go_away

Author Topic: Home made battery-pack  (Read 1401 times)

0 Members and 1 Guest are viewing this topic.

Offline dellagdTopic starter

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 730
  • Helpful? 5
  • Come to the dark side... We have cookies!
Home made battery-pack
« on: June 30, 2010, 04:43:35 PM »
Hello All-

I am wanting to build a 6 volt rechargeable battery pack out of 5 , 1.2 volt standard rechargeable NiMH AA batteries.
I plan on attaching them all in a voltage tandem (voltage would be 1.2 x 5 battries and mAh is averaged between the 5 batteries. May main question in if I could simply solder a bare copper wire between the - and + ends of the batteries, ending up with one - and one + pole for all 5 batteries. It seems common sense that If I leave the soldering iron on the battery too long it would rupture (bad  :-X )

Any thoughts on how to do this?


On a side note, 4 of these batteries are Energizer and the other one is Duracell. They are all NiMH and the only differences are the brand and the Duracell is 300 mAh lower then the Energizer. Would the only side effects of this be dropping the average mAh from 2300 mAh (would be if all Energizer) to 2240 mAh (The 4 energizers and the duracell)
Innovation is a product of Failure, which leads to Success.

If I helped, +1 helpful pls

I Won!
3rd place! I'm taking $100

Offline SmAsH

  • Supreme Robot
  • *****
  • Posts: 3,959
  • Helpful? 75
  • SoR's Locale Electronics Nut.
Re: Home made battery-pack
« Reply #1 on: June 30, 2010, 04:47:27 PM »
Hmm, about the soldering. You are right in thinking that you could screw the batteries up by soldering them, its best to solder it in a quick go and not hold the iron on there for too long. As for the batteries, i would not suggest mixing batteries of different specs, somehow it does not seem too good... Is there anyway you can get another of the energizer?
Howdy

Offline dellagdTopic starter

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 730
  • Helpful? 5
  • Come to the dark side... We have cookies!
Re: Home made battery-pack
« Reply #2 on: June 30, 2010, 04:53:36 PM »
I guess I could, but I would have to buy another 4 (I dont see any 2 packs) and then chi ching goes the register... You get it. It is really not desirable. They are both NiMH? what could be bad?
Innovation is a product of Failure, which leads to Success.

If I helped, +1 helpful pls

I Won!
3rd place! I'm taking $100

Offline SmAsH

  • Supreme Robot
  • *****
  • Posts: 3,959
  • Helpful? 75
  • SoR's Locale Electronics Nut.
Re: Home made battery-pack
« Reply #3 on: June 30, 2010, 05:16:13 PM »
Well, if one battery is lower mah than the others, it will run out before the others then drain off them for the rest of their time. You COULD do it and it would work, its just that it would not work the best it could.
Howdy

Offline dellagdTopic starter

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 730
  • Helpful? 5
  • Come to the dark side... We have cookies!
Re: Home made battery-pack
« Reply #4 on: June 30, 2010, 05:24:46 PM »
it would not just do this?

Quote
Would the only side effects of this be dropping the average mAh from 2300 mAh (would be if all Energizer) to 2240 mAh (The 4 energizers and the duracell)
Innovation is a product of Failure, which leads to Success.

If I helped, +1 helpful pls

I Won!
3rd place! I'm taking $100

Offline Razor Concepts

  • Supreme Robot
  • *****
  • Posts: 1,856
  • Helpful? 53
Re: Home made battery-pack
« Reply #5 on: June 30, 2010, 07:23:06 PM »
Rechargable AAs are not designed to be soldered to, and soldering may damage the cells. I would reccomend just modifying a 6-aa battery holder.

Offline dellagdTopic starter

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 730
  • Helpful? 5
  • Come to the dark side... We have cookies!
Re: Home made battery-pack
« Reply #6 on: June 30, 2010, 07:36:06 PM »
well, I guess I should, besides doing the 6-AA holder pack idea, I could just electrical tape some metal onto it to connect the - and + terminals together.


New question:

would a 9v 350mA power adapter work fine to charge them? I would mod it to connect to the 6v battery pack.
Innovation is a product of Failure, which leads to Success.

If I helped, +1 helpful pls

I Won!
3rd place! I'm taking $100

Offline waltr

  • Supreme Robot
  • *****
  • Posts: 1,920
  • Helpful? 97
Re: Home made battery-pack
« Reply #7 on: June 30, 2010, 08:24:07 PM »
I agree with all the comments posted above. The cells must be matched to build a pack.

When I build packs I buy cells that have a tab welded on each end of the cells. The tabs are then easily and safely soldered together.

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Home made battery-pack
« Reply #8 on: June 30, 2010, 09:37:35 PM »
Hi,

They are both NiMH? what could be bad?
When the lower capacity battery runs out before the other cells and the circuit is still consuming, the weak battery will go toward 0V and continue to pole reversal, as the rest of the batteries in series with the load will be a charger of wrong polarity - draw it on paper if you cannot imagine it.

Some things just don't mix well, like drinking and driving, shoes and battery cells.


Cells should be spot welded if anything.


Your adapter can be made into a slow charger, but it will be... Slow.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline dellagdTopic starter

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 730
  • Helpful? 5
  • Come to the dark side... We have cookies!
Re: Home made battery-pack
« Reply #9 on: July 01, 2010, 05:07:33 AM »
point taken

thank you!
Innovation is a product of Failure, which leads to Success.

If I helped, +1 helpful pls

I Won!
3rd place! I'm taking $100

Offline Gertlex

  • Supreme Robot
  • *****
  • Posts: 742
  • Helpful? 23
  • Nuclear Engineer · Roboticist
Re: Home made battery-pack
« Reply #10 on: July 11, 2010, 04:11:22 PM »
I use a 6V supply with 5 NIMH rechargeables and copper wire + spring from a pen to join the terminals in the empty battery slot.  I remove the batteries for charging, though.  Don't have said pack with me, so I can't provide a pic.
I

 


Get Your Ad Here