Voltage doubles when battery charged and converter goes to no load conditions.

[Maplhgr]

I’m stumped..
With a single lithium battery when the converter fully charges battery the battery voltage immediately doubles to 27 volts. No solar connected. So the only two voltage sources are the battery itself and the charger (converter)

As soon as charging current goes to zero and the battery monitor reads 100% charged the voltage goes fron 14.7 volts to 27. Measured on battery bus, across battery terminals and on renology monitor. Turn off Qc power to charger and voltage remains high til some discharge has occurred. Assume due to a capacitor.

At wits end

 

[Richpatty]

Will need more info.... What brand/type of battery? What model/type of charger? Has this always been t his way or did it just start? What kind of rv?

Have you made sure the charger is not set to 24 volts?

Let us know.

 

[Rich W.]

Have you measured it independently with a multi-meter with the battery disconnected?

 

[Maplhgr]

Will need more info.... What brand/type of battery? What model/type of charger? Has this always been t his way or did it just start? What kind of rv?

Have you made sure the charger is not set to 24 volts?

Let us know.

KUBOKA LiFePO4 Battery 12V 100AH Lithium Battery - Built-in 100A BMS

2020 Intech flyer Persue

Progressive dynamics 4135 converter. New board with lithium dip switch for lithium batteries.

This is a brand new card recieved today.. the first I bought was to upgrade to lithium and exhibited this same behavior ( PD4135CSV) and progressive dynamics replaced under warranty.

I just installed a renology battery monitor so if it did it before I probably wouldn’t have seen it. Bought this trailer just before the pandemic and getting ready for maiden voyage.

 

[Maplhgr]

KUBOKA LiFePO4 Battery 12V 100AH Lithium Battery - Built-in 100A BMS

2020 Intech flyer Persue

Progressive dynamics 4135 converter. New board with lithium dip switch for lithium batteries.

This is a brand new card recieved today.. the first I bought was to upgrade to lithium and exhibited this same behavior ( PD4135CSV) and progressive dynamics replaced under warranty.

I just installed a renology battery monitor so if it did it before I probably wouldn’t have seen it. Bought this trailer just before the pandemic and getting ready for maiden voyage.

only 5 wires involved to replace card and I took photos of “as found” configuration as I always do.

 

[Maplhgr]

Have you measured it independently with a multi-meter with the battery disconnected?

Yes. With battery switch off and anti reverse fuse pulled charger indicates 27 volts. No load condition. This is test progressive dynamics tech had ne perform before warranty replacement..

Btw.. curiously the replacement board serial number is identical except for last number which is only 4 digits higher…
Bad batch?

This is a 12 volt converter only. Lithium switch on board boosts output to a nominal 14.6 volts per manual.

 

[Kevin D Pem]

So the charger is solar controller I assume.
Likely the controller automatically chooses system voltage.
Maybe the battery is disconnecting via BMS leaving the controller without a system reference.
Set the controller to lithium, and the charge constant voltage/constant current to the battery suggested voltage.
That should keep the BMS from cutting out. This is important to keep a reference voltage for the controller.

If you still have the problem consider a 12v super capacitor in parallel with the battery.

 

[Maplhgr]

So the charger is solar controller I assume.
Likely the controller automatically chooses system voltage.
Maybe the battery is disconnecting via BMS leaving the controller without a system reference.
Set the controller to lithium, and the charge constant voltage/constant current to the battery suggested voltage.
That should keep the BMS from cutting out. This is important to keep a reference voltage for the controller.

If you still have the problem consider a 12v super capacitor in parallel with the battery.

Not a. Solar controller. Built in distribution center/converter. The battery is not disconnecting. 27 volts can be read directly on terminals….which I now understand is probably causing bms to actually disconnect battery internally… new to bms….

 

[Kevin D Pem]

Not a. Solar controller. Built in distribution center/converter. The battery is not disconnecting. 27 volts can be read directly on terminals….which I now understand is probably causing bms to actually disconnect battery internally… new to bms….

So the stand alone battery (disconnected) shows 27?
A 12v battery does not have enough cells to offer a 24v supply voltage, there is no physical way. Put the battery number up please.

 

[Maplhgr]

So the charger is solar controller I assume.
Likely the controller automatically chooses system voltage.
Maybe the battery is disconnecting via BMS leaving the controller without a system reference.
Set the controller to lithium, and the charge constant voltage/constant current to the battery suggested voltage.
That should keep the BMS from cutting out. This is important to keep a reference voltage for the controller.

If you still have the problem consider a 12v super capacitor in parallel with the battery.