Battery Warning Light Stays on Despite New Battery

Greetings all, this is my first post,

I've got a 2012 EV with ~70K miles on it and other than having the fuses replaced in the onboard charger ($1.2K), it's been a relatively trouble-free vehicle.

My 12v battery failed on me a couple of days ago. I was surprised because it's less than a year old and it's a good one (Optima). I bought a new battery anyway and installed it on the side of the road where the EV had failed. Everything fired up okay, except all the stuff that has to be reset of course, but the battery warning light stayed on.

I've read the posts about folks who've had problems with power leaks and I suspect something similar might be happening to me. But... I didn't see anyone mention that their battery warning light stayed on after installing a new battery, which leads me to believe I may have a different problem. Is there a way to reset the warning light? (doubtful, but I gotta ask) Or is there a fuse for the DC/DC converter that might be blown?

Anyway, you guys and gals sound like a smart helpful group and I sure could use a little advice right now.

Thank you,
Rick Kelly
Solvang, CA

syvalley said:

Greetings all, this is my first post,

I've got a 2012 EV with ~70K miles on it and other than having the fuses replaced in the onboard charger ($1.2K), it's been a relatively trouble-free vehicle.

My 12v battery failed on me a couple of days ago. I was surprised because it's less than a year old and it's a good one (Optima). I bought a new battery anyway and installed it on the side of the road where the EV had failed. Everything fired up okay, except all the stuff that has to be reset of course, but the battery warning light stayed on.

Click to expand...

There is not a warning light in a rav4ev that like in a normal car says the 12 volt battery isn't charging.
What do you mean with " battery warning light" ? do you mean "check ev" ?
Did you check the "old" battery ?
what was the voltage when you disconnected it from the rav4ev ?
Did you charge it up and put a load tester on it ?
For some reason I don't think the battery is bad.
Not a optima after 1 year.

I've read the posts about folks who've had problems with power leaks and I suspect something similar might be happening to me. But... I didn't see anyone mention that their battery warning light stayed on after installing a new battery, which leads me to believe I may have a different problem. Is there a way to reset the warning light? (doubtful, but I gotta ask) Or is there a fuse for the DC/DC converter that might be blown?

Click to expand...

If you used the cabin heater this week for the first time again, the fuses in it might have blown and it usually takes the DC/DC converter with it.

To check:
Open the hood with rav off, check voltage of the 12 Volt battery: eg 12.9 volt
When you press brake , power it on "ready " on display, check voltage again and it should be 13.4+ volt.
If that is the case, your dc-dc converter still works.

I think you have a different issue than the 12 volt battery

Anyway, you guys and gals sound like a smart helpful group and I sure could use a little advice right now.

Thank you,
Rick Kelly
Solvang, CA

Click to expand...

Thank you for your reply fromport!

What do you mean with " battery warning light" ?

Click to expand...

There is small red battery icon below the Driving Range graph on the right side of the dash display. It has two battery posts and a +(plus) and a -(minus) sign and can be seen, along with all the other warning indicators, when you first fire up the EV. They all go off after a couple of seconds, but in my case, the battery warning stays on.

Did you check the "old" battery ?

Click to expand...

The Optima was completely dead, not even enough power to turn on an interior light. I was lucky enough to break down about a mile from a parts store where I purchased a new (less expensive) battery and a 10mm wrench. I was able to return to the car, swap out the batteries and drive home. I agree 100% with you, I don't think the Optima is bad, I think it was drained because it was not being recharged by the DC/DC converter. I trickle charged it last night and it's back to ~13.5 Volts. I only purchased a new battery because it was cheaper and faster than a tow.

If you used the cabin heater this week for the first time again, the fuses in it might have blown and it usually takes the DC/DC converter with it.

Click to expand...

Really good to know. I will find and check the cabin heater fuses as soon as I post this reply!

To check:Open the hood with rav off, check voltage of the 12 Volt battery: eg 12.9 volt
When you press brake , power it on "ready " on display, check voltage again and it should be 13.4+ volt.

Click to expand...

I checked and the battery was at ~13.5 volts with the EV off and ~13.5 volts in the Ready state. I'm using an older analog multi-meter, so it might be off by a couple tenths.


Thank you again for taking the time to share your expertise. I really appreciate it!!

There is definitely something wrong with your DC-DC converter. That is what the Battery Warning light is telling you. Also, as soon as the car is in READY, the voltage at the battery should go up above 14VDC.

Thanks miimura! That's what I was thinking too, but I don't know what to do next on the troubleshooting ladder. At fromport's suggestion, I just ran a continuity test on every fuse in all four fuseboxes, but no luck. I'm having trouble understanding why the DC-DC converter wouldn't have a dedicated fuse somewhere.

syvalley said:

Thanks miimura! That's what I was thinking too, but I don't know what to do next on the troubleshooting ladder. At fromport's suggestion, I just ran a continuity test on every fuse in all four fuseboxes, but no luck. I'm having trouble understanding why the DC-DC converter wouldn't have a dedicated fuse somewhere.

