Tenergy batteries

[jha07]

I'm the type of guy that usually researches everything before I buy it. But when it came to choosing NiMh cells, I went out of character and just bought the cheapest cells I could find. For some odd reason, I actually believed their product description.

I came across the site allbattery.com and found super cheap prices. They sell mostly Tenergy cells, which I figured is a house brand. I decided to use Sub C instead of C or D mainly because they were cheaper and lighter. They also claimed to have a max discharge rate of 40A. My commute is only 12Km one way, and I was planning on charging when I got to work. So even with a 3800mah sub c pack, I'd get over 20km range, which would be fine.

Well, I got the cells a few days ago. Only took them a week for shipping, which was quite impressive. First impressions, the cells looked cheap and seemed lighter then they should be. I'm was comparing their weight to old 1700mah NiCd I had. I ordered them in 7 cell packs and soldered 5 packs together to make a 35 cell pack. I also bought a universal charger from them, which was capable of charging 30-40 cells @ 1A.

During the first charge, I was keeping an eye on them and checking the temp regularly. At around 2 hours, the pack started getting warm. At 2:15 hours, the temp was well above what I consider safe. But the charger just kept going. At 2:25, I disconnected it. I was surprised it took so little charge, since a 3800mah cell should take at least 4 hours @ 1A. I figured it could be because the cells weren't fully drained. I let the pack cool down and the next day try to peak charge the pack again. After about 25 mins of charge, I had to disconnect it again due to high temp. Again the charger never detected the peak.
Anyhow, on my first test run, I got about 12km range. This confirms that the battery capacity is around 2300mah. I'm guessing this will go up some with a few cycles, but I'm along way off the claimed 3800mah.
Hopefully, these cells will be good enough for me to commute with, but I'm already looking for replacements.
Does anyone have experience with Powerizer cells? They have a 4200mah sub c, which has a spec sheet that seems legit. They seem to actually be able to put out over 4Ah. But having just spent a bunch of money on junks cells and a defective charger, I've a bit skeptical of product claims.

Btw, after getting such poor results on the cells. I did a bit of research and found that a lot of people have similar experiences with tenergy cells.

 

[flecc]

I only know of one member buying Batteryspace/Poweriser cells, that was a 10 Ah 24 volt D cell pack, and that worked fine and met it's spec. They did have a bad patch due to poor quality control a bit over a year ago, but put some effort in, raised the prices a bit and improved the quality control.

Their chargers are rubbish though. By all means buy cells or packs from them, but buy much better chargers from Powerstream, also in the USA and benefitting from the current favourable US/UK exchange rate.
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[giguana]

sorry about that, thank you for the heads up...I hope you can get your money back because the information was misleading. I was also going to buy sub-c from vapextech but I was worried that there would be reversal really fast because of the smaller capacities of such cells. I'm still really confused about the inevitability of reversal. hope that your luck turns and you get some excellent ones.

 

[Grizzly Bear]

May I suggest you read my post "Batteries from the USA" before dealing with these people.

 

[jha07]

I only know of one member buying Batteryspace/Poweriser cells, that was a 10 Ah 24 volt D cell pack, and that worked fine and met it's spec. They did have a bad patch due to poor quality control a bit over a year ago, but put some effort in, raised the prices a bit and improved the quality control.

Their chargers are rubbish though. By all means buy cells or packs from them, but buy much better chargers from Powerstream, also in the USA and benefitting from the current favourable US/UK exchange rate.
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Thanks. I'll be sure to avoid the batteryspace chargers. I think I'll either get a charger locally from ebikes, or order one from powerstream. At the moment, I'm still not sure the number of cells I want to run. I was planning to do 35 cells. My defective charger was suppose to be able to charge anything between 30-40. I haven't found another charger that makes that claim, so now I have to pick between 30 or 40. 30 cells will do about 27ish km/h, which seems slow to me. And 40 cells should do about 36 km/h, which is plenty fast but will drain my batteries a bit too fast. It'll be a tough decision.

Glad to hear the Powerizer D cells worked fine. I might end up getting some sub C from them. I also found some good priced 'Elite' cells from cheapbatterypacks.com. The cells seem to meet and surpass their ratings. Of course I'll have to look into it more.

 

[jha07]

sorry about that, thank you for the heads up...I hope you can get your money back because the information was misleading. I was also going to buy sub-c from vapextech but I was worried that there would be reversal really fast because of the smaller capacities of such cells. I'm still really confused about the inevitability of reversal. hope that your luck turns and you get some excellent ones.

