BM2 bluetooth 12V battery monitor review (A must have accessory for any EV or ICE vehicle)

[@2011ppower]

I carry an rechargeable emergency starter . Had to use it once on my Ioniq when the 12volt lost charge for no apparent reason. It worked fine and haven't had a problem since🤞

[@GoGreenAutos]

Yes many carry a booster/jump pack. So did we initially when we got the 38kWh Ioniq, due to the known battery issues, but don't bother now and rely on this bluetooth battery monitor instead. When you can see the charging and discharging patterns, it soon gives you the confidence that its working fine and there's no battery drain. One day I may enable the Bluelink app and see how it then differs.

[@kwrzesien17]

I carry a battery pack booster in every car with the newest always in the most troublesome car. I’ve saved myself five times and just as many other people!

[@kwrzesien17]

What ever I used to do with my Leaf would leave me with a dead 12V and a full main pack in the mornings. I believe it was a combination of using the built-in charge timer and having zero cell signal in my garage for the 3G telematics. 3G went away and I had the unit disconnected and I switched to using the 2/4/6/8 hour delay charging on my EVSE.

[@kwrzesien17]

Thinking I’ll install this battery device on my spare gas car since it rarely gets driven!

[@AndyC2_]

@@GoGreenAutosHi Matt, reading your comment I wondered - did you ever start using Bluelink and monitor what happened with the 12v battery ?

[@Hitstirrer]

According to Hyundai techs the negative lead to the BM2 should be connected to the chassis and not the 12v battery negative terminal. Apparently there is a sensor on the terminal and fixing there could confuse the car's computers. So - red lead to positive 12v battery terminal and black lead to a nearby chassis screw.

[@colinphillipson4830]

Thanks Matt, I've posted this on the Hyundai Ioniq Electric UK Owners Group. What I would add is instead of leaving the car safely powered up in full drive mode with the 38kWh is to turn on the Utility mode which is much safer being left and still charges the 12v battery. 👍

[@judebrown4103]

Hi Colin, is Utility mode what happens if I turn on the car while at a rapid charger? Or is it something specific I should search for on the screen...complete non-techy person here sorry for ignorance!

[@colinphillipson4830]

@@judebrown4103 Utility mode is a specific function, it could be also classed as a "camping mode". All the power needed is only from the main traction battery thus saving the 12v battery for all the 12v system components. The option is only visible in the Drivers dash menu system under Convenience when in full drive mode and in park. Select the option with Yes and the car then applies the hand brake. To end this you have to start the car as normal.

[@judebrown4103]

@@colinphillipson4830 excellent, thank you so much. 👍

[@GoGreenAutos]

Hi Colin. Yes I saw you'd posted this, thanks. Yes we have the Utility mode on too, but others have found this still isn't stopping battery draining on the 38kWh models.

[@festeradams3972]

Nicely done. I've got a Nissan Leaf here across the pond. A 22' SV+, and the main battery is in great condition. Not so the OEM 12v. A few days ago, came out to make a quick trip to the local grocer, and was greeted by an amazing display of dash lights and relay clicks! Taking a couple of minutes to compose myself, after having a certain suspicion, I brought out my trusty fluke DMM and tested the 12 V. A very insufficient 6.8vdc appeared on the display and removed all doubt about the cause. Taking the battery out of circuit and replacing it with a small handheld 12 V lithium pack, restored all to wellness after the car is computers thought about it for a couple of minutes. All voltages then appeared nominal. Replace the OEM battery with an Optima yellow top 12 V, all has been well and a few days since.I suspect strongly that the OEM had developed a short across at least a couple of the 2v internal cells. I installed temporarily a voltage data logger, which I already had, and will use this as a permanent replacement for said temporary logger, we should give me a piece of mind at a glance.

