# First E Kart Electric Go Kart Project



## electron bom (Dec 4, 2014)

Cool project you have there!
I have a ME1003 + Alltrax 7245 in a 530lb kart and it has nice power, but nothing spectacular. I currently have it set up at 48V and 260A, 1:3.9 gear ratio and 19" tires net me 28mph top speed and acceleration much like a 400cc ATV. I run a #50 chain as well.


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## 67BGTEV (Nov 1, 2013)

Cool project. I don't have any feedback. Where did you buy the frame?


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## wesleyb82 (Sep 17, 2014)

Hey thanks for replying it's good to hear your experience and get my expectations right for this thing.

Anyway I got the frame off Craigslist. Been looking for months and when this one came up I jumped on it.

Just got a AXE4834 controller and 200a contactor for $200. Next looking at a new eTek for $300. Then I may bite the bullet and get (4) 55ah AGM deep cycles for $420 or I might go for 35ah which are $240 total, $180 less. I'm looking for 30-45m run time at a minimum. I expect to be running this thing around 15mph most of the time to keep pace with my sons gokarts and since I think I will have it geared for 30mph I think I will be pulling 50% or 5kwh at 48v which is about 100a and I have found with our other karts motors/sla's and typical riding that it normally takes an hour to run down 12ah and we normally draw about 20-25a at full throttle. So if these numbers translate to this project I would need 50ah to last an hour. Just wondering if someone with real world experience can help me make the 55ah/35ah decision.

Possibly the biggest challenge with this build will be reinforcing the frame to hold the batteries. I was thinking diamond plating under the bottom of the kart then maybe square tubing along the bottom to stiffen it up but there is very little ground clearance to start with. I could also weld the wings to the frame (since one end is bolted and the older end is a tube in tube with a set bolt) which is possible but I would have to pay someone to do this and I don't know if this is enough to hold up at least 80 lbs of batteries on either side. Any help or guidance here is much appreciated.

Finally I think I have decided to run #50 chain. I have read that small #50 sprockets can cause binding so I think I will run no smaller than a 13T on the motor, then since my rear tires are 10" I will run around a 40t in the rear which is 8.3" tall. Idk if after you lay the chain on and then apply about 400lbs if the chain will hit the ground so unless someone can really point me in the right direction I will measure it after it is assembled and buy a rear sprocket last. The speed calculator puts me at 31mph with 3200rpm, 10" tires, 13t and 40t. Am I headed in the right direction?

Thank you I need help and appreciate any and all feedback of any kind

EDIT: Oh almost forgot that since I have read that AGM's can comfortably deliver 5C, 55ah would be more appropriate for this 300a application. Is that correct?


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## Duncan (Dec 8, 2008)

Hi Wesley
Why not look at RC cells (lithiumpoly) for your cart?
Much much lighter more power and cheaper


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## wesleyb82 (Sep 17, 2014)

Duncan said:


> Hi Wesley
> Why not look at RC cells (lithiumpoly) for your cart?
> Much much lighter more power and cheaper


The first Li-Polymer cell I found was 3.7v 10ah capable of 2c burst. Just to get a 10ah 48 pack capable of 20amp burst the cost is $454. To get to 100amps burst the cost is $4540. Am I missing something here?

http://www.all-battery.com/polymerli-ionbattery37v10000mah30104.aspx

EDIT: Just found a 10c cell for $38: http://www.all-battery.com/37volt-10000mah5c_10cli-polycell-30123.aspx but that is still far from 55ah AGM (even though the lead AH is actually lower than 55ah of course) and then this is 100a max when this motor could draw 300a?


