Tenergy NiCad SubC's Report

[safe]

Tenergy NiCad SubC's Report

Just thought I'd report on my Solderless Tubes using Tenergy SubC NiCads.

First, the Solderless Tubes work great and franky I've not had any problems with them. It puzzles me why people haven't done this all along. The secret is the combination of screw and spring combined with the use of copper to make the electrical connections.

The NiCad SubC's are rated as 10C and I can disconnect my SLA's and test them at that rate and they seem able to deliver that for a while. When you do that they heat up. I normally run the SLA's in parallel with the SubC's and so the "C" rate is more like 3-4 "C" so they never get warm during use. So far the cells I'm testing are all charging and discharging successfully and the starting and ending voltage is more or less balanced for each set.

The only unexpected thing I've found is that the self discharge rate seems pretty high. I'm finding that you lose a lot more than the standard 1% per day and are losing more like 5% or more like 10% in a day, at least the first day. I've found that I can usually top off the cells a little with an extra five minutes of charge to get that last bit of extra before riding.

Long term testing will take... well... time... but I've used them for about 200-300 miles so far and they seem okay.

If you want to consider a low priced alternative to the other battery options you might look into:

http://cgi.ebay.com/96-NiCd-Sub-C-2400mAh-Batteries-for-PowerTools-Flat-Top_W0QQitemZ330198582341QQihZ014QQcategoryZ40975QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

Dirty_D:

If you manage to see this, maybe you could post what your performance has been with these cells since I know you bought a batch too.

The nice thing about Solderless Tubes and Nicads is that there's nothing that can easily break and you don't need all the Balancing, LVC and other assorted BMS hardware. NiCads are pretty durable it seems and the high "C" rates of the SubC's allow for more freedom in their use. I'd still suggest running any battery at below their maximum because all things prefer to be run in moderation and not excess.

 

[Tom_D]

Hey Safe,
Can you tell us how you have them configured and how you charge them ?

I know that without a thermal switch, you can cook these.

--Tom_D

 

[safe]

Can you tell us how you have them configured and how you charge them? I know that without a thermal switch, you can cook these.

My tubes are 12 volts and two together make up a set at 24 volts which then has a Dean Connector. I then use wiring to create the 48 volt series and parallel configuration for the bike for runtime.

But as far as charging it's a simple 24 volts.

I'm using the Tenergy 24 volt and 1.5 Amp charger and I also watch them pretty carefully. So far they have worked great. You might know that NiCads show a much more pronounced Delta V signal than NiMhs so the charger seems to never have a problem seeing it. In fact, I'm able to completely charge a set and then disconnect and five minutes later run it again for a "top off" and the charger still is able to correctly see the termination signal. Whatever they are doing it seems to be very good. However, I will say that in some cases the chargers are TOO sensitive and will cut off early. I call this a "burp" and it happens when the set is completely cold. Seems that when the beginning charge starts it warms things up rapidly at first internally and then eases and the charger can mistake this as a need to cutoff. You can prevent this by heating the sets up a little by riding around at 10C for a bit. It's never a problem if you ride, then go right to the charger because the cells are already warm. Also, once this happens once it doesn't do it again, so you can get a full charge once you restart it.

This is what I do:

1. Start the chargers.

2. Come back about half way to when they are supposed to be done and check to see everything is okay.

3. If one claims to be "done" I check by feel to see if the set is at all warm, if not I don't believe it and restart the charger.

4. After the expected time is finished I check to make sure that everything turned out okay and that all the sets ended warm.

5. I check the voltage as a final validation.

Tenergy Chargers are what might be called "hyper sensitive" so the chances of missing the Delta V with NiCads is very slim. (NiMh might be a different matter)

 

[Ypedal]

6- Plan on buying better quality chargers

 

[safe]

6- Plan on buying better quality chargers

I'd rather have chargers that are "too sensitive" than the opposite. If a charger were not very sensitive and missed the Delta V then you run the risk of overheating the cells. With a "hyper sensitive" Delta V trigger you never run the risk of overheating your cells. They actually include a temperature probe with the chargers, but I just don't see the need for it given the highly sensitive Delta V trigger.

