Do External Battery Packs Charge w/ Accessory Power On (But Engine Off)?

[AEMontoya]

Do external battery packs sold to power dashcams charge and draw current from the car's starter battery ONLY when the engine is running and the alternator is supplying ~14.6 V? Or do external battery packs begin charging and drawing 7-10 A of current from the main battery simply when accessories are turned on, regardless of whether the engine is turned on or not?

I'd hate to think that if I wanted to charge my cell phone via the 12V socket, or needed to fill up with an air compressor after patching a tire, that I'd end up draining my starter battery due to an external battery pack pulling a bunch of current. Obviously, I could avoid the issue by starting the engine every time I wanted to power an onboard accessory; but, is that really practical? I assume that these external battery packs sold for dashcams have a BMS that only allows them to charge when they see ~14.6 V from an alternator, but no one, including the dashcam battery manufacturers seems to have an answer. Strange ...

 

[ly-70mai]

Charging only above 14.6V will cause many problems. The battery condition of each vehicle is different, and other more complete logic may be needed to solve this problem.

 

[AEMontoya]

Charging only above 14.6V will cause many problems. The battery condition of each vehicle is different, and other more complete logic may be needed to solve this problem.

I'm not sure how your reply relates to the issue, to be honest. I'm wondering simply if external dashcam battery packs will begin charging from the starter battery when the car is put into accessory mode, but before the engine actually starts.

 

[Panzer Platform]

Do external battery packs sold to power dashcams charge and draw current from the car's starter battery ONLY when the engine is running and the alternator is supplying ~14.6 V? Or do external battery packs begin charging and drawing 7-10 A of current from the main battery simply when accessories are turned on, regardless of whether the engine is turned on or not?

It depends on how you wire the battery pack to your car.
You also have the option to stop the battery pack from charging by selecting “charging stop” with the smartphone APP.

 

[AEMontoya]

Interesting. I didn't know some battery packs have that feature via app. That's nice.

I guess I should have been more specific to my scenario. The question assumes that the external battery pack is hardwired to the car's fuse box via an accessory fuse, such that the battery pack sees voltage only when the car is put in accessory mode. It is further assumed that when the battery pack sees this voltage, it is already turned on.

Of course, one could always turn the battery pack off via button, via any available app, by disconnecting from the fuse box, ... this would certainly prevent the dashcam from charging and draining the starter battery.

However, I figured that when the vehicle's engine is actually started, and the alternator begins charging the starter battery and exposing whatever other electronics in the car's BMS to the higher voltage, this event would be potentially detected by the battery management system of the dashcam battery pack through the accessory fuse connection such that the battery pack would only begin charging at that moment (e.g., I'm guessing there'd perhaps be a voltage fluctuation detected upon engine start). This would be a good design and excellent benefit, because it would allow for use of other accessory devices, such as a cell phone charger plugged into a 12 V socket, without the fear of the battery pack draining the car's starter battery or the need to make sure the battery pack is turned off manually or by other means.

I ask all this because I am considering hardwiring an iVolt mini battery pack via accessory fuse and stashing it behind the dash, where it cannot be easily accessed (space is very tight in my vehicle--no room in glove box, no room under seats, ...). This placement would prevent me from being able to turn it on/off manually, and this battery pack cannot be turned on/off via an app. Sometimes I like to sit in my car without startimg the engine while keeping the car in accessory mode so that I can have power from a 12 V socket for a period of time. I would not want the dashcam battery pack to simultaneously be pulling 7-10 A from the starter battery during this time. Of course, I can install an inline switch that hangs down in the passenger footwell and such, etc. But, of course, non of this poses an issue if the dashcam battery pack only begins charging when the engine is turned on. The specs for the iVolt mini indicate that it begins charging when "the car is turned on/running". This is ambiguous to me, but does suggest to me that the engine must be running for charging to occur. I called Thinkware for clarification, but they could not give me an answer and say that they will need to do further testing. I noticed elsewhere in this forum, that an individual testing a different model of dashcam battery pack indicated that it only begins charging when it detects a voltage equivalent to what an alternator puts out (~14.6). This is why I seek the answer to my question.

I would think that this concern of mine would be a common one for those who choose to hardwire dashcams via accessory fuse port, given the relatively high amp draw of these battery packs during charging, the serious demands that are often already placed on starter batteries in many of today's electronically sophisticated vehicles, ...

 

[ly-70mai]

Interesting. I didn't know some battery packs have that feature via app. That's nice.

I guess I should have been more specific to my scenario. The question assumes that the external battery pack is hardwired to the car's fuse box via an accessory fuse, such that the battery pack sees voltage only when the car is put in accessory mode. It is further assumed that when the battery pack sees this voltage, it is already turned on.

