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5136 Views 25 Replies 6 Participants Last post by  helluvaengineer96
hey ya all heres some interesting e-mail that I recently had with jon at grass roots in neveda comments?

Dear Lou-ace,
I have spent a good deal of time evaluating various sources for lithium
batteries. As it turns out there are quite a few lithium battery
manufacturers. However, finding one source that is the best value for an
Electric Vehicle is daunting. After a lot of e-mails and phone
conversations we have concluded that Energetech Lithium-ion Phosphate
(LiFePO4) battery packs will give you the best value in performance,
construction, energy density, longevity, price and delivery. They use
Chinese made HiPower lithium batteries that as you may know need special
care when being charged and discharged. Therefore, special due diligence
has been exerted to find a superior Battery Management System ‘BMS’ which
will assure maximum battery life. We know the one thing that you want for
your vehicle is a reliable battery pack that will assure you years of
satisfactory driving pleasure. Energetech has been in business for 34
years and will give a full two years replacement warranty on all batteries
that are not mis-used. You will need a battery charger program for lithium
batteries I think the Zivan chargers are the best but you may have to have
yours reprogrammed.
Yours Truly,
Jon
702 2777544
www.grassrootsEV.com





> Hi Jon, lou-ace here, greetings from the northwest! I'm presently
> converting a small truck to electric ( ADc 9" motor installed, curtis
> 1231c
> controller, zivan charger, switches ect), and was planning on using trojan
> t-145
> batt. pack. I'm intriqued by your li-po battery advertised on the
> grassroot
> site. can you fill me in more on it? who makes it? is it compatible with
> conventional DC charging methods? Frankly it sounds to good to be true (
> although expensive). what track record/ history is there with this kind of
> technology? ect. rsvp to this e-mail address please. thanks........
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I just ordered the AC50 kit and mounting kit for a fiero from grassroots. This is a good bit of capital to spend without ever meeting someone.

Has anyone here had any experience with grassroots?
What did you order?
How quickly did it ship?
Was Jon responsive after the sale?

Thanks in advance for any input. Just want to increase my confidence level of the purchase. Also, I have the batteries/chargers/BMS to still order and I am not sure if I should spread the risk out or stay with the same vendor.
 

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Too true... Being concerned never really occurred to me until reading some of the posts on here. I've not seen anything negative about grassroots, but there seems to be a number of complaints for various suppliers. Just getting involved so not sure if it is a few sour grapes or a sign of the ecosystem.

Hate to rush in but once I decided to build one........Just really want to get my hands dirty so I can start learning from my mistakes. :)


Just an observation.... but maybe u should have asked before buying...lol :eek:....just sayin'.....
 

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RE Farmer,
Thanks for the positive feedback.
Jon emailed me yesterday he received my check and we just started working out the details for factory customizing the controller.

I hope to talk to Curtis about setting up the controller to discuss factory programming.

Questions: Hopefully I'll find out soon enough from Curtis... but what were the factory programming variables? Just battery voltage?
I've seen folks use 108 V nominal or greater with the Curtis but I can not find any Curtis documentation to support this... Hate to kill the MOSFET with too much voltage potential across the source/drain.
Also, any idea what must be done if I change the battery level at a later date? Does the controller need to be sent back to factory?

Hope your house has stayed leak free.

Regards,
Helluva

I ordered the AC31 from Jon and received good service/no problems. It's been a over a year so the details are a little fuzzy, but it pretty much shipped when my check cleared. I suspect the motor/controller was drop shipped from HPEVS and not from stock at GrassRootsEV but I'm not sure. Jon was quite friendly and usually responded to emails w/in a day. I think it took a little over two weeks to receive the kit by motor freight from the time I mailed the check. I'm pretty sure he emailed me when the kit shipped, but I had lots of other things (like putting a new roof on my house) going on at the time.
 

