12v Battery Flat? How to charge?

[RedOnesGoFaster]

Hi all,

I'm a happy new owner, bought my 2017 Yaris Hybrid shortly before the lockdown (great timing) and so have done little mileage since then.

I have been using it once or twice a week round town and the occasional out of town trip as we have been allowed.

Last week I got into the car and hit the start button. I got some error messages about safety system failures that seemed to be linked to the camera/radar system. After a few tries, the big screen didn't come on and a few other warning lights came on. I called the dealers and they told me to get the Toyota assist to look at it then get it taken to them if needed.

While waiting for the AA to come, they ask for the windows to be opened beforehand to 'air' the car for Covid reasons, I found the passenger side window would open but the drivers wouldn't.

Anyway, AA arrived and found the 12v Battery was flat. He jump started it and recommended a run out and to keep an eye on it. I've been checking the Battery voltage using the fuse box terminal and it looks OK. I've had no problems since.

Searching around, this looks to be a pretty common thing with most Toyota hybrids. A relative had something similar on a Prius a few years back and he carried a small Battery in the boot in case it happened again. I've got a small 12v sitting spare too so can do that if needed.

I'd like to give the battery a charge using a mains charger but am finding it confusing, there so many different ways to do it and competing opinions. 

Has anyone charged up their 12v? Do you use the fusebox jump start point for +ve and a ground in the engine bay for the -ve? Lifting the seat is a bit more tricky to go direct to the battery under the rear seat. Some suggest 'remove the ground' when charging, what does this mean? I found that in a manual online.

Can anyone confirm the type of battery so that I can set my charger correctly? Sealed type?

I see Toyota recommend putting the car in 'Ready' for 60 minutes a week. I did this yesterday but it was a bit of a pain to sit there for an hour with no radio on. I read a book.......

Thanks in advance for any advice

 

J

[flash22]

It's an AGM deep cycle Battery it needs to be charged low (Current) and slow - ideally charge it off the car if you have a drive or garage a Battery maintainer aka trickle charger will do the job

it can take up to 48 hours to charge the AGM type batteries fully

[FROSTYBALLS]

Also see Toyota's guidance on Battery maintenance published during lockdown:

 

[Gerg]

As well as all the above, also:

The Battery is covered by the 5 year Toyota warranty in the UK (your profile says you're not in the UK, though), generally 3 years elsewhere.  In the UK the Battery is about £125 at a main dealers.  

I wouldn't worry about having the radio off in the situation you mention above, having it on will just mean the the engine cuts in fractionally more often - a negligible difference.

I think the suggestion of disconnecting the negative Battery connection ("remove the ground") when charging from an external charger, is to prevent any voltage spikes from the charger or an accidental incorrect attachment (polarity!) from damaging the rest of the car's electronics.

The specification/quality/expense of the battery means that it will suffer deep discharges better than an ordinary car battery.  But that same internal chemistry means that it doesn't charge quickly either.  It will not make a difference to how fast the 12v battery charges - stationary, in traffic, or belting down the motorway, are all the same to the 12v battery.  As long as the 'system' is 'on', the traction battery and inverter is in control of 12v battery charge regulation.  The engine obviously only runs to keep the traction battery topped up, not to charge the 12v battery directly.  This might be contrary to everything you have been familiar with on other cars.

Even when the dash indicator shows the high-voltage (traction) battery is discharged, it isn't really.  The car's electronics will not let the high voltage battery go below a 'real world' 40% charge.  This is to prolong the hybrid battery's life.  The dashboard  (traction) battery gauge shows the available charge in the traction battery.

Getting the battery charged from a mains 'smart' charger is usually the best option, if you can securely sort this out.  The battery can be left charging for hours this way, and the 'smart' charger will usually have a setting to optimize the charger output to the AGM battery requirements, but this last bit isn't so essential in the short term.

I've charged our Auris through the fuse box connection (with a 'smart' charger - so finely regulated) without any problems.  I've only disconnected the 12v battery when doing other work/repairs on the car. 

If, or when, you reconnect the 12v battery, don't forget that all the doors and boot will likely lock immediately.

