MHD Battery Charger?

Specific discussion about the E89 2009 Z4 (sDrive35is, sDrive35i, sDrive30i, sDrive23i)
Chris1712
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MHD Battery Charger?

Post by Chris1712 » Thu May 16, 2019 10:03 am

Hi All,

Planning to flash Stage 1+ this weekend, but need a battery charger to be safe. Can anyone recommend something cheap and cheerful? I will never use it again so a bit hesitant to spend out on a C-Tek.

How many amps do I need? I've heard 5A is enough but also that the fuel pump pulls 20A so surely I need to account for that?

Currently eyeing up this: https://www.amazon.co.uk/Black-Decker-B ... way&sr=8-3


Thanks,
Chris
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MHD Battery Charger?

Post by mr wilks » Thu May 16, 2019 10:07 am

Whereabouts are you located?
Sure a member would loan you one.
Im in Lancs if that helps.
I used a trickle charger for 6 hrs to fully charge my battery prior to the MHD flash then left it attached during the process . No issues :thumbsup:
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MHD Battery Charger?

Post by Chris1712 » Thu May 16, 2019 11:14 am

mr wilks wrote:
Thu May 16, 2019 10:07 am
Whereabouts are you located?
Sure a member would loan you one.
Im in Lancs if that helps.
I used a trickle charger for 6 hrs to fully charge my battery prior to the MHD flash then left it attached during the process . No issues :thumbsup:
Somerset, bit of a trek from you :driving:. A trickle charger was my other thought, at least I might use that in the future (dreaming of a classic car and a garage :roll: )

https://www.amazon.co.uk/Battery-Automa ... 46&sr=8-19 ?
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MHD Battery Charger?

Post by R.E92 » Thu May 16, 2019 11:22 am

You don't really want to use a standard battery charger as you risk causing voltage fluctuations which can cause problems.

For DIYers there are solutions like this: https://www.boostaddict.com/showthread. ... r-Flashing

In all honesty you don't really need a charger for MHD if you battery is in good health. I've never used one and have previously done hour long module reads without any problems. If you turn off the lights, AC and stereo then there is absolutely no issues with a 20min write.
MHD now keeps the fuel pump off while flashing so there's a lot less drain.

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MHD Battery Charger?

Post by Chris1712 » Thu May 16, 2019 11:25 am

R.E92 wrote:
Thu May 16, 2019 11:22 am
You don't really want to use a standard battery charger as you risk causing voltage fluctuations which can cause problems.

For DIYers there are solutions like this: https://www.boostaddict.com/showthread. ... r-Flashing

In all honesty you don't really need a charger for MHD if you battery is in good health. I've never used one and have previously done hour long module reads without any problems. If you turn off the lights, AC and stereo then there is absolutely no issues with a 20min write.
MHD now keeps the fuel pump off while flashing so there's a lot less drain.
Anyway to tell my battery health though? I've never had any problems, car is 64 reg on 39k. If I ended up with a half flashed dead car though I would be pretty bloody infuriated.
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MHD Battery Charger?

Post by ph001 » Thu May 16, 2019 11:32 am

The fuel pump pulling 20A is not relevant to the size of your charger as that is not something that is running all the time. Any large current pulses like that will simply be taken from your main battery. Really, as long as your main battery is fully charged you will not have any issues.

If you really want something cheap and cheerful to keep things topped up that you will never use again, just buy the cheapest thing you can find such as this... https://www.amazon.co.uk/Laptronix-Batt ... ay&sr=8-19

Alternatively the Aldi / Lidl ones would be fine too and have the advantage of being smart chargers (not that that matters for what you are doing)

The one you link to will be fine too I suppose, but it seems a bit like a halfway house between a budget one and a decent one. If it were me I would just buy something decent quality such as the Ctek MXS5.0 and actually use it as my go to charger.

Don't worry about voltage fluctuations - it's all regulated down to 12V / 5V / 3.3V in the ECU anyway. As long as your car battery stays above 12.5V, you will have no issues.
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MHD Battery Charger?

Post by R.E92 » Thu May 16, 2019 1:22 pm

ph001 wrote:
Thu May 16, 2019 11:32 am
The fuel pump pulling 20A is not relevant to the size of your charger as that is not something that is running all the time. Any large current pulses like that will simply be taken from your main battery. Really, as long as your main battery is fully charged you will not have any issues.

If you really want something cheap and cheerful to keep things topped up that you will never use again, just buy the cheapest thing you can find such as this... https://www.amazon.co.uk/Laptronix-Batt ... ay&sr=8-19

Alternatively the Aldi / Lidl ones would be fine too and have the advantage of being smart chargers (not that that matters for what you are doing)

The one you link to will be fine too I suppose, but it seems a bit like a halfway house between a budget one and a decent one. If it were me I would just buy something decent quality such as the Ctek MXS5.0 and actually use it as my go to charger.

Don't worry about voltage fluctuations - it's all regulated down to 12V / 5V / 3.3V in the ECU anyway. As long as your car battery stays above 12.5V, you will have no issues.
The fuel pump is relevant if using other flashing software. When the fuel pump module (EKP) loses communications with the ECU it will by default start to run. Since flashing the ECU involves taking it offline the fuel pump will run for the entire duration of the flash. MHD sends a heartbeat signal to the EKP module which means it thinks the ECU is still OK.

The battery just needs to keep above 11V for the flash. Below 11V the ECU will power off.

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MHD Battery Charger?

Post by Chris1712 » Thu May 16, 2019 2:39 pm

R.E92 wrote:
Thu May 16, 2019 1:22 pm
The fuel pump is relevant if using other flashing software. When the fuel pump module (EKP) loses communications with the ECU it will by default start to run. Since flashing the ECU involves taking it offline the fuel pump will run for the entire duration of the flash. MHD sends a heartbeat signal to the EKP module which means it thinks the ECU is still OK.

