[Popkorn]

Stumbled across a site that sells these
Gyll 48v packs. They are sold for solar arrays. I need at least 2 of them in series. Eventually 2 more parallel. Any reason why it would be a bad idea to run them in an EV? The solar company said it could work but would void the warranty.
Running a Curtis 1221B - 7401 400A controller and a little 96v Prestolite MTC 4002L motor.

 

[brian_]

The specifications include a maximum current of 100 amps, which is 4.8 kW at 48 volts. That's not much...

 

[OR-Carl]

Yeah, these batteries are designed for stationary applications, which does not use nearly as much current as an electric vehicle would. If you look at the picture with the specs, they suggest limiting current to 30A. If you pull 100A, it will shut off after 10 seconds, 150A will shut it off after 3s. At 250A is will shut off in a second. It does say you can put them in series, which I know some of these battery packs do not allow, so at least they would be possible to use.

You would need a lot of them in parallel, and even then, the risk of an unexpected shut-down occurring on hard acceleration would be a deal breaker for me. At 300$/kwh, you would basically be better off just buying prismatic LFP cells in a size that made parallel strings unnecessary. Of course, you could buy salvaged OEM cells for less than half of that price, but it will take a little more work.

 

[JeffAU]

OR-Carl, I was wondering if what you mentioned about selecting the right size prismatic cells to make a pack all series and no parallel is generally what is done and recommended by experts. I'm in Australia where there are virtually no affordable pre-built, EV battery packs so seriously considering building my own pack with a reputable BMS, I'm looking at building a 300 -400 volt pack, ideally in the region of 25KWH. Does anyone know a good value reputable BMS supplier, Even if they are in US as that is one component I can probably get relatively cheap international shipping or forward shipping if necessary due to its small size compared to everything else?

 

[JeffAU]

Sorry Or-carl, just noticed you've answered the question on BMS recommendations in the"LIPO battery module build help" thread.

 

[OR-Carl]

OR-Carl, I was wondering if what you mentioned about selecting the right size prismatic cells to make a pack all series and no parallel is generally what is done and recommended by experts.

I think this was the way it used to be done; prismatics seem to be falling out of favor here due to the abundance of much cheaper vehicle batteries out of crashed production cars. With big cells (prismatics), you can just bolt them all into parallel at the cell level before making your series string, and in fact Leaf batteries do something akin to that. I suspect that Nissan had good reasons to do it that way, but I am not sure what their reasoning was, or how it applies to your situation.

As long as the cells are connected with large conductors, they will act as though they are one cell. Too many cells arranged that way though becomes unwieldy.

What cell sizes have you been able to find, and how much capacity are you shooting for with your 400v pack?

 

[brian_]

OR-Carl, I was wondering if what you mentioned about selecting the right size prismatic cells to make a pack all series and no parallel is generally what is done and recommended by experts. I'm in Australia where there are virtually no affordable pre-built, EV battery packs so seriously considering building my own pack with a reputable BMS, I'm looking at building a 300 -400 volt pack, ideally in the region of 25KWH.

It's certainly preferable to have no parallel strings, but it's okay to connect cells in parallel at the lowest level of the pack configuration. Few if any production EVs have no parallel cells, although it is found in some plug-in hybrids. 25 kWh is very small by current EV standards, and at the usual 360 V nominal that requires 70 Ah cells; since 40 kWh and up is now normal, two three cells in parallel is common.

If cells are paralleled at the lowest level (connected in parallel groups then those groups connected in series) it makes no difference to the BMS, which just treats each parallel cell group as a single cell.

 

[brian_]

I think this was the way it used to be done; prismatics seem to be falling out of favor here due to the abundance of much cheaper vehicle batteries out of crashed production cars.

True.

With big cells (prismatics), you can just bolt them all into parallel at the cell level before making your series string, and in fact Leaf batteries do something akin to that. I suspect that Nissan had good reasons to do it that way, but I am not sure what their reasoning was, or how it applies to your situation.

The Leaf is no different from all the other pouch-cell packs as far as series and parallel configuration is concerned. Cells are connected directly to each other in pairs (2P: two in parallel) then 96 of those pairs are connected in series (96S2P). The odd things about the Leaf are just that a module has only two groups in series (so there are many small modules compared to the more typical fewer larger modules), and that the tap between the cell groups (for the BMS) has a relatively big screw terminal.