[DevilsM8]

My M8 is in the garage for long periods of time since it is not my daily driver. What are the groups thoughts on keeping it on a Battery Tender/Charger?

[yugrac]

The last 2 summers I have left my 2022 M850 on a CTEK MXS 5.0 battery charger/maintainer, in my Florida homes climate controlled garage, for 4-5 months without issue apon return. I believe others have had similar experiences. I think 6 weeks max without any charging to the battery will potentially result in a low battery CCA condition, due to the many idle state power draws in these vehicles and you don't want to be in that scenario.

[m3_08]

my m8 get driven once in 2 weeks for 15-20 miles and its been fine. Didn't try more than two weeks hibernation

[Tenac]

Tenders are cheap batteries cost a shit load..... lol I have three always accessible for any one of my rides.

[RJC-1]

My ‘19 M850 only has ~5800 miles on it and so long as it’s driven every few weeks or so it’s all good. I do have the best model of the BMW branded chargers and observed it do lots of charging/discharging in a cycle… not sure why it does that so I stopped using it,

[Beemer5to3]

I drive mine once a week or less at the minute, and often use a charger - I’m on the fence about keeping it long term, so want to ensure everything is kept in tip top condition. I use a NOCO Genius 5 and it’s excellent. Just leave it on for a few days at a time and keeps the battery sorted.

[Seaford]

Originally Posted by DevilsM8

My M8 is in the garage for long periods of time since it is not my daily driver. What are the groups thoughts on keeping it on a Battery Tender/Charger?

Definitely leave it on a conditioner….you MAY find some stuff will not be working when you go to use it such as stop/start, comfort access.

a good conditioner won’t do it any harm and it takes an awfully long run to recharge the battery fully - I use this https://no.co/genius5

[Hornethandler]

Originally Posted by DevilsM8

My M8 is in the garage for long periods of time since it is not my daily driver. What are the groups thoughts on keeping it on a Battery Tender/Charger?

I read a few posts about excessive current draw while in sleep mode in earlier models of these vehicles. It seems that’s not the case with later models; however, I couldn’t find info. on specific years.

That being said, my car (2023 G15) sits in cold weather and I’ve been monitoring the battery voltage regularly. I’m not seeing anything that causes concern, i.e., the voltage is only dropping around .15 volts (150 milli volts) in a week or so of sitting.

I would, however, recommend not allowing the battery to sit for more than a couple of weeks without charging. AGM lead acid batteries like to be fully charged. Allowing one to sit in a low voltage state results in lost capacity and shorter life.

The BMW charger/maintainer is a rebranded good quality Ctek charger designed for these AGM lead acid batteries, and I’d recommend charging at least once every couple of weeks to ensure good battery performance and long life.

Good luck!

[Tenac]

Originally Posted by Hornethandler

I read a few posts about excessive current draw while in sleep mode in earlier models of these vehicles. It seems that’s not the case with later models; however, I couldn’t find info. on specific years.

That being said, my car (2023 G15) sits in cold weather and I’ve been monitoring the battery voltage regularly. I’m not seeing anything that causes concern, i.e., the voltage is only dropping around .15 volts (150 milli volts) in a week or so of sitting.

I would, however, recommend not allowing the battery to sit for more than a couple of weeks without charging. AGM lead acid batteries like to be fully charged. Allowing one to sit in a low voltage state results in lost capacity and shorter life.

The BMW charger/maintainer is a rebranded good quality Ctek charger designed for these AGM lead acid batteries, and I’d recommend charging at least once every couple of weeks to ensure good battery performance and long life.

Good luck!

You are correct for the AGM batteries, just small adjustment is the M8 has the LIon. Which basically follows the same rules as well. Either way batteries are meant to have duty cycles and should be on a smart tender not a dumb one that you use for trying to get it to start. Ctek all the way here!!.

[Moopai]

I see different ones offered from Ctek, is there a specific one you recommend? Do you connect the charger to the battery next to the engine or the one in the trunk? Thanks

Originally Posted by Hornethandler

I read a few posts about excessive current draw while in sleep mode in earlier models of these vehicles. It seems that’s not the case with later models; however, I couldn’t find info. on specific years.

That being said, my car (2023 G15) sits in cold weather and I’ve been monitoring the battery voltage regularly. I’m not seeing anything that causes concern, i.e., the voltage is only dropping around .15 volts (150 milli volts) in a week or so of sitting.

I would, however, recommend not allowing the battery to sit for more than a couple of weeks without charging. AGM lead acid batteries like to be fully charged. Allowing one to sit in a low voltage state results in lost capacity and shorter life.

The BMW charger/maintainer is a rebranded good quality Ctek charger designed for these AGM lead acid batteries, and I’d recommend charging at least once every couple of weeks to ensure good battery performance and long life.

Good luck!

[Tenac]

Originally Posted by Moopai

I see different ones offered from Ctek, is there a specific one you recommend? Do you connect the charger to the battery next to the engine or the one in the trunk? Thanks

From the engine, this way the system controls itself, if you connect to the battery directly it can cause over voltage issues. Also they have the new CS one out from CTek If I remember correctly it does all types. Might wanna look into that. Other wise you can just find out which battery you have for sure and chat with them they will give you the correct ones to use. I did that on my Porsche bc it was in the shop at the time and they hooked me up with 10% off too while chatting.

[Moopai]

Thanks. So this is the same one BMW dealers selling under the BMW logo? I reached out to CTek and gave them the model of my vehicle. Hopefully will get a response in the next couple of days. Do you typically close the hood completely when charging or leave it slightly open?