It's better to err on the side of caution... so I'm happy with these "safe" chargers. :wink:

(it's not such a big deal to have to restart a charger now and again... )

 

[Ypedal]

It's got nothing to do with them being " sensitive " .. it's called " inexpensively built " to be nice about it.

 

[safe]

Delta V

Delta V is Delta V...

Either a charger is sensitive enough to sense it or not. The biggest fear is that you get a charger with an insensitive Delta V measurement ability and you miss it and the charger overheats your cells.

The only way to avoid the "burp" is to have a charger with some sort of computerized logic to it that would be able to see the early "burp" and be able to say: "Hey, this is too early to stop... I think the charging should continue." For that kind of more advanced logic you pay more money. If the whole idea of batteries is price (which is why you choose something like NiCads) then if you spend all this extra money on more sophisticated chargers then you are throwing away the low cost idea that got you here in the first place.

That would be stupid!

If you start with an idea of "low priced energy source" then you need to stay consistent throughout the process and be faithful to the principle. These Tenergy chargers are inexpensive ($20) and they are "safe" to operate. If I spent lot's of money on the chargers then that defeats the whole purpose of this low priced system.

As Bill Clinton once said:

"It's the economy stupid."

 

[ebinary]

Tenergy NiCad SubC's Report

So NiCads are what, half the energy density of NiMH? What about the infamous "memory" problems of NiCd - has that been solved?

Where did you get your solderless tubes? Right before I bought my dewalts, I had a big order of NiMh and solderless tubes in hand, and decided to return them. Seemed like a great way to change out individual cells and manually balance if necessary.

 

[julesa]

So NiCads are what, half the energy density of NiMH? What about the infamous "memory" problems of NiCd - has that been solved?

NiCd energy density is still quite a bit better than SLA, and NiCd lifespan is much better than either SLA or NiMH. NiCd "memory" was almost all hype. It was never really a problem except to the marketing departments of NiCd sellers, read all about it if you're interested:
http://www.dansdata.com/gz011.htm
http://www.batterybook.com/WHAT IS MEMORY EFFECT.htm

The biggest problem with NiCd in my mind is cadmium toxicity, but as long as they're recycled properly that's not much of an issue either. NiCd is probably the most economical battery choice when you factor in lifespan.

The inexpensive LiFePO4 (Ping, Headway, Thundersky) might match NiCd's economy, if the claimed lifespan for LiFePO4 turns out to be true. The higher energy density and low toxicity make that a very attractive option. But NiCd is tried and true...

 

[docnjoj]

Agree about Nicads! Ive got some 5 amp Sanyos that still give 4 amp/hrs at 4C ater 6 years of intermittant use! Good choice, Safe!
otherDoc

 

[ebinary]

Agree about Nicads! Ive got some 5 amp Sanyos that still give 4 amp/hrs at 4C ater 6 years of intermittant use! Good choice, Safe!
otherDoc

Self-discharge of NiCds, NiMh and SLA is the other annoyance. I have started using the new low-self-discharge NiMh cells (eneloop, hybrio) at home for all things electronic. It's so nice to pick up a battery out of the drawer and have it be ready to go.

I wonder when that tech will migrate to sub-Cs for our biking benefit?

 

[safe]

Where did you get your solderless tubes?

I made them with PVC pipe, a screw fitting on one end and a regular cap on the other. The screw side also has a spring and the contacts were copper so the conductivity is very good.

As for the self discharge... yeah, that's an issue.

This morning I had to "top off" my NiCad's for about 5-10 minutes in order to have a full charge. They had dropped all the way down to a resting voltage of 26 volts. Right out of a recharge they are at 28 volts and after about an hour they drop to 27 volts. It's probably not actually all that much energy that is lost, but the lower starting voltage is just annoying. Also, the temperature seems to matter... of course that's true for all batteries.

"Memory" is how people rationalize their batteries poor performance. The only valid case was for satellites where the exact same charge was repeated again and again. Unless you can repeat the exact same partial usage with precision again and again there is no "memory effect".

