Mongoose CB 24V450 -Motor Only Range (NiMH)- Pinkerton Park

[knightmb]

The same bike from the SLA distance test using a NiMH battery pack instead.
Original Test Done Here: http://endless-sphere.com/forums/viewtopic.php?t=44

Bike Stats

1. Bike Weight: 64 lbs
2. Tire Pressure: 53.5 PSI both Front and Rear Tires
3. Batteries: (1) 24 Volt @ 12AH NiMH Battery Pack, Full Charge
4. Battery Age: Purchased 3/24/2005

Test Conducted 12/15/2006 @ 10:30AM

Environment Stats

1. Weather: Sunny
2. Winds: N 7 MPH, Gust on Occasion
3. Temperature: 56 F
4. Humidity: 54%
5. Barometer: 29.98

Rider Stats

1. Gender: Male
2. Weight: 170 lbs

Summary:

The day for this test run was sunny and clear. It was cold, so that might affect the test somewhat because the batteries lose some power when they get cold. But since it sat in the garage and it's such a short drive to the park, I ruled out the cold being a major factor, especially once I start driving around because that will heat up the batteries anyway. If anything, the cold weather would keep the motor and controller cool, so less resistance for the power to the motor.

I put on my coat and gloves because I knew this was going to be a cold ride. I started on laps around the park from the 1 mile marker (just like last time). The bike uses an instant start controller, so away I go for many laps around the park. During the ride, speeds stay steady between 16 and 18 MPH. The ride was very straight forward and the cold weather made the park a ghost town. Less people to avoid so it was easy to go full throttle the entire way. I had no problem going up and down hills.

It was a very comfortable ride, here are the results.

Test Ride Results:

• Total Ride Time: 53 Minutes
• Max Speed: 18.7 MPH (30.1 KPH)
• Level Top Speed: 17 MPH (27.4 KPH)
• Average Speed: 14.1 MPH (22.7 KPH)
• Total Ride Distance (unassisted): 12.5 Miles (20.1 Kilometers)

 

[Elmweaver]

hmmm, I am surprised, I thought you might get more then just one mile more. The other test was using batteries that were not broken in yet too.

Just shows to go ya. :lol:

 

[knightmb]

Yeah, I have a feeling that since they are both 12AH battery packs, those SLA will eventually get a good break in period and probably get that extra mile. But overall, it didn't surprise me too much. Both are rated for 12AH, just different battery technologies. But as it goes to show, power is power in the electric world. I think a 24 volt @ 12AH Lith-ion pack would get about the same distance, maybe a tad more since they would decrease the bike weight by a few more pounds.

 

[D-Man]

Yeah, you'd think you would get more miles due to the peukert effort of sla's and everything. Maybe good range and 24 volts doesn't exist unless you have large capacity batteries.

 

[Elmweaver]

Yep I agree with that, of course since the batteries weigh a lot less you could use say 2x24Vx10A NIMH battery packs at about the same weight (as the 2 SLA) and get a pretty good increase in distance, about 20 miles total would be my guess.

Seems that this bike gets about a mile for each rated battery amp. However the NIMH will give it all everytime whereas if you do that to the SLA batteries over and over you will kill them.

NOTE: I think Reid already showed us that the real draw was .77803 amps per mile. Which shows the difference between the 20hr rating and what the real rating is when used at the rate we use them.

 

[knightmb]

Seems that this bike gets about a mile for each rated battery amp. However the NIMH will give it all everytime whereas if you do that to the SLA batteries over and over you will kill them.

Yeah, exactly. My NiMH don't mind a complete discharge. If I did this to my SLA packs that often, they would be dead within the month. So it's kind of a trade-off of how frequently you want to discharge/charge the packs and cost. If you want something that you can burn out everyday and do a full charge overnight, then the NiMH would save you money in the long run. The alternative would be to buy new SLA batteries every month or so, would would cost more in the long run.

 

[Mathurin]

I've seen a study about cold vs. rolling resistance in bikes. They were doing coastdown tests and concluded that it hit especially with underinflated cheap tires, and the kind of grease used in the bearings made a difference. Don't have a link to it, sorry.

But I bet the same batts would fare better with Reid's synthetic grease packed gearbox. (I use synthetic snowmobile grease.)

Dunno how much 10f variation counts though.

 

[knightmb]

That is an excellent point. The tire pressure for both test, I tried to make them the same so it wouldn't skew the results too much. The tires have a max of 65 PSI, which I'm sure if I used that, probably could have gained another mile in distance. The ride would be a little rough, but when range matters the most, comfort takes a back seat

 

[Reid Welch]

Thanks for another high quality test report.

Say, I note two things of particular interest:
your NIMH pack fits neatly into the stock battery box!
That's so handy!

Also, your pack is a year and half old.
It may not retain its original capacity?

Again, excellent report and layout of the data!

Super! Thanks!



---------is this the same pack?

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=995

 

[knightmb]

Thanks for another high quality test report.

Say, I note two things of particular interest:
your NIMH pack fits neatly into the stock battery box!
That's so handy!

Also, your pack is a year and half old.
It may not retain its original capacity?

Given that it's rated at 12 AH and got an extra mile over my 12AH SLA, it seems to be holding steady. I'm going to do more testing with the original SLA and will probably end up getting that extra mile out of it once they are conditioned properly.

Again, excellent report and layout of the data!

Super! Thanks!



---------is this the same pack?

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=995

Yes, same pack. But when I got mine, 13 AH "F" cells weren't being used in the pack. I noticed the new one has an extra 1 AH so I think they are using the 13AH "F" cells instead of the 12AH "F" cells that was used in my pack. The extra AH will probably get you an extra mile at least.

