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Adding a battery charger connection inside the fuel filler door

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DRPM635CSi
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Adding a battery charger connection inside the fuel filler door

Post by DRPM635CSi » Thu Jun 14, 2018 9:54 am

Just wondering if anyone has done this already and can maybe post some photos or advice?

I find myself needing a constant maintaining battery charger connected to the M6 battery in the boot. My weapon of choice is a CTEK MXS 3.8. What both simultaneously annoys and delights me about having the battery in the boot is that it's perfectly adjacent to the power socket on my wall in the garage this way when reverse parked, but also that the boot needs to be left open ajar in order to let the cables out for plugging into the wall. This of course also necessitates unplugging the power cable to the internal boot light so the power isn't drained at the same rate it's going in.

This dilemma has led to thinking about how to connect the battery externally so the boot lid can remain shut and the internal light power cable at the LH hinge connected. The CTEK charger comes with a cable designed for permanent connection via eyelet ring terminals to the battery clamp posts. It's not long enough at only ~400mm and its eyelet terminals are only M6 size which is not big enough for the M8 battery clamp bolts used in an M635CSi, but both of these things can be modified to suit.

I have bought a longer length of 15AWG red/black cable to make a new charger extension lead, I've drilled out the M6 eyelets to M8 size so they fit over the M8 battery clamp bolts and I've bought all new low resistance Anderson type connector plugs to replace the very small and restrictive IP65 plugs the charger comes equipped with new.

Now before I go doing all this soldering of new cables/plugs etc. I was thinking of doing the following:

Use the battery vent tube route to run the cable out of the battery box and down sharing the same grommet (or bigger if necessary) in the floor of the boot panel and down to behind the right rear wheel arch where the vapour capture bottle resides. From there, the cable then does a U-turn and heads back up again along with the fuel filler neck and up into the fuel filler behind the flap between the plastic shroud and the inner body panel to exit with an Anderson connector plug hanging there in the breeze ready to be connected to a matching Anderson plug connection on the output side cable of the CTEK battery charger.

My thinking is then that connecting the battery charger is a very simple case of park the car up, get out, open the fuel filler flap, plug the battery charger in, switch on battery charger and leave the fuel filler flap open. The open filler flap will serve as a warning sign not to drive off with the cable still connected because it will be an obvious visual warning being as how the fuel filler flap is on the driver's side and dare I say it, impossible to miss when getting in the driver's seat.

Can anyone see anything wrong with this plan before I start working on making it a reality? Anyone else done anything similar to make the task of connecting a maintenance battery charger that little bit easier and less invasive than constantly having to remove the warning triangle + the fabric trimmed cover panel from the battery box cover and then having to fish around inside the small openings to attach clamps to the battery terminals and then having to leave the bootlid open?

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Re: Adding a battery charger connection inside the fuel filler door

Post by JohnRogers » Thu Jun 14, 2018 11:38 am

This was my report on M6 battery charging. Regards, John Rogers
Attachments
Battery Disconnector NL 4.pdf
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Re: Adding a battery charger connection inside the fuel filler door

Post by DRPM635CSi » Thu Jun 14, 2018 12:01 pm

Thanks for that but reading your report there I think we're talking about different things. You appear to have fitted a battery isolation switch of a Cole-Hersey variety kind of thing to prevent unwanted static battery charge drain. I am more interested in a convenient external battery charging port. This not not quite the same thing. I do not wish to isolate the battery as I don't want to have to reprogram the radio & obc every time I drive the car.

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Re: Adding a battery charger connection inside the fuel filler door

Post by ericono » Thu Jun 14, 2018 12:47 pm

Electrically, I don't know enough to add any comment of value, but from a design/packaging point of view, this sounds like a really clean solution. The only possible concern I can come up with: is there any concern with fuel vapor in close proximity to the electrical plug? Otherwise, this seems like a really neat and nearly factory looking solution to the problem.

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DRPM635CSi
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Re: Adding a battery charger connection inside the fuel filler door

Post by DRPM635CSi » Thu Jun 14, 2018 2:17 pm

ericono wrote:
Thu Jun 14, 2018 12:47 pm
this seems like a really neat and nearly factory looking solution to the problem.
Thank you very much. I've been trying to think of a solution that is non-invasive as far as drilling holes is concerned, non-permanent and completely reversible if at all possible. I am willing to cable tie the power lead to the fuel filler neck to hold it in place, but I'm not willing to go drilling new holes in any metal bodywork or indeed even plastic shrouds or fabric trim. Looking in the boot today, the vapour vent hose grommet is the only factory hole to the outside world I can see on that side of the inside of the boot. It would be great of course if there was a hole directly into the back of the fuel filler cavity from the inside as that would make the exercise self-evidently easy, but there just isn't (for obvious reasons you'd have to say with the proximity of having fuel vapour and potential sparks from a battery). I'm not about to drill one through there either, so the only idea I could come up with was to share the exit with the battery vapour tube through the floor grommet ahead of the battery box.

