Running boat electrics with a soon to be replaced battery.

[XDC]

Assume a 190ah battery capable of charging to and holding 12.8v but dying after 6 hours of 14 x 10w lights being turned on.

Then being charged and holding 12.8v again.

Turn on battery charger.

Voltage showing 13.9 at switch panel and instrument binnacle.

With the charger ON should the instruments work or drop in and out?

 

[pvb]

Turn on battery charger.

Voltage showing 13.9 at switch panel and instrument binnacle.

With the charger ON should the instruments work or drop in and out?

The instruments should work. Typically, they work down to about 10.5v. But it sounds like the battery is on its last legs.

 

[XDC]

Thanks PVB.

Battery definitely dying.

As a principle would putting a battery charger voltage through a totally knackered battery work?

I'm not suggesting one that's dangerous, just something between the charger and the instruments?

 

[duncan99210]

14 x 10 watt lights equals 140 watts, which is a load of about 11.6 amps. Run for 6 hours, that’s about 70 amp hours or getting on for 60% of the batteries capacity, if it was fully charged to start with. So not too surprising it struggled.

 

[kippers26]

If you think you might need a new battery have a look at eurocarparts black friday deals, 50% discount. I have just ordered a Lion 656 800cca 125a/h for £56.89 nobody local to me has anything that cheap

 

[XDC]

14 x 10 watt lights equals 140 watts, which is a load of about 11.6 amps. Run for 6 hours, that’s about 70 amp hours or getting on for 60% of the batteries capacity, if it was fully charged to start with. So not too surprising it struggled.

Agree the amp hours but not the %.

70ah from a 190ah battery (assuming it HAD 190ah) would leave it well over 50% charged but I ran the test to see just how bad it was and as I said it died after just 6 hours.

 

[XDC]

If you think you might need a new battery have a look at eurocarparts black friday deals, 50% discount. I have just ordered a Lion 656 800cca 125a/h for £56.89 nobody local to me has anything that cheap

Thanks, just looked but 2x190ah batteries very expensive.

 

[PetiteFleur]

Try replacing all your lamps with LED's - MUCH cheaper to run, probably saving 80% of your power. If you have to get new batteries I've used battery megastore in the past.

 

[XDC]

Thanks all but I really would appreciate an answer to #3.

Charger on, dead battery, will the instruments work?

 

[pvb]

Thanks all but I really would appreciate an answer to #3.

Charger on, dead battery, will the instruments work?

As I posted in #2, instruments will typically work down to about 10.5v, if you had 13.9v at the instrument binnacle of course the instruments would work.

 

[QBhoy]

Get those 10w replaced with warm white led, as mentioned. What you have take a load of power to run.
Some lights have 2 10w bulbs in them on occasion even, if it’s the festoon bulbs.

 

[XDC]

As I posted in #2, instruments will typically work down to about 10.5v, if you had 13.9v at the instrument binnacle of course the instruments would work.

Not trying to be picky but they were two different questions. The first regarded a dying battery that still works and powers a fridge, water pump, radio, VHF, lights and instruments.

However it is dropping very low after just a few days hence the comment re "soon to be" replaced.

My second question relates to a totally dead battery.

Will the charger current flow through it and still power the instruments?

 

[XDC]

Get those 10w replaced with warm white led, as mentioned. What you have take a load of power to run.
Some lights have 2 10w bulbs in them on occasion even, if it’s the festoon bulbs.

Thanks but again, that's not what I'm asking.

 

[pvb]

Not trying to be picky but they were two different questions. The first regarded a dying battery that still works and powers a fridge, water pump, radio, VHF, lights and instruments.

However it is dropping very low after just a few days hence the comment re "soon to be" replaced.

My second question relates to a totally dead battery.

Will the charger current flow through it and still power the instruments?

OK, I'll try again. You said in your original post that, with the battery charger on, you had 13.9v at the instrument binnacle. You asked whether the instruments would work. I said they would. I haven't changed my mind.

 

[XDC]

OK, So regardless of the state of battery, anything from totally flat, through soon to be replaced up to brand new, if I'm on charger and I have 13.9v at the instruments the battery state is actually irrelevant?

The charger ignoring the battery?

We're getting close

 

[Molteni]

OK, So regardless of the state of battery, anything from totally flat, through soon to be replaced up to brand new, if I'm on charger and I have 13.9v at the instruments the battery state is actually irrelevant?

The charger ignoring the battery?

We're getting close

Correct :encouragement: The entire boat's electrical system will be at 13.9v. The only proviso is that any high current drain device, like the starter, may not work. But instruments should be fine.

 

[XDC]

So if the battery state is irrelevant any idea why this is happening?

New MFD.

Start up screen insists you need to accept limitations by pressing OK



I never see that screen when the following happens which suggests to me that the MFD is not turning off, but suffering a low voltage.

See what happens. It goes from working fine to appearing to turn off but then recovers through these stages:



No voltage showing on screen





Voltage showing on screen



If it's not my low battery that's on charge any thoughts on what the problem could be?

The MFD has been checked by the commissioning agents and passed as ok and the "power down" of course didn't happen when they were there.

 

[Molteni]

I don't know what the problem is, but 13.9 volts and the combined current from the charger and weak batteries should be plenty to power a plotter (about 2 amps?)

 

[XDC]

I agree but it was suggested that my battery could be causing a problem. This is a battery capable of running a fridge albeit for a decreased amount of time ... but not an MFD, which is why it was so important for me to find out the impact of a dying or dead battery in a circuit being charged. The answer is the battery is irrelevant.

So.....?

 

[[70521]]

Without hoping to be inflammatory, may I suggest that you ask Santa Claus for some decent books on 12 volt DC systems. You are asking some very simple questions and getting a bit upset when the good people of this parish are trying to supply answers.