Newbie trying to figure out battery cutout

[EDM3]

I'm a freshly minted electrified cyclist after considering it for a year or two.
I picked up a 9C 2806 front motor, with a 36V 10Ah Lithium Manganese battery, Infineon 25Amp Controller, Direct plugin Cycle Analyst, and a thumb-throttle a few days ago.

I've tested it 3 days in a row now (all of which in Vancouver downpour we're currently in the middle of), and am having some issues with the motor/battery/Controller (I don't know which one exactly) cutting out. On each ride, I gradually waterproof everything more and more. Today, in fact, everything but the motor, and throttle were exposed (the CA had a clear plastic shield). The controller was in tupperwear under the snapdeck of my xtracycle, the battery was located in the xtracycle bag, within a plastic bag/within an EZee battery bag).

As I'm a newbie and still trying to figure out the info that the CA is giving me, I may be somewhat out to lunch. But I'm tired from hauling a motorized bike up the last 10 k of hills - so I'm requesting some insight from you folks.

All connections have liberal amounts of dialectric grease (with the exception of the Anderson battery connector - which just might be the problem ).

So I'm finding that at about 5.7Ah, on 2 occasions now, the power cuts out, the CA shortly thereafter goes blank, but still backlit - sometimes the back lighting goes out from time to time. I turn battery off/on and then the CA starts reading in the 17V neighbourhood, when last time I checked it was reading ~37. Then I go through off/on a few times, the CA will be displaying speed, etc, but no juice from throttle. More off/ons and I start getting funny readings like 17V, slowly climbing into high 20's. More off/ons and then it reads ~38V and I nurse the juice drawing <300watts, usually around 150w. Then It cuts out again and gives nothing but backlight, if that.

Could my 10Ah battery lose its ability to power my rig after only 5.7 Ah of use? I have to admit that today's first 20k were using only full power or nothing/ always cranking / and only powering on hills (as slight as they may be

Any ideas on what I may be doing wrong, or is this standard operating process from an electric assist?

Thanks!

 

[ekingsting]

Thats about right for the battery as it will only deliver 10 amps if you take .5amp discharge for 20hrs. The more amps you use at one time ( full throttle) the less amp hours the battery will deliver. Check out the "Characteristics chart" on this linkhttp://www.tempestbatteries.com/html/tr10-12.html and you will see it will only deliver about 4.38ah in 15 min. at full throttle. Using less throttle will increase batteries usable capacity but you will never get 10ah out of your batts on an ebike using 10amp sla's.

 

[Icewrench]

10 amp hour li mn should be good for at least 10 miles 16 km I think of full power use , with out pedaling.
A new battery might benefit from a few shallow discharge cycles to ``break it in`` .
Closely check all power connections give them a tug to be sure crimps are tight and secure, sounds like a poor connection what with the wide range of voltage readings.
Good luck.

 

[EDM3]

Thanks for your help Icewrench and ekingsting. Gradually putting the pieces together here. Still digesting the "characteristics chart", as I've always shied away from anything electrical - but have to say that I'm finding it fascinating. Now I know what the nerds were going through in high school while I was smoking darts and chasing girls

What I actually find really interesting is that since electrifying my rig, the hills around here seem to express their size even more than when I'm pedal power alone. I guess the electric rigging really forces you to monitor energy output, and is far less capable of 'digging deep' than something biological. Torque is very impressive though.

Thanks again for your help.

 

[dogman dan]

You'll get a lot less range out of your rig on hills. You will get a lot more strain on the battery, in the form of high discharge rate with a smaller battery, such as 10 ah. You may have less capacity in cool weather than in warm. It takes some time to learn to use the motor efficiently, which again costs you range. So you may have everything ok, but be running the battery down sooner than you think. Slowing down some, starting out slower, and setting the throttle at a set speed and pedaling to go a bit faster should help the ride efficiency. Make sure you have the battery fully charged too, it may need to stay on longer if it has a bms that balances for awhile after the green light is first seen.

I'd be inclined to test the motor and battery inside, in the warm. With the wheel off the ground, you can run the motor no load, which uses little power. It will take a long time, but you could eventually run the battery till it cuts off, or goes farther than 6 ah. Breaking in the battery by riding too far the first few rides is not often recomended too, so put in a few short ride followed by charging cycles before this test. If you rode till the battery died on cycle 1, you may have even damaged the battery. Or helped a weak cell in there die sooner. There is some argument about how many cycles to break in a battery, but cycle 1 is usually agreed to be better to keep it light.

 

[EDM3]

Thanks for the advice dogman. Very helpful.

Thankfully, my first 2 rides, and subsequent charges, were relatively short. I think it was ride 3 and 5 that I killed it 10k from home. I already promised my battery that the days of 100%/0% throttle are over..

I think I'll set up and do an indoor discharge test as you suggested. The weather is too nasty today, and where I have to go is definitely beyond the range of my battery (especially in this weather).

Once again, much thanks.