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RE Farmer,
Which LiFePo4 do you plan to use?... Staying away from the high end of the charge curve will have a bigger impact with some batteries vs others.
After talking to Jon (At grass roots) I came up with the following matrix for a few different batteries. BTW Jon has not seen this yet, so he may not agree..:eek:

Not a chemist... So I can not guess what charging a battery to a lower than recommended voltage will result in from a charge capacity standpoint.

Examples:
In the table 108.8V (34 battery string) for TS and CALB.
TS cut off voltage happens at 85V.
CALB cut off voltage happens at 68V. (To be honest after looking at the actual discharge curve in the data sheets, I'd say they cut off voltage for both is closer to the one speced by TS, CALB is not lying but they are picking a low spot on a very straight line.).

Also note that TS recommended charging voltage is 3.8V, therefore at 35 batteries you have exceeded the 130 V limit. Meaning you are limited to 34 batteries.

The CALB recommended charging voltage is 3.6V, therefore you can go up to 36 batteries and still just be under the limit...I'd stick with 35 in the string to be safe.

I am sure the limitation in the controller is the controller's MOSFET's Drain Source (Or Gate Source) voltage. I've seen exceeding this spec cause real world component failures... (Tho I don't know how much margin the folks at Curtis have build in... at high temps it might be none.) I'd love to know what device they are actually using in there so the data sheet could be pulled.

To do what you want you may be better off with a CALB battery with its lower charge voltage and going with more cells...This way your nominal voltage is 7 V higher and you don't have to worry about exceeding the Curtis's voltage limit while charging. This may be what you were already thinking.

Note: I am new to the game here just going by what the lie...I mean data sheets say.

That's pretty much my plan - to install 38 cells and stay away from the steep parts of the charge/discharge curve to enhance longevity by only charging to 128Vdc. Even if I did end up charging over 130V, I figure briefly turning on the electric heater would "eat up" that surface charge real fast, quickly dropping the pack voltage back under the 130V cut-off.
 

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What do you plan to do for the BMS?
I've only started to look, but most BMSes support 3.6 or 3.8 V for charging.

I'd prefer the CALB, but TS are an option. I'd go to higher AH cells, but their increased height start making installation problematic.

Since the nominal voltage is 3.2-3.3V, i could easily charge 39 cells to 3.3 and stay below 130V. 130V/38 cells is 3.42V; well within my parameters. Like I said above, I plan to stay away from the max. capacity of the cells to increase longevity.
 

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Thanks for the links...
Unfortunately, I am not that luckily...I am very good regression tester, I break what ever touch... Hence I must implement with BMS to avoid disaster.:) Plus my battery packs we be very hard to get at for manual intervention.

Please post your results, I'll be very interested in the results.

I've yet to settle on my battery pack... I could easily meet my requirements with inexpensive lead-acids... but the more I figure the bigger the bill gets.

I don't plan on using a BMS. If cells aren't abused (over/undercharged) several people have reported the cells stay well balanced if they start out that way. If fact, I seen some reports that they tend to balance themselves if the extremes of the charging curve are avoided. This is a highly contentious subject, but that's where I stand.

For more about this issue i recommend the following sites if you haven't already discovered them:

http://media.ev-tv.me/news111309-1280.mov

http://groups.yahoo.com/group/ThunderSky/
 

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JRP3,
Have the CALBs given you any issues? how long have you had them? I heard of high fall out in the first year (this could be from folks mistreating them).

I really want to go with the CALBs because they fit extremely well for my application... Hard to justify $4K just because they fit better, esp if there are quality issues.

BTW: Great spreadsheet.. I was up late last night tinkering with it... It really helps in translating available power into usable distances (for specific vehicles)...I have a few questions about the acceleration component, but will tinker with it a bit more before asking.

