MR2 Roadster Owners Club

The Workshop => Maintenance, Problems & Troubleshooting => Topic started by: Brackers on April 21, 2024, 09:29

Title: Flat battery - parasitic draw found and fixed
Post by: Brackers on April 21, 2024, 09:29
My 2003 roadster has suffered from a flat battery if not driven every few days.
First I replaced the battery but the problem continued. To diagnose the problem I disconnected the negative battery lead and connected an ammeter between the lead and the battery. With the ignition off and all doors closed, the car was drawing around 200 mA. I removed every fuse one at a time from the engine bay fuse box,  the fuse box at the passenger side of the dash ("RB3") and the fuse block under the front bonnet. No fuse reduced the draw significantly. The drain remained high. I eventually disconnected the alarm siren which is located in the frunk in the spare wheel storage area. This immediately dropped the current draw down to around 20 mA. I am replacing the alarm siren with a secondhand unit and have bought new batteries for this from eBay. I hope this helps others who might have the same issue.  Here are a few pictures of the faulty siren
Title: Re: Flat battery - parasitic draw found and fixed
Post by: Gaz mr-s on April 21, 2024, 09:39
Well done for perseverance.
Title: Re: Flat battery - parasitic draw found and fixed
Post by: Ardent on April 21, 2024, 10:27
I'd be inclined to leave it out.
Title: Re: Flat battery - parasitic draw found and fixed
Post by: puma2 on April 21, 2024, 11:54
 :) good work to find that out with some patience involved as well  :)
Title: Re: Flat battery - parasitic draw found and fixed
Post by: Topdownman on April 21, 2024, 17:10
Well done.

Will you be testing the new set up once fitted to see if the problem has definitely gone?
Title: Re: Flat battery - parasitic draw found and fixed
Post by: Brackers on April 22, 2024, 09:35
Yes for sure I will test it. You never know with used parts. Might be as bad as my own failed siren 😂
I will also check the current draw once fitted.
Title: Re: Flat battery - parasitic draw found and fixed
Post by: Dagnet on May 20, 2024, 10:29
I have high parasitic current on my car too. I have to disconnect the battery if I don't drive the car for a few days. Will check this out
Title: Re: Flat battery - parasitic draw found and fixed
Post by: Gibla on May 20, 2024, 17:32
Quote from: Dagnet on Yesterday at 10:29I have high parasitic current on my car too. I have to disconnect the battery if I don't drive the car for a few days. Will check this out

Whilst you are investigating(or even afterwards), would a battery isolator switch be useful?

eg

https://www.google.com/search?q=battery+isolator+switch&rlz=1CAZJXP_enGB1104&oq=battery+isolator&aqs=chrome.0.0i433i512j69i57j0i512l8.19261162j0j15&sourceid=chrome&ie=UTF-8

Title: Re: Flat battery - parasitic draw found and fixed
Post by: Carolyn on May 20, 2024, 17:41
Even better - these are very clever.

https://www.ebay.co.uk/itm/226053232446?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=Cj0KCQjw6auyBhDzARIsALIo6v9KwyrYARy9R_PVwqc8ngQg_eCFW2zdVJSjc-f8fUqNHitTV7eYal4aAnQ9EALw_wcB (https://www.ebay.co.uk/itm/226053232446?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=Cj0KCQjw6auyBhDzARIsALIo6v9KwyrYARy9R_PVwqc8ngQg_eCFW2zdVJSjc-f8fUqNHitTV7eYal4aAnQ9EALw_wcB)
Title: Re: Flat battery - parasitic draw found and fixed
Post by: Gaz mr-s on May 20, 2024, 19:34
Quote from: Carolyn on Yesterday at 17:41Even better - these are very clever.

https://www.ebay.co.uk/itm/226053232446?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=Cj0KCQjw6auyBhDzARIsALIo6v9KwyrYARy9R_PVwqc8ngQg_eCFW2zdVJSjc-f8fUqNHitTV7eYal4aAnQ9EALw_wcB (https://www.ebay.co.uk/itm/226053232446?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=Cj0KCQjw6auyBhDzARIsALIo6v9KwyrYARy9R_PVwqc8ngQg_eCFW2zdVJSjc-f8fUqNHitTV7eYal4aAnQ9EALw_wcB)

These can be had for under £10 from China.  Someone I know recently got one.