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M2 Technical Topics > Navigation, iDrive, Audio, Video, Bluetooth, Phone, Cameras, Electronics > Use a jump starter battery unit while flashing through OBD?

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      05-16-2020, 03:34 AM   #1
3t3p
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Use a jump starter battery unit while flashing through OBD?

So I did Thor flashing yesterday and according to idrove drained the battery. Luckily the flash completed and it started up fine.

I don't own a battery charger but have an 18,000mah Arteck (Seems well made) jump starter battery. So in theory it can provide nearly 18Amps for an hour.

Now I know it's not to CHARGE my battery. But is there anything precluding me from leaving it connected while flashing the car to reduce stress on the lead acid battery in the car?

Arteck instructions say when car has started to disconnect the unit within 15-20s, so presumably the answer is no and I need to invest in a charger.
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      05-17-2020, 10:20 AM   #2
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Right having done more research the usual 'plug in a battery charger' while coding/flashing is incorrect. What you would need is a voltage stabliser which is usually 300 /$ +.

Battery chargers are incapable and not designed to offset the current draw incurred by coding. Your best bet is to top off the battery then flash/code then charge it again when finished.

Went for a long drive today and auto start stop functioned for the first time in a long time. So it is highly probably my daily commute of 5 miles total is not charging my battery correctly.

For what it's worth I went for the Noco Genius 10(UK) as don't have a garage, when I'm on charge I want it done as soon as possible. Also AGM batteries should be charged at a higher C rating as possible, they actually like it. 10 Amps doesn't even tickle them tbh.

Was torn between CTEK but 1) there was no stock in UK anymore (lockdown = flat batteries!) and 2) common reliability issue of the mode button failing and CTEK being lousy about honouring warranty.
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      05-17-2020, 04:46 PM   #3
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5 miles of driving is definately not enough to keep the battery full, even more if you're driving to slow.

You'll need to find a longer route to work
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      05-17-2020, 05:58 PM   #4
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Hehe. Whole point was to get a short commute.

Does anyone know if using the repair function on a battery charger is safe via the front terminals under the bonnet?

Worried it could fry something.
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      05-17-2020, 07:27 PM   #5
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Quote:
Originally Posted by 3t3p View Post
Hehe. Whole point was to get a short commute.

Does anyone know if using the repair function on a battery charger is safe via the front terminals under the bonnet?

Worried it could fry something.
Not sure what the repair function is, but you should always be using the terminals under the hood for charging.

You don't need a full power supply for thor/bm3/mhd coding. Just make sure the battery is full via charger before starting. Only time you need the power supply is if you're doing a full upgrade on something like the nav unit or istep which will take over an hour. For the nav update I just hooked up my other car with jumper cables while it was running to get the constant voltage.
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      05-18-2020, 09:58 AM   #6
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The desulfation mode a lot of modern chargers have. It pulses higher voltage rapidly (I think in the kHz range) to reduce any sulphur (Uk spelling, enjoy that rest of the world!) crystallisation on the lead plates.

I think I'm not going to bother anyway but it can prolong batteries supposedly or rejuvinate lacklustre ones.

So I was worried about such a mode going through the front terminals with the rest of the car's electrical gubbins hooked up.
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      05-18-2020, 11:15 AM   #7
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any electrical charging needs to go through the front terminals so that you don't bypass the electronic failsafes.

If you are worried about long term power supply during any procedure you need a bench charger that can provide 20-30amps constant. Trickle chargers can not do this.

Alternatively you can just make sure your trickle charger has topped off your battery already or go for a long extended drive of 30+ mins. This will be sufficient for quick flashes/coding that only take a couple minutes.

For longer flashing sessions such as iDrive/iStep, you need a bench charger
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      05-19-2020, 05:56 PM   #8
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Cheers Nioh.

My battery resting voltage was 12.0v using a multimeter. Considering it is AGM construction this is <25% capacity having the day before been driven three + hours!

So on goes the Noco Genius 10, via the front posts, it confirms battery is under twenty five percent.

I came to check on everything an hour later and it was saying most of the charging was done, which seemed too quick, with voltage at the terminals (while still charging) being 13.3v if I recall.

Left it again and came back, this time it seemed sure it was largely done with only the final phase to go. I disconnected at put away the charger, voltage was now 12.8v which is not 100% for AGM but the charger needed more time. I had to put it away for the night.

Wondering now to use the desulfation mode via front terminals or not, but don't want to fry the cars electrics obviously!
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