Suggestions for use of 24S (88V) modules for grid storage

[CyberBill]

I've come across a source for some large battery modules used in busses. 48 cells arranged as 2P24S, 88.7VDC nominal. 7.6kWh each. They weigh 140 pounds each with integrated BMS and cooling. It's looking like I'll be able to get at least 6 of them, maybe more, and might be able to get a trickle of them over time.

I have been planning a grid-tied battery storage system for a little while, and my plan was to use an EG4 GridBOSS and a FlexBOSS21 with some kind of 48V battery, but this kind of throws a wrench into that, as it (like other 48V battery inverters) only supports up to 60V. So I'm looking for some advice/recommendations. I know of at least two options:

Option 1: Open the modules, reconfigure for 16S. Either do 3P16S within each module, or 3x 2P16S out of each 2 modules. I'd have to open the pack first to see which would be more feasible. I'd also probably need to buy a 48v BMS for each module.

Option 2: Find an inverter that supports 24S packs. I really like the EG4 setup (gateway + multiple inverters), so in addition to finding an inverter I'd also need a compatible gateway.

What do you think?

 

[Hedges]

There are high-voltage inverters which support select HV batteries such as those from BYD.
There is a project with code on Git Hub to take EV packs and emulate supported HV inverter batteries.

R

Post in thread 'Seeking Advice: Low Voltage vs. High Voltage Batteries for Home Energy Storage'

Jun 18, 2024

It makes a lot of sense to me that the trend of ESS voltage increasing over time (12 -> 24 -> 48 -> ??) will continue. SMA's upcoming Sunny Boy smart energy hybrid inverter (just shipped this past week to SMA's distributors) only works with HV batteries (90v+ IIRC), which is really telling. But I'm kinda bummed, bc I really want to use that inverter but SMA said its currently only compatible with BYD HV battery systems, which are like $600/kWh, which is way more than some of the 48v ESS options out there (EG4/Goodwe/etc ~$300/kWh or less). Anyone know of any HV (>48) battery systems...

• Rational

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maybe your integrated BMS is supported. I would think the bus uses a higher voltage configuration. Probably also has an additional box that talks to the modules and has contactors to disconnect.

What I know of people getting working so far is complete EV modules with complete BMS.

Alternatively, people do cut apart modules like you're thinking.
Instead of cutting, I've had the idea of making +24V and -12V batteries (relative to ground). 12V can be useful to backup telecom. But this is way more Ah than you're likely to need.

 

[CyberBill]

maybe your integrated BMS is supported. I would think the bus uses a higher voltage configuration. Probably also has an additional box that talks to the modules and has contactors to disconnect.

Yes, I believe it uses 42 of these modules, for 320kWh total. Not sure what the voltage is when complete.

I did some searching of the model number and make of the batteries and couldn't find any references to them online other than one page. They are from XALT Energy, called XPAND 76P. Best I can tell they use in-house BMSs on each module and then an additional control box that they plug into.