12v battery problem

[Children's Writerman]

Our 2008 Prius hasn't moved for over three weeks, since we've been in lock-down. Tried to move it to get something out of the garage and the 12v Battery is completely dead - couldn't even open the door so had to use mechanical key.

I have a trickle charger. I removed the Battery cover and disconnected the -ve strap to frame and connected the charger. Switched on charger and the amperage dial (marked 1-4) immediately shot up to the end stop, sat there for about ten seconds then fell back to zero. I have repeated several times - same result. 

Deaceased Battery? Any suggestions what to try next?

[FROSTYBALLS]

Moved to the Prius club.

[Mick F]

Dead Battery is my first suggestion.

Batteries only last a few years, and if they fully discharge that could be the end of them.  Keep them used daily, and they'll work well enough even though they may self-discharge somewhat overnight.  Give them a day or so, or even a week, and they won't be recoverable.

Mick.

[kithmo]

Try disconnecting both leads from the Battery and charging it, I suspect the capacitor box (black box) at the side of the Battery is drained and trying to charge off your charger. The capacitor is trying to pull a lot more volts than your charger can handle and the charger's overload protection circuit is kicking in. 

[PeteB]

Also, it could be trying to run one or more electric compressors for the brake hydraulics or other systems.

[Children's Writerman]

Many thanks for the suggestions but, alas, no cigar. I disconnected the Battery completely and it still won't charge. Methinks it's new Battery time. However, as the vehicle is unlikely to be driven for a couple of months I'm not sure whether it's worth replacing now or waiting until end of lockdown - whenever that might be.

Thanks again.

[TonyHSD]

Hi,

If you can source a replacement Battery now maybe is better to buy one, fit it into the car and once a week or every two weeks put the car in ready mode and let it run for 30 min. It is not recommended to leave a car without use for a long period of time, traction Battery will need charge too and the engine will need to run to keep oil seals lubricated, otherwise oil leaks are very likely and they are expensive to fix. 
Regards 

[flash22]

The 12v hybrid batteries are the AGM type and need a long and slow charge it could take days to charge with a normal charger (set yours to 1) but  your best of with the correct type of charger

If you google "AGM Battery charging" there is plenty of advice

[Children's Writerman]

I just checked. The Battery was replaced in August 2017, so less than three years old. Is that normal?

Re setting my charger,  it doesn’t have any settings - not even an on/off switch.  This is starting to look like I need a new charger too.

[PeteB]

Just now, Children's Writerman said:

...replaced in August 2017, so less than three years old. Is that normal?...

No, not unless it's been left flat either once for a few days, or several times for shorter periods.

If it's not been flattened, I'd check to see if it's covered by a warranty - some are, depends where you got it.

[QuantumFireball]

I've ordered one of these chargers after finding a lot of recommendations: www.amazon.co.uk/CTEK-MXS-5-0-Reconditions-Motorcycle/dp/B00FC42HAA

It seems more intelligent than other chargers and may give better results at reviving a dead Battery. It has a mode specific for AGM batteries too.

[Joseph D]

That CTEK MXS 5.0 is the one I have and it is a good charger.  I use mine all the time and have not regretting getting it.  I consider it an essential tool box item and wouldn't be without a charger, now.

[Gerg]

If it's of any use, this is a copy of the owner's manual for the CTEK.  I don't have one, I was just interested to see what it said. 

(I'm sure it's available on their website too, but anyway.)

 

 

[QuantumFireball]

The manual is available here: https://www.ctek.com/storage/ma/3f8cf34932cc46889f1d189ca335379c/cd879e35fdd145898b6b99c549c40292/pdf/7F18A34BA7A2CF91AC9F5404D8EB07FE2E6CAA66/MXS_5.0-manual-low-UK-EN.pdf

[kithmo]

I got the CTek 3.8A one, I had the Gen 3 when I bought it and ISTR IIRC there was something about a 4A max charge rate on the car.