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## electron bom (Dec 4, 2014)

FWIW I use a 10T drive sprocket with my #50 chain and I've had no issues. I'm using the same aluminum L bracket you cite as well. It is a nice piece. What do you think about these: http://www.hobbyking.com/hobbyking/...y_nano_tech_5000mah_8S_65_130C_Lipo_Pack.html


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## Duncan (Dec 8, 2008)

Hi Wesley
Just a quick look and I got this
http://www.hobbyking.com/hobbyking/...ech_A_SPEC_4000mah_12S_65_130C_Lipo_Pack.html
44v 4Ah - 65C
That is 260amps!
$160
1.4Kg

I would suggest running two or three of these in parallel


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## wesleyb82 (Sep 17, 2014)

electron bom said:


> FWIW I use a 10T drive sprocket with my #50 chain and I've had no issues. I'm using the same aluminum L bracket you cite as well. It is a nice piece. What do you think about these: http://www.hobbyking.com/hobbyking/...y_nano_tech_5000mah_8S_65_130C_Lipo_Pack.html


Hmm interesting. After some digging around I found these: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9176

For $404 I could get a 17lb 48v 25ah pack capable of 150a 10 second discharge (5ah @ 30c) but the AH is low and I would be pushing the battery draw by double. Is this really a viable option? Have others used these batteries with this application?

EDIT: Thank you for mentioning the 10T and the bracket. I was really debating the bracket but now you have me sold thanks.


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## RIPPERTON (Jan 26, 2010)

110C enough ?
don't buy RC packs
get single cells with tabs at both ends.
And the top of charge voltage is 4.2v

http://ygspower.com/prosecond.php?pid=5

That Hobby King pack looks like it has an improved chemistry and can be charged as 2x 6s but Turnigy had a bad batch a while ago and lots of people got ripped.
Id wait till you get some customer feedback before buying Turnigy.


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## wesleyb82 (Sep 17, 2014)

RIPPERTON said:


> 110C enough ?
> don't buy RC packs
> get single cells with tabs at both ends.
> And the top of charge voltage is 4.2v
> ...


Thank you for your input but you said no RC packs and left a RC pack link? Do you have a link to the single cells with tabs? Thanks again


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## nimblemotors (Oct 1, 2010)

How about 1000amps, A123 M1 cells...


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## Duncan (Dec 8, 2008)

Hi Wesley
Re types of cells

First - not lead acid - too heavy, low performance 
Could be useful as your "floor pack" that you charge your "kart pack(s)" with

Then - what?

RC type cells are cheap, readily available and will do what you want

Pouch type cells like the A123 are going to be more reliable - but a lot more expensive 
and not as easy to get hold of


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## wesleyb82 (Sep 17, 2014)

Ok thank you. But if I used rc packs could I use a bms or the like to charge all 6s's at once still installed on the kart? If so can someone recommend a bms? Finally what max discharge rate could I get away with? Could I use a 200a max cell on an etek which will operate at 100a most of the time but might see 300a briefly?


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## Karter2 (Nov 17, 2011)

wesleyb82 said:


> Hmm interesting. After some digging around I found these: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9176
> 
> For $404 I could get a 17lb 48v 25ah pack capable of 150a 10 second discharge (5ah @ 30c) but the AH is low and I would be pushing the battery draw by double. Is this really a viable option? Have others used these batteries with this application?
> s.


Your maths is a little off...theoretically , you could get that 150A from just a 5 Ahr pack.
A 25Ahr pack of those 20 C cells could give you 500A for 2-3 mins !
In reality, you should not expect much more than ~ 200A from that size pack if you want it to last more than a few dozen cycles.


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## wesleyb82 (Sep 17, 2014)

Oh yeah... long day. You're absolutely right thanks


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## RIPPERTON (Jan 26, 2010)

wesleyb82 said:


> Thank you for your input but you said no RC packs and left a RC pack link? Do you have a link to the single cells with tabs? Thanks again


Theres a difference between a cell and a pack.
The link I gave was for individual cells (3.7v) the first section from 15C down to 55C.
Below that it goes up to 7.4v which is a pack of 2 cells in series.
Don't forget the 3.7v is a nominal value. You have to factor for 4.2v when you build your pack.

