do not buy from onlybatterypacks.com

[Admin]

I try to do my best to protect you guys from dishonest sellers by only listing trusted companies in the robot parts list. In this case, the seller has been marking up the specs much higher than they really are. I hope this saves you guys from the frustration of buying products that don't work!

My complaint email to onlybatterypacks.com is shown below. I also noticed the mAh is lower than they claim too, but I didn't do a full test on it so left that out:

Hi

I am the author of the popular site, societyofrobots.com.

I am a recent customer of this product:
http://www.onlybatterypacks.com/showitem.asp?ItemID=10417.7

You make a claim for a 35A discharge rate, however my own measurements say its much closer to a 3.5A discharge rate! Just by drawing 2A from a fully charged battery, I already get a 1V drop.


I also bought this product:
http://www.onlybatterypacks.com/showitem.asp?ItemID=11724.12

You make a claim that it can do 3000mah in 1.5 hours. However the above 4200mah takes ~5 hours to charge! The 1.8A selectable rate does not work - it claims the battery is fully charged (within 30 minutes) when it isnt! I have to use the .9A setting for it to work.

Either the battery has a charging rate of only 1A, or your charger has a serious flaw.

Now I can't recommend your site or products any longer on mine until this problem is rectified and I'm assured this won't happen again. I will also no longer be able to purchase your products, because I can't be sure if the specs are honest.

thanks,
John Palmisano

Robotics Specialist
Naval Research Laboratory, Washington, DC
B.S. Mech. Eng., Robotics, Carnegie Mellon University
www.societyofrobots.com

[pomprocker]

whew...luckily i purchased from allbattery.com (tenergy)

[pomprocker]

Robotics Specialist
Naval Research Laboratory, Washington, DC
B.S. Mech. Eng., Robotics, Carnegie Mellon University
www.societyofrobots.com

Nice resume....ahem signature.

[Admin]

Now that I think about it, I was really really dumb to believe those specs . . . all other things the saame, even lithium polymer batteries can't do 35A discharge!

I've bought tenergy AA NiMH's in the past, and they do as they claim

But let this be a lesson to all of us: companies specs can be wrong, so use your brain!

[JonHylands]

I use http://www.all-battery.com/ and I've been very happy with their batteries and chargers...

- Jon

[airman00]

I use http://www.all-battery.com/ and I've been very happy with their batteries and chargers...

- Jon

me too

everything is very cheap there and all the specs are accurate

[jman571]

Errrr....I WAS going to pruchase my batteries from www.all-battery.com until someone from this forum suggested this site in my thread asking for advice 

I have unfortunately purchased 2 products:

Admin's charger: http://www.onlybatterypacks.com/showitem.asp?ItemID=11724.12

and this battery: http://www.onlybatterypacks.com/showitem.asp?ItemID=11128.37

However, I have not recieved either yet, though I believe they've shipped already, and will be recieving them by this Friday.

What do you guys suggest? Should I send the whole thing right back to them? Or is this going to cost me more money than it's worth, at the very least I need about 2-3 A out of this battery, but i'm wary of this charger's abilities now.

[Admin]

sorry about that jman571 . . . I got burned really bad - the battery I got I need for my competition in 3 days, but its too weak to power the robot arms on my ERP

The arms require 2A peak . . . but drawing just that causes a voltage drop so large it resets my microcontroller . . .

Anyway, the battery you posted appears to have very realistic specs. I think you are fine on that. For the charger however, yea, you won't be able to get more than .9A charging rate. It will take about ~3 hours to recharge your batteries. I'll leave it up to you . . .

If you decide to keep the battery, I encourage you to multimeter it and see how low the voltage drops when you use it.

[jman571]

sorry about that jman571 . . . I got burned really bad - the battery I got I need for my competition in 3 days, but its too weak to power the robot arms on my ERP

The arms require 2A peak . . . but drawing just that causes a voltage drop so large it resets my microcontroller . . .

Anyway, the battery you posted appears to have very realistic specs. I think you are fine on that. For the charger however, yea, you won't be able to get more than .9A charging rate. It will take about ~3 hours to recharge your batteries. I'll leave it up to you . . .

If you decide to keep the battery, I encourage you to multimeter it and see how low the voltage drops when you use it.

