Planned replacement of 12v battery

[darrude]

Is it worth changing the 12v Battery as part of maintenance, at say 5 years old, to prevent issues with 12v failure?  

 

 

[matt8]

Good question.

As well as everyone else's ideas, I'd be particularly interested in hearing from @Britprius on this matter.

How well can a trickle charger extend life of a Battery?

[Herbie]

'Preventative maintenance' it's called and yes, of course, if you can afford it and want to do it then go ahead. Having worked in maintenance all my life (first as an electrician and then a telephone engineer) it's the sort of thing that I routinely do as there just can't be a downside to doing it.

[reeac]

There is a downside ..... cost. If you want max. reliability then it's a good policy. My recent  experiences with batteries have been one that did 15 years with no failure and no charging from an external source (and on an annual mileage of only 3,000) and one that did 10 years before it started showing some problems but never failed to start the car. My sister in law got her car Battery changed at 6 years and I thought that for her, aged 75, that was sensible policy. Horses for courses.

[Herbie]

21 minutes ago, reeac said:

There is a downside ..... cost.

Not sure I agree with that Roger, which is why I qualified my statement with "if you can afford it and want to do it then go ahead".

If you can afford it and want to do it then it's not a downside. If you can't afford it or don't want to do it, then don't.

Most car batteries will indeed last longer than five years, some quite considerably longer, but given the importance of the 12V Battery in a hybrid car and the abundance of problems it can cause when it begins to fail, I think I'd err on the side of caution and replace it after five years if I could afford it, purely as a precaution.

[ColinBarber]

If you haven't had to charge it before then I'd not replace at 5 years, maybe after 8 or 10.

If it has been discharged below 1/4 capacity on more than one occasion then that could of weakened it and therefore think about replacing it.

Not just cost but also environmental issues are reasons not to replace things before needed.

 

There is always the danger than you swap out a perfectly good Battery and replace it with one that has a manufacturing detect which lets you down within the first few months - wouldn't be the first time that has happened.

[reeac]

My experience to date has been overwhelmingly with conventional rather than hybrid cars. I believe that the Lexus hybrid 12v Battery is charged from the high voltage traction Battery but I don't know whether it is given priority so as to always be fully charged. Even so, if it eventually fails it might just discharge the traction Battery causing damage to it. On the other hand there may well be built in safeguards against this happening. Probably with such a complex car it's best to err on the side of caution and replace the 12 volt Battery after around 6 years. The Toyota Hybrid Drive system has been around for about 10 years now so dealers must have some experience of 12 volt Battery behaviour.

[darrude]

That's for the replies.  I think ill change mine on its fifth birthday. On a conventional car you kind of get a feeling the Battery is about to fail at the beginning of winter, guessing it won't be a apparent on this car. I'd rather play it safe, as have missed a flight in the past because of a flat Battery....

[Uti]

37 minutes ago, darrude said:

That's for the replies.  I think ill change mine on its fifth birthday. On a conventional car you kind of get a feeling the battery is about to fail at the beginning of winter, guessing it won't be a apparent on this car. I'd rather play it safe, as have missed a flight in the past because of a flat battery....

Good decision!

Uti

[ColinBarber]

51 minutes ago, reeac said:

Even so, if it eventually fails it might just discharge the traction battery causing damage to it. On the other hand there may well be built in safeguards against this happening. 

Thankfully that is impossible. The 12v Battery isn't directly connected to the traction Battery.

[reeac]

I seem to recall reading that it's connected via a DC to DC converter to reduce the voltage from 230 to a suitable level.

[Britprius]

6 hours ago, matt8 said:

Good question.

As well as everyone else's ideas, I'd be particularly interested in hearing from @Britprius on this matter.

How well can a trickle charger extend life of a battery?

Well Matt this is not as simple a question as it may sound, but I will keep it as brief as I can.

All lead acid batteries have one thing in common. They do not like to be stood partially charged. In this state the plates of the Battery are prone to sulphation " a hard white lead/sulphur compound that if left cannot easily be turned back into acid no matter what some charger manufacturers say". This compound acts as an insulator, and also reduces the strength of the acid.