Originally Posted by Tenac

From the engine, this way the system controls itself, if you connect to the battery directly it can cause over voltage issues. Also they have the new CS one out from CTek If I remember correctly it does all types. Might wanna look into that. Other wise you can just find out which battery you have for sure and chat with them they will give you the correct ones to use. I did that on my Porsche bc it was in the shop at the time and they hooked me up with 10% off too while chatting.

[Hornethandler]

Originally Posted by Moopai

I see different ones offered from Ctek, is there a specific one you recommend? Do you connect the charger to the battery next to the engine or the one in the trunk? Thanks

I use a Ctek MXS 5.0 (see link below), as do many others from another forum I’m on. It has settings for small and large 12 Volt AGM and non-AGM (flooded lead acid) batteries. AGMs charges to a slightly higher voltage (300 milli volts) than non-AGMs.

It also has a “Recondition” setting, but it’s only used on non-AGM batteries to help prevent stratification. AGMs are not prone to stratification.

Ctek is the rebranded charger/maintainer sold/provided by Mercedes, Porsche, Ferrari and others.

https://smartercharger.ca/collection...s/ctek-mxs-5-0

Pg. 282 of my 2023 BMW Owners Manual states:
“Only connect battery chargers for the vehicle
battery to the jump-start terminals in the engine
compartment.”

I’ve confirmed that the small Li-ion battery's “battery controller” receives voltage from the charger/maintainer; however, I did not measure directly at the Li-Ion battery's output terminals to confirm it was charging. If I ever find those terminals I will measure and update.

Edit: I just re-read your post. The battery "next to the engine" in the M850i is the small Li-Ion battery located in front of the passenger side firewall. Do not connect the charger there. Only connect the charger to the jump-start terminals.

[yugrac]

Originally Posted by Moopai

Do you typically close the hood completely when charging or leave it slightly open?

I completely close my hood and have had no issues. Also, re-enforcing Hornethandler , ONLY use the jump-start terminals under the hood.

[Hornethandler]

Originally Posted by Moopai

Thanks. So this is the same one BMW dealers selling under the BMW logo? I reached out to CTek and gave them the model of my vehicle. Hopefully will get a response in the next couple of days. Do you typically close the hood completely when charging or leave it slightly open?

Re: "Do you typically close the hood completely when charging or leave it slightly open?"

I leave the hood slightly open for fear of pinching the wires, or at the very least, leaving a permanent flat spot in the hood weatherstripping.

[RJC-1]

Originally Posted by Hornethandler

Re: "Do you typically close the hood completely when charging or leave it slightly open?"

I leave the hood slightly open for fear of pinching the wires, or at the very least, leaving a permanent flat spot in the hood weatherstripping.

Good points - I believe the battery also heats up while charging so leaving the hood open helps with it too

[yugrac]

Originally Posted by Hornethandler

Re: "Do you typically close the hood completely when charging or leave it slightly open?"

I leave the hood slightly open for fear of pinching the wires, or at the very least, leaving a permanent flat spot in the hood weatherstripping.

I have found a path for the charger wire that eliminates both of these issues. Look closely just above the headlight area and I think you'll see a path and you can close the hood, eliminating the 'open hood' warnings.

[yugrac]

Originally Posted by RJC-1

Good points - I believe the battery also heats up while charging so leaving the hood open helps with it too

The battery for my M850 is in the trunk. I think it is also for the M8.....?
Also, once the battery hits full, the CTEK pulses to maintain proper battery charge and I don't believe there is any significant heat during that process.

[RJC-1]

Originally Posted by yugrac

The battery for my M850 is in the trunk. I think it is also for the M8.....?
Also, once the battery hits full, the CTEK pulses to maintain proper battery charge and I don't believe there is any significant heat during that process.

The M850 has two batteries, AGM in trunk and Lith under hood, the M8 only has one and I believe it's under the hood. If I'm not mistaken, all types of batteries heat up when charging.

[Hornethandler]

Originally Posted by yugrac

I have found a path for the charger wire that eliminates both of these issues. Look closely just above the headlight area and I think you'll see a path and you can close the hood, eliminating the 'open hood' warnings.

Thanks! I'll take a look.
That will probably be a good place to run the permanent installation quick disconnect cable that comes as an accessory with the Ctek MXS 5.0 charger.

I'll probably leave mine open a crack anyway so I won't have to cycle (open/close) the door and hood unnecessarily. I really don't like slamming the hood any more than I have to. My other car's hood is the same... it locks in three places and you have to close it with some authority. I can't help thinking the shock will cause a chunk of paint to fly off.

[bloozemanAZ]

If you have a M8 (only Lithium) than you want a CTEK 56-926 LITHIUM. The Ctek MXS 5.0 technically is wet cell (including AGM). With a M850i with both lithium and AGM I played the "dance" with several chargers including the CTEK lithium model as well as a NOCOS Genius 10 (AGM and Lithium).

As others have stated you only ever connect to the "jump start" terminals under the hood. The catch-22 when reading the M850i manual is to switch from AGM to Lithium only a certain voltage is allowed and that killed the NOCO (as in I returned it). Bought the BMW OEM'd CTEK as it appears to be a unique animal, i.e., not a consumer version available.

It's a few $ more ($40) than either the MXS, Lithium or NOCO. But it's guaranteed to work on the only hybrid (loosely stated) aspect of the M850i. I'm trying to determine if the wife's new LCI X5 is a similar config or just a single lithium/AGM. Either way same part number so I'm golden.

[yugrac]

The jump-starter terminals under the hood only charge the AMG battery in the trunk when the engine is not running.

Credit to weinerbarn in this thread, post #12, for the explanation.

https://g05.bimmerpost.com/forums/sh....php?t=1987547