Battery’s or bms for Conext XW PRO 6.8KW

[Joe_]

I have a Conext XW PRO 6.8KW ordered. When I get it installed along with everything else I will need batteries that can make full use of it’s features. Especially it’s ability to deal with starting currents of larger induction motors.
I intend to test that feature, perhaps often.
The flyer says max current draw is 180 amps. To use it’s overload capacity to it’s maximum do I need a battery or batteries with a 200 amp bms?
or what exactly or about do I need?
I was thinking of starting with a battery pack near 16k.
I have been reading for days and am still confused on this. Not sure how I need the batteries to be configured. I don’t want to buy the wrong cells, bms, or ready made lifepo4 batteries.

 

[400bird]

I have a Conext XW PRO 6.8KW ordered.

Congratulations ?

When I get it installed along with everything else I will need batteries that can make full use of it’s features.

It won't do anything without batteries, it is powered from the 48 volt battery bus.

Especially it’s ability to deal with starting currents of larger induction motors.
I intend to test that feature, perhaps often.
The flyer says max current draw is 180 amps.

A 250 amp breaker/fuse is required.

To use it’s overload capacity to it’s maximum do I need a battery or batteries with a 200 amp bms?

I'd recommend significantly higher if you want to push the XW's limits. BMS trips would seriously limit the XW's surge capacity.

or what exactly or about do I need?
I was thinking of starting with a battery pack near 16k

16k what? $16k? 16kWh?

I have been reading for days and am still confused on this. Not sure how I need the batteries to be configured. I don’t want to buy the wrong cells, bms, or ready made lifepo4 batteries.

What way are you leaning? Are you planning to DIY a pack or buy pre-built batteries with integrated BMS?

Either way, I'd recommend a minimum rating of 300 amps discharge (3x 100 amp would do that)
Most of these BMS's are MOSFET based, I don't like running those at 100%. I'd be much more comfortable at 50%, which would mean you'd want 600 amps worth of BMS.

I went a different direction and chose a shunt trip/contactor based BMS, so the current doesn't flow through the BMS, but the BMS still measures the current and can disconnect the battery when needed

 

[ElectricIslander]

I don't have an exhaustive list of Hi current capable 48 V LiFePO4 batteries and BMS's that use the more reliable and more failsafe contactor design vs MOSFET BMS designs, but this may be useful info:

• Discover AES Batteries - contactor design, battery and BMS rated for 1C capable charge/discharge discharge limits
• Discover Element Batteries - contactor design, battery and BMS rated for 3C peak, 1C continuous charge discharge limits
• Fortress Batteries - 5 kWhr and up, contactor designs, batteries and BMS available with > 100 A capabilities
• Vollithium 48 V 10 kWhr - most of their batteries have contactor design, this 200 Ahr battery has 150 A charge, 200 A discharge ratings

I wonder if it's possible to use an external high current contactor relay with a lower rated BMS in a DIY situation?

In the email above, it sounds like 400bird found a contactor based BMS suitable for large DIY cell banks. It would be interesting to learn what BMS that is?

 

[Joe_]

16kWh?

300 amp hours approximately. 48 v of battery bank to start. Most of the inductive loads would be run during daylight.

I have a fairly large AC I might try using it to power after adding a soft start to it.. 2 fridges and a 2 small chest freezers running too.

What way are you leaning? Are you planning to DIY a pack or buy pre-built batteries with integrated BMS?

DIY 304 ah the largest BMS I have found is this 200 amp one. https://www.sunfunkits.com/product/42/sun-fun-kits-200a-v2-4s-lithium-bms-wbluetooth. Have no idea how sturdy it is?

Either way, I'd recommend a minimum rating of 300 amps discharge (3x 100 amp would do that)
Most of these BMS's are MOSFET based, I don't like running those at 100%. I'd be much more comfortable at 50%, which would mean you'd want 600 amps worth of BMS.

