Chance It?

[cass1]

Hello all, my 2011 Prius is going to be standing in a garage for one month. Do I chance leaving it connected up or disconect the Battery?. Has anyone found any difficulties after a similar period?.

[timberwolf]

For the HV Battery no problem, it's good for 3-6 months.

For the 12V Battery, it depends on a lot of variables. Age, SOC and usage pattern are possibly the main variables. The time of year that you plan to leave the car could also be a factor, e.g. whether it is cold or hot will also determine how long it can be left and still be able to power up the car.

If your car does survive 4 weeks and that is reasonable on a new 12V Battery fully charged, it will shorten the life-span of the battery.

[ian rooke]

Hi can you explain why the Battery life will be shortened if it survives 4 weeks of non use.

[timberwolf]

Because the standby current used to maintain the car alarm and central locking radio receiver is slowly flattening the Battery. If you leave the car for 4 weeks then you've reduced the State of Charge in the Battery to a pretty low level - nearly flattened.

I don't know the science behind it, I just know it is bad for a lead-acid Battery. If I find a good article I'll post a link.

[Opifex]

FWIW I've left my 2010 Gen3 in the garage for more than four weeks with no problems.

Before you leave it might be a good idea to read the manual to learn how to do a jump start, just in case,

[Beretta]

Batteries thrive on charge and discharge and if low at the end of a four week period, will quickly charge up to correct levels without any detriment to the Battery, as the drain has only been a gradual one.

If left in a discharged state for loooooooong periods, then a problem (Sulphation) can occur.

I too have left mine parked for over three weeks at the airport several times whilst on holiday and the Battery indictor was still way up in the blue area when I returned to the car and it started first time.

[Ancient Nerd]

I seem to remember some people having trouble with the boot light not switching off properly. It might be worth removing the bulb just to be sure.

[kithmo]

I too have left mine parked for over three weeks at the airport several times whilst on holiday and the battery indictor was still way up in the blue area when I returned to the car and it started first time.

The Battery indicator is for the HV Battery not the 12v, the HV Battery should last 6-9 months if well charged when left.

I would say the 12v would be ok for 3-4 weeks on a 2011 car, but for peace of mind you could disconnect the 12v and leave the car unlocked if it's locked in a garage, you will lose your radio presets and see pages 416 to 419 in the user manual for info on the procedures when reconnecting.

[ian rooke]

Hi as Beretta says batterys last longer if you use them you can reduce the current drain by disabling the alarm ,Taking out the boot light will not make to much differance as the dash warning light stays on as can the interior light.On my Gen2 leaving the boot ajar flattened the Battery in less than 6 hours. (Not done it yet on my Gen 3,) I believe you can get a LED light to fit the boot light which will reduce current drain.

[Sagitar]

I seem to remember some people having trouble with the boot light not switching off properly. It might be worth removing the bulb just to be sure.

The Gen3 model has a mechanical switch on the boot light and I leave it switched off permanently unless I need it.

[Ancient Nerd]

I seem to remember some people having trouble with the boot light not switching off properly. It might be worth removing the bulb just to be sure.

The Gen3 model has a mechanical switch on the boot light and I leave it switched off permanently unless I need it.

Three years, 92,000 miles and I hadn't noticed! I'll switch it off immediately. Even though it has never caused trouble so far.

Thanks Sagitar.

[johalareewi]

I too have left my gen3 for weeks at a time without any problems. The longest is 4 weeks.

[timberwolf]

I found a good site about lead-acid batteries for anyone who may be interested. I understand the 12V Battery used in the Prius is the Starter type of Battery.

http://batteryuniversity.com/learn/article/lead_based_batteries

[Sagitar]

I found a good site about lead-acid batteries for anyone who may be interested. I understand the 12V Battery used in the Prius is the Starter type of battery.

http://batteryuniver...based_batteries

Since it isn't actually used to turn over the ICE, logic would seem to suggest that a deep cycle Battery might be better for the Prius?

There are threads on Priuschat that describe improved performance from the Optima Yellow Top Battery, which I think is a deep cycle type.

I am not sure why Toyota would choose to fit a starter type Battery, unless it is simply a question of cost reduction.

[timberwolf]

I think it's still the starter kind of Battery (or possibly combined?), at least according to this press release page "OPTIMA YellowTop^® is ideal for any application that demands heavy cycling and cranking power...".

http://www.johnsoncontrols.com/content/us/en/products/power_solutions/power_solutions_presskit/products/optima.html

[Sagitar]

Yes, sorry. I did think that mentioning the Optima might confuse the issue. Their advertising does seek to emphasise its versatility, but it is essentially a deep cycling Battery developed from the Red Top which is their preferred starter Battery - look here http://www.dcbattery...ima_yellow.html

The Red Top gives 720 CCA amps whereas the Yellow Top gives 450 CCA amps so they have certainly diminished the cranking capacity of the Battery to achieve deep cycling.

I think the role of starter batteries has changed a great deal with the introduction of systems that continue to put a load on the battery even with the car switched off. Examples on the internet demonstrate that it isn't only the Prius that can flatten its battery if it is left standing for a few weeks. It could be that batteries like the Yellow Top that allow deep cycling while still achieving reasonable cranking power will become more popular.

[timberwolf]

Yes, thank you, the marketing is confusing.

They sound good, if they can cope with being left under-charged for long periods?

They are a lot more expensive, I could replace my Battery a couple of times over with a Bosch S4 Battery (accepting that I would have to modify the vent tube elbow piece) for the cost of one Optima.

If I recall correctly, there was also some doubt over whether the Toyota Prius vent tube fitted an Optima Yellow Top Battery bought in the UK?

[korat102]

A 2011 car may be ok for a month...your choice.

On an older one, I wouldn't chance it. Actually I, personally, wouldn't chance leaving any Prius for a month - once bitten twice shy as they say. If you're going away, the best bet would be to disconnect it. If you'll still have access to the thing, I'd be inclined to leave it connected but put it on charge after three weeks. The 12v Battery on a Prius is tiny, it can't supply the current needed to maintain the radio, etc. for that length of time without almost completely discharging and once discharged its life can be shortened dramatically as a lot of us have found to our cost.

[cass1]

Thanks for all your advice and input. I think I will err on the side of safety and disconnect the Battery.

[Hicardo]

In 2011, I left my 2009 Gen3 Prius for 8 weeks with no special precautions. On returning, she fired up first time, no problem. The Prius goes into a power save mode after several days as one of the main draws on the 12v is the keyless entry. It disables this itself after around a week.