Interesting Range results!!!

[snowcrow]

Did a 14.8 mile trek today and got some interesting range results! The route was mostly hilly paved secondary roads with one mile dirt. (Posted Below)


I used the throttle just enough to make the peddling easy in high gear and on the hills.

Whats interesting is the voltage didn't change much, I started at 52.5v and ended at 50v even. Thats only about 20% down, is that right?!

Blessings, Snow Crow

 

[Link]

What sort of batteries? Voltage isn't a very good indicator for remaining capacity. Except for SLAs, where it's an okay SOC indicator.

 

[snowcrow]

What sort of batteries? Voltage isn't a very good indicator for remaining capacity. Except for SLAs, where it's an okay SOC indicator.

Yes Link, I am using SLA's (4) Zeus 12v 12ah 8)

 

[Link]

Hmm, those might be some good batts. No 12Ah SLA is gonna go 75 miles at any speed.

You need a wattmeter to get some info on how those batteries are performing. 8) Knowing how much energy you have left in the batteries is nice, too. :wink:

 

[mvadventure]

When I ran SLA's a gentle 15 mile run was common but I used a "watts up" meter to evaluate battery condition and monitor the AH used. By keeping the speed low, <15 mph, and watching to make sure I didn't get much above 8 AH used the pack worked fine. The Crystalyte 4840 controller would indicate low battery by allowing the yellow light to shine on the throttle around the 8 AH mark and power would greatly decline and cut off if too much throttle was applied. There was NO power at 48 volts and forward motion was available only through the pedals.

There is no doubt the Cycle Analyst is a better device and has many more features and probably worth the extra money yet the watts up works fine for me. By monitoring the meter I learned that cruising at 15 MPH on flat terrain would give me almost three miles per AH and 25 MPH reduced that to 1 AH per mile. Cruising at 20 MPH provides more than 2 miles per AH and is a happy medium. Going up a hill, slight or steep, shows a remarkable increase in power required and a meter helps you evaluate how much range it's costing you.

The limited range however got to me and I bit the bullet for the LiPO4's and couldn't be happier. With the new batteries I can almost ignore the meter if trips are less than 20 miles and don't really pay much attention unless 30 miles or more are going to be required. Then again I mostly use the pedals to hold my feet off the ground, not to turn the wheels with. Pedaling my bike, even at 15 MPH, isn't really possible unless you really want to work at it.

Good luck, enjoy the experience and the EVGrin.
Mike (Crystalyte 5304 on a steel beach bike)

 

[snowcrow]

Well....it was just a Sunday ride, 15 mph or so, not trying to break any land speed records 8) It might just be that I'm in better shape than I thought, I did run cross country, bike and hike in my youth, not much lately thou :wink: I do have a "Watts Up" meter, but it's up to camp right now, about 120 miles north. I do have it on my list of thing to bring back and was planning on using it for that purpose. Yes, that LED on the throttle only tells you that you're on your own :? not much help really! The bike is still a "work in progress" and I hope to be adding that meter by this coming weekend! Blessings, Snow Crow

 

[safe]

You also have sag while riding with SLA's that won't show up afterwards because the cells will recharge themselves somewhat the moment you stop. The voltage tends to float higher than really reflects what's left inside.

SLA's typically start at 13.1 volts (52.4 volts)

And will be "empty enough" at about 12.0 volts (48 volts)

...so I would guess your 50 volt ending was probably about 50%-80% of your realistically usable capacity, but some people drag their cells down to 10.0 volts even though you get very little extra power going that far down.

 

[snowcrow]

You also have sag while riding with SLA's that won't show up afterwards because the cells will recharge themselves somewhat the moment you stop. The voltage tends to float higher than really reflects what's left inside.

SLA's typically start at 13.1 volts (52.4 volts)

And will be "empty enough" at about 12.0 volts (48 volts)

...so I would guess your 50 volt ending was probably about 50%-80% of your realistically usable capacity, but some people drag their cells down to 10.0 volts even though you get very little extra power going that far down.

