Leisure battery

During this winter I have noticed the 12 v. supply to my Devon has been showing red on the control panel and the battery is very low.  I have a 65 w. solar panel fitted.  I do not leave the battery on constant mains charge but switch the charger on and off by hand. How do I test the leisure battery for condition as I believe I cannot use an ordinary starter battery tester.    The battery is still under warranty so hopefully can get a replacement.   When charged it shows 12.7 v. but I do not know about the amperage.

If you can give some more information on what model power control system you have, someone may be able to advise on checking the configuration to make sure that it's set with the correct battery size. On some controllers it will show the capacity available completely wrong if the Ah configured in the controller is different from the Ah of the battery actually fitted.

However, if that's what needs fixing, you will at some point need to confirm the spec of the battery that's in there - generally this will be printed on it somewhere, though this is not always true.

Why can't you use a starter battery tester  ?!

12.7v is indicative of a fully charged battery, but it's only a valid reading if not connected to a charging current from either the EHU or solar panel.
For accuracy, disconnect the positive cable, leave it for an hour, then take a reading.
Keith

There are modern ways of testing batteries but the old fashioned sudden discharge test is not reliable. Unfortunately, the only way to test it at home is to see how it performs on load. Firstly you need to make sure that it is fully charged which for a sealed battery requires around 14.4 volts. A modern system like the Sargent will do this when you are on EHU but if your system is not charging properly then the battery will fail prematurely. It should hold 12.7 volts for a month or so without any load after being properly charged.
There are several other things that can go wrong unfortunately. Solar panel not charging the leisure battery, a load drain somewhere in excess of the normal etc.

Dare-devil-dennis wrote:https://www.amazon.co.uk/gp/product/B0725F2L2G/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Hi Dennis

Still not sure that would be ideal for checking leisure batteries as they are sealed and can be damaged if that's a "quick/heavy" load tester type. We use MK battery testers at work on mobility batteries (virtually same construction as genuine leisure batteries i.e sealed) and a good 90 a/H battery will take anything upto 3-4 hrs to test on our testers. It's not nice when one explodes either!!!

Battery theory is a very complex and hard subject to get one's head around and I've even heard a load of "twoddle and lies" from many a battery expert/manufacturer!!!!!?

HTH's somebody

Best regards all

Molly3 wrote:Why can't you use a starter battery tester  ?!

Hi Molly3

Because starter batteries can and should be tested with the filler caps removed which you can't with proper leisure batteries as they are sealed.

You should also never smoke or cause "sparks" on a newly (not referring solely to NEW but any) charged battery due to the explosive gases batteries give off when charging!!!

Best wishes

This is a microprocessor controlled pulse type tester. The tester does not stress the battery like some, instead it uses fairly sophisticated software to analyse the data ir reads back from the battery as it it put through various test cycles. Testing takes seconds only and a readout gives you the results that can be uploaded if required. I will use it to monitor the battery performance during it's life.

You can see by the size of the unit and it's cables, it ain't gonna hurt the battery, let alone explode it. Easy to use, cheap(ish) to buy and own. It's a clever bit of kit. Stuff on youtube to see

Dennis

Dare-devil-dennis wrote:This is a microprocessor controlled pulse type tester. The tester does not stress the battery like some, instead it uses fairly sophisticated software to analyse the data ir reads back from the battery as it it put through various test cycles. Testing takes seconds only and a readout gives you the results that can be uploaded if required. I will use it to monitor the battery performance during it's life.

You can see by the size of the unit and it's cables, it ain't gonna hurt the battery, let alone explode it. Easy to use, cheap(ish) to buy and own. It's a clever bit of kit. Stuff on youtube to see

Dennis

Hi Dennis

Sooner you than me mate 

If it takes "seconds" to test a leisure battery within the 60 - 110 a/H range it must be putting a strain on something!!!!

Even the testers we use for batteries in the range of 1.2 to 20 a/H cost us £200+ with the MK's in the £400+ mark

I know electronic items are coming down in price all the time but I'd love to compare the results of yours against ours

Best wishes

Hi Wightman,

would you like to borrow it?

A classic case of crossed apples and oranges, Wightman is talking about a load bank that discharges the battery and monitors the output; Dennis is talking about a digital battery analyser. Different animals for a similar task. The load bank results are accurate for that discharge but are dependant on where the battery is in life and charge state. The analyser gives a quick opinion as to the batteries capability. I do like the look of Dennis's analyser but for £50, do I need one?

Of course you do Peter! The one with the most toys when you die - wins! 

I'm going off topic, sorry.

I prize the tools I have, many still from my father' uncle, collected over the years from family and those acqured myself. Chris complains at the storage space but assumes everything can be fixed!

My son, 40 this year, has spent years abroad and still globe trots but has bought a Lotus Elise to play with (lotus club outings, track days, etc). Last week he visited, plied me with favourite grandaughter and asked for trolley jack and torque wrench.

After giving an initial 'no way ' I disappeared into the garage and had a think about what I was likely to do in the automotive engineering field in the future. I sent him off with what he asked plus three toolboxes and more including my dads panel beating hammers and dollies.

BornAgain wrote:There are modern ways of testing batteries but the old fashioned sudden discharge test is not reliable. Unfortunately, the only way to test it at home is to see how it performs on load. Firstly you need to make sure that it is fully charged which for a sealed battery requires around 14.4 volts. A modern system like the Sargent will do this when you are on EHU but if your system is not charging properly then the battery will fail prematurely. It should hold 12.7 volts for a month or so without any load after being properly charged.
There are several other things that can go wrong unfortunately. Solar panel not charging the leisure battery, a load drain somewhere in excess of the normal etc.

I used the following technique to test the capacity. I don’t know how valid it is, but it seems logical to me.

1. Charge the battery fully. I used a CTEK charger.
2. Apply a known load for a known time. I used a 55W headlamp bulb (4.6A) for a fixed time. I used 4 hours. So that was 18AH taken from the battery.
3. Leave it off-load for few hours and then measure the open circuit voltage.
4. From this using various charts on the web determine the charge state of the battery
5. Calculate the capacity. For example if the battery was at 60% charge then 18AH was 40% of its total capacity. So it’s capacity is about 45AH.

It’s good to put it on load for a while and see what happens but unfortunately an exact calculation such as you have done doesn’t work. The capacity relates to a specific discharge current at a specific ambient temperature. Also, you can never fully discharge the battery as it may damage it. The modern testers that measure the battery conductance are very expensive and I am not sure that cheaper ones work properly as there is no way of verifying the result. Usually the best way is to fully charge the battery using a CTek or similar, then check that the voltage holds up at 12.7 volts for a day or two under light load conditions. Usually a duff battery will lose voltage very quickly.

I guess it depends on how you define "Duff'. My 4 ,year old 110AH battery would pass thst test, but whereas it used to last us over a week, it was down to a few days. Good enough for use with regular EHUs or sunny days with solar panels though.