Carnerd

How accurate is the voltage read-out on the 981's? If it's accurate, can you use it to assess when the battery should be changed? Before I turn the engine over I'm getting around 11.2-11.5V.

Code

No accuracy issues here, but if you question it test it with a multi-meter. You can also get a free battery test at most auto parts stores, which will tell you if a cell is going bad. I generally swap out batteries whey that are within 6 months of expiration, and my battery tender also tells me when the battery is going bad.

Carnerd

Code, thanks for the reply. What voltage reading is used to diagnose when a battery has gone bad?

Code

No problem. So, if the battery cannot reach higher than 10.5 volts when being charged, then the battery has a dead cell, which doesn't sound like the case here. Fully charged (according to a battery charger) but the voltage is 12.4 or less, the battery is very likely sulfated to some degree. Sulfation is the natural byproduct when a battery discharges. Re-charging the battery will reverse the sulfation crystals and turn it back into electrolyte, ready to produce power again. But if a battery sat uncharged, severely discharged, and/or drained for extended periods of time, the sulfation will increase in size and harden onto the plates. This covers the surface area of the plates, removing the chemicals needed to produce adequate power. Sulfation decreases the potential to reach a full charge, and it self-discharges the battery quicker than normal. Charging a sulfated battery is like trying to wash your hands while wearing gloves. At this point, charging alone will not restore the battery to a healthy condition. From what I understand the majority of replacement battery purchases occur when the original battery has reached this point. You mentioned that your battery is around 11.2-11.5 volts at start-up, so my question would be has the car been sitting for a while? and does the voltage reading on the dash increase after driving? or is it holding at that 11.2-11.5 range even after driving for 20+ minutes? If it is staying in the 11 volt range, it is most likely sulfated and you should consider replacing it. Like I mentioned before, most auto parts stores can load test the battery for you, which will give you a more definitive answer. I hope this helps.

Viper pilot

I'd say your battery is toast! My battery voltage is usually about 13.2 volts after sitting for a week or longer. I'm using a Li type battery btw. And it's new.

Antigravity

13.2v would be resting voltage on lithium but for your lead/acid it should be around 12.7,v, as suggested earlier, bringing it in to get a test would be good...even if the voltage is where it's supposed to be a load test can help identify if the battery is weakening. If it's sitting around 11.5 though that's a sign something could definitely be up...we also make our Battery Trackers which can accurately display your voltage and check how your battery performing during a starting attempt and then display it directly on your cellphone.

Lead Acid Battery Tracker
Lithium Battery Tracker

Carnerd

Thanks for this!

As soon as I turn the car over it moves to 14.5-14.8

Good to know. Thanks

Awesome. Thanks