My order of a Mason 280L (Vertical) with grade A 304k cells was delivered on Thursday. Just started to unpack it and it's very suprising to see:

1. It is 3/4 assembled (BMS installed, wheels fitted, Sense PCBs mounted')...

2. It comes with an active balancer installed and an external 'balance' pushbutton...

This is going to be an easier job than I was expecting 😀

Seplos are doing an active balancer as part of their BMS, @hughf ?

I was only aware of one Chinese-based BMS manufacturer who offered active balancing. That's Jikong (aka 'JK'), who also produce the Neey range.

Any chance of a photo showing that BMS unit please?
Others with Seplos Mason boxes can then compare.

Here is the link to their YouTube video showing assembly:

And attached are some pictures of the BMS and balance board.

A couple of issues, the 3-hole bus-bars that fit onto the B- and P- terminals on the BMS don't have the correct hole spacing. Something for me to investigate...

Having watched the video in its entirety, it's clear that the accessories box that was strapped to the pallet isn't the correct one for the 280L. The busbars are different, and the B+ sense cable isn't included... Darn.

Can you continue with install temporarily by using a piece of wire to replace the 'busbar'?

A length of 2.5sq.mm household ring-main cable is good for 20A. Simply reduce the charge parameters until you can get the right part.

I've sent an email with my queries to fogstar support who I purchased the whole kit from. In the meantime I will continue to assemble the kit as far as I can go. I am currently still running on my 9.6kWh CALB pack (16S1P) but I've got two weak cells in that pack which the recent cold spell has brought to my attention. I can't get spare cells that match...

One thing I do need to do is source a suitable charger - I don't want to move my current inverter/charger/mppt off the current pack and onto this new pack until I've got the pack assembled, charged and balanced. I have a 3kW Eltek flatpack HE rectifier, I just need a canbus controller for it.

Picking error at the warehouse apparently - Fogstar delivering the correct accessory pack tomorrow.

As for the active balancer - youtube research suggests that as it isn't programmable and works at any voltage above 3v, it's not really worth using...

Posted by: @hughf

↑

One thing I do need to do is source a suitable charger

Can you expand on that @hughf ?

Is this to be a temporary method of charging the cells in the new Mason box?
Or are you looking for a charger with enough clout to recharge the pack during a few hours of 'cheap rate'?

For the latter situation, you'd need to have a charger rated 3kW to 5kW (100A at a nominal 50v).
In which case, why not buy an inverter rather than a charger?
You could then charge/discharge at 240v AC through the same device.

Posted by: @hughf

↑

active balancer - youtube research suggests that as it isn't programmable and works at any voltage above 3v

It sounds like it's an interim product release by Seplos, whilst working towards something with better features.

Only working at cell voltages above 3.0v isn't too much of an issue, provided that it's only doing active balancing whilst the BMS is charging the battery.
If it remains actively balancing when the cells are exporting then I'd agree that's no very useful.

@transparent I'm offgrid and currently charge my Diy'd 9.6kWh pack from my inverter/charger/mppt. I don't want to decommission this setup until the Mason 280L is charged and top balanced, and to do that I will need a standalone charger. I'll figure something out.

The active balancer cannot be set to work only when charging, from what I understand from the video's that 'OffGridGarage' has produced.

It sounds to me like you need a Power Supply @hughf

You could start by using it to top-balance the cells in parallel.
Power Supply configured to 3.6v with as many amps as it can provide.

Then install the cells into the Mason Box and could use the same power supply to feed in anywhere between 52v - 57.6v, depending on their present SoC.
That will keep them topped up whilst you work out how to prevent the top-balancing mechanism from frittering away the stored charge!

@transparent I've got plenty of bench PSUs available at work, but the plan at the moment is to follow the instructions on the diy solar forum. Throw it together and charge it till one cell hits cell-hi-cutoff, then check the cell voltage delta. If >50mV, connect the cells in parallel and charge with a bench PSU.

Ok. That should be reasonably quick... although it means you're likely going to disassembling the Mason box in order to top-balance in parallel.

So you just need to borrow one of those desktop PSUs which can output 57v.
Simples  🙂