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Dare I ask? Batteries question...


magictime

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2 minutes ago, WotEver said:

Yup, you’d think so, but it isn’t the case. 

Probably because the plates are actual porous so the effective surface area is the surface area of all the little "granules" throughout the thickness of the plate so one thick plate probably presents a very similar effective surface area to two plates of half the thickness. however not so sure how gassing effects the action within the plates.

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4 hours ago, magictime said:

 

So, we bought our boat six or seven weeks ago, complete with this little lot:

FUPpk-03Sq2BJT4NAE4uZQMtPEFyx-dXeGmdgm7RMJXrFxT3YBTG2TgimCxf2O2Le5Iacg1rmw8NLLA3XCFgeC_L2iO7UqBktGBJIKaMoSWJF6-4sN4Exu68GPkn-H4ldCTF50SN16od9v_sfFepyXwJCT4mc8J9CSMghMiHisnB_jVh483TsIsbGhtMrF_ng8tRQscab_BoEAD4j8BMvSIwBsaFtW_qMdP5xjtFvaqwgOpttAY5lEqqocmV_Q2SCTWncrPrRFrsaH3ol9Eu3P99oYinm7RJ_lOEAHMyGFam2JrfN1mNL8k17zr1rPV-RWek_ZAOvyLAUhGdnrwOMGZCeghg3B3LCLSE4guDM35Cyp4s9qzBcgusyMvCMoQUCHXD0fHJ-ofUl683qnbFiJ0odtSthjeb7pOJjOJ3JUcoqxrCAOASPE5SIGaJWwmWYPXB8EDIR0pv5UNQ3EGvWpSotLE37fWWpITYBYmRy4FsxBLlZzfWQmzdyky6EB8RGd3dQkoWuVDkduQrlft1y84Ogv9E9-4v25ajCHdHwk2URc431EYa1lf0IVpHcb6fXA6qRFqYPj7DgMSimYH2m0Xg23WegJmlLVKx0ucfQE4zZcXSHhQ-BRUpEXY9FyUyRhU4TFDWP050eDKt6CXAuIHyHB_I4L2oXg=w358-h637-no

I've been studiously ignoring them up till now,

Enough said. They are already then knackered. On handover of a boat with the mighty " Trojan " battery installed the previous owner should have informed you of the name and sex of each battery and what sort of bedtime stories they liked. Having not cuddled them each night and not tucked them up in bed as per your admission then they will simply now be beyond saving.

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1 minute ago, Tony Brooks said:

Probably because the plates are actual porous so the effective surface area is the surface area of all the little "granules" throughout the thickness of the plate so one thick plate probably presents a very similar effective surface area to two plates of half the thickness. however not so sure how gassing effects the action within the plates.

On the basis that a starter battery can give up it's charge quicker than a batteries with smaller thicker plates, one might expect the same in reverse. 

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9 minutes ago, rowland al said:

On the basis that a starter battery can give up it's charge quicker than a batteries with smaller thicker plates, one might expect the same in reverse. 

I think it is more to do with thin plates resisting material shedding under buckling caused by high current discharges that may be expected in starter operation. This makes thin plates more suitable for high discharges and perhaps not being more capable of supplying the high discharges (without damage) that thick plates.

We know longer life batteries are those that take extra steps to make the plates resist buckling and shedding.

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4 hours ago, dmr said:

This "only top up when fully charged" thing is way over played. Just get them reasonably charged, that will be fine. Topping up whilst discharged would most likely be ok.

Don't fill them to the top, that will give trouble, about 1/4 inch below the bit of plastic sticking down from the filing holes

Thanks. That's reassuring, and you've correctly gauged my level  of comfort with technical jargon.

3 hours ago, smileypete said:

Those are Trojan batteries, topping up instructions here:

http://www.trojanbattery.com/tech-support/battery-maintenance/

Thanks. Although on balance I think I prefer instructions written in terms of 'bits of plastic sticking down' rather than 'fill wells' and 'vent caps', at least in the absence of a nice labelled diagram.

As for the rest of you... What did I say about this sort of thing?

can-of-worms.jpg

2 minutes ago, ditchcrawler said:

I bet the OP is pleased they asked how to top them up, by now they probably think they are about to fall apart.

