# Newbie in desperate need of tech help...



## racingjason (Dec 6, 2008)

I have started gathering parts for my first conversion which is basically a ride on toy for my 5 year old. Since I am new to electric vehicles but have built many drag race cars over the years I have the mechanical side covered but am SORELY lacking in EV-knowledge. 

Here is my basic plan:

500w 36v motor from monsterscooterparts with a 48v controller. 48v battery pack probably SLA but may go NiMH if a friend comes through for me. 

Potential SLA battery specs:

​Nominal Voltage...........................................................12 V​ 
20 hours (0,5 A til 10,50 V) ..........................................10 Ah
10 hours(1 A til 10,50 V) ..............................................10 Ah
5 hours (1,7 A til 10,20 V) ............................................8,5 Ah
1 C (10 A til 9,60 V) ....................................................4,5 Ah​3 C (30 A til 9,60 V) ....................................................3,5 Ah

10000mAh

Total SLA weight: 30lbs

Potential NiMH battery specs:

9.6v 3800mAh R/C packs in series sets of 5 to reach 48v then 3 parallel sets to get to 11400mAh

Total NiMH weight: 19lbs

My main questions are as follows:

What kind of power can I expect from a 36v 500w motor in a sub-70lb EV (minus rider, 110 w/rider) assuming I get the gearing fairly close? Not looking for a top speed machine mainly looking for hill/terrain climbing power with a top end of about 5-8mph.

If 500w is not enough should I step right up to a 36v 1000w motor and adjust my battery set-up accordingly? I am concerned because of the amount of energy it will take to turn the drive wheels. (they have not arrived yet for testing)

If I go with the NiMH how should I charge them, individually? My only experience with NiMH is in a Traxxas Stampede R/C car and the Vision charger for that is a POS. Charger recomendations? Any suggestions on wiring all 15 packs? Do I need anything "special" to use the NiMH vs SLA?

I figured a 25-50 min riding time with the 1000w motor and NiMH setup depending on use... is this in the ballpark? If not what should I expect?

If this was your project what would you do? Go cheap and see how it goes, or go big right out of the gate not knowing if this will even work?

My apologies for the plethora of questions and for any incorrect assumptions. Thanks in advance for the help, been lurking and I see you all have me beat in the EV department. 

Jason


----------



## racingjason (Dec 6, 2008)

As an added bonus I posted it in the wrong sub-forum. Off to a great start here.


----------



## zig06 (Aug 3, 2008)

With EV limited knowledge and a limited budget all you can do is go for it and see what you end up with. Because it's your first EV, you will find ways of improving it after you finally get it up and running. 

So just take your best shot and put it together the best way that you know how. Post pictures when you get stuck but keep pushing on and eventually you will have it.

I can say that a 500w (2/3 hp) motor will not be much power, expect to have it geared to the moon and even then it will not be very fast. In most cases you want to install the most power that you can fit into a project like this.

Switching over to NiMh batteries will lower your Hp needs, but go bigger if you can. The 1000w motor sounds better. Run time is very dependent on how hard a EV is used.


----------



## TX_Dj (Jul 25, 2008)

EV Bikes is probably a good place to have this posted. You said "ride on toy" but the parts you're talking about using are intended for scooters and bicycles, and though this section is for "everything on 2 wheels", it's still probably the best place to get in touch with people who have experience with the exact types of parts you'll be using. Folks who aren't interested in "toys" (and some people do see EV Motorcycles as toys, even) won't even bother to come in here usually... so no worries about that.

Take a moment to look for my topic Re-conversion of a Scooter.

This project used a lot of the same types of parts you're talking about. I used a Currie 36v 1000w motor salvaged from a Currie iZip 1000, and its matching controller (36v 30A peak).

The scooter weighs in about 65-70 lbs as configured (lots of lead, and that motor is HEAVY), and with my ~180 lbs on it, it will (eventually) get up to about 20-23 mph with a 3.66:1 ratio on a 9" tall tire. With a 4.66:1 ratio on the same tire, it tops out around 15 mph, but will get there in respectable time and little to no slow downs going up a hill.