 

[Drunkskunk]

You might need to check the calibration of the CA. 5.7 amps shouldn't have gotten you 20Km with throttle only unless you were crawling along at a snails pace. Sounds like you used most of the battery, and hit the LVC

 

[EDM3]

OK - so I did the indoor, no load, test of battery life and the wheel spun for about 170km!! Looks like I have to lose some weight to get the range I want out of this thing. It hummed along for hours with the speed fairly constant at about 52-53km/hr @ about 55W. Then, at about 4.25 Ah, and the Voltage dropped from about 55 to 51Watts of output, the speed decreased to the 47km/hr range. I noticed the power taking a "step" down just by the sound. Then, maybe an hour + later, it died and I didn't take any final readings.

I've got it charged now, but I'm leaving it plugged in for a couple hours just in case any of that cell balancing stuff wants to happen. I've still not plugged into the CA.

One interesting thing is that the battery charged much quicker than any of the previous charges. It's a 4A charger that is apparently supposed to charge in the 2-2.5hr range. Tonight it did that for the first time. Earlier charges were easily over 4 hrs. So I'm guessing that the battery is just getting its' groove on. Looking forward to more trials outside.

Drunkskunk - I have only ridden about 100meters without cranking so far. I guess it's just a habit that's tough to brake So the 20Km was only electrified on up-hills with pedal assistance. I don't know what LVC is.

Thanks again folks.

 

[dogman dan]

If it's just the battery breaking in, actually we should say initial balancing, it's doing it awfull slow. I was hoping to see a big improvement in the capacity when in a warm room compared to outside. Also the slower discharge should have improved that number too. Have you even talked to Ebikes-ca about it? Maybe you got a pack with one or more cells in it that underperform. Unfortunately bench tests on new cells don't always weed out the runts. Or a wire could have come loose on the bms, not letting a cell balance completely.

 

[Drunkskunk]

LVC means Low Voltage Cutoff. Its a safety device built into the battery and the controller to cut power when the voltage drops too low. Its usualy a bad Idea to run a battery down to this point, but to so occasionaly is fine.

How long did you run that indoor test for?
a 36v 10Ah battery (360 Watt hours) would have taken roughly 6 and a half hours to drain at roughly 55 watts. if it came close to that, then you may indeed be getting your full 10Ah out of the battery.

 

[EDM3]

Back from more testing - without rain Until just before getting home - but at least I'm not killing the battery before home for the past 2 trips.

I did record the final numbers from my indoor test after I posted here. They're as follows:

199.3 km
5.487 Ah
218.59 Watt-hrs
1.0 Wh/km
Amin -0.61
Amax 15.36
Vmin 20.0
total time 4:08:21
Max speed 49.9 (I thought I'd seen faster while running, but I'd rather not quote my brain)
AvgS 48.1

So it seems to be short by nearly 2.5hours of run time, based on Drunkskunk's comment - Could I have a dud battery here? (Upon re-reading your comment my understanding of the W-A-V equasion gets slightly deeper).

I did a couple of cycles today - all cranking and using assist primarily on hills, but I was lazy today and did like the sunny air blowing on my face (these all include some decent hills), and in metric:

total time 37:07
15.63 km
2.683 Ah
39.4V (left)
109.59 Watt-hrs
6.5 Wh/km
7.7% regen
0.2047 Regen Ah
2.8908 Fwd Ah
Amin -10.7
Amax 28.37
Vmin 34.4
Max S 54.5
AvgS 25.2

This afternoon's ride:

21.17 km
39.8 V (just took the reading now, and battery has been plugged in for ~45mins, so not accurate)
3.504 Ah (last hill home took ~1.1ish Ah)
156.00 Watt-hrs
4.8 Wh/km
18.2% regen (Iknow, I'm getting crazy on regen - even peddaling with brakes - need more, need more Actually, about 50% through this eve's ride, I was at 67% regen and felt like a champion of efficiency )
Regen Ah 0.6404
Fwd Ah 4.1452
Amin -13.7
Amax 29.2
Vmin 24.7
MaxS 45.6
AvgS 21.6
total time 1:15:15

Just wondering, you folks can't tell how many beers I had at the beach from these numbers can you? Kidding...

Anyway, I feel like I'm getting a much better sense of how the motor/battery like to be treated, but I'm still confused by the Ah's business - it's like amp hours are in some other dimension to our hours I suppose. And I suppose that's the case, based on the discharge rate, no? And I am starting to feel like I can live with the system and feel somewhat satisfied by it's performance. I certainly welcome any of your opinions on this, as I'm just starting to peel away the first layer of understanding of all these numbers.

Once again, your comments have been very helpful.

 

[dogman dan]

How long are you leaving it on the charger? Overnight? or take it off as soon as you see a green light. Leave it on the charger 24-7 for awhile.

 

[Drunkskunk]

Just wondering, you folks can't tell how many beers I had at the beach from these numbers can you?...

2 to 3.

