Brand new leisure batteries going flat

[Tony Brooks]

I roared with laughter when I saw Terryb's 'greenie' post above

 

I think he must be being rude and suggesting that Boathunter is still wet behind the ears - as in greenhorn.

[WotEver]

1.19ah/h at 5°C in fridge, 25°C ambient.

2.0ah/h at 5°C in fridge, 32°C ambient

Weaco crx80

Mine consumes about 25ah in 24 hours, it's cooler than 25°C on average so the numbers tally.

So as suspected, the 40W 'average' consumption is when the fridge is running. With something like a 25-33% duty cycle we get the 76Ah/day down to your figures.

 

Tony

 

I think he must be being rude and suggesting that Boathunter is still wet behind the ears - as in greenhorn.

Yes he's rude. The difference with Boathunter is that he's learning and correcting himself as he goes along, as witnessed by his latest post in this thread.

[boathunter]

I roared with laughter when I saw Terryb's 'greenie' post above

The thing is, Tony, and Mike, I do know the correct units, but I'm also prepared to lower myself to admitting understanding those that don't without making them jump through hoops or belittling their efforts to understand first. If you actually don't understand the likes of Terry, perhaps you're not as clever as you like to think?

[Paul C]

I've always maintained that 12v fridges are best evaluated by measuring the relevant variables yourself - ie an instantaneous power or current figure while running, a duty cycle and an average (daily) consumption. Fridges vary but so do installations and usage, especially on a boat.

 

Yes 230v fridges are now required to be labelled with an energy efficiency rating and a kWh/annum figure but who is naive enough to think this is invariant for the vast variety of boat installations and users too? Also inverter efficiency and quiescent draw needs to be factored in - so ideally these should be measured too. At least there is a ballpark figure to go on though.

 

I am sure it applies to other loads too, hence a power audit it best done from taking actual readings not just estimates or label values. And should be checked and updated regularly too.

[WotEver]

If you actually don't understand the likes of Terry, perhaps you're not as clever as you like to think?

I can't speak for Mike but I certainly don't think I'm clever. I have a certain knowledge set which I use to reply to posts that lay within my scope and I try very hard to be as accurate and concise as possible within those replies. IF those posts contain clear and unambiguous questions. My knowledge set doesn't include clairvoyance.

Edited September 2, 2016 by WotEver

[MtB]

The thing is, Tony, and Mike, I do know the correct units, but I'm also prepared to lower myself to admitting understanding those that don't without making them jump through hoops or belittling their efforts to understand first. If you actually don't understand the likes of Terry, perhaps you're not as clever as you like to think?

 

 

I have patiently explained on many occasions in threads like this but it's always the same old suspects who aren't willing to read and understand, preferring instead to say stuff like this.

[Tony Brooks]

I can't speak for Mike but I certainly don't think I'm clever. I have a certain knowledge set which I use to reply to posts that lay within my scope and I try very hard to be as accurate and concise as possible within those replies. IF those posts contain clear and unambiguous questions. My knowledge set doesn't include clairvoyance.

 

Pretty much my view as well.

[Johny London]

Look, it's simple. I have a fridge running 24/7, off a victron 3000 inverter, also on 24/7. On average the fridge uses a couple of amps an hour, the inverter maybe 1/2 amp or so. Thats say 60-65 amps of battery current/power call it what you will, in a 24hr day. Lets say with a bit of laptop time, shower pump and led lights - oh and a couple hours using my 240v stereo amp that I'm using 90amps a day.

My batteries are 4x100amp. So I can usefully use maybe 200amps?. Therefore they should easily last a couple days, maybe three if it's not been hot and I haven't been "living like that".

The alternator is 175amp (for the domestic batteries, the starter has its own). I would have thought that the alternator would have put out say 100amps even on tickover, hence I thought a couple hours would be adequate to recharge, given that on many days I have been cruising for a lot longer than 2 hrs.

I didn't have a convenient means of keeping an eye on the state of charge - now I do.

Thinking about it, I got into a bad habit - I frequently had to leave the boat to return to London and attend to my affairs, I would go late morning/early pm, and leave the batteries as they were, ie prolly not that well charged having been using the fridge etc over night. Upon my return always gave the engine a good run because I not only wanted power, but hot water. It had seemed wasteful to run the engine before leaving the boat and the tank of hot water.