I used it to recondition a totally flat AGM 12v mobility scooter Battery, which took 3 goes to get it to start charging. The charger will kick off if the Battery is not accepting a charge but leaving it half an hour or so then trying again eventually got it to start charging on the 3rd go. So as you've got plenty of time to mess about with it and you're going to buy a new charger anyway, it's worth buying one of these chargers to try and get the old Battery going again before you buy a new one and if it doesn't work then a new one it is. Also you can leave the charger connected when the car's not in use to keep it topped up, it will automatically condition the battery.

[Chris Dance]

I had a Battery problem this morning. The car would not start: warning said 12v Battery. The lights flashed on and off. It was a week since the car was run.

I called Toyota breakdown. The AA were at my house in 20 min. The AA man got the car started but following his checks he said the Battery was shot. Luckily he had a new Bosch 12v battery on his van (5 year warranty) which he fitted to the car. The AA man said as you have only being short runs the battery life had gone. The whole job was done in 30mins. Great prompt service from the AA. The old battery was 3 years old. You need to run a Prius regularly on a decent run to avoid this problem. 

[Children's Writerman]

Thanks Chris. I can see this being an ongoing problem for us. Since we got a second car (an indulgence for me), the Prius has been relegated to second citizen. It only really gets used when my wife drives to a (local) tennis match. I am looking into getting one of these conditioning chargers. I'm not sure whether I should use it regularly, to keep the Battery in good condition and, if I do, whether I have to disconnect the Battery from the car's electrics - inconvenient because it means reprogramming the radio etc. Maybe we should trade the Prius down for a cheap, possibly electric, runaround. 

[Gerg]

I have not read about a situation where leaving a Battery on a 'maintenance' charge has caused any damage to a Toyota hybrid, or any other car's electrical system.  Perhaps others know different?

If you post a picture or description of your existing charger, then perhaps someone will recognize it and tell you if it is poor/good/excellent model to use in this situation.

Just as background - 

Leaving any conventional 12v Battery in a heavily discharged state for any length of time will shorten its life massively - the Battery is better suited to working in the upper end of its capacity, although the genuine Toyota fitment in these cars is a higher spec. than other similar batteries so will suffer this better than some, said a man at Yuasa (the OE battery manufacturer) technical dept.

The Toyota service 'Menu' price for your battery might be cheaper than going elsewhere, certainly this is the case for Yaris/Auris batteries, as there is one fixed price at Toyota for all variants of, say, an Auris i.e. petrol, diesel, hybrid. 

Your battery is very likely to be the same model as is fitted to a Yaris/Auris etc.  But the price on the menu may be more for the same battery sold for a Prius.  In your situation, I am not sure if there is an easy way of buying a 'Yaris' battery at the dealer (possibly the same exact part as the Prius - does anyone here know for sure?) and saving a small amount of money by being cheeky?

Was your last battery from the dealer?  It may be that a 'normal' (i.e. not an AGM one) battery was fitted last time if it wasn't bought through the dealer, in which case a shorter working life is to be expected, sadly.

Amazingly, the dealer prices for the OE Yuasa battery are cheaper than I could find for the exact same item on eBay.  For comparison, the menu price for an Auris battery is £125 at the dealer, a Yaris one is £5 or £10 less, I think.

HTH.

[QuantumFireball]

1 hour ago, Children's Writerman said:

I am looking into getting one of these conditioning chargers. I'm not sure whether I should use it regularly, to keep the battery in good condition and, if I do, whether I have to disconnect the battery from the car's electrics - inconvenient because it means reprogramming the radio etc.

CTEK MXS chargers should be safe to use in situ and leave connected for maintenance. Mine just arrived this morning but I haven't set it up yet.

1 hour ago, Children's Writerman said:

Maybe we should trade the Prius down for a cheap, possibly electric, runaround. 

BEVs still generally have a lead acid 12V Battery for auxiliary equipment (and to "start" the car), so getting one will not necessarily avoid this problem.

[Children's Writerman]

1 hour ago, QuantumFireball said:

 

Hi, thanks for your comments. It's useful to know I can leave a smart charger connected without disconnecting the Battery.

