D4's charging / battery problem

Ferret, I’m with you. Post the CSV of the data. I’ve seen similar. Stupid car love to deplete the battery. It probably explains why these vehicles only get 3 odd years from a battery yet others get twice that on average. My Audi got 11 years out of its! It also explains why people endlessly tell you to put it on a charger monthly if you want the battery to survive. No other car I’ve owned needed this level of attention for its battery.

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Originally Posted by Milton477

Here you are Drivesafe

Attachment 155851

That was after a warning to start the car. I had 2 Optimas i circuit + the cranking battery. Were the Optimas taking 50A each?

You should see what having a DC2DC charger does to the charging circuit when the batteries are down a bit. Current cycles between 50A & 200A continuously. I have now added a remote control to enable me to disconnect the 12V from the D4 to the DC2DC until the D4 batteries are charged up a bit.

When somebody figures how the D4 BMS works, please let us into the secrets.

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EDIT READ Milton ( sorry Ferret ), what size alternator have you got on your D4.

Also, you should not have to disconnect your DC/DC device to be able to charge the cranking battery, the DC/DC device should draw no more than 50 amps, for a 40 amp DC/DC device.

Older type DC/DC device can draw high currents but it is unlikely to be drawing 200 amps.

You are right Drivesafe, I shouldn't have to disconnect but my D4 charging system has it's own mind. My alternator is standard whatever that may be. The modern DC2DC pushes 50 amps into my van's LifeP04 batteries while drawing around 60 amps from the D4.

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Originally Posted by Milton477

You are right Drivesafe, I shouldn't have to disconnect but my D4 charging system has it's own mind. My alternator is standard whatever that may be. The modern DC2DC pushes 50 amps into my van's LifeP04 batteries while drawing around 60 amps from the D4.

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Standard D4 is 220amp alternator. Replacements though came out at 180amp for whatever reason. That’s what I fitted to mine when I replaced mine

I guess that I should look after my original then.

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Originally Posted by Milton477

You are right Drivesafe, I shouldn't have to disconnect but my D4 charging system has it's own mind. My alternator is standard whatever that may be. The modern DC2DC pushes 50 amps into my van's LifeP04 batteries while drawing around 60 amps from the D4.

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I was working on a 40 amp DC/DC device and your 50 amp unit would draw up to 60 amps.

Something is not quite right, unless you were it traffic, driving slowly which would mean your revs were low, otherwise, at any normal speed, your alternator output current can be up to it’s maximum, regardless of the output voltage.

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Originally Posted by drivesafe

Something is not quite right, unless you were it traffic, driving slowly which would mean your revs were low...

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It's in 'Park'

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Originally Posted by drivesafe

Hi Ferret, that is nothing more than a line on a page, it gives no actual voltage reading, just a line on a page.

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Well you should have the raw data by now. Scale the chart any way you like.

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Originally Posted by Ferret

Well you should have the raw data by now. Scale the chart any way you like.

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Thanks Ferret, will do.

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Originally Posted by Milton477

You are right Drivesafe, I shouldn't have to disconnect but my D4 charging system has it's own mind. My alternator is standard whatever that may be. The modern DC2DC pushes 50 amps into my van's LifeP04 batteries while drawing around 60 amps from the D4.

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Hi again Milton, you may have a load exceeding your alternator’s capacity, and what you are doing is probably your only option.

Can you post up full specs for you setup, like what isolator you have in the D4, and also what other accessories you have, such as driving lights, how many and what type.

Also, do you have any idea of your driving habits while towing?