# Leisure Batteries - 90ah is the new 110ah ???



## peejay (May 10, 2005)

I've just read a letter from the C&CC mag and according to an EU directive (2006/66/EC) leisure batteries now have to have their values correctly and more accurately measured using a method called the 20 hour rate. 
Car batteries are apparently already rated this way.

If i've got this right this effectively means that the 2 x supposedly 110ah leisure batteries I bought recently can now only be sold as 90ah or thereabouts.

Q1 - Has the leisure battery market been misleading its customers up until now :?: 

Q2 - Can someone explain the 20 hour rate in laymans terms please :?: 

Pete


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## GEMMY (Jun 19, 2006)

My view on this. Bear in mind that I am a daily mail reader so its probably not to be believed 8O 

In my van I have 3x80 ah.batteries,total 240.My menu control is told 240,but will only charge up to 192 ie.80%

Therefore EU directive will actually give TRUE amount of amperage available.

Now the crunch,if I now buy 3 NEW batteries that are labelled atrue toal of 192 amps then my menu will only charge up to approx 155 amp. 8O 

So do I tell the menu fibs or what?

tony


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## peejay (May 10, 2005)

'tis a good point.

I set my schaudt panel to 220ah when the new batteries were fitted.

They showed as 100% charged but only a 176ah capacity which is about right according to that 20 hour thing.

I've now got a sterling b2b fitted with a remote gauge, do I have to set this to 220ah or 190ah :? :?: 

Pete


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## steco1958 (Mar 5, 2009)

All very confusing, I am sure that somewhere on this site someone will sit down and post a very thorough paper on what you should do.

My advise is you do nothing until you have to purchase a new battery.


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## DABurleigh (May 9, 2005)

Q1 No. And I thought I could be cynical :roll:

Q2 No - I'd just link you to the wiki on Peukert  Fortunately, I know a man who can, and it is all to do with beer, you'll be pleased to hear:
http://www.amplepower.com/pwrnews/beer/

However, I didn't think the battery capacity was yet in UK law. The original date of 29 Sep for implementation was not going to be met, and in any case the UK would have had to have a consultation period. The main change in capacity will probably be due to the proposal stipulating capacity when new. Actually capacity increases with use over the first few weeks. So the battery won't be any different, or perform any differently, but it will just have a slightly smaller number on the label.

Dave
PS Hey, Pete, hope you saw my post on the Brompton design award.


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## andyandsue (Sep 7, 2008)

*its all in the charge rate*

to avoid damage to expensive electronic gear your leisure batts are charged at a lower voltage than they could be so they never reach full charge, u would be ammazed how long a charge lasts if you bench charged em at say 15v on a c tec charger


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## peejay (May 10, 2005)

Thanks Dave, I think I might actually have understood that. It was the beer bit that helped.

So, do I set my shiny new battery monitor to 220ah or 180ah?

Pete

ps - off to look at your brommy post that I appear to have missed.


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## DABurleigh (May 9, 2005)

I wouldn't change anything.

However, one can tinker with many battery monitor settings to, for example, set up the Peukert exponent correctly for YOUR battery, etc. I'd be guided by your monitor instruction manual. The only thing that will be affected is the true remaining capacity when it indicates 50%, say. You don't want to regularly go below a true 50% with bog standard leisure batteries in order to maximise life. But that's a rule of thumb rather than a cliff-edge anyway.

Dave


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## CaGreg (Mar 28, 2007)

Oh dear, where does all this leave us with our single 68AH battery?

Isn't it funny in life, when you don't know something you tend not to worry about it. We swanned off for two years, oblivious to how little battery power we actually had, we wildcamped, we never hooked up at home, we also never had any problems.

Now, knowing how small our battery is, we hook up at home, we are much more careful with our useage when away. 
What has changed? Only our knowledge. I bet if they told bees that their wings were too small, they would develop stronger legs and give up flying altogether.

Ca


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## safariboy (May 1, 2005)

I don't think that anyone answered the question about 20 Hour rate.
This means that the battery is discharged from fully charged over 20 hrs. If you used a smaller current you would discharge the battery over a longer period and could measure the 40 hr rate. It might be expected that this would give the same total capacity but in practice it will give a little more.

Starter batteries are often rated by the short circuit current under specified conditions. (several hundred amps) This is because what matters is that they can give a big kick to the engine. Most of the capacity is actually unused but as max current is linked to total capacity so a bigger current goes with a bigger capacity.


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## peejay (May 10, 2005)

Thanks safariboy, the mist is slowly clearing.

Pete


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## gromett (May 9, 2005)

There is an excellent pdf Here that covers Batteries, chargers and inverters.

"The Capacity of a battery is dependent on the rate of discharge. The faster the rate of discharge, the less the Ah capacity will be available.

In general the rated capacity is for a discharge time of 20 Hours.

For a 200Ah battery the this means that the rated capacity can be delivered at a discharge current of 
200AH / 20H = 10Amps.

With a discharge current of 200Amps the same battery becomes flatter quicker and would have an actual capacity of 100AH and become flat after 30 minutes."

Batteries generally won't give their full capacity from new until it has had a couple of charges so the new legislation will actually mean that batteries will hold more charge than the labels says it will once it has been charged a few times.

Anyway the pdf is interesting reading.

Karl


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## sallytrafic (Jan 17, 2006)

If its changing to 20hrs (or perhaps being standardised) what was the discharge time used before?


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## peejay (May 10, 2005)

sallytrafic said:


> If its changing to 20hrs (or perhaps being standardised) what was the discharge time used before?


Hope you're not directing that to me Frank, haven't the faintest :wink:

Pete


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## gromett (May 9, 2005)

Not sure Frank, all the ones I looked at were rated at 20H but I think the big change is that it is now from new wheras I think some are currently sold at maximum???

Karl


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