Jack Posted August 29, 2015 Author Share Posted August 29, 2015 Just picked up the additional addendum's so in the furthering of the science of batteries I will conduct the experiment of the Stress Test once again! Link to comment Share on other sites More sharing options...
Robbo Posted August 29, 2015 Share Posted August 29, 2015 Keep going Jack - we are all waiting for the results, with the hope they prove positive. I've personally learnt a lot during this post, so thanks in particular to Brambles and Brian - a true educational masterclass. Link to comment Share on other sites More sharing options...
Brambles Posted August 29, 2015 Share Posted August 29, 2015 Assuming you tested it and measured the volts under load then at 5.4Amps , 12.5 volts corresponds to about 25 to 30% discharged. Will be nearer 25% discharged 4 hours at 5.4 Amps (which will fall as the voltage falls) is approx 20 A/h so your total capacity is between 60 and 80 Ah and nearer to the 80Ah. It seems fine. When measuring voltage to work out state of charge and hence capacity it is always a bit vague. Link to comment Share on other sites More sharing options...
Brambles Posted August 29, 2015 Share Posted August 29, 2015 With no load then the state of charge voltages when at 75% charge (25% charge removed) are... Flooded approx 12.5 volts AGM approx 12.6 volts Gel approx 12.65 So looking at an 80Ah Gel, 25% dod would be 20AH.. So after 4 hours I would expect to see around 12.5 under load and when removed voltage should settle higher at 12.65volts. There or thereabouts...as I say it is just a rough guide and also temperature dependent. Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 31, 2015 Share Posted August 31, 2015 Brambles - 2015-08-29 9:03 PM Never answered the whole question. Different for Glass or non drip? I don't actually know. I would think it would be much the same and never really given it much thought. Thanks for both Jon. Much appreciated. Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 31, 2015 Share Posted August 31, 2015 Robbo - 2015-08-29 10:56 PM..............................................I've personally learnt a lot during this post, so thanks in particular to Brambles and Brian - a true educational masterclass. Him Master, me pupil! :-D Link to comment Share on other sites More sharing options...
Jack Posted August 31, 2015 Author Share Posted August 31, 2015 Here we go drum roll in the background. Made sure the 'service charge' had been dissipated becoming very technical after this post! Let the battery stand and took first reading 12.94 turned on lights panel showing 4.7 amps. A reading taken hourly as follows:-12.6812.5712.41Let the battery rest for a hour then started again 12.60 lights on same reading on the panel 4.7 amps hourly readings:-12.5812.3212.2312.14My uninformed analysis would say the battery is still functioning at an acceptable level, but what do the experts say?Jack Link to comment Share on other sites More sharing options...
Brambles Posted August 31, 2015 Share Posted August 31, 2015 Before I dive in looking at results in detail (looks fine on 1st glance) did you measure the voltage with the lights on (load on) or switched off, also what was the approx ambient temperature ..a reasonable guess will do 10, 15, 20? Link to comment Share on other sites More sharing options...
Jack Posted August 31, 2015 Author Share Posted August 31, 2015 The readings taken with the lights on. The temperature bit on the chilly side so ??? 15 degrees Jack Link to comment Share on other sites More sharing options...
Brambles Posted September 1, 2015 Share Posted September 1, 2015 I am struggling to find discharge curves that make sense for the Exide G80 (ES900) so have used some typical ones. I have corrected for the load being applied and it ties in with the voltage recovery you had mid way for an hour so fairly confident I am using correct figures. It comes out at 32.9Ah (7 x 4.7) used when voltage indicates 50% discharged - therefore 65.8 Ah is the battery's present capacity. Temperature has a very small effect so can add on a few % so say around 67Ah. You can reduce the expected capacity by a small amount every year and could be anything from 5 to 10% so if you allow say 10% for aging through time its not a bad result at all and your battery appears fine.I have ignored factors like the discharge rate compared to the C/20 rate as you are fairly close to it but it would actually push the new capacity up very slightly. Now what is important is to hang onto these test results you have and then next time you test you have a comparison and can relate back to these results. So in a year you can repeat the test and if the time to reach 12.14 or any of the other voltages is faster then it directly relates to your loss of capacity for your battery.Hope this all makes some sense, stopped making sense to me a few minutes ago so shall post as is and stop editing it!!!!!!!! I will probably read tomorrow and cringe at what I have said. Link to comment Share on other sites More sharing options...
