Shared Knowledge

"BMW X5 - How to Install a PriorityStart"

4 March 2010

Updated 20 March 2010

Updated 21 June 2011


Summary: Because of limited cargo area space, not an easy install but certainly do-it-yourself (DIY) if you have done any sort of auto mechanics\electrical at all. And do yourself a favor and replace your battery at the same time.



PriorityStart Pro




BMW X5, 4.4liter, model year 2000.

140,000 miles.

Premium sound system; self installed CD changer; power, heated, seats and auto level headlights.


Reason for PriorityStart Install:

Something slowly drains the battery down to the point that car will suddenly not start, but once battery fully charge, ok for a week, 2 or 3.

Not the: battery; alternator or final stage resistor as all new.

And not the connections to the rear upper hatch switch as self replaced (plenty of corrosion in connector there at replacement.)


Tools, Supplies, Needed:

- PriorityStart Pro. Do not buy used. $80-90

- 2 gauge, 20inches or longer, insulated battery cable. $15

- 12inches or more of black wire and either wire connectors or soldering iron and heat shrink tubing.

- Electric tape.

- (1) flat washer with hole diameter large enough to fit over PriorityStart battery terminal bolt.

- (8 - 12 inch long) cable ties (10?)

- Not sure now: 11, 13, 15, 17mm sockets and ratchet.

- Not sure now: 11, 13, 17mm open end wrenches.

Install PriorityStart Pro into BMW X5.


How to install PriorityStart in X5:

1. Go to local auto parts store and buy 20" or longer, 2 gauge, insulated, battery cable. Cable supplied with PriorityStart is not long enough for X5 installation. And battery cable supplied with PriorityStart is only 4 gauge, if that, and X5 battery cables are 2 gauge.

2. Remove red cable from stock PriorityStart. Remove rubber covers from removed PriorityStart cable and place them on new, 2 gauge battery cable. Tight fit over 2 gauge but be patient and they will go.

3. Place 2 gauge cable flat over PriorityStart "battery" lug with cable pointing downward, which is opposite from how PriorityStart had 4 gauge cable. As 2 gauge cable has a large diameter hole than 4 gauge provided with Prioritystart, holding cable flush to PriorityStart battery terminal lug face, slip on a new flat washer, then the lock washer and finally the nut. Do not tighten the nut yet.

4. Tighten down large lug on top of PriorityStart. Would have thought this lug would be tight from factory, but was not.

5. Take PriorityStart black ground wire, cut it and splice in another 12 inches of black wire. Ground wire supplied with PriorityStart is too short for X5 installation. Can use wire connectors at splices if you wish. I soldered and used heat shrink tubing to cover junctions.

6. Fold down rear seats.

7. Remove rear cargo area floor.

8. Remove spare tire.

9. Unbolt orb or dome that is under spare tire and lean it towards front of car. Requires removing 3 nuts and 2 bolts.

Install PriorityStart Pro into BMW X5.

10. Remove red X5 cable from positive battery terminal.

11. Remove black X5 cable from battery negative terminal.

12. If you have a battery charger, connect charger to battery and charge it 100%.

13. Cut or otherwise get open, cable tie downs, freeing large red X5 cable.

14. Take freed large red X5 cable and route it along bottom of driver's side chassis.

15. Move X5 positive battery cable bundle (I have 2 red and one black cable in bundle) around until all wires are as tight together for as long as possible and then wrap all with electrical tape. This will help keep wires together and out of the way of the spare tire and also to help with any potential fraying with cable along chassis.

16. Take cable ties and place over where electric tape begins and ends on X5 power cable. This will hold electrical tape in place.

Install PriorityStart Pro into BMW X5.

17. Take PriorityStart and place into X5 in lower left corner. Want to install it as far away from spare tire edge as possible but need to use 3 holes in chassis for cable straps, so position according.

18. Once you are pretty sure where to mount Priority start, up/down, left/right, holding the large, 2 gauge battery cable in the correct orientation to allow routing to the positive terminal of the battery, tight the nut on the PriorityStart battery terminal lug.

19. Connect the black, ground wire, of the PriorityStart to the PriorityStart and route it along the back of the cargo area chassis. Make sure it is long enough to reach the negative post of the battery.

20. Holding the PriorityStart in its required, desired, location on the cargo area back chassis wall, route the end of one cable tie through the 2 chassis holes closest to the passenger's side and then around the PriorityStart and tighten down strap.

21. Using another cable strap, use the 2 holes closest to the driver's side to wrap around the PriorityStart and tighten the strap down. The PriorityStart should now be fairly snug against the back wall of the cargo area chassis.

