Author Topic: Load Testing big deep cycle batteries  (Read 7883 times)

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DoctorCon

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Load Testing big deep cycle batteries
« on: December 30, 2008, 12:48:34 PM »
Hello all,

I am new here (this is my first post) but have been lurking in the shadows of the board for a couple of years, hopefully slowly gaining enough knowledge and courage to finally get into the practical side of this RE stuff...

AND it has happened!

... I have just bought a couple of solar powered flip-dot message boards which are to my wife and mother-in-laws horror are now parked outside my house - "AUCTION MADNESS" they shout.

BUT method in the madness there is me-thinks...

x10 BP solar 75/80 watt panels with frames, x2 AERL 800BLV maximisers (MPPT no less)

x2 large traction battery chargers, x2 12v hydraulic lift units

x12 trojan J185 deep cycle batteries, various 12v low-voltage disconnect units, switches, relays, GSM modems etc, lots of flip dot LED thingies

and two heavy duty trailers

ARE now mine ALL mine I laugh maniacally back at them.

Sooo,


  • the panels I understand and am cleaning etc ready for fitting to my little getaway shack roof (the single 80 watt I currently have will be lonely no more)
  • the regulators are a real bonus - am planning to use 3 x 3 panels in series through one (probably jumpered to 12v) and keep the other for backup/shed light battery/hydropower plaything?
  • the trailers might "come in handy" (just need to hide them somewhere from the wife and m-i-l).
  • those big black painted aluminium 6 square metre perspex front message sign boxes are begging for some recycling as ?solar hot water heater collectors?
  • 12v hydraulics, maybe a blocksplitter? or frame tracker mech on the roof?
  • flip dot LED thingies - I don't know yet - they look "useful", any suggestions?


BUT what about those batteries


  • they LOOK awful covered in corroded clamp frettings, but those panels have kept them charged, the 2 x 6 battery (in parallel) strings return 12.74v on my meter
  • only one was underfull and it needed 2 litres of water to cover the plates
  • can't check the SG (my hydrometer went astray with my home brew kit I think maybe the wife and m-i-l at work again)
  • they sort of intermittently run the signs if you rattle the computer connectors for a while


How do I load test these (hopefully close to 195aH) brutes and interpret the results - at ?60kg each I'd like to know if they are OK before moving them,

Any suggestions for all these other thingies?
« Last Edit: December 30, 2008, 12:48:34 PM by (unknown) »

Boss

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Re: Load Testing big deep cycle batteries
« Reply #1 on: December 30, 2008, 07:38:18 AM »
Good question on the load test for deep cycle batteries. With automotive batteries a load test is just what it sounds like: a certain load is placed on the battery for a particular period of time. It has been a while since I worked in a auto repair shop, but I remember the load tester getting very hot, kind of like our dump load devices. The battery passed if it could handle running the shunt resistor for a couple of minutes, I think.    


!2 volt hydraulic system. What are the specs? How much fluid can it pump?

I built this log splitter several years ago from a tire change lift



Next project after I get done paying for it, is to put a flat bed on the Dodge Diesel Cummings truck I'm buying, I have the bed, but i don't think the truck has a PTO (power take off) so 12 volt hydraulic system may be the way to go.

 

« Last Edit: December 30, 2008, 07:38:18 AM by Boss »
Brian Rodgers
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thirteen

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Re: Load Testing big deep cycle batteries
« Reply #2 on: December 30, 2008, 11:09:13 AM »
I would separate the battery that took all of the 2 liters of water and charge it just by it's self. Is it possible it was tipped over and may have lost some of its fliud.  Maybe it was the first one in line and took the blunt of over charging. A poor battery will drag the others down. You might separate them when they get cleaned and check each one and record the findings. Voltage, fluid level, post connection conditions. Just some ideas.

Could the worst of the two trailers be used for the truck bed?? Could one of the trailers be fixed so it could used as a movable flower bed for the wife and her lovely mother. Just a question to try and ease the hassele of your treasured findings. Sounds like you have made a good deal for you. The solar panels will be able to keep the batteries up and in turn that might just be able keep a small refigerator cold enough for some liquid refreshment. Besy of luck. Just some ideas to ponder.  
« Last Edit: December 30, 2008, 11:09:13 AM by thirteen »
MntMnROY 13

mgtd

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Re: Load Testing big deep cycle batteries
« Reply #3 on: December 30, 2008, 02:33:30 PM »
DoctorCon--Funny you should post this at this time.  I am currently negotiating with a private party for 2 trailers very similar to what you just obtained.  The 2 trailers I'm considering have 8 55w Siemens panels on each unit.  Total of 16 panels for total wattage of 880w.  I want to add that to my existing 860 watts of solar.  I'm also considering what can be done with some of the residue, once I strip the panels from the trailers.  I'd like to PM you, but this board doesn't seem to have that capability amongst members.   I'd be interested in what you paid for yours, relative to what I'm trying to get these for.  If you'd care to privately email me, please do so at xpag@nemr.net.  Maybe we can share our trials and tribulations on this.
« Last Edit: December 30, 2008, 02:33:30 PM by mgtd »

