Srs lights drain battery when engine is off in a 2008 c70. How to keep battery from getting drained?

Should be the alarm/immobilizer indicator.

How to Stop Car Battery Drains

How to Find Car Battery Drain
How to Test and Find Parasitic Battery Drain Key Off
How To Perform Parasitic Draw Test EricTheCarGuy

is the alternator charging. if it is then. I am guessing a light is coming on after you walk away. my truck did that. 2 hours later the lights would come on

sounds like the radio it's the problem. to make sure it is, you have to do what mechanics call a parasite circuit test, simply buy a test light at your local auto parts store, open the engine hood and look for the battery disconnect the negative cable and connect the test light in series with the battery and negative cable, the test light will stay on indicating that in fact there is a parasite circuit drain, find the fuse box your car comes with a owner's manual this manual it's helpful to find the fuses in the car, now that you find the fuses take out one fuse at the time until the test light goes off, (important put the fuse back before moving to the next one) when the test light goes off by removing the fuse, that is the circuit that it's draining the battery, check the fuse number whit your owner's manual to see if the radio in fact it's part of the fuse circuit. if not then you have a drain somewhere else in that circuit, (important the car doors must be close while doing this test or the interior light will stay on causing a normal drain keeping the test light on. and if the test light does not come on when connecting it in series don't panic this means the drain it's too small and then you have to do the same test but this time using an amp meter which it's more expensive and more complicate than the test light.

First step have the battery tested, a bad cell can cause a internal drain and kill the battery, if the batt is ok then check for interior lights like visors that stay on or interior light that come on by themselves at night due to defective door switches.

The unfortunate thing is diagnostics DOES TAKE TIME. You need to set aside the time to be accurate.

Something for sure is draining the battery and methodical diagnosis is the only way to get it figured out. IF there were an open in the alternator to battery circuit, the new alternator would be damaged.

Pull the interior light and radio fuses, disconnect the negative battery and put a test light or volt meter in series with the cable and battery terminal. I expect the light will be lit or the voltage to be above .2 volts draw.... Disconnect the battery, remove one component, connect the battery test setup, and see if voltage drops or light goes out..... when it does, you have the offending system, so investigate that.

Be sure that you can garantee good ground between battery and everything....especially the engine.

You my friend have a bundle of problems. See if I can address them for you.
#1) Airbag light (SRS) needs to be reset by dealer or a competent shop - it's a special (and expensive reset tool) it's a safety thing. Keep in mind, if light comes back on, one of the crash sensors is loose, corroded or shorted and needs replacing. #2) Engine light - one of your cars many sensors have triggered computer as to a fault. You need to go to a good part store or shop and have them do an OBII fault scan (different from above) Autozone, Advance etc auto parts stores do these FREE. They'll tell you what needs to be replaced, thenthey can reset your light. #3) Your leak can be anything from door seal, window seal, and if you have a sunroof there's a drain near drivers side. I'd have a good shop look at it.

INTERMITTENT BATTERY DRAINS ARE HARD TO FIND. TURN OFF ALL SWITCHES IN THE VEHICLE. MAKE SURE THE GLOVE COMPARTMENT LITE IS GOING OUT. OPEN THE HOOD. CLOSE ALL THE DOORS. MAKE SURE ALL OF THE COURTESY LITES ARE GOING OFF. DISABLE ANY UNDER THE HOOD LIGHTS. REMOVE THE NEGATIVE BATTERY CABLE. USE A 12 VOLT TEST LIGHT, FASTEN ONE END TO A GOOD GROUND, { METAL PART OF THE MOTOR} . FASTEN THE OTHER END TO THE NEGATIVE TERMINAL OF THE BATTERY. IF THE TEST LIGHT LIGHTS UP THERE IS A BATTERY DRAIN. IF NO LIGHT , NO DRAIN. IF THE LIGHT IS ON LOOK IN THE FUSE/RELAY BOX NEAR THE BATTERY. PULLOUT THE FUSES, LARGE & SMALL ONE AT A TIME, IF THE LIGHT STAYS ON PUT THE FUSE BACK IN TRY THE NEXT FUSE. WHEN THE LIGHT GOES OUT, THAT IS THE CIRCUIT CAUSING THE DRAIN. IF IT NEVER GOES OUT, DISCONNECT THE ALTERNATOR. IF THAT MAKES THE LIGHT GO OUT, THERE IS SOMETHING WRONG WITH THE ALTERNATOR. IF THE LIGHT IS NEVER ON, YOU MAY HAVE TO DO THIS ANOTHER DAY TO FIND THE DRAIN. ALSO HAVE THE NEW BATTERY RECHECKED.

Use a 12volt test light between the positive battery post and the positive cable with the positive cable disconnected from the battery.
Keep key off.
You will see the test light "light" with any drain.

Any drain showing a dim test light is..... OK
Any drain showing a bright light is.....BAD

Disconnect items (fuses) one at a time and watch the light.
Keep the doors closed....the inside dome light is a drain with the door open!
After fuses are checked....disconnect the alt if needed and watch the light.
Keep going until you get rid of the bright light.

Check all doors for a sticking door open sense switch. Check all over-riding interior light activation switches are off. If all the above are ok, check for a sticking interior light relay.