New Battery and car won't start

[JumpingJack]

Just purchased a 2007 m35x and the batter died. Put in a new battery and now the car won't start. I'm able to operate the door locks with the fob but when i try to start the car the dash lights come on but the motor won't turn over. Also noticed that when i depress the start button the lights begin to go dim. I let it sit overnight and the battery was completely dead. I found where some people have implicated the ecm relay in the ipdm but i tested it and it's fine. I've never seen something like this. Has anyone got suggestions?

[Ilya]

Hmm that's an interesting one. Try this...put the key fob on top of the start button as you start the car. Basically, push the start button with the fob.

[steve_c]

I am assuming you are correct in your diagnosis that the battery is draining, even though you did not say you checked it, as opposed to a faulty ground, etc.
If so, that is a large parasitic draw, something is drawing that battery down very quickly & consuming amps!
On a cold car, (left unstarted overnight) on a fully charged battery, I would think whatever is drawing down the battery as quickly as you say would be warm to the touch, whether it be the alternator, stuck relay, electronic module or component etc.
In my opinion, you are not losing milliamps here, you may be drawing over an amp or better by your description of a new battery going dead overnight. If this is the case, the component with the draw should be warmer than the surrounding temps.
If it were my car, I would check to see what is warm while the battery is charged, and the car is off (and has been off several hours so that everything is at ambient temps). One of those infrared laser heat guns work great for this. (Harbor Freight sells cheapo units).

[JumpingJack]

Thanks for the reply. It's always possible that the new battery is bad. I agree that to drain the battery so quickly is unusual. I charged the battery last night so can do some more diagnostics when i get home. The is the strangest thing....

[steve_c]

.... It's always possible that the new battery is bad.....

Absolutely!
When I shop for a new battery, I only purchase from the rack, where I can select the battery I want.
I check for 2 things before selecting the actual battery I purchase.
First, the date code (manufacture date code). Shelf life of a new battery is critical, as sulfation starts while battery is sitting on the rack!
I have seen batteries on the rack at retail outlets that were over a year old, sitting below 12.5 base voltage!
At a good retail store with moderate battery turnover, I see 2 to 3 months average on date codes.

I then check the battery voltage using a pocket voltmeter. I select the highest voltage battery on the rack. Nominal base voltage should be 12.5 volts. On a fresh new battery, it will always be 13.xx (base voltage + residual). The longer the battery sits, the lower to the 12.5 base voltage it will eventually trickle go down to. It will drop lower than 12.5 volts if a cell is weak, or sulfation is beginning to set in!

Before installing a new battery, I give it a trickle charge, usually six hours minimum, and under an amp. It is not necessary, but I do it to keep the residual battery voltage up since the first thing the battery will experience is a discharge cycle (starting).