Yea, I was just looking at allbattery, and they didn't really have what I was looking for. I'm sure my uncle (he's an electrician) has a multimeter, and I'm going over there anyways to do some soldering, so I'll let you guys know if my battery charger is messed up as well. Because if it is...*rubs hands in anticipation of consumer boycott*

[cooldog]

Robotics Specialist
Naval Research Laboratory, Washington, DC
B.S. Mech. Eng., Robotics, Carnegie Mellon University
www.societyofrobots.com

[/quote]

your signature is intimidating

"naval research lab"

[GHF]

To be honest, it's a terrible idea to expect a lot of current from NiMHs. They aren't exactly known for their superior current-delivering abilities.  That's why battlebots, which tend to draw amps in the hundreds, use big fat NiCds -- they're just irreplaceable when you want a durable, cheap, high-amperage battery. Also, battlebots people tend not to care about the environment or weight.

Also, the charger thing was more of an user error. NiMHs are best charged at C/10 (capacity over ten hours; the hours is just their to make the units work out), so in your case, about 4.2Ah/10hr = 0.42A. One of the symptoms of charging too fast is of course voltage spiking, causing false peak detection by the charger and then premature end of charge. Also, heat becomes an issue. The 3000 mAh battery in 1.5hours would be perfectly reasonable for a NiCd pack though -- NiCd has a endothermic charging process, and will thus cool itself off while charging. Plus, they just charge faster. Some "fast" or "quick" chargers actually go for 1C.

Anyways, high current capacity stuff should just be left to the lithiums. LiPo/LiIon provide a lot of energy density and a lot of current. Take a look through Tower Hobbies and the like, and you can find 30C discharge LiPos. However, they are much more finicky about voltages. Overcharge them a tiny bit and they explode. Undercharge them by 0.1V and they stop working (or explode). Drop them and they die (sometimes explode). Charge/discharge them too fast, and they explode. The 30C figure doesn't go together with the lifetime either; discharge them at that rate and you might only get a hundred or so cycles before hitting 60% capacity.

For a sumo robot, I used four A123 M1 cells (2300mAh, 70A capacity, approximate sub-C form factor, about $18/cell), which have begun to have legends circulating about their ruggedness. Cells unbalanced to 5.0V with no damage, discharge to 0.5V, etc. They also come it aluminum cylinders, so they're more durable than the foil pouches LiPos come in and lighter than steel-canned NiCds/NiMHs. http://www.flyelectric.ukgateway.net/lithium-a123.htm The most telling difference is this: these are used in power tools and electric cars, while lithiums are used in cell phones and iPods.

-Xo W.

[AndrewM]

Anyways, high current capacity stuff should just be left to the lithiums. LiPo/LiIon provide a lot of energy density and a lot of current. Take a look through Tower Hobbies and the like, and you can find 30C discharge LiPos. However, they are much more finicky about voltages. Overcharge them a tiny bit and they explode. Undercharge them by 0.1V and they stop working (or explode). Drop them and they die (sometimes explode). Charge/discharge them too fast, and they explode. The 30C figure doesn't go together with the lifetime either; discharge them at that rate and you might only get a hundred or so cycles before hitting 60% capacity.

Li-Mn batteries are a less volatile option with similar discharge and burst rates to NiCads and LiPos, but without the explosive results of LiPos.  But about 2X the price.  http://duralitebatteries.com/flight/batteries-mg.php#Electric

[superchiku]

li-ion rocks ....

[jman571]

Alright, I recieved my stuff, I'll keep you guys up-to-date on whether I have any problems. Though it might be some time before I "test" out all my components, as I realized I will need an additional connector, and some soldering to do as well.

[ALZ]

Hi:

I took a look at some of these places you have been buying batteries from. I hate to break it to you but those are some high prices you are paying! "www.all-battery.com"
wants $26 for a 14.4 Volts 2400 MAH battery. Then they want $14.99 for just a wall charger that can only put out 300 ma. and they called that a sale! Some of the other places you talk about even want more. Shop around guys. I can tell you that I didn't pay anything close to those prices. Also my charger has a base for the battery pack that cuts off if the battery overheats and it can put out 1.2 amps. I bought a few, so if any of you want to buy 1, let me know. BTW the battery pack (C cells) that comes with the charger is  14.4 Volts at 2400 MAH

I use http://www.all-battery.com/ and I've been very happy with their batteries and chargers...

- Jon

[airman00]

Hi:

I took a look at some of these places you have been buying batteries from. I hate to break it to you but those are some high prices you are paying! "www.all-battery.com"
wants $26 for a 14.4 Volts 2400 MAH battery. Then they want $14.99 for just a wall charger that can only put out 300 ma. and they called that a sale! Some of the other places you talk about even want more. Shop around guys. I can tell you that I didn't pay anything close to those prices. Also my charger has a base for the battery pack that cuts off if the battery overheats and it can put out 1.2 amps. I bought a few, so if any of you want to buy 1, let me know. BTW the battery pack (C cells) that comes with the charger is  14.4 Volts at 2400 MAH

care to tell us where you bought your batteries from?

