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iron-quail-ranch avatar image

Blue solar MPPT 150/70 with lithium

Hello, I recently upgraded from 12v SLA Batteries to 12v LifePo4 batteries from bigbattery.com.


My question: Is there a software/firmware upgrade that will allow me to select a lithium charging profile on the MPPT 150/70 so the lithium batteries are charged properly? Looks like the newer "smart solar" MPPT have a lithium profile.


Right now I have setup a "custom" charge profile that has absorb @ 14.4v and float @ 13.6v, no equalize. There is no option for bulk.


Thank you!

MPPT - Solar Charge Controller
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3 Answers
klim8skeptic avatar image
klim8skeptic answered ·

The OP might want to specify which model of bluesolar 150-70 they have.

The current plastic shell model, or the nla metal cased unit.

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seb71 avatar image
seb71 answered ·

The bulk stage is a constant current stage (in theory it is constant current stage, but in practice with solar chargers it only happens with a constant current if if you have enough sun to maintain a constant current; if not, it will use whatever current/power the PV array can generate). During this "bulk stage"/"constant current stage", as the battery is charged, the battery voltage will rise.

When the battery voltage reaches the value set for "Absorption voltage", the bulk stage (constant current stage) ends and the absorption stage (constant voltage stage) begins. During this absorption stage the voltage is kept constant and the current taken/"absorbed" by the battery will drop as the battery gets closer and closer to fully charged (this current drop is caused by the battery, not by the charger).

The absorption stage ends either based on time (certain duration you set) or based on the "tail current" (when the current taken by the battery drops under a certain threshold you set, the battery is considered to be fully charged and the charger wil end the absorption stage). This "tail current" is tricky to set correctly with solar chargers, because the current can drop bellow this current threshold value because you have a cloud shading the panels, not because the battery does not accept a higher current/power anymore.

When absorption stage ends, the Float stage begins and from now on the charger will maintain the "Float voltage" value (if there is still sun power).


For charging LiFePO4, you should never get over/above 3.6V per cell. You can limit the charging voltage even lower than that (such as 3.45V per cell), but this value depends on the battery you have (mainly if it has a BMS or not and if it has, what kind of BMS and how it can be set).

Float voltage value is somewhere in the 3.35V-3.375V range (cell voltage).


A "12V" LiFePO4 battery has 4 cells in series.


Note:

When discharging, you shoud not get under 3V (cell voltage).

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Alexandra avatar image
Alexandra answered ·

@Iron Quail Ranch

Bulk charge is the same as absorption charge as it is a constant voltage part of the charge cycle, where you are trying to raise the voltage of the bank to a target level.

Does your manufacturer recommended two different voltages there?

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Ok, I understand the charging cycles and have them set.


But my question is:. Is there a software/firmware upgrade for the Victron MPPT Blue Solar 150/70 charge controller that has lithium charging profiles?


Thank you!

If you have the latest version of VictronConnect installed than you have automatically the latest firmware and you have to install it to change settings. The current FW version for tht 150/70 isis 1.54.