Best Jump Start Box for 1993 850Ci

[Denis G]

I have been evaluating the Hulkman Alpha 85, 85S and Alpha 100.
Which one is best for the dual battery 850Ci?

Specs are as follows:
Alpha 85
Peak Current: 2,000A
Battery Capacity: 20,000mAh/74 Wh

Alpha 85S same as above but has a pre-heat function

Alpha 100
Peak Current: 4,000A
Battery Capacity: 32,000mAh/118Wh

I ask because as those of us who are now close friends with the AAA tech who bails us out regularly, they use 2 jump boxes.
I'd prefer to keep my own to just one jump box.

Thanks!

[Timm]

[Denis G]

Thank you...points well taken!!!!!!!

Is it ok to charge the batteries through the port under the hood? I have a C-Tek charger.

[SteveCT]

I have used a C-Tek trickle charger for years on a '93 850Ci without any problems. I connected the dongle they supplied to the driver's side battery in the trunk, and attached to C-Tek to the dongle when the car is garaged.

[Denis G]

I have used a C-Tek trickle charger for years on a '93 850Ci without any problems. I connected the dongle they supplied to the driver's side battery in the trunk, and attached to C-Tek to the dongle when the car is garaged.

Thank you!!

[m6bigdog]

Jumping the starter batteries on a car should be the last thing you want to have happen.
If you don't have access to an electrical utility where your car is parked then it is better to disconnect the battery during the storage period; even if it is just a week.

Automotive starter batteries are designed to be kept at a 100% state-of-charge (SOC) during their lifetime and while that is practically impossible when they are ever and/or regularly allowed to dwell at even a few percent of depth-of-discharge (DOD) they will quickly loose their capacity and life span.
Hence, allowing the battery to discharge for days while the battery supplies the vehicle parasitic current drain and/or occasionally require a jump start, that will kill the battery in less than a year.
However, if the battery is maintained at 100% SOC, while a trickle charger supplies the vehicles parasitic current, when the vehicle is not inuse, the batteries will last 5-10 years.
I got 8-1/2 years out of the last pair of BMW Exide Batteries in my 850.

See attached graph.
While your mileage may very, the reality is allowing a lead-acid automotive starter battery to discharge from a parasitic load it will greatly shorten its useful life.
AGM batteries do better, however their lifespan is much longer if they are kept at 100% SOC between engine restarts.

[Denis G]

Jumping the starter batteries on a car should be the last thing you want to have happen.
If you don't have access to an electrical utility where your car is parked then it is better to disconnect the battery during the storage period; even if it is just a week.

Automotive starter batteries are designed to be kept at a 100% state-of-charge (SOC) during their lifetime and while that is practically impossible when they are ever and/or regularly allowed to dwell at even a few percent of depth-of-discharge (DOD) they will quickly loose their capacity and life span.
Hence, allowing the battery to discharge for days while the battery supplies the vehicle parasitic current drain and/or occasionally require a jump start, that will kill the battery in less than a year.
However, if the battery is maintained at 100% SOC, while a trickle charger supplies the vehicles parasitic current, when the vehicle is not inuse, the batteries will last 5-10 years.
I got 8-1/2 years out of the last pair of BMW Exide Batteries in my 850.

See attached graph.
While your mileage may very, the reality is allowing a lead-acid automotive starter battery to discharge from a parasitic load it will greatly shorten its useful life.
AGM batteries do better, however their lifespan is much longer if they are kept at 100% SOC between engine restarts.

Thank you for the thorough advice...I now have switches installed on the batteries so I can disconnect them from the car's electrical system when the 850 is not in use for a while.

[Hogg]

Resurrecting this thread...

I have a 2001 740iL that i just bought. Brand new battery. Stupidly left the light son. Tried to start car - click, click, click. Battery at 10v or so. Used a NOCO GB40 1000amp jump pack connected to the engine bay terminal and shock tower nut. Nada. Let it sit for 15 mins, still nada. Ended up bringing my sons e30 over to jump the car. Yah yah i know not meant to jump BMWs, take the battery out etc. I have looked at the wiring diagram for the dual battery system (i have an electrical engineering degree) and cant see any possible way that jumping this car from the engine bay could cause any issues. All i can think is that people that fry stuff have participated in that good old "user error" model of doing things.

So, what booster have people used successfully with these cars? Like actually used with a relatively dead battery!
Right side angle.jpeg
Front seats from drivers door.jpeg

[LappingLuke]

The NOCO ones work really well in my experience but I have run into issues with them at work where if the battery you're jumping off is too low they will refuse to work. They check the voltage and will balk if its too low. Its one downside of them. I work in engineering for a major construction and ag equipment company and we have many of the NOCOs for jumping off machines that have sat for ages.

[the green amigo]

I like the good ole Jump n carry 770

[Hogg]

The NOCO ones work really well in my experience but I have run into issues with them at work where if the battery you're jumping off is too low they will refuse to work. They check the voltage and will balk if its too low. Its one downside of them. I work in engineering for a major construction and ag equipment company and we have many of the NOCOs for jumping off machines that have sat for ages.

I measured the battery voltage, thinking that might be the issue. On the NOCOs it has to be below 2V i think. Mine was at 10 volts. Im assuming the battery pack just didnt have enough juice. This car is the two battery variety so maybe that was interfering with the jump, if both were way down.

[LappingLuke]

"2 battery" cars are just one big battery split in half. They don't go dead separately from each other. Being wired in parallel they are always at the same voltage as the other but that doesn't mean they might not age slightly differently, or God forbid if you replace one and not the other, that is another recipe for problems. But yeah, your mention of being around 10V is about what I recall from having a NOCO not work for me. They just won't allow a jump in that case.