AndrewElvisFan Posted May 30, 2015 Share Posted May 30, 2015 Hi all hope someone can help me out here. I need to get a new battery as mine has died completely - can't hold a charge for more than a couple of miles. My problem is is that I need my bike working on Monday morning so have to get a battery tomorrow and cannot find anywhere with the correct battery in stock. Ideally I need 40A and 7Ah, the closest I can find is a 45A / 4Ah. It is my understanding that the Ah is how long it will hold a charge for. If this is right, would it be that big a deal on a '94 SR125 which is used daily and only basic electrics (lights etc) in use? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 30, 2015 Moderator Share Posted May 30, 2015 The way that works Andy is the battery capacity is shown by in this case 40A, 7AH. What it is saying is 40A cranking capacity. Its continuous load is 7Ah ie 7 amps per hour. This doesen't mean it would be flat in 6 hours running 7A. It would be 'flat' long before that (actually at around 80% capacity serious damage is done, under 60% is critical). What it is saying is that the battery can continuously deliver 7A per hour, that is intended to work with a charging system putting approximately that back. The 45A battery is capable of supplying more as cranking output but will be at a disadvantage in normal running. 4A may well be fine for this time of year but it wont last, it will work but as I said it wont last. Normal daylight will be engine, ? Brake light 21w Sometimes indicators 42w Total maybe 70W with some engine load. Or 6A Peak daytime. Evening, as above but with what? 35w in the headlight that's 3A plus 5 for the tail and prob another 5 for the idiot lights/dials that's another amp with load. So your night time peak could be 10A certainly a continuous 5 or 6 allowing for losses can be expected. Explains the 7Ah. Link to comment Share on other sites More sharing options...
AndrewElvisFan Posted May 30, 2015 Author Share Posted May 30, 2015 Ok. Cheers Jason. As I have my lights on all the time that's a no brainier. Looks like it's the car for me Monday! Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 30, 2015 Moderator Share Posted May 30, 2015 Sorry mate. Link to comment Share on other sites More sharing options...
AndrewElvisFan Posted May 31, 2015 Author Share Posted May 31, 2015 No worries - you've saved me wasting some money so thanks! Link to comment Share on other sites More sharing options...
AndrewElvisFan Posted May 31, 2015 Author Share Posted May 31, 2015 So I'm thinking I could perhaps use a 9Ah? At 5000rpm I have charging capacity of 9A: Link to comment Share on other sites More sharing options...
slice Posted May 31, 2015 Share Posted May 31, 2015 That would probably be the MAX output your bike is capable of Andrew, not sure you want to run it flat out all the time. You really want the average that your bike puts out not max or min. Link to comment Share on other sites More sharing options...
AndrewElvisFan Posted May 31, 2015 Author Share Posted May 31, 2015 So a 9ah battery just wouldn't charge unless I was revving the hell out of it? Link to comment Share on other sites More sharing options...
slice Posted May 31, 2015 Share Posted May 31, 2015 No it will charge but slowly due to your not whacking the shit out of your engine, as above if you use 7amps then it will be ok but you will not get a full 7 amps in return all the time cos your bike only puts out 9amps at 5K with V14 volts, that's about max for most bikes even the big ones, my FJ puts out 14.5 volts at 3K. Wait till Monday and buy the right one then you'll be ok for another couple of years. 1 Link to comment Share on other sites More sharing options...
AndrewElvisFan Posted May 31, 2015 Author Share Posted May 31, 2015 Cheers for that. Resigned myself to waiting for right one now. Borrowing my car tomorrow now! Link to comment Share on other sites More sharing options...
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