Planing CanView and BMS+ conversion with lithium

I would go with using a 6Mohm trim pot if they exist. But I would not adjust it to any lower than 1 Mohm. So say a 5 Mohm trim pot in series with a 1Mohm resistor.

The V+ to solder the resistor to in the photo is a glass fuse for the output. The glass fuse is covered with heatshrink tubing.

I did not see any photos where he connected a resistor in series with a trimpot connected to the V+. So I have assume he has never done this mod to decrease the endpoint voltage in practice. He did the calculations to decrease the endpoint voltage but that is all.

 

3,2v is a little lower then our A123 (3,3v). But 72x3,2v is ok = 230v End voltage will be 210/72=2,9v. It is also ok.
3,8v is high. Are they Lifepo4 cells ?

It is very important that your cells accept a regen like 100A during say 30-60 sec

 

I think this person is confused with some batteries options

 

Okay
What"IF" you go with the 60ah LifePo4 GBS prismatic 3.2v rated what cell count could you go with???? Does the cell just have to be rated 3.2 only.Can I pm somebody my questions this back for kinda slow

 

GBS cells are rated to 3.2v. Not 3.8v. See here Elite Power Solutions

 

I am real confused because EV Lithuim gives the following rating /specs
60Ah
Working Voltage
Single cell charging：3.8V
Battery pack charging：3.65V
Single cell discharging：2.5V

 

Yes you are correct!!!So can you help

 

Single cell charging：3.8V - No single cell should exceed 3.8v during charging. BMS setting.

Battery pack charging：3.65V - Complete battery pack should not exceed 3.65v x 72 cells = 262.8v during charging. Charger setting.

Single cell discharging：2.5V - No single cell should go any lower than 2.5v during discharging. BMS setting.

Going outside these limits will damage the cell/s during charging or discharging.

BMS - Battery Management System

 

Hi Texas,

This topic is about DIY BMSplus PHEV kits for hobbysts and EV enthusiasts. You need to spend some time researching and studying this topic. Reading Norm's website is a must CAN-view index as a good starting point. Also use google to research.

 

Thanks
I still have a few more questions?? First, what control boards do you have besides the main BMS plus? Have you seen the new thread that shows a image of 10kw PIS that planitere posted?

 

Where do you suggest I research and search for what?? OH BTW FWD and you may want to start a new thread of your own

 

uh??

 

Wth! Wadh.

 

one cell when down fast to 2,6 and 2,5 volts and after that 1,9!!!!!
this cell was the highest of them all and dropped to the lowest voltage after taking ~16ah out of the pack
so i guess i really have 1 really really bad cell

then there are around 12 that where at 2,7 volts and some 2,8 and others at 3 volts where i want them al to be... and that after using 16ah according to canview... and looking at the voltages i would say i used more then 80%
so i am guessing non of these are close to 19ah but more like 17ah or so..

now i have to take the battery pack apart again... i really dont wanna do that again...
at this point i just want to stop......

i need something like this
West Mountain Radio - CBA III - Computerized Battery Analyzer

 

yesterday i did a top balance where all where at 3,688-3,7
now 12 hours later most of them are above 3,6xx and just 8 of then are below that at 3,5xx
so what does this mean? your al saying that these cell after a full charge drop down to 3,5 after just a short period.
so are al the high voltage cells bad ones ( maybe ? ) because the bad cell that dropped fast is one of the higher ones.

......

 

FWD if your cells are not very well matched could you perhaps bottom balance them instead? Discharge them all down to the same voltage, then charge at fixed current until the weakest cells hit the finish voltage? Your voltages will be mismatched at the top end, but everyone should get to the bottom at the same time and you will have gotten the most out of the pack you can. Other than that it does sound like you may need to just characterize the capacity of the cells and weed out the weak ones if there aren't too many. Bummer that you're having so many issues. Do you mind sharing where you purchased the cells from? The usual ebay guy?

 

When a battery pack is put together at the factory they make sure all the cells come from the same production batch. Then they all have the same internal resistance and will probably balance evenly at the top. The cells being sold by Xueming08 on EbAy are either rejects or excess stock and they probably come from different batches. I am in the opinion they are rejects - why else would they cut off the tabs. You got the cells with tabs so who knows.
Bottom balancing has the advantage of shifting a lot of charge from strong cells to weak cells to maximize range. But if it gets it wrong it can overcharge a cell/s and kill it. Therefor I prefer top balancing as all it can do is just burn off excess charge, a bit simpler and in my opinion it is safer than bottom balancing.

 

Let see after 159 plus "posts" to this thread alone and you have something of no value to "post" again who would think .FYI a memory check thread is TITLE "Planning Canview & BMS plus conv with Lithuim".

 

Maybe you should take your own advice. Look at your own posts before you criticize others.

 

Easy there Tex. There is really no proven recipe for an affordable DIY lithium conversion. Those that want one now figure it out by investing significant amounts of their own time and money in trying, and through sharing their experiences collaboratively in discussions like this. FWD has been extremely generous in sharing the challenges he's faced with one approach so that everyone else here can benefit from his experiences in what working and whats not. As a result we'll all be better off the next time someone tries to do one.

You've asked an awful lot of questions without really contributing anything of value, so one would think you'd be a little more appreciative of the information others are providing as it will likely save you a lot of money and effort in experimenting when it comes time to do your own conversion. I can understand if you're a bit frustrated that no one will just tell you how to do it, but that's just the reality of the maturity of this effort. No one yet knows the best way to do it. Rather than waiting for someone else to eventually figure it out and then maybe share their results, I'm glad we're getting to see the whole process unfold in real time. The more info that gets shared sooner, rather than later, the more likely we are to see real solutions sooner. The last thing we need is for those doing the real work to get pissed off and stop sharing their insights as their projects progress.