22. Take the flat connector supplied with the PriorityStart and place it under the X5 ground cable nut and then place X5 ground cable on battery negative post and tight nut. Note here that the orientation of the flat PriorityStart connector is a function of how long your black PriorityStart cable is. The X5 ground cable should be tight on the battery negative post but be careful tightening the nut as it is possible to twist the nut off and then you have a problem finding a replacement.

23. Route the 2 gauge PriorityStart cable down along chassis and into battery compartment. Because of size of 2 gauge cable battery connector, and because I wanted the connector to sit as flat as possible into the battery compartment and away from the metal orb that goes over it, I had to orient the connector just so. Here an open ended wrench is required and perhaps even vice grips. As shown below, I routed the 2 gauge cable down into the X5 battery compartment so that the orb above could not possibly touch or potentially fray it. NOTE: When you touch the PriorityStart battery cable to the positive battery terminal, you will hear noise inside the PriorityStart as it has some sort of gearing. Also note that the green LED on the PriorityStart should be glowing.

Install PriorityStart Pro into BMW X5.

24. With PriorityStart installed and wired to battery, must now connect X5 red cable bundle to top lug of PriorityStart. Easy? Right? Well I found that although the X5 red cable bundle connector fits over the large PriorityStart lug on the top of the PriorityStart, no matter how much I tightened the nut on the Red connector, I could not get the X5 cable tight and I wanted and you want it tight. Note: when you place the X5 red connector over the PriorityStart top lug, you may see some sparks. This is normal as you have the rear hatch open and current is being drawn to power interior lights.


Install PriorityStart Pro into BMW X5.

25. If your X5 red cable is tight on the PriorityStart top lug, no problem but if it turns at all on the lug, and you have tightened the X5 cable nut as much as you dare, go to an auto parts dealer and buy "battery terminal shims". Because of the large nut at the bottom of the PriorityStart top lug, my battery shim would not fit down all the way on the lug, so I had to cut off some of the shim. It was easy to cut with a pair of scissors. No place shim over PriorityStart lug and then place X5 red cable over shim and lug and tighten X5 connector nut.

Install PriorityStart Pro in BMW X5.


26. Check everything over: all connections tight; no chance of positive battery voltage touching chassis; cables tied to chassis to keep from moving and PriorityStart securely mounted to back wall of cargo area?

27. Remount orb or dome over battery compartment. The metal framework of the orb should not be pinched or otherwise touch any cable. If you look, there are "cut outs" on the back frame for the routing of the black X5 ground cable.

28. If all looks good, start car. If car is in garage, move car out slowly into an open area and let it run for 5 minutes or more.

29. Turn car off and let it sit. Take a break for a few and put away some of your tools.

30. Start car again. Should start right up without there seeming to be any sort of weak battery.

31. Place spare back in car. Once in proper location, check clearance between tire and PriorityStart. Will not be a lot of clearance but tire should go into and out of the car without undue consideration to the PriorityStart. Secure spare tire.

Install PriorityStart Pro in BMW X5.

Install PriorityStart Pro in BMW X5.

32. Replace cargo area floor.

33. All done.

34. Just in case, if you have them, carry a set of jumper cables for a while until you are sure there is not a problem with the PriorityStart or your installation of it.

PriorityStart does not fix the parasitic electrical drain but at least prevents suddenly being stranded due to a dead battery. Eventually, I would like to track down the actual problem but that is going to take time and motivation I do not have right now.


Update 20 March 2010:

So after PriorityStart install, all seemed good. How could it be otherwise with PriorityStart disconnecting X5 electrical load if battery voltage drops to 11.7 volts. Well guess what, other day I went to start car and battery dead!!!!! So take battery out of car and put on charger. Charges right up! Crap. Nothing left to do but take to Auto Zone where I bought it and have them test it and tell me it is fine. Well it was not fine. Had only like 560 cold cranking amps!

Now in PriorityStart install literature, it clearing says or suggests that you get a new battery and if you think about it, you probably installed a PriorityStart because you have been experiencing a dead battery and so really is possible that battery is bad. After reading, apparently batteries do not like to be cycled, meaning drained down to nothing and then recharged. After a few cycles, battery begins to loose its ability to hold a nice, solid charge. SO, DO YOURSELF A FAVOR AND WHILE YOU HAVE THE CARGO AREA OF THE X5 OPEN, REMOVE THE BATTERY AND AT LEAST HAVE IT TESTED.


Update 21 June 2011:

Wife recently took X5 on trip and after reaching destination, SAV sat for a week. When she went to use X5, found her remote entry key would not work although car unlocked with key on driver's side. Also said the remote control of the tail gate did not work until she got into car. And the point of telling you this? Obviously battery voltage dropped below ??volts and the PriorityStart disconnected the battery like is is supposed to do. Sure I have told wife about PriorityStart but apparently did not sink in.


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