# The secret maths of batteries - new to me!



## Patrick_Phillips (Aug 17, 2006)

2 years and two weeks ago, we bought a set of 110Ah sealed lead acid batteries and guess what. Yep! Two weeks out of warranty they are dead!

Now it seems that everyone else but me knows this…

The problem was that the batteries are only good for about 150 cycles and I have had them all.
I was working on the basis that I had 3 x 110 amps to go at but should leave half of them there to keep the batteries from dying an early death. Actually, the van control panel switches everything off if the voltage dips as far as 11.5v. It has only ever done this once!
So 3 x 110 /2 = 165 amps I can actually use, right? Well, yes but only 150 times.
I actually was using 70 amps a night which was easily replaced by the solar cells before lunch next day. That’s only half a cycle per night so I can have just 300 days before the dear things are curling up their toes – about ten months!!!

Now I am looking for my next set of batteries but I now know to ask “What is the maximum Depth of Discharge (DoD) and how many cycles do you warrant at that DoD?

Guess what? The sellers of batteries are very reluctant to tell me, just like the guy from Sterling Power said they would be…

So thank you Dave Newell and Stirling Power for telling me what I should have known years ago – and I am sure the rest of you did.

Patrick


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## dragabed (May 24, 2008)

try this before buying new ones


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## Techno100 (May 8, 2010)

I like their analysis 
http://www.sterling-power.com/support-faq-2.htm

Using your solar in daytime to charge all your toys will reduce the usage of cycles on your batteries significantly

I favour these on price/performance
http://www.ebay.co.uk/itm/2x-12V-11...ccessories&hash=item3a7193e65b#ht_2331wt_1392


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## Stanner (Aug 17, 2006)

dragabed said:


> try this before buying new ones


Anyways....... Did it work?

I can't stay awake until the video endzzzzzzzzzzzzzzzzzz..........................


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## teemyob (Nov 22, 2005)

*battery*



Stanner said:


> dragabed said:
> 
> 
> > try this before buying new ones
> ...


Inconclusive

Need to check back with him......


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## gnscloz (Oct 4, 2008)

*Re: battery*



teemyob said:


> Stanner said:
> 
> 
> > dragabed said:
> ...


there's loads of videos showing the same, got loads of old batteries at work willbe getting some epsom salt tomorrow we'll do a experiment


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## spatz1 (May 19, 2011)

Patrick_Phillips said:


> Now I am looking for my next set of batteries but I now know to ask "What is the maximum Depth of Discharge (DoD) and how many cycles do you warrant at that DoD?
> 
> Patrick


there are some reasonably priced 110ah that state 500 cycles at 60% discharge and dont expect 165 ah out of 3 x 110ah s because in colder temps you ll be lucky to have over 100 ah s...


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## Patrick_Phillips (Aug 17, 2006)

spatz1 said:


> Patrick_Phillips said:
> 
> 
> > Now I am looking for my next set of batteries but I now know to ask "What is the maximum Depth of Discharge (DoD) and how many cycles do you warrant at that DoD?
> ...


But thats what the motorhome is for - to make sure I am never subjected to those lower temperatures again. 8) :lol:


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## Patrick_Phillips (Aug 17, 2006)

Techno100 said:


> I like their analysis
> http://www.sterling-power.com/support-faq-2.htm
> 
> Using your solar in daytime to charge all your toys will reduce the usage of cycles on your batteries significantly
> ...


But they are only 250 cycle batts. Hope to get better from Numax. They claim 500 cycles. See http://www.ebay.co.uk/itm/12V-110AH...tEquipment_Accessories_SM&hash=item2c60d92d60
Not sure if I trust their rather casual tone though...

Patrick


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## spatz1 (May 19, 2011)

:lol: :lol: 

with your usage and relliance i definately wouldnt bother with 12v and would string (220ah each) 4 x 6v in two sets of parallel to give 440 ah so i wasnt pushing them at 70ah a night...

£126 each on ebay so not much more than 3 x110ah but heavy


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## Pudsey_Bear (Sep 25, 2008)

Anyone got a wiring diagram of the 6v set up, (brain not awake yet) I'll be needing to get new batts for the self build, so might go down that road depending on weight/space available at the time.


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## DTPCHEMICALS (Jul 24, 2006)

I am easily confused by the techie stuff.  

My leisure battery is 6 years old. At home on permanent EHU

Will it last much longer?

Dave p


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## dragabed (May 24, 2008)

ive just changed my 7 year old one


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## Techno100 (May 8, 2010)

Patrick_Phillips said:


> Techno100 said:
> 
> 
> > I like their analysis
> ...


When I contacted them before buying I said theirs looks exactly like the Numax ? they said it is and pretty much said 500 cycles is nonsense.

