Guest Posted November 2, 2013 Share Posted November 2, 2013 Picked up my car from Caterham yesterday and drove it back around the M25 towards Surrey. The traffic was terrible as was the weather and i spent the best part of 30 miles crawling through traffic at barely more than idle. Getting thoroughly bored with the situation, I finally pulled into the new Chobham services to get some lunch. When i got back to the car some 30 minutes later it would not restart. The battery wasn't strong enough to turn the engine over. As luck would have it, an RAC van was parked nearby so I asked the chap if he'd be kind enough to jump start it for me. Nice guy that he was, not only did he do that but he also had a look at what the alternator was giving off in terms of current under different conditions. Turns out that with just the headlights on (dipped beam), and engine at idle, the battery is actually being discharged overall (minus 4 or 5A i think it showed). With the headlights off it was just about OK. as soon as the revs came up to about 1.5k-2k then I was OK whether lights were on or off. My question is, is this normal or would one ordinarily expect for the alternator to be charging the system even at idle? Could it be that i have a lazy alternator or are the ones fitted to Caterham's deliberately quite small? Cheers Tom Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted November 2, 2013 Share Posted November 2, 2013 Did you leave the lights on when parked .... easy to do. Switch off headlights when idling ...... are you aren't moving at this point. Never had this problem, so not had occasion to measure it. Link to comment Share on other sites More sharing options...
Guest Posted November 2, 2013 Share Posted November 2, 2013 Nope definitely turned them off when parked up as I'd forgotten initially and as I walked away noticed they were still on. I couldn't really turn the lights off whilst still moving as it was pouring down. I think because I was travelling so slowly in traffic the revs were at barely more than idle for a while. Still surprised it managed to drain the battery that quickly though. Link to comment Share on other sites More sharing options...
DJ. Posted November 2, 2013 Share Posted November 2, 2013 It doesn't seem right to me, I certainly don't turn my headlights off (on my Sigma 125) when in a traffic jam and haven't had any problem with the car restarting. In fact, i've often run with headlights, heated screen, heater blower and wipers going and no problems so far, but admittedly I haven't tried all those in a 30min traffic jam Sorry to hear you had this trouble on the way home today ☹️ Duncan Link to comment Share on other sites More sharing options...
prangerman Posted November 2, 2013 Share Posted November 2, 2013 The two Sevens that I have bought from CCS had to go back within a few weeks for new batteries. On the second car the battery that came with it was supposed to be new but it wouldn't keep its charge. In both cases CCS supplied replacement new batteries without quibble and the replacement batteries were trouble-free. Peter Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 2, 2013 Member Share Posted November 2, 2013 Could be duff battery or duff charging. What's the voltage across the battery at idle and at 3000 rpm? Jonathan Link to comment Share on other sites More sharing options...
CharlesElliott Posted November 2, 2013 Share Posted November 2, 2013 Doesn't sound right. Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted November 2, 2013 Area Representative Share Posted November 2, 2013 Even at tickover, the alternator should provide enough power to power all of the cars systems. Is the alternator drive belt tight enough? As "power" is the product of torque multiplied by speed, at tickover, the alternator is at its most difficult to turn. The faster it turns, the less likely it is to make the belt slip. Link to comment Share on other sites More sharing options...
Grubbster Posted November 2, 2013 Share Posted November 2, 2013 Shame to hear that the experience is still not what it should be Tom ☹️ In 10 years of sevenning, (mostly with lights on when on the road) I've never discharged the battery like this so it sounds like something is wrong Link to comment Share on other sites More sharing options...
7TOM Posted November 2, 2013 Share Posted November 2, 2013 Hi check your charging and battery. Lights don't take a lot of current it's most likely your fan drawing it in traffic. You should have around 13.5 to 14.5 volts at fast idle and would not expect it to drop below 12.5-13 at idle. Also this is the time of year a battery will show its weakness. Link to comment Share on other sites More sharing options...
OliverSedlacek Posted November 2, 2013 Share Posted November 2, 2013 I had this problem some years ago, that the alternator wouldn't run the ignition, lights, wipers, heater and heated screen at idle. This was on an XFlow with a Lucas 45A alternator. I replaced it with a 55A alternator and made sure the idle was always set to at least 800 rpm and haven't had the problem again. It's certainly nothing to do with the battery! I wouldn't expect this to be a problem on a more recent car, so I would get the alternator checked and also look for unexpected electrical loads. Link to comment Share on other sites More sharing options...
Gasmaninaseven Posted November 3, 2013 Share Posted November 3, 2013 As the weather was bad, did you have the heated screen on? To my surprise, this remains live with the ignition off on my car leading to a flat battery... Link to comment Share on other sites More sharing options...
redlight Posted November 3, 2013 Share Posted November 3, 2013 Batteries, Banner Type, only last about three years from my 20 years of Sevening experience. How old was the battery on your car? A new battery makes a huge difference. I have just replaced mine after 3 years as it would not hold a charge, the engine now flies around when starting. Link to comment Share on other sites More sharing options...
Grubbster Posted November 3, 2013 Share Posted November 3, 2013 It's a brand new car, just registered. Link to comment Share on other sites More sharing options...
OliverSedlacek Posted November 3, 2013 Share Posted November 3, 2013 If the alternator doesn't provide enough current, then it's nothing to do with the battery Link to comment Share on other sites More sharing options...