[RedOnesGoFaster]

Thanks Frosty, I found the recommendation and performed the routine yesterday.

Thanks Gerg, I'm actually in the UK and it's a UK car, I'm just a little paranoid about some of the data sharing on these sites.

I think I'd better double-check my charger settings as it's pretty old, over 10 years I think. I'll make sure it charges on minimum rate. I'm not 100% comfortable leaving it going overnight so might just try it during the day tomorrow. I'll be sure to protect the charger in case it rains too!

 

Thanks for all your replies, I'll be a regular visitor here just hopefully not for solutions to problems!

 

J

RedOnesGoFaster!

[Starter Battery]

AGM profound cycle li-on Battery it should be charged low (Current) and moderate - preferably charge it off the vehicle in the event that you have a drive or carport a Battery maintainer otherwise known as stream charger will take care of the work it may take 24 - 48 hours to charge the AGM type batteries completely

[kenneth mcgreal]

Hi, I have a 2022 Yaris hybrid which suffered from flat Battery outages after 6 months with only a few days between usage.

The dealer eventually swapped the Battery in April 2023 and having been left idle for 3 weeks the same flat Battery problem has again arisen.

What type is the 12v battery fitted to the vehicle as there have been some conflicting answers on this AGM or Lithium?

Will the battery take a trickle charge via the +ve terminal in the fuse box, where is the -ve terminal? or is an engine earth point adequate.

Appreciate any advice.

[TonyHSD]

Yes, you can do recharge through emergency points under bonnet. Your Battery is lead acid or agm, but not li-ion. For infrequent use you will need to top up your Battery with a smart charger once every two weeks or even more often. There are many posts regarding this issue. There is useful information and ideas how to run cables from the Battery terminals under the rear seats and leave them sticking out ready to connect to charger when needed. Tons of information about it. 
Regards 

[Roker]

It takes me back to the 60s when we had DC dynamos and starting handles before alternators and we used to top up the Battery occasionally. Toyota is taking us back to that time, this should not be necessary

[Max_Headroom]

1 hour ago, Roker said:

It takes me back to the 60s when we had DC dynamos and starting handles before alternators and we used to top up the battery occasionally. Toyota is taking us back to that time, this should not be necessary

No its not and its not just Toyota hybrids that are having the problem the majority are.

The problem is some owners are not driving the car enough to keep the small 12v Battery topped up and sales staff are not being honest with potential owners by telling them they need to driver the car at least once a week to keep the 12v Battery topped up, they did exactly the same back in the diesel DPF (diesel particulate filter) days when they didn't tell customers if they drove in town at 30 mph all the time and never give it a good blast the DPF would eventually block and it would cost many hundreds of pounds to get it fixed or replaced.

 

I have posted the quote below from the other 12v thread some owners didn't agree saying they shouldn't have to search for problems i disagree a couple of minutes searching could have saved them the disappointment the first time their new car let them down and expense of  finding a way of stopping this happening.

Quote

Customers could also be blamed for not doing a little research before buying a hybrid a simple search for Toyota hybrid main problems brings up this - 

Problems With Toyota’s Hybrid Cars (5 Known Issues) | Motor & Wheels (motorandwheels.com)

 

The bottom line - 

Drive the car more than once a week and not just round the block and you shouldn't have any problems, if you dont want to drive just for the sake of it put the car in READY mode and sit in the car the ICE will fire up and shut down as required and the 12v Battery will be topped up.

If you dont drive regularly (at least once a week) a hybrid is probably not the right car for you.

If you still go ahead and buy one knowing this you will need a battery charger or solar charger or you will at some point find the car will not start.

If you cannot use either of the above buy a small jump pack and keep it charged and in the car (not in the boot) this will get you out of trouble should the 12v battery go flat.

 

 

 

 

[Roy124]

36 minutes ago, Max_Headroom said:

its not just Toyota hybrids that are having the problem the majority are.

I agree, not all, but many.  The Toyota solution however is not the best.  A better solution is better design.

My neighbour has a Kia.  He says you should not jump start in the event of a flat Battery.   There is a switch that allows the car to be started. 

