Kid Friendly Lipo Controller Solution

[T-Man]

I am putting together a 14S3P 15Ah Lipo pack for an electric go kart for the kids. So I need to make it as dummy proof as possible. I need a LVC cutoff solution to protect the batteries. The kids will drive it till it stops, so I need that to be at a safe voltage. The motor is a 48V 1000W Unite motor. All the charging will be done through a 25 pin D-sub connector to a 1420i charger, so the pack will be balanced charged every time. That said, can I rely on the controller LVC to protect the batteries?
What controller would you recommend. It would be nice to have a programmable controller, but I'd like to keep the costs down... I've been looking at the Kelly controllers. Is that a good way to go?

Thanks,

Tanner

 

[Ypedal]

No.. do not rely on the controller's LVC ( it only looks at the pack voltage.. not cell voltages )

get either a methods or TPpacks.com lvc cutouff board and hook it into the throttle signal to shut down the power if any cell/group reaches 3.0v

Kids and Lipo.. dont mix well....

 

[Drunkskunk]

This is a good example of why I try not to recommend Lipo to new people. I may have to link back to this thread from time to time.

 

[el_walto]

No the controller LVC will not work safely.

At full charge your pack would be around 58.8V
At Minimum charge your pack should cut out before 42.0V

Imagine if one cell becomes faulty for some reason and drops to 2V after 1 minute of use. The pack voltage would then be at 56.8 and the controller LVC will not trip even though a cell is over discharged. If this situation happened for some reason you'd likely end up with a nice fire.

Yes if the pack stayed perfectly balanced you'd be fine, but not all cells are exactly equal.

 

[Ypedal]

It would still be a good idea to get a controller with a conservative cutoff , 14 cells x 3.4v = 47.5 ish volts would be good to get most of the pack's capacity but not draining it flat ( not a much left from 3.4 to 3.0.. )

 

[Grizzlybear]

"Dad.... DAAAAAD!!! can I have some LIPO for Christmas?" :lol:

 

[vanilla ice]

Whatever you decide to do, make sure the kiddos watch some fire vids and talk to them, so they know what can happen and so they know what to do. And run the charge bags ON the vehicle also. Not just during charge time.

 

[T-Man]

Yes, Yes, I've read all about the dangers of Lipo and am aware of the need to closely monitor the kids. In reality, I didn't really want to admit it, but I will be driving the kart most of the time to take my 3 yr old boy for rides. He asks me every day "go kart daddy, go kart?" I will be doing all the charging as well. I just want to reduce the risk as much as possible for the few times the older kids want to take the kart out for a ride. The battery will also be located in a well shielded area that will protect the riders from a massive flame out.

I looked at the LVC boards and they look like a great solution. Out of curiosity, what did everyone do before methods and tppacks came out with these. Were they all riding on a prayer? Some of these comments will lead one to believe your packs will blow up first ride out...
Looks like methods is working on getting some new stock out and the tppower web site isn't working...

So until I can get some of these LVC boards,
What would be a suitable controller? I imagine the best solution would be a programmable one so that the LVC on the controller could also be set conservatively high. Is there anything out there that offers the same value as the Kelly controllers?

On a side note, I've been using Lipos for years in RC planes. I've heard the horror stories, but in my experience, the Lipos I've used have taken a lot of abuse without giving me any issues.

 

[LI-ghtcycle]

The LVC boards should be all you need and a good position of the batteries so if heaven forbid, murphy takes his toll on the pack, you have a nice metal shield around the packs that would vent things away from harming the rider.

I can't imagine why if this is well supervised that it couldn't be just the same as a kid going around a track with a gas powered kart.

Another trick that many here use is to have an extra high LVC and only charge to 4.1V per cell, that way you have some wiggle room while charging, and keeps you from having to balance as often since as long as the packs aren't far outta whack (more than about 0.1 V of difference) you stay well away from too high, and set the LVC to 3.65 per cell (since you're not commuting, why not? the packs will last longer, and since you have a nice quick charger, shouldn't be much of an issue for ya) and by this I mean something along the lines of the LVC on your controller, and if you have something like a Cycle Analyst, you can have it set for more like a LVC of 3.0 - 3.5 if you want to run things harder when you are riding, and just make sure you re-program the CA for a higher LVC when the kids take a turn.

As you are already experienced with LiPo, I'm sure you already know, but you get what you pay for, cheap LiPo doesn't work as well, doesn't last as long, so get something at least middle road, and high C rate (I like the Turnigy Nano Techs with 25 - 50C because I never use half the C rate, so they aren't really even getting warm in heavy use) and I am going to be doing the same, I currently run 12S, going to try 14S and see if my gearing still agrees with my pedal cadence as well as it does now.