Im just suspicious of the built packs in heat shrink. They are often dodgy quality.
YGS don't have a photo of an individual cell but this is what they look like, no heat shrink


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## wesleyb82 (Sep 17, 2014)

I found 6s 5AH 30c (40c burst) packs for $32 each. 2 in series makes 48v, then 6 of those groups in parallel make 30ah. The 12 pack total cost is $384 for 48v 30ah. 6 groups in parallel are handling 100a nominal or 16.6a per pair, or ~3c per pack which is 1/10 the nominal C rating. Then 300a burst which is 50a per pack or 1/4 the burst C rating. 2 of these groups in either side would make 48v 60ah packs for $768 + handling and further reduce the pack amp load.

I found a 6 block tree to charge 6 batteries at once. Charging seems risky and difficult to manage and thats if it actually works well and stays in balance: http://hobbyking.com/hobbyking/stor..._charging_Board_for_6_packs_2_6S_HXT4mm_.html

I am leaning towards 50 or 55ah AGM Deep Cycles as of now

Any advice or guidance is appreciated


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## Tomdb (Jan 28, 2013)

how about building the cart with cheap batteries. Then getting lipo once you are bored.


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## wesleyb82 (Sep 17, 2014)

Yes maybe you are right thank you very much. Cheaper and able to take more abuse although the weight might be a challenge.

I may even go with a smaller than 55ah (~40a lb ea) and get 35ah (~30 lb ea) but I want to get a feel for run time on either 55 or 35ah. Can anyone help me with this? Also is it even easily possible to get 300a out of a 35ah (@ 8.5c)?

Thank you all for your help


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## Duncan (Dec 8, 2008)

Why not start with a Lipo pack?
Lead will cost more and be very disappointing


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## major (Apr 4, 2008)

wesleyb82 said:


> I may even go with a smaller than 55ah (~40a lb ea) and get 35ah (~30 lb ea) but I want to get a feel for run time on either 55 or 35ah. Can anyone help me with this? Also is it even easily possible to get 300a out of a 35ah (@ 8.5c)?


Here is a test which I ran on 4 new Odyssey PC925 AGMs, about the best you can buy in its class, rated 26Ah and 330cca. Subsequent testing confirmed they can indeed deliver 300+ Amperes. So at around 6hp average, you'd see about 6 to 7 minutes run time.










BTW, your plan to use a brushed PM motor might survive Pb-acid, but with a decent size Lithium battery, will likely result in motor failure.


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## wesleyb82 (Sep 17, 2014)

Haha the conflicting opinions back to back are not making this easier.

Major I've read about 500 of your posts so it's an honor.... Very interesting that you got about half of the rated AH at that discharge rate. Ay i ay. Why do you say Lithium will cause a motor failure?

Well I don't want to spend $2k total and lug this thing around for it to run for only 10-15m so I might go big and get 55ah. All other battery options I have found besides this dicey RC option have exceeded my budget. I have such a bad feeling that I am going to eat the $400 battery cost and have no where to unload them when the time comes to try to sell them...


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## major (Apr 4, 2008)

With PB, you'll likely drain the battery before overheat the motor. Decent Lithium will give you enough energy to toast the motor. Using bigger Pb may also toast the motor; higher load and a bit longer time.

I've made some nice EVs with Pb. But they used the best Pb. And were short range. Cheap Pb will disappoint you and waste your $.


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## RIPPERTON (Jan 26, 2010)

Strangely the electric Sodi Karts we have here in Newcastle have 4 massive lead acids in them and they go pretty well. Only problem is the weight doesn't let the kart frame twist so it can tripod around the corners so the tires skid a bit.
Even with lithium you are going to be heavier than a petrol kart


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## wesleyb82 (Sep 17, 2014)

Hm trying to figure out what tripoding means but anyway would you consider these Pbs junk?
http://www.interstatebatteries.com/1/1/8807-12v-50ah-sla-deep-cycle-insert-sla0190.html
http://www.ebay.com/itm/131179320949

I am guessing I will get the kart out... 20-40 times in the next year or two. 

