Flat Battery

[Catweazle]

Not used the RAV for 2 weeks exactly and the Battery is completely flat. Not even enough power to unlock the doors. When I did unlock them manually with the key, the indicators started manically flashing, albeit very dimly. Connected up the Battery charger and the indicators stopped after a couple of minutes then the alarm went off.

I experienced a similar thing last winter when I didn't take it out in the snow for a couple of weeks but the weather's barely even cold at the moment. The Battery was changed last winter also so is this normal or is something draining the battery?

HELP!

[CharlieFarlie]

Firstly is the Battery still under warranty ??.. If You have a permanent drain then it would flatten enough not to start in any weather.. Is the Battery the right size and power ? Man enough ?

You could take the car to any Battery distributor and ask for the battery to be load tested. HTH

Wee Charlie.

[webleymk3]

Na. Definately not right. My in laws were in portugal for 6 weeks and both their Toyotas started first time.

Either a drain or a duff Battery.

[IanXT4]

I have had similar problems and have a theory

Here goes -

The Battery on the petrol XT4's is small and they are fitted with an alarm which includes a microwave sensor etc and I suspect it has a small but appreciable parasitic drain.

If you use the car for lots of small journeys and then leave it, the Battery starts its "storage phase" way less than maximum charge. They used to say "back in the day" it took 15 minutes of running to recover the charge from a start ? These days with no ammeter its hard to tell.

Anyway, if you leave the car with a partially charged Battery after a week or so of parasitic drain the battery is now in no fit state to give the 100's amps required at start-up. Interestingly a friend of mine who has a LR is having exactly the same problem. Battery tests fine,no fault found with the car, however, he uses it for lots of short journeys ?

The answer for me was to wire a charge point in the boot, now I can run an extension lead to the car and "leave it on charge" in seconds.

[CharlieFarlie]

I have had similar problems and have a theory

Here goes -

The battery on the petrol XT4's is small and they are fitted with an alarm which includes a microwave sensor etc and I suspect it has a small but appreciable parasitic drain.

If you use the car for lots of small journeys and then leave it, the battery starts its "storage phase" way less than maximum charge. They used to say "back in the day" it took 15 minutes of running to recover the charge from a start ? These days with no ammeter its hard to tell.

Anyway, if you leave the car with a partially charged battery after a week or so of parasitic drain the battery is now in no fit state to give the 100's amps required at start-up. Interestingly a friend of mine who has a LR is having exactly the same problem. Battery tests fine,no fault found with the car, however, he uses it for lots of short journeys ?

The answer for me was to wire a charge point in the boot, now I can run an extension lead to the car and "leave it on charge" in seconds.

So Battery not Man enough then ??

Is Your charger of the Opitimate variety ? IE a Battery tender rather than a dedicated charging unit ?? These are safe to connect to a Battery while said battery is still on the car where as I think a normal charger can play havoc with the cars electrical systems ???

Wee Charlie.

[IanXT4]

Yep, us petrol heads have to make do with toy batteries.

I think I have posted before my preference for car chargers, they are Aldi German/Chinese copies of CTEK chargers.

All the sophistication, modes, pulse charging, trickle etc etc but at a faction of the price.

To be honest modern car electric components have some serious transient protection specs.

I would be very surprised if you could damage them by connecting any type of car charger.

[Jamesbelfast]

Get the Battery load tested at least 3 times in succession. If there are any duff cells it will show. Go to a decent Battery supplier or auto-spark. Also get the alternator output checked. Then get the ampage of the residual voltage checked just in case there is a parasitic voltage drain.

As alarms work on the voltage drop principle it will activate when the Battery voltage lowers to around 10 - 11 volts.

[IanXT4]

Well got a bit bored this afternoon , so dug out an ammeter and placed it in series with the Battery to measure the actual parasitic current drain.

After switching on the alarm and allowing it to settle down into a "standby mode" the drain seemed to be around 45ma - 50ma.

This (if correct) ties in with what I suspected.

45ma is 0.045A which for 1 hour is 0.045AH

24 hours x 0.045AH = roughly 1AH

So every day the car looses very roughly 1AH.

After two weeks Battery looses very roughly 14AH etc etc.

Now if you start with a poorly charged Battery due to a series of short journeys, you can see how there could be a problem.

[jedi134]

what Amp rating is the Battery?

I personally would not think 45ma is a huge drain.....

[IanXT4]

I would agree 45ma does seems small, but a little over a long period becomes a lot.

Confucius say "a drip will empty a dam"

In the case above you lose approx 30% of a 45ah Battery in two weeks, assuming Battery ageing looses 10% per year and perhaps capacity loss due to other factors (ie undercharging due to short journeys) its not difficult to see a situation where after a few weeks of inactivity you are left with a very poorly charged Battery.

Out of curiosity I have just been reading a Yuasa application document and they mention/warn a few times of problems associated with undercharging caused by short journeys.

The problems I have seen in my car I think are definitely down to a small battery 45ah, short journeys and occasional long periods of inactivity. I suspect/guess the battery gets to half charge or less

At some charge level a battery can no longer provide the current required to turn the starter motor. Out of interest I am trying to find a graph of starter current against residual capacity but have not yet found one ?

[Jamesbelfast]

Your discharge calculations are rough and ready but good enough for what you want but 0.45 amps is too high.

I reckon it should be around the 0.6 to 1 milliamp range.

[IanXT4]

Its 0.045A plus I am not sure you could do a lot with 1 ma

Consider all the alarm circuitry (all distributed so requiring comms and buffering circuitry)

Main alarm CPU

Two flashing LEDs

Internal microwave proximity detector

Glass breakage sensor

Charging circuitry for back up Battery

I think 45ma sounds very reasonable

[jedi134]

1-6 ma would be the drain with nothing connected to the Battery :D you could just about power up 2 tiny LED`s with that current, so 45ma sounds ok to me. What does sound stranger to me is your 45Amp rated Battery, I think you have hit the nail on the head, short runs and constant cranking of the starter motor, with that tiny motor bike Battery..

My rav diesel has a 90amp rated battery, can you not fit a higher AMP rated battery in your petrol? does it not have the same battery space???? I always go for the highest AMP battery that will fit Vs price..........I find there is not much difference in price from the low amp batteries to the higher ones......

I would think if the battery is underpowered it will fail quicker as it has to work closer to its limits. Like and engine running at 6k RPM as opposed to 2K RPM

Just out of interest what make and model is the battery.........does it state a cold cranking Amperage?

[mnl]

If you park on the drive or in the garage, get an optimate or similar and connect it up when you park the car, maybe fit the socket under the dash so the wire crosses the drivers seat and you won't forget to remove it.

I've got a 'bike from 2001 still on the original Battery because it has been connected to an optimate when parked.

(Has likely cost £50,000 in electricity though, a new Battery would only be £60 a year....)

[jedi134]

Or one of those solar 12v types that plug into 12v ciggy socket, £10-£20 from maplins.

Free electric and eco friendly, you may get a rebate on your road tax ;)

[mnl]

They don't work well enough through the windscreen, and they are not waterproof.

I thought they were a good idea too until I tried one.

[Cyker]

Is it the right Battery?

My brother's Corolla had weird problems with cranking the engine and then the Battery went flat so he replaced it and that went flat a few months later.

He went to Toyota after that, and it turned out the standard Toyota Battery for a 2.0 D4D Corolla is some giant thing what looks like it belongs in a truck

He's had no problems since then ;)

[jedi134]

Good point, I would think it should be bigger, maybe someone put in a cheaper one.??