Let's Make Robots!

Battery chargers

Hello,  just to know what kind of battery chargers do you use ? any advice on what to buy ?

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Three advices:

1) Get many batteries, and get many of the same kind

2) Get batteries with as many MhA's as possible

3) Get 2 rechargers, or another setup, so you can charge at least 8 at a time

That will make you happy!

Heres my advise on top of frits

 

Dont listen to frits about hardware :p

 

NIMH batteries are now cheaper and have one of the highest power densities (LiPo-Lion-NIMH-NIcad-Alkaline-Lead Acid)

Put out a lot of current as compared to size and new NIMH technologies allow for batteries to be able to draw 30+ amps at a time

Get battery holder, not necessarily premade packs. This allows you to reconfigure your batteries. I myself have about 40 NIMH batteries :)

You can put tape over battery holders if it makes you feel better.

You can take the batteries out that you put in. THis also allows you to buy a cheap wall charger too.

uhm that sounds nice..

Today i casually visited a local shop of RC radio and modelism and i found they also sell many batteries! yay! :)

They have NIMH pack with 7 V (7.3 iirc) and also some lead 12V square batteries that looks almost like scooter batteries but a bit smaller, they came for 20€ which is not bad, and 19€ for the charger. I was almost sure to buy it before i read your post :P I'll go again on monday and ask some more info.. 

Btw they have some fine goodies, such as a great choice of servo, some remote controller, motors (no geared asfar as i saw) some ubercool RC elicopter (for 400€ ),RC fuel powered cars, etc etc. I definitely return to take a second look :)

You want NIMH batteries, they hold more charge, are not affected from memory effect and current technologies can surpast the current outputs of NICaD batteries.

Another advantage of rechargables is that 4 of them gives 4.8V, whereas 4 alkalines gives 6V. Also, where alkalines tend to slowly drop in voltage, rechargables tend to maintain their voltage unti the stop alltogether!

I know this is true of NiCds. Can anyone confirm the voltage /discharge curve for NiMH?

A major disadvantages can be seen when you make a mistake. If you short circuit a NiCd, your wires heat up and the insulation melts and it frightens you half to death.

I'm too yeller to use rechargables, so I use el-cheapo alkalines.

There are two exceptions. I once found a cheap source of 7.2V Tamiya racing packs which are NiCd. The other is that I use a lead acid batttery with Big Chaser.

well i'm using 4 standard rechargeable AA batteries for my current robot (that eats 5V), but the next one will require 12V. I've seen a NiMH battery pack on many sites that come for around 25 €, but the recharger alone costs 70 €! I was even considering a scooter battery (as you can read in the shoutbox), since my new robot would be quite big anyway. It costs like hell but at least should provide plenty of energy :) Btw, can i just connect one of those to say, arduino? It requires 12V just like the batteries, but maybe the amperage will kill the board?

So many doubts, so few certainties :)

Amperage won't kill the board. The board will only draw the current it needs. Voltage will kill the board. I don't know what the standard drive voltage for arduino is, but If it's 5V, you'll need a 7805 regulator. Be aware that I separated my motorcycle battery from my MCU and run the MCU off a seperate battery as the power drain on the battery when the motors were starting up was resetting te PIC.

My battery cost $40 and the charger was $10.

Ask questions. Don't fry your hardware. Unless you're a cousin of Frits.

Yup, the Arduino board (at least the Diecimilla) has an onboard voltage regulator, so you can feed it anywhere between 7-12v comfortably. It should be fine from a motorcycle battery, but as BoA says, if you're powering big motor with the battery too, they may cause it to sag enough to cause your Arduino to reset. You can stick a capacitor across its input leads to help minimize that problem, or just stick it on a smaller separate battery to be sure it won't affect you.

Dan

Not on the inputs. If you put it on the input (even physicall close to the input) then a rapid switch on of your motor will still draw from the cap. You need a bit cap on the 5V side of the regulator. The board might already include on. I'm fascianted by the notion of a cap on teh 12V side (I've seen it on the data sheet for the 7805) but I don't see why ot would work...

...can anyone help?