" You can expect approx 500 re-charge cycles and that's around 3 to 4 times more than regular leisure batteries." IS IT REALLY????? 
No depth of discharge mentioned :roll:

They are both 3 yr warranty so who can prove how many cycles either may do?


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## Telbell (May 1, 2005)

Er...what exactly is a "cycle" and how do you know how many it's had? How do you work it out- especially if you are on ehu (more or less) permanently??


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## rayrecrok (Nov 21, 2008)

Hi.


As Toya Wilcox's would say, "It's a mithstery"..

I have had my leisure batteries a good 6 years with lots of use, and they seem as good as ever.. A few months does not seem reasonable to me, but what do I know!  

ray.


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## Techno100 (May 8, 2010)

In practice you cant really measure or count them due to the way we use them.
If it was a fixed installation of battery powered street light being 50% discharged every night and recharged by solar every day you might stand a chance but even then the length of day/night and Sun make it inconsistent.

generally the longer the warranty the more likely you'll get what you paid for.


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## Telbell (May 1, 2005)

> I favour these on price/performance
> http://www.ebay.co.uk/itm/2x-12V-115AH-DUAL-PURPOSE-LEISURE-BATTE RY-STARTING-AND-DEEP-CYCLING-XV31MF-/251013621339?pt=UK_Campervan_Caravan_Accessories&hash=item3a7193e65b#ht_2331wt_1392


But they're "sealed & totally maintenance free" which Mr Sterling doesn't seem to favour


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## Techno100 (May 8, 2010)

Yes prefers open due to price but if sealed are as cheap?


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## Stanner (Aug 17, 2006)

Techno100 said:


> I favour these on price/performance
> http://www.ebay.co.uk/itm/2x-12V-11...ccessories&hash=item3a7193e65b#ht_2331wt_1392


What do you think of these for the money?
http://www.alpha-batteries.co.uk/bu...-calcium-225amp-leisure-battery/prod_101.html


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## Techno100 (May 8, 2010)

I think they're very good and the only reason I don't consider them is their dimensions.
When I get my Knaus Sun Ti perhaps :wink:


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## pieterv (Feb 3, 2009)

Telbell said:


> > I favour these on price/performance
> > http://www.ebay.co.uk/itm/2x-12V-115AH-DUAL-PURPOSE-LEISURE-BATTE RY-STARTING-AND-DEEP-CYCLING-XV31MF-/251013621339?pt=UK_Campervan_Caravan_Accessories&hash=item3a7193e65b#ht_2331wt_1392
> 
> 
> But they're "sealed & totally maintenance free" which Mr Sterling doesn't seem to favour


Sterling doesn't recommend sealed because using their B2B involves higher charge voltage which will bring the battery to boil and use water, and therefore needs refilling.


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## Stanner (Aug 17, 2006)

Techno100 said:


> I think they're very good and the only reason I don't consider them is their dimensions.
> When I get my Knaus Sun Ti perhaps :wink:


One of those is smaller in volume than two of the 110amp batteries I use now, has fractionally more capacity, more cycles to a lower discharge level (500 @ 50% instead of 250 @70%) only costs about £5 more and will fit in the same space ----

2x - http://www.alpha-batteries.co.uk/bu...-low-height-110l-leisure-battery/prod_92.html

or

1x - http://www.alpha-batteries.co.uk/bu...-calcium-225amp-leisure-battery/prod_101.html

- so should I buy one?


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## Techno100 (May 8, 2010)

Only if your batteries are knackered :wink:


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## rayrecrok (Nov 21, 2008)

Hi.

So if you do not "Deep Cycle" your leisure batteries by keeping them with as much power as possible in them in use and continuously topped up by some means, they should last a lot longer..

Or does it not work like that?.

ray.


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## Techno100 (May 8, 2010)

Correct Ray and solars recover some of the investment cost by helping to achieve exactly that.

People saying they can go 3,4 or 5 days in one place without charging on a regular basis will very definitely get shorter battery life


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## Andysam (May 10, 2005)

Techno100 said:


> I like their analysis
> http://www.sterling-power.com/support-faq-2.htm
> 
> Using your solar in daytime to charge all your toys will reduce the usage of cycles on your batteries significantly
> ...


I've been running those for 18 months now without issue.


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## Andysam (May 10, 2005)

Patrick_Phillips said:


> But they are only 250 cycle batts. Hope to get better from Numax. They claim 500 cycles. See http://www.ebay.co.uk/itm/12V-110AH...tEquipment_Accessories_SM&hash=item2c60d92d60
> Not sure if I trust their rather casual tone though...
> 
> Patrick


They are the same batts. Clones made elsewhere and badged in the country of destination.


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