JJC Posted September 26, 2016 Report Share Posted September 26, 2016 Is 45 a/h enough for a battery ? I don't drive in dark and rain. Car starts every time first go. My original workshop Manuel suggests it is. JJC Quote Link to post Share on other sites
North London Mike Posted September 26, 2016 Report Share Posted September 26, 2016 Sounds like enough, charging rate is the key, if it keeps up with the draw you'll be fine. The Amp hours are to help to starting the beast, max drain, no charge If your still on a Dynamo the battery could supplement very high drain for a short period but not recommended Quote Link to post Share on other sites
peejay4A Posted September 26, 2016 Report Share Posted September 26, 2016 Isn't it cold cranking current that determines how good a battery is at starting? Amp hours is a measure of its stored energy and not an indicator of starting ability. Quote Link to post Share on other sites
Lebro Posted September 27, 2016 Report Share Posted September 27, 2016 +1 AH is the capacity i.e. how long it will supply a current for. 65 AH = 6.5A for 10 hours etc. Cold cranking figure is a measure of the internal resistance of the battery, which if very low will allow lots of current, if higher will limit the current. A CC figure of around 650A, & an AH of around 75 would be fairly normal for a TR. Go less on the AH, and you may run out of energy if it is not a good starter. Bob. Quote Link to post Share on other sites
Ian Vincent Posted September 27, 2016 Report Share Posted September 27, 2016 My philosophy is to buy the biggest one that will fit in the tray. Rgds Ian Quote Link to post Share on other sites
tim hunt Posted September 27, 2016 Report Share Posted September 27, 2016 +1 Ian. I currently have a Varta Blue Dynamic of 95AH capacity and a CCA of 850 Amps. I don't give a stuff that it doesn't look original, the comforting thought is that if it will start a big diesel engine with maybe 18:1 CR then it is well man enough for my 2.1L tractor engine. I also still run a dynamo and the reserve capacity is a reassurance on an all night drive when heater and wipers may be required with the o/d frequently engaged. Tim Quote Link to post Share on other sites
TR5tar Posted September 27, 2016 Report Share Posted September 27, 2016 My philosophy is to buy the biggest one that will fit in the tray. Rgds Ian +2. I use an Optima Redtop on my 5 (815 cca,100 ah). Not cheap, but it has performed very well for me. Cheers, Darren Quote Link to post Share on other sites
McMuttley Posted September 27, 2016 Report Share Posted September 27, 2016 I have a cheap old 'Lion' battery that has never been an issue - always fired. The good news is that it is for sale - you just have to buy the rest of the car too ! Quote Link to post Share on other sites
North London Mike Posted September 27, 2016 Report Share Posted September 27, 2016 +1 AH is the capacity i.e. how long it will supply a current for. 65 AH = 6.5A for 10 hours etc. Cold cranking figure is a measure of the internal resistance of the battery, which if very low will allow lots of current, if higher will limit the current. A CC figure of around 650A, & an AH of around 75 would be fairly normal for a TR. Go less on the AH, and you may run out of energy if it is not a good starter. Bob. +2 sorry, my point was badly expressed, it allows you to keep cranking until it starts (not the power of the cranking) tough crowd Quote Link to post Share on other sites
peejay4A Posted September 27, 2016 Report Share Posted September 27, 2016 Weeell not really. You could have a 100 ah battery with rubbish CCA and it will not start the car on a cold morning. You have to consider both figures. Sorry. Quote Link to post Share on other sites
North London Mike Posted September 28, 2016 Report Share Posted September 28, 2016 Everyday is a school day Quote Link to post Share on other sites
stuart Posted September 28, 2016 Report Share Posted September 28, 2016 Get the biggest one that fits in the space. I had a 3a in the week before that must have had a truck battery fitted as it took up the whole of the battery box and only just missed the bonnet! Interestingly enough it also had a high torque starter fitted too! Stuart. Quote Link to post Share on other sites
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