Thursday, May 21, 2009

2500 and counting

Today I broke 2500 miles on electric, woohoo! In general things have been really smooth with the build and I'm overall very happy. I'm really pleased with the lithium cells and the balancers I built. Hopefully the cells just keep us moving for many many years :)

OK, so there is one item I'm not completely happy with. The BMS from TS has some really great features all wrapped into one system. Many piece together things like amp meter, fuel gauge, etc. It was nice to find it all in one package, but this thing has been far from reliable.

You may recall my initial problems with charging where the BMS would freak out and start reporting cells at low voltages and such if the charger was at high amps.

The next thing I noticed was two cells that seemed to be sagging pretty bad under load. I placed a volt meter on them and they weren't sagging at all like the BMS reported. There are 5 modules, up to 10 cells connect to each. I switched around two of the modules and then I started getting two different cells (same module) that were reporting sag. I'm still waiting on a replacement from Elite Power Solutions. The first "replacement" didn't work at all and I had to send that one back.

I've also had a couple of occurrences where the charger just stops during the charge and I couldn't figure out why. I was at first assuming it was getting a little hot, so I started opening the trunk (until I get time to vent the trunk better). This seemed to fix it for a bit, but it started happening again. While driving the other day, the BMS alarm went off indicating one cell was about one volt lower than it really was (it immediately jumps back up to normal voltage). This has happened a couple of times now. During charging, any low voltage indication will terminate charging, so again the BMS shows its quality.

I have some plans to implement my own high and low voltage protection, and still use this BMS for the rest of it's functionality. This way if it blimps, it doesn't matter except for viewing purposes.


Dimitri said...


your results confirm my suspisions of TS BMS and charger quality. I like their cells, but whoever they contracted to build BMS and charger is obviously a lowest bidder, unfortunately the end user still pays a hefty price tag on this low quality hardware. I will stick to my PakTrakr and Zivan charger, plus our custom designed LVC and HVC protection. Glad to see the car is rolling good, mine should be on the road in a few days too.

Brian said...

Other than the charger being WAY to big, it has atleast done what's told. It created the problems for the BMS when charging at high amps, but I'm thinking any charger may have created the problem. The BMS should have been able to filter out any noise.

So yeah, as you mentioned, I plan to remove the BMS from my HVC connection to the charger and add my own. Then the BMS can give the occasional incorrect data point, but it won't be an issue.