Good luck, and be sure and take pics of the build for us!

I would also recommend you talk to the guys here who sell controllers, Methods, Lyen, and Stevo I think are all here who sell programmable controllers, not familiar with your motor, but I know with the 12 FET that Lyen sells for $140 - $150 shipped with USB cord for program in everything including phase currents and motor timing down to LVC & HVC, I'm not very electronically handy, but it was pretty simple to learn and can handle around 3000 Watts, with a cap of about 60 amps IIRC and around 3000 Watts out-put, so if that is what you are needing, it's a very reasonable price.

He also sells a pretty tough 24 FET like the one that the recent winner PaulD used in the Grange Motorized Bicycle race used at around 50-60V and 100A to hit speeds of just under 50 MPH IIRC, but that one is closer to $350 - $400.

Lots of different controllers available, I have only used Lyen's programmable ones so far, and I am very pleased with them, just ordered 2 more.

 

[wesnewell]

A controller with lvc should work fine as long as the lvc is set high enough. For 14s, for the way you want to use it, I'd set lvc to 52V. That will get you about 80% DOD. If you're trying to stay real cheap. I'd run a cheap non programmable controller using 12s instead of 14s. LVC on most 48V controllers are set to about 42V (for sla). 12s works great with them. It will shut off before reaching 100% dod. This is what i set up for a kid in the hod and he's never gone below a 4% charge.

 

[Ypedal]

Backing things up a bit..

What kind of performance do you want from this machine ?.. if it's just a low and slow toy a brushless chain driven setup will do but if you want competetive performance and grin inducing pull, you may be looking at a brushed setup with a mars / etek / agni type 100's of amps setup... all things to factor in.

when someone posts asking about lipo without telling us they know their stuff, we err on the side of caution obviously, but if you know all about RC and lipo proper use and care it's a different story..

 

[dogman dan]

I posted a few dumb comments yesterday and then deleted. But back to repeat one comment.

Might be a good idea to get a controller with a very conservative lvc, then use the boards as a back up to that. So the controller would stop when the pack was at an average of 3.75v per cell or 3.79v. Get the meat out of the 3.8v section of the discharge, but have the boad stop it sooner if one cell is going south. Then kids can ride it till it cuts out every ride with no problems.

 

[Ypedal]

depeneds on discharge rate and cell choice.. :wink:

 

[kfong]

Try this, http://endless-sphere.com/forums/viewtopic.php?f=31&t=32135

 

[T-Man]

Might be a good idea to get a controller with a very conservative lvc, then use the boards as a back up to that. So the controller would stop when the pack was at an average of 3.75v per cell or 3.79v. Get the meat out of the 3.8v section of the discharge, but have the boad stop it sooner if one cell is going south. Then kids can ride it till it cuts out every ride with no problems.

Thanks, dogman. I think this would be the safest solution as well.

This is in no way going to be a performance kart of any kind. It will be a neighborhood cruiser geared to max out at 12 mph. This should give me enough torque on the low end to do some donuts in the dirt with the boy and keep things slow enough I don't have to worry about the kids seriously injuring themselves or others. I plan to current limit as well to keep things tame. I don't expect this motor to pull more than 20-25 amps continuously.

The kart started out as a 49cc gasser chinese kart. Kind of like this:


There shouldn't be anywhere the kart can't go... :lol: It's got a live axle and full suspension.

I'm using the Turnigy 4S and 2S 5Ah batteries rated at 20C. The motor is a cheap brushed motor from China as well. But it has held up pretty well so far.

I would also recommend you talk to the guys here who sell controllers, Methods, Lyen, and Stevo I think are all here who sell programmable controllers, not familiar with your motor, but I know with the 12 FET that Lyen sells for $140 - $150 shipped with USB cord for program in everything including phase currents and motor timing down to LVC & HVC, I'm not very electronically handy, but it was pretty simple to learn and can handle around 3000 Watts, with a cap of about 60 amps IIRC and around 3000 Watts out-put, so if that is what you are needing, it's a very reasonable price.

He also sells a pretty tough 24 FET like the one that the recent winner PaulD used in the Grange Motorized Bicycle race used at around 50-60V and 100A to hit speeds of just under 50 MPH IIRC, but that one is closer to $350 - $400.

Lots of different controllers available, I have only used Lyen's programmable ones so far, and I am very pleased with them, just ordered 2 more.

Thanks LI-ghtcycle. I will take a look at these.

Any other controller suggestions? It might be nice to get a nicer controller now to allow for future upgrades (i.e. stronger, faster motor).

Thank you for all the suggestions. I think this really can be done right so that the kids stay safe and have fun.

