450/100 MPPT Overcharging

Q&A and troubleshooting
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1

A customer of mine has a 450/100 MPPT that is over charging the batteries. Charge voltage is set to 56V and it just sails right past, up to 57.5V at the highest.
There is no Bluetooth connection to any VE.Smart network
No VE.CAN or VE.Direct
Only a temperature probe connected to the Orange plug.

ReBulk offset is 0.4V
Absorption duration is fixed
Absorption time is 2hrs
tail current disabled.
Equalisation disabled
Temperature compensation disabled

Also charging the battery is a Selectronic SP Pro with an AC coupled Fronius inverter.
Batteries are Powerplus Lithium (no comms)

2

Hi @dbx160,
Can you please post some screenshots of the history section of VictronConnect when connected to the MPPT RS, and any other source of battery voltage data at the same time?

3

Are you sure it is the MPPT RS and not ac charging from the Fronius through the inverters?

4

Hi @dbx160,

Do you get this resolved?

5

Hi Guy, I have the same issue with my MTTP 450/200. I have been using it for about a year and just randomly today it starts sailing past the Float Voltage.

I have external Xantrex inverters/ac chargers but I ruled them out because the problem continues when i turn off the Xantrex chargers but the problem stops when i turn off the MTTP.

6

Hi @Aaron_H_Martin,

Turning off the MPPT will disable the MPPTs over voltage alarm warnings, but that doesn’t mean that the MPPT is the cause of those warnings.

Like turning off the smoke detector when the toast is burning.

Once you turn off the Xantrex the battery voltage might still be over the limit for the MPPT even if no further power is being added to the battery.

Like if the room is still smokey from the burned toast even after turning off the toaster, confirming it must still be the smoke detector.

What are you using to control the Xantrex inverters?

1 Like
7

Thanks for your prompt reply. I understand your explanation and your reference to the toaster but i wasn’t really referring to just the alarm. I let let the battery discharge for a while with both charges on off. Then after turning on only the MTTP charger, over a while the over-voltage error came back. I let the battery discharge again and turned on only the Xantrex chargers but the error never came back. I tried twice more with the MTTP but it kept over-charging.

That was yesterday. By turning off the MTTP i was referring to digitally turning off the switch from the mobile app. Later last night I physically turned off the MTTP with the switch on the unit and also reduced the Float Voltage setting on the MTTP. Now today it seems to working properly again and stopping charging when the Float Voltage is reached.

We will see if the problem returns. If not i would like to increase the Float voltage setting again.

8

I would disconnect the temp sensor.

What does the battery voltage reach without the mppt there? Is it the same voltage as what is triggering the overcharge error?

The screen shot requested by Guy Stewart is a needed piece of information.