Battery choice for go-kart build

[tome]

I am working on a go-kart, mainly for a pre-teen boy, and need to figure out what batteries to use. The motor is a Mars 10kW BLDC and have a Kelly KDL series (300A) controller. I want to run the system at 48V. Top speed isn't critical, though with the current gearing, wheels, etc, calculations show top speed would be about 35-38mph. I will dial this down in the controller for main driver, but may turn it up for others. Anyway, I need to figure out what batteries to use in order to figure out how big the battery trays I need to add to the sides will be. I am leaning towards initially scrounging (or buying new) AGMs or similar but not really sure which ones to look for. I want a reasonable amount of run time, say 30-60 min, but obviously don't want to spend a ridiculous sum or add more weight than absolutely necessary (I realize it will be heavy in any case). Any ideas on what I should look for that is reasonable in price and performance for this application?

Assuming the kart is fun and gets used I will probably build a Lithium Phosphate pack of some sort in the future - unless some amazing pack comes available to buy in the next year or so at a reasonable price.

Thanks for any suggestions.

 

[parajared]

Go-Karts can be pretty fiddly when it comes to weight, assuming you want them to race nicely. You want your kart to be as light as possible. Your lightest/cheapest option is li-co. Most of us buy our li-co from a website called hobbyking.com. Li-co is pretty nasty stuff and has a bad habbit of bursting into flames when punctured. It will burn down your house if you don't charge it properly. None-the-less it's the battery of choice for light weight, top performance, and price. Li-co completely dominates the aircraft helicopter and car world the as source of power for anything remote controlled. After playing with Lifepo4 I think Li-co is the way to go.

Lifepo4 is the stuff used by NASA, and people building vehicles so large that that it just doesn't make sense to have a bazillion little remote controlled car batteries. Lifepo4 can still catch fire, but isn't nearly as volitile as li-co. It runs like crap when you get it cold, it's expensive, it feels like a ton of bricks, and has a really screwy voltage curve making it hard to tell when it's fully charged or depleted. When you pull amperage from Lifepo4 the voltage "sags" making your top speed and throttle feel inconsistant. More and more people are making the switch to Lifepo4 due to how vile and hateful Li-co can be. You can get pretty good prices on Lifepo4 from evassemble.com.

I haven't personally worked with other chemistries than these two.

 

[tome]

You can get pretty good prices on Lifepo4 from evassemble.com.

Thanks for the info. Their 48V 20Ah pack looks quite interesting. I hadn't seen these before. From what I have read here on these they seem to be decent...
-Tom

 

[parajared]

Back in April I decided to give Headway Lifepo4 a try. The BMS I bought from Headway Headquarters after about 10 cycles started running into a glitch where the bms would trip whenever >10 amps was drawn from the pack. HH and I had a few e-mails about this of which the conclusion was that the BMS was damaged because the cells were not completely balanced before connecting the BMS. I didn't feel this was fair because the cells were all balanced within 1/10th of a volt of one another, but I didn't say anything in the interest of keeping things amiable.

I decided to "go naked" and top balance down the balance wires using a rc charger instead. This worked to balance cells however, the cells were only charging to around 80% instead of fully charged. I sent an e-mail on 6/19/13 in regards to this and have not recieved a response. I thought this was fault of the charger and bought another charger from evassemble which also charged only to 80%. I concluded that it was not the charger's fault, but if fact the cells. Further testing revealed that all of the cells are having a problem where they heat up rather than charging properly. I sent a second e-mail on 7/12/13 and called and left a message a week later, both are still unanswered. I have continued to use the pack and now I have several cells showing 0 voltage that refuse to take a charge.

 

[major]

The EnerDel 2P12S modules work out well on go karts. Gives you 44V at 35Ah. I've used 1, 2 or 3 modules in parallel. Also know of guys running 2 in series.

 

[tome]

The EnerDel 2P12S modules work out well on go karts. Gives you 44V at 35Ah. I've used 1, 2 or 3 modules in parallel. Also know of guys running 2 in series.

Is this chemistry less or more volatile than LifePO if mistreated?
Tom

 

[major]

The EnerDel 2P12S modules work out well on go karts. Gives you 44V at 35Ah. I've used 1, 2 or 3 modules in parallel. Also know of guys running 2 in series.

Is this chemistry less or more volatile than LifePO if mistreated?
Tom

It is Li-NCM or sometimes called just NCM or NMC. It is typically put in the same safety category as LiFePO4. See: http://batteryuniversity.com/learn/article/the_high_power_lithium_ion

 

[Arlo1]

As long as you don't over charge or discharge and don't puncture them you should be fine... So make a proper enclosure and use a good BMS.

Luke (liveforphysics) on the forums here posted a video a while back showing one NMC Cell WAY over charged and hitting it with a hammer and nothing happened.

I'm trying to find the video.

