The battery of my 2013 TDI can become very low overnight that I cannot start the car.
I changed the battery less than 3 years ago. I bought the battery from the dealer.
1. the car is used not much. My wife drives it but not long distance every day. Is it possible that the battery is not charged enough? and sometime it discharged too deep?
2. after I changed the battery, I found some one to program the car. If the programming is wrong, can it cause the problem?
3. Can there be battery drain?

what should I check?

I am thinking to send the car to the dealer for a new battery.

thanks.

 

1. Yes, this can absolutely occur. The TDI engine uses a lot of power to start, and it requires a fair bit of driving to recover that charge. I would estimate that if you drive less than twenty minutes before shutting the vehicle off, you are slowly draining it.
2. If the battery energy management coding was not done correctly, it will cause problems. Ultimately, you need the car to reset its memory to a new battery with the correct amperage capacity. Alternatively, you can unplug the BEM cable on the battery terminal, and this just results in "dumb" charging it, like vehicles did for the prior one hundred years.
3. Yes, there might be a battery drain. Common issues are one or more of the touch-sensitive door handles.

If #1, put it on a trickle charger during periods of non-use or once a week over night. This should make up for the short drives. However, it won't do anything for you diesel particulate filter, which needs a good long drive every so often to successfully complete a regeneration cycle!
If #2, well, I doubt it is this. If it was, the battery would probably already be toast. Non-coding will generally kill a new battery within a year or two, tops.
If #3, the trickle charger will help for a little while. But, the constant heavy drain on the battery (and it *is* a fairly heavy drain) will kill it sooner than later (such that it will not properly hold charge).

I'd start with adding a trickle charger, then use a multi-meter to check for a parasitic drain while the system is off. If the amperage is acceptable, then it is likely #1.

 

Thanks for the reply.
I am using a trickle charger which can charge AGM battery. It can help, but the issue repeats. I can be wrong but I believe the battery is toasted.

But for checking parasitic drain, I have no idea how to check amperage because the battery is under the seat, besides, a multimeter has limited amp range. Can you elaborate on this? Do you use the special Amperage meter?
Even I have the battery changed, the new battery will be damaged soon if the parasitic drain persists. So I need to check this.

thank you again.

 

First thought is how many amps is your trickle charger kicking out? It needs to be at least a 3amp or higher trickle charge rate for this car...lower than that isn't gonna do you much good with battery installed in the car, as relates to resistive losses in cables, parasitic losses constant, etc., etc. This car has a heavy electrical load with so many accessory items, pumps, after-run pumps, etc., so leaving the key on/engine off and door(s) open is a good way to drain the battery down. TDI's need to be driven longer/faster drives regularly to keep the DPF /emissions systems from clogging/failing, and you can easily check status of DPF regens via a decent VAGCOM type scan tool...that just means it can read VW Auto Group diagnostics coding.

You will have the common parasitic battery drains from the 'Audi Smart Key' door handles, if your car is so equipped, as they have proximity sensors embedded in them and also the cute little thumb pushbutton to lock car as convenience on handle exterior.

There are dedicated fault codes for the proximity sensor failure and also for the push-button failure (grounding out) on each smart-key door handle. You need to get a basic VAGCOM scan tool to read internal fault codes stored, if you don't plan to DIY, but just want to know what's going on with the car. Those start around $50 USD for VAGCOM type scan tool. If you want to actually DIY any repairs and services on this car, or get help diagnosing issues, then you should get a Ross-Tech VCDS (VAGCOM) that provides you the full coding/diagnostics access to this car, etc. Otherwise you are just guessing or operating with sub-par, limited information, which gets really frustrating and expensive with this car.

If you got 3yrs on the OE battery, with an older Q7, then it really sounds like your issue is primarily the shorter drive cycles combined with sitting in the car engine off/radio on or phone call going, etc., or doing same in driveway/garage while cleaning the car...so much electrical on this car is awake when key is ON position/doors open, etc. Get a scan tool.

Take it to Audi they'll charge you same or more than what you'll spend buying a good scan tool (Ross-Tech VCDS) just to hookup their own scan on your car once, so that's really not a smart move...these are very common issues. The OE battery is very good quality. Make sure your charger is up to the task; minimum 3amps trickle output, and it's better if you have one that is automatic and/or switchable to charge at higher amperage rates...5, 10, 15amps, etc, as this is a large, high capacity/high reserve type battery.