I knew the risk I was running! And I think I do feel slightly better about doing the job.

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1 minute ago, Tony Brooks said:

I think it is more to do with thin plates resisting material shedding under buckling caused by high current discharges that may be expected in starter operation. This makes thin plates more suitable for high discharges and perhaps not being more capable of supplying the high discharges (without damage) that thick plates.

We know longer life batteries are those that take extra steps to make the plates resist buckling and shedding.

This is something else I find confusing, Starter batteries have thinner plates so have more surface area for the chemical effect. They are designed to release a lot more energy in a short time than domestic batteries, presumably with little damage on driving a starter motor.

So I would have thought that starter batteries would cope quite happily with low current draw conditions which are more forgiving. 

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4 minutes ago, rowland al said:

So I would have thought that starter batteries would cope quite happily with low current draw conditions which are more forgiving. 

It’s nowt to do with low currents and everything to do with depth of discharge and cycles.

A starter battery is designed to give a high current for a short while, only using a small number of Ah and then be charged straight back up. A traction battery is designed to give up a large percentage of its capacity over a number hours and then be recharged. Treat a starter battery like a traction battery and it will shed, buckle and sulphate. 

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17 minutes ago, magictime said:

Thanks. That's reassuring, and you've correctly gauged my level  of comfort with technical jargon.

Thanks. Although on balance I think I prefer instructions written in terms of 'bits of plastic sticking down' rather than 'fill wells' and 'vent caps', at least in the absence of a nice labelled diagram.

As for the rest of you... What did I say about this sort of thing?

can-of-worms.jpg

I knew the risk I was running! And I think I do feel slightly better about doing the job.

That image is off topic. Belongs in either the recent fishing topic or the one about the great late Italian chef.

Ian.

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Far from being more forgiving, it’s a very harsh life, being a leisure battery. 

That’s why they’re called ‘deep cycle’ Batteries  

 

Edited by WotEver
My phone can’t spell ‘leisure’
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Just now, magictime said:

Okay, one more newbie question: presumably each of the three vent caps on each battery gives access to a separate cell (?) that needs topping up in its own right? They're not just three different access points to one space?

That is correct. Any lead acid battery is made up of a number of cells. Each cell generates approximately 2.1V. So a 6V battery (like those T105s) has 3 cells. A 12V battery has 6 cells. A 24V battery has 12 cells. 

That’s why a 12V battery reads 12.6V when fully charged. 

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4 minutes ago, WotEver said:

It’s nowt to do with low currents and everything to do with depth of discharge and cycles.

A starter battery is designed to give a high current for a short while, only using a small number of Ah and then be charged straight back up. A traction battery is designed to give up a large percentage of its capacity over a number hours and then be recharged. Treat a starter battery like a traction battery and it will shed, buckle and sulphate. 

Yes but isn't it the lower charging and output currents from the thicker plates (less surface area) which give you the more charging cycles?

In effect, aren't domestic batteries just less efficient batteries? With a handle and much more expensive? :)

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3 minutes ago, magictime said:

Okay, one more newbie question: presumably each of the three vent caps on each battery gives access to a separate cell (?) that needs topping up in its own right? They're not just three different access points to one space?

Yes each cell is totally separate. The nature of the lead-acid chemical reaction is that it produces 2 volts. A 12vot battery therefore needs 6 cells to make those 12 volts (2 x 6 = 12). There is another factor that says big cells are better, so your lovely Trojans have only 3 cells each which makes only 6 volts, so they are wired in pairs to make the required 12 volts. A single 12 volt battery with those big cells would be a real bugger to pick up.

As you appear very new to this.....they are full of very bad acid so try not to splash any out as you fill them, wear OLD clothes, wash your hands afterwards. Keep your face well away.  And de-ionised water only, Never use tap water.

...........Dave

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39 minutes ago, rowland al said:

This is something else I find confusing, Starter batteries have thinner plates so have more surface area for the chemical effect. They are designed to release a lot more energy in a short time than domestic batteries, presumably with little damage on driving a starter motor.

So I would have thought that starter batteries would cope quite happily with low current draw conditions which are more forgiving. 

A simple but fairly realistic visualisation of this....