I think my experience with Tenergy sub C cells shouldn't scare you off of all sub C cells. I still plan on using sub C, just ones that meet their ratings. I only paid $2 per cell, so I guess I shouldn't be too shocked that they don't do what they claim. I think $4-$5 a cell should get you something decent.
Cell reversal will only happen if you drain your pack so low that the weakest cell has nothing left. As long as you stop when you feel your pack is near empty and don't over do it. It should be fine.
I really like the lower cost and weight of sub C when compared to D. And I think if 4Ah is enough for your needs, sub C are a better choice. Some high end cells are close to 5Ah, and a 48V pack will weigh just a bit over 5 pounds. Also, decent sub C have high discharge rates, over 40A. Much better than the C cells I've seen.

 

[Ian]

Just a Thought

It's worth remembering that the capacity of all batteries reduces with increased discharge rates and nominal capacities are quoted at a 10 or 20 hour rate which is far lower than that encountered in bike applications. Therefore a 5Ah battery will cover less than half the range of a 10Ah battery, likewise a 20Ah battery (bliss) would go more than twice as far as the 10Ah battery.

NiMh packs really should have a thermistor to detect the rapid increase in temperature that occurs if charging continues beyond the voltage cut off, a decent charger should have provision for this.

It's possible that due to poor matching of the cells there is no clearly defined rise in voltage (dV/dT) from the pack as a whole at full charge, hence the charger just carries on.

 

[Jeremy]

Looking around it does seem as if the sub-C cells offer the best high current discharge characteristics and favourable pricing. I am pretty sure this is because this size cell is popular for high-discharge applications, like power tools and RC models, so has been subject to a fair bit of product development.

In another life, I used high voltage NiCd packs in a demanding aerospace application. We found that trying to charge more than about ten cells in series was fraught with difficulty, due to the need to maintain all cells in the same state of charge. Discharging them in series, even with packs of 30 or more cells, works well, but if the cells get even slightly out of balance you can easily end up with problems in a big pack.

One simple solution is to arrange to discharge the cells in series, but charge each 12V sub-pack via it's own charger. Although slightly cumbersome, this does reduce the chance of damaging cells.

A better solution is to look at incorporating a battery management system to keep the cells in balance, or to buy accurately matched cells (this latter method is what the manufacturers of ebikes tend to do, I believe).

I'm seriously thinking of using 12V RC model sub-C packs, but if I do then I intend to build a relatively simple multi-pack charger to ensure reliability.

 

[Tiberius]

I have just received a large number of AA cells and a charger from Batteryspace. I'll be experiementing with those over the break.

Nick

 

[flecc]

Hi Nick, don't know if you saw this originally?
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[Tiberius]

flecc,

Cheers, yes I read that and it informed my thinking greatly. AA cells are quite attractive in terms of price and weight for the current and Ah delivered. I'm not going to do exactly what you did but your results were useful in formulating my own cunning plan.

Nick

 

[flecc]

I guessed that Nick, look forward to hearing about it.
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[jha07]

It's worth remembering that the capacity of all batteries reduces with increased discharge rates and nominal capacities are quoted at a 10 or 20 hour rate which is far lower than that encountered in bike applications. Therefore a 5Ah battery will cover less than half the range of a 10Ah battery, likewise a 20Ah battery (bliss) would go more than twice as far as the 10Ah battery.

NiMh packs really should have a thermistor to detect the rapid increase in temperature that occurs if charging continues beyond the voltage cut off, a decent charger should have provision for this.

It's possible that due to poor matching of the cells there is no clearly defined rise in voltage (dV/dT) from the pack as a whole at full charge, hence the charger just carries on.

I agree that higher discharge rates will decrease a batteries capacity. But a lot of the sub C cells were designed for high discharge rates and a lot of companies show graphs of the cell’s discharge characteristics at 20A or 30A. Some good cells even exceed their ratings at these high discharge rates.
I was expecting my cells to be a bit under what they were rated, but maybe by only 10%. The fact that the cells didn’t take over 4 hours to charge means there is no way it could have the capacity it claimed. No matter how low the discharge rate was.
On a brighter note, I charged my pack up a second time last night. The cells took over 3 hours of charge. So there is an improvement. Hopefully, it’ll keep getting better. Today, I made my 12km commute without running out to power. So at least they are usable

And I totally agree that nimh chargers should have a thermistor. My next charger will definitely have it.

