DC to DC Charger with MPPT only charging batteries to 50%

[jtown]

I recently installed my electrical system which has the Renogy DC to DC charger with MPPT 50A, two Renogy 170Ah lithium iron batteries, and the Renogy 500A battery monitor with a shunt.

The DC to DC charger with MPPT works fine - no issues getting a charge from both solar and the alternator. The battery monitor seems to work as well, it detects loads that I’m using and shows when I’m charging.

However, the DC to DC charger with MPPT seems to only detect one of my batteries as it will only charge from my alternator or the solar PVs up to 48% or 49% - as seen on the battery monitor. My batteries are connected in parallel. I’ve set the battery type on the DC to DC charger with MPPT to Lithium iron as well as on the Bluetooth mode of the battery monitor and setting it to 340Ah. Is this an issue that the DC to DC charger with MPPT isn’t detecting both batteries? Or is there something I’m doing wrong in setting up the battery monitor?

Any help is greatly appreciated. Thanks!

 

[TacomaJoe]

What are you using to determine that the batteries are only charged to 48-49%? The charger doesn't know, or care, how many batteries you have.

Your monitor may need an initial setup. On mine (AiLi) I charge the batteries fully then set the SOC to 100%. From there the monitor tracks charge/discharge currents. The monitor knows the battery capacity and uses that value to determine the % value.

 

[mikefitz]

Possible issues,
a) the shunt is in series with only one of the batteries, the negatives of each battery connect to shunt B-, every other negative connects to shunt P-.
b) the settings in setup for the shunt are wrong, see page 5 of manual.
CAP set to 340 ,
HIGH V set to 0.1 volts lower than the charger absorbtion, boost, volts
LOW V set to BMS low volts protection limit, typically 10.5 volts
c) one of the Renogy batteries is in protection mode or asleep. Ensure each battery can individually supply current to a load, and each battery can be charged individually. Before reconnecting in parallel ensure the voltages are similar.
d) the cell inbalance in one of the batteries may cause BMS protection to disable charge in that battery. Lowering the charge voltage is advised by Renogy if this is the case, down in 0.1 volt steps to 13.8 volts if necessary.

Mike

 

[jtown]

What are you using to determine that the batteries are only charged to 48-49%? The charger doesn't know, or care, how many batteries you have.

Your monitor may need an initial setup. On mine (AiLi) I charge the batteries fully then set the SOC to 100%. From there the monitor tracks charge/discharge currents. The monitor knows the battery capacity and uses that value to determine the % value.

The battery monitor shows that the batteries are only charged to 48-49%.

Where’s the setup for this battery monitor? Doesn’t seem like much setup other than setting the Ah?

 

[jtown]

Possible issues,
a) the shunt is in series with only one of the batteries, the negatives of each battery connect to shunt B-, every other negative connects to shunt P-.
b) the settings in setup for the shunt are wrong, see page 5 of manual.
CAP set to 340 ,
HIGH V set to 0.1 volts lower than the charger absorbtion, boost, volts
LOW V set to BMS low volts protection limit, typically 10.5 volts
c) one of the Renogy batteries is in protection mode or asleep. Ensure each battery can individually supply current to a load, and each battery can be charged individually. Before reconnecting in parallel ensure the voltages are similar.
d) the cell inbalance in one of the batteries may cause BMS protection to disable charge in that battery. Lowering the charge voltage is advised by Renogy if this is the case, down in 0.1 volt steps to 13.8 volts if necessary.

Mike

thanks for your help! I didn’t set the CAP to 100% after fully charging them. Seems to work all good now.