Questions tagged [bms]

A battery management system (BMS) is any electronic system that manages a rechargeable battery (cell or battery pack)

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Can't find formula to calculate resistor values for a BQ34Z100

I am designing a BMS board using the BQ34Z10 fuel gauge IC. From the datasheet BQ34Z100 datasheet figure 8-3 I am unable to figure out how to calculate values for R2,R3,R4. I am designing the system ...
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LTC2944 shorting

So I am using a LTC2944 battery fuel gauge IC. When a 48V(nominal) Li-Ion battery is connected to measure, the IC shorts. When I measure the battery voltage using a multimeter it is 52.6V which is ...
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110 views

Daisy Chain on the AD7284 not working

We are building a battery management system with BMS IC AD7284. Communication to the first device is done via SPI. Following devices can be addressed with a proprietary daisy chain protocol (...
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Drawing more current from a battery than what it was designed for

I have built a system that requires at least 8A to run properly. It is powered by 6S1P li-ion battery pack protected by BMS circuit. I did some research and found that maximum battery current output ...
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BMS design question

I recently came across this popular BMS design and I am trying to understand the circuit design There are some great technical discussions around it, like on robojax or this non-English forum. Most ...
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Practical usage of Automotive BMS with Active Balancing

I work as an intern at one of top semiconductor companies and also in automotive industry. Since I'm assigned to BMS (Battery Management System) team as a concept engineer I'm constantly looking for ...
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What level of imbalance in series connected cells is good?

If I have lithium battery with some cells in series (same type, same manufacturer) - how much could they disbalance after one cycle? How much is too much? If, lets say, I charge 4S pack from 12V to ...
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Consequences for invalid BMS wire and its diagnosis

While re-assembling the 16S BMS, I didn't notice that the socket for one 8s pack was different from the socket for the other 8s pack until I connected the plug (image 4) to the battery tape, when ...
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Is there any difference between Li-ion and LiFePo4 BMS

I am recently exploring how to make Lithium Battery packs and trying to build my on my own for Electric Vehicles. I've learnt about both Li-ion and LiFePo4 cells and understood their differences. But ...
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Can I use a BMS to get different voltages?

I am making a 3s2p 18650 battery to make a 12v battery pack for a project I am working on. When I test the various battery cell pads on the BMS I get the expected voltages, 3.7, 7.4, and 12. However, ...
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Just making sure I have this right before I start welding

I have an RC project that requires a 3S battery pack. I am making my own, but want to make sure that I have my cell configuration right before I start spot welding. I am 99% sure this is right, but ...
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Not satisfied with 2.5 V battery protection shutoff. How to stop discharge at a safer voltage?

I have some of these lithium ion battery charging modules which are very commonly available online. They use a TP4056 charger and a DW01 protection IC. The DW01 datasheet says that it should cut off ...
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BMS Two Stage OP Amp

My company is designing a 4 cell BMS. We recently did a redesign of our cell voltage measurement circuits and are having major issues. The first stage of each amplifier is a differential opamp with ...
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Diodes between BMS pins

What is the purpose of the three diodes in this BQ76940-based battery monitor schematic?
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Using 6S lithium-ion battery with(out) bms?

I built a 6S LTO battery pack and I am wondering - does it need BMS? Battery will be charged with car alternator - voltage wont exceed passive BMS balancing threshold (battery will never reach maximum ...
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Battery management system - voltage at BAT pin

I am working on a BMS with a BQ76940. I have prepared a circuit with the help of the Typical Application Schematic from the data sheet. I have connected 9 cells to start with. When I measure the ...
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My 15S BMS of LiFePO4 battery stack outputs 15.9 V (the entire pack measures 48 V)

I have a LiFePO4 stack of 15S and 3P configuration. Everything was working fine until I broke the pack and divided it into two packs of 8S and 7S, and connected both via jumper wires. Now the pack ...
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Why doesn't this LTC6803-4 battery controller work?

