NEWBIE LOOKING FOR BMS ADVICE

[Robin Hillier]

I'm building 4, 12 volt batteries using EVE LF280K cells. They will be independantly fused and switched, feeding a busbar in parallel, feeding a 4000 watt inverter/charger. I would like to avoid unnecessary connections, so my preference is a bms without leads. I will add busbars/leads appropriate to the physical situation. Any advice on the bms and sourcing will be appreciated. This will be used in a fulltime RV. Thank you

 

[timselectric]

4000 w is a huge system for 12v.
Never seen a BMS without leads. Unnecessary connections?

 

[Robin Hillier]

https://www.aliexpress.com/item/100...0b9c84f3ab3f7-1684497716812-05455-_uJEFTk&tt= That is one example of a bms with no leads (it has no main power leads permanently attached, or short leads that will have to be spliced onto or removed to add longer leads). As to the 12 volts, I want flexibility in servicing. I don't want to lose my whole system if one battery has to be taken out of service. I also don't want the losses of a 24/48 to 12 dc to dc converter for my 12 volt loads.

 

[timselectric]

https://www.aliexpress.com/item/100...0b9c84f3ab3f7-1684497716812-05455-_uJEFTk&tt= That is one example of a bms with no leads (it has no main power leads permanently attached, or short leads that will have to be spliced onto or removed to add longer leads). As to the 12 volts, I want flexibility in servicing. I don't want to lose my whole system if one battery has to be taken out of service. I also don't want the losses of a 24/48 to 12 dc to dc converter for my 12 volt loads.

I didn't realize that you were referring to the battery leads. I was referring to the balance leads.
I get the desire for a 12v inverter, when you also have 12v loads. But a 4000W inverter is not a good match for 12v. 3000w is the max recommended. And I would even consider that excessive.

 

[Robin Hillier]

I'm not seeing the issue. The watts are there regardless of battery configuration. The only advantage I see in a higher battery voltage is keeping down the size of the wires, which doesn't concern me as the distances are short. What am I missing?

 

[SparkyJJO]

4000W @ 12V = 333A and that is without factoring in efficiency and connection losses. That's a huge amount of current to deal with.

I also question the quality of a 4000W 12V inverter. Not sure how many good ones are out there.

 

[timselectric]

That ?

 

[wiseacre]

4000W @ 12V = 333A and that is without factoring in efficiency and connection losses. That's a huge amount of current to deal with.

I also question the quality of a 4000W 12V inverter. Not sure how many good ones are out there.

I wouldn't want to deal with such high amps but if I did I'd look at a Victron 12V Quattro – 5kVA (4000W) 120V Inverter – 220A Charger

 

[Robin Hillier]

That ?

I don't understand your reply. Are you giving me the finger? HaHa

 

[timselectric]

I don't understand your reply. Are you giving me the finger? HaHa

Agreeing with sparky's post, above mine.
That's the pointing emoji. (Index finger)

 

[JJJJ]

4000W @ 12V = 333A and that is without factoring in efficiency and connection losses. That's a huge amount of current to deal with.

Even with short wires that is a considerable amount of current. Personally I like to keep my wires cool and reduce risk.

My other concern is batteries when rapidly discharged on a regular basis have the potential to wear out quicker. In the solar world slower discharges can equate to longer battery lifespan.

The responses you received above are from very knowledgeable members.

Perhaps consider a higher voltage system?

 

[DIYrich]

JK-B2A8S20P
JK BMS 4-8S (12V-24V) - 200A Continuous - 350A Peak - 2A Active Balancing

You need 100 amps per bank to produce 4000 watts. However, if you take a bank out, you will need more amps from each bank. Hence the 200A continuous. The JK-B2A8S20P has screw connections.

Note: It has 2 screw connections on each side, so you will need 2 wires. The battery also has 2 screw connections. The 80A model has single cable connection.

People are also happy with JBD: JBD 12V 200A BMS - Bluetooth. It has single terminal connection. I believe it is passive balance.

 

[Robin Hillier]

Admittedly the 4000 watt inverter is a bit of overkill, but if I want a few minutes of AC or electric heat I would like the option of doing so. Thank you all for your comments. I'm still at the planning stage, so I'm gathering info.

 

[timselectric]

Admittedly the 4000 watt inverter is a bit of overkill, but if I want a few minutes of AC or electric heat I would like the option of doing so. Thank you all for your comments. I'm still at the planning stage, so I'm gathering info.

If you are referring to A/C (air conditioning) .
Consider two smaller inverters. One dedicated to the A/C. When not in use , you can turn that inverter off. And save some idle current as well.

 

[Robin Hillier]

If you are referring to A/C (air conditioning) .
Consider two smaller inverters. One dedicated to the A/C. When not in use , you can turn that inverter off. And save some idle current as well.

Yes I did mean air conditioning.

Even with short wires that is a considerable amount of current. Personally I like to keep my wires cool and reduce risk.

My other concern is batteries when rapidly discharged on a regular basis have the potential to wear out quicker. In the solar world slower discharges can equate to longer battery lifespan.

The responses you received above are from very knowledgeable members.

Perhaps consider a higher voltage system?

I also like cool wires. The wires/busbars will be sized appropriately. I do everything with overkill, so I may never get near the max output of the inverter.

 

[Robin Hillier]

JK-B2A8S20P
JK BMS 4-8S (12V-24V) - 200A Continuous - 350A Peak - 2A Active Balancing

You need 100 amps per bank to produce 4000 watts. However, if you take a bank out, you will need more amps from each bank. Hence the 200A continuous. The JK-B2A8S20P has screw connections.

Note: It has 2 screw connections on each side, so you will need 2 wires. The battery also has 2 screw connections. The 80A model has single cable connection.

People are also happy with JBD: JBD 12V 200A BMS - Bluetooth. It has single terminal connection. I believe it is passive balance.

Thank you for that bms suggestion, I will give it some consideration.

 

[Robin Hillier]

I received one bms suggestion, are there any others people are fond of?

 

[timselectric]

I only use and recommend JK.

 

[Robin Hillier]

I only use and recommend JK.

thanks

 

[JJJJ]

I have the overkill on two of my packs and they work well. Downsides that I see are 100 amp limit output which does not affect me and passive and not active balancer.