My miata battery drains all th time

Losing power while just sitting for long times is normal for wet cell batteries. However, for a short period like that, sounds like there is a constant drain on the battery when you think it is not in use (something connected to the battery). When you are not using the battery, either disconnect the battery, trace the source of the drain and turn it off, or buy a trickle charger and attach it to the battery and plug it in. You should also do a battery load test to see if the battery is properly holding a charge.

You have a parasitic drain on the electrical system , something is staying on . Maybe a module isn't powering down . There are videos on youtube How to Perform Parasitic Draw Test on Your Vehicle Diagnosing Battery...

Connected ? Could be a light or fault on alternator draining.if it loses charge disconnected battery is finished

You have a parasitic draw. Something is drawing power while the truck is sitting. Do you have any aftermarket items hooked to direct power? Something you leave plugged in to the 12V plug (cig lighter) Some 12v plugs are full time power and some are only powered with ignition on. Any amps wired direct power? If you have no aftermarket accessories drawing constant power you then need to determine what circuit has the draw. An amp clamp on the battery cable will show draw, then re & re 1 fuse at a time until you find the one that eliminates the draw. Once you've done that you need to find the problem on that circuit. All this is assuming your charging system is working and the battery is being properly charged while you're driving the truck.

You can check with a 12v test light or an amp meter. If you take off one of the battery terminal ends, (preferably the negative) and run the test light or amp meter in series from the battery post to the cable end, see if it lights up.


If it does, then you will want to start pulling fuses one by one until it goes out. When it goes out, then that is the circuit that is causing the draw. If not, then the battery is bad, as it can't hold a charge.

The recommendation for maximum parasitic drain is around 30 mA (0.030 amp). A typical drain today actually falls into the 7-12 mA range, even though some vehicles do approach the maximum. Multiply the drain (in amps) by the time (in hours) the battery sits without being recharged. The result is the amount of AH consumed by the parasitic drain. The actual drain may be small, but over time the battery grows steadily weaker.

Just remember to keep all of the doors closed when you do this and disconnect the hood light if there is one, thanks

You have what is called a parasitic draw on the electrical system , battery . Could be a control module not powering down when it's should . a electrical componet is staying on . , light in glove box , something you can't see . Bad diode in the alternator could cause this . But this just gussing , testing is the way to a fix . Watch thesed videos on testing for a draw on the system . Improved Methods to Find Parasitic Draw Battery Drains Overnight

The Trainer 27 3 Ways Of Finding The Cause Of Key Off Battery Drain...

Batteries will lose power if they sit for long periods of time. It is a good idea to start the vehicle once in awhile to restore the charge to the battery. Batteries will lose their charge and it is not a good idea to let them sit for a long period of time, especially in the winter months. If your battery is older, it may not be holding a charge as good as a new one would.

Only way to completely empty tank is to remove it. there is about a two gallon space between the pump and tank bottom where condensation can build up. You can partially drain it by disconnecting the fuel line and turning the key on. The pump will empty tank (don't run the pump after fuel is mostly empty or it will burn out) Also make sure that hose is secure so that fuel dosen't end up on the ground. After you have finished, put the battery on a charger and bring it back to best charge...Alternator will not and cannot do that.

Check you Key FOB for a low battery.

you have a battery power drain.  Remove one fuse at a time until you find which circuit it's in.  This will take a while but it will find the problem and it's free.