Sounds like the new battery still needs a bit more charging. Personally, my SD sits for days at a time so I also use a plug-in charger occasionally to maintain the battery. There are fairly inexpensive (<$100) computer-based chargers these days which are useful if the car doesn't run enough.
-----Original Message----- From: Mercedes [mailto:mercedes-boun...@okiebenz.com] On Behalf Of WILTON Sent: Thursday, May 30, 2013 10:07 AM To: Mercedes Discussion List Subject: Re: [MBZ] '91 350SDL not charging? - starter? SDL (new) battery voltage this morning before starting = 12.31; car started easily with just a touch of starter; "charging" voltage at idle = 14.23; after idling for 15 min. or so, charging V = 14.03; after shut down, bat V = 12.58. Belt is plenty tight, but I did notice idler pulley slightly askew (not properly aligned with belt), so 'hafta address that again; new pulley assembly installed several years ago for same. Wilton ----- Original Message ----- From: "Scott Ritchey" <ritche...@nc.rr.com> To: "'Mercedes Discussion List'" <mercedes@okiebenz.com> Sent: Wednesday, May 29, 2013 7:26 PM Subject: Re: [MBZ] '91 350SDL not charging? - starter? > > Wilton: Oh by the way. Are your alternator belts tight? If the belt(s) > can slip you will still see a nice 14.x volts with a well-charged battery. > But a discharged battery will load the alternator causing the belts to > slip > and the battery won't get charged. I found out the hard way. > > -----Original Message----- > From: Mercedes [mailto:mercedes-boun...@okiebenz.com] On Behalf Of Scott > Ritchey > Sent: Wednesday, May 29, 2013 7:16 PM > To: 'Mercedes Discussion List' > Subject: Re: [MBZ] '91 350SDL not charging? - starter? > > > Wilton, I think your voltages are OK. It's normal for a NEW battery to be > somewhat discharged. It likely sat on the shelf for weeks between the > time > the electrolyte was added and the time you bought it. All lead-acid > batteries self-discharge. The fact you saw 14.2+ volts with a relatively > "topped up" battery (from the 300D) indicates descent alternator function. > > Lead-acid batteries die for a variety of reasons but chronic undercharging > (or sitting without recharge) is the most common cause. > > You generally cannot draw a conclusion from just the battery charging > voltage unless you also know the charge current or the battery state of > charge. > > I don't have tech data all Bosch regulators. But here's what you should > see: > > Phase 1: The alternator will put out the maximum charge current until the > voltage reaches 14.2-14.4 volts. The RPM limits the maximimn current the > alternator can produce. With the engine idling, this may not be a lot of > current so the voltage could be anything between 12.5 volts and 14.4 > volts. > If you rev the engine the alternator should produce more current and you > should see a higher voltage in this phase. > > Phase 2: The battery is mostly charged and the alternator can produce > more > than enough current to get the voltage to 14.2-14.4 volts. Now the > regulator reduces the charge current so the voltage does not exceed the > preset 14.2-14.4 volts. If you drew a graph of current vs time you would > see the current tapering off asymptotically as the battery approaches full > charge. > > Plug-in battery maintainers and some AC chargers have a third phase where > the voltage drops down to about 13.8 volts (trickle charge) after the > battery is fully charged (defined as charged to the point the charge > current > below threshold at 14.x volts). I don't know if Bosch regulators do this > or > not. Because you don't drive 24 hours a day for days at a time, this > trickle mode isn't as important in an alternator. > > > > -----Original Message----- > From: Mercedes [mailto:mercedes-boun...@okiebenz.com] On Behalf Of WILTON > Sent: Wednesday, May 29, 2013 5:02 PM > To: Mercedes Discussion List > Subject: Re: [MBZ] '91 350SDL not charging? - starter? > > My thoughts, too, 'bout "charging" voltage. Shoulda called it "voltage > across bat terminals with engines at idle and no load on systems." Didn't > chk bat V before starting and after running few minutes, but I suspect > both > bats are fully charged; SDL bat is new/never driven. I'll check V's again > tomorrow before starting, running, run bat's down a bit with headlights on > with engines off, then chk V for re-charge, etc. Not gonna mess with 'em > any more today. > > SDL charging V was 14.27 yesterday with 300D battery in it after having > "tortured" that battery the day before trying to "jump" start SDL. > > BTW, both start in the usual manner with just a touch of starter. > > Wilt > > ----- Original Message ----- > From: "Craig" <diese...@pisquared.net> > To: "Mercedes Discussion List" <mercedes@okiebenz.com> > Sent: Wednesday, May 29, 2013 4:15 PM > Subject: Re: [MBZ] '91 350SDL not charging? - starter? > > >> On Wed, 29 May 2013 15:59:43 -0400 "WILTON" <wilt...@nc.rr.com> wrote: >> >>> Engines at idle. >> >> The 300D voltage is very low. >> >> The SDL voltage is a little low. >> >> >> Craig >> >>> > On Wed, 29 May 2013 15:40:27 -0400 "WILTON" <wilt...@nc.rr.com> wrote: >>> > >>> >> 300D charging V now, with its "old" battery and after driving it on 2 >>> >> trips "around" town today = 13.10. >>> >> SDL charging V now (not driven since new battery yesterday) = 13.77. >>> > >>> > Are those voltages measured with the engine running (and preferably >>> > above idle)? >> >> _______________________________________ >> http://www.okiebenz.com >> For new and used parts go to www.okiebenz.com >> To search list archives http://www.okiebenz.com/archive/ >> >> To Unsubscribe or change delivery options go to: >> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > > > _______________________________________ > http://www.okiebenz.com > For new and used parts go to www.okiebenz.com > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > > > > _______________________________________ > http://www.okiebenz.com > For new and used parts go to www.okiebenz.com > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > > > > _______________________________________ > http://www.okiebenz.com > For new and used parts go to www.okiebenz.com > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
