Battery support unit

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morski

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What brand/ model etc of battery support unit is everyone using if you use it? Some diagnostic sessions take a good amount of time especially if the car has quite a few ecu's and or if im programming either with VCDS or online with ODIS
Looking at a Gysflash the 50A version and seen the bosch units which are twice the price around £1200+vat here also CTEK make one and again around the £1000 mark
Is a 50A supply sufficient?
 
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Bruce

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Ross-Tech has had good experience with chargers from Xantrex. Not sure if we are using the 20A or the 40A charger. These have been in service at trade fairs and in the office for long duty - often keeping a car alive for hours. Sure, we turn off as many consumers as we can to keep the car alive, but to the best of my knowledge, we have never run a battery down with these. Cars tied to our docking station for program testing are run for days on the charger. I believe our chargers have been used for 10+ years now. While they may not be cheap, they are also not £1000.

I'm sure there are other choices. There are some who say only the Bosch chargers are good enough.

As you are in the UK, one thing that needs to be checked: the negative lead should be at ground potential or you may end up letting the secret gray smoke out of the protection circuits in the interface should you plug the PC and connect via USB. So far this is a phenomena that only happens in the 230v 50 cycle community where the laptop and the battery charger are not referenced to the same ground (or not referenced at all.) Do make sure the battery charger has a ground reference. Do make certain the PC does also.

(Besides, who would want to work on a metal object that could potentially be floating at 230V above earth? Safety concerns anyone?)
 
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mattylondon

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Sorry to go off topic, but Bruce you mentioned "So far this is a phenomena that only happens in the 230v 50 cycle community where the laptop and the battery charger are not referenced to the same ground", is this due to which type of earthing / grounding system is used? Either TN-S, TN-C, TN-C-S, TT or IT? Or something else?
 
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Uwe

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Not sure if we are using the 20A
20A. We've found that sufficient for general diagnostics if one makes the effort to turn off non-essential consumers (lights, HVAC, infotainment, etc). Beware however that many really cheaper chargers don't produce the current they claim, or they have poor voltage regulation and will end up setting over-voltage codes if left connected to the vehicle for a length of time when there's no load.

I do not think it's necessary to spend £1000 to get an adequate charger; a few hundred will likely do, but anything under 100 is likely junk.

-Uwe-
 
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Bruce

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I've not had my hands on a unit that has caused the issue but we know it has happened. It's the only possibility for the type of failures reported. Having reviewed the setups, I fear that it may be the laptop supplies that cause the faults. If a system is connected TN-S, TN-C, TN-C-S, TT - I can't see a fail if both are referenced to the same system. But, if not.. a voltage may appear on the grounds and the interface cannot hack the large potential. My suggestion to most Pros is to run the lap top from a battery. We put protection in place and were surprised that still there is configuration that blows the protection devices. We do not know what that configuration might be.

Do keep in mind, my electrical engineering experience is in the USA mostly. The configurations in the UK and in Europe are different but I do not know the nuances.
 
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DrPeter

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morski

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Thanks for the replies. I rang a diagnostic equipment supplier earlier today and he was suggesting a 100A unit which i thought was way overkill. Was thinking around 50A would suffice. I have a CTEK 10A unit but its no where sufficient and barely keeps up. I think some figures are over inflated like Uwe mentioned
I always have all unwanted consumers switched off so not to cause any unnecessary battery drain.
@Bruce; i have heard about this issue with laptops being plugged in causing mains issue but dint know it was a 240v 'thing'. Could it be a one off case where a laptop was/is plugged into the mains and it developed an internal fault causing mains leakage back towards the usb port and hence to the vehicle? Or am i on a different page altogether?
Some of the laptops we have use the 'figure 8' power cable ie live & neutral and some higher power ones use 3 pin which has the earth/ground
 
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Uwe

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i have heard about this issue with laptops being plugged in causing mains issue but dint know it was a 240v 'thing'. Could it be a one off case where a laptop was/is plugged into the mains and it developed an internal fault causing mains leakage back towards the usb port and hence to the vehicle? Or am i on a different page altogether?
We see it more in 230V markets than in 120V markets, but I don't think it's exclusively a 230V or 50Hz thing.

Let me see if I can explain this in detail:

A car by itself is intrinsically "floating"; it has no ground reference because the only contact it has with ground is through its tires, which are quite high in resistance. This may change when a charger is attached. Now there's at least the possibility that the charger will give the car low resistance connection to something external. If so, we hope that reference is earth/ground.

A laptop by itself is also floating. It's air-gapped and running from its internal battery. But when you use an external power supply (or if you're using a "desktop" PC that has no battery), there's a good chance that the computer's "ground" will have a low-resistance connection to something external; hopefully earth/ground.

When both the car's ground and the computer's ground have low-resistance paths to something external, it is critical that the external things are at the same voltage potential. If they are at different potentials and you connect something (like a diagnostic interface) between the car and the computer current will flow. If the potential difference is substantial, the current flowing will be too and may cause damage. This is called a ground loop.

In the real world of our experience, it occurs most often when someone uses a cheap 12V power adapter for their laptop that incorrectly puts the laptop's ground at some DC potential different than the car's ground. See this ancient page on our site. However, we've also seen it at least once with a cheap charger and a computer that was plugged into an AC outlet, and that was in Canada (120V/60Hz).

I suspect the only reason we see this more in 230V markets is that people there (especially east of the old iron curtain) tend to buy cheap chargers.

-Uwe-
 
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morski

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Managed to get a GYSFlash unit. Planned to get the 50A version but found a 100A version for only £50 more so thought sod it and at least im covered.
Has a Diagnostic mode where i can select the voltage i require and it will regulate the current according to demand. I assume i can safely set it to 14.5V?
Also has a Power supply mode which is in the advanced menu where it works as a stabilised power supply with regulated voltage and adjustable maximum current- i dont think i will need this mode
 
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morski

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I had a 2018 RS4 in last week and during the scan the car was showing a charging voltage of 15.05V with the engine running and obviously no BSU attached. It seemed too high when i noticed it.
 
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PetrolDave

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I had a 2018 RS4 in last week and during the scan the car was showing a charging voltage of 15.05V with the engine running and obviously no BSU attached. It seemed too high when i noticed it.
Was it during the recent cold spell? Maximum allowed charging voltage changes with temperature.

batterytemperaturewithcharging.jpg
 
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morski

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Yes it was when the car was outside and quite nippy here so i guess it was allowable
 
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morski

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Just some info... Running diagnostics on a 2017 RS6 last night inside the garage so it was quite warm in there and had the BSU connected. Set to 14.5V and with ignition switch on the current reading peaked at 44A and then settled at 23A with all ancillaries switched off. Thats with the 100A BSU. Dont think a 30A would suffice if the initial surge is higher than the rated Ampage of the BSU. Would it?
 
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Uwe

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Dont think a 30A would suffice if the initial surge is higher than the rated Ampage of the BSU. Would it?
Sure it would. The initial "surge" is due to the battery being less than fully charged and thus willing to accept a bunch of coulombs. A 30A unit would just supply those coulombs more slowly, and would sit at 30A for however long it took the battery to be fully charged before also settling on 23A.

-Uwe-
 

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Personally I have a Ring 50A RSCPR50 which is a multimode charger and can operate a BSU, the voltage when in Battery Support mode is a solid 13.8 volts with current jumpoing around depending on what consumers are operating (e.g. electric tailgate which always seems to need to be opened to retrieve random tools or other stuff !!)

Not cheap at £300 but seems to do the job
 
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