BMS for Lithium Iron phosphate battery bank LiFePo4

[(*steve*)]

I like the use of cutting boards

 

[AprilSteel]

Found that right BMS for a 24 Volt LiFePo4 system with the right cut-offs ,free postage and cheap $USD13 to $22 .
Also with the one input and output I can parralel them up for more amps

https://www.aliexpress.com/item/8S-...474.html?spm=a2g0s.9042311.0.0.27424c4dDhGzaQ

 

[Audioguru]

The very important specification called "Capacity" is missing from this cheap Chinese junk.
It gives the spec's for a "protection circuit" but does not say it has one.

EDIT: Sorry. I see that it is a BMS, not a Lithium ferrous battery. Some of us say "protection circuit" and others say "BMS".

 

[AprilSteel]

Still at it huh ! Duh ! Most of what you are buying uses cheap Chinese junk . Wake up and get with it. I'd also add that the cost of postage of anything from the States to anywhere else is exorbitant and unconscionable.

And
No, a Protection circuit as you call it is to me ,a PCM Power Control Module or if you like Protection Control Module , all it does is when tripped , channel some small current through a bunch of resistors as heat to reduce voltage across a single cell of 3.2V. I will put a picture of a PCM below

A BMS or Battery Management System seems to be used when a more complete protection is needed . It disconnects the charge when high or low voltage limits set by the chip are exceeded . It also has a bleed off system similar to a PCM as the voltage is rising under charge but not yet over the set high voltage.

 

[AprilSteel]

Just an update in Feb 2019
My 50 Amp hour 24 Volt LiFePo4 battery has been running very well for 12 months now .
There is no corrosion . No acid spills . The capacity if anything has increased slightly .
I charge it from two house solar panels in series giving me 62 Volts or so in and the MPPT charger gives 15 amps charge in from 10 to 11 am and its full. I have seen it at 18 amps on semi clouded days
I obtained a "Celllog8" 8 cell monitor which does LIFEPO4 and LI-ION and set to LFP it gives me an accurate view of the state of charge of each cell , high and low vell voltages and an alarm .
The 8s BMS for $20 is working excellently .
The 500 watt inverter has not missed a beat.
If I turn off the solar input my TV using 170 watts will run for 10 hours.It draws about 5 amps.
Solar on I can run all through my awake hours with my desktop PC on also.
So I commend this system to you as the battery system we have all been waiting for .
My next foray is up to 3000 watts capacity with the same cells only larger at 240 Ah and a 3Kw Inverter. It will be 48 Volts so 16 cells .

Here is an instructable I did on the 24Volt system above.
https://www.instructables.com/id/Working-System-LiFePo4-Battery-and-Spotlights-With/

 

[Bluejets]

Classy installation......

 

[AprilSteel]

Everything is still operating well and the battery seems to be holding its capacity.
Had a hiccup with the charger though . made for lead acid but set to USER it still insisted on going into equalisation every so often . Must have been doing it for a while and I didn't notice.

When the battery is fully charged the controller decides to up the voltage to over 30 Volts to shake the sh off the lead acid plates. This does not work for LFP and turns the BMS off. Charger stops trying so BMS turns back on . 10 seconds later it tries again and so on.

These chargers are not suitable . Tempory fix was to use the GEL setting so equalisation does not come on and get a new charger that I could get equalisation turned off . The GEL setting voltages were set so I had to accept the higher voltage points but I decided to just disconnect the PV input line and only connect it when the battery capacity got down to 20%. Amazing things these LFP cells . Take them to 0% and no damage done.

Here is my latest venture down the LFP road. 400 Ah 12 V or 200Ah 24V or 100Ah 48V. About $3000 AUD with inverter controller and all gear. $2000 USD

https://www.instructables.com/id/100-Ah-48-Volt-LFP-Battery-Construction/

 

[AprilSteel]

BTW here is an active cell balancer that I leave attached now . It seems to be working excellently. There have been claims that it just dumps voltage through a resistive load but thats now been proved to be wrong.

https://www.aliexpress.com/item/33018862449.html?spm=a2g0s.9042311.0.0.34684c4dGH61UP

Ill put the analysis in here when I find it.

https://www.beyondlogic.org/review-...ive-equalizer-balancer-energy-transfer-board/