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Discussion Starter · #1 ·
Sorry if this is a FAQ; I searched the site but found nothing exactly on point. I bought a new Konnwei battery tester and ran the test on my 2018 Premier's battery (purchased 8/18) after disconnecting both positive and negative cables. Selected AGM flat plate 520A. Here's the readout. Does this indicate I'll soon need a new battery? Hard to interpret "Charge and Retest" when I basically leave the car plugged in at all times, so the internal system should keep the 12V battery fully charged. Thanks for any advice.
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Hard to interpret "Charge and Retest" when I basically leave the car plugged in at all times, so the internal system should keep the 12V battery fully charged. Thanks for any advice.
I'd say your battery was getting weak and would replace it. Fully charged AGM batteries should be closer to 13 volts when disconnected.
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For a more accurate test of your battery's health you should put it on a charger for a while to ensure that is fully charged. (The official party line is that you should use a charger that is designed for AGM batteries which the Bolt has.) Once the battery has been fully charged, you then need to remove the surface charge before testing it.

A battery that has been on a charger is very full. When setting the table as a kid did you every fill everyone's glasses so that the water was just higher than the rim so that they had to bend down and slurp the water before picking it up? Otherwise they risked spilling some? This is how I like to picture a battery that has just come off been a charger and is fully charged.

In order to slurp off that surface charge, you need to either let the battery sit for a few hours or you can run your headlights for a bit. I have a battery load tester that I connect to remove surface charge.

Once the surface charge it gone, you can run your tester on the battery. Then you can have accurate results.

Finally, there are battery chargers out there that do something called desulfating. It is supposed to break up the sulfate crystals on battery plates and improve the health of your battery. It all sounds like black magic to me, but I have been using one on my vehicles once a year and the batteries seem to last at least 7 years. I just replaced an 11 year old battery in one vehicle.

Batteries aren't cheap so even if it is snake oil, it's easy to do once a year. My truck has two big expensive batteries so it gets desulfated for a week and tested twice a year. Those are pushing 8 years and are doing great.
 

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Discussion Starter · #5 ·
For a more accurate test of your battery's health you should put it on a charger for a while to ensure that is fully charged. (The official party line is that you should use a charger that is designed for AGM batteries which the Bolt has.) Once the battery has been fully charged, you then need to remove the surface charge before testing it.

A battery that has been on a charger is very full. When setting the table as a kid did you every fill everyone's glasses so that the water was just higher than the rim so that they had to bend down and slurp the water before picking it up? Otherwise they risked spilling some? This is how I like to picture a battery that has just come off been a charger and is fully charged.

In order to slurp off that surface charge, you need to either let the battery sit for a few hours or you can run your headlights for a bit. I have a battery load tester that I connect to remove surface charge.

Once the surface charge it gone, you can run your tester on the battery. Then you can have accurate results.

Finally, there are battery chargers out there that do something called desulfating. It is supposed to break up the sulfate crystals on battery plates and improve the health of your battery. It all sounds like black magic to me, but I have been using one on my vehicles once a year and the batteries seem to last at least 7 years. I just replaced an 11 year old battery in one vehicle.

Batteries aren't cheap so even if it is snake oil, it's easy to do once a year. My truck has two big expensive batteries so it gets desulfated for a week and tested twice a year. Those are pushing 8 years and are doing great.
I have ordered a Schumacher charger with desulfating capability from Amazon, and it should arrive in a couple of days. Perhaps I should run a desulfating cycle, charge the battery with it, and then run a load test with the Konnwei. Do I need to disconnect the battery terminals when I charge it?
 

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My battery charger (Batteryminder) charges and desulfates at the same time. Once it is done charging, it goes into float (maintenance) mode and it continues to desulfate. I typically let it run at least a week in float/desulfate. Another thing I do is install quick connects on all my vehicles. Much easier than fiddling with battery clips.

I leave my battery connected when I charge/condition them since I have the quick connects. My tester has a setting to indicate if the battery is in (connected) the vehicle. Chances are your's does too. This is the test I run most of the time because resetting clocks and entering lockout codes is a hassle. I find this is good enough for tracking the general health of my battery. When I want to really establish a baseline on a battery, I will disconnect it from the vehicle. In your case I would disconnect since you are looking for a baseline. Remember to remove the surface charge before you disconnect. Twenty-30 seconds of the headlights should do the trick.