Also if the lead batteries discharged about half the rated AH at 100amps what percentage of AH rating would you say the average lithium batteries would discharge? 3/4? More? Trying to figure out if a 20AH lithium battery is around the same real world capacity as a 55ah Pb.

Thanks for helping me along this is my first big expensive project


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## major (Apr 4, 2008)

You essentially get full rated Ah from Li. Search for Peukert to see recent discussion here.


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## Karter2 (Nov 17, 2011)

RIPPERTON said:


> Strangely the electric Sodi Karts we have here in Newcastle have 4 massive lead acids in them and they go pretty well. Only problem is the weight doesn't let the kart frame twist so it can tripod around the corners so the tires skid a bit.
> Even with lithium you are going to be heavier than a petrol kart


I have never seen a rental kart that was either light weight or able to "Tripod"
( weight jack) the chassis. Electric or petrol.
Tyres are also chosen for long life/low cost rather than grip.
But it doesn't matter if all the karts are similar so that racing is close and driver ability can prevail.
One problem with self built karts , is finding a track that will let you on .
Current liability insurance requirements makes it risky for track owners to let any unusual karts run, especially if there are other karts already using the track.


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## wesleyb82 (Sep 17, 2014)

http://www.ebay.com/itm/181656393488

This battery seems it would be a perfect fit! Any thoughts or suggestions on this?


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## Tomdb (Jan 28, 2013)

re purposed chevy volt pack. and just a bleeder board bms system on it. 

so 45ah. and your stated max draw of 300A

This is 300/45 = 6.7 C i would suspect these cells to heat up alot under this kind of load, however i have never seen clear data on this so i might be wrong.

Sorry im wrong. This battery will easily handle it.

http://www.diyelectriccar.com/forums/showthread.php?t=109698&highlight=chevy+volt+battery


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## wesleyb82 (Sep 17, 2014)

Wow great link, thank you so much!


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## major (Apr 4, 2008)

wesleyb82 said:


> http://www.ebay.com/itm/181656393488
> 
> This battery seems it would be a perfect fit! Any thoughts or suggestions on this?


Don't trust that seller.


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## major (Apr 4, 2008)

major said:


> Don't trust that seller.


Hi, I am on the road and shot that reply off my phone while at lunch. Hold up in a motel now, so: That individual has been banned here under several user names, like crusin, 1eyedcruiser, and so on. I would not do business with him, and advise others to stay clear. He gives the hobby a bad name. See this thread: http://www.diyelectriccar.com/forum...-45-and-ac-115177.html?highlight=1eyedcruiser Also search for other threads by his user names.

BTW, I still have have some nice EnerDels for sale. See my FS thread in the classifieds.


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## wesleyb82 (Sep 17, 2014)

Oh no.... that sucks. I thought this pack was the golden solution for my project.

Does anyone know anything about this seller?
http://www.ebay.com/itm/45Ah-Lithiu...eaf-/261705212143?hash=item3ceed8a0ef&vxp=mtr

EDIT: Just found the EnerDels thread yes this looks great I might order 2 I just need to read the thread and figure out the BMS situation there.


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## wesleyb82 (Sep 17, 2014)

Hmm Found these....
http://www.ebay.com/itm/48V-40Ah-Qt...323?pt=LH_DefaultDomain_0&hash=item2a4bb71db3
Still need to figure out how to charge these cells.


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## Tomdb (Jan 28, 2013)

go for hybrid parts, quite some people have gotten leaf cells from them, and no real bad news from them.

Dont muck around with cheap chinese cells that are rebranded or B-grade


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## wesleyb82 (Sep 17, 2014)

Ok thats great thanks. Do you have a link or a brand name or a company name or anything? Something to go on I'm more or less lost here.