I don't know how Kia has done this, maybe some feed from the HV system. 

[Mojo1010]

22 minutes ago, Roy124 said:

I agree, not all, but many.  The Toyota solution however is not the best.  A better solution is better design.

My neighbour has a Kia.  He says you should not jump start in the event of a flat battery.   There is a switch that allows the car to be started. 

I don't know how Kia has done this, maybe some feed from the HV system. 

Think Toyota need to install a bigger Battery and the tech mentioned from kia into these hybrids. 

I don't like not starting a non hybrid car even just after a week, let alone 3 weeks. 

[Cyker]

It does seem more common among hybrids and EVs - I wonder if it's something about the way the 12v Battery gets charged via DC-DC converters vs an alternator?

Alternators can deliver much higher bursts of current than the DC-DC converters used in electrified vehicles, so maybe it's somehow reconditioning the Battery, as opposed to EV/hybrids where the constant current maybe allows sulfation/scale to just keep building up over time...?

For balance, I should note my car is hitting 3 years old soon and I have had zero problems with the 12v Battery so far, and that's with me leaving the sidelights on all day once! And it's still the original battery that came with the car.

...

Now that I've said that I feel like I should buy a jump pack...

 

[Dala]

turn off intelligent smart charging while driving and the problem is over

but how?

[Roy124]

Yesterday I was monitoring my Battery monitor.  On our return journey immediately after starting it jumped to 13.9v for a few minutes before dropping to 12.7v.

@Cyker I wonder if it's something about the way the 12v Battery gets charged via DC-DC converters vs an alternator?

is probably on the money.

[Roker]

4 hours ago, Roy124 said:

I agree, not all, but many.  The Toyota solution however is not the best.  A better solution is better design.

My neighbour has a Kia.  He says you should not jump start in the event of a flat battery.   There is a switch that allows the car to be started. 

I don't know how Kia has done this, maybe some feed from the HV system. 

I always wondered why toyota cannot do this there's a huge Battery for the drive and a existing DC to DC convertor to 12v this could be used to start the car by having a switch until the ready light comes on

[TonyHSD]

Assuming the dc to dc conversation acts as a smart charger if the voltage supply drops below the usual 14.7v that most likely means that the batteries is in good state of charge and the system reduces the voltage to only trickle charge aka maintain healthy levels. The standard cars with alternators also have some voltage regulators and no matter what rpm they constantly supply 14v , not sure what happens there when you drive long journeys, is there anything to reduce voltage supply and only trickle charge the Battery? 

[Max_Headroom]

17 hours ago, Mojo1010 said:

Deleted

 

[Max_Headroom]

"I agree, not all, but many.  The Toyota solution however is not the best.  A better solution is better design" 

I agree but we are stuck with it so the points in my earlier post still apply

 

The bottom line - 

Drive the car more than once a week and not just round the block and you shouldn't have any problems, if you dont want to drive just for the sake of it put the car in READY mode and sit in the car the ICE will fire up and shut down as required and the 12v Battery will be topped up.

If you dont drive regularly (at least once a week) a hybrid is probably not the right car for you.

If you still go ahead and buy one knowing this you will need a Battery charger or solar charger or you will at some point find the car will not start.

If you cannot use either of the above buy a small jump pack and keep it charged and in the car (not in the boot) this will get you out of trouble should the 12v Battery go flat.

 

[Mooly]

12 hours ago, TonyHSD said:

The standard cars with alternators also have some voltage regulators and no matter what rpm they constantly supply 14v , not sure what happens there when you drive long journeys, is there anything to reduce voltage supply and only trickle charge the battery? 

Certainly on the older Auris and the charging is under constant control with the alternator changing from a nominal 14.4v down to around 12.5 volts.

https://www.toyotaownersclub.com/forums/topic/186724-stop-start/?do=findComment&comment=1492865

Whichever way you look at it, the 12 volt Battery in any car has to fall under the 'cyclic' use tag.

