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Leisure Battery testing


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So lesuire batteries

 

How do you guys test them.

 

I have four 110ah leisure batteries on a 200watt solar mppt setup. currently waking up to dead batteries in the morning's around 10v DC out !

 

Only thing running in the night hours is the fridge about 3Amps when it is on .

 

Drop test says batteries are fine .... Yes I did take them out for a good few hours after full charge cycle !

 

Don't want to buy new batteries if don't need to.... But wondering if maybe drop test not the right test ?

 

Help !!!! 

 

Thank you for reading 

 

Andy

 

 

 

 

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A drop test only demonstrates that a battery can deliver a high current for a short time. It is in no way an indication of capacity. A badly sulphate battery can act like a good battery that is much much smaller than its original capacity.

 

To test the capacity of a battery you have to fully charge it, then discharge it at a known current either until it is flat, or for a fixed duration (ie extracting x amphours) and then measure its remaining State of Charge by measuring its cells’ specific gravities or its rested no-load voltage.

 

from the sound of it though, your batteries are knackered!

 

Before splashing out on new batteries, check that you charging regime is actually fully charging your batteries. If you just drift along with the batteries getting some charge in a day, but not fully charged, you will rapidly kill the new ones.

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Your batteries are dead, deceased, have shrugged off their mortal coil. Replace them

I would suggest you are actually 'living off the solar' and not the batteries, the solar is 'masking' your battery problem during the day and you only see the reality in the morning, after a few hours without sunlight.

Sort them NOW, you will have big problems in a couple of months when the nights draw in.

 

Drop test is useless and tells you nothing - it is used on starter batteries to tell you if there is enough amps available for a quick 20 second burst of a starter motor - not long term, slow, usage.

 

If you want to test them and get an 'rough' capacity then :

1) Charge them until the tail current is down to 1% of capacity (about 4 amps) at around 14.4-14.6 volts and has not changed for an hour.

2) Disconnect your solar and switch off the battery charger.

3) Switch off all electrical appliances. Add on item with a known wattage (something like an 'old' 55w car headlight is commonly used)

4) Note the time.

5) Leave the 'load' on until the battery shows 12.2 volts, switch the light off, note the time.

 

Deduct the time in 4 from that in 5 to get the elapsed time (lets say 4 hours) multiply the time by the current drawn (in the case of the headlight 4.5 amps) and that gives you 50% of the capacity of you battery bank. You ideally do not want to drop below 50% / 12.2 volts.

 

In this example 4 x 5.5 = 22Ah (for 50% of your capacity)

 

Edit :

Nick types quicker than I do but at least we are both saying the same thing.

 

 

Edited by Alan de Enfield
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Well nearly the same thing. If you discharge as you say, down to 12.2v then the rested no load voltage will be a little higher, say 12.3 to 12.4v. And thus the calculation will be pessimistic. I would discharge to 12v with the expectation of a bounce-back to 12.2v. However in this specific case I doubt it will affect the result, which will be “knackered”, using either method!

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Also re drop testing.

 

Drop or high rate discharge testers need to be matched to the battery capacity/CCA and as most drop testers in the hands of boaters are designed for car the load they put on a battery will be lower than the correct tester so are less likely to show a fault.

 

Today testers usually give the CCA they are designed for and as there is no accurate correlation between CCA and Ah capacity it is all too easy to use the wrong tester.

 

There are three possibilities in the OPs case.

1. the batteries are sulphated an have insufficient capacity

2. one or more cells has an internal short

3. a combination of both.

 

Alan's capacity test is fine as far as it goes but a shorting cell will skew the results but at least it skews them towards the loss of capacity side. If the ends of a battery are bowing out it indicates a high degree of sulphation that I would take as indication enough that the batteries need replacing because of loss of capacity.

 

To test fro shorting cells is easier on open cell batteries because all you have to do is to put them on charge and look into the cells now and again.  Any cell that is bubbling more than the others is suspect, especially if it is hotter, contains discoloured fluid or is venting stinking fumes.

 

Sealed batteries are much more difficult.

 

1 Fully charge as per Alan's instruction except if a cell is shorting you may not get down to a 1% of capacity charge so charge at 14V + until the current fails to fall over an hour. However just getting them well charged will do.

 

2. Disconnect all the interlinks etc. and allow to stand for a couple of hours then take and note the voltage of each battery.

 

3. Leave standing for 24 hours and note the voltage of  each battery. The result should be very similar to the earlier reading and between batteries. Any battery that shows something like more than 0.5v difference is likely to have internal shorts.

 

4. If test 3 looks OK leave to sand for about a week and retest. Again the readings should be very similar to 3 above. Again any major differences will indicate internal shorts.

 

I accept this is all but impossible for liveaboards but you could take one abattery out of service at a time and test it as above. This is why I favour open cell batteries, much easier testing for ordinary boaters.

