EDIT: CellLink Neo charging voltage 2-2.5V lower than car battery voltage

[Nigel]

I asked in the previous reply, but wouldn't a damaged/corroded wire or connector cause both amperage and voltage drops? The amperage draw on the CellLink Neo is stable during the first couple minutes of ignition.

I assume the amperage you are seeing is what the Neo is putting into the battery cells, and it will take what it needs from the car to achieve that, as long as there is enough voltage to be able to. So the amperage through the fuse at 13 volts would be rather more than the 9A at 15.1V into the cells...

Does this mean somewhere between the fusebox and the inline fuse, there is a corroded connector or damaged wire?

Seems you are losing a bit of voltage in several places and it all adds up to be too much loss.
So the question is really, what has got worse to take it over the limit and generate the error?

You could try cleaning and remaking the connections.
If you have used crimp connectors then you could try remaking them with new crimps and add some solder to ensure good connections.

When the car battery settles down to 13.3V after the first couple minutes,...

That is rather low, with a well charged battery I would expect it to settle down to around 13.8 across the battery terminals. 13.3 would be reasonable if the car battery is over half empty, and if you are using an Neo then the car battery should not be half empty.

I think you should explain why you only have 13.3 volts before touching anything...

Maybe a dying battery?
Maybe a dying alternator/in need of new brushes?
Maybe that is not measured across the battery terminals?
Maybe it is being heavily discharged by something?

 

[dvttipspe]

@Nigel

I have been measuring my car battery voltage during my commute for the past number of months, and I believe it has always been ~13.4V when idle. If the car has just been started, then idle voltage is ~14.8-15.1, but after a couple of minutes it always drops down to 13.4V. I have never had issues with ignition/lights dimming/instrument clutter problems, and resting car battery voltage after a week is 12.65V, so it seems like the alternator is working properly, at least for my make and model. Since the CellLink Neo issue, I installed a newer, higher capacity car battery that is also reading the same voltages.

When I rechecked the inline fuse voltage reading, I also rechecked the car voltage at the battery terminals, which was indeed 13.4V. Maybe there is something that is heavily discharging the battery as you mentioned, but it seems unrelated to the voltage drop seen at the CellLink Neo.

To further test the wiring, I used the cigarette plug adapter to test 5A charging of the CellLink Neo. In my car, there is a 1.0-1.3V lower reading on the CellLink Neo than the car battery.
I tested it with a separate vehicle, and the CellLink Neo only reads 0.3-0.5V lower. Based on this, I am leaning towards something other than the wiring being the issue.

I wish it was straightforward with alternator failure, but would it be the alternator if the car voltage is adequate/stable, but voltage measured on the device is low? It seems like the wiring is the issue, but the test with the plug adapter and two separate vehicles seems to say otherwise.

 

[Nigel]

I tested it with a separate vehicle, and the CellLink Neo only reads 0.3-0.5V lower.

So we know that it is not getting lost in the Neo, so it must be getting lost in the car wiring. It is perfectly possible if the car is using thin cables, or there is a bad contact somewhere.

and resting car battery voltage after a week is 12.65V

That is an almost full voltage.
So we can assume that there is no heavy discharge.

but after a couple of minutes it always drops down to 13.4V

This is the only thing that I see as wrong, it should be 13.8 or a little more.
However, if it has always been like that, then this is not the cause of the change.

Can you check if it is 13.4 with the Neo charging at 9A and also 13.4 when the Neo is not charging, or does it rise to 13.8 if you stop the Neo charging? (Which would be normal.)

when the CellLink Neo is set to draw 9A and charge via a hardwire in the fuse box, the charging voltage seen on the CellLink Neo is 2-2.5V lower than what the car battery is.

Which fuse do you have it plugged in to, and what is the original fuse rating?

I'm wondering if the fuse is switched when the engine is on by a relay, and maybe the relay contacts have worn through heavy use from the Neo and are now losing some voltage...

 

[Outbacknomad]

For a car stuffed full of electronics these days still under warranty the battery is too low & too high as per the voltages noted.

Next issue.

The wire resistance with a 3 metre cable, so 6 metres for positive and negative. The voltage drop with:

16awg 0.72 volts
14awg 0.45
12awg 0.28
10awg 0.18
8awg 0.11
6awg 0.07

Then any other wire in the circuit needs its resistance added to the equation.

 

[dvttipspe]

Can you check if it is 13.4 with the Neo charging at 9A and also 13.4 when the Neo is not charging, or does it rise to 13.8 if you stop the Neo charging? (Which would be normal.)

Which fuse do you have it plugged in to, and what is the original fuse rating?

I'm wondering if the fuse is switched when the engine is on by a relay, and maybe the relay contacts have worn through heavy use from the Neo and are now losing some voltage...

I have previously tested your first question, and the car voltage increases by 0.1V when I stop the 9A charging by disconnecting/turning off the CellLink Neo.
My fusebox has fuses with a small slot next to them (to allow for piggybacking?). I have always used this piggyback slot for the CellLink Neo, hence the inline 20A fuse. The original slot was beside the review mirror/seat ventilation/rear ventilation fuse (5 or 10A original fuse). I have noticed that the plastic around the slot has melted a bit, but I am unsure if it occurred before or after my low voltage issues.
Currently, I am using another piggyback slot beneath it. I figured the original slot had a bad contact point with the spade connector that was used, maybe it slipped out a bit, causing the melted plastic.
Here is picture for reference.