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## Tomdb (Jan 28, 2013)

the same as your ebay auction you posted.

http://hybridautocenter.com/HAC4/index.php?option=com_hikashop&ctrl=product&task=show&cid=79&name=2kw-h-lithium-battery-pack-chevrolet-volt-45v-45ah-12-cells&Itemid=605

I would just add an simple pack monitoring setup. Also charge it with a balance charger.


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## wesleyb82 (Sep 17, 2014)

Ok thats great thank you. Do you have any links or names of these parts or makers of these parts or anything for me to work off of? I have experience with lead batteries so this BMS and monitoring parts are new to me. Thanks again


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## Tomdb (Jan 28, 2013)

here is an tutorial on charging http://endless-sphere.com/forums/viewtopic.php?f=14&t=52240

a "noob" guide to lipo drivetrains, ebike because of the lower voltage

http://endless-sphere.com/forums/viewtopic.php?f=16&t=26619

some more reading on batteries
http://www.ypedal.com/Lipo/Lipo.htm


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## RIPPERTON (Jan 26, 2010)

wesleyb82 said:


> Hm trying to figure out what tripoding means


Second post down is kind of what weight jacking or tripoding looks like except this guy is in the rain with slicks and hes pushing to the outside,
but theres a lot of good reading on this page too.
Because karts don't have a differential they need to lift the inside rear wheel so theres no scrubbing of tires. 

http://forum.miata.net/vb/showthread.php?t=459244&page=3


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## wesleyb82 (Sep 17, 2014)

I purchased (2) 48v 45ah Chevy Volt cells from Sales Hybrid Auto Center. Might be too many AH's for this project but I'm going big and could use these cells for other future projects. I may run one pack at a time and keep the kart weight super low. My only concern is if I want to move to 72v it may be impossible with these 48v packs. Anyway so far they have responded to my questions within a day and have suggested using the following BMS and charger for these packs. 

Can anyone yay or nay these suggestions? More than anything I want to play it safe with these packs so slow charging and is OK but of course accurate charging is important as well but also if it's OK to partially charge to 4.1v to play it safe I am OK with that as well. I also want to keep the charger around $150-200 USD if I can. 

http://www.ebay.com/itm/44V-48V-50-...989?pt=LH_DefaultDomain_0&hash=item3384f6bd8d

http://www.ebay.com/itm/AC110-220V-...672?pt=LH_DefaultDomain_0&hash=item1c4d498740


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## Tomdb (Jan 28, 2013)

are you getting packs with the bms cabling? if you are you might be able to make an adapter to run simple RC style battery monitoring and chargers.


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## wesleyb82 (Sep 17, 2014)

The packs come with the factory BMS harness which can be spliced to work with any BMS from what I understand.


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## Tomdb (Jan 28, 2013)

http://www.hobbypartz.com/75p-1220-charger.html?gclid=CNa3z9_N57ICFayPPAod10MAPw

This is a possabilty


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## wesleyb82 (Sep 17, 2014)

Anyone have any other BMS suggestions? < $200 and safe? Thank you much!


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## major (Apr 4, 2008)

wesleyb82 said:


> Anyone have any other BMS suggestions? < $200 and safe? Thank you much!


You could read up on the subject here: http://liionbms.com/php/bms-selector.php


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## RIPPERTON (Jan 26, 2010)

Tomdb said:


> http://www.hobbypartz.com/75p-1220-charger.html?gclid=CNa3z9_N57ICFayPPAod10MAPw
> 
> This is a possabilty


I don't know why they call this a "balance" charger. All it does it monitor the individual cell voltages but doesn't actively balance them at top of charge so they are all equal.


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## major (Apr 4, 2008)

RIPPERTON said:


> I don't know why they call this a "balance" charger. All it does it monitor the individual cell voltages but doesn't actively balance them at top of charge so they are all equal.


Yes it does. That is the Thunder 1220. I have one. Kinda slow balance on large cells.


