MGTF battery problems?

Hi all
I know battery problems have been discussed plenty of times on here before. My TF 1.8 has a problem and I'm not sure if it's the battery or something else.
I was away last week and went to start the car at the weekend but the battery was almost totally flat. It seemed to spin the starter without engaging the flywheel then died. I then put it on charge, initially it was charging at 6A but after only a couple of hours reduced to 2A which was hopefully enough to start the car. This i did and ran it up to temperature until both the radiator and engine fans cut in then back out again.
I then went back around 5 mins later, intending to go out, but the battery behaved as if it was almost totally flat again. The engine turned over once and stopped.
Today when the engine was cold it fired up almost immediately although the battery still sounded tired. I've had the car for almost a year and according to the service history the battery was new in 2016.
I took some voltage/current measurements today. Voltage not running is 12.5v and running 13.8v. With the ignition off my multimeter read a current drain of 1A immediately on connecting but then there was a bleep (from inside the car, not sure where) and the current settled down to around 30mA.
My question is this just a case of a tired battery or could the alternator or something else be breaking down?
Grateful for any help

Thanks
Jon

My 2004 TF is very sensitive to a low battery. It will only start with one key & fob and not the other. The car cannot be unlocked. Different conditions shown on the little red led on the display. The battery was continually going flat if the car was left for more than about a week. I looked at the parasitic drain on the battery once and something of the order of 30mA sounds familiar.

Three years ago, I replaced the battery with a new 075 Bosch Silver from Tayna and that helped a lot.

The thing that has made all of the difference is having fitted a DisCarNect battery isolator. This has been a revelation for me as all of my flat battery issues have been resolved. I have not seen any ill effect from disconnecting the battery when I put the car in the garage other than the clock stops.

I have noticed that when I reconnect the battery there is a faint beep from somewhere inside the car. I have no idea what it is but, since all seems well, I've ignored it.

I think that when a car is used daily, the battery causes lees problems than when it is used intermittently. My last daily drive had a 9 year old battery when I sold it and had never given problems.

Hi Jon

To me it sounds like a tired battery, most are only guaranteed for 3 years so this fits with your 4 year old one.

The voltage should be around 14.4v running and around 13.2v when off.

The ECU remains live for up to ten minutes after shut down monitoring coolant temperatures and if needs be fire the coolant fans. This would be the 1amp draw you see.

James

Thank you both for your replies.
Mystery solved, it was a tired battery. I took it to a local garage who did a drop test and found that it was only 65% effective. Also the existing battery was only a 063 so i now have a 075 fitted.

Jon

Its also worth checking the date the battery was manufactured before buying, there should be a label on the battery case. I buy mine from established car parts sources who generally have a high turn over of batteries so they are not left sitting on a shelf for years.

The problem seems to have come back. Things have been fine since the new battery was fitted in July. However over the last 2-3 weeks the starter has turned over quite slowly but the engine has fired. Tonight the engine turned over once then died. I repeated some of the previous measurents. Last weekend the battery was charging at around 14.6v. Tonight the voltage across the battery not running was 11.6v. Current drain tonight was initially 1.5 amps but fell to 250mA after about 2 secs.
I've checked the battery earth strap and the 80A fuse on the bulkhead for corrosion.
Do people think that there is a problem with the alternator or do I have a new but duff battery? It was manufactured in July 2019 and I bought it this July

Thanks
Jon

I have a similar problem with my F. Definitely not a battery problem as it is brand new. Mine will go flat in two or three weeks if i don't use it. A solar trickle charger made no noticeable difference. I have gone for one of those isolaters.

The battery has been on charge for about 8 hours today. The voltage is about 12.6v. I then measured the current being drawn- I think I must have had the boot lid open when I measured it before (hence the light was on) as the current drain was now initially around 1A very quickly falling back to 30mA which is probably about right. I repeated this 2 or 3 times to be sure. I'm starting to think the new battery may be duff. I'll get it tested tomorrow before doing anything else.

I only do short infrequent journeys now, and if I leave the battery connected, it will discharge within 3 -4 days.

I fitted one of those battery disconnects and use it after every journey when the car isn't going to be used for a few days. The battery remains charged.

There is definitely a history of parasitic drain on these cars, as flat battery problems come up a LOT with TFs and Fs.

Discarnect. Best £6 I ever spent on my MG TF. Apart from fun juice, that is

Today my local garage tested the battery and confirmed it was 100%. They then tested the battery voltage under load with heater blower, headlights and wipers on. The voltage dipped to just over 12v and didn't increase with engine speed. They suggested that the alternator was at fault so I'll repeat this test at the weekend and check the output direct from the alternator terminals. Also will check the engine earth strap connections for corrosion before I do anything else.