Battery Test

Discussion in 'Tech/Mech General' started by Peter A Forbes, Jul 17, 2016.

  1. Peter A Forbes

    Peter A Forbes Funster

    Joined:
    Nov 23, 2014
    Messages:
    259
    Likes Received:
    182
    Location:
    Rushden, Northants, UK
    Just out of interest, I'm running a discharge test on a 6V 225AH AGM battery for a customer. The test is a resistive load to give 21A load at the start of the test, reducing slightly as the battery volts drop down.

    Off load the battery was 6.59V after a full recharge.

    Test started at 10:26am with 6.26V terminal voltage at 21.20A load.

    As I type it was 6.05V at 20.05A at 15:31pm.

    The shunt is a 60mV to 30A type, the actual amps is a formulae conversion.

    Volts Shunt mV Actual Amps Time
    6.59 0.00 Off Load 10:25:00
    6.36 42.40 21.20 10:26:00
    6.32 41.80 20.90 11:03:00
    6.28 41.70 20.85 11:30:00
    6.24 41.00 20.50 11:57:00
    6.22 40.70 20.35 12:34:00
    6.20 41.10 20.55 12:55:00
    6.15 40.70 20.35 13:52:00
    6.12 40.50 20.25 14:30:00
    6.09 40.40 20.20 15:00:00
    6.05 40.10 20.05 15:31:00

    So 5 hours and just over 100AH taken out. It should produce 194AH at that discharge rate.

    The test takes the block down to 5.70V (6V block)

    I'll post the final figures later, this is a used but nearly new battery.

    Peter
     
    Last edited: Jul 17, 2016
    • Informative Informative x 1
  2. SomeoneElse

    SomeoneElse Funster

    Joined:
    Apr 22, 2013
    Messages:
    571
    Likes Received:
    375
    Location:
    Cotswolds
    A 225 AH battery? I assume that's at the 20 Hour test. You are discharging it at close to a 10 hour test so I would expect its capacity to be less than 200 AH at that rate. A full AH test would take a 6V battery down to 3.6 volts ( 1.2 V per cell ). Your 100AH at 6.05V seems about right.
     
  3. Peter A Forbes

    Peter A Forbes Funster

    Joined:
    Nov 23, 2014
    Messages:
    259
    Likes Received:
    182
    Location:
    Rushden, Northants, UK
    1.2V per cell for any lead-acid battery would kill it. Don't know where you got that from.

    I did point out that 194AH was the expected returned capacity.

    Peter
     
  4. Peter A Forbes

    Peter A Forbes Funster

    Joined:
    Nov 23, 2014
    Messages:
    259
    Likes Received:
    182
    Location:
    Rushden, Northants, UK
    Test stopped at 5.43V terminal voltage, average current for the test was 19.78 amps.

    Test ran from 10.30am to 21.30pm, total capacity removed was 219.37 ampere-hours, against the manufacturer's figure of 194 ampere-hours for the 10 hour test. We were slightly below their figure of 20.00Amps.

    We didn't take it right down to 1.70V per cell as we had proven the capacity of the battery, so it was immediately put onto a recharge at 15A with a setting of 7.20V on the power supply. That will get a recharge back in overnight without getting anything warm.

    Interesting that there is a fair bit of extra capacity over the published figures, but I have heard of 240AH being quoted for these batteries.

    225AHTest.jpg

    Hope I haven't dropped any clangers in the spreadsheet!

    We did have an analogue ammeter across the shunt as a rough check on the discharge current, but shunt readings were used for the spreadsheet.

    Peter
     
    Last edited: Jul 17, 2016
    • Informative Informative x 1
  5. Peter A Forbes

    Peter A Forbes Funster

    Joined:
    Nov 23, 2014
    Messages:
    259
    Likes Received:
    182
    Location:
    Rushden, Northants, UK
    We are testing a brand new block today, after giving it a top-up recharge overnight.

    Figures later.

    Peter
     
  6. Peter A Forbes

    Peter A Forbes Funster

    Joined:
    Nov 23, 2014
    Messages:
    259
    Likes Received:
    182
    Location:
    Rushden, Northants, UK
    Results of the new block show very similar performance and capacity. As the new one has been stored for some time with just refresh charging, its capacity is marginally lower, but its test finished on a time basis with a slightly higher terminal voltage, so too close to call.

    The first battery was in service for 18 months on a train battery raft as one of 17 blocks in series.

    These are Chinese, manufactured by Full River.

    Peter
     
Loading...

Share This Page