Date: Tue, 12 Mar 2002 04:53:41 GMT
From: Bill Jeffrey <NOSPAMwjeffreynopsam.mit.edu>
Subject: Re: 93 900 turbo battery charge


Some good ideas here, John. 'Course, if there was a hidden drain, I would expect the alternator to recharge the battery and make up for it each time I drive. The battery should (ideally) never go dead unless I park the car for a long time. In my case, I drive it at least every couple days, and for at least a dozen miles reach time. Measuring discharge current from the battery when the car is off is a good idea. How much should I expect to see? Clearly the radio and the engine computer will draw a bit, but I just don't know how much I should expect to see. What I really would like to have is a full-time ammeter that measures net charging current. Before the invention of idiot lights, cars always had an ammeter, and I thought about adding one to my 900. That way, if there were, for example, a relay that occasionally sticks closed, I would be able to see the discharge when I turn off the ignition key. However, the Saab wiring layout makes installing an ammeter inconvenient at best. The charge current flows from the alternator to the starter main lug and then to the battery through the big starter cable. The discharge current flows out from the battery in an entirely separate cable. There is no single place where the net charge/discharge current can be measured. I guess I can re-route the wires, but it is messy at best. Disconnecting the battery for a couple weeks would be an interesting exercise, and I think I have a time coming up when I can arrange to do that. I'll try it. Meanwhile, thanks for the thoughts - and keep 'em coming. Bill Jeffrey ========================= John Hudson wrote: > > G' Day Bill, > Sounds like there's some drain on the battery when the car is not beng > driven. Could it be a glove box light? How about disconnecting the battery > for a week or three and see if it still goes flat? Of course you'll need to > input the the radio code when you reconnect it. If you have a digital > multimeter try setting it to current (amps) range and see if you can measure > any discharge by disconnecting the ground post on the battery and connecting > the meter between the ground post and ground lead. > -- > Regards, > John Hudson > Brisbane Australia > 1993 900i 2.1 16 v. > > "Bill Jeffrey" <NOSPAMwjeffreynopsam.mit.edu> wrote in message > news:3C8CD4AB.D66161DAnopsam.mit.edu... > > Did anyone catch Car Talk last week? A lady called in to ask why the > > battery on her 93 900 turbo convertible won't stay charged. t takes two > > SNIP < > > I have been fighting exactly this problem for at least three years on > > this exact car (about 100K miles).> Any ideas? > > SNIP< > > Bill Jeffrey > > > > ====================== > > If "NOSPAM" appears in my return address, you must remove it after you hit > REPLY. ====================== If "NOSPAM" appears in my return address, you must remove it after you hit REPLY.

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