Replacing leisure batteries

[Alan de Enfield]

12 minutes ago, Tony ralph said:

Looking now for solar panels for my boat. Any recommendations make and model I'll be looking to use around 80 to 100 amps. A nite ? 

Solar panels don't tend to work very well at night (the name sort of gives it away, SOLAR rather than LUNAR)

 

Are you really looking for 80-100 amps ?

If so then you'll be looking for around 1500w of solar panels, but you will only get that for 4 or 5 months in the summer.

 

I'll assume you mean that you will be looking to replace 80-100Ah per day ?

In which case a single 150 watt panel would just about achieve that for (maybe) 4 months of the year.

Even if you went to 1000 watts of panels it would be very unlikely to produce 100Ah per day in the 5 or 6 months of late Autumn, Winter and early Spring.

Edited June 4, 2018 by Alan de Enfield

[Tony ralph]

2 minutes ago, Alan de Enfield said:

Solar panels don't tend to work very well at night (the name sort of gives it away, SOLAR rather than LUNAR)

 

Are you really looking for 80-100 amps ?

If so then you'll be looking for around 1500w of solar panels, but you will only get that for 4 or 5 months in the summer.

Just about to do a bit of a audit

[WotEver]

Buy as many as you can afford both in terms of roof space and wallet. It will be too much in the summer and not enough in the winter. The more you have the shorter the ‘nothing in the winter’ period becomes. 

[Ssscrudddy]

& still expect some days of naff all in the summer when it's miserable

[MtB]

On 04/06/2018 at 12:01, WotEver said:

Buy as many as you can afford both in terms of roof space and wallet. It will be too much in the summer and not enough in the winter. The more you have the shorter the ‘nothing in the winter’ period becomes. 

 

 

Subject to limits. When I expanded my solar from 200w to 560w, the "nothing in winter" period hardly changed. 

 

The big change was the climb from "nothing in winter" to "too much in summer" reduced from about three months to about three weeks. 

 

 

[WotEver]

6 hours ago, Mike the Boilerman said:

 

 

Subject to limits. When I expanded my solar from 200w to 560w, the "nothing in winter" period hardly changed. 

 

The big change was the climb from "nothing in winter" to "too much in summer" reduced from about three months to about three weeks. 

Yes indeed. Even 5kW wouldn’t do you much good in the winter gloom, but it would be like a switch in Feb or thereabouts. 

[Dr Bob]

1 hour ago, WotEver said:

Yes indeed. Even 5kW wouldn’t do you much good in the winter gloom, but it would be like a switch in Feb or thereabouts. 

500W is the limit for me with the room on the roof (and the look) of our 63' NB. Any more and we would look like a mobile power generation site rather than a boat. For me its compromise between looks and practicality (using the roof in locks to get off boat) and power generation.

[Tony ralph]

2 minutes ago, Dr Bob said:

500W is the limit for me with the room on the roof (and the look) of our 63' NB. Any more and we would look like a mobile power generation site rather than a boat. For me its compromise between looks and practicality (using the roof in locks to get off boat) and power generation.

 that's a fair size

How many amps are you replacing I live in a marina  sailing summer 

[MtB]

18 minutes ago, Tony ralph said:

 that's a fair size

How many amps are you replacing I live in a marina  sailing summer 

 

This is a question that makes no sense and suggests you have yet to 'get' the meaning of 'amp', so I'll have a bash at explaining.

 

"Amp" is the unit used to measure electrical current. Think of current as the 'speed' the electricity is flowing at.

 

An analogy with water can be helpful envisioning this. A hose pipe is running. The water coming from the end is flowing at say one litre per second. This is the water current. Wires carry electricity in a similar way (except both ends need to be joined up) and the flow, or current is measured in Amps rather than litres per second.

 

If the hose pipe runs for an hour, it could be used to fill a tank. A battery is the electrical equivalent of the tank. An amp flowing into the battery will only fill it up if left to run for long enough, so battery capacity is measured in amps x hours. AmpHours. Ah for short.

 

So the solar output that can be stored is actually measured in Ah, so your question ought to really ask "how many Ah are you replacing?" 

 

This is however difficult to answer as solar panel output varies widely with the time of day, the weather, and the season.

 

Is that clear? 

 

Thought not.... 

 

 

 

Edited June 8, 2018 by Mike the Boilerman

[Dr Bob]

27 minutes ago, Tony ralph said:

 that's a fair size

How many amps are you replacing I live in a marina  sailing summer 

We are fairly wasteful on power. We try to be the opposite to living in a tent. We normally have a DVR box on (or standby), a sky box on (or standby, plus Rasp pie, TV, hard disk, various chargers, mifi box etc etc so at any one time maybe 5 to 10A going out, depending if the 240V fridge compressor is going. Overnight (with some stuff switched off) we end up with typically -80 to -100Ahrs out of the 660Ahr domestic bank - which then needs to be replaced.

The 500W on a cloudless sunny day will put in circa 30A so the bank is back to almost full with the MPPT controllers switching to float before lunch. This means we dont need to run the engine. Most days Apr-Oct we are moving so run the engine a few hours and most days the sky isnt cloudless. What I find is that with 200W, the power on a cloudy summer day would just about keep up with our hourly demand (say 5Ahr) but with 500W, the extra power is charging the batteries so maybe 5A to 10A is going into the batteries at any one time. This means that even on a cloudy day, with the couple of hours of engine, the batteries are on float by the end of the day. This summer I think we have not had one day when we have not been almost full ie less than -10Ahr and most days the tail current is less than 6A but we have had a lot of sunshine. Last summer with only 200W of panels we had quite a few days that we were short of full.

 

Edit to add. I am switching between Amps and Ahrs to try and explain the difference as per MtB's post which crossed with my post. I think I understood Tony Ralph's question.