We've all had car batteries go dead flat - leaving lights on, electrical gremlins, whatever. Sometimes you recharge the battery and its fine, but usally if its a bit old then a few days later it goes flat again so you buy another one.

These batteries were so new that I assumed they would have a bit of leeway in them, I was quite to prepared to replace them a little early ie 18 month, couple years. I didn't realise they were so fragile. Now, thanks to you all, I do. I was hoping someone would have a remedy or perhaps suggest I had a failing alternator or whatever, that's why I posted. Simples.

I apologise in advance if I've used the wrong units, mis spelt anything or upset anyone in any other pedantic manner

Have to go now as the laptop battery is getting low....

[Alan de Enfield]

you just don't get it, do you?

 

40w average power consumption (over any period you like to nominate) equates to 40Wh per hour.

 

of course the running power may be 80w and it may have a typical duty cycle of 50:50 giving an average of 40w.

 

simples.

 

I do 'get it' - my background is in electrical engineering, originally as a designer of electric wires and cables for the NCB (and wrote many of their specifications), then Aircraft and Military ships wiring, then cable installations. I hold several Patents for cables.

 

My 'paper' qualifications (before the management ones) were all 'electrical' based so I do understand a bit of the theory as well as the 'practical'

 

However I think it is good to play devils advocate and, maybe from the answers given, some people will gradually understand the points made.

[WotEver]

Johny, your basic misunderstanding was to assume that you can put any worthwhile charge into your batteries in 'a couple of hours'.

 

Hopefully now that you can monitor your batteries you will treat them better going forward.

 

Tony

Edited September 2, 2016 by WotEver

[Murflynn]

Look, it's simple. I have a fridge running 24/7, off a victron 3000 inverter, also on 24/7. On average the fridge uses a couple of amps an hour, the inverter maybe 1/2 amp or so. Thats say 60-65 amps of battery current/power call it what you will, in a 24hr day. Lets say with a bit of laptop time, shower pump and led lights - oh and a couple hours using my 240v stereo amp that I'm using 90amps a day.

My batteries are 4x100amp. So I can usefully use maybe 200amps?. Therefore they should easily last a couple days, maybe three if it's not been hot and I haven't been "living like that".

The alternator is 175amp (for the domestic batteries, the starter has its own). I would have thought that the alternator would have put out say 100amps even on tickover, hence I thought a couple hours would be adequate to recharge, given that on many days I have been cruising for a lot longer than 2 hrs.

I didn't have a convenient means of keeping an eye on the state of charge - now I do.

Thinking about it, I got into a bad habit - I frequently had to leave the boat to return to London and attend to my affairs, I would go late morning/early pm, and leave the batteries as they were, ie prolly not that well charged having been using the fridge etc over night. Upon my return always gave the engine a good run because I not only wanted power, but hot water. It had seemed wasteful to run the engine before leaving the boat and the tank of hot water.

We've all had car batteries go dead flat - leaving lights on, electrical gremlins, whatever. Sometimes you recharge the battery and its fine, but usally if its a bit old then a few days later it goes flat again so you buy another one.

These batteries were so new that I assumed they would have a bit of leeway in them, I was quite to prepared to replace them a little early ie 18 month, couple years. I didn't realise they were so fragile. Now, thanks to you all, I do. I was hoping someone would have a remedy or perhaps suggest I had a failing alternator or whatever, that's why I posted. Simples.

I apologise in advance if I've used the wrong units, mis spelt anything or upset anyone in any other pedantic manner

Have to go now as the laptop battery is getting low....

I assume you're taking the pee, deliberately mixing amps and 'amps an hour', and avoiding using amp-hours, such that your explanation is meaningless except for the clairvoyants on this topic.

Edited September 2, 2016 by Murflynn

[Alan de Enfield]

 

The alternator is 175amp (for the domestic batteries, the starter has its own). I would have thought that the alternator would have put out say 100amps even on tickover, hence I thought a couple hours would be adequate to recharge,

 

Unfortunately you are compounding the errors.

 

Firstly it is very unlikely that your batteries are now anything like 4x 100 aH, they are now more proabably 4 x 50Ah, giving you a useful capacity of 100Ah which you are taking out every day. They will not last 2 days - if you do not recharge them properly and fully then they will be totally knackered within a few days.