 

 

 

 

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200 watts solar even in this weather will only put out somewhere around 60 to 70 amp hours into the batteries your fridge in this hot weather will use most of that.  When I only had 300watts of solar that did not keep my batteries fully charged, so I suspect you have been seriously undercharging for some time and now have more sulphate than you want.  10 volts is a killer voltage, you may get a bit of life back once or twice but even then only a percentage of original capacity, several 10 volt days basically means death has occurred.

Edited by Detling
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The extra strong, severe, brutal and rather dramatic method of drop testing a battery goes like so--   Remove battery. Transport it out into the wilderness, far from the maddening crowd, Develop an exclusion zone around you and your battery to keep nosey parkers at bay.  Place the battery upon the ground and remove the stoppers. Don a rubber suit, apron and motor cycle goggles. Grasp hold of a stout steel bar, like a mooring stake. Get iinto a comfortable position and brace up, poised above your battery clutching the stake in both hands. Above all keep nice and calm and take a deep breath.  Get ready, GO!!!! Whack the stake onto both battery terminals at precisely the same moment, causing NO SPARKS!!! which might blow you and the battery up.  Peer into the cells at arms length whilst holding the steel bar on the terminals. The first cell to boil is probably dead or dying, the last cell to boil WAS probably the best one.  On no account must you dither whilst conducting this operation which only takes a few seconds. Withdraw bar sharply, again by causing no sparks.  Dithering about in a nervous state whilst plonking the bar on and off the terminals will probaly cause an explosion.  :)

Edited by bizzard
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1 hour ago, bizzard said:

The extra strong, severe, brutal and rather dramatic method of drop testing a battery goes like so--   Remove battery. Transport it out into the wilderness, far from the maddening crowd, Develop an exclusion zone around you and your battery to keep nosey parkers at bay.  Place the battery upon the ground and remove the stoppers. Don a rubber suit, apron and motor cycle goggles. Grasp hold of a stout steel bar, like a mooring stake. Get iinto a comfortable position and brace up, poised above your battery clutching the stake in both hands. Above all keep nice and calm and take a deep breath.  Get ready, GO!!!! Whack the stake onto both battery terminals at precisely the same moment, causing NO SPARKS!!! which might blow you and the battery up.  Peer into the cells at arms length whilst holding the steel bar on the terminals. The first cell to boil is probably dead or dying, the last cell to boil WAS probably the best one.  On no account must you dither whilst conducting this operation which only takes a few seconds. Withdraw bar sharply, again by causing no sparks.  Dithering about in a nervous state whilst plonking the bar on and off the terminals will probaly cause an explosion.  :)

Thats sort of how I did it in mu youth but used a big file and got away without blowing mu self up, blinding my self of getting covered in acid, I think all the batteries were knackerd anyway from how often I use to bump start. You try finding a hill in Norfolk to park on every time.:apple:

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1 hour ago, bizzard said:

The extra strong, severe, brutal and rather dramatic method of drop testing a battery goes like so--   Remove battery. Transport it out into the wilderness, far from the maddening crowd, Develop an exclusion zone around you and your battery to keep nosey parkers at bay.  Place the battery upon the ground and remove the stoppers. Don a rubber suit, apron and motor cycle goggles. Grasp hold of a stout steel bar, like a mooring stake. Get iinto a comfortable position and brace up, poised above your battery clutching the stake in both hands. Above all keep nice and calm and take a deep breath.  Get ready, GO!!!! Whack the stake onto both battery terminals at precisely the same moment, causing NO SPARKS!!! which might blow you and the battery up.  Peer into the cells at arms length whilst holding the steel bar on the terminals. The first cell to boil is probably dead or dying, the last cell to boil WAS probably the best one.  On no account must you dither whilst conducting this operation which only takes a few seconds. Withdraw bar sharply, again by causing no sparks.  Dithering about in a nervous state whilst plonking the bar on and off the terminals will probaly cause an explosion.  :)

Many years ago we did something similar.

 

At the Gliding club we used old (large) cars, such as Mk10 Jaguars, 3 litre Fords etc, and we needed to see thru the roof to watch what the Gliders were doing as we launched them.

We had some huge truck batteries with very thick cables, one cable was securely attached to the vehicle whilst the other was 'touched' to the roof of the car and as long as you kept moving made a superb 'cutting torch' - however if you stopped moving the cable welded itself to the car and all sorts of nasty things happened.

 

It was as good as Bonfire night.

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I once, I think saved someones eyesight. It was a long time ago when I was an apprentice. It was lunch time and I and another chap, called Dave were there. He'd brought his mother in laws car in to check the battery, a Morris Minor 1000. The battery on those was high up on the middle of the bulkhead behind the engine. I heard a bang and a scream and rushed with enormous haste to his aid. He'd been hanging over the engine testing the battery with a drop tester and must have dithered causing sparks and blew the battery up in his face. He was a big chap and fought me like a drowning man as I tried to drag him to the stand pipe water tap nearby. My adrenalin ran big time doubling my strength and I managed it after a big struggle, got him in a head lock and on to his back on the ground with his head face up under the tap and turned it full on to deluge water over his face. He kept his eyed tight shut which I had to get open. It took both hands to force his eyes open to enable the water to flush out the acid, all the time he was struggling and hollering. In the end Dave survived ok, with no damage, especially his eyes. He bought me 1/2 oz of baccy for saving them.   This is perfectly true.