The 4 hour indoor test eliminated CA/controller interface callibration missmatch trouble possabilities. That would have been easier to fix than it is to read that sentence. But your tests are showing it is probably a battery issue. Doing as dogman sugests will let it balance if one cell is just way out. If that doesn't work, time to try out the warrenty.
Since you called it a 2806, I'm guessing you got it from Ebikes.ca? You can probably send them a link to your posts here so they can see what the battery is doing and what you're Tried.

 

[EDM3]

I've only left it on for an extended period (4+) hours post-green light. I've plugged the charger back in and will leave it plugged in until tomorrow and see if I get a change.

Thanks again - super helpful.

 

[John in CR]

EDM3,

The voltage on LiMN sags heavily in the lower 1/3 to 1/2 of their capacity. In simplistic terms, once you get below half a tank and you start climbing hills, then your LVC is going to kick in. I use sony 18650V and 18650VT's, which are great LiMN cells, on a daily basis. I ran out of juice once, and hobbled home on flat road once. As soon as you notice a significant power decrease, just forget it and pedal the rest of the way, or maybe save a bit of recovered assistance for that last hill climb.

If you aren't feeling a quickly decrease in your power over a relatively short distance (1km on flat road), then maybe the LVC of your controller is a bit high. Instead of adjusting it, in the interest of far greater battery life, add some more capacity to your pack. Send a PM to Doc Bass here on the forum, and maybe he can fix you up with the cells needed for a nice little range booster pack with very little electrical know how or out of pocket $. Whatever you spend will more than pay for itself, because you are inadvertently killing your current pack prematurely. I run my packs very conservatively, and in over a year of daily use I've seen no appreciable degradation using cells with a factory estimated life of 500-600 cycles. I average 2 cycles daily, but they are only about 60% of rated capacity with only 90-95% maximum charge.

Staying in that 90-95% top of charge and 50-60% depth of discharge is exactly how Toyota gets 10 years out of their NiMH packs in Prius's. Yes those are inferior to LiMN cells, but I firmly believe that using batteries conservatively regardless of chemistry leads to drastically longer useful life, and batteries should be the single largest expense amortized over the life of our EVs. Also, if you can stretch 2-3yrs out of your current pack, then far greater batteries will be available to replace them. Lithium battery prices decreased by a solid 50% in the past year to year and a half, and useful lives are getting out near a decade. eg A123 has some 100k cycle test results on their newer cells using shallow discharge rates. That's cycle life getting out there so far that you move your old battery pack into your next new car, and I can't wait till those become available for our DIY use.

Bottom line- Spend your money on more batteries now, and the savings will more than pay for itself once you consider the time value of money. Just don't go crazy and get more than 150-200% of what you need for your commute, because battery tech is improving so rapidly that then you'll end up with batteries that are still good, but obsolete.

Just don't be like the guys trying to run 90%+ of original rated capacity of your pack to meet your daily commute. First, you're killing your batts. Second, all batteries have some Peukert's Effect, some chemistries more than others, but regardless the harder you drive them, the less capacity they have. That means even when new, they don't live as long when you drive them hard (ie near full capacity).

 

[EDM3]

John in CR,

Many thanks for the loaded response. I've had to read it a couple times to ensure I got the message. The EV electrical fog is gradually lifting thanks to you folks.

I'm tempted to get more battery capacity - especially due to the somewhat small amount of range I seem to have with this one. I must say that I am learning to be a better EV rider and, therefore, extending my range. Problem is, most rides I do aren't commuting (home office), but running errands, meetings and such that usually run me a minimum of 30km - and that generally tends to eat a good portion of my battery if I'm not very stingy on it and crazy on regen.

BTW - I live up on a hill and have heard that it's not good to regen when the battery is full. Is this the case? Is it recommended that I tool around and use up some juice before I regen (use brakes) going down the hill to most of my destinations?

Back to increasing capacity - is it a pretty straightforward operation to just add more batteries to my system, or does it require some serious know-how and subsequent care? I'll try and find some info on this..

Thanks again for the insight!

 

[EDM3]

Just an update...
It looks like there was likely a dud cell in the battery. Justin set me up with a new battery yesterday while they test the 'strange' one. The replacement battery seems to be much better already. Had a nice 20km 'break-in' ride last night that was splendid. Charged the batt when I got home, bringing it up to about 41.7V. Today, before my ride, it read a little lower voltage, so I topped it up and went out for 40km of relatively lazy riding on my part (which must have had some of the roadies I overtook scratching their heads).
Anyway, returned home with 6.6Ah used (yahoo, I've broken the 5.7Ah barrier, and the battery recovered to 38.5V (it dipped as low as 34.4 on the last long uphill). So I haven't found the bottom of the battery, but it feels good. And it has me waaay less in second-guessing mode of moving to electrification.

In my concern of not having enough juice to do my regular trips, not to mention longer trips, I sprung for another battery pack - the 36V 8Ah NiCad package that ebikes.ca has going for 200 skins. I couldn't pass it up.

So not only do my battery woes appear to be gone, I'm feeling a surplus of juice!

Thanks to you all for your help in the past week.