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Re: Adding a battery charger connection inside the fuel filler door

Post by DRPM635CSi » Sat Jun 16, 2018 9:47 am

Got under the car & investigated the routing for the cable up to the inside of the fuel filler to find it is going to be very straightforward and easy. Removed the battery and then pushed out the grommet in the side of the battery box to remove the vent line hose. Amazingly the grommet actually came out intact with only minor damage, however it is rubber and it has gone quite hard, so I'm not going to re-use the old ones again. Found these instead locally. The BMW grommet has a Ø5mm hole, whereas the uncompressed vent hose line is Ø6mm. This means the vent hose line gets slightly crimped where it goes through the grommets. Not a big deal as it's not bad enough to block the vapour flow from the battery cells, but it does mean you can't move the hose through the grommets if necessary very easily. Where they are is where they stay sorta thing.

The replacement grommets have a Ø7mm hole through the middle of them. This allows me to get even the flared end of the vent tube that's been expanded by the plastic nipple that goes into the end of the battery through without too much drama or cutting the end off and it also allows the vent tube to be slid through easily without crimping damage to the tube.

The extra clearance is not enough to allow an additional 15AWG cable through there as well though, so a little bit of careful melting modification with a soldering iron I think is going to be necessary to open up the hole in the middle a bit to accept an electrical cable as well.

Looking at the fuel filler door, it is made symmetrical to suit both LHD & RHD cars, which is both sensible and fortunate. What's good is that I should be able to buy a second fuel filler holder 51171923919 and install it under the existing one in the bracket clip at the bottom of the door flap to use as the supporting bracket for mounting the electric connection plug to the door on the inside.

Think I might try and source a new rubber seal for the base of the fuel filler flap too 16111119235 as there doesn't seem a whole lot of life left in mine and it feels like it might split or tear quite easily with me pulling and bending it to get access to feed the cable through.

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Re: Adding a battery charger connection inside the fuel filler door

Post by sharkfan » Sat Jun 16, 2018 3:52 pm

Surely just trailing a cable out under the bootlid is easiest - I've been doing this with my M635CSi and Accumate for years with no issues.
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Re: Adding a battery charger connection inside the fuel filler door

Post by DRPM635CSi » Sun Jun 17, 2018 9:06 am

sharkfan wrote:
Sat Jun 16, 2018 3:52 pm
Surely just trailing a cable out under the bootlid is easiest - I've been doing this with my M635CSi and Accumate for years with no issues.
Yeah it's the having to leave the boot lid open that I'm trying to avoid. After messing around with the battery vent hose grommets today to try and route the extra wire I need there (which did work but was a bit messy), I found another more straight forward and simple way out of the battery box and into the fuel filler cavity for the wire. When I removed the rubber seal around the fuel filler neck I could see and get proper access to the three fuel vapour vent hoses that go through grommets in the side wall of the fuel filler door cavity. These are much larger grommets than the ones for the battery vent hose and need no modification at all to be able to easily slide an extra piece of 15 AWG wire through together with one of the vent hoses. On the inside the wire can then just loop around and enter the battery box through the same large U-shaped end grommet for the battery +ve lead cable, which I admit now makes a lot more sense having a power cable exiting with other power cables rather than squeezing it through a vent tube grommet. This will make for a much easier, shorter and straight forward route for the cable into the fuel filler void.

It will need some flexi-cable shield conduit to protect the cable on the inside from abrasion against the sharp edge of the internal strut the antenna mounting bolts to as the wire will be resting on it, but that's no big deal. I will scrap the vent hose route plans now, revert that back to how it was and start on the fuel vent line hoses option instead.

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Re: Adding a battery charger connection inside the fuel filler door

Post by sharkfan » Sun Jun 17, 2018 9:23 pm

No need to leave the bootlid slightly open, just shut the bootlid on the wire. I do, with no issues.
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Re: Adding a battery charger connection inside the fuel filler door

Post by 86_6series » Sun Jun 17, 2018 11:20 pm

I also would stay away from the filler door. I know you would plug the connection in first
before plugging in the battery maintainer. But man oh man that would make me very nervous.
The closed boot is a much better idea.

Just my $.02

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Re: Adding a battery charger connection inside the fuel filler door

Post by DRPM635CSi » Mon Jun 18, 2018 12:52 am

sharkfan wrote:
Sun Jun 17, 2018 9:23 pm
No need to leave the bootlid slightly open, just shut the bootlid on the wire. I do, with no issues.
In my particular case where I need to reverse park the car in the garage almost touching the rear wall for it to fit, is that with the bootlid closed, the car looks exactly the same whether the battery charger is connected or not. There would be a very real risk of me forgetfully getting in the car and driving off with the battery charger still connected and plugged into the wall. This would be a far greater danger than simply having it plugged into a lead exiting from the open fuel filler flap.

