We're connecting two 24 volt Tesla batteries to 2 LG panels to have some off-grid power. Do we need a BP 220 for each battery or will one do for both?
asked
How Many BPs Do I Need?
As @Justin Cook already wrote:
Please don't use lithium batteries without a properly designed BMS system with cut-off protection (shunt-trip or relay) so you have a double protection.
As you write you're a novice in this area, please make sure someone is -very- knowledgeable to do this project for you. Or use a supported and proven safe alternative.
Tesla battery modules are great, but they need proper handling, because otherwise they can be great danger! they will burn / explode violently when overcharged for example. And overcharging can happen without exceeding total pack voltage limits (when a module is out of balance).
The BMS system has to monitor all cell-groups and has to be able to disconnect the modules when charging / discharging goes beyond safe limits for whatever reasons.
There are a couple of good BMS options available, but all are for experienced users and require deep electrical and software knowledge. (therefore we cannot recommend BMS x or y)
Yes, I do know this, am aware of the dangers, want to set it up properly, am proceeding with caution. We'd like to be pointed toward the best BMS options. I am working with a very experienced electrician.
I respect these strong positions from Victron regarding the benefits of a BMS but I would appreciate some supporting data. Maybe take some real world examples to derive some conclusions based upon probability analysis?
All batteries introduce risk including ones with on board BMS. so what is the quantifiable difference? I"m really curious
2 (in words: two) LG Panels means a (in words: one) small MPPT will be enough. If you provide specs or model of the LG panels, I can tell you which one.
Here's what we have so far:
Two Tesla Battery Modules 24V 250Ah 5.2 kWh 444 Panasonic 18650 Cells
MPP SOLAR Hybrid 2400w Pure Sine Wave Power Inverter with mppt Solar Charger 80A DC 24V AC Output 110V 120V with 60A Utility Charger 50HZ or 60HZ
Two of these panels: LG340n1c-v5 340w neon n2 60 cell
Nominal Maximum Power: 340 Watts
MPP Voltage: 34.50 Volts
MPP Current: 9.86 Amps
Open Circuit Voltage: 41.10 Volts
Short Circuit Voltage: 10.53 Volts
Module Efficiency: 19.80%
You're saying we don't need external battery protection other than what the Inverter provides....?
We're running the off-grid system to a 24 volt freezer and would like to make a charging station and some nominal lighting.
I'm very new to this (don't understand electricity at all!). I'm working with an older, retired electrician who is quite skilled but this is a new application for him. Any direction very appreciated!
@BonnieLinden, are you asking about the BP (BatteryProtect) or the MPPT (solar charge controller)? A BatteryProtect is unidirectional in operation only, so it would be connected to a DC load side only, and would not be relevant to your PV panels.
Hi Justin, I'm asking about the BP and wondering if each of these batteries needs its own BatteryProtect.
Two Tesla Battery Modules 24V 250Ah 5.2 kWh 444 Panasonic 18650 Cells
Aren't the batteries being protected from too much possible current from the solar panels? Doesn't the DC come from the panels?
We have two of these panels: LG340n1c-v5 340w neon n2 60 cell
Nominal Maximum Power: 340 Watts
MPP Voltage: 34.50 Volts
MPP Current: 9.86 Amps
Open Circuit Voltage: 41.10 Volts
Short Circuit Voltage: 10.53 Volts
Module Efficiency: 19.80%
We have this charge controller: MPP SOLAR Hybrid 2400w Pure Sine Wave Power Inverter with mppt Solar Charger 80A DC 24V AC Output 110V 120V with 60A Utility Charger 50HZ or 60HZ
Sorry, I'm a total novice, don't understand electricity at all. But I'm willing to learn! The installation is at my house so I should understand it as well as possible. Your elucidations welcome.
