are all batteries born equal ?

[funflair]

Well the simple answer to that is NO,

I was reading a thread last night regarding perceived and actual battery capacity and got looking at the spec of various batteries, the poster was using a EXIDE ER550 115ah battery, with EXIDE the 550, 900 etc in the description is the available watt hours or in other words the power in the battery before it reaches it's recommended DoD (depth of discharge), now you might expect there to be some reasonable correlation between the more common amp hours (ah) and watt hours (W=VxA) BUT looking at the specifications of EXIDE batteries a 110ah Gel has 1200 watt hours of power/energy where a 115ah lead acid has 550 watt hours of energy. OK the Gel can discharge to 80% vs 50% ish for lead acid but even that doesn't make the numbers add up so there is a lot more going on with the way they deliver the power.

Page 6 is the table but it's all an interesting read.



Oh yes I have GEL.

Martin

 

[jo10000_6]

Hi Martin - so looking at your link I need 3 of my batteries to give me the same power as one of their gels ?

Thanks Jo.



(I’m the poster of the info you were reading. I haven’t read the replies yet - I find I need coffee and a clear head to help with digestion !)

 

[funflair]

Hi Martin - so looking at your link I need 3 of my batteries to give me the same power as one of their gels ?

Thanks Jo.



(I’m the poster of the info you were reading. I haven’t read the replies yet - I find I need coffee and a clear head to help with digestion !)

Yes Jo there were two post running on a similar theme that got me thinking, but yours was the one that mentioned the specific battery, as I say I am a fan of Gel’s but afraid people will get sick of me banging on about them and think I have shares in EXIDE.

Martin

 

[rosalan]

I do believe that overall, although the Gel battery may be superior in some respects, the cost difference weighed against the ownership time of a vehicle, I could be better off buying a quality wet battery.

 

[funflair]

I do believe that overall, although the Gel battery may be superior in some respects, the cost difference weighed against the ownership time of a vehicle, I could be better off buying a quality wet battery.

But the numbers in the table suggest you would have to buy two lead acid to replace one Gel so then the finances don't stack up so well not to mention the weight issue.

Martin

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[autorouter]

BUT looking at the specifications of EXIDE batteries a 110ah Gel has 1200 watt hours of power/energy where a 115ah lead acid has 550 watt hours of energy. OK the Gel can discharge to 80% vs 50% ish for lead acid but even that doesn't make the numbers add up so there is a lot more going on with the way they deliver the power.

They are implying that the maximum discharge is 91% not 80% for Gel, and 40% not 50% for lead-acid.
1200 / (110 x 12) = .909 = 91%
550 / (115 x 12) = .398 = 40%

 

[andy63]

hi martin , just having a quick look at the information you mentioned..
its sales literature at the end of the day and I'm sure they could explain how they came by the figures if challenged.. they are obviously pushing the gel and agm range of their products at the mh market..
at the end of the day power is power and whatever way they state it a watt is a watt ,

so in both cases mentioned you and I would most probably say that a 1200wh battery of lead acid battery type equated to 100ah
and likewise a 550wh battery equated to approx 45 ah..

if they are using different discharge rates to come by their figures again we know that that can materially alter the battery capacity.. but they seem to be stating that everything is based on the 20 hour rate and that's the figure the industry usually use to state the amp hour rate of a battery..
Andy

 

[pappajohn]

It really does get quite anal......

Stick in a couple of 110amp batteries of chosen chemistry.
When they start to go flat charge them up.
When they won't hold a charge replace them.

If you need to calculate to the last hour or last few remaining amps before damaging your batteries it's time to seriously consider only using sites with hookup and forget off grid camping.

Just my opinion.

 

[funflair]

They are implying that the maximum discharge is 91% not 80% for Gel, and 40% not 50% for lead-acid.
1200 / (110 x 12) = .909 = 91%
550 / (115 x 12) = .398 = 40%

That would correct if each battery chemistry exhibited the same voltage at the same discharge but I believe that is not the case as Gel's tend to have a slightly higher voltage than FLA, not sure it is enough to make that difference to the numbers though.

Martin

 

[funflair]

It really does get quite anal......

Stick in a couple of 110amp batteries of chosen chemistry.
When they start to go flat charge them up.
When they won't hold a charge replace them.

If you need to calculate to the last hour or last few remaining amps before damaging your batteries it's time to seriously consider only using sites with hookup and forget off grid camping.

Just my opinion.

That seems to be the important bit though "of chosen chemistry"

Martin

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[funflair]

hi martin , just having a quick look at the information you mentioned..
its sales literature at the end of the day and I'm sure they could explain how they came by the figures if challenged.. they are obviously pushing the gel and agm range of their products at the mh market..
at the end of the day power is power and whatever way they state it a watt is a watt ,

so in both cases mentioned you and I would most probably say that a 1200wh battery of lead acid battery type equated to 100ah
and likewise a 550wh battery equated to approx 45 ah..

if they are using different discharge rates to come by their figures again we know that that can materially alter the battery capacity.. but they seem to be stating that everything is based on the 20 hour rate and that's the figure the industry usually use to state the amp hour rate of a battery..
Andy

Hi Andy

Yes it is "sales literature" but they are all their own products of course and surely there should be some real facts behind the numbers not just make believe.

My only experience of anything other than Gel was when we bought this van and it came with two 80ah G80/ES900 Gel batteries and an inverter, the 240v off the inverter seemed useless so as I had a couple of Elecsol 110ah that were only about a year old and fully charged I fitted them turned on the inverter and the battery voltage plummeted to under 11volts and the inverter switched off, so back to the Old Gel's and at least the voltage held steady even though the microwave was still useless.

The simple answer was that the inverter was quasi sine wave and useless but the Gel batteries were good so they have stayed on for the past 7 years and the inverter was swapped for a PSW and shorter cables.

Martin

 

[autorouter]

My take on these tables is, they are obliged to use the industry standard measure of battery capacity: how many amp-hours at the 20 hour rate until it's 100% flat. Then they say the maximum amount of power (watt-hours) you are recommended to use on a regular basis without causing too much damage. This highlights the difference between gel batteries and lead-acid batteries built for engine starting.

 

[andy63]

how many amp-hours at the 20 hour rate until it's 100% flat. T

The 20 hour rate is based on the ability of the battery to supply said current until its voltage falls to 10.7 v or some such figure..thats what i seem to remember..
Not that that voltage is particularly relevant to us as you would not let your battery go there if you could help it..
As i said battery capacity is such a difficult topic to discuss because as seems to be the case here ..manufacturers cloud the water with their figures...and we as users all have different requirements which can make a nonsense of even honestly stated battery capacities..
As was pointed out bu phil.. @PhilandMena a while back there just is no standard that applies to the industry that allows accurate comparisons, so we all base our opinions on our experiences which all differ..
Andy.

 

[Scotsblood]

I've found this to be particularly interesting;-
http://www.aandncaravanservices.co.uk/campaign-for-battery-change.php
I think we may find out even more as investigations continue and I think some labeling changes are already being seen.

 

[jo10000_6]

The murky world of batteries.

Yes very interesting.

Thank you for posting.

Jo.

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