I went a different direction and chose a shunt trip/contactor based BMS, so the current doesn't flow through the BMS, but the BMS still measures the current and can disconnect the battery when needed

I haven’t run across anything like that. Is there any downside to that design?

 

[Joe_]

I don't have an exhaustive list of Hi current capable 48 V LiFePO4 batteries and BMS's that use the more reliable and more failsafe contactor design vs MOSFET BMS designs, but this may be useful info:

• Discover AES Batteries - contactor design, battery and BMS rated for 1C capable charge/discharge discharge limits
• Discover Element Batteries - contactor design, battery and BMS rated for 3C peak, 1C continuous charge discharge limits
• Fortress Batteries - 5 kWhr and up, contactor designs, batteries and BMS available with > 100 A capabilities
• Vollithium 48 V 10 kWhr - most of their batteries have contactor design, this 200 Ahr battery has 150 A charge, 200 A discharge ratings

What does 1 C and 3 C stand for? 100 and 300?
Thanks for the list I’ll have a look.

I wonder if it's possible to use an external high current contactor relay with a lower rated BMS in a DIY situation?

No idea..

In the email above, it sounds like 400bird found a contactor based BMS suitable for large DIY cell banks. It would be interesting to learn what BMS that is?

Does sound interesting.

 

[DIYrich]

If you are near St Louis, see the posting about selling EVE LF280K batteries, and pair it with JK BMS B2A24S20P. I like the flexible bus bars to connect the batteries. At $110/cell you could build 2 for about $4,500 and have 28kWh with 400 Amps of BMS continuous (at 100% of rating, so discount from there).

If you don't want to build it yourself, a 30kWh rack of 6 batteries is $9-10k from signature solar.

 

[400bird]

DIY 304 ah the largest BMS I have found is this 200 amp one. https://www.sunfunkits.com/product/42/sun-fun-kits-200a-v2-4s-lithium-bms-wbluetooth. Have no idea how sturdy it is?

That BMS is only 4s, it is for a 12v battery.

I haven’t run across anything like that. Is there any downside to that design?

I'm using a Batrium BMS, but they are very expensive and aren't getting the best reviews right now. I'm very happy with mine, but it seems like it's got too much configurability for many and the newest model may not have all the bugs worked out.

JBD and JK are two BMS manufacturer that are used pretty commonly around here.
This one's rated at 300 amps.

Jiabaida (JBD) Smart BMS Lifepo4 300A 7s-20s Battery Protection Module with Bluetooth Dongle BMS | SRIKO Batteries | Online store for electronics | Online battery store

This is a universal BMS which can be used for Li-ion/Lifepo4//LTO Cell Chemistries. It can be used for many battery pack configurations including 7s 8s 10s 12s 13s 14s 15s 16s 17s 20s Wiring Diagrams for different battery pack Configurations are available at srikobatteries.com website...

srikobatteries.com

And another, this one with a built in contactor

JBD Smart BMS 7~21S 8S 16S 20S 200A 300A Communicate with UART, Bluetooth or RS485 Function freeshipping - Jiabaida BMS

Jiabaida BMS JBD Smart BMS 7~21S 8S 16S 20S 200A Communicate with UART, Bluetooth or RS485 Function. High quality better service and favorable price with free shipping. Battery Management System for NMC/Li-ion Lifepo4 battery, 10+business for the protection boards manufaturing experiences.

jiabaidabms.com

 

[ElectricIslander]

What does 1 C and 3 C stand for? 100 and 300?
Thanks for the list I’ll have a look.

No idea..

Does sound interesting.

Batteries are rated for either discharge and charge rates in terms of multipliers of their relative amp hour capacity C at their one hour discharge rate "C" ( in which C is the measured capacity in Amp-hrs from a 1 hr discharge test). So the rated discharge current for a 100 Amp-hr battery at 1C means 1C-hr x 100 Amp/hr = 100 Amps. A battery rated at 3C means the battery and BMS is rated to be able to sustain a discharge up to 300 Amps.