Of course, one could always turn the battery pack off via button, via any available app, by disconnecting from the fuse box, ... this would certainly prevent the dashcam from charging and draining the starter battery.

However, I figured that when the vehicle's engine is actually started, and the alternator begins charging the starter battery and exposing whatever other electronics in the car's BMS to the higher voltage, this event would be potentially detected by the battery management system of the dashcam battery pack through the accessory fuse connection such that the battery pack would only begin charging at that moment (e.g., I'm guessing there'd perhaps be a voltage fluctuation detected upon engine start). This would be a good design and excellent benefit, because it would allow for use of other accessory devices, such as a cell phone charger plugged into a 12 V socket, without the fear of the battery pack draining the car's starter battery or the need to make sure the battery pack is turned off manually or by other means.

I ask all this because I am considering hardwiring an iVolt mini battery pack via accessory fuse and stashing it behind the dash, where it cannot be easily accessed (space is very tight in my vehicle--no room in glove box, no room under seats, ...). This placement would prevent me from being able to turn it on/off manually, and this battery pack cannot be turned on/off via an app. Sometimes I like to sit in my car without startimg the engine while keeping the car in accessory mode so that I can have power from a 12 V socket for a period of time. I would not want the dashcam battery pack to simultaneously be pulling 7-10 A from the starter battery during this time. Of course, I can install an inline switch that hangs down in the passenger footwell and such, etc. But, of course, non of this poses an issue if the dashcam battery pack only begins charging when the engine is turned on. The specs for the iVolt mini indicate that it begins charging when "the car is turned on/running". This is ambiguous to me, but does suggest to me that the engine must be running for charging to occur. I called Thinkware for clarification, but they could not give me an answer and say that they will need to do further testing. I noticed elsewhere in this forum, that an individual testing a different model of dashcam battery pack indicated that it only begins charging when it detects a voltage equivalent to what an alternator puts out (~14.6). This is why I seek the answer to my question.

I would think that this concern of mine would be a common one for those who choose to hardwire dashcams via accessory fuse port, given the relatively high amp draw of these battery packs during charging, the serious demands that are often already placed on starter batteries in many of today's electronically sophisticated vehicles, ...

Haha, sorry, I was actually wondering what functionality you need from a battery pack. In many cars, when the engine is not started but the key is turned to the ACC position, the central control, radio, and cigarette lighter are powered, so most dash cam battery packs will be charged normally at this time. Among the several battery packs I have used and tested, as long as the power supply voltage is not lower than 11V-12V, they can be charged. I was thinking about the same problem as you recently. At first, my idea was to detect voltage fluctuations to determine whether there was an engine start event. However, my concern was that the voltage fluctuations when the batteries of different vehicles are ignited may not be consistent. Maybe I cannot simply use 14.6 V such a threshold to judge. So I was wondering if I could detect the voltage drop trend for a period of time after starting charging. Maybe this can also be judged?

 

[Panzer Platform]

If you only want your dash cam battery pack to charge while your car’s engine is running, you can wire it up with a relay.
Connect the signal / trigger wire of the relay to a power source that is only energized when the car’s engine is running.

 

[ly-70mai]

If you only want your dash cam battery pack to charge while your car’s engine is running, you can wire it up with a relay.
Connect the signal / trigger wire of the relay to a power source that is only energized when the car’s engine is running.

Perhaps, if the battery pack provides a Type-c fast charging port, this "habits of not starting the car engine but still needing to charge the mobile phone" can be changed?

 

[rcg530]

The various dash camera battery packs I have in my dash camera test car will start charging when the input power to the battery pack is turned on (Thinkware iVolt Xtra BAB-95 is the exception). I have the following battery packs in my car: Thinkware iVolt Mini BAB-50, BlackVue B-112, Cellink B, BlackboxMyCar PowerCell 8, Thinkware iVolt Xtra BAB-95. The BAB-95 is connected to constant vehicle battery power and it starts charging when 12V power is provided on its "ACC IN" (green) wire. When I'm working on rearranging dash cameras in my car, I will often have the ignition switch in the accessory position/mode (not the RUN position/mode and no engine running) to allow the dash cameras to power up and function while I'm adjusting the lens aim. I use a car battery maintainer while my vehicle is parked for multiple days and while I have one of these dash camera installation sessions. One of the dash camera battery packs in my car's trunk (I believe it's the PowerCell 8) will "beep" periodically indicating that the input charging voltage is too low (it will be in the very low 12 volt range even with the car battery maintainer active with all of the battery packs attempting to charge themselves).

