Car Alarm - When Car Battery Low
Discussion
Just a variation on a theme from recent threads on car alarms. When the car's battery is low the alarm siren begins to chirp merrily away and if the car battery dies altogether the alarm thinks the battery has been disconnected and the siren goes off. That's all very well but the battery is then so low that the receiver for the remote (for unlocking doors and disarming alarm) doesn't work. 
Does anyone know a better way around this than manually opening the door... setting off the alarm and connecting a battery charger? The plastic immobiliser tab doesn't work if the car battery is low.
Does anyone know away to get a backup battery supply just for the alarm receiver or set the alarm so that it begins chirping before the battery is so dead you can't deactivate the alarm?
It's all very embarrassing at 6 am in the morning!
MC
Does anyone know a better way around this than manually opening the door... setting off the alarm and connecting a battery charger? The plastic immobiliser tab doesn't work if the car battery is low.
Does anyone know away to get a backup battery supply just for the alarm receiver or set the alarm so that it begins chirping before the battery is so dead you can't deactivate the alarm?
It's all very embarrassing at 6 am in the morning!
MC
Solve the problem further back and get a battery conditioner, eg 'Airflow'. Costs about £45 and plugs into the cigarette lighter socket (which is not switched through the ignition). Leave it on all the time the car is at home garaged. Super gadget!
>> Edited by simpo one on Friday 26th July 20:42
>> Edited by simpo one on Friday 26th July 20:42
quote:Already have one but the battery just died completely anyway (the charger wasn't connected at the time normally goes on once a week) i.e will not accept any charge.
Solve the problem further back and get a battery conditioner, eg 'Airflow'. Costs about £45 and plugs into the cigarette lighter socket (which is not switched through the ignition). Leave it on all the time the car is at home garaged. Super gadget!
I did find out that if you disarm the alarm and then disconnect the battery that this does not set the alarm off. Couldn't for the life of me work out how to remove the battery box. There were no bolts around the box but there were 4 bolts underneath the car.
I ended up having to leave the old battery in place and connect the positive lead to the new battery. I couldn't get the negative strap off the old battery so it's currently (no pun intended!) connected to the new battery using a heavy duty jump lead. At least that way I can lock the car and leave the alarm armed and will be able to get down to the dealer on Saturday.
Also had fun in Halfords as the 072 batteries there are only rated for 590A but was wondering whether the 630A rating for crank capacity in the bible is measured a different way. We searched through Lucas, Bosch and one other manufacturer's catalogues and all 072s were rated at 590A (SAE).
I reset the ECU but is there anything else that needs reseting?
MC
'Already have one but the battery just died completely anyway (the charger wasn't connected at the time normally goes on once a week) i.e will not accept any charge.'
First point is that a *conditioner* is slightly different from a charger - it puts out very low current, ie milliamps, and stops doing so when the battery is happy (so it does not overcharge, fill your car with hydrogen and blow your garage up). It cannot bring a knackered battery back to life, and is not designed with strenuous recharging in mind.
Second point is that even a conditioner cannot keep a battery working for ever, just for longer and more reliably. Eventually the battery will die, especially if it has been discharged too much, and will have to be replaced.
'I did find out that if you disarm the alarm and then disconnect the battery that this does not set the alarm off.'
Diconnecting the battery will stop current drain, but will not keep the battery topped up. If disconnection is your preferred option, suggest you take the car somewhere and get one of those red T-handle isolators fitted somewhere convenient.
'Couldn't for the life of me work out how to remove the battery box. There were no bolts around the box but there were 4 bolts underneath the car.'
Don't know about Chimps, but there must be a way! Either get ye olde Bible or post another thread.
'I ended up having to leave the old battery in place and connect the positive lead to the new battery. I couldn't get the negative strap off the old battery so it's currently (no pun intended!) connected to the new battery using a heavy duty jump lead. At least that way I can lock the car and leave the alarm armed and will be able to get down to the dealer on Saturday.'
Hopefully they will think of a more elegant solution!
'Also had fun in Halfords as the 072 batteries there are only rated for 590A but was wondering whether the 630A rating for crank capacity in the bible is measured a different way. We searched through Lucas, Bosch and one other manufacturer's catalogues and all 072s were rated at 590A (SAE).'
Been there, done that! We found a 620A one I think, slightly different shape to the original, bit lower I think, but nothing a desperate owner and AA man couldn't use!
'I reset the ECU but is there anything else that needs reseting?'
I thought the ECU reset anyway when the battery was disconnected?
Hope this helps!