Paul Deslandes Posted November 3, 2013 Share Posted November 3, 2013 I would certainly check the alternator belt tension first. Dipped headlights plus sidelights, instrument lights and engine electrics will pull about 12 Amps which either have to come from the alternator or the battery. If the fan was coming on that would take it up further by an amp or two, some of them take a lot more. Assuming CC haven't reduced the pulley ratio too much to stop the alternator over revving at warp speed, the alternator should be just about able to provide enough current at idle. Link to comment Share on other sites More sharing options...
zetec Posted November 3, 2013 Share Posted November 3, 2013 have they wired the alternator correctly?? proper earth connections etc?? Link to comment Share on other sites More sharing options...
sjmmarsh Posted November 3, 2013 Share Posted November 3, 2013 When I had my CSR mapped at the 'two Steves', he was surprised that my CSR was charging at idle - said that most 7s discharge when just ticking over, so any power drain (lights, fan, heated screen) will only put more drain on the battery. Steve Link to comment Share on other sites More sharing options...
Guest Posted November 3, 2013 Share Posted November 3, 2013 Thanks for all the comments everyone and apologies for being slow to reply. I've been out in the car today enjoying the break in the weather 😬 Ok, so last night I put the car on the charger so it was fully charged this morning. At standstill with the engine off, the voltage was showing 13V. Pretty good but I guess expected given it was fully charged. I then started the car and at idle, the voltage was 14v which I thought was pretty good. Leaving the car a while to warm up so that the fan finally came on saw that figure drop to 12.8v. With the headlights also turned on, the voltage was showing a bit less and appeared to be dropping the longer I sat there with the voltmeter. The biggest change in voltage appeared to be when the fan came on. I'm presuming then that being sat for a prolonged period in traffic will have meant that both the headlights + fan coming on would have resulted in a net loss / drain on the battery. To answer some Q's raised by others on this thread: - Belt is defo tight. Its a self tensioning belt and I can see it turning the alternator over fine at idle. - Battery is new, as is the car. Could be that the battery is not particularly good. How would I know if the battery was duff and not taking a charge very well? Anyhow, I've done about 100 miles today of varied driving (great fun it was too :) ) and not had the problem reappear so I'm hoping this is not a problem I'm going to see again given as I have no plans to sit in heavy traffic in the dark if I can at all help it. Link to comment Share on other sites More sharing options...
Guest Posted November 3, 2013 Share Posted November 3, 2013 Quoting sjmmarsh: When I had my CSR mapped at the 'two Steves', he was surprised that my CSR was charging at idle - said that most 7s discharge when just ticking over, so any power drain (lights, fan, heated screen) will only put more drain on the battery. Steve Thanks Steve, in a way that backs up my own findings then in that case. I guess I could speed up the idle a little bit? I think its about 900 rpm at the moment. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 3, 2013 Member Share Posted November 3, 2013 Quoting TomWoodis: Ok, so last night I put the car on the charger so it was fully charged this morning. At standstill with the engine off, the voltage was showing 13V. Pretty good but I guess expected given it was fully charged. I then started the car and at idle, the voltage was 14v which I thought was pretty good. Leaving the car a while to warm up so that the fan finally came on saw that figure drop to 12.8v. With the headlights also turned on, the voltage was showing a bit less and appeared to be dropping the longer I sat there with the voltmeter. The biggest change in voltage appeared to be when the fan came on.And if you lift it to 3,000 rpm when it's dropped to 12.8V what happens? Jonathan Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted November 3, 2013 Share Posted November 3, 2013 Just a thought ... is it a wet battery ? Check the liquid level in every cell. Link to comment Share on other sites More sharing options...
Guest Posted November 3, 2013 Share Posted November 3, 2013 Quoting Jonathan Kay: Quoting TomWoodis: Ok, so last night I put the car on the charger so it was fully charged this morning. At standstill with the engine off, the voltage was showing 13V. Pretty good but I guess expected given it was fully charged. I then started the car and at idle, the voltage was 14v which I thought was pretty good. Leaving the car a while to warm up so that the fan finally came on saw that figure drop to 12.8v. With the headlights also turned on, the voltage was showing a bit less and appeared to be dropping the longer I sat there with the voltmeter. The biggest change in voltage appeared to be when the fan came on.And if you lift it to 3,000 rpm when it's dropped to 12.8V what happens? Jonathan About 13.5v Jonathan. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 3, 2013 Member Share Posted November 3, 2013 I feel that my contributions on electrics become rather supererogatory when Paul is advising... ... but I'm not sure that there is an explicit fault but rather that the charging is just marginal at idle and that with enough circuits running it isn't quite enough: see related comments and calculations above. It is possible that there is a poor connection in the charging circuit, either on the live or earth side. You could inspect and remake all of those or measure the voltage directly across the alternator terminals, again both at idle and at 3,000 rpm. Jonathan Link to comment Share on other sites More sharing options...
oldbutnotslow Posted November 4, 2013 Share Posted November 4, 2013 Just for reference a fully charged battery after standing for 1 hour without charge or load should give a reading of 12.65 volts Idle charge should give 14.25 volts If it discharges as you have described either there is a fault with the alternator:- belt lose or the alternator charging side internally is faulty or the battery is US Link to comment Share on other sites More sharing options...
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