BMS24T lithium battery management system

jonr

This is about what I would expect to see in a lithium BMS for large cells.   1.2A of balancing.   Apparently about $400.  Any thoughts?

http://www.chargery.com/doc/Chargery_BMS24T_specification_V1.13.pdf

mike95490

Buy a fire extinguisher.

To charge your large cells, you are using solar PV ?  and a MPPT charge controller?  Vehicle Alternator ?  Whatever it is, lets assume it puts out 30A to the batteries.

When the BMS senses the very first cell cell is full, it can only do 2 things:

 a) Balance 1.2 A around the full cell and let the rest charge at 10A, still putting 8.8A into the full cell

 b)Disconnects the MPPT charger from the battery bank and slowly balance all the cells with 1.2A,  till it reconnects the MPPT to the battery. 

However, a MPPT controller receives it CPU power from the battery it is supposed to be charging and disconnecting the battery while solar is connected is a No-No.

But first you have to snake a bunch of wires around the batteries to connect each one to the BMS. 

Do you install a fuse on each wire ?  Why not ?

I want people to THINK about what is supposed to happen and get good answers before you purchase gear

jonr

If good balance is maintained, the voltage limited charger will stop charging before any cell reaches over-voltage.   So no need for a) or b).   But under failure conditions b) could happen (and a fuse on a lead acid charger link could blow too).  Perhaps the BMS24T's charger disconnect output should be wired to an alarm  (better than no BMS).  Or used to otherwise signal the charger to stop (best solution that is used if you use their charger).  Or it could power a relay or SSR to disconnect the MPPT solar charger *input* (simple and effective solution).

So not relevant to the BMS24T, but do good MPPT chargers actually die or start fires when batteries are disconnected while charging?  I have a bunch of non-solar chargers, power supplies and DC-DC converters that aren't bothered by such things.

Dave Angelini

At Shenzhen, 518054, China. Tel: 86 (0)755 26436165, fax: 86 (0) 755 26412865

Just never park the  electric car in the garage and the folks at the above will be there to help.

You are not talking about using this with a home solar battery based system right?

karrak

jonr said:

Or used to otherwise signal the charger to stop (best solution that is used if you use their charger). 

Lots of MPPT chargers and inverters on the market today can be stopped via an external signal.

Only issue I have with the Chargery unit is there doesn't seem to be any way to be able to monitor your battery remotely via computer/phone or the internet.

Simon

mike95490

karrak said:Lots of MPPT chargers and inverters on the market today can be stopped via an external signal.

Other than the Midnight Classic, what other chargers have a shutdown connection ?

 

Dave Angelini

My schneider mppt-80s and 60s all shut down if the Lion battery is overcharging. The new outback 100A will also. 
You can also manually shut down the charger from SCP, or Combox. It is a nice slow shut-down and start-up. Much better than banging the in/out breakers.

Dave Angelini

I do not use the Emergency Power Off on the XW for shutting down outside for fire people. It also shuts down the mppts & inverter.
Outback calls it something different but it does the same thing. A few clients have needed this to get a certificate of occupancy.

jonr

Based on another discussion, it looks like @mcgivor uses a similar model (perhaps BMS16). No fires?

Dave Angelini

It is all balance of requirements. Electronics and their failure modes need to be addressed. A fairly non-smart lead acid battery just does not have that extra layer of failure that a lithium battery and its electronics have. If that is not a problem then it is addressed.

For someone offgrid who does not want to lose power ever, they will need a second independant battery system or be able to get one in a reasonable amount of time. Like going to Costco for an emergency bank of golf cart batteries which I have done for a few clients near me.

My point is adding electronics to a battery is an extra source of failure that was not there before. Fire for any type of batteries can happen. It is pretty rare with a reasonable amount design skill and maintenance. You need to watch a lithium battery a bit more than once a month like a flooded😉