There is a minimum voltage level most dash camera battery packs will require before the dash camera battery pack's BMS will "start" their charging cycle and that is usually in the mid 12V range. I've never tested that minimum voltage level for any of the battery packs that I've used. They do not wait to see an input voltage level of 14.6V. Keep in mind, your vehicle's charging system is not always at 14.6V while the engine is running. It depends on the logic in the vehicle's engine/powertrain control module (ECM/PCM) on how it detects the load on the vehicle's electrical system and what the vehicle's battery charge level is at that time. My car's alternator will be commanded by the ECM to output voltage in the 14.8V down to the 12.3V range depending on the engine load and the current amp load on the car's battery. My car's ECM monitors the amp load on the car battery using an amp clamp around the negative battery cable connected the my car's battery in the trunk.

If you want to restrict the Thinkware iVolt Mini BAB-50 to receiving input charging power only when the engine is running, you could follow @Panzer Platform's suggestion and locate a power circuit that is only provided power while the ignition switch (or push button system) is in the "RUN" position/mode. This will not mean it has power only when the engine is running, but it will be powered only when the ignition switch or push button system is in the engine "RUN" mode. This will allow you to place the ignition switch/push button system into "Accessory" mode and not supply power to the battery pack or control side of a relay powering the battery pack (if using a relay to provide power to the charging input of the dash camera battery pack - my preferred method). You will have to look for a fuse box fuse socket that only receives power in "RUN" mode.

 

[AEMontoya]

Thank you very much! You answered my question, and then some.

Basically, for all those out there who purchased a dedicated dashcam battery pack under the sales pitch that it would protect their starter battery and/or avoid a car that won't start: Be aware that if you use conventional hardwiring, as the manufacturers recommend, you put yourself in the position of actually harming your starter battery and/or instigating a car that doesn't start if you don't power your vehicle's engine, turn off your battery pack, or connect a battery charger when using accessory ports such as the 12 V sockets. Also, if you have one of the many vehicles on the road nowadays that has auto start-stop, everytime you're at a red light and the engine turns off, the dashcam battery pack will be pulling ~10 A.

Given the ambiguous language I've encountered as well as the so-called inability of manufacturers and vendors to give me an answer, I can't help but to feel that the above is a bit of a dirty little secret that vendors and manufacturers don't want you to know. Oh well, welcome to every industry out there, lol. Do thy research always ... Assume guilt, unless proven otherwise

 

[Panzer Platform]

The various dash camera battery packs I have in my dash camera test car will start charging when the input power to the battery pack is turned on (Thinkware iVolt Xtra BAB-95 is the exception). I have the following battery packs in my car: Thinkware iVolt Mini BAB-50, BlackVue B-112, Cellink B, BlackboxMyCar PowerCell 8, Thinkware iVolt Xtra BAB-95. The BAB-95 is connected to constant vehicle battery power and it starts charging when 12V power is provided on its "ACC IN" (green) wire. When I'm working on rearranging dash cameras in my car, I will often have the ignition switch in the accessory position/mode (not the RUN position/mode and no engine running) to allow the dash cameras to power up and function while I'm adjusting the lens aim. I use a car battery maintainer while my vehicle is parked for multiple days and while I have one of these dash camera installation sessions. One of the dash camera battery packs in my car's trunk (I believe it's the PowerCell 8) will "beep" periodically indicating that the input charging voltage is too low (it will be in the very low 12 volt range even with the car battery maintainer active with all of the battery packs attempting to charge themselves).

There is a minimum voltage level most dash camera battery packs will require before the dash camera battery pack's BMS will "start" their charging cycle and that is usually in the mid 12V range. I've never tested that minimum voltage level for any of the battery packs that I've used. They do not wait to see an input voltage level of 14.6V. Keep in mind, your vehicle's charging system is not always at 14.6V while the engine is running. It depends on the logic in the vehicle's engine/powertrain control module (ECM/PCM) on how it detects the load on the vehicle's electrical system and what the vehicle's battery charge level is at that time. My car's alternator will be commanded by the ECM to output voltage in the 14.8V down to the 12.3V range depending on the engine load and the current amp load on the car's battery. My car's ECM monitors the amp load on the car battery using an amp clamp around the negative battery cable connected the my car's battery in the trunk.

If you want to restrict the Thinkware iVolt Mini BAB-50 to receiving input charging power only when the engine is running, you could follow @Panzer Platform's suggestion and locate a power circuit that is only provided power while the ignition switch (or push button system) is in the "RUN" position/mode. This will not mean it has power only when the engine is running, but it will be powered only when the ignition switch or push button system is in the engine "RUN" mode. This will allow you to place the ignition switch/push button system into "Accessory" mode and not supply power to the battery pack or control side of a relay powering the battery pack (if using a relay to provide power to the charging input of the dash camera battery pack - my preferred method). You will have to look for a fuse box fuse socket that only receives power in "RUN" mode.