If a hybrid is used every day for a reasonable length of time the 12 volt Battery will always be at or close to fully charged so no reason to trickle charge it.

If the car is used only once a week then trickle charging while the car is idle would be beneficial because the car discharges the Battery while standing, and the Battery has some self discharge.

If the car is used even less frequently I would say it is essential to trickle charge if you want a reasonable Battery life. 

The 12 volt batteries that Toyota/Lexus use in the hybrids are AGM batteries "absorbed glass mat". This means there is no free liquid acid in the Battery as in the case of ordinary normal car batteries "flooded lead acid". So there is much less acid available, and is reduced in strength quicker when sulphation takes place thus reducing the available capacity more quickly with AGM. AGM batteries tend to have a greater amp hour capacity for a given physical size, and have a slightly higher output voltage of circa 14.2 volts against the flooded Battery of 13.8 volts. It is important therefore that the charger used is suitable for AGM batteries as some flooded Battery chargers do not put out enough voltage to fully charge AGM batteries. The Toyota batteries are known for not recovering well from being deeply discharged.

If you want a Battery with a higher amp hour capacity of the same physical size to the OEM the batteries used in disability scooters not only have much higher capacity, but are much more ruggedly built, and designed to be deep discharged on a regular basis with little or no damage. The only downside is that they do not have standard Battery terminals. The Toyota 45 amp hour Battery can be replaced with a Battery of between 55, and 60 amp hours. for the same dimensions. 

John. 

[Britprius]

22 minutes ago, reeac said:

I seem to recall reading that it's connected via a DC to DC converter to reduce the voltage from 230 to a suitable level.

This is so, but only when the car is in ready mode. In all other modes the high voltage Battery is completely isolated from the rest of the car. 

John.

[ColinBarber]

16 minutes ago, reeac said:

I seem to recall reading that it's connected via a DC to DC converter to reduce the voltage from 230 to a suitable level.

Yes the inverter assembly boosts 230.4 VDC from the hybrid Battery to 650 VDC and then to 3 phase AC to power the electric motor and also contains a DC-DC step down converter to provide 14 VDC for the car's electrical system and to charge the 12 V Battery.

[ColinBarber]

6 minutes ago, Britprius said:

The Toyota batteries are known for not recovering well from being deeply discharged.

Toyota state that their normal flooded batteries shouldn't be discharged more than 50% and AGM's used in all current hybrids no more than 70% discharged (30% remaining).

[Britprius]

51 minutes ago, ColinBarber said:

Toyota state that their normal flooded batteries shouldn't be discharged more than 50% and AGM's used in all current hybrids no more than 70% discharged (30% remaining).

Yes this is generally the accepted formula. Many disability batteries are rated to 100% discharge. 
If you have a Battery of 45 AH a 70% discharge would be 31.5 AH of usable capacity.
If you have a Battery of 60 AH a 70% discharge would be 42 AH of usable capacity an increase of 25%.
I use a mobility Battery in my GS450H rated at 110 AH instead of the OEM 70 AH.

John.

[darrude]

Interesting comments, my car only really gets used for a long commute Monday then Thursday or Friday. This is bad for the Battery then and will deteriorate quicker than average?

[Britprius]

10 minutes ago, darrude said:

Interesting comments, my car only really gets used for a long commute Monday then Thursday or Friday. This is bad for the battery then and will deteriorate quicker than average?

Your Battery I would say will be in the average range as the longest period of inactivity is only three days.

John.

[malcolmw]

A colleague of mine has a 3 year old NX300h which she has had from new. Although not an IS, it has the same running gear ref. batteries etc.

She has just had the 12V Battery replaced under warranty. She only does short journeys of, say, 4 miles maximum and only does 3,000 miles per year maximum. Whether this is an actual failure or just undercharging is a moot point.

