NiMH confusion

[Rock323]

Hi, as a still new e-bike rider, I'm enjoying reading other posts. My entry into the ebike world is wholehearted, but kinda rocky! My bike (eZee sprint) came with an NiMH battery, which lasted two weeks and died... completely died... would not hold a charge for even a quarter mile. Now I have a new battery (the shop was great, sent me a new battery fed ex!), and I've been using it for almost a week now, and I'm finding the performance kindof disappointing. So far, using the battery sparingly, only for a boost on uphill grades, pedalling all the time, I can only go about 8 miles. Then I notice the meter sticking for a few seconds in the yellow, which I think indicates the battery is at full discharge and further use will damage it. So when that has happened I stop using the battery and just pedal. I've read it can take a few uses to "condition" the battery. But even after 6 rides, I'm not seeing an improvement. Basically, I'm getting nervous... do I just have bad battery karma? Are these batteries really that finicky? I would love a consistent set of principles on use and care of the NiMH battery! I've read conflicting information, like one place saying they need to be fully discharged once a month or so, and others say that full discharge causes irreparable damage. What is the line? What about charging, is it ok to pull them off the charger before full charge, is it ok to leave the battery on the charger after the full charge indicator has come on. One thing I notice is that I can fully charge the battery, take it off the charger overnight, plug it in to top it off in the morning, and find that it takes hours to get back up to the full charge. Is that normal? Both the old/dead battery and the new one are the same in that regard.

grateful for any feedback!

[dman-ebike]

Specs for Ezee sprint:

Electric drive system:
Maximum Speed : 20 mph
Range: Up to 30 miles (with pedaling)
Weight : 65 lbs
Motor: Brushless Servo motor 700 watt peak with a continuous rating of 350 watt with planetary gears.
Controller: PWM, digital, self diagnostic indicator, overload protection 16 amps, low voltage protection - 31.5 V
Battery: 36V 9Ah NiMH battery, or 36V 10 Ah Lithium ion battery, (Li-ion)
Charger: Charge current 2 amps., maximum charge time 5.5 hours

I'd hook up a voltmeter and see whats really going on. Check the voltage of the batteries before/during/after charging and riding etc... Check actual cutoff voltage also when bike cuts out. They claim its 31.5 above. 36v at 9ah of battery with 16amp protection should last more then 8 miles unless your going straight uphill for the 8 miles. Fully charged battery should read 1.4 volts per cell resting so that comes to 42 volts charged pack.

[Rock323]

I'd hook up a voltmeter and see whats really going on. Check the voltage of the batteries before/during/after charging and riding etc... Check actual cutoff voltage also when bike cuts out. They claim its 31.5 above. 36v at 9ah of battery with 16amp protection should last more then 8 miles unless your going straight uphill for the 8 miles. Fully charged battery should read 1.4 volts per cell resting so that comes to 42 volts charged pack.

Any particular type of voltmeter? After a trip to the hardware store, I'm not sure what to get?

Thanks!

[piper_chuck]

Are these batteries really that finicky? I would love a consistent set of principles on use and care of the NiMH battery! I've read conflicting information, like one place saying they need to be fully discharged once a month or so, and others say that full discharge causes irreparable damage. What is the line? What about charging, is it ok to pull them off the charger before full charge, is it ok to leave the battery on the charger after the full charge indicator has come on. One thing I notice is that I can fully charge the battery, take it off the charger overnight, plug it in to top it off in the morning, and find that it takes hours to get back up to the full charge. Is that normal? Both the old/dead battery and the new one are the same in that regard.

grateful for any feedback!
I've only got a few minutes, but I can at least point you to a place with reliable information: http://www.rcbatteryclinic.com/ . I realize the site has nothing to do with cycling, but the guy who owns it knows his stuff.

In answer to one of your questions, fully discharging a NiMH battery will damage it. Don't do this at all. There's more about this at Red's site.

[dhofmann]

You can't fully discharge the battery on the eZee sprint because it has low voltage protection. So don't worry about running it all the way down.