About time you showed up. lol

 

[Panzer Platform]

@AEMontoya
If you want to simplify the wiring, and not use a relay, you can use the Thinkware BAB-95 instead of the iVolt Mini BAB-50, (see attached screenshot).
Just connect the ACC Power Signal Input wire to whatever power source is energized when the engine is running.
Here are the two best reviews of the BAB-95;

Here is the worst dash cam battery pack review ever. lol

 

[AEMontoya]

Man ... this whole issue is still elluding my understanding. I just called BlackBoxMyCar, and the rep I spoke with told me that their installers always use accessory fuse ports that are only powered when the engine is running (I think he essentially means when in "run" mode). He said that in this way if a car has auto start-stop, the battery pack will not charge when in stop mode, and it will begin charging again once the engine is re-started. Furthermore, he said that the battery pack will not charge itself when parked and in accessory mode.

If the above is true, how come all of the instructions I see for installation of dashcams and battery packs simply specify to wire to an accessory port (aka "switch fuse" port)? There is no mention of using a fuse port that is only powered when in "Run" mode, just "accessory mode". I mean, unless you are like rcg530 and want to re-adjust and test your dashcams while in accessory mode with the engine turned off and a battery maintainer hooked up, why would anyone want to use an "accessory" fuse port as opposed to a "run" fuse port? From my testing of fuses in the passenger footwell of my 2019 GLA 45, I'm not even sure there is a "run" fuse port, just a bunch of always on fuse ports and a few accessory fuse ports. Indeed, from what I see online, there seems to be a dearth of others searching for such "run" fuse ports, let alone those who actually manage to find one. I've seen some different references to fuse ports so far. Perhaps there are three main categories: 1) accessory, 2) ignition, 3) batt +? A lot of the time there will be an ambiguous reference to "ACC/Ignition" fuse ports. For MBZ vehicles with push button start in general, not necessarily my model, this is how mercedes says pushing the button will work:



So, I guess I'm just looking for a fuse port that gets power upon the second push (no foot on brake). Plus, the fuse port needs to be rated for a 20 A fuse. If I recall correctly, all of the fuses I tested in the passenger footwell were either always on or powered when in accessory mode (one push + no foot on brake). I guess that just leaves the fuse box under the hood, meaning that if I do find an appropriate fuse, I'll need to run the wire through a grommet/hole in the firewall. How common are such complications?

And regarding the difference between how the Thinkware iVolt Xtra is triggered to begin charging, versus the iVol mini and other brands/models of battery packs, how do the below wiring diagram differences play a role in whether I'd need to use a realy or not? (iVolt Xtra is image 1, iVolt Mini is image 2.) It seems to me that once power is received via a run/accessory fuse, in either case, the battery would be triggered to begin charging, regardless of whether I used a relay or not.

 

[GPak]

That “Push” procedure is likely similar for most cars, certainly for my 2012 GC Jeep.

In my Jeep, when engine is running, No-Load voltage in electrical system is about 14.45V.
When car is on ACC (either one push or second push, and engine is not running), No-Load “resting” voltage in electrical system is about 12.45V, I guess it depends on health of the car battery and state of the charge, but "resting voltage" never going to be say more than 13.0V, even for AGM battery.

So for the price they are charging for these dedicated batteries, they could probably add some type of No-Load voltage sensor in sequence, to activate charger, when it senses above say 13.5V, for example.

At list, low voltage protection could be incorporated into charger to protect car Battery, when charging voltage gets to, say 12V for example, while on ACC and engine is not running. With engine/alternator running, it should not really go that low.

For example in my LTO battery project, I use cheap, just $15, CC-CV, 20A, 1200W boost converter/charger and yet it has the battery low voltage protection.
I set it to 12V, and when voltage comes close to about 12.2V it will start to lower charging current and will eventually stop charging at about 12V. Not very precise but at list some protection.
https://www.amazon.com/gp/B0CGTBMNJQ

 

[AEMontoya]

That “Push” procedure is likely similar for most cars, certainly for my 2012 GC Jeep.

In my Jeep, when engine is running, No-Load voltage in electrical system is about 14.45V.
When car is on ACC (either one push or second push, and engine is not running), No-Load “resting” voltage in electrical system is about 12.45V, I guess it depends on health of the car battery and state of the charge, but "resting voltage" never going to be say more than 13.0V, even for AGM battery.

