Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Vexelius on November 23, 2011, 07:28:53 PM

Title: Some questions regarding LiPo Batteries
Post by: Vexelius on November 23, 2011, 07:28:53 PM: Hello, everyone!

It's my first time posting in this forum, though I have lurked the website for a very long time and it has helped me a lot in the past.

So... I decided it was time to register. For my first post, I have some questions regarding LiPo Batteries. It's my first time using them as the power supply of a robot, and I want to "play safe". (Especially after watching some videos of exploding batteries)

(https://lh5.googleusercontent.com/-1vSnLi9UjGQ/Ts2ZKbw--zI/AAAAAAAAALE/S95VvgNwqZc/s400/IMG_20111123_190004.jpg)

In the picture above, you can see the battery that I'll be using, as well as its balance charger. I haven't tested them yet, as I'm having some trouble locating a 12V, 1.5A power supply but I'll get one tomorrow morning.

Question #1: Should I have any special caution to attach them to my robot chassis? So far, I have used adhesive tape to attach my battery packs, but I want to know if I can do the same with these.

Question #2: I have never seen a plug like this one. How can I connect it to my circuit board? From what I have read, the "pin friendly" connector should only be used to charge the battery, and the long ones are the ones that power the RC model.

(https://lh4.googleusercontent.com/-57OCDXIc40E/Ts2Y9Hw66eI/AAAAAAAAAK8/bZ-42h0TcDo/s640/IMG_20111123_190023.jpg)

Question #3: Should I use a special circuit with this kind of battery? Usually, I design a "Power module" when working with 9V/AA batteries, with a couple of inductors, a 7805 and some capacitors. I don't know if I can do the same with LiPo batteries, or if I need some additional components.

Thank you very much in advance. Any additional words of caution or suggestions will be appreciated.
Title: Re: Some questions regarding LiPo Batteries
Post by: rbtying on November 23, 2011, 08:03:23 PM: Those aren't plugs--they're just heatshrink over thick wire. You'll need to solder your own plugs, or use a screw terminal.
Title: Re: Some questions regarding LiPo Batteries
Post by: Soeren on November 23, 2011, 08:07:36 PM: Hi,

Quote from: Vexelius on November 23, 2011, 07:28:53 PM
Question #1: Should I have any special caution to attach them to my robot chassis? So far, I have used adhesive tape to attach my battery packs, but I want to know if I can do the same with these.
As long as it's strong enough to hold it and you don't pierce the battery cells in any way, you should be fine. Velcro will let you remove and reattach the battery in a second, but there's a huge difference on the holding force of different "Velcro's".
3M makes a super strong one where both halves are the same material contrary to the hook and loop of ordinary Velcro.

Quote from: Vexelius on November 23, 2011, 07:28:53 PM
Question #2: I have never seen a plug like this one. How can I connect it to my circuit board? From what I have read, the "pin friendly" connector should only be used to charge the battery, and the long ones are the ones that power the RC model.
Neither have I
Are you referring to the black something or the one looking like rolled up paper?

Any chance of a better photo, preferabley from the end as well - it looks like someone just put heat shrink sleaving on a connector (or a thicker part of a wire).

Quote from: Vexelius on November 23, 2011, 07:28:53 PM
Question #3: Should I use a special circuit with this kind of battery? Usually, I design a "Power module" when working with 9V/AA batteries, with a couple of inductors, a 7805 and some capacitors. I don't know if I can do the same with LiPo batteries, or if I need some additional components.
Why do you use inductors there?
If you just want o regulate down a bit, a voltage regulator and 2 caps should do and since a battery is the most noise free supply we have, there's no need forinductors (they may even be bad, if you hit certain resonance frequencies).

LC filters are best used at the motor supply part, to keep motor noise from getting into your logic (no matter the battery chemistry).
Title: Re: Some questions regarding LiPo Batteries
Post by: Vexelius on November 23, 2011, 11:42:25 PM: Quote from: rbtying on November 23, 2011, 08:03:23 PM
Those aren't plugs--they're just heatshrink over thick wire. You'll need to solder your own plugs, or use a screw terminal.

Thanks for your answer. As you have pointed out, it's just a piece of heatshrink... I thought something like that after looking at the battery for the first time, but as I'm new to using LiPo, I thought that maybe, it could be some kind of connector I haven't seen before.

Anyways, do you think banana plugs be OK for this battery?

Quote
Why do you use inductors there?
If you just want o regulate down a bit, a voltage regulator and 2 caps should do and since a battery is the most noise free supply we have, there's no need forinductors (they may even be bad, if you hit certain resonance frequencies).

Yeah, thanks for correcting me there. When I thought on "Power module", my mind instantly recalled the schematic for an AC/DC power supply, where these are actually used. ;)
Title: Re: Some questions regarding LiPo Batteries
Post by: Soeren on November 28, 2011, 05:32:31 PM: Hi,

Quote from: Vexelius on November 23, 2011, 11:42:25 PM
[...] do you think banana plugs be OK for this battery?
OK in the sense of current capability, yes, but...
Using loose male plugs on a battery is asking for a short, which is very bad (and I mean really bad) with lithium cells.
Even a two pin male plug is chancing it.

There's a rule of thumb about using male plugs where somethings go out of them and female plugs where something goes in (I shall refrain from commenting on what kind of analogy has led to that ;)).
HOWEVER... When you talk power supplies, the exact opposite holds true, and a two (or more) pin female connector should go on the battery, so they don't accidentally short and start a fire.

For the modest current you're going to draw, any size of R/C battery connectors will do.
Title: Re: Some questions regarding LiPo Batteries
Post by: Gertlex on December 02, 2011, 02:58:58 PM: A common connector used with Lipos are the Deans connectors, AKA T-Connectors. And you ALWAYS put a female connector on the battery.

See e.g. here: http://www.amazon.com/Nylon-T-Connectors-Pairs-Male-Female/dp/B005D5PMLO/ref=sr_1_3?ie=UTF8&qid=1322859494&sr=8-3 (http://www.amazon.com/Nylon-T-Connectors-Pairs-Male-Female/dp/B005D5PMLO/ref=sr_1_3?ie=UTF8&qid=1322859494&sr=8-3)

You'll want to solder one wire on at a time, then cover it in tape/heat shrink, then solder the other wire. You're risking a short if you don't do it this way. You can heat shrink both wires individually, or epoxy the final result.