Click to expand...

Sorry , i was not aware of a separate light for the "12 volt battery not charging"
When my dc-dc converter stopped working, that light never came on :-(

It has a dedicated fuse INSIDE the unit.
That is why tesla/toyota just exchanges the whole unit instead of replacing the fuses.
And it is completely sealed, you have to pry it open.
Look at the forum for a thread where someone did exactly that !

The interesting thread about the DC-DC Converter is here:
Anatomy of The DC/DC Converter

Update:

Thanks for the replies fromport and miimura! I've read everything that was suggested on the DC/DC converter, including the breakdown posts from ddoxey and TonyWilliams. I also got my hands on a digital multimeter to confirm what my old analog meter was telling me, which it did. The battery voltage is down ~.2V instead of being up when the car is turned on and in the Ready state.

I also fired up my cabin heater and confirmed that it seems to be working fine. I've got hot air blowing out the vents and the Denso heater core under the hood seems to be warmer to the touch after a few minutes. Kinda hard to tell because it's 95 degrees here in SoCal. :twisted:

So, my question is, does the fact that my cabin heater still seems to be working along with the battery warning light remaining on, mean that I might have a different problem than what others on this board have experienced?

One of the big 50A 200V fuses in my onboard charger blew a couple of months ago. Toyota wanted north of $4K to replace the whole charger, but I found a local shop (Santa Barbara) with a tech that was Tesla trained. I bought the 2 fuses for a $100 and he put them in for $1.2K. The reason I bring this up is that if I was able to narrow down the likely cause of the DC/DC Converter failure (e.g. fuse), I could ask the same Tesla mechanic to fix it rather than forking out $1.8K for a whole new converter, plus labor to install it. I think he's got faith in me since I was lucky enough to make the right call re: the onboard charger fuse.

Thanks again all!

Just to add some more weirdness to this, i just noticed that plugging the 40A traction battery-charger in seems to draw heavily from the 12v battery. I had the 12v on a trickle charge overnight and now, in the morning, it indicated it was charging at about 1 amp meaning I have a full 12v battery. But when I hooked the big 40A charger for the system battery, the little trickle charger jumped all the way to the top, about 10amps, which would indicate something is drawing heavily from the 12v battery during the charging of the traction battery. I guess it wouldn't matter if my DC/DC converter was working??

Does any of this make sense to anyone? Does the 12v battery supply power for something during the traction battery charge cycle?

Thanks

syvalley said:

I guess it wouldn't matter if my DC/DC converter was working??

Click to expand...

correct, the dc-dc converter should take care of that normally

Does any of this make sense to anyone? Does the 12v battery supply power for something during the traction battery charge cycle?
Thanks

Click to expand...

eg: the big "click" you hear when you get the car in "ready" mode is the high voltage connector that enables the high voltage to be connected to the rest of the EV.
Those relays alone draw some serious power (since 500+ amps when accelerating in sport mode)


It really is up to you what to do.
Buy a second hand unit from ebay, replace the broken one with that, or open up your current one and fix it.
I would do that and see if you could fix it. You can always buy a unit from ebay if it doesn't work.
Downtime is your only downside of that.

Thanks again for your time fromport!

I would love to open the unit and have a look, but I'm a little intimidated by the two high voltage cables and also the coolant system. On paper it looks easy; remove 4 bolts, 8 cables and 2 coolant lines and I'd have the converter on my garage workbench just like that. But....I'm not sure what sort of procedure I need to follow for unhooking and reattaching the coolant lines and I'm also not sure how to remove the two HV cables, and lastly, do I need to worry about any static electricity remaining in any of the components once I get the top off? So anyway, I'd really like to give it a go, but I still need a clearer plan. Have you ever taken one out before?

The other question mark for me is that I still don't understand what problem could be causing the converter to no longer charge, but still allow the cabin heater to work. Could the cause be one of the Bussmann 40A fuses is blown?

If you bring it to our shop in San Diego, we can diagnose and repair it:

Quick Charge Power LLC
1780-104 La Costa Meadows Drive
San Marcos, CA 92078

Office: 760-798-0342
Hours: M-F, 9-5

I'm tempted to take you up on that, Tony. Do you mean bring the EV to the shop or bring the converter? I'm about 230 miles away.

syvalley said:

I'm tempted to take you up on that, Tony. Do you mean bring the EV to the shop or bring the converter? I'm about 230 miles away.

Click to expand...

Drive or trailer.

It’s cheap to move cars around SoCal.

Hmm....sounds interesting. Let me check into options and cost. What kind of range of time might you need to make the repair (dependent on what you find of course) ? Ideal for me would probably be to rent a trailer and make an early morning run to San Marcos to get the EV there when you open. I'd feel a lot better about owning this vehicle if I knew I had someone to bring it to.

Okay, just got some information. Would you prefer that I call you or should we keep it in the thread?

-Rick

Just call our shop with delivery info.