I'd imagine with a comparably sized tire with a ratio that would yield a 5-8 mph top speed, with my motor, it would climb up a cliff at full speed.  500w not as much.

I'll mention this, since you say you have little EV experience - volts are what drive RPM, and amps are what drive torque. At 36v, that motor will be draw about 14 amps at peak. At 48v, it will turn a little faster (which could be too fast, depending on the motor) but will only draw about 11 amps at peak.

Depending on the motor type, it may be able to draw more amps, but that's dependent on its type, configuration, construction, and the load placed on it.

As for your batteries- SLA batteries are far more tolerant of minor mismatches when placed in parallel without protection. NiMH are far less tolerant of any mismatch in parallel. Either way, if you're going to parallel any battery type in this project, invest in some fast switching or schottky diodes to keep the packs isolated from each other. I have a dual-diode (fast switching) in my scooter, and I credit it with winning the race at last month's Scooter Challenge at the NTEAA meeting.

The diode lets all the batteries in parallel share the amp load (and increase their apparent capacity by drawing them at a lesser rate) without a stronger pack trying to charge a weaker pack when that weaker pack sags to a lower voltage than the others.

In any chemistry, when this happens (uncontrolled "charging" of the weaker pack) a lot of heat can be generated, a lot of power can be shunted to that pack instead of to the load, and you can either reduce your potential capacity during that discharge cycle or cause a runaway thermal condition that could result in explosion/fire of the battery.


----------



## racingjason (Dec 6, 2008)

Thanks for the replies, I appreciate the help! TX_DJ, your scooter project is what brought me to the forum in the first place. It's actually the reason I registered here, and the motor you have used is indeed the same motor I am considering for this.

So since it seems you both agree to can the 500w motor I'll get a 1000w currie on order ASAP.  I did want to run 48 volts but if 36v will work well with that motor and keep the RPM down I can go that route. Is there any controllers you can recommend (or better yet NOT recommend)?

I can get a deal on the NiMH R/C packs (close to SLA prices) so I am leaning that way. Is there a website where I can buy those diodes? And what about charging? Should I buy a bunch of chargers and charge each pack separate? 

My son saw some sketches I was working on for this and nearly peed himself, I hope I can pull this off or he'll think I did a bait and switch on him!


----------



## TX_Dj (Jul 25, 2008)

racingjason said:


> Thanks for the replies, I appreciate the help! TX_DJ, your scooter project is what brought me to the forum in the first place. It's actually the reason I registered here, and the motor you have used is indeed the same motor I am considering for this.


Thanks for this, now my head is so large I can't fit thru the door. LOL j/k



> So since it seems you both agree to can the 500w motor I'll get a 1000w currie on order ASAP.  I did want to run 48 volts but if 36v will work well with that motor and keep the RPM down I can go that route. Is there any controllers you can recommend (or better yet NOT recommend)?


The motor will take 48v, but I'm not sure if it will take the extra RPM because I've not tested it. Typically, motor designers under-rate the RPM on their motors just to "be safe" because surely there can be variances from motor to motor which could possibly allow one to spin much faster and another to not spin any faster than the rated RPM without damage. It's up to you to determine what you wish to risk.

I'm using the matched controller for that motor, 36v, 30A. I'd like more power, but I'm not sure I can fit a more powerful controller.




> I can get a deal on the NiMH R/C packs (close to SLA prices) so I am leaning that way. Is there a website where I can buy those diodes? And what about charging? Should I buy a bunch of chargers and charge each pack separate?


With NiMH I would think charging the packs separately would be the best bet.

You can buy diodes sized specific to your needs from just about any electronics supplier. I got mine from ebay, after deciding on a specific model.

I can't charge both from one controller because that would circumvent the point of the diode by permitting charge current to go to both packs (i.e. 1 can discharge into the other)



> My son saw some sketches I was working on for this and nearly peed himself, I hope I can pull this off or he'll think I did a bait and switch on him!


HAH! Good luck!


----------

