MPP Charging Problem - Voltage Disagreement w/ BMS

[AmboCamper]

Hi all, I'm having an issue getting my 12v MPP All-In-One Unit (this guy) to charge my batteries.

First, the system: 12v 200ah battery - Aliexpress cells with an Overkill Solar BMS.
400w solar
40amp DC-DC alternator charger (renogy)
20 amp utility charger (part of the MPP)

The issue is that the MPP Unit won't charge the batteries at times, particularly when multiple charge sources are active.

I've found that the BMS and the MPP disagree about the battery voltage. The MPP unit reads the battery voltage as high when a charge source is connected, so it goes into float mode and won't charge the battery. I've checked the battery voltage at the posts with a multimeter and it agrees with the MPP's "high" voltage reading.

For example, right now my BMS is showing 13.1v and 50ah remaining. But the MPP unit is showing the battery voltage as 13.9. It's showing the "fully charged" battery symbol and the solid green lights indicating the battery is fully charged.

Not sure if this matters, but I have the MPP connected to my battery via positive and negative bus bars, which also serve as the connection point for my 12v fuse block and dc-dc charger. There are breakers on all these points. Could all of these connections be creating an issue? (like, the opposite of voltage drop?) Or is it more likely that the fault is with the BMS, because the voltage reading at the battery terminals is the same as the reading at the MPP?

If anyone else can shed some light on this, I would be extremely thankful.

 

[mikefitz]

You need measure voltages at different points in the system with the meter and report.
With the battery measure the voltage before and after the bms. You may be getting volt drops across breakers if they are ebay/amazon low cost units.

What may be occurring is bms shutdown of the charge path, measuring the volts across the bms with the meter will confirm.
It could be over volt cell / pack or temperature sensor has put the bms into protection mode.

Can you indicate the voltages set on the chargers , they maybe unsuitable for your battery.

A screen shot of the bms app would be useful as would a diagram and/picture of your system.

Mike

 

[realdouglasquaid]

Hi all, I'm having an issue getting my 12v MPP All-In-One Unit (this guy) to charge my batteries.

First, the system: 12v 200ah battery - Aliexpress cells with an Overkill Solar BMS.
400w solar
40amp DC-DC alternator charger (renogy)
20 amp utility charger (part of the MPP)

The issue is that the MPP Unit won't charge the batteries at times, particularly when multiple charge sources are active.

I've found that the BMS and the MPP disagree about the battery voltage. The MPP unit reads the battery voltage as high when a charge source is connected, so it goes into float mode and won't charge the battery. I've checked the battery voltage at the posts with a multimeter and it agrees with the MPP's "high" voltage reading.

For example, right now my BMS is showing 13.1v and 50ah remaining. But the MPP unit is showing the battery voltage as 13.9. It's showing the "fully charged" battery symbol and the solid green lights indicating the battery is fully charged.

Not sure if this matters, but I have the MPP connected to my battery via positive and negative bus bars, which also serve as the connection point for my 12v fuse block and dc-dc charger. There are breakers on all these points. Could all of these connections be creating an issue? (like, the opposite of voltage drop?) Or is it more likely that the fault is with the BMS, because the voltage reading at the battery terminals is the same as the reading at the MPP?

If anyone else can shed some light on this, I would be extremely thankful.

Did you figure this out? I seem to be having the same issue.