Re BEVs, as it happens, we already have one. That's our other vehicle. I leave it plugged in whenever not in use. I must say, I thought the 12v Battery was maintained, as necessary, from the main automotive Battery whether or not the vehicle was driven but I could be wrong. I also don't understand why the 12v should be needed to start the vehicle. Electric motors don't need independent starting. Surely they just go when you apply electricity? 

[Catlover]

Hi Keith, what car is your BEV and how do you like its performance ie distance you can travel on a charge etc

[QuantumFireball]

1 hour ago, Children's Writerman said:

Re BEVs, as it happens, we already have one. That's our other vehicle. I leave it plugged in whenever not in use. I must say, I thought the 12v battery was maintained, as necessary, from the main automotive battery whether or not the vehicle was driven but I could be wrong. I also don't understand why the 12v should be needed to start the vehicle. Electric motors don't need independent starting. Surely they just go when you apply electricity? 

It depends on the car as to whether there will be any maintenance of the 12V Battery if left plugged in and the traction Battery is not charging. In my Prius Plug-in, I understand the 12V Battery is only charged when plugged in if the traction battery is charging - but I'm doing 4 km round trips to a supermarket every two weeks or so, so there's very little charging of that going on. Otherwise it is only charged when the car is running, as a normal Prius does.

As to why the 12V system is required to start the car: There's no big mechanical switch in your car to turn on the high voltage power, like there is for example the mains switch for an electric cooker at home. The high voltage system is turned on by relays operated by a 12V circuit, in conjunction with your keyless entry system and immobiliser - which are operating all the time (to some extent) but only require a low voltage and low power to work. Even if the car was turned on the old fashioned way i.e. with a key and "ignition" barrel, there'd still need to be a 12V relay to turn on the HV stuff as the contacts on a typical ignition barrel couldn't handle high voltages - there'd need to be a big hefty switch somewhere to do it without a 12V relay (I think).

[Children's Writerman]

QuantumFireball, thanks for another informative post. Yes, a relay for the high voltage makes sense. I checked and my car does monitor and recharge the 12v Battery even when stationary.

Catlover, my BEV is a Tesla model S70 (I said it was an indulgence), which I picked up second hand. It's now approaching four years old. The Battery still performs as per spec. when new. On a flat road, I easily get 3 miles per kWh, so that's 210 in total. Of course, that's hypothetical. You never want to run down to zero. On a long run, I'm looking to recharge every 150 miles or so. We had a trip to North Yorkshire planned before lockdown - about 300 miles from home. I had planned a 15 minute coffee break at Warwick Services and a 30 minute lunch break at Woodall, arriving at my destination with 30% left "in the tank". You just plan journeys slightly differently. I'm retired so I'm happy to take regular breaks. How do I like it? The most wonderful car I've ever owned, reawakening my dormant love of motoring. 

[Chris Dance]

When you disconnect the 12v Battery you will lose your "settings". The AA have a box of tricks they connect to the car so no settings are lost when disconnecting the Battery,

[ian999]

I received the following email from our Toyota Main Dealer today regarding Batterys going flat.

 

Vehicle Maintenance Tip

The majority of us, with the exception of key workers, are now isolating at home and only venturing out for basic essentials, which means that our cars are parked and being rarely used – if at all. If your car has not been used for two weeks the last thing you’ll want to worry about is a flat Battery! We’re experiencing a few customer issues directly related to this and you may want to consider starting your car every few days and allowing the engine to run for ten to fifteen minutes to top up the charge. The car does not need to be taken out on to the road, should not be in a garage or confined space and for security it should not be left unattended. If you have two cars in the family it may be worth alternating between vehicles when you do venture out for essential reasons. To be clear, we’re not advocating wasting fuel or polluting the environment – just trying to help with the unnecessary hassle of charging or replacing your Battery. I hope that this once a week inconvenience will save you considerably more time and hassle when life returns to some form of normality.