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## wesleyb82 (Sep 17, 2014)

major said:


> You could read up on the subject here: http://liionbms.com/php/bms-selector.php


Wow cool link thank you.

Looking at the MiniBMS and it seems a 12s system costs about $350 + charger. Am I correct that I can use the 13 pin factory BMS harness with this system? Connect each module onto the first and second bms wire, then the second and third, etc (each BMS wire would have 2 modules connected) which would monitor the pack during usage and charging. I plan on using 1 system on the factory BMS harness and use and charge one pack at a time. Only issue I have read of so far on their docs is disconnecting main power before removing BMS and that it needs an acc 12v source. Any feedback? Thank you


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## wesleyb82 (Sep 17, 2014)

major said:


> Yes it does. That is the Thunder 1220. I have one. Kinda slow balance on large cells.


Hmm but should only take ~ a couple hours for these 45AH packs at 20A, right?


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## Tomdb (Jan 28, 2013)

yes around 45/20= 2.25 hours. Excluding balancing


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## major (Apr 4, 2008)

wesleyb82 said:


> Hmm but should only take ~ a couple hours for these 45AH packs at 20A, right?


No, that would be 800 to 900W. Max is 300W. And that is for bulk charge. I'm not sure of the balance procedure for Lithium. I think I'll set it up on a 12S EnerDel and find out tomorrow.


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## wesleyb82 (Sep 17, 2014)

I can wrap my head around MiniBMS and it seems to do what I want-LV alarm and safe charging so I think I'm going with that. Getting the AC relay, head board and (3) 4s boards for $235 shipped.

Can someone make a charger recommendation for < $150? Speed charging the 45ah is not a priority, 2-4 hours would be fine.

As per the MiniBMS docs it said a simple DC source would work (such as the link below I believe) but instead of guessing I'm hoping someone could make a recommendation. 

Thank you for your help so far I really appreciate it.

http://www.ebay.com/itm/Output-DC-4...142?pt=LH_DefaultDomain_0&hash=item418305615e


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## major (Apr 4, 2008)

Be careful. 48 Volts won't fully charge a 48V battery. You need to check the number of series cells and the V/c at 100% SOC.


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## wesleyb82 (Sep 17, 2014)

Max charge should be 4.2v X 12 = 50.4v, right?


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## major (Apr 4, 2008)

major said:


> Yes it does. That is the Thunder 1220. I have one. Kinda slow balance on large cells.


Really, really slow, but I think it does try to balance. Been at it for a day now and still a long way to go. I'd have to say it is not useful to balance more than about 100mV on 5 or 6 Ah. Even that could take a day.

Does anybody have a better manual or operational information about the Thunder 1220? All I have is some old scanned pdf which sucks.


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## major (Apr 4, 2008)

wesleyb82 said:


> Max charge should be 4.2v X 12 = 50.4v, right?


I guess so, if you have a 12S battery with cells needing 4.2V/c. 

But if the absolute maximum of the power supply is 50.4V, then it may take forever to actually bring the battery voltage to 50.4.


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## wesleyb82 (Sep 17, 2014)

Found this guy, 5a 0-60v adjustable dc power supply. But I wouldn't set the voltage to my target 50.4 I would set it higher.... to 60? and once the first cell reaches HVC the charger would be shut off by miniBMS?

Ay i ay I have a bad feeling about this

http://www.ebay.com/itm/60V-5A-5AMP...468?pt=LH_DefaultDomain_0&hash=item51b2412bc4

EDIT: Or this guy, 60v 10a
http://www.ebay.com/itm/600W-60V-10...652?pt=LH_DefaultDomain_0&hash=item58bf8a0d34


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## major (Apr 4, 2008)

My recommendation is to use a charger (or power supply) with the proper cutoff voltage and also the BMS which will cut off the charger on a single cell HVC. Better safe than sorry.

