Battery tender for not driving car for 1.5 months

Trip meters, maybe, though that might have changed with newer model like yours. I recall something like that. Maybe the later model years have some flash memory. Also, the display just reverts to defaults, for me the little pic of car with arrows going various directions. You "might" also lose ability for window to roll up with single touch, which can be "relearned". And..., at least on our 2010, the car does an unusual rev-up when starting, the next few starts, like it's recalibrating something.

You can dodge all this, with a memory saver. I have a jump pack with a cord, cig lighter plug at the pack, and obd connector at the other end, with just the 12 volt specific pins, and an indicator light to ensure you've got good connection.

But it's no big deal. I intentionally disconnect the 12 volt neg cable, if I'm going to look at the brakes, to play it safe.

 

I tested the battery with the tester I got today and it said "GOOD-RECHARGE."

 

It should say "RECHARGE AND RETEST after resting for 12 hours".

Right now it is marginal and pronouncing it "good" based only on that one test is NOT very accurate.
Which is true of most "consumer" battery testers......and many used by shops too.

Self-discharge is often an early symptom of battery failure and that can't be measured with only one test unless the test runs for several hours.

 

Who knows? If I leave the car overnight and retest will I get a different result? The battery is installed in the car and is subject to parasitic drains overnight. I retested this morning and got similar results. I don't think there is a self discharge problem. I understand that the Prius doesn't fully charge the battery anyway. Maybe I should disconnect a battery cable, fully charge the battery with my battery charger, and do an out of vehicle test. Probably won't change the results though.


If the Prime doesn't fully charge the battery, what meaning does a static voltage test of the battery have?

I'm probably going to replace the battery for piece of mind. I think it should have lasted much longer than the 11 days I didn't use the car plus it's at least 5 years old anyway.

 

If anyone needs a new 12v battery, good luck. Toyota wouldn't even order one for me. Carquest auto parts was the only place I could find one. I checked Napa, O'Reilly, Auto Zone, online searches...

 

Looking at these numbers:



I gather you inputted the 295A value, that's the CCA spec of the battery? I believe the 254A value is the as-measured CCA value. Also, 254/295=0.86 (aka 86%)..Maybe the tester's being optimistic. That CCA is significantly below spec. I think you'll find a recharge will bring the voltage up to so-so level, but the CCA would move much. In my experience once CCA drops below spec it's time.

Found the manual here btw:

user manual for konnwei kw850-Shenzhen Jiawei Hengxin Technology Co., Ltd (KONNWEI Technology )

But it doesn't go into much detail. At least with a quick skim, not much explanation of the verdict.

 

The CCA is for a new battery. I found this https://www.testingautos.com/car_care/images/battery-test-printout.jpg which shows this tester measuring the actual CCA of a battery and comparing it to the rated CCA. It's low and it's calling it good.

 

Yeah not sure. I know when I tested our in-the-pink batteries the CCA was always higher than spec. Could be more factors though.

 

This is from a brand new DieHard battery I just bought, tested out of the car not fully charged.

Actual CCA is lower than spec. Maybe I jumped the gun and my old battery still had a lot of life in it, or this tester is junk.

 

Your logic in dealing with your battery is kind of convoluted.

The tester is TELLING you that you should give it a full charge and that is the least that you should do.
There is no need to disconnect anything to do that.

But 5 years is a good life span for a battery.
Do whatever makes you happy.

Edit: I see that it's already been done.

 

I did charge the battery fully with my CTEK charger prior to testing. The tester must assume it wasn't charged because the battery voltage measured low. I've got the old battery out of the car and I'm charging it now and will test it when done.

 

End of story.
IF the battery IS fully charged but the tester says that it is NOT........
Then the battery is BAD.
(Having that important piece of information way back in your first post would have been REALLY helpful.)

 

I think I'm going to return this tester. I charged the battery out of the car yesterday and tested hot off the charger and got this. Note the high voltage (13.15v - overcharged?):

View attachment 219780



Then, this morning I tested and it said "GOOD BATTERY."

Now I'm consistently getting this:

Also, I have not seen this high a battery voltage on the battery in the car. Maybe I needed to remove the ground cable before charging like Toyota says?

 

There is nothing wrong with your tester.
The problem is with you not being able to properly interpret the results.

Did it come with a little instruction manual.....or is there one available online ?
Did you READ that ??

Typically you need to wait about an hour after a charging session before running a test.

The battery charger MUST put out a voltage higher than 13.2 volts in order to put any charge into to the battery.
The battery will RETAIN that higher voltage in the form of a "surface charge" for a time after the charger is disconnected.
Perfectly normal and does NOT indicate a problem.

If you had done the test twice or 3 times in a row, the end result would have been much better.

 

I've had no problems with the Solar line of testers, seems to be on the money. Solar BA9 is the current/available model. Ancel is also popular

 

I wonder if this type of tester, that uses a resistive load, would provide a more accurate test (Schumacher BT-100 Battery Load Tester and Voltmeter - 100 Amp)

 

Yep; that's what you should be using. Those "smart" battery analyzers are all over the map, mainly because they use such a small load resistor. It's trying to figure out a battery rated at 300+CCA with a <5A load resistor. Does that Konnwei have cooling vents cut into the case - to allow the load resistor within to cool down?

From what I've read about your situation, your original battery is fine. Remember; it only needs to close a few heavy-duty relays - not start the ICE. If your really worried about this; find a small & affordable jump-pack and toss it in the trunk. You'll need to check it every quarter for charge status - less so if you get one of those really nice lithium ones.

On your old battery, check your electrolyte levels and top-off with distilled water only!!! Don't over fill it. You should be doing this every fall; well late fall in your area; because of your warm early fall weather. I've consistently had regular car batteries last more than 10 years by doing this. I only buy those cheap batteries that you can get access to refill; not those very expensive sealed 84 month batteries. You don't get dramatic swings in temperatures like our northern folks; so you'll never need the full CCA capabilities of the battery.

You noticed the difference in charging the battery when you disconnected it form the car. That's because your weren't "splitting current" with the car's 'always-on' electronics and CPUs. The car doesn't magically know when your going to use it; it's constantly scanning and doing self diagnostics - almost forgot about the internet connectivity. All this takes power, which isn't coming off your drive pack battery in the trunk.

Hope this helps.....

 

Konnwei vs Solar on old battery. I'll be returning the Konnwei.

 

They’re not that far apart. What verdict did the BA9 give?

 

Hard to read, but it says OK. CCA readings were 24 A apart. I'd say that's a significant discrepancy.