perfectly ok in Croatia ( whereeverthatis)

 

[RupertW]

Buy perfectly ok in Croatia ( whereeverthatis)

Buy what?

 

[VicS]

Buy what?

I think " Perfectly" is a cheap brand of perfume

 

[sailorman]

Buy what?

See the edit
thats me im off out shooting rabbits now, NV all charged up :encouragement:

 

[Hadenough]

See the edit
thats me im off out shooting rabbits now, NV all charged up :encouragement:

NV? Oh, just looked it up - no validity

 

[Habebty]

Just to add, my AGMs have been on constant charge by a 3 or 4 stage (can't remember which!) at a marina berth or on the hard for the last 14 years (less sailing time ) and seem fine. I believe maintenance charging has contributed to their long life.

 

[halcyon]

I think the reason for not leaving paralleled batteries on float charge is that one “bad” battery will cause the charger to “sense” that it “needs” to increase the voltage.

But you have the same problem during the charge phase, when old batteries may fail to reach hi-charge voltage levels.

Brian

 

[Kukri]

Just to add, my AGMs have been on constant charge by a 3 or 4 stage (can't remember which!) at a marina berth or on the hard for the last 14 years (less sailing time ) and seem fine. I believe maintenance charging has contributed to their long life.

Thank you!