Our team is currently working on a Battery Management System with specifications as below: 12 x 3.3 V, 50 Ah LiFePO4 Batteries, connected in series LTC6803-4 Battery Controller Monitored via Arduino ...
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Battery Management System - Fast charging

I am using a TI BQ76940 battery management IC for a project. I want to implement fast charging in this system. How can I go about achieving it? Can I connect multiple high-side bidirectional MOSFETs ...
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EEPROM in battery management system

I am designing a battery management system. I am however unable to comprehend the way in which EEPROM can be accessed to feed OCD (Over Current Delay) values. I have attached the datasheet: https://...
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Battery management system

I am designing a battery management system for lithium ion batteries. I am referring a schematic that is already available. I do not understand the function of the two MOSFETs marked in the schematic.
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BMS adjusting charge current

I use this ready module for 3S battery group. Due to high charge rate (pull about 2-3A from power supply) a high current power supply also needs. I want to reduce charge rate up to 0.2C or 0.1C. No ...
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Charging a LiPo battery with load

I have built my own BMS (Battery Monitoring System) that can control the SOH (State of Health) and SOC (State of Charge) of a LiPo battery. It can control every cell voltage (with passive cell balance)...
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2S BMS shuts down by itself

I made a small 2 DC motor Arduino robot car which is powered by two 18650 cells. I am using a 2S BMS with a TP5100 to charge and protect my cells. I am using a DC-DC boost converter to make 9 V to ...
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Powering a RPI board with a 22V battery pack

I built a 22V battery pack with 6 18650 cells connected them to a 6s BMS. I will use this to power a portable audio amplifier. I also want to use the same battery pack to power a Raspberry Pi Zero W ...
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What can be possible reason for explosion and fire in battery pack built with 3S Li-Ios BMS

I recently made some 12v battery back using regular 3S Li-Ion BMS and 18650 cells. Unfortunately, 3 of them EXPLODED and one even caught fire on site. The BMS I used was almost exactly like this but ...
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Li-ion BMS 2S3P wiring to a 2S BMS

I'd like to seriously increase the capacity of my pack by adding more cells in parallel whist maintaining 8.4v from these 4.2v/3500mAh 18650 batteries. I'd like this scalable so I could potentially ...
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Is a battery pack connected parallelly or in series?

I have a circuit of a battery pack of 4 18650 and a 4S BMS. See the picture below. The question is: is my understanding correct that this circuit means that the batteries are connected in a series, so ...
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2 votes
1 answer
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How to choose components to charge/discharge 18650 battery block for a robot

I want to build a battery for my robot, and I don't understand how to choose components to use after BMS to charge/discharge the battery. I have 4 pieces of 18650 batteries: 3.7 V, 6.7 A maximum. This ...
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1 vote
3 answers
298 views

Is an Ideal Diode necessary for BMS?

I'm designing a battery pack that's on the order of 10s5p. Each 10s stack has its own BMS, with high side driven FETs for charge and discharge. This is based on the Texas Instruments reference design, ...
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4 answers
955 views

BMS charging voltage. Can I supply overvoltage?

Most decent battery management systems out there employ balancing, overdischarge protection, overcharge protection, etc. Almost universally they state that the charging voltage is just 4.2*N_cells. ...
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BMS 4S 40A Li-Ion balancer board problem

Trying to figure out how to use the BMS 4S 40A Li-Ion protecting balancer board that I got off Ebay. Revision 2.3, photo and schematic is attached. I am building a power bank. Got some new NCR18650b's....
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How can I follow the current in this DW01A circuit?

I try to understand the inner logic of this diagram, this a modified version of a schematic that I found online. I made the necessary calculations for my power MOSFETs and all but I have some ...
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1 vote
1 answer
226 views

DIY protection board for lithium-ion batteries. How to scale a schematic?