I don't think I'd want to drag the batteries down to 10.0 volts, that is risking hard sulphate forming on the plates in SLA's. I generally go down to 11.85 volts before calling the battery discharged, but thats for FLA (flooded lead acid) batteries. I have worked with FLA (flooded lead acid) batteries the last 4 years, and they are a lot more forgiving to abuse than the SLA (starved lead acid) batteries are. You can't speed charge, or equalize SLA's with damaging them. About 10% of the total amp-hour is used as the max. charge rate, I think I guess if the controller's cut-off voltage is 48 volts, then thats it's going to be, Oh well.... :? Not sure what the term "sag" refers to, the voltage drop thats do to the lack of available current, which rebounds after you remove a load? Blessings, Snow Crow

 

[dogman dan]

Ride a bit at full throttle and you'll see votage sag very easy. For my watt hog brushed motors, I would get a real fast first mile, then settle in for 75% of the ride at a slightly slower pace, and the last bit, really really slow. The lifepo4 pretty much runs the same speed for 90% of the ride, and slows only slighltly before at the end when the voltage just vanishes.

 

[docnjoj]

Not sure what the term "sag" refers to, the voltage drop thats do to the lack of available current, which rebounds after you remove a load? Blessings, Snow Crow
Yup! Thats Sag or Peukert effect if ya gotta be an engineer type! Lead is bad, Nicad better, NiMh not so good, LiFePo4 really good!
otherDoc

 

[kbarrett]

Yep ... LiFePO4 will go all they way to the end without any real sag. My ping pack starts at 40V, and will go all the way down to about 30V before the BMS shuts them down ... and will have put out 16.5 AH total. The drop from 33V to 30V is steep and damned fast.

LiFePO4 will dump its rated load, and nearly full voltage, and then suddenly kill itself and end up zero voltage or reversed at near zero. The BMS is there to prevent the batt from killing itself by jumping off that overdischarge ledge.

A lead batt may be rated for, say, 12Ah ... but squeezing out the last half of it will require a lot of low voltage low amp load use because of sag/peukert effect.

 

[snowcrow]

So...the peukert effect is only a real issue for SLA's :? and it only gets worse as the batteries age I guess it's time to start saving up for a "ping pack"and take the plung myself 8) The SLA's should last me a while, as I don't use the bike to commute, just for riding around town. Well... it's a start. Blessings, Snow Crow

 

[dogman dan]

Weight is an even bigger issue in my opinion. My 36v 12 ah sla's weigh 33 pounds. 36v 20 ah ping is 15. Of course with the Ping though, I can ride till my motor melts. But you won't have my weather.

 

[snowcrow]

Weight is an even bigger issue in my opinion. My 36v 12 ah sla's weigh 33 pounds. 36v 20 ah ping is 15. Of course with the Ping though, I can ride till my motor melts. But you won't have my weather.

Yes I know, cause I'm running 48v :? Don't think I would like running out of juice, it would be like peddling a Buick up some of those hills As it is, the motor does growls a bit going up some of those long 8% grade hills. Blessings, Snow Crow

 

[Link]

I'm finding the motor itself is dragging me down WAY more than anything else on the bike. I can barely manage 14mph with the thing on there. I can only do about 8mph comfortably. :?

 

[safe]

SLA's work better when you don't try to drain them too fast. So you need to have a big SLA battery and lot's of gears to be able to keep the current low and still get around. You can do very well with SLA if you configure your bike around it.

The other chemistries (NiCad, NiMh, LiFePO4) just make life easier... you can use your power any way you want and just not have to think about it.

SLA requires some serious thought to make useful.

...I'm migrating to NiCad SubC's now because they seem to (for the moment) be the best overall as far as cost and performance. They can pull 10C and yet they only cost about $1.40 each cell on eBay. However, you need to assemble the cells by either soldering them together or making yourself some solderless tubes, so there's an extra step that separates you from quickly using them.

The Pings look like a good choice and I might try them some day too... seems like people are bidding them up alot and they are always getting sold for like $400-$500 when the bidding ends. (my NiCad's ended up about $200 per bike)