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43 minutes ago, ditchcrawler said:

Thats sort of how I did it in mu youth but used a big file and got away without blowing mu self up, blinding my self of getting covered in acid, I think all the batteries were knackerd anyway from how often I use to bump start. You try finding a hill in Norfolk to park on every time.:apple:

Yes DC. I've done it the harsh way, with a bar a few times when called out to a non starter, and forgotten my teast gear. But very briefly to determin a a dead cell in a cars battery.

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If its lamp swinging time related to the topic. When I was an apprentice at a Dagenite battery agent we (I) used to hacksaw the posts and cell interlinks off the old batteries before sending them for scrap. The lead was then melted and recast into rods for use when building second line new batteries or re-plating old cases. In those days the interlinks were external and really chunky. Being young I though why cut just one point at a time when careful lining up of the hacksaw bald would do three or four. The short circuit ob good cells and the bang that followed was inevitable.

 

When re-burning posts  that were damaged by loose & arcing terminals or posts that were for some reason a bit undersized the standard procedure was to de-gas the battery by removing all the cell tops, carefully blow into each cell and then stand well back and run the town gas-oxygen lead burning porch across the cells. We never     got even a small pop but I wonder what the 'elfs & safety would say about that now.

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5 hours ago, nicknorman said:

A drop test only demonstrates that a battery can deliver a high current for a short time. It is in no way an indication of capacity. A badly sulphate battery can act like a good battery that is much much smaller than its original capacity.

 

To test the capacity of a battery you have to fully charge it, then discharge it at a known current either until it is flat, or for a fixed duration (ie extracting x amphours) and then measure its remaining State of Charge by measuring its cells’ specific gravities or its rested no-load voltage.

 

from the sound of it though, your batteries are knackered!

 

Before splashing out on new batteries, check that you charging regime is actually fully charging your batteries. If you just drift along with the batteries getting some charge in a day, but not fully charged, you will rapidly kill the new ones.

 

5 hours ago, Alan de Enfield said:

Your batteries are dead, deceased, have shrugged off their mortal coil. Replace them

I would suggest you are actually 'living off the solar' and not the batteries, the solar is 'masking' your battery problem during the day and you only see the reality in the morning, after a few hours without sunlight.

Sort them NOW, you will have big problems in a couple of months when the nights draw in.

 

Drop test is useless and tells you nothing - it is used on starter batteries to tell you if there is enough amps available for a quick 20 second burst of a starter motor - not long term, slow, usage.

 

If you want to test them and get an 'rough' capacity then :

1) Charge them until the tail current is down to 1% of capacity (about 4 amps) at around 14.4-14.6 volts and has not changed for an hour.

2) Disconnect your solar and switch off the battery charger.

3) Switch off all electrical appliances. Add on item with a known wattage (something like an 'old' 55w car headlight is commonly used)

4) Note the time.

5) Leave the 'load' on until the battery shows 12.2 volts, switch the light off, note the time.

 

Deduct the time in 4 from that in 5 to get the elapsed time (lets say 4 hours) multiply the time by the current drawn (in the case of the headlight 4.5 amps) and that gives you 50% of the capacity of you battery bank. You ideally do not want to drop below 50% / 12.2 volts.

 

In this example 4 x 5.5 = 22Ah (for 50% of your capacity)

 

Edit :

Nick types quicker than I do but at least we are both saying the same thing.

 

 

 

In addition to the great advice above, to measure the battery capacity accurately, the battery needs to be discharged at an appropriate rate.  The 20 hour rate will work for leisure batteries, so 5 amps is charge per 100 Amp-hour of battery capacity. You also need to increase the load back to the 20 hour rate, say every 30 minutes, to cater for falling voltage as the battery discharges. 

 

To heavy a discharge will depress the battery voltage and give a false (low) capacity reading (Peukerts).

 

However, as others have said, your batteries sound knackered anyway, so you may wish to concentrate on learning how to fully charge batteries, and then only when you understand that, buy new ones, thus ensuring the new batteries don't rapidly go the same way as the old ones.

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11 minutes ago, cuthound said:

 

 

In addition to the great advice above, to measure the battery capacity accurately, the battery needs to be discharged at an appropriate rate.  The 20 hour rate will work for leisure batteries, so 5 amps is charge per 100 Amp-hour of battery capacity. You also need to increase the load back to the 20 hour rate, say every 30 minutes, to cater for falling voltage as the battery discharges. 

 

To heavy a discharge will depress the battery voltage and give a false (low) capacity reading (Peukerts).

 

However, as others have said, your batteries sound knackered anyway, so you may wish to concentrate on learning how to fully charge batteries, and then only when you understand that, buy new ones, thus ensuring the new batteries don't rapidly go the same way as the old ones.

and if your battery is in good nick it will take you all day and you will be bored senseless. I know

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