The Daly or other MosFet based BMS' are ok with a qualifier. When they state 200A Capacity for discharge, that is the absolute limit of capacity. The usual recommendation is, that if you know you will need 100A going through a BMS, then get 150A, if you want 200A then get 250-300A model. Having that elbow room means you won't push the FETS to death.
Typically FET based also only does 50% of the rating for charging. So a 100A BMS will max out at 50A Charge rate, this can be an issue with a large capacity bank. These cells can also take up to 1C Charge rate but it's recommended to not exceed .5C (140A) The more amperage behind the charge the faster they will charge and top off BUT they WILL diverge at the top side... IT IS NOT UNUSUAL for the cells to deviate by 1mv per AH so with 280AH cells you can see 280mv differential. LFP will NEVER sit at 3.65V per cell, even if you charge it till the cells are only taking 0.1A, stop charging and within an hour or two they'll settle between 3.5V to 3.6V each, this is normal.
The other common BMS type uses Relays/Contactors and therefore do not suffer such limits as the Relay is what handles the amperage being passed through it. Contactors can be had up to 1,000A. These do tend to cost more than the FET based BMS and you do have to buy the Relay/Contactors but the payback in performance & capabilities makes it worthwhile. I should note that EV's use Relay/Contactor based BMS' for load handling & reliability.
Basic BMS info:
- There are Dumb BMS' which just do their job, they are preprogrammed and the end user has no access to anything within (settings etc). These are preset with values for the specific chemistry you are using.
- There are Interactive "Smart BMS" which can be accessed by Wifi or BlueTooth or ? These can be configured & tweaked for personal preferences like cut-off points and such. Some offer logging that can be retrieved / accessed. Some have CanBUS or ModBUS others just RS232 output for logs.
- Smart BMS with advanced features: Similar to above BUT with Balancing Capabilities, this adds to the cost and "can be of benefit" if the correct type is selected for the application. The two Basic Balancing are Passive or Active.
-- Passive Balancing is a simple method in which the HIgh Voltage cells in the pack get discharged by the BMS to balance with the lowest voltage within the pack. This is a long slow & tedious process where the BMS burns off the extra voltage which results in heating of the BMS as well, due to the process. (Not much use on cells above 100AH as this is very slow) Also the cheapest form of Balancing Function.
-- Active Balancing actually takes Voltage from High Cells and transfers it to the Low Volt cells within the pack. These can range from 1A to 10A capacity and is more suitable for Large Capacity cells. This ADDS Cost due to the extra requirements for the electronics but can result in improved battery pack performance (IF DONE RIGHT) it is tricky and varies with BMS type & Model.
General Info & Links.
Poll: What BMS(s) are you using in your system(s)? (LiFePO4 only) Index of most commonly discussed BMS' on this forum, with pictures and links to relevant resources. (click to expand) Please keep responses concise and avoid discussion/commentary. Replies should follow the format: BMS...
diysolarforum.com
Hi Folks. I have recently come across this Company (not a new company) which produced BMS' and Active Balancers. I found them via my ongoing search for an Active Balancing System and watched a couple of vids on the products and felt it is worthy of mention in the forum. They have High Amp...
diysolarforum.com
Battery Management System. Compact, yet powerful and feature-rich. Cell voltages, temperature, current and logs are available over communication line.
www.energusps.com
www.chargerystore.com
I use Chargery BMS8T-300 with DCC (Solid State Contactors) (I'm 24V) but have Passive Balancing OFF because I am running large cells (280AH & 175AH) and instead using QNBBM 8S Active Balancer for each pack.
8s 24v Active Battery Balancer Equalizer Anti Short Camper Trailer Battery - Buy Active Battery Balancer,Camper Trailer,8s 24v Battery Product on Alibaba.com
deligreen.en.alibaba.com
SUGGESTED READING !
BU-803a: Cell Matching and Balancing – Battery University
Pre-Balancing Cells | Orion Li-Ion Battery Management System
Li-Ion BMS - White Paper - Dissipative vs. nondissipative balancing (a.k.a.: Passive vs. Active balancing)
Hope it helps, good luck.
Steve
PS: Remember, these 280AH are Grade-A COMMODITY Cells. They are NOT Matched & Batched as equal cells (that can cost up to $50 per cell to get done). They are Grade-A "Manufacturer Specs" and comply with that classification. See the first TWO Links in the suggested readings. That means they will have slightly variable IR (Internal REsistances) at different voltages (most notably at the top & bottom of their voltage range). Remember the Divergence I mentioned.
You may want to watch this as well, Will covers some issues that people raise and it's best to put the nonsense to bed right off the batt.