 

[knightmb]

I updated the first post in this topic with an overhead map of the park along with lines showing the 1 mile loop and colors to represent which segments were downhill and which were uphill.

 

[D-Man]

cancel

 

[Reid Welch]

I get only about 7AH from the stock 12AH SLAs because of the Peukert effect.

That's why I wonder whether your NIMH pack has aged and lost capacity.

Sir, you need a Drain Brain


(notice how we converts become big-time prosletizers, ha ha)

 

[knightmb]

It's true, don't have a brain drain. But I do have the next best thing. An amp meter and a bunch of 12 and 24 volt devices to hook up, measure current and just time how long it takes it to kill the battery. Will make for a good experiment for me this weekend 8)

 

[Lessss]

Hmm reverse your direction and you have a tougher course to run for testing the battery.

 

[knightmb]

I would do a bench test at 1c rate to see if Nimh are still in spec. According to graphs, a 12v-12ah sla battery only lasts like 35 minutes at 12 amps. The nimh should go an hour. The range difference should be more noticable even if its not pulling 12 amps. Tha actual 1c rate for a 12v-12ah sla is 7.8 amps according to the graph.

Got one setup and running right now. Boy is this thing loud. It is fun though to see what this battery can take though

It's about to hit the 50 minute mark (from a full charge NiMH pack of course) when I post this. The voltage is getting pretty close to 21 volts, so they won't last much longer I can see.

 

[knightmb]

Wow, that was dang close. The pack hit below 20 volts right around 59 minutes. This test rig works very well. Each fan pulls (?? still determining that because of math problems later on) amp draw on the battery. That's one battery pack down, time for me to try this on the SLA. I'll have to be careful about the voltage on them, don't want to give them an early death. I'm actually letting the NiMH run down as far as it can go since it's been half a year since I've done a complete discharge like this on the pack. Must flush out that "voltage slush" :lol:

 

[Elmweaver]

You want to be careful though I don't think you are supposed to go below 1.0V per cell with NIMH.

I was thinking earlier that its possible the controller is cutting off before your getting to 20V though which is fine and you want that with the SLA cells even though you could go to 1.6V per cell with them before bottoming out.

So NIMH - 1V x 20 = 20V max discharge

SLA - 1.6V x 12 = 19.2V max discharge

Reid, I think said the red light comes on at 21V but do we know the actual cut off voltage for the controller?

Shame currie does not give any specs for the equipment we are using.

 

[knightmb]

I ran them down to about 18 volts, figured that would be enough. There have been times when I've run it down to almost nothing (NiMH that is), which has only happened twice in the life of these packs.

The SLA, I'll be careful with. I'm going to get them when they hit an even 20 volts just to be safe. That's when I stopped the timer for the NiMH, so it should be an even match for the two packs.

 

[knightmb]

Well the results of the SLA (24) volt @ 12AH Pack, it hit under 20 volts in 57 minutes. So the NiMH pack is closer to the 12AH rating than the new SLA pack, but only slightly. Which would explain the extra mile I got out the NiMH pack (had enough juice to make it up that final hill in my test to coast out for some more distance)

Observations during this NiMH vs. SLA trial

1. NiMH Pack started at a strong 28 volts, when the fan load was applied, it dropped the voltage to 26 volts and from there a very linear voltage drop as the battery pack was discharging.
2. SLA Pack started at a strong 28 volts, when the fan load was applied, it dropped the voltage to 24 volts and from there did not have a linear voltage drop.
3. SLA Pack, right around 21 volts, started a rapid decline in voltage when I had about 5 minutes left on the 1C clock.
4. After testing SLA pack, rushed SLA pack it to the charger like a doctor rushing a patient into surgery before he dies

[Hmm, this is a test within a test, I should make a separate topic just for this, will do later :wink: ]

 

[Elmweaver]

I think I should mention that the SLA battery was at a major disadvantage because a 3 amp drain means its rating was more like 9 AH versus the 12 AH of the NIMH.

So, hmmm, does that mean since the NIMH was so close in spec to the SLA that maybe its rating is not 12AH currently either?

Calling Dr. Knightmb, calling Dr. Knightmb, your patient needs you.

 

[D-Man]

Maybe this peukert effect is false.

 

[knightmb]

I'm going to have to figure out which hour rating these are using because you are right, the math doesn't add up with how much fans are using for power.

 

[Elmweaver]

Ok, I have re-read and re-read and it appears I was not talking apples and oranges.

You had 4 fans that draw 3 amps each at 24V connected to the batteries and timed them to see how long they would last? Was that the test?

If so, 12amp draw should have not even lasted close to an hour for the SLA's as the rate would be far lower then the 7.2 one hour rate the BP12 battery shows. The figure quoted of 35 minutes would have been more correct.

So that would mean that the fans must not really be drawing 12 amps continuous. Or yes they are super batteries. I think this was a situation where one of those brain drain thingies would have come in handy.

Either way it still would appear the NIMH battery which should be operating at the 12AH rate even with the 12 amp draw must not be storing the full 12 amps.

As always I could be wrong, please feel free to correct my mistakes. :lol: :lol: :lol:

 

[knightmb]

I got the fan current wrong I'm afraid. The meter does AC amp current, not DC, so I'm having build a simple shunt resistor circuit to connect the fan to so I can measure voltage drops and resistance to figure out how much power the fan uses. I hate it when I confuse the sine wave with the straight line on these meters, but sometimes it's so small, it all looks the same, LOL.