24v system, new batteries.

[Mark 0810]

It doesn't take much but I'm confused. I had solar panels fitted last week by Narrowboat Solar Systems (who did a great job by the way!) and towards the end they said they don't see many 24v systems. I was surprised as I just assumed it's a 12v system, I've only had the boat a month.

 

I was budgeting on new batteries anyway, as the existing ones look prob as old as the boat 13 years. The guy from the solar company said they're 4 batteries, 2 pairs linked in series then both linked in parallel (or might have been the other way round) As someone who doesn't understand electricity in the slightest, my question is this: if I get 120 Ah batteries will the storage still be 120Ah per battery, or will it be halved due to the 24v system?

 

I'm a cont cruiser so need all the battery storage I can get! Any advice would be appreciated!

 

Thanks. ?

[Chewbacka]

A single battery will be 12v and 120Ah

Two batteries in series (assuming both are 120Ah) will be 120Ah and 24v.

 

Now you might think you have lost 120Ah, but this is because Amp hours is not a proper unit.  If you think in energy it is 

single battery = 1440 watt hours

two batteries will be double at 2880watt hours.  Doesn’t matter if they are in series or Parallel, the energy is still 2880watt hours.

 

Remember that a 24v device will take half the current of a 12v appliance, so for a 100watt appliance a 12v appliance will take 8.3amps and a 24v appliance will take 4.2amps.  So your 24v 120Ahour battery will last twice as long as a 12v 120Ahour battery if you see what I mean.

 

Complicated stuff is electricity.

 

Added - a word of caution, you need to understand what voltage(s) your system is, because if you buy the wrong voltage appliance, then in the worst case you will destroy it and possibly it will catch fire.

Edited August 11, 2019 by Chewbacka

[Alan de Enfield]

If you have 4x 120Ah connected as 24v then you will have a total of 240Ah

 

If you have 2x 120AH connected as 24v then you will have a total of 120Ah

[MtB]

7 minutes ago, Alan de Enfield said:

If you have 4x 120Ah connected as 24v then you will have a total of 240Ah

 

If you have 2x 120AH connected as 24v then you will have a total of 120Ah

 

But as Chewy said, Ah is not really much help. An irrelevance in fact when considering how much energy the battery bank stores. 

 

The energy stored will be exactly the same regardless of whether the four batteries are configured as a 12v bank or a 24v bank. 

 

 

 

[Mark 0810]

Chewbacca, thanks for your swift reply! I thought that the 'missing' 120ah must still be in there, lol! Alan de Enfield's post seems to contradict you though, is that because battery monitors etc only recognise 12volt batteries?

 

[MtB]

Just to expand, the energy stored is AmpHours x Voltage, which gives you WattHours.

 

The same whichever way you join them up. 

[Alan de Enfield]

2 minutes ago, Mike the Boilerman said:

 

But as Chewy said, Ah is not really much help. An irrelevance in fact when considering how much energy the battery bank stores. 

 

The energy stored will be exactly the same regardless of whether the four batteries are configured as a 12v bank or a 24v bank. 

 

 

 

But I answered the OP's question.

[Chewbacka]

1 minute ago, Mark 0810 said:

Chewbacca, thanks for your swift reply! I thought that the 'missing' 120ah must still be in there, lol! Alan de Enfield's post seems to contradict you though, is that because battery monitors etc only recognise 12volt batteries?

 

His answer is correct.

 

2 batteries in series (so 24v) will be 120Ah.

4 batteries connected as two 24v pairs will be 120Ah per pair, so 240Ah at 24v

 

[Alan de Enfield]

4 minutes ago, Mark 0810 said:

Chewbacca, thanks for your swift reply! I thought that the 'missing' 120ah must still be in there, lol! Alan de Enfield's post seems to contradict you though, is that because battery monitors etc only recognise 12volt batteries?

 

It does not contradict Chew's post it says exactly the same.

 

If you connect 2x 120Ah 12v batteries to form a 24v system you will now have a '120Ah 24v system'

[Chewbacka]

2 minutes ago, Alan de Enfield said:

But I answered the OP's question.

You did, but did you think the op would fully understand??

 

[MtB]

3 minutes ago, Alan de Enfield said:

But I answered the OP's question.

 

Yes, but he asked the wrong question!

 

 

[Tony Brooks]

4 minutes ago, Mark 0810 said:

Chewbacca, thanks for your swift reply! I thought that the 'missing' 120ah must still be in there, lol! Alan de Enfield's post seems to contradict you though, is that because battery monitors etc only recognise 12volt batteries?

