Charging leisure batteries effectively

[bizzard]

Your engine battery must be charged up ok or the engine wouldn't start. You could try swapping the batteries around. Swap over a cabin battery with the start battery, but only connect up just that one starter battery as a cabin battery and leave the others disconnected out of the circuit in case they're no good and see how it charges. Mind, the cabin battery might not start the engine which would prove its either no good or it hasn't been charged.

[tommyleyland]

Just having the inverter on shouldn't be a problem, it depends on what the inverter was powering - ie what loads were plugged into the 240. With big loads it's certainly possible for the inverter to take most or all of the alternator current.

 

This is my thinking, it's at 13.5 at the moment which is better than it's been, I was running 2 laptops from an extension socket so that might be the issue...

[James T Berk]

not sure what you are seeking to prove. The start battery will easily stay charged enough to work whilst the domestic bank that actually has to work for a living will never keep up. Remember even a long hard crank to start is only about one amp hour.

[nicknorman]

This is my thinking, it's at 13.5 at the moment which is better than it's been, I was running 2 laptops from an extension socket so that might be the issue...

Have you tried increasing the engine revs?

[bottle]

My laptop chargers are 90 watts, so two would be 180 watts so that is a load of 18 amps on the batteries.

 

Engine on tick-over, you may be lucky to get say 20 amps so that means the batteries were taking 2amps.

 

Will take forever to charge them fully.

 

All the above figures are only given as a guide, each situation, batteries, alternator, inverter, load will make them vary.

[Nickhlx]

Whilst the chargers are 90 watts, that is the max continuous power they are able to provide - the actual power they will be consuming is likely to be somewhat less...

 

Surely charging current at tickover revs will entirely depend on how the alternator is geared ? - Mine produces a max of over 100 amps at low SoC

Edited November 19, 2015 by Nickhlx

[tommyleyland]

Have you tried increasing the engine revs?

 

It's revving quite high at the moment, if it doesn't go over 13.5 I'll bring up the revs.

 

 

My laptop chargers are 90 watts, so two would be 180 watts so that is a load of 18 amps on the batteries.

 

Engine on tick-over, you may be lucky to get say 20 amps so that means the batteries were taking 2amps.

 

Will take forever to charge them fully.

 

All the above figures are only given as a guide, each situation, batteries, alternator, inverter, load will make them vary.

 

Yeah you're right, this is quite embarrassing now...

[Alan de Enfield]

 

This is my thinking, it's at 13.5 at the moment which is better than it's been, I was running 2 laptops from an extension socket so that might be the issue...

 

Lets talk turkey :

 

My lap top draws 1.4 amps at 220v.

W=A x V so that is roughly 308 watts.

 

times that by 2 laptops and you are using 600w.

 

That 600 watts will take roughly 60 amps out of your batteries (via the inverter)

If you have a 60 amp or less alternator and / or it is running at less than optimum revs ( for the alternator, not the engine) you are taking more out of the batteries than you are putting in.

 

Answer - use less laptops, produce more electricity, get a bigger alternator, buy a generator, move onto a serviced mooring or live in a house

[ditchcrawler]

That makes sense thanks. I've left it charging for an hour so I'll see where we're up to in a few hours. Another reason it might not have been climbing is because I may have been drawing too much power whilst charging from the inverter.

Yes that's with the engine ticking over

Edit

Its all been said

Edited November 19, 2015 by ditchcrawler

[Nickhlx]

Really ? I struggle to believe a laptop will ever draw 300+ watts, let alone for any length of time

[tommyleyland]

 

Lets talk turkey :

 

My lap top draws 1.4 amps at 220v.

W=A x V so that is roughly 308 watts.

 

times that by 2 laptops and you are using 600w.

 

That 600 watts will take roughly 60 amps out of your batteries (via the inverter)

If you have a 60 amp or less alternator and / or it is running at less than optimum revs ( for the alternator, not the engine) you are taking more out of the batteries than you are putting in.

 

Answer - use less laptops, produce more electricity, get a bigger alternator, buy a generator, move onto a serviced mooring or live in a house

 

Yup you're right. As I said before I've bought 12v laptop chargers, a generator and Smartguage so you live and you learn!

Well thats two problems, On tickover the output of your alternator will probably be quite low and two you are probably taking it out nearly as fast as you are putting it in. What electrical equipment both 12 and 240 volt is running while the engine is running?

 

I don't use a lot of energy to be honest, I had been running the two laptops off 240 which I know is bad but I've got 12v chargers and a new 12v socket. Other than that it's just 12v lighting, I already use a gas powered fridge so nothing else apart from the water pump.

[bottle]

Whilst the chargers are 90 watts, that is the max continuous power they are able to provide - the actual power they will be consuming is likely to be somewhat less...

 

Surely charging current at tickover revs will entirely depend on how the alternator is geared ? - Mine produces a max of over 100 amps at low SoC

 

Agreed but we are trying to help Tommy understand and sort out his charging problems, I only used the laptop chargers as an example as he mentioned them.

 

I could have mentioned a kettle or a fan heater.