DoctorCon

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Re: Load Testing big deep cycle batteries
« Reply #4 on: December 30, 2008, 06:59:15 PM »
Thanks everyone for your comments:


  • mgtd, I am in Australia so am not sure how relevant the price of the trailers ($2200 but dont tell the wife) would be to you (where are you?)
  • Boss, I love the blocksplitter and know that Christmas has just gone but if I am good could you build me one for next year to go with a new hydrometer? (PS dont ask the wife or m-i-l if I've been good)
  • Thirteen, The "dry" battery is indeed the first in the charge string from the panels - so I guess it has boiled down related to higher resistance in the rest of the corroded parallel harness (it couldn't spill without the others also spilling). I disconnected it from the string after filling and doing a mains power charge from the inbuilt unit (with lots of bubbling going on) and it too is now showing 12.7v on the meter after an overnight rest.


But this is partly why I am a little concerned - I reckon this battery, if any, is most likely to be a problem but it will show 12.7v on the meter.


I need some practical way of load testing them before transport to my little retreat. What do you think about a string of 12v headlights - I think I have some 55w or maybe a 100w lamp somewhere. After I separate and clean them up, could I run a lamp from each battery for a whiles? Should I just run them for 30mins, an hour (or two, or more??) and record the end of test voltage, or run them until the voltage hits a certain level and record a "time-to-drop-x-volts" for each battery.


My problem is I don't quite know how I would interpret the results - I reckon it would tell me which batteries were "best" but even the "best" might still turn out to be a dud. Does anyone have a practical solution or hints / formula for what kind of load / how long to apply etc and ideas on interpreting the results?

« Last Edit: December 30, 2008, 06:59:15 PM by DoctorCon »

TomW

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Re: Load Testing big deep cycle batteries
« Reply #5 on: December 30, 2008, 07:06:41 PM »
Your Photo:



Tom

« Last Edit: December 30, 2008, 07:06:41 PM by TomW »

DoctorCon

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Re: Load Testing big deep cycle batteries
« Reply #6 on: December 30, 2008, 07:13:55 PM »
Thanks Tom - newbie gremlins! My brain failed its load test.
« Last Edit: December 30, 2008, 07:13:55 PM by DoctorCon »

zeusmorg

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Re: Load Testing big deep cycle batteries
« Reply #7 on: December 31, 2008, 01:39:39 AM »
 Load testing is only one way to ascertain the State of charge. You apply a load that is 3X the AH rating for 15 seconds and watch the battery voltage.  A drop below 9.5 V. on a 12 v battery indicates a bad SOC. This test is properly performed after a battery has been fully charged and has been at rest for several hours, but it can be done with a 75% charge state, or higher.


 I would buy a good quality hydrometer as this is the best way to determine SOC. Most people do not have access to a variable load large enough to check a normal auto battery, let alone a deep cycle large one.


 You may find a good auto shop or parts store that has a good battery load tester to do this test for you. Some parts houses will do the test for free. (of course they're trying to sell you a battery so watch the test and make sure they do not overload it!)

« Last Edit: December 31, 2008, 01:39:39 AM by zeusmorg »

WineGuy

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Re: Load Testing big deep cycle batteries
« Reply #8 on: December 31, 2008, 03:39:07 PM »
Here is what I have done in the past to try to "re-claim" batteries.


  1. Clean the terminals and all connections. You may need to strip some of the wire back from the connectors 'cuz the corrosion can actually travel up the wire under the insulation.
  2. Trickle charge (1 - 2 amps) the batteries for a LONG time. Check the SG to see if it  is fully charged.
  3. I hook up an inverter to the battery. I add a lamp with a 100 watt bulb and an analog clock. I start the clock at midnight. Come back every couple of hours to see if the bulb is still lit. The inverter will shut off when the batter gets down to around 11 volts, and the clock will stop.


Repeat steps 2 and 3 above and see if the battery stays running longer.


I also have a de-sulfator running and perform some shock load tests while charging, but that is a different topic.


Hope this helps.

« Last Edit: December 31, 2008, 03:39:07 PM by WineGuy »

bob g

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Re: Load Testing big deep cycle batteries
« Reply #9 on: December 31, 2008, 08:13:50 PM »
find out from the manufacture what the 20 hour rating is, and apply that amount of load, if the battery is good and fully charged it should carry this amount of load for most of the 20 hours.


true deep cycle batteries should not be tested with a load tester made for starting or marine deep cycle batteries (which are more of a compromise between a starting battery and a true deep cycle).


the thick heavy plates of a true deep cycle are not designed to deliver a large amount of amperage for a short test like that which a automotive load tester applies.


get them cleaned up, and charge them until they max out the specific gravity (no further rise after about 3 hours) and then let them rest for 24 hours.


recheck the specific gravity and see if all the cells match up pretty close, if not you may have to do an equalization charge and then rest them, and recheck the specific gravity.  if after all this the specific gravity is very close cell to cell

you can then do a 20 hour test to see what you have.


