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electricals:voltage_vs_health [2019/02/27 12:40]
jin created
electricals:voltage_vs_health [2019/05/15 23:33] (current)
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 ====== Why battery voltage is not a good indicator of battery health ====== ====== Why battery voltage is not a good indicator of battery health ======
 +
 +//Because batteries are far harder than you think//
  
 Being the sort of geek I am, with access to an actual programmable load tester and TSD's python scripts, I'd actually load-tested the Trojan battery before I fitted it in May 2016 (it was already old then, maybe 10 years by the date label!), comparing the result when I finally removed it shows how performance degrades massively but the battery voltage at idle (no load) is almost identical. Being the sort of geek I am, with access to an actual programmable load tester and TSD's python scripts, I'd actually load-tested the Trojan battery before I fitted it in May 2016 (it was already old then, maybe 10 years by the date label!), comparing the result when I finally removed it shows how performance degrades massively but the battery voltage at idle (no load) is almost identical.
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 {{ http://​fuddymuckers.co.uk/​gallery/​s/​1000/​alfie_electrics/​batt_graph_trojan31agm_good_vs_bad.png }} {{ http://​fuddymuckers.co.uk/​gallery/​s/​1000/​alfie_electrics/​batt_graph_trojan31agm_good_vs_bad.png }}
  
-The dead battery is managing about 3 hours at C/20 rate (5A for a 100Ah battery) compared to 18 hours it managed when fresh (but by no means new). And not managing the high-current spike at all.* +The dead battery is managing about 3 hours at C/20 rate (5A for a 100Ah battery) compared to 18 hours it managed when fresh (but by no means new). And it'​s ​not managing the high-current spike at all - that's the first very low blue spike, at which point the test script gives up on that idea and just runs the C/20 tests
- + 
 +Although the "​good"​ battery starts a little higher (maybe 12.6v to the "​bad"​ 12.4v), after a short period they'​re **both** floating up to around 12.4v at zero-load. Measuring the voltage, you would have //​absolutely no idea// that one battery had about 100Ah capacity and the other had perhaps 25Ah.
  
 ===== The Science Part ===== ===== The Science Part =====
electricals/voltage_vs_health.txt · Last modified: 2019/05/15 23:33 (external edit)
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