[Britprius]

The batteries do not have a good start in life. After being fitted to the new car the car is driven off the production line to storage and awaits transport to the docks. The car is driven onto transport, and driven off at the docks awaiting a ship. No long runs so far.
The car is driven onto a ship taking weeks to arrive at the UK dock where it is again driven to a parking area. It is then driven onto a delivery vehicle to go to the dealers where again it is driven off. 

At this point the dealer is supposed to charge the Battery, but how many do? The car may then sit in a showroom for people to open doors and look at or a storage area. It may be driven into the workshop for a PDI. All this is far from ideal for the Battery.

Some luck customer then gets to take the car home with a Battery that is well discharged, and has been for weeks possibly months. 

John. 

[Bluesman]

1 hour ago, Britprius said:

The batteries do not have a good start in life. After being fitted to the new car the car is driven off the production line to storage and awaits transport to the docks. The car is driven onto transport, and driven off at the docks awaiting a ship. No long runs so far.
The car is driven onto a ship taking weeks to arrive at the UK dock where it is again driven to a parking area. It is then driven onto a delivery vehicle to go to the dealers where again it is driven off. 

At this point the dealer is supposed to charge the battery, but how many do? The car may then sit in a showroom for people to open doors and look at or a storage area. It may be driven into the workshop for a PDI. All this is far from ideal for the battery.

Some luck customer then gets to take the car home with a battery that is well discharged, and has been for weeks possibly months. 

John. 

My original Battery on my LS was 14 years old when it had to be replaced.

[ColinBarber]

2 hours ago, Bluesman said:

My original battery on my LS was 14 years old when it had to be replaced.

Early Toyota hybrids had very small batteries that were deep-cycled too often so didn't last. Ones this decade don't suffer as much but still don't last as long as a big Battery found in something like the LS.

For their size they are quite expensive though, the odd shape and need for ventilation, because most are located in the cabin, means there isn't a big choice.

[PRT68]

Having a 2007 Prius, and previously using it as a Taxi for 5 years, I would say yes, replace it. The inconvenience of getting into the car and seeing the 'red triangle of death' is annoying, especially if you need the vehicle for work. The only problems us drivers had seemed to revolve around the 12v Battery, causing odd electrical glitches. The majority of us would replace after 3 years, or when purchasing a 'new' vehicle if the age of the Battery was unknown. For about the cost of £90, the loss  of a mornings takings and inconvenience was avoided. It was a small regular price to pay for the otherwise superb reliability.

[Britprius]

15 hours ago, Bluesman said:

My original battery on my LS was 14 years old when it had to be replaced.

The LS has I believe a normal flooded lead acid Battery using a normal starter motor as it is not a hybrid so not so prone to the problems, but not immune. It is also possible that your Battery was replaced at the dealers before being sold.
I am not saying all the batteries will fail just that they are likely to suffer some damage at the very start of there life.

The problem with a hybrid is that we get no warning of a weak Battery as we do not hear the starter struggling to turn over the engine. This is enough for most people to check the Battery.
With a hybrid the first sign of problems is usually a failure to boot into ready mode possibly with false codes.

John

[reeac]

On 9/8/2018 at 4:44 PM, Britprius said:

Yes this is generally the accepted formula. Many disability batteries are rated to 100% discharge. 
If you have a battery of 45 AH a 70% discharge would be 31.5 AH of usable capacity.
If you have a battery of 60 AH a 70% discharge would be 42 AH of usable capacity an increase of 25%.
I use a mobility battery in my GS450H rated at 110 AH instead of the OEM 70 AH.

John.

I own a 1958 MGA sports car which has two 6 volt batteries in series to power the 12 v system. After restoration between 1981 and 1983 the first pair of batteries lasted 11 years and the second pair 10 years. After that I started having trouble with batteries which was eventually cured by converting to using a single 12 v Battery. I believe that the problem was that the more recent 6 v batteries were intended for use in golf buggies and so were deep cycle and couldn't supply enough current for cold starts. I expect that true car type 6 v batteries are still obtainable but it's a possible pitfall if choosing deep cycle batteries. So called leisure batteries provide enough CCA (cold cranking  amps) and have reasonable deep cycling ability and I always used them on my boat, finding that they lasted about 10 years.