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5131 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'm planning to try one extra cell for 37 total but expect that might shut down the controller with strong regen on a cold day. The answer may be to use the brakes more instead of regen until the cells warm up a bit, which they do after driving around for a while. Winter temps will probably make this worse, but once the salt starts hitting the roads I won't be driving the car anyway. I'll let my ICE take the hit.
 

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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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