[@MavAuto-Pete]

This is also a problem with cars with Start/Stop. The battery may have a larger crank and capacity but without a solar charger things like start stop, even cylinder deactivate won't work on VAG cars until the battery has sufficient voltage back in it. Hence MPG will go down for the first few miles.... AA 4.8V Solar charger with EOBD Connection, works well especially with your Hybrid, going on cars I've tested...

[@thathairyguy]

When my 12v died in my 38, it behaved more like a dying ICE 12v battery. It let me in the car no problem, then when I went to start it tried and got about half way through the "boops" then all the interior dash lighting flickered a lot, then I got the, "check electrical system" message on the screen and then it fully died... this device would have been handy for some advance warning for sure.

[@uberacx]

Thank you. I do carry an emergency battery starter but it is actually a better practice to check the battery voltage from time to time. Check with this gadget while the car is NOT while the car is running because the voltage will be higher when the car is running. Thank you.

[@GoGreenAutos]

The key thing with this BM2 device is that you can install it and forget about it as it monitors the battery constantly and will warn you when it gets below the thresholds you set.

[@stevechelt1]

Thanks for this. I have an Ampera which is also known for 12v battery problems.

[@GoGreenAutos]

Glad you found it useful.

[@iantaylor1172]

Not had 12v issues as yet. Got the bluelink app running since I bought the car second hand in Oct. I do have a noco gb70 jump pack in the boot that I've kept in a few cars just in case.(7yrs+) Never been required in my cars but has been used on other peoples cars. I like the bluelink software . Switch the heating on in winter as I got up was nice.

[@GoGreenAutos]

Yes, many Ioniq drivers keep a jump/boost pack in the car. We did initially, but find that these BM2 battery monitors is another great way of monitoring the battery health and catches any issues before you need the jump pack. Its better to catch the drain, rather than suffer being caught out as it will normally be first thing in the morning when you're rushing off to work.

[@royd63uk]

If the battery goes dead you cant open the boot , keep the jump starter in the glove box

[@iantaylor1172]

@@royd63uk you can fold the seat down to gain access to the boot space.

[@adeebkhan1122]

Solved. The problem is if your car battery state if charge is 20% and below. The car stops charging the 12 v battery. Example Your at 18% SOC after reaching your destination. You leave it and don't use it or you have an app link bluelink. Keep using it the battery of 12 v drops further Rac came to my rescue and updated me. Will monitor But i believe at 20 percent or less the car battery stops powering the 12v battery to save the main battery. To reslove this Keep main battery on charge after reaching destination or granny charge it via 3pin plug

[@stulop]

We have a rechargeable jumpstarter that we carried over from a previous car to our Kona Ev in case of this event. We've only used it to power the dashcam when in a dodgy looking car park and jumpstart other people's cars. It's a '21 Kona and after we had it for 6 months thumbing through the manual, yes it came with a paperback book, we discovered the car monitors the 12v battery and will connect the main battery to recharge it if needed when the car is off. There is a little orange light in the middle of the front logo when it's doing it. I had seen it on a few times but didn't know what it was. Not sure at what point this feature was introduced but the bluelink app also monitors the status of the battery along with other systems, just with an 'OK' to describe it. Though as I look at bluelink now the 12v battery reference has gone and low voltage DC/DC converter has replaced it.

[@GoGreenAutos]

Yes all the Kia & Hyundai EVs do this 12V battery charging when the vehicle is switch off and asleep. Even the 2016 Ioniqs. However, on the later vehicles, this still isn't enough and they suffer sudden 12V battery drain, even with this feature enabled.

[@sandancer5382]

Thanks Matt, I've just ordered one from your link

[@JorgeniLund]

Hi Matt and thanks for another great video. Will order a monitor now. Very interesting comment that you have never used Bluelink nor had a dead 12 volt battery. I suspect Bluelink may be a power thief. On the two occasions that my 12 volt battery has been drained, the connection from the car with Bluelink has been shaky for a long time. With monitor I could see if there is such a connection.

