Car dead

Newbie57 · April 11, 2024, 15:20

Just tried to start the car and it's completely dead. It's been sitting about a week. Put the charger on the battery and it goes to maintain.
Any thoughts.

Carolyn · April 11, 2024, 15:32

The alarm immobliser does drain a surprising amount of current. Coupled with the small battery, it's nor unusual for the car tp go flat over several days. If the battery has been deep discharged, it may not come back to life, depending on just how flat it got.

An isolator like this will do the trick:

https://www.ebay.co.uk/itm/315195073754?itmmeta=01HV6S2237B34G2D59HRS1VA7Y&hash=item49631724da:g:G~sAAOSwagJl4uiA&itmprp=enc%3AAQAJAAAA8AEYmztVBt7RKSSnFwLj3Be3xO08k1zDJzlpfQE4Pl0haAh4snCGlH8plIrasFr8Y6UBlGCEMQQyrMif0%2F78lsNn7e7G1fOC9x3yGHM5KZBXz9zsBIchNJzFd7gCqqBFuM5JYcVoknL8gTIcfT2l8ekmpBwszFENYSXQ3C5sv3n20mw2SyZ0FxyOtbm8mb6yLQVv0SwOX3zTrheVdIhImacLqpdi0tPzUaR%2BNf47G0xD91IVUvNeNqWSBfvQgTgLRG%2FqNQETXYAtG3%2BS4hMAbfM3CyCay5Q%2BghO5cTxe%2BorgcsFzgKtKuTG7vibI5ETBhA%3D%3D%7Ctkp%3ABFBM2qGI2dlj

Less money but a lot less convenient:

https://www.ebay.co.uk/itm/264539496409?epid=7028124817&itmmeta=01HV6S2237HXVK387J4JRSA1TR&hash=item3d97c85fd9:g:FxAAAOSwcrJd1RsT&itmprp=enc%3AAQAJAAAA0PcvCUAky2uXkfySMr1m69mmHXpTs1xY%2FprbkJkhVqIUJnn%2BnVmAHUuX8n%2Fc9GZlvHZ%2Fn2OqgXgtmyrzDtPWYAT210FTFa6tecE1KwXbB9KkUgoTOVZ1UccgZCGyHvLaH7jgZYq0cinEh3%2By8vjBrwER3a3vScBN2ps6zXMv5kTh80ICOAIsPxjqjrjLzVRMMjQu%2F2COMvMfsnjQydBuDw8hd5KFL4kxX4nkjtxQnGrPh0mJVqzD9IxX9t%2B8KC2ZICGA62avpkZTn9s9YmIvjis%3D%7Ctkp%3ABk9SR9qhiNnZYw

Gaz mr-s · April 11, 2024, 16:38

If the charger won't chime in on it's own, a solution is to wire another healthier 12V batt in parallel & attach the charger. The charger will respond to the higher voltage, but most of the charging current will go into the flat battery. It might take 5 minutes or 50, but if the car worked a week ago I'm sure this'll work.

Going flat in a week suggests either the battery is way past it's best, or not running long enough (30 mins perhaps) to fully charge. If you have a voltmeter, it'd be a good idea to check the voltage when it's charging/charged.

Topdownman · April 11, 2024, 17:03

If you havent already tried this, I would also suggest taking off the battery clamps and cleaning the insides and terminals with some fine grit wet and dry. I have had the oxidisation on these areas mean that the car lights would work, but not enough current to turn over the car.

Newbie57 · April 11, 2024, 17:08

Car has a few good runs recently. Battery is not that old and I have had no issues with leaving it a week before.

Joesson · April 11, 2024, 17:17

Quote from: Newbie57 on April 11, 2024, 15:20Just tried to start the car and it's completely dead. It's been sitting about a week. Put the charger on the battery and it goes to maintain.
Any thoughts.

My reading of this is that your charger is telling you that the battery is charged and just needs to maintain that charge.
Do your ignition lights come on? Do your lights come on?
That being the case perhaps the battery is OK and the problem is with the starting circuit.

Gaz mr-s · April 11, 2024, 18:16

Quote from: Newbie57 on April 11, 2024, 17:08Car has a few good runs recently. Battery is not that old and I have had no issues with leaving it a week before.

Check of alternator output would be a good idea.

tomaky · April 11, 2024, 19:38

how new is the battery? often a battery can charge up to a good voltage but have no amperage. If you dont have a tester (cheap of amazon) halfrauds will test for free.

Newbie57 · April 11, 2024, 21:05

Played around with the 2 chargers I have and finally got one to recognise the battery needed charging. Will see what happens overnight.

Newbie57 · April 12, 2024, 21:09

Up and running.

MarkB1 · April 12, 2024, 23:16

Most modern/digital display chargers won't even start to charge a really flat battery. Best jump starting and running for 10mins then try to charge. I find you only get three to four weeks out of the MR2 battery in the colder weather. I don't use mine much and the battery goes flat quite often. I've had four batteries in 12 years, not using them kills the battery.

Joesson · April 13, 2024, 13:24

Since 2011 when I bought a new car and also a 2002 MR2 I have bought 2 replacement batteries.
A Yuasa in March 2016 for my 2, used 6 months of the year and garaged all year. For the first few years, during the 6 months of no usage I kept the battery on a trickle / maintenance charge but in recent years I simply disconnect the battery, check it occasionally and charge as required. Currently unconnected and at 12.7 V.
My daily had a replacement Yuasa battery in November 2017 at approaching 7 years old and is kept on the driveway.

So, the daily is used as such and my 2 is only for infrequent fair weather use but the batteries both seem to last beyond the 5 year warranty period. Neither battery has been allowed to discharge substantially, maybe that is the key factor in longevity.