# Charging system malfunction **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** is-300, lexus\ **Created:** [December 1, 2023, 3:46am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940 "2023-12-01T03:46:37Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Clueless33](https://avatars.discourse-cdn.com/v4/letter/c/dbc845/32.png) [@Clueless33](https://community.cartalk.com/u/Clueless33)\ **Post date:** [December 1, 2023, 3:46am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/1 "2023-12-01T03:46:37Z")
2018 Lexus IS 300 AWD. FSPORT. Issue: charging system malfunction. Today, when I attempted to start the car, the car refused to start with the message on the dashboard. I then tried again and the car started just fine and no issues from there. Critical info: The battery was replaced last year. I had a remote starter installed 3 years ago by the dealer. Since the weather has become cold, I’ve been turning off and on the car more frequently than should. For example: When I’m idling, I turn the car on to keep the inside warm then turn the car off when I feel warm enough, then turn back the car on when I am feeling chilly again. Hmmm. What else can I report to you so you might have a good idea what’s going on? Ohh, one more thing: The message came on the dashboard while I attempted to turn the car on and not while the engine was running. The message has not came on again. Should I visit my dealer ? Thank you. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [December 1, 2023, 3:49am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/2 "2023-12-01T03:49:58Z")
> [@Clueless33](#): > > I’ve been turning off and on the car more frequently than should. For example: When I’m idling, I turn the car on to keep the inside warm then turn the car off when I feel warm enough, then turn back the car on when I am feeling chilly again. Why are you doing this? Tester ---
**Author:** ![Clueless33](https://avatars.discourse-cdn.com/v4/letter/c/dbc845/32.png) [@Clueless33](https://community.cartalk.com/u/Clueless33)\ **Post date:** [December 1, 2023, 3:52am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/3 "2023-12-01T03:52:09Z")
It’s so cold outside. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [December 1, 2023, 3:57am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/4 "2023-12-01T03:57:02Z")
> [@Clueless33](#): > > It’s so cold outside I know! It gets cold inside too when you turn the heat off! Tester ---
**Author:** ![SteveCBT](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/stevecbt/32/3192_2.png) [@SteveCBT](https://community.cartalk.com/u/SteveCBT)\ **Post date:** [December 1, 2023, 3:58am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/5 "2023-12-01T03:58:38Z")
The constant start/stop could be draining the battery Just leave the engine running and use the controls to adjust the heat ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [December 1, 2023, 4:02am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/6 "2023-12-01T04:02:41Z")
> [@Clueless33](#): > > When I’m idling, I turn the car on to keep the inside warm then turn the car off when I feel warm enough, then turn back the car on when I am feeling chilly again. Do you live in your car? > [@Clueless33](#): > > The battery was replaced last year. If the battery was replaced by your Lexus dealer, it has a 2 year free replacement warranty. ---
**Author:** ![Clueless33](https://avatars.discourse-cdn.com/v4/letter/c/dbc845/32.png) [@Clueless33](https://community.cartalk.com/u/Clueless33)\ **Post date:** [December 1, 2023, 4:03am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/7 "2023-12-01T04:03:35Z")
I used to do that. Idling consumes gas 😔 My gut feeling was telling me not to start and off the car this often. I’ll definitely stop doing it from now on I’ll go get some blanket at the store! ---
**Author:** ![Clueless33](https://avatars.discourse-cdn.com/v4/letter/c/dbc845/32.png) [@Clueless33](https://community.cartalk.com/u/Clueless33)\ **Post date:** [December 1, 2023, 4:05am UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/8 "2023-12-01T04:05:25Z")
> [@Nevada\_545](#): > > Do you live in your car? Love the question ! When I do leave the house during winter, I actually stay inside of the car until I return home. I go for joyrides. But man, out there is so cold! ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [December 1, 2023, 1:08pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/9 "2023-12-01T13:08:35Z")
Idling consumes very little gas. It appears that you have a choice: save a minimal amount of gasoline with your manual stop/start system and experience charging problems or just let the car run and have a properly charged battery. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [December 1, 2023, 1:15pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/10 "2023-12-01T13:15:31Z")
In addition to running-down the battery, the OP’s stop-start-stop routine is also putting more wear and tear on the starter. The HVAC system has a temperature control–and likely it is automatic–so simply setting the temp for one’s own comfort level should be all that is needed to have a cabin temperature that is appropriate. ---
**Author:** ![LoudThunder](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/loudthunder/32/27769_2.png) [@LoudThunder](https://community.cartalk.com/u/LoudThunder)\ **Post date:** [December 1, 2023, 1:45pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/11 "2023-12-01T13:45:25Z")
> [@Clueless33](#): > > I go for joyrides. Get a coat, a hat, and wear gloves. The blanket may get tangled up in your feet. Your remark that you go for joyrides seem so contrary to your desire to “save gas.” If you really want to save gas, only drive downhill or with a tail wind… L 😁 L . . . ---
**Author:** ![Purebred](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/purebred/32/46796_2.png) [@Purebred](https://community.cartalk.com/u/Purebred)\ **Post date:** [December 1, 2023, 1:50pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/12 "2023-12-01T13:50:35Z")
Your start/stop method is hard on your car, period. In addition to the above comments, follow the severe service requirements in your owners manual. How long, time and miles, are your joy rides? I don’t know how much a starter or alternator replacement is for you car, but I am sure it is much, much more than consuming $5.00 worth of car over the course of a **year** the car may be spent during periods idling. Just my opinion, I would not trust **any** remote start added on by **anyone**. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [December 1, 2023, 2:32pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/13 "2023-12-01T14:32:15Z")