Tanner

 

[bobc]

hobbyking do an 8 cell monitor for $14 which includes an adjustable LVC looking at every cell.
Only problem with this bit of kit is that the alarm plug connection is just awful, and of course you'll have to get 2 and engineer an isolated soloution. Should be do-able though & $14 eac is so cheap.
http://www.hobbyking.com/hobbyking/store/%5F%5F10952%5F%5FCell%5FLog%5F8M%5FCell%5FVoltage%5FMonitor%5F2%5F8S%5FLipo.html

 

[LI-ghtcycle]

Might be a good idea to get a controller with a very conservative lvc, then use the boards as a back up to that. So the controller would stop when the pack was at an average of 3.75v per cell or 3.79v. Get the meat out of the 3.8v section of the discharge, but have the boad stop it sooner if one cell is going south. Then kids can ride it till it cuts out every ride with no problems.

Thanks, dogman. I think this would be the safest solution as well.

This is in no way going to be a performance kart of any kind. It will be a neighborhood cruiser geared to max out at 12 mph. This should give me enough torque on the low end to do some donuts in the dirt with the boy and keep things slow enough I don't have to worry about the kids seriously injuring themselves or others. I plan to current limit as well to keep things tame. I don't expect this motor to pull more than 20-25 amps continuously.

The kart started out as a 49cc gasser chinese kart. Kind of like this:


There shouldn't be anywhere the kart can't go... :lol: It's got a live axle and full suspension.

I'm using the Turnigy 4S and 2S 5Ah batteries rated at 20C. The motor is a cheap brushed motor from China as well. But it has held up pretty well so far.

I would also recommend you talk to the guys here who sell controllers, Methods, Lyen, and Stevo I think are all here who sell programmable controllers, not familiar with your motor, but I know with the 12 FET that Lyen sells for $140 - $150 shipped with USB cord for program in everything including phase currents and motor timing down to LVC & HVC, I'm not very electronically handy, but it was pretty simple to learn and can handle around 3000 Watts, with a cap of about 60 amps IIRC and around 3000 Watts out-put, so if that is what you are needing, it's a very reasonable price.

He also sells a pretty tough 24 FET like the one that the recent winner PaulD used in the Grange Motorized Bicycle race used at around 50-60V and 100A to hit speeds of just under 50 MPH IIRC, but that one is closer to $350 - $400.

Lots of different controllers available, I have only used Lyen's programmable ones so far, and I am very pleased with them, just ordered 2 more.

Thanks LI-ghtcycle. I will take a look at these.

Any other controller suggestions? It might be nice to get a nicer controller now to allow for future upgrades (i.e. stronger, faster motor).

Thank you for all the suggestions. I think this really can be done right so that the kids stay safe and have fun.

Tanner

Well, in that case, I would say you could probably go with the 12 FET, but honestly I am not the expert, send a PM to Lyen or one of the others selling controllers, and they can tell you exactly what you need, just curious, how much does that 4 wheeler weight?

I think we all envisioned a racing cart on a track .. maybe that's because we are used to seeing really fast builds here hehe .

Another idea is if you had say, the 12 FET, and have it programmed for pretty brisk performance, in "Adult" mode, say around 30 - 40 Amps so YOU can have some fun when you're wanting to go around 20 - 30 MPH, and then just use the Cycle Analyst and change the speed limiter and amps limit on the CA since it's really easy to do in just minutes.

But best of all, you can even limit the speed the motor will provide too! In fact, now that I think about it, you probably can just get a pretty standard controller that has around 20-30 amps that is compatible with the CA, and just use the top speed and amp limits for the kids, not to mention the CA has LVC too, and would give you a great "gas gauge" to let you know not only how many Amp Hours you're using, but Wh/Mile, and if you have your motor set up directly (no freewheel) you can even use regen braking.

http://www.ebikes.ca/store/store_accessories.php

If you bought say the CA-LDPS (Large Screen Direct Plug-in Cycle Analyst with Speedometer Cable) and a compatible controller that would have the direct plug-in so all you have is two small cords instead of having a standard watt meter that has main power going through, and the CA keeps track of all this info even when you power off, and even gives you how many charge cycles for the battery. 8)

 

[dogman dan]

Once he goes brushless on the motor, a CA compatible controller and CA would allow some nice limiting options to be set.

Resetable to better options when you are driving.

 

[ohzee]

reading this thread I am tempted to do something similar. I am curious could someone link a motor
that would work for a go cart like this ? Would it be something from a decent scooter or rc type ?

thanks for the post I find it pretty interesting. I have access to a similar go cart that does not run if
i wanted it.