Another thing to consider is that desulfation (still not 100% bought into it, but since I have a charger that does it and have the time, I'm happy to drink the Kool-aid) takes time. The longer it is allowed to run the more the health of the battery can be improved. I was able to take my buddy's marginal battery and after a couple weeks of being connected to my charger/desulfator, it turned into a serviceable battery and is still in his vehicle a couple of years later.

It still all seems like a bunch of witchdoctorey. Kind of like going to an orthopedist vs a chiropractor. I guess if getting your neck cracked makes it feel better it must be doing something. Right?

Good luck.
 

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I really prefer load testers with good ol' analogue voltage meters because I can see exactly what the battery is doing under load, whether the voltage continues to sag while the load is applied, what it rebounds to after the test, etc. etc. These newfangled computerized rigs do a lot of opaque processing under the covers that hides information, IMHO.

And they're less pricey!



I load test my battery every 3 months (at the same time I check and recharge me Li-Ion booster pack) to establish a baseline against which I can check any deviation. I just installed a dashcam a few months back and it has a parking mode that runs off the 12V battery with a low voltage cutoff, so I'm kind of back to square one in seeing what a baseline looks like...
 

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I bought a new Konnwei battery tester
Eh........I wouldn't put all that much faith in the accuracy of the instrumentation or the methodology of the test it does. I've worked with battery gauges of similar constitution and they were off by as much as 20% when we measured it against a proper instrument. What results do you get on other batteries?
 

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good ol' analogue voltage meters
This is the same unit I have as part of my battery health monitoring kit. It's also great for removing the surface charge on a battery that is not in a vehicle. The digital testers are helpful in that they provide additional data points to track battery health. Every time I test a battery I record the results from both testers and review the history to identify the trends.

Once a battery's numbers have dropped enough I am already ready to replace it.
 

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I put meter on battery and test voltage. Then I turn on all lights and watch voltage drop.
Both the new and old testers are probably good in how they report assuming the battery is charged. I don't really see a need to disulfate an AGM. If you want the battery to work, just get a new one. You will just go mad trying to scuffle along with a weak battery.
 

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Discussion Starter · #11 ·
My battery charger (Batteryminder) charges and desulfates at the same time. Once it is done charging, it goes into float (maintenance) mode and it continues to desulfate. I typically let it run at least a week in float/desulfate. Another thing I do is install quick connects on all my vehicles. Much easier than fiddling with battery clips.

I leave my battery connected when I charge/condition them since I have the quick connects. My tester has a setting to indicate if the battery is in (connected) the vehicle. Chances are your's does too. This is the test I run most of the time because resetting clocks and entering lockout codes is a hassle. I find this is good enough for tracking the general health of my battery. When I want to really establish a baseline on a battery, I will disconnect it from the vehicle. In your case I would disconnect since you are looking for a baseline. Remember to remove the surface charge before you disconnect. Twenty-30 seconds of the headlights should do the trick.

Another thing to consider is that desulfation (still not 100% bought into it, but since I have a charger that does it and have the time, I'm happy to drink the Kool-aid) takes time. The longer it is allowed to run the more the health of the battery can be improved. I was able to take my buddy's marginal battery and after a couple weeks of being connected to my charger/desulfator, it turned into a serviceable battery and is still in his vehicle a couple of years later.

It still all seems like a bunch of witchdoctorey. Kind of like going to an orthopedist vs a chiropractor. I guess if getting your neck cracked makes it feel better it must be doing something. Right?

Good luck.
Schumacher charger arrived. I disconnected battery from car and charged it to 100%. Reconnected battery and put on the Konnwei load tester. Ran the lights as instructed by tester to eliminate surface charge. Then ran the test. This time it said "battery good, recharge," and showed SOC of battery as only 60%! Not sure what's going on.
 

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Schumacher charger arrived. I disconnected battery from car and charged it to 100%. Reconnected battery and put on the Konnwei load tester. Ran the lights as instructed by tester to eliminate surface charge. Then ran the test. This time it said "battery good, recharge," and showed SOC of battery as only 60%! Not sure what's going on.
Batteries are often delivered with less than a full charge.
 
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