Curtis shutdown: I've noticed several here mention the Curtis will shutdown at 130 V.. I am betting this means the Curtis disconnects the Solenoid. Is this true?
One area of concern would be, if there is a lot of current flowing when that Solenoid is opened, then there will be an inductive voltage spike on the battery side of the solenoid. The lead acids would probably just absorb it but I am not sure how the LiFePo4's would like it... To be safe it might be a really good idea to add a 130 V clamping diode on the battery side. Question is how big? I little 5W 1N5362 would definitely not be big enough. Since it is a transient spike a 1N3344B might work, want to be careful with the leakage current. Anyway I'll spend some time looking for a good fit for this.
Since high voltage will probably only occur during charging and there won't be any current going across the Solenoid then it could be a moot point.
Something else to considered, if clamping diode is big enough it could shunt excessive regen voltage harmlessly to GND preventing Curtis from disconnecting the Solenoid.


Regards..

I would also recommend the CALB cells for the flatter curve, and I'm also not using a BMS.
 

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MN,
Guess I am taking the "recommended" part a bit too seriously. Hazard from old occupation. :eek: I am sure the TS could be charged at 3.6 V vs 3.8 V...but with so little info on the data sheet it is it really hard to tell what the trade-offs are. I am not even sure why TS recommends 3.8 V and CALB recommends 3.6 V... Could be significant.. don't know.

I do agree that the TS could be charged at 3.6V like the CALBs.

Charging to 3.3v is not going to give you a full cell. When you fully charge a cell I would aim for nothing less than 3.4v, at that point you still might leave a little behind and need to float the charge at that voltage a little longer at a lower voltage to ensure a full charge. Keep in mind that 39 cells will leave you with no headroom for regen. The controller shuts down at a 130v which should be the max the cells will ever reach, not the nominal voltage. The nominal rating is 108v based on lead acid cells but the max under any 'on' condition should be 130v.

helluvaengineer96, The recommended charging voltages don't really make much of a difference because its all LiFePO4 and IMHO You don't get really anything past 3.6v except for some headroom for balancing shunts to operate with if that is your mode of operation. I wouldn't base number of cells on that. There is no reason that I see to why someone would limit themselves to 34 cells because they chose TS.
 

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Cheap way to possibly prevent Controller cut off and protect batteries from a transient voltage spike.

Something like 1V5KE150(C)A or 1V5KE130(C)A

http://www.fairchildsemi.com/ds/1V/1V5KE100A.pdf

Might have to experiment a little to see which works for you battery voltage. I'm probably going to start with the 150 (with 35 batteries with charge voltage of 126V) who just starts to conduct a little at 128V. This might no prevent the controller from shutting down.. a few trade off here.

I'll keep looking for something with a more exact cut off, but this is an inexpensive piece of mind. These are only 1.5KW so they only protect against a small amount of current.. Just transient protection, Won't save you from the charger going crazy ect....

BTW: I just notice that I am way way off the topic of the original post.. Sorry.


JRP3,
Have the CALBs given you any issues? how long have you had them? I heard of high fall out in the first year (this could be from folks mistreating them).

I really want to go with the CALBs because they fit extremely well for my application... Hard to justify $4K just because they fit better, esp if there are quality issues.

BTW: Great spreadsheet.. I was up late last night tinkering with it... It really helps in translating available power into usable distances (for specific vehicles)...I have a few questions about the acceleration component, but will tinker with it a bit more before asking.

Curtis shutdown: I've noticed several here mention the Curtis will shutdown at 130 V.. I am betting this means the Curtis disconnects the Solenoid. Is this true?
One area of concern would be, if there is a lot of current flowing when that Solenoid is opened, then there will be an inductive voltage spike on the battery side of the solenoid. The lead acids would probably just absorb it but I am not sure how the LiFePo4's would like it... To be safe it might be a really good idea to add a 130 V clamping diode on the battery side. Question is how big? I little 5W 1N5362 would definitely not be big enough. Since it is a transient spike a 1N3344B might work, want to be careful with the leakage current. Anyway I'll spend some time looking for a good fit for this.
Since high voltage will probably only occur during charging and there won't be any current going across the Solenoid then it could be a moot point.
Something else to considered, if clamping diode is big enough it could shunt excessive regen voltage harmlessly to GND preventing Curtis from disconnecting the Solenoid.


Regards..
 
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