> [@Purebred](#): > > I don’t know how much a starter or alternator replacement is for you car, but I am sure it is much, much more than consuming $5.00 worth of car over the course of a **year** the car may be spent during periods idling. +1 If the OP winds-up wearing out his starter, replacement will likely cost ~$500 (parts + labor). > [@Purebred](#): > > I would not trust **any** remote start added on by **anyone** +1 Even a genuine Toyota remote starter, which was installed at the dealership on my friend’s Rav-4, was problematic. I would only trust a remote starter that was added to a vehicle at the factory, at the time that it was built. ---
**Author:** ![lion9car](https://avatars.discourse-cdn.com/v4/letter/l/59ef9b/32.png) [@lion9car](https://community.cartalk.com/u/lion9car)\ **Post date:** [December 1, 2023, 6:09pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/14 "2023-12-01T18:09:58Z")
> [@Clueless33](#): > > When I’m idling, I turn the car on to keep the inside warm then turn the car off when I feel warm enough, then turn back the car on when I am feeling chilly again. In today’s cars, idling barely adds any charge back to the battery, so you’re depleting your battery every time you do this. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [December 1, 2023, 6:45pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/15 "2023-12-01T18:45:35Z")
> [@lion9car](#): > > In today’s cars, idling barely adds any charge back to the battery, so you’re depleting your battery every time you do this. Today’s cars have BMS’s . This makes sure the battery remains properly charged under all engine operating conditions. > **[What does a battery current sensor do - heyi](https://www.heyiele.com/faqs/what-does-a-battery-current-sensor-do/)** > > The battery current sensor is an amp clamp that measures current flow into and out of the battery. The current sensor then translates flow into a variable duty cycle signal. The sensor then sends this variable duty cycle to the BCM to indicate... Tester ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 1, 2023, 9:10pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/16 "2023-12-01T21:10:19Z")
> [@Clueless33](#): > > I’ve been turning off and on the car more frequently than should. For example: When I’m idling, I turn the car on to keep the inside warm then turn the car off when I feel warm enough, then turn back the car on when I am feeling chilly again. There’s absolutely nothing wrong w/doing that.It’s your car, you can turn it on and off whenever you like. I did that many times in the winter when I lived at a Colorado ski resort, never caused any problems w/my vehicles. Perhaps the difference is that I drove the vehicles nearly every day for 15-50 miles, which gave ample opportunity to recharge the battery. If you aren’t driving your Lexus very often, you may need to recharge the battery periodically overnight with a shop battery charger or w/a trickle charger. Idling isn’t very effective at charging the battery, in fact the battery may actually be discharging during idling. The charging rate is proportional to the engine rpm. At idle your alternator’s charging rate might only be 30 amps, and the electronics laden car is using 40 amps just to idle. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [December 1, 2023, 9:37pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/17 "2023-12-01T21:37:38Z")
The alternator has a capable output of 80 amps at idle speed, this is enough to shorten the life of a battery. We don’t need to drive at highway speeds to generate enough current to charge the battery. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 1, 2023, 10:16pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/18 "2023-12-01T22:16:43Z")
> [@Nevada\_545](#): > > The alternator has a capable output of 80 amps at idle speed, I’m not finding an idle rpm max alternator current output spec for a 2018 IS-300… The chart in the link below shows it varies greatly by the specific alternator. If the car uses a 170 amp rated alternator and a 2:1 ratio, 80 amps looks reasonable at 750 rpm. Although the output drops to zero at 500 rpm. OP, if your car has an alternator output gauge, you might could make an estimate… First step, turn on the headlights on bright at warm idle, what does the gauge show? > **[Alternator Output Curves - Balmar](https://balmar.net/balmar-technology/alternator-output-curves/)** > > Alternator Output Curves Alternator output is dependent on a number of factors:  battery condition and capacity, wire size, engine horsepower and engine RPM, battery temperature and alternator temperature.  Of these factors, alternator... ---
**Author:** ![Clueless33](https://avatars.discourse-cdn.com/v4/letter/c/dbc845/32.png) [@Clueless33](https://community.cartalk.com/u/Clueless33)\ **Post date:** [December 1, 2023, 10:31pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/19 "2023-12-01T22:31:51Z")
I took my car today to auto zone for them to check up on the battery’s health and all was good. Battery was in good condition. The guy said my problem could be alternator related. I asked if he thought turning the engine off and on too much would hurt the car and he said not to his knowledge but would recommend me talking to Lexus. The problem hasn’t occurred since. And I made an appointment with the dealer already but now thinking I should cancel ??? Maybe I should wait to see if the message comes on again before taking the issue seriously ? What do you all think ? ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 1, 2023, 10:38pm UTC](https://community.cartalk.com/t/charging-system-malfunction/193940/20 "2023-12-01T22:38:08Z")
I found this link for a 2016 Lexus IS300 alternator. While capable of up to 240 amps at higher rpms, the output seems to be less than 50 amps at 750 rpm. [https://www.tucsonalternator.com/product/1006264/2016-Lexus-IS300-Base-3.5L-V6-Alternator/0-GB/](https://www.tucsonalternator.com/product/1006264/2016-Lexus-IS300-Base-3.5L-V6-Alternator/0-GB/) > [@Clueless33](#): > > What do you all think ? Me, I’d probably just drive the car more often or recharge the battery once in a while using my shop battery charger. And turn the car on and off when I wanted to. Then monitor the situation. In any event, you’ll almost certainly get better results at a Lexus dealership than a retail parts store. BTW, I was recharging my Corolla’s battery using a shop battery charger just this morning, common routine maintenance for a car not driven frequently. I like to keep the Corolla’s battery fully charged b/c it reduces wear and tear on the starter motor. [Next page](https://community.cartalk.com/t/charging-system-malfunction/193940.md?page=2)