Jack Posted September 1, 2015 Author Share Posted September 1, 2015 Many thanks for confirming that the battery is doing ok. Will keep the info as suggested it will be helpful when I take my A level in battery maintenance!! A very interesting topic. Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 1, 2015 Share Posted September 1, 2015 Brambles - 2015-08-29 8:52 PM Brian Kirby - 2015-08-29 5:47 PM So Jon, what sort of load should be applied for those 5 - 10 minutes to remove the surface charge on gel/AGM type batteries? Would it be different for flooded? Silly question, I guess, but how can one tell if it has gone? It's a bit like hunting the Snark! :-D You need to remove about 1% of the batteries capacity. So for a 100Ah battery that is 1 Ah, so 1 amp for an hour, 2 amps 30 mins, 4 amps 15 minutes. A 60 watt headlight bulb will draw 5 amps so ...12 minutes. a 21 watt lamp is 34 minutes. I have found on worn batteries you can do lot quicker and just watch the voltage as it settles. It will immediately drop when you connect the load, and then slowly drop and settle..then you can disconnect, wait a couple of minutes and measure the voltage again. Apologies for this, but another silly question has struck me regarding surface charge. Would the surface charge not in any case have been removed during these tests? If so, why would it matter if the starting reading included a surface charge that was subsequently eliminated? I accept that it would skew the initial reading, but the second and subsequent readings should be reasonably realistic, so even if the voltage seemed to drop somewhat sharply as the surface charge came off, if what one was looking for was the final reading resulting from a known load over a known period of time, is the initial reading significant? It seems to me that the point of the intermediate readings is to indicate whether the test is worth continuing, in that if the voltage subsides significantly more quickly than it should, the battery is on its way out (or has already departed! :-)). What I think I'm asking is that if one is assessing, say, an 80Ah battery by applying a continuous 5A load for 4 hours, is it safe to simply leave it for the 4 hours and if the Voltage is then about 12.5 Volts (25% DoD), conclude it is OK, but if it is nearer to 12.3 Volts (50% DoD) conclude it should be replaced? Could the test be reduced to that extent? Link to comment Share on other sites More sharing options...
Brambles Posted September 1, 2015 Share Posted September 1, 2015 Hi Brian, Think I understand what you are asking and see the confusion or not as you seem to have pointed out valid points. The initial surface charge in your case of drawing 5 amps will skew the results by about 10 minutes. So in effect the 1st hour should really be 50 minutes for calculating the capacity. After the surface charge is removed and the battery voltage is allowed to settle the voltage reading can be recorded/taken. This is a useful voltage as it gives the initial state of the battery and a low voltage indicates a weak cell or cells. After 25% discharge ( 4 hours) you can indeed get a pretty good idea if it is worth testing further. Indeed just after the 1st hour you get a good idea. But the longer the test is carried out for the more accurate the results and as we can have massive margins of errors in the voltage readings, which may even be down to the voltmeter not being accurate especially if not calibrated. Not sure if I have answered your question! (time for a caffeine fix) Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 2, 2015 Share Posted September 2, 2015 Thanks Jon. What I really had in mind is whether, if being unsure of the reliability of a battery, one could get a reasonable guide to its viability by just putting it on charge for 24 hours and then disconnecting the charger, immediately turning enough lights (assuming not LED!) to give about a 5A load, waiting 4 hours, and then going back, turning off the lights, and measuring the final battery voltage. So, a less less time consuming test than the more detailed one, that would allow folk to get on with other things in the meantime. I think you're saying you could - but the result might not be much use! So, not such a good idea. Thanks again. Link to comment Share on other sites More sharing options...
Jack Posted October 4, 2015 Author Share Posted October 4, 2015 An update. Everything went well on our trip the electrics functioned satisfactorily to a degree. We did have EHU as well as using Aries and I would say that we would have struggled without the supplementary EHU One possibly two days/nights without electricity would be the max for the battery (it did shut down once) then it would need to be charged. Given that our usual usage would be Aires I think two batteries/solar power will need to be a serious consideration for the future. Thanks for the help previously. Link to comment Share on other sites More sharing options...
aandncaravan Posted October 6, 2015 Share Posted October 6, 2015 This is an excellent thread with really easy to follow test advice, but it only tests short term power storage. It does not test leakage (longer term power storage capability) or how efficient the battery is. A simpler way of testing a battery is to buy a device such as a Power Meter (about £17) which measures the power put into a battery. Connect the Power Meter between the Charger and the battery before you charge it up. The Power meter will show in Ah and Watts how much was required to fully charge the battery. Then connect the Power Meter between battery and the 5 amp load and again measure at intervals the voltage drop as per the chart publish by Brambles above. At the end of the test note the Ah given back. Better still wait 2 weeks before applying the load as this will also allow for leakage. The Power Meter style units are designed to be connected between the Solar Regulator and a battery to show how many amps over time (Ah) have been harvested. They keep a running total of the amps, so you can average out the gain over a week. Very simple 4 wire connection, 2 wires in, 2 wires out. They can also be wired between the Solar Panel and the Solar regulator, which is the most efficient way of running them, but the running totals will be lost each day. This is because the Solar regulator isolates the Power meter from the Battery so it's only source of power to run the internal electronics comes from the Solar Panel, which obviously ceases overnight. As well as logging the amps/Ah they are a Voltage display. Very good for diagnosing Solar panel and Regulator issues as they can show both amps/voltage from the regulator to the battery or be wired on the Solar Panel side of the regulator to check it's volts/amps into the regulator. We don't sell them but you can get them here, good service : wsvetlanka@aol.com or 01935 863306. Around £17 incl post. You can get them cheaper but we can recommend this seller. Please note we have no connections with this company. Remember to put a Fuse in the output wire from a Solar Panel before connecting it to a Meter or Solar Regulator. Before you fit a second battery, please see our Schaudt page on the EBL 101's ability to support a bigger battery bank? http://www.aandncaravanservices.co.uk/schaudt-elektroblock.php The Solar power Hints and Tips page, especially in relation to the Schaudt EBL range, might also be useful? . Link to comment Share on other sites More sharing options...
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