So for the price they are charging for these dedicated batteries, they could probably add some type of No-Load voltage sensor in sequence, to activate charger, when it senses above say 13.5V, for example.

At list, low voltage protection could be incorporated into charger to protect car Battery, when charging voltage gets to, say 12V for example, while on ACC and engine is not running. With engine/alternator running, it should not really go that low.

For example in my LTO battery project, I use cheap, just $15, CC-CV, 20A, 1200W boost converter/charger and yet it has the battery low voltage protection.
I set it to 12V, and when voltage comes close to about 12.2V it will start to lower charging current and will eventually stop charging at about 12V. Not very precise but at list some protection.
https://www.amazon.com/gp/B0CGTBMNJQ

Interesting. Everything you say makes sense to me. I do vaguely remember the rep at Blackbox My Car saying something about how most of the dashcam battery packs do have a BMS that prevents charging when they see less than 12 or so volts. I have a variable output OBD reader in my vehicle that I've set to give me the voltage that my battery sees whenever I'm driving around and parked. Even after topping off my 9-month-old AGM battery, the lowest voltage the battery sees while the engine is running is 13.5 V. So, I agree a sensor that inititiates charging somewhere between 13 and 13.5 V seems like it could be a good idea.

 

[AEMontoya]

BTW, to anyone reading this post: Contrary to what I was told by Blackbox My Car in Post 13, I have since determined that dashcam battery packs will in fact draw current from the starter battery when in auto start-stop mode. This was confirmed by a technician at Blackbox My Car as well as a pro installer I spoke with at a local shop. It also just makes sense, since it's unlikely that a vehicle's "run" mode will completely turn off such that the car enters accessory mode only, if this makes sense. I have also found several instances online of individuals whose auto start-stop systems did not work whenever they had a dashcam battery pack in use. The thinking there was that the current draw and voltage sag caused by the battery pack "tricked" the car's native BMS into thinking that the starter battery's state of charge was less than it really was, thereby causing the auto start-stop feature to shutoff so as to protect the "compromised" battery.

 

[AEMontoya]

This device seems like it could function to turn on and off a dedicated dashcam battery pack based on turning on and off the engine:

Voltage Sensing Relay 12V / 24V 80A

The ProCon VSR is the next grade up from the ProCon IF. The VSR has 12 Volt or 24 Volt automatic voltage selection and does not require an ignition feed. When the voltage of battery 1 (e.g. starter battery) exceeds 13.3V the ProCon VSR assumes that the charging device (alternator / battery...

www.intellitecmv.com

 

[AEMontoya]

Here's another voltage sensitive relay that is much more compact and less expensive that seems like it would work just fine. I suppose it could be connected directly to the battery ad installed within the engine bay (it has a good water resistance rating), and its power lead could be routed through a firewall grommet. Once inside the cabin, a 20A inline fuse could then be put between the relay's incoming power lead and the ACC lead of the dashcam battery pack. I think that some, if not all, of these relays might make a slight clicking noise when the cut in voltage is reached and the relay latches. This would be another good reason to keep the relay in the engine bay, where the sound would unlikely be heard from within the cabin. The power lead that enters the cabin could also have multiple bullet connectors soldered on so that different devices that one would want powered only when the engine is running could also be powered.

https://www.ebay.com/itm/204139521236

 

[AEMontoya]

After reading about voltage sensing relays (VSR) like those shown above, I see some mention that they will not work with so-called "smart alternators", which change charging voltage dynamically based on the car's overall electrical system condition. My vehicle happens to have a smart altenator (there's a rectangular sensor on the negative terminal of the starter battery that indicates this), but I have never seen the voltage of the battery go outside of the range of 13.5 V to 14.9 V (I have a digital gauge inside my vehicle that displays the battery voltage, and I've watched it while I drive, including between having a fully charged battery [when it reads around 13.5 V] to having a nearly fully discharged battery [when it reads up to 14.9 V]). Since 13.5 V is greater than the 13.3 cut-in voltage of most of the VSRs I see online, I don't see why a smart alternator--at least not mine--would be a problem.




Here is another indication that a VSR won't work with a smart alternator:


A bit more on the matter:

 

[AEMontoya]

Apparently, since VSRs are not supposed to work with smart alternators, a DC-DC charger such as the one below is supposed to be used in its place. These are designed to provide a stage-related voltage/amperage output based on the type of battery they are charging and do not rely simply on input voltage from the starter battery/alternator to determine when to switch on and off. One of the potential drawbacks I see in these is that dashcam battery packs already have a built-in battery management system; so, I'm not sure how the staged output of these DC-DC chargers would play with that, although it does seem that they are highly programmable.