Deep cycle AGM battery almost died out on me

[cashcow]

Hi,

Been driving the Rav4 EV more often now and spending a good amount of time charging it back up.. Today I spend about 7 hours at a j1772 plug with the car on and the deep cycle botched almost died out. Couldn't turn on the car until I turned it off for a while then tried to turn it back on again. the dome lights were pretty dimmed out by then and the LEDs domes barely gave out any light. Just wondering about how much damage do you guys think the deep cycle agm took? I've been noticing a decline in its ability to power the car while charging lately. I had some of the heat on due to the cold air going on right now so I guess that drained it. Otherwise held out pretty good. I popped the hood and checked it and it wasn't fumming or anything. box didn't look bloated either,

Also, the big battery wasnt clicking at first to get it on ready on. I guess it didn't have any power to close the contractors until I let it rest for 10 minutes by turning the car off.

Can you manually turn on the contractors? I believe they are under the passenger seat? Do you need special gloves or can you use your bare hand. I think it is a round handle? If I turn it on like this will the car take any damage? Unsafe?

Do you need to remove the seat to do this or can you just reach under?

Dont recall just how old the agm is. I think maybe about 1.5 years?

 

[hokiematt]

The contactors are sealed inside the battery pack, and can not be manually activated. The only thing under the passenger seat is the high voltage service disconnect, which you should not disturb.

Most auto parts stores offer a free 12V battery check. They'll probably want to trickle charge your battery overnight before doing a load test on it. 1.5 years is pretty 'young' for an AGM battery to fail.

It may be that your symptoms are not the result of a bad battery, but rather a failing DC-DC converter (which uses the high voltage battery to keep the 12V system topped off when in charging or READY mode). With the system in READY mode, use a volt meter to check the voltage at the 12V battery; you should see 14-15 volts. If you see 13 volts or less, your converter most likely isn't working.

I've suggested folks get something like this: https://www.amazon.com/gp/product/B01N00I4TM/ It's accuracy may be off by a few tenths of a volt compared to a good meter, but it's a quick way to see if your DC-DC is working (14-15 volts). If you ever see less than 12 volts while driving, you need to consider getting off the road as some systems will start shutting down around 11 volts.

 

[cashcow]

The contactors are sealed inside the battery pack, and can not be manually activated. The only thing under the passenger seat is the high voltage service disconnect, which you should not disturb.

Most auto parts stores offer a free 12V battery check. They'll probably want to trickle charge your battery overnight before doing a load test on it. 1.5 years is pretty 'young' for an AGM battery to fail.

It may be that your symptoms are not the result of a bad battery, but rather a failing DC-DC converter (which uses the high voltage battery to keep the 12V system topped off when in charging or READY mode). With the system in READY mode, use a volt meter to check the voltage at the 12V battery; you should see 14-15 volts. If you see 13 volts or less, your converter most likely isn't working.

I've suggested folks get something like this: https://www.amazon.com/gp/product/B01N00I4TM/ It's accuracy may be off by a few tenths of a volt compared to a good meter, but it's a quick way to see if your DC-DC is working (14-15 volts). If you ever see less than 12 volts while driving, you need to consider getting off the road as some systems will start shutting down around 11 volts.

Hey there,

Thanks that sounds great. I have a 12V modified synwave inverter for charging small items (175w) but it does not have any LED screen displaying anything. Actually, I have looked into to these type of 12v readers before that you can plug into your cig socket, but they seem to be full of comments controversies stating that the reading is at the sig socket and not at the battery terminals which is what would be ideal. At least I hear that was the argument when I was reading into this a long while back. I think these devices are great because they show you the voltage real time while driving which is when you cannot get out of your car to tap on to the battery terminals... unless you have a device tapped in to the battery terminals and the wires ran through the firewall with the display on your dash for real time voltage of the terminals while driving. I think someone said that would be ideal before. Really i'm not tech inclined, but I think I recall this.

I did get a few months ago a volt meter from harbor freight for free (Cheap kind) but I have not gotten around to using it just yet. I should give it a try now. Still I am interested in having some sort of solution for knowing voltage real time while driving. Unsure if it would be best to know the voltage directly from the battery terminals or cig port....

Any thoughts on this? is the difference significant?

