Toyota Rav4 EV Forum
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Deep cycle AGM battery almost died out on me
http://www.myrav4ev.com/forum/viewtopic.php?f=7&t=2334
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Author:  smkettner [ Sun Mar 10, 2019 11:23 pm ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

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.

Author:  hokiematt [ Mon Mar 11, 2019 9:27 pm ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

cashcow wrote:
miimura wrote:
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 letÅ› 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.

Author:  cashcow [ Sat Mar 16, 2019 10:55 pm ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

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.

Author:  hokiematt [ Sun Mar 17, 2019 8:35 pm ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

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.

Author:  TonyWilliams [ Sun Mar 17, 2019 11:04 pm ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

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.

Author:  cashcow [ Mon Mar 18, 2019 4:35 am ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

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.

Author:  davewill [ Mon Mar 18, 2019 5:18 pm ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

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.

Author:  cashcow [ Tue Mar 19, 2019 8:51 am ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

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

Author:  miimura [ Tue Mar 19, 2019 5:46 pm ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

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.

Author:  davewill [ Tue Mar 19, 2019 6:46 pm ]
Post subject:  Re: Deep cycle AGM battery almost died out on me

miimura wrote:
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.

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