Charge 4S Li-ION Overkill Solar BMS directly with 60W solar panel

pinchio

New Member
Joined
Apr 13, 2020
Messages
24
Hi, I have a 4S Li-ion BMS powering my 100Ah pack. I also have a portable solar panel that I want to connect directly to the battery pack to charge it without using an external MPPT charge controller to simplify my setup. With the specs listed below should I worry about damaging the BMS and do I need an external solar charge controller (MPPT or other).

MobiSolar 60W-ETFE-B Foldable Solar Panel Specs

Peak Power 60W
Cell Type Monocrystaline
Cell Efficiency 21.4%
Max Power Current (Impp) 2.87A
Max Power Voltage (Vmpp) 20.90V
Open Circuit Voltage (Voc) 24.70V
Short Circuit Current (Isc) 3.38A
Max System Voltage 100V


4S Li-Ion BMS
 

time2roll

Photon Sorcerer
Joined
Mar 20, 2021
Messages
3,580
Technically it will work but I do not recommend having the BMS as the controller. The BMS will shut down the battery every time it reaches full charge.
At least get a low price PWM controller.
 

Rocketman

Solar Addict
Joined
Sep 27, 2020
Messages
710
Also, if something were to happen to the bms and it didn’t shut down - that single panels voltage is too high for full batteries- it would overcharge them.
At least get a low price PWM controller.
 

AE4KR

Ham Radio Tinkerer
Joined
Jun 2, 2020
Messages
63
Location
Near Salt Lake City, UT
That panel only makes 60 watts with an MPPT charge controller. Without a controller or a PWM, the battery will pull the panel's output voltage down to the battery voltage, and the panel will provide in the neighborhood of 3 amps. So in your application it's now a 35 - 45-watt panel.

If you have a way to monitor battery charge voltage and manually disconnect the panel when it reaches that voltage, (with no time in constant-voltage mode,) you'll never be able to charge the battery past about 90%. That's not a bad thing for battery life, but be sure you're willing to accept the limitation on both useable battery capacity and useable panel capacity.

An MPPT charge controller will convert the panel's 20.97 volts at 2.87 amps to charge the battery at 13.6 volts at 4.3 amps (vs. about 3 amps with no controller,) charging faster, and will hold the battery at its max charge voltage until the charge current drops to about 10 amps, maximizing the effectiveness of both battery and panel.
 
Last edited:

pierre

Somewhere down South
Joined
Dec 21, 2019
Messages
903
Also , without a charge controller e.g. MPPT , you will lose out on the max power point tracking optomization.
 
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