2015 Toyota RAV4. Family members car. They went to a dealer for an oil change. And the dealer said the battery was dying. Dealer wanted $270-$300 for a new battery with installation. Family decided to wait and ask me.
I checked the battery myself and the battery voltage was low, 12.06V at rest and 9.27V at crank. If it were me, I’d just push it to the limit and just wait. But the family member isn’t so inclined.
So I recommended to get a new one and offered to do it for them. I suggested options for an AGM battery which was $180 vs $120 for traditional, giving the pros and cons, and they wanted AGM. And we were able to change it out smoothly.
When I went to return the old battery core, I did notice the liquid in the battery was low. In retrospect, I should have tried adding water first before calling for a new battery.
1) Would filling the battery with water revived the battery to hold a charge for a fair length of time? Or is it already too far gone? (I personally have never added water to a battery, just always changed it out.)
2) I have changed out a few batteries, but only after the fact when the car has a hard time starting or needs a jump.
There were no symptoms for the RAV4, I just recommended it as a precaution, based on the voltage. This is the first time I have changed out a battery as preventative maintenance. Was it too early? Too late? Or just in time?
they wanted AGM
Is their car compatible with AGM? Don't AGM batteries require a charging system designed for AGM with the correct voltages and charging profile?
I did notice the liquid in the battery was low
how do you know? They aren't supposed full to the top.
Would filling the battery with water revived the battery to hold a charge for a fair length of time?
maybe. unlikely. How old was the battery? Did the battery have a removable top, or was it "maintenance-free"?
Was it too early?
I change it when I start experiencing problems. But the voltage was pretty low. I can't understand how it wasn't struggling to start, but I have a V8 not a 4 cylinder.
I was wondering about the charging system. I presumed AGM was compatible, because it was offered as an option when putting in the make and model of the car, alongside the traditional batteries.
For the battery fill. The thing that gave me the clue was the opaque nature of the Panasonic battery. It also had a min and max fill line. And the water was below the fill line. It had several removable access points at the top. It was 9.5 years old.
I concur, I was surprised the car was starting easily! Alas, it could probably be cause it is a 4 cylinder.
Interesting. I've never seen a battery with min max marks. So in that case yeah the battery needs to be kept topped up with distilled water (and give them a little shake).
Just because an option is offered, it doesn't automatically mean you can use it. Even within a make+model there are variations and optional equipment. It's your responsibility to know what the car needs.
@imperator You are correct. Although not intensive, I also did some quick research to make sure it would be okay, alongside Costco’s suggestions. I decided it was worth trying it out, when it popped up as one of the only two options. From what I understand, on most* modern cars one can easily go from lead acid to AGM, but not the other way around.
@imperator Here is a pic of the battery:
https://imgur.com/a/ZJ9M4ao
My first time seeing a Panasonic.
looks like a Japanese spec battery.
Anyway like Hixster said, unless you live in extreme conditions the AGM isn't worth the extra cost.
@imperator all things being equal, I think the benefit of AGM would be negligible. However, one of the big reasons the owner of the car (not me) decided to go with AGM was because of the frequency of use for the car, which isn’t as much as it used to be. The owner isn’t mechanically inclined. While the lifespan might be the same, AGM is maintains its voltage for longer than lead acid. Discharge is slower for an AGM. And that sold them on the AGM. We went over the pros and cons of each. They were happy with the $180 AGM with free labor from me, as opposed to the $300 lead acid the dealer was going to charge them.
Checking/adding water, will allow for more months of service. (I've never tried to revive a lead-acid battery)Would filling the battery with water revived the battery to hold a charge for a fair length of time?
I use batteries longer than most folks. There's no way I'd attempt to do that in my lady's car, no way.This is the first time I have changed out a battery as preventative maintenance. Was it too early? Too late? Or just in time?
That's low, I'd would have changed it too. I would not have used an AGM battery. IMO it was too expensive and simply not necessary.I checked the battery myself and the battery voltage was low, 12.06V at rest and 9.27V at crank.
@hixster thanks for your thoughts!
Anything under 10V while cranking is a battery ready to fail and leave you stranded in my opinion. It's also probably wearing out the alternator due to excessive charging of a weak battery.
If I get 5 years out of a car battery I'm satisfied. I had a battery go 8 years and then suddenly die. Luckily I was at home when it happened. I waited too long to replace it because I didn't know how to test batteries at the time.
I read up on AGM batteries to learn about them. They're mostly used in stop/start cars that turn the engine on/off automatically. They can survive more charge cycles than regular batteries and also charge faster. Although I read they have a similar service life of around 5 years.
AGM batteries are damaged by voltages above 15V but can handle higher charge currents of 20 or 30 amps.
Flooded batteries are the opposite. They can handle higher voltages of 15V to 17V but a current over 10 amps will start damaging the battery. I read a 20 amp charge will start damaging a flooded battery after 20 minutes.
https://www.interstatebatteries.com/blog/how-to-charge-an-agm-battery
14.5V seems to be the sweet spot for a battery charger that can charge both AGM and flooded batteries. For flooded batteries lower the current to 10 amps and for AGM turn it to 20 or 30 amps if you like. When the battery charger's amp gauge shows the battery is only drawing 1 or 2 amps, the battery is fully charger so turn the charger off.
I leaned the difference between float charging and trickle charging as well. A float charger applies a constant 13 volts and 200mA, for example, to maintain a fully charged battery. The charger never shuts off.
Trickle chargers monitor the voltage of a battery and when it drops below a certain voltage, 12.6V for example, the charger automatically turns on and charges the battery back up 13V then shuts off again.
It's best to check the water level of a battery once a year during an oil change. Only fill until water barely covers the top of the metal lead plates inside the battery then stop. Never fill until water is coming up the plastic round fill tubes. There's actually a notch cut into the bottom of the plastic tube. That notch is there to allow hydrogen gas to vent out. If the notch is covered with water then the gases can't vent.
@oskool thanks for the info! I think I made the right choice by changing it out.
I got mixed up float charging and trickle charging in my above comment. https://electricalacademia.com/batteries/battery-charger-types-trickle-float-charger-working/
@oskool thanks!