Spec 1 power specs?

Azimov · #1 06-06-2003, 10:44 PM

Anyone out there have the voltage and current ratings for the Spec 1? I know it has three batteries, so I'm guessing around 3.6VDC, but I'm unsure of the current. Has anyone done any testing of the Spec 1's stock motor stats for open and stalled current requirements?

Azimov · #2 06-09-2003, 06:28 PM

OK, you're forcin me to post in another forum. Don't make me do it.....

tinyrc · #3 06-14-2003, 01:57 AM

Don't do it! Voltage is 3.6v, current I'm not sure - why Spec 1 specifically?

Azimov · #4 06-14-2003, 02:13 AM

Quote:

why Spec 1 specifically?

Well, solarizing a couple of Zips has made me want to make a solarized car with proportional speed and steering. The Epoch leapt to mind. I specified a spec 1 as I figured I may be able to get one cheaply for the conversion. I would prefer a spec 2, but was hoping for a used one or some other bargain.
I kinda figured that was the voltage rating. Tell me this. How many batteries are in the thing and what are their current capacities. I can figure from there.
(edit) OK, I just re-read my own post and realized I already knew there are three batteries. But I still need the mA rating on them.

tinyrc · #5 06-14-2003, 02:27 AM

Stock pack is 3 x 120mAh 1/3 AAAs. Great project idea!

Azimov · #6 06-14-2003, 02:48 AM

Thanks Tiny! So, we're talkin 3.6VDC @ 120mA. Great! That means these solar cells will work nicely. Now to find the victim.

tinyrc · #7 06-14-2003, 10:26 AM

Hold on a sec; that 120mAh would mean 120mA draw if the car lasted for an hour on a single charge - since it lasts only maybe ten minutes, the actual draw must be something like 6 times 120 = 720mA. Right?

Azimov · #8 06-14-2003, 02:24 PM

Quote:

120mA draw if the car lasted for an hour on a single charge - since it lasts only maybe ten minutes, the actual draw must be something like 6 times 120 = 720mA. Right?

No, not really. The battery is most likely charged like a bit and is no where near full. A bit charges for 45 sec. and runs for about 4-5 minutes. The car contains a 1.2VDC @ 50mA battery. Using your math, it would be using 700mA to run for that 4-5 minutes. If you peak charge that bit, you can get half an hour to 45 minutes of run time out of it. Now, it uses only 100-120mA of current draw versus runtime. That's why I asked for motor current draw open and stalled. That's the numbers that tell me what I need to supply the car continuously to operate normally with a solar cell. Namuna supplied some great charts on Zip and Bit motors that helped tremendously when I was solarizing Zips. See, you're thinking capacity, and I'm talkin consumption. Once solarized the car no longer has any storage capacity other than a small buffer cap. I need to factor actual power consumption of the car as it is driven. I supply a tad more than this through a solar array and whammo, solar Epoch!

tinyrc · #9 06-14-2003, 03:13 PM

The ten minutes I quoted was based on actual experience, and I only ever peak it, I don't use the included charger. So - surely if it lasts 10 minutes, and has 120mAh, the average consumption over that period is 0.7A? This makes sense compared to Mini-Z statistics, which I'm extremely familiar with, and where for example, a stock motor @ ~0.7A draw running 4 700mAh NiMHs will run for about an hour. And a powerful motor running over 2A will last for 15 minutes or so. Right?

Azimov · #10 06-14-2003, 03:43 PM

Yep, that's right. But, the key is in your last statement.

Quote:

a stock motor @ ~0.7A draw running 4 700mAh NiMHs will run for about an hour. And a powerful motor running over 2A will last for 15 minutes or so. Right?

The power needs of the motors is the factor. The motor isn't pulling that 700mA cause if it did, it would deplete the batteries almost immediately. It runs for an hour or so. That means it's sipping from the batteries until they are depleted. The motor pulls most of it's current needs at stalled conditions. Once the car is moving, the power requirements drop considerably more. This stall current is the power needed to run the car continuously from solar cells. This is another reason battery capacity isn't really related to solar cell output. What I need to factor this is the stalled current of the drive and steering motors combined. This number is what is needed to run the car continuously from solar cells. Capacity and runtime become irrelivant at this point.

tinyrc · #11 06-14-2003, 04:21 PM

Quote:

Originally posted by Azimov
Yep, that's right. But, the key is in your last statement.

The power needs of the motors is the factor. The motor isn't pulling that 700mA cause if it did, it would deplete the batteries almost immediately. It runs for an hour or so.

No, I'm still fairly sure my approximations are close; if it pulls 700mA, then that means it could drive for an hour at that load it if had a 700mAh pack. But, it only has a 120mAh pack, which explains why it only runs for 1/6th of an hour, 10 minutes. Yes, it takes more to move from a standstill, and less to coast, but that's why I said 0.7A average. Like I said, I've done extensive, accurate testing on Mini-Z motors, and they pull 0.7-2A, so it's not unreasonable that the Epoch pulls around 0.7A on average. What kind of output can you get from the solar cells?

Namuna · #12 06-14-2003, 05:47 PM

I haven't done the tests (yet), but I recall hearing that the Epoch Spec-2 Motor pulls something like ~350ma (no load).

Have you considered the Yokomo Puchi Maru? It's 1/60th scale, which puts it just slightly bigger than the ZipZaps and it's FULLY proportional. A little hunting around can fetch it for ~$60 so it's cheaper than the Epoch as well.

It's powered by dual NiMH batteries, 2.4v.

Azimov · #13 06-14-2003, 08:00 PM

Quote:

What kind of output can you get from the solar cells?

Not that much for sure. Unless I make a more complex and larger array. I don't doubt your figures and can't really debate the matter as I have never owned an Epoch to do any real testing.

Quote:

I recall hearing that the Epoch Spec-2 Motor pulls something like ~350ma (no load).

That could be a problem. That would put the stall current requirements much higher. Probably around Tiny's estimate. I can get solar cells that output 400mA, but this still may not be enough to do the trick. An array that mixes parallel and series connections would work, but the array would get much larger. Twice as large actually. Still, switching out the motor for a much more efficient one may work with a smaller array.

Quote:

Have you considered the Yokomo Puchi Maru?

Yes I have and even more so now. From what you've said, it may be a better candidate. I'm trying to keep the solar array as small as possible while delivering the most bang.