12V battery voltage drops, is it normal???
Thread Starter
Pole Position
Joined: Sep 2019
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From: CA
12V battery voltage drops, is it normal???
hi All,
I found my vehicle 12V battery was low at 11.45V on the NX350h so I trickle charged it. Last reading was at 12.65V yesterday as if 11pm.
Today, I looked and it's down to 12.43V at 8am.
Is that normal to lose that amount over night?
I saw some other videos including the ones on youtube from LSFT but not sure if there's an issue on my vehicle.
I found my vehicle 12V battery was low at 11.45V on the NX350h so I trickle charged it. Last reading was at 12.65V yesterday as if 11pm.
Today, I looked and it's down to 12.43V at 8am.
Is that normal to lose that amount over night?
I saw some other videos including the ones on youtube from LSFT but not sure if there's an issue on my vehicle.
Racer
Joined: Apr 2015
Posts: 1,717
Likes: 806
From: Ontario
Mine typically drops about 0.2V between that timeframe. Which it seems to be very similar on yours as well. That is what I have seen, but typically it drops a little and not a long, but around 6am, it seems to do something and drops a bit more during that timeframe.
Thread Starter
Pole Position
Joined: Sep 2019
Posts: 2,175
Likes: 443
From: CA
Thanks for chiming in on it.
Intermediate
Joined: Oct 2023
Posts: 438
Likes: 341
From: CA
hi All,
I found my vehicle 12V battery was low at 11.45V on the NX350h so I trickle charged it. Last reading was at 12.65V yesterday as if 11pm.
Today, I looked and it's down to 12.43V at 8am.
Is that normal to lose that amount over night?
I saw some other videos including the ones on youtube from LSFT but not sure if there's an issue on my vehicle.
I found my vehicle 12V battery was low at 11.45V on the NX350h so I trickle charged it. Last reading was at 12.65V yesterday as if 11pm.
Today, I looked and it's down to 12.43V at 8am.
Is that normal to lose that amount over night?
I saw some other videos including the ones on youtube from LSFT but not sure if there's an issue on my vehicle.
Pole Position
Joined: Dec 2012
Posts: 2,129
Likes: 947
From: Toronto, ON
Just measured mine for licks and giggles. 11.32V after a full 4 days in sleeping beauty mode. It has sat longer without issues and my battery actually has to crank.
But voltage itself really isn't the best measure of battery health or charge function. I think its normal for a battery to show a high voltage right after charging that isn't necessarily an indicator of state of charge or health without a proper load test. I've heard the term "surface charge" which I believe refers to a kind of heightened voltage level that is a residual effect of charging that can dissipate very quickly. Voltage can show on the higher side of things, but have little capacity and fail a load test. Voltage can show a bit on the low side but still have significant capacity to provide high current. A load test (or perhaps a smart charger test) is the best way of determining battery health. A current draw test (putting an amp meter between battery post and cable) is a better way of determining the amount of parasitic draw. I think most cars will draw 30 to 50 mA just sitting, 50 to 70 a bit on the high side and above that is likely to cause issues (provided something hasn't woken up, like the EVAP system test as example).
But voltage itself really isn't the best measure of battery health or charge function. I think its normal for a battery to show a high voltage right after charging that isn't necessarily an indicator of state of charge or health without a proper load test. I've heard the term "surface charge" which I believe refers to a kind of heightened voltage level that is a residual effect of charging that can dissipate very quickly. Voltage can show on the higher side of things, but have little capacity and fail a load test. Voltage can show a bit on the low side but still have significant capacity to provide high current. A load test (or perhaps a smart charger test) is the best way of determining battery health. A current draw test (putting an amp meter between battery post and cable) is a better way of determining the amount of parasitic draw. I think most cars will draw 30 to 50 mA just sitting, 50 to 70 a bit on the high side and above that is likely to cause issues (provided something hasn't woken up, like the EVAP system test as example).
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Racer
Joined: Apr 2015
Posts: 1,717
Likes: 806
From: Ontario
There is no alternator. It is charge via the DC to DC converter. The DC to DC Converter in Ready Mode will supply current to the 12V and charge it.
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Thread Starter
Pole Position
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From: CA
Racer
Joined: Apr 2015
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From: Ontario
Pole Position
Joined: Aug 2011
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physics/electrical - load resistance or impedance causes voltage drop. V=I*R (less phase shift) unloaded battery, full voltage 
Just what are the forum "Electrical Engineers" trying to measure?
YMMV,
MisCow3
Just what are the forum "Electrical Engineers" trying to measure?YMMV,
MisCow3
Thread Starter
Pole Position
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From: CA
Thread Starter
Pole Position
Joined: Sep 2019
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From: CA
I'm an EE so I know about Ohm's Law.
Pole Position
Joined: Aug 2011
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... and by the way most forum members are not BSEEs, much less understand Ohm's law. Even with Ohm's law it is nearly impossible to get correct measurements while a battery is still under load , with a load that varies without much rhyme or reason.YMMV,
MidCow3
Thread Starter
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From: CA
It's those pesky resistance bugs connected to the battery terminals that draw parasite voltage and current. ... and by the way most forum members are not BSEEs, much less understand Ohm's law. Even with Ohm's law it is nearly impossible to get correct measurements while a battery is still under load , with a load that varies without much rhyme or reason.
YMMV,
MidCow3
... and by the way most forum members are not BSEEs, much less understand Ohm's law. Even with Ohm's law it is nearly impossible to get correct measurements while a battery is still under load , with a load that varies without much rhyme or reason.YMMV,
MidCow3