First point is that a *conditioner* is slightly different from a charger - it puts out very low current, ie milliamps, and stops doing so when the battery is happy (so it does not overcharge, fill your car with hydrogen and blow your garage up). It cannot bring a knackered battery back to life, and is not designed with strenuous recharging in mind.
Second point is that even a conditioner cannot keep a battery working for ever, just for longer and more reliably. Eventually the battery will die, especially if it has been discharged too much, and will have to be replaced.
'I did find out that if you disarm the alarm and then disconnect the battery that this does not set the alarm off.'
Diconnecting the battery will stop current drain, but will not keep the battery topped up. If disconnection is your preferred option, suggest you take the car somewhere and get one of those red T-handle isolators fitted somewhere convenient.
'Couldn't for the life of me work out how to remove the battery box. There were no bolts around the box but there were 4 bolts underneath the car.'
Don't know about Chimps, but there must be a way! Either get ye olde Bible or post another thread.
'I ended up having to leave the old battery in place and connect the positive lead to the new battery. I couldn't get the negative strap off the old battery so it's currently (no pun intended!) connected to the new battery using a heavy duty jump lead. At least that way I can lock the car and leave the alarm armed and will be able to get down to the dealer on Saturday.'
Hopefully they will think of a more elegant solution!
'Also had fun in Halfords as the 072 batteries there are only rated for 590A but was wondering whether the 630A rating for crank capacity in the bible is measured a different way. We searched through Lucas, Bosch and one other manufacturer's catalogues and all 072s were rated at 590A (SAE).'
Been there, done that! We found a 620A one I think, slightly different shape to the original, bit lower I think, but nothing a desperate owner and AA man couldn't use!
'I reset the ECU but is there anything else that needs reseting?'
I thought the ECU reset anyway when the battery was disconnected?
Hope this helps!
Thanks Simpo,
Should have mentioned that I use an 'intelligent charger' so it does act as a conditioner after battery's voltage gets back up near the top. Also normally have a solar charger trickling away when not connected to the IC... but up until Thursday it just hasn't been sunny enough!
On my other car, if you disconnect the car battery the car alarm goes off, but there is a manual override (key operated switch) to prevent this deafening the mechanics. I wasn't sure what would happen when I swapped over the leads to the new battery as I do know that if the battery discharges completely whilst the alarm is activated it also sets the alarm off! I only needed to disconnect the battery to swap the new one over.
I'd looked in the Bible (the battery section is also on Steve's Website) and also I spoke to the dealer. On my car (98 Chim) the battery box sounds fairly similar to the Griffith's with 4 bolts accessed from beneath the car. They're going to have the joy of swapping it over in any case as there's a risk of messing up the fibreglass.
I understood that if you disconnect the battery the ECU resets to defaults. By running the engine without touching the accelerator, the ECU reprogrammes and then the fans come on briefly (at much lower temp than normal).
MC
Should have mentioned that I use an 'intelligent charger' so it does act as a conditioner after battery's voltage gets back up near the top. Also normally have a solar charger trickling away when not connected to the IC... but up until Thursday it just hasn't been sunny enough!
On my other car, if you disconnect the car battery the car alarm goes off, but there is a manual override (key operated switch) to prevent this deafening the mechanics. I wasn't sure what would happen when I swapped over the leads to the new battery as I do know that if the battery discharges completely whilst the alarm is activated it also sets the alarm off! I only needed to disconnect the battery to swap the new one over.
I'd looked in the Bible (the battery section is also on Steve's Website) and also I spoke to the dealer. On my car (98 Chim) the battery box sounds fairly similar to the Griffith's with 4 bolts accessed from beneath the car. They're going to have the joy of swapping it over in any case as there's a risk of messing up the fibreglass.
I understood that if you disconnect the battery the ECU resets to defaults. By running the engine without touching the accelerator, the ECU reprogrammes and then the fans come on briefly (at much lower temp than normal).
MC
'Should have mentioned that I use an 'intelligent charger' so it does act as a conditioner after battery's voltage gets back up near the top. Also normally have a solar charger trickling away when not connected to the IC... but up until Thursday it just hasn't been sunny enough!'
But you said you only connected it once a week? Whatever, if the battery's expired, that's that!
'I wasn't sure what would happen when I swapped over the leads to the new battery as I do know that if the battery discharges completely whilst the alarm is activated it also sets the alarm off!'
You could bridge it by attaching the new battery before removing the old one, hence there is always some current in the system. That's the AA did with my BMW - there was a warning that the ECU would go funny if power was removed completely, so he bridged it with his special big yellow battery whilst changing the proper one.
