Seplos BMS with a separate active balancing

[_laurens]

Hey Guys,

I just received my JK BMS but truth to be told I do not like the cable they use (aluminium, not replaceable) and that you have to crimp your own connector for the battery.

I was looking at Seplos which seemed interesting to me because it does allows you to use your own cables and it has a Victron integration which makes this super tempting too! BUT there is no active balancer so I was wondering If there was a solution to have the best of two worlds. Do you guys have experience with mixed setups? I can imagine it will ruin the BMS rating/calculations of voltage etc.

My situation: I hope to have 1 load and unload in 1 day, or perhaps 2 days. So it's rather fast.

In general with my situation would the active balancer be suggested in my case?

 

[CrossStreet]

I think any active balancer will do, they can work in parallel. You need to disable balancing on the bms, otherwise they'll possibly be fighting somewhat. I've bought a Seplos too, but has not used it much for charging and discharging my 28kWh battery yet, but passively it seems to work ok.

 

[brum]

The Seplos BMS can be configured when to do the balancing. The active balancers usually are not "smart" and support no configuration.

You need to find an active balancer that will balance only under appropriate conditions. I.e. activate the balancing only under specific conditions. Let's say over 3.45V. If you find an appropriate one you can connect it parallel to the passive one. They will not "fight". Instead, they will collaborate and increase the total balancing current.

But if your cells are good you don't need an active balancer. They will both age pretty equally and the passive balancing will be sufficient to keep them balanced. There are two cases that I see as suitable for an active balancer:
1) Bad cells that need constant balancing with pretty high current
2) Initial balancing of good cells

Take a look at the latest video from the Off-Grid Garage - pretty close to what you are trying to do.

 

[edcoopered]

Hey Guys,

I just received my JK BMS but truth to be told I do not like the cable they use (aluminium, not replaceable) and that you have to crimp your own connector for the battery.

I was looking at Seplos which seemed interesting to me because it does allows you to use your own cables and it has a Victron integration which makes this super tempting too! BUT there is no active balancer so I was wondering If there was a solution to have the best of two worlds. Do you guys have experience with mixed setups? I can imagine it will ruin the BMS rating/calculations of voltage etc.

My situation: I hope to have 1 load and unload in 1 day, or perhaps 2 days. So it's rather fast.

In general with my situation would the active balancer be suggested in my case?

Why do you thin the Seplos balancer will be inadequate, I've been running a 230Ah 16S pack on one for 18 months, cells went in balanced and are still balanced. This obsession with balancing is IMO driven by poor quality cells (or maybe poorly built systems), the constant rebalancing makes the situation look less dire, but your pack will still underperform, the junk cells will still define the capacity of your system, the balancer will just make it look better.

 

[_laurens]

Why do you thin the Seplos balancer will be inadequate, I've been running a 230Ah 16S pack on one for 18 months, cells went in balanced and are still balanced. This obsession with balancing is IMO driven by poor quality cells (or maybe poorly built systems), the constant rebalancing makes the situation look less dire, but your pack will still underperform, the junk cells will still define the capacity of your system, the balancer will just make it look better.

I thought it might be an issue with resistance, even if it's rather small in time the gap might be widening, which is why I assumed it was better to have it.

Yeah, the downside is it might be masking bad cells which can also cause problems in the long term, I think, decided to go with a mason, including seplos bms.

 

[RCinFLA]

The separate active balancer needs to have its own independent sense leads going to cells' terminals.

If you share a common set of sense leads between BMS and active balancer, the voltage drop due to asynchronously operating active balancer will corrupt the cell voltage readings by the BMS.

All balancers momentarily stop balancing current when making cell voltage measurement to avoid voltage drop on small gauge sense wires.