 

[dstjohn99]

With a good battery and dc-dc converter your voltage will be reasonably steady. So if you have a readout at the accy outlet you will know what normal looks like. Then if it starts dropping from normal you will know something is up. In that sense it doesn't matter whether you are at the terminals or not. Besides, knowing something is a huge step up from knowing nothing. So what if you are off by a few tenths of a volt. IMHO.

 

[smkettner]

You needed an old fashioned jump start to get you to the battery store.

 

[cashcow]

So I took out the voltmeter and set it to 20 dcv after driving the rav4 ev for a few hours. I charged for 2 hrs and I checked the voltage on the battery after finishing with out turning on the car. 13.36v. Then went inside and fully ready on turned the car. Checked the voltage and it was 14.41v. I guess last time i just left it on too long with the heat. 7hrs or so with heat on and not ready on isn very friendly to the agm I guess lol do these numbers look good?

checked 5 minutes later and its 14.46v with ready on

 

[miimura]

Don't use Accessory-On or On-but-not-Ready on the RAV4 EV. It will drain the 12V battery. You can leave the car parked for several hours at least with it READY and it won't use much range from the traction battery. However, do be aware that leaving the car in READY with an AGM battery for a truly extended period (like 12 hours or more) will cause it to overcharge and overheat. So, every few hours, turn it off and turn it back on to Accessory-On for a little while to drain some of the overcharge. I know because I did this once while camping. The Bosch battery overheated and started venting.

 

[cashcow]

What does a venting AGM smell like? Lead ones smell like rotten eggs. Does it vent sulfur or hydrogen? Also how did you know it was venting? Did it make noises? I've camped out of the RAV4 so many times I think I must have already damaged it but the case doesn't look bloated. Are there any other signs that tell if it over heated previously? Does driving the RAV4 for 12 hours also cause the AGM to over heat?

-edit-

Also ever since the rv4 ev failed to start due to the drained agm and dim dome lights it threw a check ev system take to dealership and has not cleared turned on and off the rav4ev 5 times and hasnt cleared off. been driving it since then though with really no issue. im also wondering judt how much damage the agm has taken. if it drains faster than normal is that a sign of really bad damage and needs replacement? maybe I run it in acc mode and check it every so often to see how fast it drains with the volt meter?

 

[miimura]

Yes, the venting smells like rotten eggs just like a normal battery.

Honestly, leaving the car parked and READY is the only way to accumulate 12 hours unless you're driving and JdeMO charging continuously back to back. Starting the car with a dead 12V battery will cause a Check EV System error that won't clear. You can clear it yourself with an inexpensive cable with Techstream on the front OBD port.

 

[cashcow]

Yes, the venting smells like rotten eggs just like a normal battery.

Honestly, leaving the car parked and READY is the only way to accumulate 12 hours unless you're driving and JdeMO charging continuously back to back. Starting the car with a dead 12V battery will cause a Check EV System error that won't clear. You can clear it yourself with an inexpensive cable with Techstream on the front OBD port.

Great I have not smelled that yet. With the lead acid it ended up fuming and I got poisoned for like a week a half because I thought it was milk I spilled in the back. It sucked and I hope I did not get long term damage from it.

Anyway, the agm is acting strange. I left the car in acc mode for I think 2 hours with fan on and the dome light started to dimmed. So I turned the car on to ready on for like 2 minutes to charge it then decided to turn it off and check the voltage to see where it was at.

12.94 v

So then I thought letś check the voltage while the car is in acc mode.

11.32 v

Then I was wow ok that is really low for a battery and the dome lights were dimmed previously so I thought the battery was dying. So I went and turned off the car and left it off. I checked the voltage on the battery again

12.74 V

So how come it dropped while on acc on? Is it because it was under 'load'? but that is pretty low isn't? It seems that on ready on the voltage is good but on acc at least after being on for a while it gets pretty low.

thoughts?

The car in full ready with big battery gives me 14.36 v

 

[smkettner]

Leave the hood up overnight. Check the battery voltage in the morning after a rest. Check voltage before you touch the car. Any load like opening the door will affect the results.

12.5+ is probably fine. s/b 12.7+

12.4 or less is probably time for a new battery. If an AGM battery has vented then it needs replaced.