Check out Delta Q chargers. Some on eBay, new, for $300 to $350. 18A. That is what you'll need to hit your charge time target. And it will be a hellofalot more durable than those power supplies.


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## Sunking (Aug 10, 2009)

wesleyb82 said:


> Max charge should be 4.2v X 12 = 50.4v, right?


*NO!*

While it is true you can take LFP up to 4.2 vpc. but does so with great stress, and if you have a BMS is over charging the crap out of them. Try 3.6 to 3.65 to 100% SOC, but no reason to even go that high and does not gain you really any useful capacity. The ride from 3.6 volts to 3.4 volts is seconds. 

If you only charge to 90% should increase you cycle life 50%, and all you give up is a few seconds of run time.


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## major (Apr 4, 2008)

Sunking said:


> *NO!*
> 
> While it is true you can take LFP up to 4.2 vpc. but does so with great stress, and if you have a BMS is over charging the crap out of them. Try 3.6 to 3.65 to 100% SOC, but no reason to even go that high and does not gain you really any useful capacity. The ride from 3.6 volts to 3.4 volts is seconds.
> 
> If you only charge to 90% should increase you cycle life 50%, and all you give up is a few seconds of run time.


I thought he was using NMC from the Volt pack, not LFP.


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## Sunking (Aug 10, 2009)

major said:


> I thought he was using NMC from the Volt pack, not LFP.


If that is the case I stand corrected.


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## wesleyb82 (Sep 17, 2014)

major said:


> My recommendation is to use a charger (or power supply) with the proper cutoff voltage and also the BMS which will cut off the charger on a single cell HVC. Better safe than sorry.
> 
> Check out Delta Q chargers. Some on eBay, new, for $300 to $350. 18A. That is what you'll need to hit your charge time target. And it will be a hellofalot more durable than those power supplies.


Major, thanks a lot for taking the time to help me I really appreciate it. 

I'm going to see if I can get a Delta Q QuiQ programed with a 4.2v 12s charging algorithm. I read that someone on the forum does this for free. Need to find that post again.

Or this charger which I read can be ordered with any termination voltage
http://www.headway-headquarters.com/48v15a-battery-charger-lifepo4/


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## major (Apr 4, 2008)

I'd be careful with headway headquarters. Sounds like the place involved in some shady deals a few years back. Travis (aka member frodus) is the guy to program the Delta Q and is in the area of headway hq, so ask him about them. Also, I could do the Delta Q program if he can't. Check with him before you buy.


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## wesleyb82 (Sep 17, 2014)

After following the advice given here I purchased (2) 48v 45ah Chevy volt packs from Sales Hybrid Auto Center. Good experience there packs were received well. I also ordered a mini-BMS system (Dimitri was extremely helpful). Finally I ordered a 15a 50.4v terminating charger from Headway. Took a few weeks to get here but it looks solid.

After many late nights I am completing the build phase but I have a question before we start running it. 

The only pack monitoring during operation that I am currently planning on relying on is the controller under voltage protection. Is this a good idea or not? Based on previous advice here I plan to stop discharging at 42v or 3.5v X 12. Also, I have an Alltrax 4834, does anyone know if the moment the controller reads this voltage it will simply cut out? Even under brief voltage sage? Alltrax support has not responded to my email question about this... I was not going to use the mini-BMS for under volting since the alarm triggers at 2.7v but besides that I have very limited space on the kart. I have considered an entire pack voltage gauge on the control box (I will most likely at least do this) and also possibly a lipo alarm splice into a factory harness. 

Finally I think I might have gone overboard buying two batteries and would not have done that if I had realized how much this was going to cost in the end (~$3k with 2 batteries). I have not even opened one of the batteries yet. Do I need a special license or certification to ship this battery? It came via UPS ground with hazardous content identifiers.


