LVC/LVA for a 1 Cell LiPo?
 

Hey guys, I have a quick question.

Since I'm making a USB charger, I was thinking of using a single cell lipo, over 2 or 4 double A's.

Using a single cell lipo to power a USB charger directly would surely be moe efficient an last longer than standard AAs.

Now if I DO use a single cell, is there any way I can mod, or pick up a LVC, afterall, I don't want something smoking on me during class, nor so I want a puffed lipo in class! :lol:

Any help/suggestions/advice would be appreciated!

Shaz-zam:

http://www.batteryjunction.com/prcimopcbfor.html

Wow, didn't see that.
But what the hell do I do with that :neutral:

Is this USB charger for powering your laptop? If so, why not use A123 cells? You could buy a 15Ah prismatic for $37 + shipping and that could go in your bag with a few heat shrink layers on it for protection, or even some stiff rigid plate for added security?

Not a laptop charger, but rather a USB charger for little things, like my phone, iPod, etc...

That PCB is wired between the LiPo battery and the device, and it acts as a voltage/amperage traffic cop, stopping the LiPo from over-discharging or doing exactly what you don't want it to do.

If you take apart certain Lithium batteries for things like cell-phones and audio-devices, you almost always see a similar PCB wired to the battery to keep it from over-discharging or over-charging.

The PCB linked to above is EXACTLY what you need.

I meant more along the lines of what to solder it to (Positive to ?, Negative, etc.)

It will come with instructions, but it is pretty self-explanatory...

http://ep.yimg.com/ca/I/theshoreline..._2106_58772718
http://lib.store.yahoo.net/lib/thesh....7vpcb8.5A.jpg

So I would assume, the left, bigger pad is for the positive, right side is for the negative side, what's the middle for? Just a different cable to charge?

If it's THAT simple, I'll definitely be trying this out..

Remember, it is used to make sure the battery is not over-charged, or over-discharged...so, that's why there are three pads. Two are positive (+) and one is a common ground/negative (-).

The circuit lies between the negative batt and negative load&charge, both the batt + and load + are connected to the same contact point.

Ah, but my real question is where are the polarities, and such?

Is the far left both positive and the right is the ground?

The top part of the diagram is your battery, the bottom part is the wires going to your charger circuit. B+ is battery positive, and so on.

Okay, so the B+ is battery positive, B-, battery negative, P+/- is...

yeah, I'm dumb.

The wires going to the charger circuit.

Oh, okay, so it'd just be like a standard 2s lipo.

As in, I have one set of wires (let's say JST for now, smaller ones), that go to the USB charger.
then I have another set of wires, to plug into my charger to recharge?

Would there be any way to keep one set of wires, since it'd take less room in the little Altoids tin I'm keeping everything in.

If not, I guess I could go with two sets.

You have the battery going into B+ and B- then you have the P+ and P- connected to the JST plug, which you plug into the MintyBoost, and also use to charge the lipo, you only need the one JST plug.

Look at your RC lipo packs, you have a deans, bullets, etc. on there and use it to charge and discharge the pack. Same thing here.

AHHHH
Now I think I've got it!

So, pretty much, this:
http://i53.photobucket.com/albums/g6...PCMDiagram.png

The load is the item you are charging ( charger side of the circuit ), the battery will be the power supply ( a single lipo cell to power the charger ).

Seems like alot of extra complication when you can just buy plug-in usb chargers that take a 9v battery for example, or a lithium cell built into the case for an iPhone to extend its air-time...

Ahh, but what's the fun in that!? :party:

Don't take me wrong, I have about 2 or 3 iPod/iPhone chargers, prebuilt, it just seems... too easy...

I mean, I like easy, but making stuff makes me take pride in it! :tongue:
Besides, people are buying my chargers off me like a fat kid and cake. :whistle:

EDIT: but anyways, the diagram is correct...right?
Of course, I'm gonna try making the simple way (board and AA's), then order the PCB, and another lipo w/ one built in, and switch off..
Hehe, looks kinda like a bomb in class. :lol::lol:

I am pretty sure you have it wired wrong there Chadworkz. I might be reading which contacts are for which labels, but I think the batt and load have a common ground or negative.

God, now I am so confused.

Isn't that exactly the same as the diagram above though?
It has the same common ground, just that circle load is.. uh..

Chadworkz diagram is correct, the one zeropointbug drew is the same but drawn a bit differently. They are both right.

Chadworkz diagram is the websites diagram-

So, just making sure, for the umpteenth time, the diagram I drew is fine?
Just thinking everything in my head on how I'm gonna do it. :X

No the diagram you drew is wrong, the JST connector needs to be across the 2 left-most pads, the battery connection is correct though.

Across, as in both of them? So over P+ and B+?

Look at the original diagram from the site, the one Chadworkz posted. The battery goes to the far left and far right pads, and the JST plug goes to the 2 left-most pads. You just need to make sure the polarity is correct, and they are labelled on the board.

The original diagram is drawn exactly as you need to wire it. The symbol on the top represents a voltage source (in this case a 3.7V lipo) and the bottom says load/charge, which is where you have the JST plug to connect to the charging circuit and also use it to charge the lipo.

That labeling is horrible. Which diagrams are each person talking about? One is flipped around the other way.

The manufacturers diagram don't line up with the labels IMO. The big one is batt +, the one next to it is load +, and the far one is common ground... that's just the way I am reading it.

Would it be this way then?
http://i53.photobucket.com/albums/g6...CMDiagram0.png

Ding ding ding! We have a winner!

Oh thank god, finally.
Confusing as hell... Not for you, but definitely for me..
Thanks guys, I'll see if all else goes well, and if not..will still post back.. with pictures!

Even if it seems unconventional it makes sense to me that the larger size pad was made larger because it has to have 2 wires soldered on (B+ and P+), and that would leave the other two smaller pads to be single connections of B- and P- respecitvely.

Well, despite the diagram on the site showing one thing, I really disagree with you. Look at the labels, you are plugging the JST into two positives, does that make sense? Am I missing something?

I would agree that the large contact looks like it would be for TWO connections, but not according to the babels.

I believe my first couple diagrams, I screwed up completely, but the newer one, on Post #29:
http://www.rc-monster.com/forum/show...9&postcount=29

Make sense to me..
considering it's positive on one side, and has two common grounds?

Just to be safe, sent in an email to verify my diagram, we'll see what they say

You don't have two common grounds, the whole sense of the term is "common", is exactly that, it is common to both source and load.

The only explanation is that the labeling is wrong, or the diagram they show with the product is wrong.

Do we need Brian in here for an opinion?

Here...

http://pics.offroadextremes.com/rc/wired_up.png

It's wired up so that the charger charges the battery without the charge current entering the device, and so that the device is powered by the battery current, not the charge current. All this time it is monitoring the charge and discharge cut-off voltages.

That's what I was thinking when I typed it
:lol:

Oh BrianG!

lol, I saw the opening post and thought the device Neil posted was pretty straightforward.

In looking at the pic below, it should be pretty obvious that the battery + and load + are common.

http://lib.store.yahoo.net/lib/thesh....7vpcb8.5A.jpg

Here...

http://pics.offroadextremes.com/rc/wired_up.png

It's wired up so that the charger charges the battery without the charge current entering the device, and so that the device is powered by the battery current, not the charge current. All this time it is monitoring the charge and discharge cut-off voltages.