The one thing the Auris has is a sensor (a very very low value resistor) in series with the Battery feed and this resistor develops a volt drop as current is drawn. This is the little 'box' on the Battery terminal clamp.

The resistor value is so low that I think the drop is just 0.1 volt per 100A but that is enough for suitable electronics to calculate the energy removed from the battery (not so much in amp hours but by looking at Coulombs as a unit of charge) and it can therefore calculate how much energy to put back in. It is very accurate and works well.

If you have a partly discharged 12 volt battery and you find the voltage immediately rises to around 14.4 or higher when put on charge then that implies that either you have a very very high capacity charger (cable of delivering many 10's of amps) or the battery has significant internal resistance (deteriorated).

Again on the Auris, a discharge test of say headlights, heated window, fog lights etc all being left on without the engine running pulls a very high current from the battery. Fwiw a fully charged and healthy battery will support that level of loading for a considerable time. Where is gets interesting is when you start the car after doing that. The loading is so high on the alternator (so it becomes very hard to spin round) that the engine immediately stalls. This is because the battery is taking all the current the alternator can deliver which could be as high as 50A or more and the learned idle position of the engine can not support that extra unexpected mechanical loading. That high current soon tails off and the more deteriorated the battery and the quicker it does so.

 

[Cyker]

The thing with the voltage is it just has to be high enough to overcome the battery's nominal voltage in order to push charge into it, then the rest is all about current - The higher the current, the faster it will charge.

This is why with EVs, there is such a broad range of charging speeds despite the fact almost all chargers are 400v - The higher powered chargers just up the current to stuff more charge in faster (Although that brings its own problems, like the charge cab;es getting very hot and needing active liquid cooling!!)

AFAIK the DC-DC converters are constant-current chargers, whereas an alternator's output will vary depending on RPM (Hence why the jump start instructions for most conventional cars recommend you rev the engine to at least 2000rpm before trying to start the other car)

 

[Roker]

On 11/5/2023 at 5:35 PM, Roker said:

I always wondered why toyota cannot do this there's a huge battery for the drive and a existing DC to DC convertor to 12v this could be used to start the car by having a switch until the ready light comes on

Better still why have a 12v Battery at all. Do all the 12v through DC to DC converter 

[Roy124]

6 minutes ago, Roker said:

Better still why have a 12v battery at all. Do all the 12v through DC to DC converter 

True to a point.   Lots of services such as air con and motors run on 12v but only after the system is live.

You need a 12v storage system (battery) to energise the DC-DC system.  That 12v system is also required connect with the mothership and carry out many functions. 

I believe even state of the art EV have 12v batteries.

[Cyker]

I assumed it was a safety requirement - Normally the whole high-voltage system is isolated when the car is 'off', so you need the 12v system there to 'boot' the high voltage system

However, some manufacturers have the car high voltage system connected all the time (e.g. Teslas in Sentry mode) without penalty, so I don't know anymore...

It would be less practical with our hybrids tho' - e.g. My Mk4 only has a 700Wh traction Battery, and that would drain fairly quickly if it took over the 12v's job of being on all the time, which would be a far worse situation than the 12v Battery running out!!! (Because with the 12v, you can jump-start it, but if the HV Battery runs out then you're screwed until your car can be carted to a dealer and the mysterious and mythical Toyota Traction Battery Charger delivered from its distant and hallowed storage location to said dealer...)

 

[Stobie]

On 11/5/2023 at 12:54 PM, Roy124 said:

I agree, not all, but many.  The Toyota solution however is not the best.  A better solution is better design.

My neighbour has a Kia.  He says you should not jump start in the event of a flat battery.   There is a switch that allows the car to be started. 

I don't know how Kia has done this, maybe some feed from the HV system. 

Kia and Hyundai only use one Battery with a small portion reserved for starting etc. If that small portion goes flat you press a button on the dash and the main Battery dumps a load of power into it. Dead simple and a really good system, I had it on my 21 reg. Tucson Hybrid and used the button 3 times in 18months, twice after leaving the dash cam plugged into the permanently live USB port before I discovered the problem and the other time after leaving the ignition in accessory mode while I washed the car with radio etc on.