[@GoGreenAutos]

I'm sure you'll find the device will be very useful and hopefully will allow you to monitor the battery drain and get an idea on what's going on.

[@garrycroft4215]

I have one, it’s interesting to see on my BMW i3s that the high voltage battery charges the 12v battery even while parked off charge. So in conclusion unless the 12v fails it cannot ever be flat. This is not the case with other EVs like ioniq 5 that only charges when the car is switched on, crazy.

[@GoGreenAutos]

Good to hear. Actually the Ioniq 5 (all other Hyundai EVs) do charge the battery when the vehicle is powered off. The vehicle will wake up and do a charging session, but that still isn't enough in many cases to counteract the power drain, so they do suffer dead 12V batteries. It is strange that a vehicle that does this, suffers from more 12V battery drain issues than any other. Apparently a later BMS update does help, but I don't think it completely solves the issues.

[@garrycroft4215]

@@GoGreenAutos I also bought one of those tiny power bank jump starters, I’ve never used it but because I can’t charge at home I thought it might come in hand one day. Especially as my next EV might not be as good at keeping the 12v charged when parked up.

[@philiponsolent7232]

Useful to see it works on an I3, did you have to isolate the main battery when fitting.

[@garrycroft4215]

@@philiponsolent7232 no just slacken the 10mm bolts and slide the connections in and tighten.

[@aemarques]

Hi Garry. I also have an i3 and it looks like an interesting device. However, won't it contribute to drain the 12v battery too? 🤔

[@bothe3360]

If You want to order a similar device make shure that it provides long time monitoring. I purchased a Vgate Battery Assistant Blue Tooth 4.0 Wireless 6~20V Automotive Battery Load Tester that looks exactly the same and it doesn't offer it..

[@fredgrayson1443]

Carrying a rechargable emergency pack is all very well, but when my 2020 Ioniq PHEV's 12v battery failed, I couldn't open the boot (trunk) - because it's an electric only catch. What a design failure. (In the PHEV, the 12v battery is hidden away in the rear wing.)

[@krisvandermeulen253]

I haven't had this issue yet on my 2018 ionic... So maybe I was lucky ? Burt an interesting video which I've added to my list of ionic videos.

[@GoGreenAutos]

We never had an issue with our Ioniq 28kWh either. Some people do, but I would assume that's low mileage and low use vehicles. The Ioniq 38kWh with its telematics, app etc is catching a lot of owners out with dead 12V batteries.

[@kevancroftkc]

Purchased one , thanks for the info it's brilliant.

[@GoGreenAutos]

Great, glad you think so too.

[@frankradcliffe1374]

Watching your 12volt battery video I do not have a problem other than I noticed a blue charger light flashing on my ionic when the car was not connected to a charger, I think you mentioned a blue will flash when the big battery is topping up the 12 volt battery ? Thank you for great videos

[@GoGreenAutos]

Yes, that's correct. However, some people are finding even with this automatic charge function enabled, their 12V batteries still drain flat.

[@robertpaterson7311]

Thanks for the review. Have you ever left the car for a few days and if so did it drain the battery much ?

[@GoGreenAutos]

I've regularly left the car for 3-4 days and zero drain. I've also left it for a week and all ok. The drain from this device is so small, its not noticeable.

[@nimbuskhannk627]

If you have to be in BT range to read the instantaneous and stored data, how can it be of any use in what pertains to not finding your battery dead in the morning?...If one is triggered, how would a warning reach you, in your home, for timely corrective action?

[@GoGreenAutos]

Because you'll normally have a few days/weeks of poor performance before it completely fails, so hopefully you should get notifications as you'll be using your car or walking past your car many times before the battery completely dies and lets you down.