Realistically, however, 'memory' CANNOT exist if ANY ONE of the following conditions holds:

Batteries achieve full overcharge.
Discharge is not exactly the same each cycle - plus or minus 2-3%
Discharge is to less than 1.0 volt per cell.

Remember, the existence of any ONE of these conditions eliminates the possibility of 'memory'.

http://www.repairfaq.org/ELE/F_NiCd_Battery.html#NICDBATTERY_014

 

[ebinary]

NiCd "memory" was almost all hype. It was never really a problem except to the marketing departments of NiCd sellers

Hmm, well there are still some baaaad chargers or cells out there then. I've had lots of cordless phones and screwdrivers (expensive and cheap) fail to hold a charge at some point, and the one thing they've all had in common was NiCads. The most recent was a set of solar lights which are fully charged and discharged daily.

I've often replaced the NiCads with NiMh in the same application and charger, and they've worked indefinately from that point on.

Maybe NiCad cells are more likely to swap polarity and ruin a pack (or is that a myth too)? Bottom line, I've probably owned 500 indivudual rechargable cells of all varieties over my lifetime, and I've never trusted NiCads. And its all due to personal experience (with marketing to add a name for it: memory).

 

[TylerDurden]

"Memory" is how people rationalize their batteries poor performance. The only valid case was for satellites where the exact same charge was repeated again and again. Unless you can repeat the exact same partial usage with precision again and again there is no "memory effect.

Wrongo-bucko... (as if you knew jack-shyte about anything).

Memory-effect occurs unless full discharges are periodically implemented to eliminate the crystals. Ask any walkie-talkie repair service or broadcast camera operator.

How to restore and prolong nickel-based batteries
Crystalline formation is most pronounced if a nickel-based battery is left in the charger for days, or if repeatedly recharged without a periodic full discharge. Since most applications do not use all energy before recharge, a periodic discharge to 1 volt per cell (known as exercise) is essential to prevent memory.

 

[jha07]

My Tenergy NiMh SubC are at about 150 cycles and seem to have lost a lot in performance. I just noticed today that the heatshrink on one cell is splitting from excessive heat. Maybe it's just one bad cell, but I feel like the drop in performance is greater than what I would experience from one bad cell. I'm going to rip the pack apart and see if there are more bad cells.
Hopefully, your NiCd are tougher than my NiMh.

 

[ebinary]

Where did you get your solderless tubes?

I made them with PVC pipe, a screw fitting on one end and a regular cap on the other. The screw side also has a spring and the contacts were copper so the conductivity is very good.

Cool - post some pics!

 

[D-Man]

How about some real data like actual measurements of capacity? A simple load test measuring amps and a stop watch would be a nice low budget test.

 

[safe]

This picture should pretty much explain the whole idea of how to build Solderless Tubes. There are two thicknesses for PVC and I'm using the thinner version. They are 3/4" tubes. The copper connectors are roughly the same size as pre-1982 pure copper pennies, though it would be illegal to deface American currency. :wink:

The springs are #96 from ACE Hardware and cost 75 cents each...

 

[Ben]

How do you think these cells would handle a high drain application like the r/c bikes that are starting to pop up now?

I think their rating works out to be something like 8C, but do you reckon they would have any chance of providing that kind of current?

 

[safe]

I think their rating works out to be something like 8C, but do you reckon they would have any chance of providing that kind of current?

I run my bike with 18Ah SLA's in parallel with two strings of 2.4Ah NiCads in these tubes. So normally the NiCads mostly prevent the SLA's from sagging, but a good chunk of the energy is still coming from the SLA's. However, I have tried disconnecting the SLA's and riding with just the NiCads and since my controller is 40 amps:

40 / (2 * 2.4) = 6.95 "C".

...and it does work. Obviously the range is short doing this and my main reason to do it is to drain the last out of the NiCads before doing a recharge. (I was worried about the "memory effect" which turns out to be less of a problem than some seem to think)

The problem with these extreme "C" rates is that the batteries get hot... really hot. The higher the "C" rate then the higher your batteries will heat and heat means shortened lifespan, so doing that is degrading your batteries. But it certainly can be done.

