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Segway General Discussion General discussion related to any model of Segways, miniPROs, or Ninebots. Please do not post non-Segway technology posts here; use the technology forum instead.

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Old 01-13-2011, 06:58 PM   #21
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How do you intend to integrate 3.7V nominal cells into the BMS? The BMS is setup for a 23S configuration on a 3.2V nominal cell. If you change to a 19S config with 3.7V nominal cell there are many hurdles to overcome just to get the Segway to communicate with the battery and turn on. PM me if you want a second opinion on concepts. I'll help out if I can.
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Old 01-13-2011, 11:23 PM   #22
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Thanks for the kind offers, L3Research and Jason.

I think you might be giving me too much credit here -- I'm not messing with the BMS, charger, or anything complex.

I'm just substituting 9S LiPo (33.3v nominal) for the 30S NiMH (36v). All the circuitry, and as much of the case as I can retain, stay exactly the same.

The 9S LiPo will get down to 28v safely, 27 is probably okay if they're balanced.
So the question is, how does the Segway allow the NiMH to get under 1v per cell? 0.9v?

The other thing to watch out for is starting with fully charged LiPo and then going on a long descent.. the Seg would probably overcharge them with regen power. Who knows; I'm not going to try it.
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Old 01-14-2011, 11:54 AM   #23
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I'm aware of what you did and appreciate the simple yet effective approach. Certainly it worked and there are limitations on how much you get out of it due to the lower nominal voltage. I was actually referring to L3Research when he said about a 19 cell configuration for the lithium ion packs. It's a totally different animal than the NiMH and cannot be fooled so easily.
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Old 02-26-2011, 11:33 PM   #24
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I made another one, and I like this one best:

I left the middle strip 'mohawk' of plastic intact this time, to retain the battery connector and add some structural rigidity.

Now I'm all matched batteries (twelve 3S batteries), XT60 connectors, and cleaner wiring.

I also got a chance to run the Segway under more conditions with just LiPo power. First, the full performance envelope is available. With my resuscitated NiMH batteries, they would sag under load and get the straight-face slowdown.

I also added some battery monitoring of my own to track performance in motion.

I rode the Segway with a young passenger to bring it to 200lbs load, up and down hills at full speed and around the block. I measured a peak draw from each battery of 129 Watts. That works out to 11.4 Amps at peak load.

I made a second ride with 170lbs load and worked it as hard as I could. Rapid starts, rapid stops, full-speed turns, inclines, etc. The highest I could hit was 192 Watts, 17.5 Amps.

Overall, this puts the whole battery array at 2300 Watts peak.

As most of you predicted, battery cutoff became an issue. The Segway went to blinking-red when the packs reached 11.0 Volts. At this point, I had used only 0.58 Ah out of 2.2 Ah of capacity, so that's way too early.

None of the 3S batteries dipped below 10.97 volts at any time. (They're rated for 45A or so, so this is a cakewalk). Temperatures stayed slightly above ambient.

So what does all this data show? I believe the batteries are well-matched to this application, operating well within both average and peak load demands.
However, 11v per array is clearly the "zero bars" cutoff for the NiMH Battery monitor, so I'm going to have to experiment with added cells.

Next I will try 3S+4S+3S and see if the segway is monitoring each 10-NiMH string individually, or the one-of-four assembly as a whole. Based on the complex monitoring circuitry, I suspect it will not fall for this, but who knows.

If I had it to do over again, I would go with 4S (14.8v) packs all around. At 45v peak, that's still within the 'float' charge you might find on 30S NiMH, so I doubt it would fry anything. Anyone experiment in this direction? Does anyone know the resting voltage of the Segway/Valence Lithium packs?
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Old 02-27-2011, 04:06 PM   #25
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Have you considered using prismatic LiFePO4 cells instead of Polymer so you end up with a 12.8V nominal and a safer battery chemistry?
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Old 02-27-2011, 04:06 PM   #26
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Nominal voltage on Valence pack is 73.8V but thats irrelevant since your using a NiMH BMS and not a Lithium BMS.
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Old 02-28-2011, 12:46 AM   #27
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Thanks MTO.
I just asked about LiIon voltage since I was thinking of feeding my segway 45v on each rail instead of the nominal 36. Seems like it will be fine.

The prismatic LiFePO4 or even A123 cells look sweet, but this is a low-budget operation I'm running over here.

Does anyone know if the Segway will run if it gets Power on the correct pins, but no connection on the other pins? It's a longshot. If I could build a battery spoofer that lies about voltage, that might also work. I'd like it to run down to 30v on each rail, to keep using the 9S LiPo arrangement.
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Old 02-28-2011, 02:46 AM   #28
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Quote:
Originally Posted by Ground Loop View Post
Thanks MTO.
I just asked about LiIon voltage since I was thinking of feeding my segway 45v on each rail instead of the nominal 36. Seems like it will be fine.

The prismatic LiFePO4 or even A123 cells look sweet, but this is a low-budget operation I'm running over here.

Does anyone know if the Segway will run if it gets Power on the correct pins, but no connection on the other pins? It's a longshot. If I could build a battery spoofer that lies about voltage, that might also work. I'd like it to run down to 30v on each rail, to keep using the 9S LiPo arrangement.
http://www.hobbyking.com/hobbyking/s...dProduct=16575

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Old 02-28-2011, 08:18 AM   #29
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4S will give you more than 45V on each side when fully charged. Fully charged that pack should be reading ~16.8V per cluster which would be ~50.4V per half or 100.8V per battery. I would be concerned about voltage ratings on PCB components (capacitors, voltage regulators, etc.) inside the Segway as they are likely not rated for that type of voltage.

The Segway will not run on just power. It must have communication with the BMS in order to operate.
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Old 02-28-2011, 02:49 PM   #30
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That's why I was asking about the Valance pack voltages.
If my i167 can be software-upgraded to work with the Valance batteries, then surely the components are cool with the ~50v range, no?

I had no idea HK carried A123 cells. Hm! And at $8/ea, cheaper than EPBuddy.com, where I've been buying them.

I'd like to just bring the power leads out and go to a tethered battery of some sort. Maybe a pack that mounts to the shaft or something. Tired of pulling all these screws out.
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