[Alan de Enfield]

Really ? I struggle to believe a laptop will ever draw 300+ watts, let alone for any length of time

 

The laptop draws 2.3 amps at 19.5 volts.

The 'power brick' states that "input at 240v 50hz 1.4 amps"

 

Maybe the manufacturers have got it wrong

[tommyleyland]

 

Agreed but we are trying to help Tommy understand and sort out his charging problems, I only used the laptop chargers as an example as he mentioned them.

 

I could have mentioned a kettle or a fan heater.

 

Oh god no I don't use them!

[bottle]

.mistook post.

Edited November 19, 2015 by bottle

[Nickhlx]

Fair enough, but he should understand that the rating label on a power supply is the max surge spike at switch on for a fraction of a second and the VA rating is what it can produce at 19 volts or whatever its output is.

 

If 90 VA, the max draw will be around 100 watts with inefficiencies, which is around 8 amps at 13 volts DC, and that's only when its working flat out - I reckon a clamp meter would be a good investment at around £20-£30 to see what currents are actually flowing on his system...

[ditchcrawler]

 

Yup you're right. As I said before I've bought 12v laptop chargers, a generator and Smartguage so you live and you learn!

 

I don't use a lot of energy to be honest, I had been running the two laptops off 240 which I know is bad but I've got 12v chargers and a new 12v socket. Other than that it's just 12v lighting, I already use a gas powered fridge so nothing else apart from the water pump.

But they will still be using approximately the same amount of power, the only thing you save is the inverter inefficiency.

[nicknorman]

Laptop power supplies are generally rated to be able to charge the laptop's battery and run the laptop "flat out" at the same time. The steady state consumption with charged batteries, just doing a bit of web browsing etc, will be very much less.

[ditchcrawler]

Fair enough, but he should understand that the rating label on a power supply is the max surge spike at switch on for a fraction of a second and the VA rating is what it can produce at 19 volts or whatever its output is.

 

If 90 VA, the max draw will be around 100 watts with inefficiencies, which is around 8 amps at 13 volts DC, and that's only when its working flat out - I reckon a clamp meter would be a good investment at around £20-£30 to see what currents are actually flowing on his system...

My laptop on charge and in use uses about 3.5 Amps at 24 volts. Thats measured not whats on the label

[Nickhlx]

My laptop on charge and in use uses about 3.5 Amps at 24 volts. Thats measured not whats on the label

 

I imagine that is a recent and possibly high end laptop - what is the power rating of its power supply I wonder ?

[system 4-50]

If the OP is running a significant load off his inverter, his alternator will not see the current to the batteries getting small and will therefore not ratchet up the charging voltage, so the batteries will never be "fully" charged no matter how long the engine runs? Is this true or am I misunderstanding what takes place?

[tommyleyland]

From converting to a 12v laptop charger it's gone from an estimated 625w to 64w. Should make a difference..

Still not getting over 13.5 on charge... Been on that for a while.

[nicknorman]

If the OP is running a significant load off his inverter, his alternator will not see the current to the batteries getting small and will therefore not ratchet up the charging voltage, so the batteries will never be "fully" charged no matter how long the engine runs? Is this true or am I misunderstanding what takes place?

Well I'm not sure the alternator quite works like that, but yes a steady and significant load from the boat will mean the alternator's voltage does not get as hig as it otherwise would do. However I don't think that means the batteries never get fully charged, just that it will take longer. Obviously in extremis with a large load, yes it will stop the batteries ever getting fully charged.

From converting to a 12v laptop charger it's gone from an estimated 625w to 64w. Should make a difference..

Still not getting over 13.5 on charge... Been on that for a while.

If it hasn't changed by 0.1v in an hour, I'd say there is something wrong with the alternator, or its a very old type that had low regulated voltage. Either way I think you will have to address the charging system.

 

However can we just check where you are measuring the voltage? If you are measuring it from some connector in the cabin it could be voltage drop in the wiring that is reducing the voltage. Can you put your meter on the batteries themselves?

[tommyleyland]

Well I'm not sure the alternator quite works like that, but yes a steady and significant load from the boat will mean the alternator's voltage does not get as hig as it otherwise would do. However I don't think that means the batteries never get fully charged, just that it will take longer. Obviously in extremis with a large load, yes it will stop the batteries ever getting fully charged.

 

If it hasn't changed by 0.1v in an hour, I'd say there is something wrong with the alternator, or its a very old type that had low regulated voltage. Either way I think you will have to address the charging system.

 

However can we just check where you are measuring the voltage? If you are measuring it from some connector in the cabin it could be voltage drop in the wiring that is reducing the voltage. Can you put your meter on the batteries themselves?

 

Ok so I've stopped the charging for now as it's not gone up in over an hour but I'm getting a generator tomorrow and the smartguage should come tomorrow so I can pick it up at the weekend and see if it's the alternator that can't charge it high enough.

[Paul C]

If the OP is running a significant load off his inverter, his alternator will not see the current to the batteries getting small and will therefore not ratchet up the charging voltage, so the batteries will never be "fully" charged no matter how long the engine runs? Is this true or am I misunderstanding what takes place?