Edit: I guess in the end though, since using the same cigarette plug adapter in two cars shows a higher voltage drop with my car, how it was wired into the fuse box does not really matter.

 

[dvttipspe]

For a car stuffed full of electronics these days still under warranty the battery is too low & too high as per the voltages noted.

Next issue.

The wire resistance with a 3 metre cable, so 6 metres for positive and negative. The voltage drop with:

16awg 0.72 volts
14awg 0.45
12awg 0.28
10awg 0.18
8awg 0.11
6awg 0.07

Then any other wire in the circuit needs its resistance added to the equation.

The problem is that for the past 1-2 years there has been no issues with charging the CellLink Neo with the exact same setup. Only in the past few weeks did the current problem arise.
As I also mentioned to Nigel, I tested the CellLink Neo with a cigarette plug adapter in two different vehicles. The voltage drop is two times higher in my vehicle, hindering proper charging of the CellLink Neo.

 

[Outbacknomad]

Can you stick a car battery charger on the starter battery, so you have a fully charged large stable supply, while the car is not running, no need to take the battery out. Then connect the CellLink directly to the battery and measure the voltage at the CellLink end of the cable while it is charging, preferably from a reasonably discharged starting point.

This will rule out whether the CellLink has a problem. If it is ok, then it is the car.

 

[Mtrev]

I have previously tested your first question, and the car voltage increases by 0.1V when I stop the 9A charging by disconnecting/turning off the CellLink Neo.
My fusebox has fuses with a small slot next to them (to allow for piggybacking?). I have always used this piggyback slot for the CellLink Neo, hence the inline 20A fuse. The original slot was beside the review mirror/seat ventilation/rear ventilation fuse (5 or 10A original fuse). I have noticed that the plastic around the slot has melted a bit, but I am unsure if it occurred before or after my low voltage issues.
Currently, I am using another piggyback slot beneath it. I figured the original slot had a bad contact point with the spade connector that was used, maybe it slipped out a bit, causing the melted plastic.
Here is picture for reference.

Edit: I guess in the end though, since using the same cigarette plug adapter in two cars shows a higher voltage drop with my car, how it was wired into the fuse box does not really matter.

I’m guessing your car is a VW group car from that fuse box, the slots next to the fuse are additional fuses, that slot isn’t protected by the fuse next to it and is a different supply circuit to the fuse.
the melting does look like it has been hot probably due to high resistance as you suspect.

 

[Nigel]

Edit: I guess in the end though, since using the same cigarette plug adapter in two cars shows a higher voltage drop with my car, how it was wired into the fuse box does not really matter.

We still haven't located the cause of the main voltage drop, something is causing it, but it is hard to ask the right question and your answers appear a bit inconsistent, even though they may be accurate.

Can you check the Neo's earth connection? I know you said it was hard to access, but measuring the voltage between that earth point and the battery negative would be useful, it should be very close to zero when charging and when not charging.

Given that the issues seem to be with the vehicle, it might be sensible to consider powering the Neo from the battery instead of from the fuse box. You would need to run a cable to the battery, but it would eliminate the issues if you also have a good earth. If it needs switching then you can add a relay with the coil connected to the fuse box.

 

[dvttipspe]

We still haven't located the cause of the main voltage drop, something is causing it, but it is hard to ask the right question and your answers appear a bit inconsistent, even though they may be accurate.

My idea was to eliminate variables such as the aftermarket >3meter wire, inline fuse, ground connection, crimp connectors, potential piggyback fuse slot conditions, etc., by using the cigarette adapter plug adapter. This way we can ignore the custom ground wire connection, (dashcam installer tried 2 different points and said there are no issues with the quality of ground, which was also being used to ground OE components) and also test with the same cigarette plug adapter in two different vehicles.
As mentioned there is still a higher voltage drop in my vehicle, so my thought is that I can now focus on just the circuit that provides power to the cigarette port, if that makes sense?

Given that the issues seem to be with the vehicle, it might be sensible to consider powering the Neo from the battery instead of from the fuse box. You would need to run a cable to the battery, but it would eliminate the issues if you also have a good earth. If it needs switching then you can add a relay with the coil connected to the fuse box.

I like this idea, and I think by doing so it can eliminate the fuse box as the source of problems. Would I simply keep my current setup, but just move the charging wire into the clamp that attaches to the positive battery terminal? I will not add a relay just yet, as I want to see if there are still voltage issues.

 

[Nigel]

so my thought is that I can now focus on just the circuit that provides power to the cigarette port, if that makes sense?

While it does make sense, I'm not sure you have good access to the circuit to find out where the voltage loss is?

Would I simply keep my current setup, but just move the charging wire into the clamp that attaches to the positive battery terminal?

Essentially, yes, but I don't know the details of your battery installation so can't comment in detail.

For a permanent install, you do want to make a secure connection, it may be simpler to connect to the other end of the main battery cables, or to the under bonnet fuse box where there is quite likely to be a suitable screw terminal. For a temporary connection, simply sticking the end of the wire under the battery terminal clamp may work, depending on the car.