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Re: Adding a battery charger connection inside the fuel filler door

Post by baders » Mon Jun 18, 2018 4:46 am

Running the 13.8v leads into the boot and shutting it will provide no risk, even if you drive off. The Cteks are well protected. Far less risk than installing inside the fuel flap.
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Re: Adding a battery charger connection inside the fuel filler door

Post by nick88highline » Mon Jun 18, 2018 12:48 pm

I added an easy access charging point next to the fog light (mine is not an M so battery is not far from here), behind the later model's access panel:

Image

When the panel is open an LED flashes on the check panel so I don't drive off with my CTEK connected...
May not work on your car given this requires a specific later model body kit.
Nick

PS I have a switch in the trunk which can be used to turn off the internal light(s).
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Re: Adding a battery charger connection inside the fuel filler door

Post by sansouci » Wed Jun 20, 2018 12:30 am

Won't these CTEK maintainers work through the cig lighter? As I'm not a smoker I don't know if it is always hot (or not).
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Re: Adding a battery charger connection inside the fuel filler door

Post by nick88highline » Wed Jun 20, 2018 6:09 pm

sansouci wrote:
Wed Jun 20, 2018 12:30 am
Won't these CTEK maintainers work through the cig lighter? As I'm not a smoker I don't know if it is always hot (or not).
Yes, they will do as cigar lighter is always hot. :lol:
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Re: Adding a battery charger connection inside the fuel filler door

Post by DRPM635CSi » Thu Jun 21, 2018 1:10 am

nick88highline wrote:
Wed Jun 20, 2018 6:09 pm
sansouci wrote:
Wed Jun 20, 2018 12:30 am
Won't these CTEK maintainers work through the cig lighter? As I'm not a smoker I don't know if it is always hot (or not).
Yes, they will do as cigar lighter is always hot. :lol:
It is in UK delivered cars at least. It is not in Australian delivered cars and possibly not in US delivered cars either. Part of the local design laws designed to prevent children left in cars from playing around and setting themselves on fire.

In any case, plugging a battery charger into a cigarette light socket doesn't do anything to solve the problem of having to leave an opening ajar to let a power cable out.

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Re: Adding a battery charger connection inside the fuel filler door

Post by jps635 » Thu Jun 21, 2018 8:04 am

Not a good idea introducing a potential ignition source to where fuel vapours are likely to be present. I would think of another method. If you're concerned you might forget to disconnect a cables coming out the boot, park a yellow sponge or similar on your drivers side windscreen wiper every time you plug.
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Re: Adding a battery charger connection inside the fuel filler door

Post by DRPM635CSi » Thu Jun 21, 2018 8:33 am

jps635 wrote:
Thu Jun 21, 2018 8:04 am
Not a good idea introducing a potential ignition source to where fuel vapours are likely to be present.
You mean like the engine bay? Or the exhaust running right alongside the fuel tank? Or heaven forbid how about when refueling your car at the petrol station. How about when you place the metal nozzle back into the metal holster of the carrier handle in the bowser? That could spark too.
Amazing how many petrol stations you don't hear about bursting into flames every single day isn't it? Actually it's not that surprising at all because the risk is actually blown way out of all proportion to reality.

It's exactly the same unjustified panic that caused mobile phone use to be banned at petrol stations when they first became popular and the use of mobile phones in planes. Both risks since debunked as being complete and utter nonsense.

There is an actual electic current and a sparking variable resistor sitting right inside your fuel tank for god's sake! It's called the fuel level sender and it tells your fuel gauge on your dashboard how much fuel you have left. How many cars have you heard about blowing up because the fuel sender ignited the fumes inside the nearly empty tank? Lemme guess… umm, none?

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Re: Adding a battery charger connection inside the fuel filler door

Post by Pod » Fri Jun 22, 2018 3:40 pm

DRPM635CSi wrote:
Thu Jun 21, 2018 8:33 am
jps635 wrote:
Thu Jun 21, 2018 8:04 am
Not a good idea introducing a potential ignition source to where fuel vapours are likely to be present.
You mean like the engine bay? Or the exhaust running right alongside the fuel tank? Or heaven forbid how about when refueling your car at the petrol station. How about when you place the metal nozzle back into the metal holster of the carrier handle in the bowser? That could spark too.
Amazing how many petrol stations you don't hear about bursting into flames every single day isn't it? Actually it's not that surprising at all because the risk is actually blown way out of all proportion to reality.

It's exactly the same unjustified panic that caused mobile phone use to be banned at petrol stations when they first became popular and the use of mobile phones in planes. Both risks since debunked as being complete and utter nonsense.

There is an actual electic current and a sparking variable resistor sitting right inside your fuel tank for god's sake! It's called the fuel level sender and it tells your fuel gauge on your dashboard how much fuel you have left. How many cars have you heard about blowing up because the fuel sender ignited the fumes inside the nearly empty tank? Lemme guess… umm, none?
I was just about to say the same thing as jps635! I think the response was pretty fierce to someone just trying to give some (good) advice :shock:.
If you had ever experienced an under-bonnet fire, you'd understand :wink:

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