# Current flowing through charger while driving



## CroDriver (Jan 8, 2009)

Hi guys.

We have a test bench for battery-packs with a Manzanita 75 Amp charger and a Soliton for discharging the packs.

This week we have calibrated a PDU (Power Distribution Unit - a system with integrated current measuring for different systems in the vehicle) and we noticed a strange thing. 

(Disclaimer: I haven't performed those tests personally - my guys from the electronics engineering did so I'm just posting here what they told me - so I might say something which is not correct)

If the charger is connected to the battery-pack while discharging the battery, there is A LOT of current flowing through the charger (because of the capacitors on the output side). It is almost impossible to measure it correctly except with an Oscilloscope because the current is depending on the controller PWM. So the cables of the charger get very hot and you loose efficiency.

We don't use Manzanita chargers or Soliton controllers in our cars so we can't check that in the vehicles, and we didn't notice this before when we did use Manzanita. 

This was the first time we noticed it on the bench because the PDU measures the current on the charger separately so we noticed a strange current on the charger-sensor while discharging the battery through the controller. 

Did anyone else notice that? Maybe someone could check if the charger-cables get hot while driving?

So we strongly recommend to disconnect the charger from the battery while driving. 

I'll ask my guys for more info on this on Monday and post it if I have time.


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## rwaudio (May 22, 2008)

I just finished assembling the EMW 10kW charger and there is a diode (or relay if you go that route) that keeps that from happening. If going the diode route it may be important to sense the voltage after the diode drop depending on required accuracy.


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## Tesseract (Sep 27, 2008)

CroDriver said:


> ...
> (Disclaimer: I haven't performed those tests personally - my guys from the electronics engineering did so I'm just posting here what they told me - so I might say something which is not correct)....


Ripple from the controller's normal operation can result in reactive current flow through any capacitors also connected in parallel with the controller's battery terminals. Ie - the input capacitors of a dc/dc converter or the output capacitors of the charger. This is mentioned in the Soliton owner's manual, btw.

These are EEs, you say?


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## MalcolmB (Jun 10, 2008)

rwaudio said:


> I just finished assembling the EMW 10kW charger and there is a diode (or relay if you go that route) that keeps that from happening. If going the diode route it may be important to sense the voltage after the diode drop depending on required accuracy.


Could you tell me the rating of the diode? I want to add some protection to the Curtis chargers I'm using. They're designed for stationary use, but I'll be installing them in the car, permanently connected to the pack, so I'd appreciate any guidance on suitable safety margins for current and voltage. I realise that heat sinking is important. I'd prefer not to disconnect the charger as I think that would require a precharge for the output capacitors.


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## Otmar (Dec 4, 2008)

Controllers with larger input filter capacitors such as the Zilla do not have this issue. If you are concerned about it check with your controller manufacturer.


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