 

[Ian]

I'm sure you are aware that NiMh cells take a few cycles to "run in" before reaching maximum capacity, so with luck they will do the job.

 

[jha07]

Looking around it does seem as if the sub-C cells offer the best high current discharge characteristics and favourable pricing. I am pretty sure this is because this size cell is popular for high-discharge applications, like power tools and RC models, so has been subject to a fair bit of product development.

In another life, I used high voltage NiCd packs in a demanding aerospace application. We found that trying to charge more than about ten cells in series was fraught with difficulty, due to the need to maintain all cells in the same state of charge. Discharging them in series, even with packs of 30 or more cells, works well, but if the cells get even slightly out of balance you can easily end up with problems in a big pack.

One simple solution is to arrange to discharge the cells in series, but charge each 12V sub-pack via it's own charger. Although slightly cumbersome, this does reduce the chance of damaging cells.

A better solution is to look at incorporating a battery management system to keep the cells in balance, or to buy accurately matched cells (this latter method is what the manufacturers of ebikes tend to do, I believe).

I'm seriously thinking of using 12V RC model sub-C packs, but if I do then I intend to build a relatively simple multi-pack charger to ensure reliability.

I use to race RC cars so I’ve had a lot of experience with sub C. It was long enough ago that we didn’t have NiMh, just NiCd. I also think that the RC industry has sped up sub C development over other cells. I remember draining a 1700mah pack in 4 mins. That’s over 25A average. Your average C or D cell user doesn’t need discharge rates nearly that high. So why would manufactures make them better if there is no need for it.

I was thinking about charging the pack in parts as you suggested. Maybe buy a 24V charger to charge a 48V pack, 20 cells at a time. I wonder if I get another 48V charger, one with a thermistor, if I will have the same problem with the charger not being able to detect the peak. I really don’t want to rely on the thermistor to stop the charger because it will probably be overcharging my pack every time.

By the way, that crappy charger of mine has failed to detect a peak on both 35 cell nimh, and 35 cell nicd packs. I read that nimh are more difficult for chargers to detect the peak, but nicd doesn't seem to be any better. Going to try 30 cells next just to test it.

 

[jha07]

May I suggest you read my post "Batteries from the USA" before dealing with these people.

I saw that tread. I know powerstream usually ship with UPS. And I know UPS charge a ton on brokerage fees to canada. They can use other methods of shipping, but you have to specify in writing on your order.
The other thing you mentioned, that they require a copy of your ID and debt card before releasing your shippment. I've never heard of any company needing that. Seems a bit odd to me. I guess they are just trying to prevent online fraud. I wouldn't mind doing that, as long as their product is decent.

 

[flecc]

I absolutely refused to do that with my credit card last time when they demanded it, so the transaction was cancelled. Since then another member has refused and they still let his order go through anyway.

I wouldn't copy your card in that way if I were you. It's not a matter of not trusting them, rather the fact that it would probably breach your credit card conditions. Then if you were subsequently caught by a fraud using your card number, the credit card company could refuse to indemnify you, leaving you to pick up the fraudulent amount, which could be very large.

It's a risk not worth taking.
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[jha07]

I absolutely refused to do that with my credit card last time when they demanded it, so the transaction was cancelled. Since then another member has refused and they still let his order go through anyway.

I wouldn't copy your card in that way if I were you. It's not a matter of not trusting them, rather the fact that it would probably breach your credit card conditions. Then if you were subsequently caught by a fraud using your card number, the credit card company could refuse to indemnify you, leaving you to pick up the fraudulent amount, which could be very large.

It's a risk not worth taking.
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That's a good point. But I'm just wondering what they could do with a copy of your credit card. Don't they already have all your credit card info from placing your order?

 

[flecc]

They do except for the signature, and with a dummy reproduced card, quite easily produced, that could be useful.

The problem though is one of less security. Where all the details given online are given in a secure environment, the emailed copy could easily be printed out, giving everything needed including the last three from the reverse for online ordering.

There's also the fact that emails are stored by ISPs for at least six months, another danger point over a long period of time.

Their demand is totally unreasonable. I offered them a screenshot of my account page from the credit card company website which I could only access with my user name, password and an item of personal information, showing their transaction, amongst several others, entered and credited to them in full. They refused that, saying I could have forged the entire page!

This shows how perverse they are being, since if I could forge a copy of an entire complex website page, I could even more easily forge a couple of credit card copies.

I'm still considering notifying Visa and Mastercard of their demand, since I'm sure that would earn them a very swift reprimand and penalty threats.
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