 

[tome]

It is Li-NCM or sometimes called just NCM or NMC. It is typically put in the same safety category as LiFePO4. See: http://batteryuniversity.com/learn/article/the_high_power_lithium_ion

A few other questions on the Enerdel modules....Which would be more appropriate for my application:
http://evolveelectrics.com/Enerdel_MP310-049_Moxie.html
or
http://evolveelectrics.com/Enerdel_ME330-049_Moxie.html

I assume I need a BMS with 1 or two packs, yes? If so, which one would you recommend. If I use two of the modules paralleled together, what would I use to charge them? Would I disconnect the parallel packs and charge individually or can they be charged as one?

Thanks,
Tom

 

[major]

The MP modules are for power. ME for energy. Typically ME cost less and have a extra Ah per cell. The power cells have a bit lower resistance. The 049 in the part number is the charged voltage of the module. All these are 2P12S. The ME350 is the grade A 35Ah module using 17.5Ah cells. ME340 is grade B and ME330 is grade C with 16.5Ah cells. MP310 is grade B power cells at 15.5Ah. All are top quality brand new cells and modules. From evolve, for the money, ME330-049 is the way to go.

For your application I think the energy cells (MExxx-049) are suitable. It is what we ran in our karts. You can search here and find numerous tests I have run and posted showing high discharge from these modules.

The BMS and charging questions are up to you. In our karts we would monitor and balance semi manually. I have an klunker kart where I use a single module and a 275A controller. The good race karts ran 2 or 3 modules in parallel. For the competition we were limited to just over 300A. But on free track days we jack it up to 550A.

We used DeltaQ 17A chargers single modules and parallel modules both. I've also used the Thunder 1220 charger on a single module. It takes a while.

 

[tome]

The BMS and charging questions are up to you. In our karts we would monitor and balance semi manually.

Thanks for the info. So are you saying that you didn't have a BMS but just watched your draw and balanced on a hobby-style charger, or something more sophisticated than that?
Tom

 

[major]

The BMS and charging questions are up to you. In our karts we would monitor and balance semi manually.

Thanks for the info. So are you saying that you didn't have a BMS but just watched your draw and balanced on a hobby-style charger, or something more sophisticated than that?
Tom

On the competition ekarts we used a system comprised of monitors (CellLog8s), alarms for LVC, charger safety disconnect for HVC and manual balance/equalization when needed, which was infrequent. I drive a Think EV which has 16 ME350-049 for 24 kWh everyday. Its has a full blown BMS by EnerDel. I have about 500 cycles on it. I have also crewed for Lightning and helped build those bikes and other EV racers. There we always used a BMS which balanced at the top of charge.

I also use the ME350-049 modules on other projects where I monitor them without automatic BMS. These cells stay very closely balanced. But I am not going to tell you not use a BMS. That is your decision.

So far I have been disappointed with hobby style balance/chargers on these large Ah batteries. They, to me anyway, appear low quality and took forever to make a 50mV difference. I just ordered a BC-168 to see how it works. The modules are supplied with a flexible circuit connector installed which has a path to each cell pair for BMS connect good for maybe 4 Amps. It also includes a thermistor for each cell pair.

These EnerDel cells and module systems are high quality made-in-America to automotive standards products. You can see the high price on the ME350-049 and MP320-049 modules on the evolve website. Over the past year EnerDel has been reorganizing and changing ownership and directing focus from automotive to other markets like GES (grid energy storage). They cleaned house so-to-speak and made available product to some dealers and friends like me at a steal. I doubt that EnerDel sees the hobbyist as a viable market so I suspect after these "surplus" products are gone, prices will resume the high OEM levels of a year ago.

 

[tome]

The BMS and charging questions are up to you. In our karts we would monitor and balance semi manually.

Thanks for the info. So are you saying that you didn't have a BMS but just watched your draw and balanced on a hobby-style charger, or something more sophisticated than that?
Tom

On the competition ekarts we used a system comprised of monitors (CellLog8s), alarms for LVC, charger safety disconnect for HVC and manual balance/equalization when needed, which was infrequent. I drive a Think EV which has 16 ME350-049 for 24 kWh everyday. Its has a full blown BMS by EnerDel. I have about 500 cycles on it. I have also crewed for Lightning and helped build those bikes and other EV racers. There we always used a BMS which balanced at the top of charge.

I also use the ME350-049 modules on other projects where I monitor them without automatic BMS. These cells stay very closely balanced. But I am not going to tell you not use a BMS. That is your decision.

So far I have been disappointed with hobby style balance/chargers on these large Ah batteries. They, to me anyway, appear low quality and took forever to make a 50mV difference. I just ordered a BC-168 to see how it works. The modules are supplied with a flexible circuit connector installed which has a path to each cell pair for BMS connect good for maybe 4 Amps. It also includes a thermistor for each cell pair.