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## wesleyb82 (Sep 17, 2014)

Finished the wiring last night and setup the charger for the first charge. Still need to work out managing over discharging the pack


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## wesleyb82 (Sep 17, 2014)

The kart is rolling. Ran it around the block a few times. It's geared to do about 30mph and probably gets there in a few seconds. I have sprockets to do ~35mph and ~40mph. Will try to larger gears tomorrow. We ran it for 20-30 min on and off and the motor barely got warm which was one of my main concerns. IR temp gun showed case temp at about 10-20*F above ambient.

The #1 problem is that it will not steer unless you are on the brakes. The 40lb battery behind the rear axle is only making steering more difficult combined with the solid axle. I will have to reconsider a side mounted battery or avoid u-turns and stick to wide turning. You don't see electric karts with batterys in the rear. This is probably why.

The mini-bms and headway charger worked great. Cells started at either 3.84 or 3.85 and at the end of the cycle were 4.14 to 4.19. The charger displayed 15a until very late into charging when shunting started here and there and then the charger ended with a huge ear shattering bang. I thought I had blown a fuse or something had gone wrong but the charger is working again now normally a day later. As per the miniBMS manual shunting allows for .75a draw per cell group but the 15a charger was charging at full 15a at this phase of the cycle. So the charger was supplying 15a/12 or 1.25a per cell group while shunting was only absorbing .75a which I thought was going to be a problem and cause either resistor over temp (80*C) or over voltage state but the miniBMS allowed the charger to continue and the cycle ended with the charger reaching termination voltage of 50.4v (although my meter readings showed less than 4.20 after charge and 8hr rest). After running it for a test of 20-30m I am showing 3.84v or what I believe to be 30% capacity used.

I ran it with a laptop around the block and have the results posted below. I selected battery amperage and output amperage but the data was saved as battery voltage which seems like a typo? Anyway this data claims a near 500a draw with this 300a controller. The battery metal case was a few degrees above ambient at the end of testing.

Regarding under voltage again, I am guessing that once the under voltage setting (42v or ~3.5v per cell group) is reached the controller will shut off. Since I should not be far from the trailer where ever I take it I plan to allow the batteries voltage to rest and rise, power cycle the controller then limp back to the trailer. Is this guess correct? Otherwise I will find myself walking back to fetch the trailer sometime soon when I do run it all the way down


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## wesleyb82 (Sep 17, 2014)

Video from first run, doesn't really show the acceleration except for a moment half way through... but anyway if anyone is interested here is something to check out for now


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## wesleyb82 (Sep 17, 2014)

I ran this kart hard today for about 15 minutes then suddenly the motor sounded differently as if there was a rock lodged inside. Metal shards staying falling out of the motor. It was pretty hot at this point so it may have overheated. Does anyone have an idea what might be happening here?


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## major (Apr 4, 2008)

wesleyb82 said:


> I ran this kart hard today for about 15 minutes then suddenly the motor sounded differently as if there was a rock lodged inside. Metal shards staying falling out of the motor. It was pretty hot at this point so it may have overheated. Does anyone have an idea what might be happening here?


I think so.


major said:


> BTW, your plan to use a brushed PM motor might survive Pb-acid, but with a decent size Lithium battery, will likely result in motor failure.


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## wesleyb82 (Sep 17, 2014)

I ran the motor today after it cooled down and it is working. Don't know if the power is the same or if will soon stop working but I will attempt to open it to inspect it. Anyone have a guess what these shavings are from?

https://www.youtube.com/watch?v=lcMbzAKrlXY


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## major (Apr 4, 2008)

wesleyb82 said:


> I ran the motor today after it cooled down and it is working. Don't know if the power is the same or if will soon stop working but I will attempt to open it to inspect it. Anyone have a guess what these shavings are from?


It's difficult to see the photo evidence. Typical failure is in the connections of coils to commutator, or inside or outside of the rotor disc. Melts solder and sometimes throws off metal clips depending on the construction techniques. Also possible brush rigging melted releasing metal part(s) which were then ground up by spinning rotor. Less likely is a magnet being dislodged from stator.


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