I've been waiting some time to post what I feared would be the case from this company, but I think it's time to let as many people know as possible.<br /><br />As you're aware for those following along I've had a few, to say the least, issues with the BMS system I purchased from Elite Power Solutions. I've emailed them quite a few times along the way but never really got a fix to anything and it always resulted in me figuring out a work around to make the system happy.<br /><br />Recently, I thought I had two bad cells. It turns out, again, the BMS was misreporting these cell voltages, but only under load (they show fine at standing voltage, but drop quicker in voltage on under load than they really are). Here is the email transaction. It seems to start off fine, but after well over a month, I just feel like I'm getting the run around.<br /><br />April 15, 2009 6:37:03 PM<br /><span style="color:#3366ff;">Hey Jennifer,<br /><br />I noticed yesterday two of my cells are experiencing excessive voltage sag under load. I looked at the discharge graph for these cells at 1C and all of my cells seem to match this. They are typically a little under 3.2v @ 1C. The other two cells are at about 2.9v. At 3C the problem is much more noticable. My average cell voltage is 3.0v or so and the two bad cells are usually around 2.5-2.6v. These numbers were taken at full charge to the pack and I've only got about 15 cycles on the pack.<br /><br />The serial numbers for the two cells are:<br />080730-EDITED<br />080730-EDITED<br /><br />From my understanding this is a sign of a weak or failing cells so I'm guessing I should get them replaced before they leave me stranded.<br /><br />Thanks,<br />Brian</span><br /><span style="color:#3366ff;"></span><br />April 15, 2009 10:46:47 PM<br /><span style="color:#ff0000;">Brian,<br /><br />Voltage is sag is due to internal resistance of battery cell. Are the resting voltage of the cells OK? The internal resistance of these two cells are 0.31 and 0.41 resspectively (most of the cells have resistance between 0.3 to 0.44mohm), which are below our control limit of <1 mOhm. Are the reading coming off from BMS reading? Is it possible you physically verify using a voltage meter? <br /><br />I recommend you continue to use them and monitor the performance of these cells. If you fail for whatever reason we can replace them.<br /> Regards,<br />Jennifer Wenren</span><br /><span style="color:#ff0000;"></span><br />April 18, 2009 10:12:10 AM<br /><span style="color:#3366ff;">Hey Jennifer<br /><br />I had some time to test the cell voltages under load with my multimeter. There was about .01 voltage variation at rest. It was hard to see the worst case while driving but I noticed as much as .15 voltage difference so it looks like the computer and not the cells. Both cells that are reporting low are on the same module. Is there a way to adjust each cell in the module or does the module need to be replaced to fix this?<br /><br />Thanks,<br />Brian</span><br /><span style="color:#3366ff;"></span><br />April 18, 2009 11:16:57 AM<br /><span style="color:#ff0000;">Hi Brian,<br /><br />There is a voltage adjustment knob at the cornder of the voltage module if you want to fine tune it. I do not think it is defective.<br /><br />Regards,<br />Jennifer Wenren</span><br /><span style="color:#ff0000;"></span><br />April 29, 2009 6:04:28 PM<br /><span style="color:#3366ff;">I've tried fine tuning the module, but it is of course changing all the cells voltages. The module was Address 0,0 and cells 5 and 9 were the two showing low under load. It turns out these two cells are also showing the highest while charging. I swapped modules with 0,1 and now cells 5 and 9 are fine but 15 and 19 now show the same problems so I'm positive the module is defective.<br /><br />What are my options for getting this replaced? I'd like to avoid any down time since I'm using it to commute to work daily.<br /><br />Thanks,<br />Brian</span><br /><span style="color:#3366ff;"></span><br />Wednesday, April 29, 2009 10:03:26 PM<br /><span style="color:#ff0000;">OK, I will replace the module for you. Will ship to you in 2-3 days. I will inform you the tracking number. Please go ahead and ship the old one back to us, and let me know the tracking number.<br /><br />Thanks! Regards,<br />Jennifer Wenren</span><br /><span style="color:#ff0000;"></span><br />May 4, 2009 6:41:36 PM<br /><span style="color:#3366ff;">Hey Jennifer,<br /><br />I received the replacement module today but I'm afraid it didn't work at all. I replaced my module which was at address 1,0, with the one you sent, and all of the voltages for cells 11-20 were bouncing around between 0.3-0.6v. I also tried switching the module with 0,0 but then all the 1-10 cells started reporting the odd voltages. I also tried messing with the fine tune adjust, not knowing how much that could affect the voltages, but it didn't change anything. I reset the computer with each change in case that made a difference but no luck all around. If I plug my old module back in the voltages are normal again (at least until I drive or charge).<br /><br />Any thoughts on what to try? Otherwise I can resend this module back tomorrow and wait for another? :(<br /><br />Brian</span><br /><span style="color:#3366ff;"></span><br />May 13, 2009 10:07:12 AM<br /><span style="color:#3366ff;">I'm resending this email to your work email since I haven't received a reply still.<br /><br />Brian</span><br /><span style="color:#3366ff;"></span><br />May 13, 2009 11:01:29 AM<br /><span style="color:#ff0000;">I am sorry about the problem. I will get another voltage module from another package. Please send back the module in question, and upon receiving it, we will immediately send you an 2nd replacement. We will try the unit in our car first before sending you the next time. Regards,<br />Jennifer Wenren</span><br /><span style="color:#ff0000;"></span><br />May 27, 2009 8:16:34 AM<br /><span style="color:#3366ff;">Hi Jennifer,<br /><br />I see the defective module was delivered to you on May 16th.<br />Just checking on the status of this.<br /><br />Thanks,<br />Brian</span><br /><span style="color:#3366ff;"></span><br /><span style="color:#000000;">May 27, 2009 8:23:41 PM</span><br /><span style="color:#ff0000;">I did not received it, which address did you send it to? Regards,<br />Jennifer Wenren</span><br /><span style="color:#ff0000;"></span><br />May 27, 2009 8:29:14 AM<br /><span style="color:#3366ff;">The same address listed in this email and on the package it arrived in. Here is the tracking number. EDITED</span><br /><span style="color:#3366ff;"></span><br /><span style="color:#3366ff;"></span><br /><span style="color:#000000;">This is where it's at now. I'm sure they will not get back to me until I bug them again. They are more than happy to take your order, but don't count on that one year warranty being honored. As far as the TS cells themselves, I'm so far quite pleased. I only ordered them from somebody in the US hoping to get the customer service support if needed.</span><br /><br />I'm probably screwed on ever getting this thing fixed and might just design my own or mix and match a few other options out there.<br /><br />So where should you buy these cells from now? Dave over at EVComponents is offering the cells and a different charger and BMS system. I kick myself, because his cell prices are about 70% of what I paid from EPS. Check out his website at <a href="http://www.evcomponents.com/">http://www.evcomponents.com</a>. They are working at keeping these cells in stock! This means no more 2-3 month turn arouund times either. Very promising for the EV world.<div class="blogger-post-footer"><img width='1' height='1' src='//blogger.googleusercontent.com/tracker/7683526616307057319-6061831757012256855?l=s2kev.blogspot.com'/></div>
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