Realistically if you want to keep these NiCads cool you want to run them at about three or four "C" and that's about it. That's what I'm doing... no sense in risking it.

 

[Ypedal]

What the hell man ?

First of all.. the nicads will sag in voltage way more than the SLA...

2nd.. if the cells are getting WAY HOT during discharge, you are exceeding their rated " C " cabability..

3rd.. your concept of Memory effect has no place in ebike use.. forget that allready..

4th.. pushing high amps thru the cells to warm them up before a charge = not the way to do it.

This has got to stop........ .............

 

[Toorbough ULL-Zeveigh]

This has got to stop........ .............

yeah, I no what you mean.
It *would* be rather entertaining watching this trainwreck build a head of steam.
If it weren't for the fact that his dispensing bad advice will screw up a lot of people reading this for years to come.

Draining the last drop out of the battery on discharge added to the practice of "top off" on charge is burning the candle at both ends.
That will indeed wring out the maximum amp-hours from the cell, (the miniscule difference such that it is), at an enormous cost to lifespan.
However, since the cells are cheap & as long as you're aware of the tradeoff going in, that's a personal judgment call if it's worth it.

After all, the R/C racers do it all the time cuz pushing the limit is what it takes to win & they're perfectly happy with getting 25-50 cycles out of a pack.
They're forced to do it out of necessity, partly due to physical limits of available space but basically it's imposed by the race rules.
If you really hate to lose that last volt then just add one more cell to each string already & quit abusing your pack.

 

[safe]

First of all.. the nicads will sag in voltage way more than the SLA...

My SLA's start at 13.1 volts and so when you multiply them together you get 52.4 volts.

My NiCad's start at 27.0+ volts and so when you multiply them together you get 54.0 volts.

The first part of the ride will mostly just balance the two chemistries as the higher NiCad voltage will settle down into the lower.

Experience... actually riding the bike... shows me that the behavior works like this:

...it might fit what you want to believe, but I know from riding it that it works this way. SLA's tend to "sag" from the start and NiCad's "sag" in a flat manner. I suspect that the initial "sag" of the NiCad's might be proportionally different than the SLA's, but experience is experience what can I say. The bike goes with full power for about 15 miles and then starts to drop off rapidly. The maximum range of the combined batteries is about 20-22 miles. (beyond that and the cells are drained)

I don't drain the cells for memory reasons anymore... I tried that just for testing purposes. And topping can help because my chargers sometimes cut out early. Normally it takes about 5 minutes to top off, but I had a string that needed like half an hour to finish because the charger had cut off early. I just stay nearby and make sure they never get warm. (I touch the tubes during the top off)

Heat kills batteries... I try to keep the heat down and the best way you do that is to run at low "C" rates which is what I do. So I'm doing everything the right way.

Ironically the need for "topping of" is because of my use of low "C" rates. The chargers start with a completely cold battery and as the power enters it heats the cells slightly and then they cool and that's what triggers the false finish... the so called "burp". So it's because I'm running completely cold cells that I'm needing to compensate with an extra top off step.

"Cheap" is normally not "simple". :lol:

("cheap" means you have to adapt to it's "quirks")

And I have to add that this whole SLA/NiCad test is just something to do while I'm fiberglassing and welding and all the other stuff I'm doing to get the other bikes done.

 

[Ypedal]

Instead of testing by " Feel " and " Intuition " .. i test with equipment ! like a CA meter for example !!! Please do yourself and all of us a favor and invest in one ! ( or at least a Doc Wattson )

 

[safe]

Please do yourself and all of us a favor and invest in one!

Sensors of all kinds are nice to have. I have a multimeter. One day I'll throw some more money into one of these onboard meters.

After all... the old ebike saying...

"He who spends the most money wins." :?

($50 is more than the batteries for the test :lol: )

It's just that I'm trying not to waste money... and at this point the extra step of another meter seems like a frill. You can figure out what is going on pretty easily without one.

My current decision:

Buy an onboard meter

...or:

Buy another gallon of fiberglass resin.

...for me the resin takes a higher priority. ($35+)