'On my car (98 Chim) the battery box sounds fairly similar to the Griffith's with 4 bolts accessed from beneath the car.'
The Griff is two bolts. Undo them, then crawl into the passenger footwell, pull up the carpet, take the ECU and assorted spaghetti off the top (or can be at side), pull the battery box forward and disconnect. If you're really unlucky - eg if the battery is the original one - the top will have a GRP panel which has to be removed to.. It's fairly easy to put it all back, apart from the bolts - which I left for someone else to do at MOT time. I don't mind driving about with the box unbolted - it's a tight fit and can't go forwards if I hit something, but water could get up through the bolt holes.
'They're going to have the joy of swapping it over in any case as there's a risk of messing up the fibreglass.'
Good philosophy - 'if in doubt leave it'!
But you said you only connected it once a week? Whatever, if the battery's expired, that's that!
'I wasn't sure what would happen when I swapped over the leads to the new battery as I do know that if the battery discharges completely whilst the alarm is activated it also sets the alarm off!'
You could bridge it by attaching the new battery before removing the old one, hence there is always some current in the system. That's the AA did with my BMW - there was a warning that the ECU would go funny if power was removed completely, so he bridged it with his special big yellow battery whilst changing the proper one.
'On my car (98 Chim) the battery box sounds fairly similar to the Griffith's with 4 bolts accessed from beneath the car.'
The Griff is two bolts. Undo them, then crawl into the passenger footwell, pull up the carpet, take the ECU and assorted spaghetti off the top (or can be at side), pull the battery box forward and disconnect. If you're really unlucky - eg if the battery is the original one - the top will have a GRP panel which has to be removed to.. It's fairly easy to put it all back, apart from the bolts - which I left for someone else to do at MOT time. I don't mind driving about with the box unbolted - it's a tight fit and can't go forwards if I hit something, but water could get up through the bolt holes.
'They're going to have the joy of swapping it over in any case as there's a risk of messing up the fibreglass.'
Good philosophy - 'if in doubt leave it'!
quote:
I understood that if you disconnect the battery the ECU resets to defaults. By running the engine without touching the accelerator, the ECU reprogrammes and then the fans come on briefly (at much lower temp than normal).
1. The fans are not connected to the ECU and are totally independent so if they come on early its because the sensor has tripped early. Purely temperature related and nothing else.
2. The adaptive learning starts at around 90 degrees ish and is a continious process. Just drive the car. It is not going to magically reprogramme itself by letting the car idle on the drive.
Just get in the car and enjoy it. No special treatment is needed.
Steve
quote:So I guess all you can do is what I did and open the car and connect a power source, whether a second battery or charger/conditioner. All I know is that the charge from a solar panel was not enough to allow doors to be unlocked/alarm to deactivate via the remote... and that provides about 50 mA @ 12V.
if the car battery dies altogether the alarm thinks the battery has been disconnected and the siren goes off.... but the battery is then so low that the receiver for the remote (for unlocking doors and disarming alarm) doesn't work.
Does anyone know a better way around this than manually opening the door... setting off the alarm and connecting a battery charger?
The plastic immobiliser tab doesn't work if the car battery is low.
MC
You could either connect a full-blown proper battery charger for a day (or whatever the instructions say) and see if that does the trick. I suspect your battery will not the hold the charge for very long. If it doesn't, then fit a nice shiny new battery, plug in a conditioner (or solar charger, as they are both very low output) and live happily ever after!
In short, I think amputation is the answer (no pun intended!)
In short, I think amputation is the answer (no pun intended!)
I've had this trouble with mine. When the battery is completely flat the "intelligent" charger assumes its dead. If you jump the car off from another, and run it for 10 mins or so, it should get enough charge in for the "intelligent" charger to start doing its thang.
If the battery has been flat for any length of time it may well be beyond hope, but I have had this happen a couple of times and so far have gotten away with it - the battery still works.
Worth a try before you bin the battery.
If the battery has been flat for any length of time it may well be beyond hope, but I have had this happen a couple of times and so far have gotten away with it - the battery still works.
Worth a try before you bin the battery.
If you've got a 'proper' charger you may as well use it. 'Conditioners' are not designed to recharge really flat batteries - mine has four red LEDS and two green ones. If it's down to the last red one the instructions say it won't be able to charge the battery. I see conditioners as a way to keep an essentially heathly battery in tip top condition, not to keep dying ones half-alive for a few days!
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