If you pull the battery off the charger before it's done, it may make it develop memory faster. Eventually you won't be able to give it a full charge until you recondition it. But that's not difficult to do. After 60 charges, mine (Crystalyte) would no longer charge fully, so I ran it all the way down, charged it up all the way, ran it all the way down again, and now it charges properly again.

It's normal for NiMH batteries to self-discharge, especially when they're topped off. You can leave the battery on the charger overnight, but they recommend not keeping it on the charger for more than a few days at a time.

[Rock323]

thanks, I did check out the site, and learned a lot, especially regarding the danger of overcharging. Evidently my charger is a "smart" one, so that should not be an issue. I'm thinking I'll need to take that suggestion about a voltmeter to really figure out "the line" between discharged and fully discharged.

[jerryt]

Rock,
I hope by now you are doing Ok with your batteries.

I have an eZee (Quando) with NiMh batteries and here is my experience:

When I purchased my bike I was advised to ride until the batteries cut out and then recharge them and to do so again about once a month to prevent "memory" effects.

I rely solely on the eZee LED system to report my battery condition:
1. Green = battery is OK and charged
2. Yellow = battery discharging normally
3. Red = Battery discharging at an accelerated rate

(These may not be exact definitions)

With my weight and riding style, I learned to expect 15 to 18 miles range and I generally ride with minimal (low exertion) pedalling (just enough to stay "green" mostly). As I approach my max range, my LED will dip into the "yellow" more often and then into the "red". Then I will usually pedal a little harder to stay in the green and yellow but know it is now time to recharge.

Once in a while (once a month is recommended) I will continue to ride until the battery cuts out completely. The battery is now drained near exhaustion however, the Ezee controller doesn't allow a total battery drain which causes damage.

I know I'm putting a lot of faith in my equipment and I'm not an expert and only had this bike about three months so take this advice with a grain of salt.

[Rock323]

Hey Jerry, thanks... that's really helpful info! Over the past several weeks, I've really puzzled over that stuff, and gradually figured out the stuff you just confirmed except I just could never get much range. I'm not sure whether the problem was in the battery(s) or the charger, but I've had two batteries now that only had about a 5 mile range, 8 miles tops. The first battery was the one that came with the bike and after a couple of weeks, it would go into the red after only a quarter mile or so. The shop supplied me with a second battery, and I never could get much range out of it (5-8 miles), pedalling constantly. I suspected the charger because they seemed to hold less and less of a charge. I did run them to "cut out" a couple of times to see if that would help, but I didn't gain much, if any in terms of range. So, this past weekend, I took the NiMH batteries and charger back to the shop and exchanged them for LiOn. Haven't tried it yet, and I'm hopeful... I love the bike... I think I just had some bad luck... I started to get a bit paranoid about the NiMH batteries, though I've read that when they work right they're great.

Thanks again!
Rocklynn

[jerryt]

Rock I hope you have luck with the Lithiums and hope you were under warranty on the NiMh.
Since you're familiar with the Pedelecs forum you are probably aware that eZee had trouble with the lithium batts and changed suppliers. I believe their new supplier is Sanyo (in England) but don't know when or if they will be available here. Can you tell (or ask) who mfg your batts?
Keep us posted how they work for you. I intend to upgrade when my NiMh's are done.

[Rock323]

Jerry, still haven't ridden with the new battery due to a nasty cold and too much wind. I'm aware of the problems with the lithiums (mainly cutting out on hills and shortened battery life), though this battery is supposed to be from a newer batch. It's a Phylion, not Sanyo. I've been reading the pedelecs forum too, and it sounds like the Sanyos are doing very well. My NiMH was still under waranty, and I'm happy to say that they upgraded me to lithium with no charge. I'll let you know when I get out and ride a couple times with the new bat...

[jerryt]

Lithium replace @ no charge and I assume including charger. Good dealer.

[Rock323]

Jerry, I'm happy to report that I rode my eZee Sprint 24 mile yesterday with the new lithium battery, up and down many hills. This morning I rode to work with the biggest grin, seeing speeds from 12 up to 20 mph. With the NiMH I was constantly trying to conserve the battery, pedaling without assist on flats so that I could save the battery for hills, and even then I would be flat out of battery for the last couple miles of my 10 mile commute. The new battery makes all the difference. :)