Absorbed Glass Mat battery - how to recharge when completely flat

I failed to do the former about 10 years ago. But don't worry, there is just as much as there was earlier, which is not a lot :-)

NO it's soaked into a matt , as in the name. The chemistrys the same & the chargings closer to a flooded cell than a gel cell. All the matt does is stop it sloshing around.

Which says it's a lead acid battery with a fibre matt to stop the acid sloshing around. & offers some minor mechanical support to the plates.

Oh, every man and his dog claims to make a sealed battery which isn't a gel type. But the correct name for these is semi-sealed.

I have an 03 MX5 as well, an have suffered from a flat battery when left. The electrics seem to drain quite a bit, and the alternator seems not to charge completely.

As your neighbour will undoubtedly have to take your advice on a trickle charger, it might be worth trying an Optimate as they are suitable for up to 28AH and the Westco is only just above at 31AH, and as Duncan has stated they are designed to recharge deep discharged batteries

Once you've flatted them they're never as good again, it's whether they're good enough :-) If they get frozen whilst they're flat they're scrap. The optimate will happily maintain the battery for months, or maybe even a couple of years (although selling the car & buying another one would make more sense) , recovery depends on how shagged the battery is.

Have you measured the quiescent current drain? If this is heavy *and* the alternator doesn't charge properly it could be a faulty rectifier diode.

If permanent float charging isn't possible and the vehicle is going to be left for some time, simply disconnect the battery or better still install a master switch. A lead acid battery has a very long self discharge time, and will still be fine after several months.

Good point - I'd not thought of that. If I can ever get the battery to charge I'll try that.

Indeed - the car lives in her garage and there is a socket right by it so a long term float charge should not be a problem.

Thanks.

Tony