The chemical reaction takes place on the surface of the plates and everytime this happens (every charge and discharge cycle) a bit of the chemical stuff falls off. If you have thin plates then all the stuff has gone in no time at all (about 300 cycles). With nice thick plates then you get maybe 1500 cycles before it has all fallen off. Proper Deep Cycle batteries also tend to be taller so there is more space at the bottom for all this fallen off stuff to go without causing trouble.

............Dave

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42 minutes ago, rowland al said:

Yes but isn't it the lower charging and output currents from the thicker plates (less surface area) which give you the more charging cycles?

In effect, aren't domestic batteries just less efficient batteries? With a handle and much more expensive? :)

Back to my earlier post - the plates are porous on all types so you an not simply think of conventional surface area.

 

I do not see how either type of battery be more or less resistant to sulphation, the chemical process and the hardening over time is the same in both cases. A deep cycle battery is likely to be open cell so can be topped up, this means a higher charging voltage can be used to reverse more sulphation. As someone else has said deep cycle batteries tend to have deeper sediment traps so can shed more material before they short out internally. their plates are also better supported and may be in glass fibre pockets to help keep the active materiel on the plates. The tubular plate designs will resist buckling far better than flat plates.

This is not s simple question about plate superficial surface area. I suspect a starter/leisure/dual purpose battery could be made with a far better cyclic life than those readily available today but it would not be cost effective.

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7 minutes ago, Tony Brooks said:

Back to my earlier post - the plates are porous on all types so you an not simply think of conventional surface area.

This is what a typical lead acid battery plate look like. A lead grid filled with an active paste.

 

images.png

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2 hours ago, dmr said:

A simple but fairly realistic visualisation of this....

The chemical reaction takes place on the surface of the plates and everytime this happens (every charge and discharge cycle) a bit of the chemical stuff falls off. If you have thin plates then all the stuff has gone in no time at all (about 300 cycles). With nice thick plates then you get maybe 1500 cycles before it has all fallen off. Proper Deep Cycle batteries also tend to be taller so there is more space at the bottom for all this fallen off stuff to go without causing trouble.

............Dave

That's a good explaination as to why they can do so many more cycles. However if a starter battery is being used with small loads wouldn't it last longer than if it's used for starting an engine? Is it damaged more just by the number of cycles or is it more to do with the higher energy output when cranking an engine? 

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1 hour ago, rowland al said:

That's a good explaination as to why they can do so many more cycles. However if a starter battery is being used with small loads wouldn't it last longer than if it's used for starting an engine? Is it damaged more just by the number of cycles or is it more to do with the higher energy output when cranking an engine? 

Its the depth of discharge that does the damage, the amount of the lead oxide that gets turned in lead sulphate. A few hundred starting amps for a few seconds only discharges the battery a tiny bit, but a deep discharge has a much greater effect on the chemical changes. There are graphs available for batteries like Trojans which show how long they last against how deeply they are discharged, the deeper the discharge the fewer cycles they can do.

http://www.trojanbattery.com/products/deep-cycle-flooded/signature-line-flooded-2/

.............Dave

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1 hour ago, magictime said:

Well, I just took a look and they don't appear to need even a teensy bit of topping up.

That suggests that they’re probably not getting their preferred charging voltage but something somewhat lower. 

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49 minutes ago, WotEver said:

That suggests that they’re probably not getting their preferred charging voltage but something somewhat lower. 

Qkay... so what would that imply? A problem with the charger, alternator to battery charger, alternator, MPPT controller...?

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1 hour ago, magictime said:

Qkay... so what would that imply? A problem with the charger, alternator to battery charger, alternator, MPPT controller...?

Any of the above really, it depends on what they have been set to deliver by the previous owner. :)

T105’s like 14.8V at 25C, temperature compensated (so higher in cold weather). 

See here:

http://www.trojanbattery.com/pdf/datasheets/T105_Trojan_Data_Sheets.pdf

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On ‎2017‎-‎11‎-‎13 at 14:39, magictime said:

 so I can't see how we can have failed to keep the batteries charged.

Seems that you may have kept up you side of the bargain, but without taking readings you can't really be sure.

Anyway with your small usage of electrics it's plausible that you have not used up much of the water, and if you totally ignored them until now you may not know if they were a bit over topped to begin with?

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