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MG TD TF 1500 - AGM Battery

I want to replace the lead acid battery in my TD with an AGM battery.
The Interstate Battery website indicates that it will work with a 1950 MG TD. However, my car is not a standard 1950 MG TD. It is still positive ground but my concern is the charging circuit. I have replaced the generator and regulator with an alternator.
So my question is will the AGM battery have any problems with the alternator conversion?
Will it charge safely and properly?
Thanks,
Mort
Mort Resnicoff

The battery doesn't care if you have a generator or alternator. 12 volts is 12 volts. I've run AGM batteries in most of my classics for ages, with both generators and alternators.
Steve Simmons

In my wife's modern car we went from EFB battery to AGM and I was told all sorts of things like the AGM battery doesn't need to be charged above 80% (you don't need to fill your fuel tank either) and that the battery shouldn't be charged over 13.8v so you need a special charger rather than the 30 year old 4amp I have. Yet my neighbour's modern trick charger and tester has a special setting for AGM with a 0.2v higher charge rating at 14.6v (14.8 winter (-20c to 5c)) as per attached pdf.

I also had the urine extracted from me as I put that a long, low and slow recharge of a drained battery was better than a quick, high and fast recharger, especially if it'd been a long, low and slow discharge.

But I didn't realised the battery had to be coded to the car's evil VW computer programs, that was a fun learning experience and showed what nonsense they'd also been pushing before as two of the three details were monkeying around, the factory battery serial number was 1111111111 for my wife's car and all the cars I referenced.

Gawd knows what Tesla might be up to with the car's interconnected programs, possible only the Chinese, Russians, Mossad and Elon really know, and perhaps some criminal gangs. 🤣
Nigel Atkins

Thank you Nigel. That was very helpful. Now I know exactly what to do.
Mort Resnicoff

This from a trusted mechanic:

Put a volt meter on the battery and start the car. Load the alternator up by putting the lights and blower on high. See what the alternator charges at. That will tell you all you need to know. Like I said AGM batts optimal charge is 14.2v – 14.8v. Trust me I have been a “Certified Master Technician” for 42+ years.
Mort Resnicoff

Mort,
hopefully you won't need to code in your AGM battery to your 1950 MG TD. 😊

I should have read your post better, I usual put that car batteries are one of the most over sold car parts often they just need properly recharging or rejuvenating/reconditioning (see the pdf I forgot to attach last time).

As your mechanic has put test your current (no pun intended) and if required properly recharging or rejuvenating/reconditioning.

This is what I put on another recent post -

Check after the engine hasn't run for a good while, take a note of the figure, then if you can get someone to start the car and note what the multimeter figure is at starting and after it measure with the engine (and alternator) running and note all three figures.

Cheap digital multimeters tend to be a bit inaccurate and unreliable but the difference in figures should show what's needed.
Nigel Atkins

I've had an Optima in my positive ground 55 TF for 6 years and never had a problem. PJ
PJ Jennings

Paul, are you using athe generator or an alternator?


Mort Resnicoff

Mort, I'm using the rebuilt generator. The Dynomator I have quit working so I rebuilt and put the generator back on and reverted back to stock wiring. PJ
PJ Jennings

Mort,
your battery and charging seem OK to me with those figures - note I am NOT an expert in this or any thing else.

To confirm the battery you would need to repeat the readings from starting the car and just after a few times in succession to see if the battery falls (drops) off with this test/use.
Nigel Atkins

I have a CTEK charger that has the AGM setting (like most do now) it charges and maintains the battery well.
M Hyde

Agree with Mr. Hyde, use a charger designed for AGM batteries, conventional chargers can damage them. PJ
PJ Jennings

Paul,

Assuming you are using incandescent headlamp bulbs it all looks good the me.

Digital multi meters are very good, however in this case it is better to use an analog meter. I use one with a 15V scale so that an accurate reading can be interpolated. Back in my "electronics" days we use ones with a mirror behind the needle to avoid parallax errors when reading.

I would monitor the battery over a period where you are not using the car, see if it maintains that steady 13.6V for a few days.

I use an AGM battery for Antique Auto Battery, I know they had some issues but have not heard lately if they are "up and running" again.

Peter
P G Gilvarry

I put a lithium battery in my 1999 Excelsior Henderson motorcycle and purchased the "new modern technology lithium charger" . My brother ask why I had to buy a new technology charger when my motorcycle was using 1999 technology to charge it. I had no answer for that. It's now 7 years later and the motorcycle has kept it charged just fine.
rich40701

This thread was discussed between 12/07/2022 and 30/07/2022

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