These EnerDel cells and module systems are high quality made-in-America to automotive standards products. You can see the high price on the ME350-049 and MP320-049 modules on the evolve website. Over the past year EnerDel has been reorganizing and changing ownership and directing focus from automotive to other markets like GES (grid energy storage). They cleaned house so-to-speak and made available product to some dealers and friends like me at a steal. I doubt that EnerDel sees the hobbyist as a viable market so I suspect after these "surplus" products are gone, prices will resume the high OEM levels of a year ago.

Again thanks for the info. Is there a BMS that is reasonably priced that you would recommend?
Tom

 

[major]

I am not in a position (meaning I know I don't know enough about the subject) to make a BMS recommendation. However I do suggest you look over the information Davide has accumulated on his site. http://liionbms.com/php/bms-selector.php The BMS systems for the larger batteries seem to be different than those I see used for ebikes and portable electronics.

 

[tome]

So far I have been disappointed with hobby style balance/chargers on these large Ah batteries. They, to me anyway, appear low quality and took forever to make a 50mV difference. I just ordered a BC-168 to see how it works. The modules are supplied with a flexible circuit connector installed which has a path to each cell pair for BMS connect good for maybe 4 Amps. It also includes a thermistor for each cell pair.

So, if you are willing to charge at a slower rate you can just use a charger or chargers on each cell and charge through the balance leads, rather than charge the whole pack? If you had 2 BC-168s, you could connect up all 12 cells and charge that way safely? How long would a full charge take doing that do you think?
Tom

 

[major]

So far I have been disappointed with hobby style balance/chargers on these large Ah batteries. They, to me anyway, appear low quality and took forever to make a 50mV difference. I just ordered a BC-168 to see how it works. The modules are supplied with a flexible circuit connector installed which has a path to each cell pair for BMS connect good for maybe 4 Amps. It also includes a thermistor for each cell pair.

So, if you are willing to charge at a slower rate you can just use a charger or chargers on each cell and charge through the balance leads, rather than charge the whole pack? If you had 2 BC-168s, you could connect up all 12 cells and charge that way safely? How long would a full charge take doing that do you think?
Tom

I should know in a few weeks, maybe sooner. I make an adapter to go from the flex BMS connector which comes with the ME350-049 module to mate to the JST connectors using #22 wire. So using those to charge with BC-168 which charges each cell independently thru the balance leads, I suspect I will have to limit to about 4 Amps per cell pair. I will monitor the heat in the flex connector on the modules as I do not know its rating and they are smallish circuit board type traces. If I charge a 2P12S module at at 4 Amps per channel, it takes 8.75 hours for a complete 100% SOC. The BC-168 has a 8 Amp per channel limit and if I am able to use all of that, I could charge in 35Ah/8A = 4.375h. The BC-168 is 6 channel, so the 12S battery requires two of them, or one to be used on half the battery sequentially requiring twice the time.

 

[Arlo1]

The BC168 is not isolated you can not use two to charged at one time unless you use 2 separate 12v power supplies to power 2 of the BC168 chargers.
Its talked about in this thread. http://endless-sphere.com/forums/viewtopic.php?f=31&t=41107&hilit=charger&start=50

 

[major]

The BC168 is not isolated you can not use two to charged at one time unless you use 2 separate 12v power supplies to power 2 of the BC168 chargers.
Its talked about in this thread. http://endless-sphere.com/forums/viewtopic.php?f=31&t=41107&hilit=charger&start=50

Yeah, I know, but thanks for pointing that out. I just ordered one BC-168 to limit my "risk" and see how it works. Since I have a nice 1000W power supply I really wanted to be able to run a pair of the BC168s from it together to make life simple. But if I like the quality and function of the BC168, I'll order a 2nd one and figure out 2 isolated supplies for them.

 

[Arlo1]

I have a BC168 and I love it! I also have 31 20 amp DC-DC isolated supplies I plan to make a cell level charger with. All in time. Charging at the cell level is the way to go.

 

[major]

I also have 31 20 amp DC-DC isolated supplies I plan to make a cell level charger with. All in time. Charging at the cell level is the way to go.

It has pros and cons. Getting 20 Amps to each cell in isolation might be a bit harry; lots of big wire. And you need to make sure you haven't had one of your single cell chargers fault out before you go driving off. But I used it of sorts on Pb-Acid at the battery level (12V), called modular charging, for 48V vehicles. It was nice because I didn't have to worry about uneven discharge and could draw 12V accessory from one of the 4 series batteries. Also, the batteries or cells don't have to be perfectly matched.

 

[parajared]

Headway Headquarters read my ES post and now we are working to resolve the Lifepo4 issue.

 

[JimmieD]

I've contacted parajared with concerns to his experience and issues and we are working together to come to a resolution.

 

[dogman dan]

If the dispute is not resolved, we can restore this thread to it's original form. For now, only the description of the problem parajed has been kept.