 

The point is, if you do not want to be working out watts, Amp hours are still relevant because, a  said, the current at 24 volts to do the same job as 12V is half so when you work out the amp hours 24 volt boat will consume half the amp hours a 12V boat would doing the same thing so the 24 volt batteries will last twice as long as the same capacity battery on a 12V boat. Its just a different way of looking at it.

[Alan de Enfield]

2 minutes ago, Mike the Boilerman said:

 

Yes, but he asked the wrong question!

 

 

 

Question : How much is a pint of Theakstons ?

Answer : Whiskey is £4 a shot.

[Mark 0810]

My fridge and freezer are 24 volts, and he's lived on board for 12 years, 240v & 12 volt cigar lighter type sockets all work fine, so for my simple mind the total amount of electric in a 24v 4 battery system will get used at the same rate as a 12v 4 battery system?

 

Cheers

[Chewbacka]

8 minutes ago, Mark 0810 said:

My fridge and freezer are 24 volts, and he's lived on board for 12 years, 240v & 12 volt cigar lighter type sockets all work fine, so for my simple mind the total amount of electric in a 24v 4 battery system will get used at the same rate as a 12v 4 battery system?

 

Cheers

Correct because both systems consist of 4 batteries.

 

added - you may find it useful to browse some old posts concerning battery charging and maintenance otherwise your new batteries will not last long.  Come back when you have more questions.

Edited August 11, 2019 by Chewbacka

[sans allumette]

44 minutes ago, Mark 0810 said:

I was budgeting on new batteries anyway

Hi Mark

 

Welcome to the forum. Once you've got your head round the responses to your 24 volt battery question, then follow the forum link below and read, learn and inwardly digest its contents! It can't be stressed enough just how critical this knowledge is going to be to your future on the canals. ?

 

https://www.canalworld.net/forums/index.php?/topic/95003-battery-charging-primer/&tab=comments#comment-2100390

[Mark 0810]

14 minutes ago, Chewbacka said:

Correct because both systems consist of 4 batteries.

 

added - you may find it useful to browse some old posts concerning battery charging and maintenance otherwise your new batteries will not last long.  Come back when you have more questions.

Thanks all for your input, now to look for suitable batteries!

 

Mark

[Jennifer McM]

While you're having a look around, compare prices with these people https://advancedbatterysupplies.co.uk/product-category/leisure-batteries/agm-leisure-batteries/

 

Next day delivery via Yodel is included. They were really helpful. 

[MtB]

1 hour ago, Alan de Enfield said:

 

Question : How much is a pint of Theakstons ?

Answer : Whiskey is £4 a shot.

 

I need a pint of Theakstons. Barman, how much is your whisky?

 

 

See? Wrong question!

 

 

[Mark 0810]

Three rupees and 27 British pence?!

[ditchcrawler]

19 minutes ago, Mark 0810 said:

Thanks all for your input, now to look for suitable batteries!

 

Mark

Are you sure he ones you have are beyond their useful life

I have a 24 volt system and have 4 Trojan T105 batteries in series, they ate 6 volt batteries

[Mark 0810]

I think so, just by the fact the monitor never shows 100% and will drop to below 80% even if I'm out for the day and only 24v fridge & freezer are on and TV on standby?

[Alan de Enfield]

16 minutes ago, Mark 0810 said:

I think so, just by the fact the monitor never shows 100% and will drop to below 80% even if I'm out for the day and only 24v fridge & freezer are on and TV on standby?

The fact the monitor never shows 100% means you are not fully charging the batteries, that will lead to reduced capacity.

 

Why would you go out for the day and leave the TV on standby ?

Edited August 11, 2019 by Alan de Enfield

[Mark 0810]

Because I always forget to switch off the plug. Having now written this I hope I will remember to do so! But that wouldn't account for such a drop would it?

And however much I leave the engine running battery monitor never goes above 98%.

[Chewbacka]

13 minutes ago, Mark 0810 said:

Because I always forget to switch off the plug. Having now written this I hope I will remember to do so! But that wouldn't account for such a drop would it?

Power is precious on a boat, so minimise consumption, waste nothing and remember because of the chemistry of lead acid batteries even if you discharge them quickly it will still take many hours (maybe 10) to fully recharge.  If you fail to recharge fully and often, then the amount you didn’t recharge will be lost forever,  unfortunately this is cumulative, so continue to fail to recharge and again loose the top bit, continue and again loose the top bit ........

There are people that have destroyed a new set of batteries within a few months.

 

added - I bought a battery discharge meter to see if any of my old Leasure batteries were useable for a bow thruster or engine starting which don’t need lots ofcapacity.  When new they were 110Ah each, before replacement they were between 15 to 20Ah.

So your batteries may be quite low on capacity, so losing 20% of available capacity during the day is more than feasible.

Edited August 11, 2019 by Chewbacka