When to replace the battery

Joined
Aug 17, 2016
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Location
Alberta
Our '07 Accord k24...
I bought a group 24f rated at 725 CCA to replace the 7 year old AGM 51r, which is rated at 440 CCA. The 51r is now testing at 420 to 440 CA at around +10 deg C, which is much warmer than -18 deg C (0 deg F) that CCA is rated at. So I think it's time to replace, even if it's cranking o.k. for now. The group 24f will fit, and it's a common upgrade on Accords, so why not? The 24f weighs 14 lbs more, and cost $16 more than the 51r (I was looking at non AGM this time).

I'll install the 24f tomorrow, and post some pics. The cheapskate in me wanted to run the 51r a bit longer, but thankfully, common sense regarding upcoming -30 deg C cold snaps has prevailed.
 
This summer at the behest of my son I checked out battery on my wife's Camry. Original battery, 24 F 580CCa. The battery started OK, but resting voltage was 12.2 V. I brought it up to 12.8 with my HF 1/2 amp trickle. I replaced it instead of waiting for it to die as usual.
 
That's a popular upgrade with the k24. I upgraded my 51r to a AGM group 35. The 51r was an everstart Maxx from Walmart, didn't last 4 years. I always had to put my ctek charger on it every weekend during the final months. If it sat for 2 days in our -30c winter it wouldn't start. (Also heater block was plugged in). Brought it to an auto shop and load tested, it was a goner. Group 35 is going strong for 3 years.
 
IMHO, first you want good voltage at cranking, if lower than 9V - time to replace; well, given charging system is in order.
Also, check charge level after coming home after a good drive and compare it with charge level next morning. If charge level dropped from say 95% to 65% - time to replace.
Basically - battery needs to hold voltage, have capacity to crank multiple times and not just once and not to discharge on its own quickly.
I got this little battery tester MOTOPOWER MP0515A when it was on sale and it actually works well giving useful info on batt state.
If you need only one batt tested then it'd make sense to get it done some place.
 
IMHO, first you want good voltage at cranking, if lower than 9V - time to replace; well, given charging system is in order.
? A 12v car battery at 9v isn't going to crank anything. Even 12.0 volts is iffy and only 50% of max volts.

edit: oh, during cranking. Not right before cranking.
 
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