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bms vs charge controller vs 12v vs 48v

rockwind1

Natural selection intervention specialist
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Nov 19, 2020
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if i buy a quality charge controller,, why do i need a bms,( assuming i build a battery, which i am not going to do) just wondering what the bms does when also using a charge controller,,

also, on a rv set up, which i think i will start with,, what is the advantage of a 48v battery set up vs a 12v battery set up

some forums are suggesting that the 48v has some advantages, but the reasons were vague.

i'v got a big roof and i boondock alot,, i was just going to max out the roof,

i am leaning towards 2 or 3 250-300ah batteries

like if a panel puts out 18v,, will that cook a lithium battery with a bms?

are the bms's that have bluetooth more desirable? does the charge controller have blue tooth?
 
if i buy a quality charge controller,, why do i need a bms,( assuming i build a battery, which i am not going to do) just wondering what the bms does when also using a charge controller
A BMS (battery management system) helps ensure the individual cells of a battery are kept in balance. It also helps protect the cells from under and over voltage. If you buy a LiFePO₄ battery it will have a BMS inside. If you use lead acid type batteries there will not be a BMS.

A solar charge controller takes power from solar panels and it converts it into power that can charge batteries.

The job of a battery's BMS and the job of a solar charge controller are completely separate and have nothing to do with each other. A LiFePO₄ battery needs a BMS whether you use a charge controller or not. A charge controller can be used with lots of different types of batteries, many of which (such as lead acid) that make no use of a BMS.

what is the advantage of a 48v battery set up vs a 12v battery set up
Higher voltage means lower amperage which in turn means smaller wires and smaller fuses/breakers. Lower amperage means you can support higher wattage inverters. For example, a 2000W inverter on a 12V system means 200A. The same inverter on a 24V system means 100A and on a 48V system it is only 50A. Or looking at this another way, the same 200A on a 24V system means a 4000W inverter or on a 48V system it means an 8000W inverter. Same applies to solar power. A 50A charge controller at 12V supports 600W of solar. On 24V you can have 1200W and on 48V you can have 2400W.

i'v got a big roof and i boondock alot,, i was just going to max out the roof,

i am leaning towards 2 or 3 250-300ah batteries
Do a proper energy audit so you know what you really need. See:


like if a panel puts out 18v,, will that cook a lithium battery with a bms?
A BMS is irrelevant for this. The solar charge controller will take the power from the panels, regardless of the panel voltage, and convert that power into the needed charge voltage appropriate to your batteries.

are the bms's that have bluetooth more desirable?
If you build your own battery then you probably want Bluetooth on the BMS. If you buy a pre-built battery then getting one that has a Bluetooth enabled BMS is only useful if you are the type of person that likes to see the nitty gritty details of what is going on inside the battery's cells. My batteries have a BMS without Bluetooth and they work just fine.

does the charge controller have blue tooth?
It depends on which charge controller you buy. Many do have Bluetooth to allow you to connect to it using a smart phone app. This typically lets you see the current state of the charge controller and to setup its configuration.
 
Battery Management System (BMS) has many protections for the battery that the charge controller does not. Protection at the cell level for both high and low voltage. Temperature protection for both high and low. BMS also keeps the cells balanced on charge level. If the BMS has BT it should transmit charge level to your phone, a big benefit and could save from buying a monitor.

The system will need a solar controller AND a BMS.

Many people go 24 and 48 volts. Especially if a large inverter (3000+ watts) is installed. The current can go well over 200 amps at 12v. I installed 2000w inverter and stuck with 12v and all works just fine. The higher the voltage the lower the current. 2x voltage = half the amps. Same energy but smaller wire and fuses. Many functions on an RV are 12v related so boosting or dropping voltage is a complication but certainly doable.

Yes some controllers also have BT connection. Although once set there should be little to no reason to look at it. Unless tons of gadgets seems like a good thing.
 
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