[Trumpkin]

I paid $11 for my 2400mah 6volt battery from www.all-battery.com I think that's pretty dang cheap. please tell us where you bought your batterys.

[superchiku]

plzz tell iam in  process of buying my battery so it would be good if u can

[pomprocker]

I paid $11 for my 2400mah 6volt battery from www.all-battery.com I think that's pretty dang cheap. please tell us where you bought your batterys.

so did i. that was a sale price.

[superchiku]

easy for u to say, i ordered my battery pack adn charger from the site all-battery pack , it was good only 40$ fro both i proceed to checkout and what do i see international shipments cost is around 60$ what a waste is this economical ordering batteries for 100 $ , better do without the batteries doesnt anyone give free samples??

[pomprocker]

easy for u to say, i ordered my battery pack adn charger from the site all-battery pack , it was good only 40$ fro both i proceed to checkout and what do i see international shipments cost is around 60$ what a waste is this economical ordering batteries for 100 $ , better do without the batteries doesnt anyone give free samples??

Yeah I think my total was $44 for battery, charger, and shipping.

[Trumpkin]

I just used an adapter thingy for my charger. (it was free)

[superchiku]

Yeah I think my total was $44 for battery, charger, and shipping.

with shipping how come ? was it overseas

and trumpkin

I just used an adapter thingy for my charger. (it was free)

what kinda charger??

[ALZ]

Hi Guys:

I got them on Ebay a few months ago. The company was selling off all the Lentek robotic vacs and parts. All the parts were new, some of the vac were lightly use, others new.   The shipping cost much more than the parts but still a great deal. So when the bids were low I picked up a battery here and there along with a vac. Then they listed a box of 12 chargers. No one wanted that many so I got them cheap.  The transformer part that plugs into the wall is really a DC power supply that gives 24 V at over 1 A. That plugs into a base that looks like it has some kind of switcher power supply in it.  If you are looking for NiMH AA cells "www.mcminone.com" sells them for 99 cents each. Like I said you just have to look around a bit.

I paid $11 for my 2400mah 6volt battery from www.all-battery.com I think that's pretty dang cheap. please tell us where you bought your batterys.

[Trumpkin]

Ummm...so it's not such a great deal. I think we all know that you can get NiMH AA cells, but who wants to go through the trouble of soldering them all together then getting a molex connector kit and putting the molex connector on the wires. It isn't worth the trouble and in the end it ends up costing pretty much the same. You can get 12 hitec male molex connectors for $8 and if you want a 4 cell battery pack and each cell is 99 cents that's ~$4 if the connectors are $8 that's $12 plus shipping and you have to do extra work!!!! I would feel uneasy buying batterys and stuff on ebay for some reason.....
 

[ALZ]

Hi: Why in the world would you want to wired the cells together & pay $8 for a connector!
4 cell battery holder with connector, 78 cents from Jameco.   

Ummm...so it's not such a great deal. I think we all know that you can get NiMH AA cells, but who wants to go through the trouble of soldering them all together then getting a molex connector kit and putting the molex connector on the wires. It isn't worth the trouble and in the end it ends up costing pretty much the same. You can get 12 hitec male molex connectors for $8 and if you want a 4 cell battery pack and each cell is 99 cents that's ~$4 if the connectors are $8 that's $12 plus shipping and you have to do extra work!!!! I would feel uneasy buying batterys and stuff on ebay for some reason.....
 

[Trumpkin]

I couldn't find a battery holder with the molex connector on jameco.

[ALZ]

Hi: I didn't say the connector was a "molex" connector. My point was that you don't have to spend the time soldering and tapeing cells together to make a battery pack when you can buy a battery holder at low cost. 

Yes, when you buy on Ebay you should use some sense. If you can try looking for a comany that is dumping lots of the same item, this way you can buy one and see if it meets your needs. Also this way you can buy only when the bid is low. The most the 14.4 V packs cost me was $5 for S/H and $2 for the battery pack; many of them only cost me 99 cents.   

I couldn't find a battery holder with the molex connector on jameco.

[Admin]

It appears that the charger they shipped is bad and not the batteries.

They told me that the charger is bad and to ship it back. I suspect they whole product line was bad . . .

jman571, your post:
http://www.societyofrobots.com/robotforum/index.php?topic=3173.msg31171#msg31171

suggests they have made a replacement recently to a new type of charger . . .

I'm going to mail back the charger, try the replacement, and see how things go.

[Admin]

An update on the saga . . .

They *finally* tested the charger this morning and told me it was working fine.

I guess then maybe its the battery, so I'll be shipping that back soon for them to test . . .

arggghhhhhhh