 

[LI-ghtcycle]

Oh good point D-man, I forgot what motor he was using. So the Unite motor is brushed? Bummer, I can recommend a good motor, should have plenty of power! (not sure you want the kids driving it though! )

But seriously, as long as the "kart" (looks more like a buggy to me :wink: ) is less than 200 lbs? You might get along find with one of these:

http://www.goldenmotor.com/

(The one on the far right, 800W, designed for the large heavy Pedicabs used as trucks more or less in China) even comes with a 420 Motorcycle chain sprocket! Probably wouldn't be hard to power your current 4 wheeler if it uses chain drive. 8)

These motors are used with a Pedicab that would weigh around 600lbs with the rider and two passengers, albeit they probably go only 5 - 10 MPH.

The two that I serviced recently had to weigh AT LEAST 150 - 200lbs all by themselves! I'm sure this motor wouldn't have trouble moving around your kart. 8)

 

[LI-ghtcycle]

reading this thread I am tempted to do something similar. I am curious could someone link a motor
that would work for a go card like this ? Would it be something from a decent scooter or rc type ?

thanks for the post I find it pretty interesting. I have access to a similar go cart that does not run if
i wanted it.

Wow, that was funny, I was just finishing my post when you asked that, good timing!

 

[ohzee]

haha yea that is thanks - my ninja edit to fix go cart (damn fingers) was a little slow.

Still great info. I love lipo having these batteries around I pretty much have my own fuel
cell to do whatever I want. Cant wait until I have some spare money to get me some nano's.

 

[Pure]

The only thing I have to add to what everone else has said is where you say this.

This is in no way going to be a performance kart of any kind. It will be a neighborhood cruiser geared to max out at 12 mph. This should give me enough torque on the low end to do some donuts in the dirt with the boy and keep things slow enough I don't have to worry about the kids seriously injuring themselves or others. I plan to current limit as well to keep things tame. I don't expect this motor to pull more than 20-25 amps continuously.

Looking at that cart, it's not very light to begin with, then with it being a 2 seater, I would def look into a few more amps. 30-40 for one adult or 2 kids should be about right and still "safe".

 

[T-Man]

hobbyking do an 8 cell monitor for $14 which includes an adjustable LVC looking at every cell.

I've looked at this, but as far as I can tell it only alarms at low voltage. It doesn't disable the controller or throttle. But, you're right it is an attactive solution at $14. If it was just me, it's the way I would go.

The kart weighs maybe 130lbs without batteries. I've never weighed it, but I can easily pick up and move the front or back end around, batteries included...

I've run several sets of SLA through the kart so far (which is why I'm switching to Lipo), and at 48V the motor gets pretty warm, especially during our 110F summers here in AZ. I've never bothered to measure Amps, but I am wary of pushing too many. Especially since it is a cheap China motor. The kart is geared so low that it reaches top speed whithin several seconds anyway.

Ohzee, I picked up the Unite motor because it was only like $90. And for kid application, the power is sufficient. I stepped outside one day to see 4 kids riding down the street on the kart with one kid hanging off the back being dragged. The kart climbs the dirt hills in the retention basin easily. Lots of low end torque. Not much speed...

One day I will step up to brushless and go faster...

I get to pick up my 1420i charger today!
Now all I lack is the controller and a LVC board. I hope to have some time this weekend to look into the cycle Analyst, though initially it looks to be more elegant of a solution than I need.
So far, I'm liking Methods boards.

What is the best way to get more info on the controllers being offered by Methods, Lyen, and Stevo? I've tried searching the forum, but it is time consuming to comb through all the posts.

Thanks!

 

[T-Man]

After a lot of searching (probably in all the wrong places) I ordered a KDS48100 from Kelly today. I couldn't really find anything negative about the Kelly controllers, and they seemed to offer a lot of value for your money. Their customer support was good though a little on the slow side when I asked a few questions.

I have the 1420i in my possessition and the charge cable all put together as well. I think it turned out pretty well. I'll have to try to post some picts. I found a great source for hyperion charge adapters, loose connectors, pigtails, etc. here: http://www.allerc.com. They are based out of AZ, just down the road a ways from me. I went to my LHS the other day, and the owner told me he has a local hyperion distributor that he can get stuff from as well (I suspect it may be the same place). I had him order me the charger and loose EOS balance connectors. He is able to get stuff in next day. Very convenient.

I've also been able to do a little motor mount work on the kart. I'm not sure if I want to post picts of that. Not very pretty looking. I definitely need a lot more practice with a welder. :? But it is functional and makes it very easy to adjust chain tension. I know my boy won't care as long as it goes.

I think with the long weekend coming up, I should be able to get things finished up, assuming the controller gets delivered before then.

T-Man