The battery just needs to keep above 11V for the flash. Below 11V the ECU will power off.
Good to know, think I'll go with the up to 8A smart charger and top it up before hand. Fingers crossed! If not there'll be lots of panic posts by me tomorrow night :headbang: .

Should I connect the battery charger straight to the battery or to the special terminals under the bonnet? Do I need ignition on beforehand?
  • Get in car
    Plug cable into OBD port
    Plug cable into phone
    Buy Flasher + Stage 1 map pack from MHD Store
    Airplane Mode
    Insert key
    Lower drivers window
    Turn off headlights, vent fans and DRLs
    Get out of car, close door and lean in and press the ignition button
    Start the flash
Where can I find the differences between v7/v8 maps? I'll be going for regular 95 ron as getting 99 around here is tricky.
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MHD Battery Charger?

Post by R.E92 » Thu May 16, 2019 3:21 pm

Chris1712 wrote:
Thu May 16, 2019 2:39 pm
R.E92 wrote:
Thu May 16, 2019 1:22 pm
The fuel pump is relevant if using other flashing software. When the fuel pump module (EKP) loses communications with the ECU it will by default start to run. Since flashing the ECU involves taking it offline the fuel pump will run for the entire duration of the flash. MHD sends a heartbeat signal to the EKP module which means it thinks the ECU is still OK.

The battery just needs to keep above 11V for the flash. Below 11V the ECU will power off.
Good to know, think I'll go with the up to 8A smart charger and top it up before hand. Fingers crossed! If not there'll be lots of panic posts by me tomorrow night :headbang: .

Should I connect the battery charger straight to the battery or to the special terminals under the bonnet? Do I need ignition on beforehand?
  • Get in car
    Plug cable into OBD port
    Plug cable into phone
    Buy Flasher + Stage 1 map pack from MHD Store
    Airplane Mode
    Insert key
    Lower drivers window
    Turn off headlights, vent fans and DRLs
    Get out of car, close door and lean in and press the ignition button
    Start the flash
Where can I find the differences between v7/v8 maps? I'll be going for regular 95 ron as getting 99 around here is tricky.
Connect to the positive terminal and the chassis screw which is nearby. Not directly to the battery.

The rest of the procedure is perfect.

Are you using a Bimmergeeks cable to do the flash? It halves the flash times so the first write should only take 20 minutes rather than the 40 that all other cables take. Makes it much less risky.

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MHD Battery Charger?

Post by Chris1712 » Thu May 16, 2019 3:26 pm

Ordered from cable-shack in the end, all the Europe Bimmergeeks suppliers were out of stock. Are they any good? It's in the MHD pdf guide so I assumed it was a solid cable? Which direction should I have the switch?

EDIT: I'm guessing towards 'D' not 'K' based on the Bimmergeeks cable which is also switched.
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MHD Battery Charger?

Post by Chris1712 » Fri May 17, 2019 10:31 am

OK here's my new list :p

Plug in Battery Charger (set to 2A, AGM)
Attach positive to starter point under bonnet
Attach negative to chassis ground
Turn on Battery Charger
Up to 8A charge if needed
Wait a while
Get in car
Switch cable to 'D'
Plug cable into OBD port
Plug cable into phone
Buy Flasher + Stage 1 map pack from MHD Store
Airplane Mode
Insert key
Lower drivers window
Turn off headlights, vent fans and DRLs
Get out of car, close door and lean in and press the ignition button
DME Backup
Start the flash
Finish Flash
Ignition Off
Key out, wait 30s
Disconnect Negative
Disconnect Positive
Unplug Charger

Get back in car and cross fingers, clench butthole and pray.
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MHD Battery Charger?

Post by Chris1712 » Fri May 17, 2019 7:59 pm

Well, fallen at the first hurdle - not even that!

It appears I have an incredibly loose / useless OBD port!? I cannot get either the new cable or my old Wi-Fi ELM327 to sit properly at all! It will absolutely not click down or even close, it’s wobbly and loose.




Wtf?
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MHD Battery Charger?

Post by R.E92 » Sun May 19, 2019 10:30 am

Chris1712 wrote:
Fri May 17, 2019 7:59 pm
Well, fallen at the first hurdle - not even that!

It appears I have an incredibly loose / useless OBD port!? I cannot get either the new cable or my old Wi-Fi ELM327 to sit properly at all! It will absolutely not click down or even close, it’s wobbly and loose.




Wtf?
Your OBD port seems buggered. I wouldn't attempt a flash like that.

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MHD Battery Charger?

Post by Chris1712 » Sun May 19, 2019 11:15 am

Yeah on closer inspection it looks like one of the female pins is a bit mangled on the connector. Will try and find an auto electrician to replace the port ASAP, normally I’d do it myself but the access is so fiddly I don’t want the hassle tbh!

No idea how it’s happened, an over zealous technician maybe. Pretty annoying as I do have warranty, but I’m sure it’s not worth the £100 excess.
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MHD Battery Charger?

Post by Chris1712 » Sat Aug 10, 2019 6:34 pm

Huge bump!

Finally got my OBD port fixed and I’m flashing right now.... almost touching cloth the anxiety is terrible.
C4BBECC5-3B96-45CE-BC9C-82E362217776.jpeg
C4BBECC5-3B96-45CE-BC9C-82E362217776.jpeg (430.81 KiB) Viewed 106 times
Probably should have hoovered the seats first. I also only realised after I’d got out and started the flash that the DRLs are always bloody on! I thought ‘0’ was everything off on the lights dial but nope. Fingers crossed.
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