 

Secondly

An alternator charging a battery doesn't work like that.

The battery limits what it will take, not the alternator 'pushing in' what it is rated at.

You may get 100a for (say) half an hour, then it will drop to 70a for half an hour, then to 50 amps for half an hour, then to 25 amps for half an hour. (figures will vary and are just indicative)

So I suggest that in the above example you would need to run your engine at least 2 hours every day.

 

If I may suggest that you do a little more research on battery charging, how it works and how much more you need to replace than you have used.

[MtB]

I assume you're taking the pee, deliberately mixing amps and 'amps an hour', and avoiding using amp-hours, such that your explanation is meaningless except for the clairvoyants on this topic.

 

 

I couldn't decide if he was taking the pee or genuinely meant it either.

 

But whichever, it is a most monumentally unhelpful and misleading post. Anyone trying to understand 12v electrics would be best advised to ignore it.

[WotEver]

You'll note that I totally ignored all of the figures because they made no sense. I just picked up on the fact that he thought he could recharge >25% of his bank in 'a couple of hours'.

[MtB]

I think its a desperate shame that any answers here that attempt to explain why Amps/hour is wrong and a meaningless term technically, now gets jumped on and subverted by the 'anti-pedants' on here.

 

One cannot help people here now with electrical questions without getting called a pedant, simply for wanting and needing to get the details right. Getting the details right is critical when answering technical questions but sadly the anti-pedants here now seem to treat baiting the pedants as an amusing sport.

[WotEver]

It bothers me not a jot. I simply shan't reply to them.

[MtB]

It bothers me not a jot. I simply shan't reply to them.

 

 

Which is a shame. Johny London's post 108 really ought to be challenged or newbies will take it as legitimate. But I can see it would just continue the downward spiral of accusations of pedantry followed by defences of the need for accuracy.

[Murflynn]

folks should read some basic introductory literature if they intend to try to understand and maintain their boat's 12v system.

 

I can recommend 'The 12 Volt Bible for Boats'

[cereal tiller]

Johny, your basic misunderstanding was to assume that you can put any worthwhile charge into your batteries in 'a couple of hours'.

 

Hopefully now that you can monitor your batteries you will treat them better going forward.

 

Tony

Agreed

 

But,cast off this morning at 7 P.M. ran Engine for a total of 2 hours and 10 minutes

 

Alternators are 2 x 75 AMP with Sterling digital controllers

 

Batteries are 6x 105 A.H. crown 12 Volt batteries

 

Smartgauge read 81 % at first light then 96% when moored up

 

After 30 mins. the Smartgauge settled to 95%

 

CT

[Murflynn]

Agreed

 

But,cast off this morning at 7 P.M. ran Engine for a total of 2 hours and 10 minutes

 

Alternators are 2 x 75 AMP with Sterling digital controllers

 

Batteries are 6x 105 A.H. crown 12 Volt batteries

 

Smartgauge read 81 % at first light then 96% when moored up

 

After 30 mins. the Smartgauge settled to 95%

 

CT

so you've recharged them to the extent of 100 Ah using 2 nominal 75A alternators over a period of 2 hours, i.e. about 30% of the nominal maximum calculated by 75 x 2 x 2.16. Sounds about what I would expect.

[WotEver]

But... That other 5% would take at least another 2 hours, possibly more. And as you know, if you consistently only take them to 95% then they won't last as long.

 

However, even Gibbo posted that batteries are a consumable item and he didn't obsess over their upkeep.

 

Tony

[nicknorman]

 

 

I couldn't decide if he was taking the pee or genuinely meant it either.

 

Well considering the points have been explained extensively on this thread, it was either a deliberate pee take or he is unable to understand fairly simple concepts well explained. Either way, not much point in responding further.

[Paul C]

You can take a horse to water but a pencil must be lead.

[ditchcrawler]

Shoreline Fridges used to have the terminology wrong in all their literature and on their web site, and frequently talked about "amps per hour". They have now realised their mistake and their literature all refers to "amp-hours per hour", as a way of describing the average current taken over a period of time during which the motor will spend some time running (and taking an unspecified number of amps) and some time not running (and taking zero amps).

I thought they did that so it looked like it drew less current than it did

[WotEver]

You can take a horse to water but a pencil must be lead.

Actually it's graphite... oh, sorry, am I being pedantic again