Hi all, I need a recommendation for a battery, (make and model or type number) The two I got with the cars are now defuncked! They were also too big. Also which other cars have the same type of battery clamps for securing the battery. Thanks in advance for your help.
Tel
(See my FAQ page six, which covers batteries for the Murena)
The Murena had a small battery which was only 135mm wide at the hold down strips along the base where the clamps fasten. Originally it was 265CCA (cold cranking amps) with a 35-40Ah rating. You can do slightly better today with the same size since an '049' battery will have 300CCA (so more starting power) and a similar or better 40-45 Ah rating. These are wet Lead-Acid batteries. You might sometimes see a better one with 330CCA but these don't always have the hold down strips at the base for the clamps and are specified as 129mm wide; so you will have to devise another method to secure that battery.
A.G.M. (advanced glass mat) batteries which usually contain a gel and not a liquid, are much better, and as Paul says only lose about 1% charge per month compared to a lead-acid battery which can lose 1% per day, but they are generally up to four times the cost here in the U.K. They also must have a special charger if you charge the battery yourself as they don't like rapid charging or heat, so the charger monitors the battery whilst charging.
One of the biggest advantages of an A.G.M. battery is that you can 'deep cycle' it. This means you can re-charge it when it has gone very flat and the battery suffers little damage. A modern wet lead-acid battery cannot be deep cycled any more like proper lead plated batteries used to be cable of, back in the fifties or before. If you let a modern lead-acid battery go flat (even sometime down to 70% charge) and then recharge it, it will never be as good and can let you down at a moments notice. This is because as the charge drops really low the plates sulphate and the battery will never be as good afterwards. You could be using the car fine one day and next day the battery is flat and won't even turn the engine over! The answer is to use the car regularly and never let the battery go flat.
Because they only lose charge very slowly A.G.M. batteries are often used in boats which get intermittent use and some people use them in classic cars for the same reason. However, the range is very limited especially in the size we need in the Murena, so there is only one I know of in the U.K. that is suitable and that is the Optima 'yellow top' YTS 2.7 which costs around £130 and does not have the hold down strips either, so you would have to devise another method to secure the battery. It does have a higher specification as it is rated at 460CCA and 38 Ah and should have a multi-year warranty but one stockist only claims a one year warranty, which is pathetic for such an expensive battery. In comparison a Varta B32 or B34 '049' lead-acid battery has a 4-year warranty! Yet the Optima should outlast any lead-acid battery and should last probably 10 years or more.
Roy