Edited June 8, 2018 by Dr Bob

[Richard10002]

With 500w my solar monitor showed almost 2kwh during the day. At 14V this is about 140Ah which is more than I estimate I normally use in a day, but I did leave the inverter on for a few hours to charge my shaver and vacuum cleaner.

[WotEver]

2 hours ago, Dr Bob said:

Edit to add. I am switching between Amps and Ahrs.. 

You might want to do another edit to correct that “5Ah” in the middle to “5A”

[George and Dragon]

3 hours ago, Mike the Boilerman said:

So the solar output that can be stored is actually measured in Ah, so your question ought to really ask "how many Ah are you replacing?" 

 

Watts would be a useful unit if batteries were rated in watts rather than amp hours since the number of watts is independent of voltage. 

 

ETA Stands back and waits for hornets' nest to explode

Edited June 8, 2018 by George and Dragon
.

[Tony Brooks]

1 hour ago, George and Dragon said:

Watts would be a useful unit if batteries were rated in watts rather than amp hours since the number of watts is independent of voltage. 

 

ETA Stands back and waits for hornets' nest to explode

Watt hours, not Watts. Then I might agree but I find Ah does fine.

Edited June 8, 2018 by Tony Brooks

[MtB]

I find AH confusing. I know I shouldn't but I do!

 

I have four six volt batteries in series making up my 24v domestic bank. 

 

A typical four-battery bank of 110ah 12v batteries connected in parallel add up to 440ah. 

 

My bank is only 220ah. Yet the four 6v batteries are 220ah each. To a newbie this will make no sense at all!

[Dr Bob]

2 hours ago, WotEver said:

You might want to do another edit to correct that “5Ah” in the middle to “5A”

mmmmmm.

I agree a 'demand' would be in Amps but perhaps my use of the word demand was wrong. What I was trying to say was that in one hour the batteries would have been depleted by 5 Ahr of capacity...but then you knew that.? ....so I will leave it as it is.?

 

eta....and the edit function has expired....

Edited June 8, 2018 by Dr Bob

[WotEver]

21 minutes ago, Mike the Boilerman said:

I find AH confusing. I know I shouldn't but I do!

 

I have four six volt batteries in series making up my 24v domestic bank. 

 

A typical four-battery bank of 110ah 12v batteries connected in parallel add up to 440ah. 

 

My bank is only 220ah. Yet the four 6v batteries are 220ah each. To a newbie this will make no sense at all!

You have a good point. If you do the calcs in Wh using the nominal voltage (6, 12, 24 etc) then it makes perfect sense.

 

Each of your batts is (nominally) 1320wh. So 4 of them makes 5280Wh. Dead simple. And that’s how much power you have available. 

 

Coverting back to Ah is where it can be confusing. At 6V that 5280Wh would be 880Ah, at 12V 440Ah, and at 24V 220Ah. However, that’s the same amount of power in all 3 systems. So as I said, you make a good point. 

[Tony Brooks]

26 minutes ago, Mike the Boilerman said:

I find AH confusing. I know I shouldn't but I do!

 

I have four six volt batteries in series making up my 24v domestic bank. 

 

A typical four-battery bank of 110ah 12v batteries connected in parallel add up to 440ah. 

 

My bank is only 220ah. Yet the four 6v batteries are 220ah each. To a newbie this will make no sense at all!

But that is the case of almost anything one has little experience of. The individual either has to do some learning or simply stick their head in the sand and I fear far too many want to do the latter. That is not aimed at you Mike.

[Tony ralph]

On 08/06/2018 at 11:44, Dr Bob said:

We are fairly wasteful on power. We try to be the opposite to living in a tent. We normally have a DVR box on (or standby), a sky box on (or standby, plus Rasp pie, TV, hard disk, various chargers, mifi box etc etc so at any one time maybe 5 to 10A going out, depending if the 240V fridge compressor is going. Overnight (with some stuff switched off) we end up with typically -80 to -100Ahrs out of the 660Ahr domestic bank - which then needs to be replaced.

The 500W on a cloudless sunny day will put in circa 30A so the bank is back to almost full with the MPPT controllers switching to float before lunch. This means we dont need to run the engine. Most days Apr-Oct we are moving so run the engine a few hours and most days the sky isnt cloudless. What I find is that with 200W, the power on a cloudy summer day would just about keep up with our hourly demand (say 5Ahr) but with 500W, the extra power is charging the batteries so maybe 5A to 10A is going into the batteries at any one time. This means that even on a cloudy day, with the couple of hours of engine, the batteries are on float by the end of the day. This summer I think we have not had one day when we have not been almost full ie less than -10Ahr and most days the tail current is less than 6A but we have had a lot of sunshine. Last summer with only 200W of panels we had quite a few days that we were short of full.

 

Edit to add. I am switching between Amps and Ahrs to try and explain the difference as per MtB's post which crossed with my post. I think I understood Tony Ralph's question.

Thank you 

Is there a difference between solar panels that people have on their roofs on houses and the Marine type we use on our boats ?

[MtB]

31 minutes ago, Tony ralph said:

Thank you 

Is there a difference between solar panels that people have on their roofs on houses and the Marine type we use on our boats ?

 

They differ in size, but that's about all. 

 

The household solar panels are also connected to a whacking great inverter to change their output into 240Vac too. 

[Tony Brooks]

Nominal 12V panels typically have an open circuit voltage of about 20 volts. Domestic ones are much higher nowadays. If you use an MPPT controller there is probably not much to worry about unless you try to mix panels, then there may be a problem. With a PMW controller a higher voltage panel may not produce the best output. Just be aware and ensure the panel output can not exceed the cotroller's maximum voltage.