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5132 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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Since I'm running 36 SE/CALB cells with an AC31 I can give you some feedback. Fully charged I'm resting around 120 volts. Moderate regen of 100 or so amps can drive the voltage to 124, higher regen around 200 amps will hit 126, BUT, if your cells are colder their resistance is higher and voltage will be higher on regen, I've seen 127 so far, my controller is set for 40% regen, (neutral braking).
I live at the bottom of a valley so I have to travel uphill right away and wont' be regen'ing until after I've "burned" a bunch of electrons. Opportuity charging won't be topping off the cells so I'm not too concerned about hitting the cut-off. If CALB' higher AH cell wer the same height as the 100's, I'd use them but their 11-12" height starts giving me fitment issues. China Hi-power's new format is shorter but heavier, and weight is even more critical for me than size.:(
 

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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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I've heard of no issues at all with the SE/CALB cells, generally they are considered better than TS. I've had no problems in the 8 months I've used them. I've taken them as low as 1.77V under load and pushed a few to 4V temporarily, I've pulled 5.5C from them for a few seconds, they seem fine. The only bad cells I've heard of were the results of faulty BMS over discharging them, and some of them even survived that abuse.
I've had a few controller shutdowns and there is a voltage spike, the programmer recorded a max of 140V, but a short high voltage spike like that won't hurt the batteries.
 

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I live at the bottom of a valley so I have to travel uphill right away and wont' be regen'ing until after I've "burned" a bunch of electrons. Opportuity charging won't be topping off the cells so I'm not too concerned about hitting the cut-off.
It may not matter. If you have 38 cells sitting at 3.3 volts after driving for a while, 150-200 amps of regen will drive the cell voltage to 3.40 or higher which is getting pretty close to the cutoff. If you can keep the cells warm you might be ok, but just be ready for controller shutdowns since you'll be right on the edge.
 

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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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