Thoughts about LiPo used as HV batteries

[Lee Malo]

I was wondering about the use of a bundle of LiPo batteries (1P6S )put together and used as the H.V battery in a E.V ? What are your thoughts ???

[doobedoobedo]

6S is around 22V. Or do you mean a bunch of 6S packs in series?

Also what do you mean by LiPo?
If you mean high drain hobby cells, then I'd say they would be a poor choice for longevity, but a good choice if you just want instant power and don't care about longevity. High drain cells are constructed in a different way to 'standard' LiPo cells, the way they are constructed makes it much harder to produce them with as much consistency as the kind of cells you usually see in EVs. This is one of the reasons they need so much more frequent balancing.

[Lee Malo]

why I am asking is because I have come across an EV with 168 x 6s packs @ 4.1 (+- .1 ) volts each ( high capacity ) , making up a high voltage of 350 volts , 20kw battery pack . Would you use this type of HV battery for the race track driving for more than 40 minutes at a time without any type of cooling for the batteries ? . The best part is this person made the battery box out of plexiglass and the batteries are stacked 42 batteries in each group and there are 4 groups of batteries with plexiglass dividers and fully sealed with no ventilation . The owner bought the battery assembly from a guy in Texas USA * http://www.ampahaulic.com/ * . This battery configuration is screaming Danger to me !

What are your thoughts ? take a look at the link and give your feed back .

[doobedoobedo]

Ah looks like he's using them for drag racing. In which case as much current out of as little weight as possible would be a good thing. I suspect he probably heats them before a run too. Risk of fire probably no higher than an ICE machine on a drag run.

40 minutes is actually a fairly low C output (60 minutes full to flat = 1C, 1minute full to flat = 60C, 30 seconds full to flat = 120C etc. ).

The cells on that site look pretty dubious to me, especially the claims about them. If you look at the 'sleeper cell' operating manual they seem to define continuous as 10 seconds and peak as 2 seconds max - which actually goes with the drag racing thing, but is much worse than the claims for many hobby cells - note 'claims' though, although the completely ridiculous C ratings do seem to have abated a bit.

Would I race a 20KWh pack of them for 40 minutes? Definitely not, I doubt you'd get that long a run time under race conditions for a start. Without sufficient compression they'll puff, and yes they'll get hot.

I suspect the drag racing guys consider them a consumable.

Edit:
For comparison - a high(ish) end hobby pack used for buggy racing https://hobbyking.com/en_us/turnigy-nan ... roved.html note that they actually tell you how much they puff in use and if you run them at their max (claimed) 414A they'll go from full to flat in 40 seconds

[Lee Malo]

This setup is screening death and fire !!! This is the car I am speaking about
The fuse is 3 feet of cable away from the battery and the charger is directly hooked up to the battery without any type of fuse . The charger is located inside the car 6 inches from the driver.

[tom91]

Yes the biggest issue using 'hobby RC' lipos is the making of the parallel connections.

The only 'Clean' 'professional' way of doing this would be single cells paralleled with a busbar before making the series connections.

Remember every connection is a potential issue, and the above example is a minefield of problems.

[Lee Malo]

Yes the biggest issue using 'hobby RC' lipos is the making of the parallel connections.

The only 'Clean' 'professional' way of doing this would be single cells paralleled with a busbar before making the series connections.

Remember every connection is a potential issue, and the above example is a minefield of problems.

If one of the cells has a problem and starts to vent or goes in to thermal runaway this whole pack is a bomb ! The battery assembly has a second layer of metal around the sides and bottom with no pressure vents . The people that thought this setup was a good thing should stay away from E.Vs .