Long story but I have to take a battery down to the paint shop next week. The one on the car is flat (which rather surprises me). Anyway, problem is I have 2 batteries here one of which may, or may not, have come off the BRM when I last changed it. Or off the Renault 5. Or off the Scimitar! One is 45Ah and the other is a 60Ah job. My feeling is that the larger one came off the Scimitar and the smaller off the Renault 5 but, given the Renault 5 is a 1.7 engine, I would think the latter should be fine if fully charged. I couldn't find the OEM spec of the BRM battery anywhere, but I'm sure someone here can advise me! Thanks. Phil
Information asked is written here: https://thebrm.co.uk/index.php?threads/brm-info-and-technical-data.16/ BRM battery is 45 Ah one.
You can also fit a 063 battery, smaller than a 075. The brm battery tray has two slots for the clamp to bolt too. Mine has the 063 as it shares the battery with the 45 and that is all you can fit to them.
Yes... But... Lets just go through some basics. The battery needs to fit, by which I mean it ideally has the clamp feature at the bottom, but you are perfectly entitled to clamp by other means, if like most Rovers the clamp nut has rusted, seized and spun you can loop a strap or belt round battery and tray. But what it really must not do is foul at the top, with your bonnet. Fortunately our cars are intended to have earth end forwards, which means that will be the end which fouls first, but when the live end fouls you do get an interesting effect occurring! Now lets just look at the battery's power capability. 45ah, amp multiplied by hour. This is all a bit theoretical unfortunately, a one amp load will fully deplete a charged battery in 45 hours...except a 1a load will drag the battery into useless state in quite a bit shorter time. Why, because it wont crank below lets say 9 volts anyway...and below circa 5v the electronics wont work either! Recall V=Ixr so as current depletes, but resistance doesnt, so your volts are lost too. Whats far more valuable to look at is the Cold Cranking Ampage. CCA is a measure of how well the battery can expend its stored energy, which is a function of many variables in its design. This is what will throw an engine over on the starter. The bigger the CCA the stronger the cranking for extended periods. We also know that whilst this is a test in a very cold environment, a warmer 'lead acid' battery has greater amp delivery performance. In the olden days we actually used to do a physical dead engine cranking test to ensure the car could be moved (I think it was 15m/20yds) on level ground in first or reverse. Nowadays thats a bit academic on most new tech cars which rely on just a Faraday rotary engine, but should you ever need to crank a stalled car off the level crossing its the cca which will dictate just how far you get off the tracks! So, in ideal conditions your engine 'lifts off' the starter in about a half a crankshafts revolution, (two firing events) so needs almost no amps perhaps as low as say 250 cca, but if you are inclined to do arctic driving it was designed to self start at -30C, within 30 seconds, and be capable of an assisted start down to -40C... So for your donkey battery, use anything that you can clamp the terminals to, but dont shut the bonnet!, when choosing a replacement, balance price/warranty/CCA/ and your perception of brand name. (I nowadays try to write the supplier, invoice and end of warranty onto the battery before install. They generally claim 2-4 years now, but rely on no one knowing when or who they bought from! You dont need to have the invoice only evidence of it!
Thanks, Roland. Useful, instructive comments as always. Reminds me, I once had to use the battery on the Scimitar to move her off the road when I ran out of petrol on probably the second busiest roundabout in France. The Foux roundabout a couple of miles outside St Tropez. I'm counting the Arc de Triomphe roundabout as the busiest! Anyway, most embarrassing. First and last time I ran the gauge that low!
I wish to share a moment of great joy with you all. Down to the paintshop this morning where the final stages of hand-flatting and polishing are under way. New battery on - and she started absolutely on the button. No problem with the fob operation (thank you Technozen). Just got to sort out the boot lock when I get her back home - and then the MOT. Wonderful feeling!
