Yes, you definitely need to disconnect the BMS from the -ve post. worst case, you buy a new one, best case, you need to reset the throughput due to implausible values.
What did you do with your Range Rover today
- Thread starter Dopey
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RangeRoller dt
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Yes - Why would you chance it considering the risk?
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Well I'm asking for a friend
had a battery battery problem, went to garage and now had all sorts of issues. Been told the car is scrap (cam belt gone) and offered £300 for it!My gut feeling is they've damaged a wire somewhere and/or are just thick or they've done something stupid.
Engine still runs so cam belt is fine. I'm trying to think of options before he goes any further
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Get the car back and have it checked by someone else 
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Yes he's got it back but doesn't know the first thingGet the car back and have it checked by someone else
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What work was done on it kerms? What car?
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My Ring Charger has Battery % charged, and CCA/EN test modes. Most modern cars give false readings if the battery is tested while still connected to the car.
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its a Mercedes c250 CDI sport 2011What work was done on it kerms? What car?
wouldnt start/dead battery, battery replaced.. started to stall and dash lights.. managed to get it idling ok but in limp mode
Datatek
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Datatek
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You could certainly confuse all the ECU's
Its fine to charge a battery on a vehicle with a BMS provided you connect the negative charging lead to the body, not the battery terminal. That way, the BMS is aware of the charge input and will 'account' for it. If a battery is going to be tested by means of a heavy electrical load being applied, the negative terminal should always be disconnected regardless of whether the vehicle is equipped with a BMS or not.
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thanks for that, whenever i'd done a test its always been on a battery taken off for charging so i've never had do consider it
RangeRoller dt
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Dodgy AF mate. You did the right thing get it out of there
Is there a reason for this not to use the negative terminal.
Earth is Earth surely?
J
On what car?
J
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Surely whether you connect a charger to one end or other of the battery earth cable (terminal/chassis) makes no difference?
Forgive me if I'm being thick
I can see you wouldn't connect to the business side of the bms
Forgive me if I'm being thick
I can see you wouldn't connect to the business side of the bms
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In fact. I charge using via the trailer socket, surely that can't be an issue?
What about folks who use solar chargers?
What about folks who use solar chargers?
Datatek
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The negative for the trailer socket is connected to the chassis o is in line with the advice from Graculus.