[@silvacrest11]

Seems a shame to not use the bluelink app when you get it for free for a few years. Like others have said, I would carry a 12v portable battery charger, still use the bluelink app and probably get the 12v battery monitor as well, cover all bases without losing functionality

[@GoGreenAutos]

We've had apps on other EVs and to be honest I get very little value from them. We didn't have an app on the previous Ioniq 28kWh and what you don't have, you don't miss. So not bothered enabling it on the 38kWh. If enabling Bluelink introduces the chance of 12V battery draining, I'd rather go without. We did carry a 12v jump pack initially in the 38kWh, due to the known 12V issues with this car. But now that we have this BM2 battery monitor instead, we don't carry the booster, as I keep it at work where it gets used.

[@ryanmohammed3743]

The major issue with these plug in electronics is engine bay heat, need to shield it from heat to last time

[@GoGreenAutos]

No heat in an EV engine bay. But even in an ICE vehicle, the 12V battery is far enough away and doesn't get hot. They're often surrounded by a plastic box to insulate them.

[@Exxodus74]

Handy little device, thx for the video

[@GoGreenAutos]

Thanks

[@clemenswyss8]

doesn't the BM2 drain the battery, i.e. mustn't it be connected to a "switched connector"? I know: you would loose continuous measuring ...

[@GoGreenAutos]

Obviously it uses power but it's so little it's not even measurable. It wouldn't be fit for purpose if it actually drained your battery.

[@au18ert]

Have you tested the BM6? Seems quite good if you have an older EV and want to know where the car is located, if you know what I mean 😅..

[@GoGreenAutos]

No, I didn't know there was a BM6. I will check it out. Thanks.

[@davidharvey5161]

Excellent. Will you be fitting one to your Tesla?

[@GoGreenAutos]

No, I don't have one on the Tesla. While a Tesla is still reliant on the 12V battery like all vehicles, they don't shut down the HV battery pack when turned off. So on a Tesla, the 12V doesn't get a chance to drain as much. The result is that they do last longer and you also get messages on the screen when the 12V needs replacing. But when you see the message the first time, you have to get on and replace it quickly as it will soon catch you out. So on a Tesla, you're less likely to be caught out with a dead 12V battery, but it still can happen. On the downside though, a Tesla will continue to eat through the traction battery charge when the vehicle is parked up, which isn't the case with other EVs. Mine typically uses about 1-2% per day.

[@clayton4115]

Thanks i've ordered one.

[@GoGreenAutos]

Glad it helped.

[@frankradcliffe1374]

Brilliant video

[@GoGreenAutos]

Thanks

[@rockinginafreeworld3256]

I have just fitted one on my ioniq 2022. It says charging when I’m not using the car. Is this normal?

[@GoGreenAutos]

The Ioniq will turn on and charge the 12V battery if it deems necessary. It normally does it about twice a night.

[@Adventures-and-More]

only gives notifications if within Bluetooth range

[@GoGreenAutos]

Correct. You couldn't expect anything more otherwise it would need a SIM card.

[@grahamjones8450]

I have a counter example: I started using Bluelink in late 2020 when I bought my Ioniq. Later I started using the integration it with Home Assistant. Recently I switched to Octopus Intelligent tarrif, which uses it. No problems have occurred with the Ioniq (EV battery, 12V battery, coolant etc). The Home Assistant integration exposes both EV battery level and "Car" battery level (the 12V battery), so I can already track the 12V battery state. Looking at the last couple of months the 12V battery has varied between 75% and 85% and doesn't drain especially much over night when controlled by Octopus, or when updating for the Bluelink App or Home Assistant. I suspect there are other sources of problems with the 12V battery, but my experience is only one measure. One question would be what happens if the EV is parked for a long time in an area without a mobile signal - will it do what phones can do, and drain the battery more quickly while searching for a signal? Even then a phone battery is much smaller capacity than the 12V battery, so the impact shouldn't be too great unless the EV is not used for a long time.