 

[hokiematt]

Yes, the venting smells like rotten eggs just like a normal battery.

Honestly, leaving the car parked and READY is the only way to accumulate 12 hours unless you're driving and JdeMO charging continuously back to back. Starting the car with a dead 12V battery will cause a Check EV System error that won't clear. You can clear it yourself with an inexpensive cable with Techstream on the front OBD port.

Great I have not smelled that yet. With the lead acid it ended up fuming and I got poisoned for like a week a half because I thought it was milk I spilled in the back. It sucked and I hope I did not get long term damage from it.

Anyway, the agm is acting strange. I left the car in acc mode for I think 2 hours with fan on and the dome light started to dimmed. So I turned the car on to ready on for like 2 minutes to charge it then decided to turn it off and check the voltage to see where it was at.

12.94 v

So then I thought letś check the voltage while the car is in acc mode.

11.32 v

Then I was wow ok that is really low for a battery and the dome lights were dimmed previously so I thought the battery was dying. So I went and turned off the car and left it off. I checked the voltage on the battery again

12.74 V

So how come it dropped while on acc on? Is it because it was under 'load'? but that is pretty low isn't? It seems that on ready on the voltage is good but on acc at least after being on for a while it gets pretty low.

thoughts?

The car in full ready with big battery gives me 14.36 v

You have a bad cell. Fully charged, an AGM will show around 12.8 V (can vary a few tenths based on temperature and chemistry); under a constant load the voltage will decrease almost linearly until it hits 0% state of charge around 11.8 V. The fact that you're seeing a very quick drop to less than 11.8 V indicates that you've got one (if not more) damaged cells that barely have any capacity. A 12V lead acid battery is comprised of six cells in series, so the weakest cell in the link will determine the overall capacity of the battery.

You need to replace your battery ASAP before it leaves you stranded. Hopefully your battery is covered under a manufacturer's warranty.

 

[cashcow]

Hey

Yeah I think the battery took some damage because the dome lights some times dim when turning on the rav. Also I think they dim faster when the rav is not ready on for a few hours and I left it on because I was changing and inside. I'm going to keep an eye on it and see how it holds. As long as it doesn't fume then I'm ok with it. Though I had a nightmare last night it fummed! No joke and it was stressing.

 

[hokiematt]

I think you may be on borrowed time with your 12V battery. If you're not going to replace it, make sure you've got a set of jumper cables or a small lithium booster pack to keep with you in the RAV.

 

[TonyWilliams]

I concur with others... your 12 volt battery is bad.

It sounds like you had it under load without the car in READY, which of course, will drain it.

Please get a new battery BEFORE you start getting weird error messages and need to take it to a dealer to clear the errors.

 

[cashcow]

What kind of weird error messages can come up? I already got the check ev system. Is there room for more? Also how can I clear it? Someone said tech stream and a cable. Is tech stream a subscription? I really hope not because my mom took out a loan on a leaf and we are in debt so spending right now would not be good.

 

[davewill]

A bad 12v battery is a VERY bad thing in the RAV4EV. It can trigger expensive repairs if allowed to. Anyone who has any reason to suspect their 12v battery, should replace it ASAP.

 

[cashcow]

Hi

Can you elaborate on what kind of expensive repairs can happen because of a bad 12v battery? Also the way you said it makes it sound like these repairs will not be covered by the warranty

Thanks

 

[miimura]

If you have to take it to the dealer to diagnose the Check EV System and they determine that the 12V battery is the cause, you will have to pay for the diagnostic time. It will not be covered by the Platinum Extended Warranty since the battery is specifically excluded from that policy.

 

[davewill]

If you have to take it to the dealer to diagnose the Check EV System and they determine that the 12V battery is the cause, you will have to pay for the diagnostic time. It will not be covered by the Platinum Extended Warranty since the battery is specifically excluded from that policy.

This is essentially the issue. The car goes berserk sometimes when the 12v battery is low. If you are out of warranty, or don't realize the cause, the situation gets messy and expensive (diagnostics, towing, replacing parts that aren't actually bad) for what in a normal car would just be a new battery. Therefore it's best to replace the 12v battery at the earliest sign that it's not OK rather than try to coax it along.