How long to drain the battery?
Discussion
So I normally leave the car on trickle charge in the garage. Let's say for arguments sake I forget to turn the charger on and don't use the car for a bit, having just been for a 200 mile run. How long should I expect to be able to leave a healthy car before the battery is too flat to start it? Roughly.
Standard 400 with the factory alarm immobilser. And no, I didn't - I mean let's assume I didn't - leave the lights or anything on that should be turned off.
Standard 400 with the factory alarm immobilser. And no, I didn't - I mean let's assume I didn't - leave the lights or anything on that should be turned off.
I'd back that up. Assuming the car has just had a long run, it should last a fortnight at least.
If not, I'd suspect a faulty battery or excessive drain somewhere.
There are users on here with isolation switches that turn everything off including the immobiliser and they last a month or more. They stay on shelves for years with full charge.
If not, I'd suspect a faulty battery or excessive drain somewhere.
There are users on here with isolation switches that turn everything off including the immobiliser and they last a month or more. They stay on shelves for years with full charge.
scushing said:
Thanks folks. Sounds like I do have an issue. It was less than 4 days from fully topped up to flat as a pancake.
You need to be 100% certain your battery is in perfect health before moving to testing for a parasitic drain, this is extremely important as a weakened battery will never hold a charge as effectively as it should even if there are no parasitic drains present at all, you could easily spend hours looking for an issue only to later discover your existing battery is on the way out. If your battery has already suffered a number of deep discharges it will likely be damaged and should be replaced before you begin the process of chasing down the reason it was being discharged in the first place.Unlike leisure batteries that will cope quite happily with multiple discharges, car batteries are designed for cranking and will only give you two or maybe three deep discharge and recharge cycles before they become irreversibly damaged. Never jump start the car when the battery is fully discharged, the alternator will just dump as many amps as it can in the battery as quickly as it can, this is not only very hard on the alternator itself but it will also invariably be the end of your battery, always recover a discharged battery as slowly as possible using a proper modern charger with a good recovery algorithm that will slowly and gently ramp the amps and should also offer a recovery pulse mode to gently lift the sulfation build-up from the battery plates.
Once you've satisfied yourself your current battery is in perfect health (or more likely you have fitted a new battery) you can now start testing for a parasitic drain.
These cars are extremely susceptible to parasitic drains, the security system and more specifically the way it's wired is a common source of such issues. Door pin courtesy light switches are a good place to start your investigations, make sure the little buttons on the doors that are there to press on the on the switches are actually making reliable contact and pushing those pin switches fully in. Even if the switches themselves and the pusher buttons check out Ok the circuit they are connected to is linked to the security system which is poorly wired and the Meta system itself isn't the most reliable either.
Not only is the door pin switch circuit responsible for telling the alarm unit the doors are open or closed it also activates the courtesy light, this part of the circuit has a remote delay relay in it which is actually triggered by the lock/unlock signal from the Meta unit. When you unlock the car the courtesy light comes on before you've even opened the door, when you've arrived at your destination and open the door to leave the car the courtesy light will be activated, you then lock the car the and delay relay is activated again by the Meta unit, the light stays on for a set number of seconds until the delay relay switches off but it's quite common for current to still be present on the delay relay coil or the relay buried inside the alarm unit even though the courtesy light itself has gone out. All this is hard to test as obviously the doors will be shut and locked so the components you need to test with your meter will be inaccessible, I recommend disconnecting your door switches completely and seeing if your four days suddenly becomes the 2-3 weeks before the battery goes flat that you should be enjoying.
My Experience:
I found on my car there was a constant excessive parasitic drain at the alarm unit even with the doors shut and the car locked, the delay relay itself checked out fine but there's another relay buried inside the Meta unit that remained energised. A 25 - 60 milliamp draw is acceptable but anything that exceeds 100 milliamps indicates an electrical issue that needs to be addressed, my Meta unit was pulling a constant 2-3 amps with the doors shut and the car locked even though the door pin switches were working correctly. Clearly there was a sticking relay inside the Meta unit which seemed to be a constant, completely disconnecting the perfectly functioning door switches solved the issue as this circuit is looped through the Meta unit circuit where the true fault resides.
Even though the switches and their activation were themselves functioning perfectly disconnecting the switches solved the problem, as soon as I disconnected both switches the parasitic drain at the Meta unit disappeared. Solving the issue permanently demands I replace the Meta unit itself, as the fault resides inside it and it's internal relays are potted within means replacement of the whole unit is the only way to correctly fix the problem. However for the time being I've simply left the door switches disconnected which while eliminating the drain does mean my courtesy light only comes on if I switch it on myself at the light itself, no big deal really but the proper solution is to have the whole system replaced by David at HF Solutions who fortunately lives locally to me.