[@GoGreenAutos]

Yes I think you're probably right about the vehicle searching for a mobile signal - it must have an impact on the battery drain. Obviously telematics draining the 12V can affect many modern vehicles and not just EVs. Older 'dumb' vehicles don't suffer these issues anywhere near as much. Home Assistant is not something I've played with. We don't even use the Bluelink in the Ioniq. We didn't have it before in the 28kWh, so don't miss it. I just prefer to keep things simple and (hopefully) more reliable by not enabling Bluelink and so far that is proving to negate the 12V battery drains that these vehicles are prone too. This BM2 bluetooth battery monitor then gives us the peace of mind that we don't get caught out. Same goes with Octopus Intelligent and I've not gone onto that tariff as it complicates things further. Instead we've stuck with the Go tariff and push other things like the dishwasher, washing machine to run at night. The 4 hours of cheap rate electricity suites our charging needs just fine. I've read that some users have experienced issues with Intelligent and woke up in the morning to EVs that have not charged over night. I don't have the time to mess around with that just yet!

[@cheribibi112]

Hi I bought one but on my 28 i couldn t fot the +. There s no room. Is there a trick ?

[@GoGreenAutos]

You can squeeze it in there. Or leave the terminal cover lid open. In my case, I notched out the plastic to allow the BM2 wire to sit where the two surfaces closes.

[@johnfaulkner6776]

I had this problem with my Kia Soul during COVID lockup . Fortunately I have an old boating battery, deep cycle, in my garage. Didn't even need jump leads just a piece of cable for the 12v required. EVs have the wrong battery. A lead acid cranking battery is not what's needed here. Tesla are playing with a smaller more appropriate battery as we speak! The EV Achilles heel? Old world 12v battery.

[@GoGreenAutos]

Yes, Tesla are now using a 16V lithium battery. Here's an excellent video on it kzbin.info/www/bejne/bl6wf3mdltibprM

[@StephenLyons1984]

thank you as normal

[@GoGreenAutos]

Cheers. Glad you found it interesting.

[@firstsurname9709]

I own 15plate model s, is it worth me getting or does tesla have this inbuilt?

[@GoGreenAutos]

It wont do any harm and will only increase your knowledge and confidence, but I also have a Tesla Model S and I haven't fitted one. While a Tesla is still reliant on the 12V battery like all vehicles, they don't shut down the HV battery pack when turned off. So on a Tesla, the 12V doesn't get a chance to drain as much. The result is that they do last longer and you also get messages on the screen when the 12V needs replacing. But when you see the message the first time, you have to get on and replace it quickly as it will soon catch you out. So on a Tesla, you're less likely to be caught out with a dead 12V battery, but it still can happen. On the downside though, a Tesla will continue to eat through the traction battery charge when the vehicle is parked up, which isn't the case with other EVs. Mine typically uses about 1-2% per day.

[@a.c.e.7568]

Waste of money! I bought three of these BM2 Battery Voltage Monitors so that I can check on my batteries of my stored/parked vehicles as well as my daily driver in my garage and driveway and I wanted to be able to check them while sitting in my home. The range is about 12 feet as I have to be at my front door to get a signal. This is typical of Bluetooth devices where they state 10 meters or 33 feet but in unobstructed view, but not under a hood shrouded in metal. If I need to be that close to a vehicle, I might as well pop the hood and take a DMM meter to the battery.

[@lharris828]

Mine keeps losing lock with the phone - only 2 m away!

[@GoGreenAutos]

Not sure why that is. Have you tried deleting it and adding your device again?

[@lharris828]

@@GoGreenAutos yes. It works intermittently.

[@KiwiMechEng]

As a note, it logs every 2 minutes.

[@GoGreenAutos]

Thanks

[@mordyd1770]

Mate you really need to do some work on your presentation, dirty screens, dust everywhere, out of focus, c'mon bit more effort.

[@Markcain268]

Got a voltmeter on my dashboard 😁

[@GoGreenAutos]

Yep. But it is far more than that of course.

[@Markcain268]

@@GoGreenAutos that's all I need, got a booster in case it ever goes flat, but that's not happened for a long time as I often trickle charge it overnight after a few short journeys