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I need one!

I've gone through two Mf31-1000s in two cars, so not happy with them..

Anyone else got a recommendation on one that will fit?

Thanks

H

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Spec for the P38 is an 069 battery - 70Ah and ~600CCA. Positive terminal on front left (back right when fitted). The battery tray can take large batteries so L x W isn’t that important but H <= 225mm. I would treat this as a minimum spec. Batteries with positive terminal front right can fit but may have problems getting the positive cable to reach the terminal if the battery is very wide but that shouldn’t be a problem if you’ve already had a MF31-1000 fit.

Normally the bigger the Ah & CCA the better but the relatively low compression ratio of the V8 means that It spins over quite easily so CCA is not overly critical for an engine in rude health. Same for Ah is the alternator is in rude health. Standard as opposed to AGM is also not that critical.

Currently I have a ‘bog standard’ Halfords’ Calcium HCB072 battery (which is pretty much the minimum spec above) fitted that has just passed its 5th birthday in the vehicle and hasn’t put a foot wrong in all that time. It was procured in an ‘emergency’ but has done really well. I have also had good service from Yuasa 5000 series batteries (in other vehicles) which seem to be reasonable vfm and can be had with relatively high Ah and CCA.

Unfortunately my history with Varta and Exide batteries has never been good!

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What are you doing to kill the Hankook's? I've got one in each P38, have supplied 3 more for other owners and one in a boat with a 4.3 litre V6 and not had a problem with any of them.

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Nowt has been done to them.

It has never been discharged, and has always been above 12.5v

Fine until a few days ago, when it refused to start the car, still reading over 12v weirdly.

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Sounds more like a starter problem that a battery problem. What does it drop down to when cranking?

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I've fitted it to another car to rule that out, still nothing..

And it drops to 9v when cranking

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If this same problem was with two different cars, this is not likely your issue, but here’s what mine was like when I got it. Battery voltage a little low, I think a bit over 12V (all my numbers will be from memory 5 years ago, so not exact). The alternator itself (alt terminal straight to ground) was 14.5, but alt terminal to battery around 13. I cleaned all the wire connections, which improved it a bit but still a big voltage drop Alt to Batt. I then ran a heavy gauge wire directly from the Alt to the batt + terminal (keeping the rest of the wires as they were. I now have almost no voltage drop. According to the vehicles records, the battery was replaced about every 2 years before I got it. It’s still the same battery in it now so it must be around 7 years old. I think the alternator to starter cable must be marginally too small, but my bodge seems to work so I haven’t bothered replacing it.
Good luck with yours Henry.

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Try charging it and see what it drops to when cranking then, it shouldn't go below 11.5V. If it does, it's faulty so time for a warranty claim.

@Harv, your car is a GEMS so has the main power cables going from the battery to starter and starter to alternator. A poor contact at the starter causes the voltage drop and there was a TSB that recommended exactly what you have done, an additional cable from the alternator to the battery. However, this won't be StrangeRover's problem as his car is a Thor which has a cable directly from the alternator to the battery as standard.

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Thanks for that info Richard