This was just my experience and may well not be your problem, it's essential before you start testing for a parasitic drain you satisfy yourself your battery is in perfect condition, indeed if you've suffered a few full discharges already you may well be best off just biting the bullet and buying a brand new battery before moving forward to the diagnostic stage. Be systematic and don't make assumptions based on my experience as your situation may well be completely different.
Good luck with it and if you're unsure how to test for a parasitic drain there are many excellent step by step guides available online like this one....
http://www.wikihow.com/Find-a-Parasitic-Battery-Dr...
A clamp meter can also be an extremely helpful tool when checking for parasitic drains as it allows you to see how many amps a wire is carrying without the need to disconnect it
Maplins sell a very useful tool for narrowing the search for parasitic drain. It's essentially an ammeter with a connector that replaces a standard fuse in the fuse box. Just plug this into each fuse position and see what the drain is in each fuse circuit. Helps narrow down where to look.
Plan B said:
Maplins sell a very useful tool for narrowing the search for parasitic drain. It's essentially an ammeter with a connector that replaces a standard fuse in the fuse box. Just plug this into each fuse position and see what the drain is in each fuse circuit. Helps narrow down where to look.
I'll have a look for that in Maplins then as 4 or 5 days without trickle in mine and its also dead. Its not the battery and the alarm has been sorted by Carl so I'm thinking that is probably ok but its definately somewhere and that might help me track it down.I did this awhile ago when my battery was probably about 8-10 months old. Forgot to flick the switch on at the mains and when going to start 8 days later it was flat. The alarm wasn't set on the car as the garage is alarmed but like you thought it would of held longer than a week on a relatively new battery so you're not alone.
Since then the longest I've left it unplugged is 4 days and it fired up no problem(So it should) ,but I now tend to leave the mains switch active all the time so it doesn't happen again.
Since then the longest I've left it unplugged is 4 days and it fired up no problem(So it should) ,but I now tend to leave the mains switch active all the time so it doesn't happen again.
Prior to locating the source of my parasitic drain I solved (read masked) the problem of a frequently discharged battery by using a Battery Brain remote battery disconnect device.
This worked brilliantly when I had my car in a council lockup where there was no mains power, although I now have a garage with mains and my battery is kept on a float charge I still use the Battery Brain as it ensures complete safety when the car is not being uses.
With no power to the iffy quality TVR electrics there can be no electrical fire, I also use the Battery Brain if I'm leaving the car overnight in an area where security may be in question as it acts as a great second line of defense against theft.
While tracing an resolving a parasitic drain is always the best option, the Battery Brain is an excellent bit of kit with a number of uses and advantages. If left on and in monitor mode the Battery Brain also constantly checks the battery voltage and automatically cuts it off if power falls below a certain lower threshold, this means you can always start the car even if say you've left your lights on.
Chasing down and fixing the drain itself should be your priority but the Battery Brain is certainly a great addition too. Buy the one with two IR remote fobs as this means you can dead lock the car and then remotely disconnect the battery from outside and up to 10 meters from the car, when you return to the car just press the fob to reconnect the battery and then unlock the car as normal.
https://www.batterybrain.co.uk/product/battery-bra...
It's £90 but worth every penny in my opinion
This worked brilliantly when I had my car in a council lockup where there was no mains power, although I now have a garage with mains and my battery is kept on a float charge I still use the Battery Brain as it ensures complete safety when the car is not being uses.
With no power to the iffy quality TVR electrics there can be no electrical fire, I also use the Battery Brain if I'm leaving the car overnight in an area where security may be in question as it acts as a great second line of defense against theft.
While tracing an resolving a parasitic drain is always the best option, the Battery Brain is an excellent bit of kit with a number of uses and advantages. If left on and in monitor mode the Battery Brain also constantly checks the battery voltage and automatically cuts it off if power falls below a certain lower threshold, this means you can always start the car even if say you've left your lights on.
Chasing down and fixing the drain itself should be your priority but the Battery Brain is certainly a great addition too. Buy the one with two IR remote fobs as this means you can dead lock the car and then remotely disconnect the battery from outside and up to 10 meters from the car, when you return to the car just press the fob to reconnect the battery and then unlock the car as normal.
https://www.batterybrain.co.uk/product/battery-bra...
It's £90 but worth every penny in my opinion
PhilH42 said:
Plan B said:
Maplins sell a very useful tool for narrowing the search for parasitic drain. It's essentially an ammeter with a connector that replaces a standard fuse in the fuse box. Just plug this into each fuse position and see what the drain is in each fuse circuit. Helps narrow down where to look.
I'll have a look for that in Maplins then as 4 or 5 days without trickle in mine and its also dead. Its not the battery and the alarm has been sorted by Carl so I'm thinking that is probably ok but its definately somewhere and that might help me track it down.Gassing Station | Chimaera | Top of Page | What's New | My Stuff