I need to build a DIY protection board for a university project. We are not allowed to buy one online so I have to construct it myself. I have found a variety of schematics accomplishing the same ...
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3 votes
1 answer
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Smart BMS UART problems [closed]

I recently bought a Daly Smart BMS from China for an EV project. It works well but we can’t communicate with its UART port. I got the pinouts and protocol from manufacturer and connected it to an ...
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109 views

Power adapter 12V for charging LiFePo4 12V battery with BMS with passive balancing

I have a project where I need to charge an Enerpower LIFEPO4 Battery of 12V 12Ah with BMS with an integrated passive balancer, protection against overcharge, deep discharge, over-discharge (...
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Is a LiPo battery cut-off voltage open-circuit or under any conditions?

I'm working on battery management system firmware for a battery pack consisting of these cells. The battery pack powers a motor that, of course, when pulling current causes the voltage of the LiPo ...
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How to charge 8S battery pack with two 4S BMS circuits?

I recently made 8S battery pack out of 18650 cells (4.2V each) and I am worried about connecting it to BMS. Some time ago I asked what BMS should I get (well, I asked if i have to have some BMS at all ...
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Is it a good idea to charge multiple Li-Ion batteries using a single buck converter?

I am trying to implement a DIY MPPT into my solar tracker project and I wanted to know if it was possible to charge all of the three li-ion 3.7v batteries in series with just one feedback buck ...
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Can you just rely on battery BMS's undervoltage protection for normal use

Let's say you buy a lithium battery with BMS circuit included. The BMS protects against undervoltage (and other things) and only 2 wire-leads come out of the battery (so no seperate charging wire). eg....
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1 vote
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115 views

Are parallel wired BMS controlled batteries even necessary?

I've read many question on here about how to connect multiple BMS controlled batteries in parallel to step up amps. Is this necessary to step up amps as opposed to running all the cells in series and ...
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630 views

Undervolt protection circuit

I want to undervolt protect a series of 3 Li-ion cells. The load is a voltage booster with initial 5 amp usage for 5 seconds. Then power consumption is reduced to 5 watts. (It works ok on battery.) (A ...
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Can I use TP5100 2S battery charger with 2S BMS

I want to use TP5100 2S battery charing module with a 2S BMS. I posted questions before and found out that I can't use BMS only to charge. So can I use TP5100 as a charger and a BMS together? ...
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326 views

Can I Charge 2 18650 with 2 TP4056 boards with single input

I found this video on youtube where they charges 2 18650 with 2 TP4056 modules with one input. below is the schematic he uses. Is it safe to do that?
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Can I charge 2S 18650 battery pack with a BMS and a 9V wall adapter?

I have this cheap 2S BMS board that I want to use to charge a 2S 18650 battery pack (two 18650 in series.) Can I use this BMS board with a 9V wall adapter to charge my battery pack? I want to make a ...
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BMS for 12V Lead Acid Batteries (48V)

I'm thinking about creating a BMS for my Battery Bank. The bank consists of 12 VRLA Batteries connected in 4 series and 3 parallel configuration to get a 48V system. For this bank I wanted to monitor ...
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Problems with LiPo Volt buck boost for a LED

I need a little bit of help in understanding buck-boost converter. I have 4 LiPo 18650 batteries in series an BMS to charge and discharge the batteries properly. After that I added the buck-boost ...
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1 vote
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Building a 1S Li-ion battery pack with all the cells in parallel and using a DC to DC converter to get higher voltage

I want to build a 12 V battery for my Mac Mini and possibly a 36 V battery pack for a electric scooter I plan to make later using some old 18650 cells. I have read that a lot of battery management ...
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If I connect three different capacity lithium batteries in series with a 3S BMS board, When the BMS will stop giving output?

If three different capacity batteries are connected in series with a 3S BMS board, when the lowest capacity battery runs out and under voltage occurs of the battery then will the BMS continue giving ...
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1 vote
1 answer
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What does 2.5-3.0V mean on BMS specs?

I'm looking at buying a cheap eBay BMS to prevent overdischarge of a Li-Ion battery, but I'm confused about the specs. Basically every BMS I can see lists the overdischarge cutoff voltage as "2.5-...
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