Replacing Aurion Mayday ECU backup Battery

[bje]

Toyoya Link send an SMS about a message on my phone for Mayday ECU backup battery low. Changing this battery with dealer was going to cost me more than $300. hence decided to do it myself. With ideas from other posts in the forum I successfully opened the "Black box" hanging in the boot , located the battery and took it out. Reading only 5.3V against rquired 7.2V. Its a 7.2V NiCD battery. Checked online for Ni MH battery which is better. Found many options - Can buy 6 of C Size chargeable battery with tabs and solder them together or can buy assembled 6cell 7.2 V battery . Cost varying from $25 to $60 including shipping. The connection need to be taken from the old battery and soldered on to the new one.

The suggestion in one of the topics that the rear seats need not be removed came out very handy. Pulled out the side panels with SRS Airbag written on them.( Not hard; Gently pulling at each plastic pin briings it out. Once both sides are removed the tray also lifts out easily. Had to do some mucking around to take the tray out as 3 sealts were coming on the way. Loosening the belt make it easy to remove the tray. Then you have another layer with padding which pulls out very easily. Now the speakers and the nuts mounting the May day ECU are exposed. 12mm ratchet spanner easily removes the 4 nuts. Now the box will hang from 2 plastic clips. Pull out the antenna plugs and other connectors by pressing their locks. One cable tie need to be cut to release the big cable bunch. Slowly slide it out of the 2 plastic clips while having some one to hold the "black box" or it will fall in the boot.

Now the plastic cover holding the battery is visible held by 6 torr screws. Once the cover is removed the battery is exposed. It is made of 6 C Size chargeable cells of 1.2 V each. Dimensions roughly 140mm x 47mm x 25mm . Any chargeablel battery pack close to this dimension and rating 2.5Ah, 7.2V should do the job. original replacemnt from Toyota available for about $80

Have ordered a battery from ebay USA. Till that time I have kept the black box out. Will put it back once the battery arrive.

( Search on ebay "Onyx NiMH 6C 7.2V 2500mAh Stick Battery "

See some photos below

Took me about an hour to get to the battery following above steps without disturbing the back seats. The car is running with no issues with the black box out

Edited December 1, 2012 by bje

[b-mc0]

Many Thanks newbie for this very helpful post.

My battery was held in the Mayday Unit by tamper proof screws which I managed to undo with an allen wrench.

I bought a replacement battery pack from Battery worked. It was not a Toyota unit but just a generic 7.2V nicd pack. I think that the design is poor. Not only is the battery under constant charge causing poor battery life but it is the very dickens to replace as you quite rightly point out. I got longer leads with my replacement battery so I can mount it outside the box. That way, next time the battery fails I can replace it easily from within the boot. I don't mind paying $30 every couple of years and doing a 10 minute replacement myself rather that paying Toyota $300 have having to pay one of their blokes to do the tedious replacement process. BTW, my battery volts had fallen to 6V indicating that one cell had gone short circuit. Toyota Link had not detected to low volts yet but the red led had come on. Also, be warned that as soon as you unplug the unit, Toyota Link will phone you to say that there is a security alert from your car.

[matt36415]

Hi, showing my ignorance here, what is the Mayday unit? What does it do?

thanks