Voltage drop between MidNite classic 200 and batteries

[Kalvin]

Good day,

We have a MidNite classic 200 connected to a 1kw solar panel array, and the wattage measured from the panels match the wattage displayed on the MidNite classic so between charger and panels there seems to be no issue. The issue we are encountering is that when there is enough wattage from the solar panels and the solar charger (the MidNite classic 200) is charging at higher than 30A there seems to be a .3V difference between what the voltage is at the battery output terminals inside the classic 200 and the batteries themselves. We understand that this is due to voltage drop over the cable however we cannot install a thicker cable than 35mm^2 as there is insufficient space inside the classic, is there any setting that i can try adjust to attempt to solve my problem?

Another problem we encountered was the Ethernet port has seemly stopped responding (when a lan cable, crossover or straight cable, gets plugged into two devices there is no activity lights). The situation to which this could've occurred is a mystery as we had a cat5e cable plugged in over night whilst the system was powered down (the connection was tested that day and it all worked) and then the day after the lan port wouldn't respond to anything. I have checked the 'net' settings and the web server is still set to enabled and i have rebooted the system and updated it as a troubleshooting attempt to no success. any suggestions as to how i can try test if this problem is on the hardware or software of the machine?

TL,DR:
1. Have a 35mm^2 cable between charger and batteries and getting voltage drop at high amperage only.
2. Ethernet port seems to be unresponsive.

Hope the problems where described to sufficient detail, if not please ask.

Thanks!
Hope

[ClassicCrazy]

What voltage is  your battery ? 
How long are the cables where the voltage drop is ?
A design with 2 % voltage drop is acceptable.  Some design it higher % .
So if you have 24v  and .3v drop - if I did my math correct that is only 1.25 % voltage drop.

Not sure about your network.
You get no communications at all with it ? If you plug it into router with DHCP you don't see it show up on router list ?
Are you getting no communications with Mymidite webpage or with Local Status App or both ?
The Local Status App will look for it  on network - you get nothing showing up via that ?

Larry

[dgd]

How are you measuring the voltage at both locations? Using a decently accurate fluke meter?
Hopefully not using the voltage reading from the Classic's display and a meter at the battery
Also that 35mm2 cable, you should double check that it's tight into the Classic's terminal block as a multi stranded cable will get loose due to creepage of the wire strands. It should be checked reasonably often. I'm surprised you can get 35mm2 cable into the terminal block as the largest cable I can squeeze in is #4, that is 21mm2

Dgd

[TomW]

As far as larger cable size not fitting The Classic you can use a short length of cable that fits from The Classic to a terminal block that can accept larger cable to complete the run to the battery bank.

First thing I would do is use a quality meter  as DGD suggested to check the actual voltage at the input on The Classic and at the battery terminals and adjust as needed from the tweaks menu (I think).

Are you aware you can calibrate The Classic's idea of what the voltage on it's input is?

Just some general thoughts.

Tom

[Kalvin]

Good day,

Thanks for all the replies.

My battery voltage is 12V, and the length of the longest cable (as batteries are positioned on two sides of the car for weight balancing) is approx 5m.

The network side of things i have tested further and i do believe the port itself is not working on the classic so RIP being able to adjust the system and monitor it externally, however we are making a plan to put an external screen plugging it into the original screen port.

The manner in which i observed the voltage drop was as such, parked the van in full sunlight on a slight hill to obtain close to 700 watts of power, the batteries were drained previously using and inverter and a kettle. Then as the solar charger tried to reach the targeted 14.7 V (The AGM batteries im using require such a charge) i measured teh voltage at both batteries (they are in parallel) and compared that to my control system i have made with current and voltage measuring circuits for both batteries and solar system. the solar systems voltage output that it displays was then checked at their output terminal using the same voltage meter (the lid was off so i was able to probe with gloves on) and the voltage on the screen was accurate to those terminals however there was a difference of .3 volts between those terminals and the batteries.

the 35mm^2 cable was fitted into the terminals using pin lugs to convert the 35mm^2 cable into something that i could fit into the terminal block and so a loose connection at the terminal is highly unlikely however i will check that out once i get back into later this week.

Tom my worry about setting a fixed offset on the voltage is that if im charging at low amperage there is no voltage drop so inevitably the solar charger will try reach a voltage of 15v which will damage my batteries (I do plan on testing my theory by trying to obtain a steady low amperage input from the solar charger into the batteries and then observe if there is indeed no voltage drop under those circumstances).

Thanks for all the inputs and i did a test drive last weekend with the system and the solar charger charge the batteries to full capacity each time however a correct charge voltage of 14.7v was never reached which worries me, but i shall ake a closer look this coming weekend.

Thanks
Kalvin.

[dgd]

Kalvin,
Ok, now you have given us some more info there may be other issue causing this perceived voltage drop. First, you are not using a quality, hence properly calibrated DVM such as a Fluke. Instead you have 3 separate voltage/current sensors, you have constructed these?, one on the Classic and one on each battery?
So are the interconnect cables between Classic and the two batteries all the same length and cable size? Its a bit suspicious when you say the longest cable is 5m, so what are the rest? All different lengths?
You could try disconnecting one battery and see if you still see the voltage drop as unbalanced batteries could be a problem. Different length cables could cause unbalanced charging.
Some photos of your wiring and batteries could be useful
Dgd