you will want to be armed with all the info you can get from the manufacture, what is the specific gravity of a fully charged battery? what is the 20 hour amp rating?

what is the end voltage spec supposed to be after a 20 hour test?


an automotive tester can be used to cull out the worst of the bunch after a good clean up, fill up and charge,, if the battery falls on its ass with a hundred amps applied, it might not be worth the effort to continue with.


or if you have the time and the inclination to do so, you can play around with whatever alternate methods you like to try and recover the poorly performing ones.

typically though you will find a few weak links that will only drag down the good ones in a string so it might not be worth the effort.


bob g

« Last Edit: December 31, 2008, 08:13:50 PM by bob g »
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winsolpower

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Re: Load Testing big deep cycle batteries
« Reply #10 on: January 01, 2009, 08:46:27 AM »
Brian: Looks good the log splitter. DO you have any close up of info on how to build, specially the hydraulic pack and ram?

Thanks

Hanks
« Last Edit: January 01, 2009, 08:46:27 AM by winsolpower »

DoctorCon

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Re: Load Testing big deep cycle batteries
« Reply #11 on: January 04, 2009, 05:28:40 AM »
Thankyou to you all for replying. I love the elegance of the inverter, clock and lamp solution and would love to give it a try once I reclaim/replace my hydrometer and bring my inverter back home. I wil also need to troll the net for the battery specs. I have a friend who might have access to a commercial battery tester (works for a telco with battery backups in their exchanges) and will explore this too.
« Last Edit: January 04, 2009, 05:28:40 AM by DoctorCon »

woodchips

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Re: Load Testing big deep cycle batteries
« Reply #12 on: January 04, 2009, 11:59:01 AM »
Hello, couple of suggestions.


First, most important, never run bateries directly in parallel, use isolating diodes from the charger to battery and battery to load. Reason is that batteries are all different, and will end up fighting each other and not putting current in the load.


Secondly, high current load testing, 50A or more. I have read about, but never used, a wet load bank. Basically it is a large non-conductive tub with a saline solution in it. The salt provides ions which makes the water conductive. Then two metal plates are put in, one at each end, the battery is connected and a current flows. The current can be regulated by either moving the plates closer together or putting more salt in. From what I can remember a plastic storage tray about 24" long and 15" wide could be a good start. Alternatively use aluminum cooking foil 300mm wide. Need to have metal clamps at each end to make a good connection over the whole width of the sheet. The length then determines the resistance, try 2m or so to start. Note that there will be considerable wriggling from the magnetic field so drape the foil over a couple of lengths of wood.


An obvious word of warning, high currents, melting aluminium, hot saline baths etc can be dangerous, take obvious precautions.


For any messing with batteries buy a DC clamp ammeter, they only cost £30GBP or so, well worth the investment.


Bob

« Last Edit: January 04, 2009, 11:59:01 AM by woodchips »

DoctorCon

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Re: Load Testing big deep cycle batteries
« Reply #13 on: January 05, 2009, 05:46:22 AM »
OK, OK, I admit it, the thought of my m-i-l in a nice warm electrified saline bathtub did pass ever-so-briefly through my head...

- but here is my more reasoned thunking.

The batteries have a 20hr manufacturers rating of 195amp hours. If I want to apply a load to discharge to 50% SOC over 10hrs then I will ?need a load that draws 195/20 = say 9.7amps. From my very vague recollection of electrickery I think this equates to a ~12 x 9.7 = say 120 watt lamp (a ?100 watt globe may do it - with my cheapo inverter losses - need to think more on this maybe).

If each battery (and lamp, and inverter) survives 10 hours of this with a end test voltage of  >12.2v / SG 1.190 (equates to 50% SOC from the battery FAQ). then I should be an EXTREMELY happy man and recharge my new friends promptly. Lesser life would decrease the size of my grin proportionally. Any battery that;

a. falls well short of the 10hr lamp test, or

b. survives significantly less than its mates

should be recharged/re-tested, but perhaps is likely to end up living a lonely life in my garage or going to the recyclers.


Can anyone see any flaws in my logic?

« Last Edit: January 05, 2009, 05:46:22 AM by DoctorCon »

Chuckrunyan

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Re: Load Testing big deep cycle batteries
« Reply #14 on: August 17, 2009, 10:31:15 PM »
Hi Bob


I know your posting is several months old.


But could you elaborate on using isolation diodes in the battery bank.  I think I know what you are getting at.  If I have three batteries in parallel different voltages (slightly), the higher voltage battery spends some of its voltage trying to raise the voltage of the others instead of powering the inverter.


So if I place an isolation diode between each of the plus poles of the batteries and the "paralleling" buss, I prevent one battery from trying to charge another.


But now switch to charging.  It seems like the isolation diodes would prevent me from simultaneously charging all three batteries if I were to apply the battery charging power to the "paralleling" buss???


Thanks for any help you can provide.


Chuck Runyan


chuckrunyan1@gmail    (dot com)

« Last Edit: August 17, 2009, 10:31:15 PM by Chuckrunyan »