so, using this battery, thinking about a mod. Could use some tips.

[Lance_Wallen]

All-Battery.com: AT: Tenergy 7.4V 1150mAh LIPO PCB Protected Battery Pack w/ Bare Leads

there's the battery I'm looking at. I like the size and profile for the mod I'm making (secret!). Going to put an adjustable regulator on it, a switch, and the connector obviously. What I'm a little on the fence about is how to make it rechargeable. I don't know alot about making something rechargeable so any tips would be great. Can I just split the leads at the battery and connect it to a mini-usb female and use a standard usb-mini usb cable to charge it?

 

[asdaq]

Not quite so simply. That battery needs protection from overcharging (8.4v) and over-discharging (4.6v). Also since it is 2 cells it needs a balancing charger. The related products from your link offer the needed parts, and if you build these into a mod, you lose quite a bit of space you are looking for in using a compact battery in the first place. A single protected cell with an on board charger will be smaller and allow a usb port like you are wanting, but it would only be a 3.7v mod....

 

[Lance_Wallen]

that battery has a PCB on it according to the description below. does that not take care of what you mentioned?

 

[Java_Az]

Yes it does have built in protection. but you still have the problem of a USB port is 5volts and that battery pack charges @ 8.4 volts. That usually means your going to need a source voltage of about 9 volts. USB charging is not really a good option for 7.4 volt battery packs. I am not saying it cant be done but it would be a pain and take up space and cost quite a bit. Your best bet is to use the Adapter recommended on the battery page to do on-board charging. Someone else just did a MOD with a li-po battery similar t the one you posted and that's how they solved the problem.

 

[VpnDrgn]

The pack has built in protection. You would need a multi-cell charger like this one.
All you would need in the mod is a port for plugging in the charger.

You could use a diagram like thisView attachment VV BOX MOD V2.pdf, rearranged for your enclosure.

The only thing you will have to check is the specs on your VV circuit.
The discharge protection on that polymer pack seems kinda high.

 

[asdaq]

Sorry, I wasn't so clear. The battery is indeed protected itself, but you need a multi cell charger to charge it. That rather defeats your original wish to have the mod chargeable by a standard USB port, even if you stuck the sizable charger inside the mod.

 

[Lance_Wallen]

I guess making it wall charger only isn't that big of a deal. Having a single battery at that size seems to be half the amount of space taken up than in a normal mod capable of that voltage.

 

[unloaded]

I'd track down a charger that can use voltage from the wall or a vehicle's 12v. Just to have the portable option.

 

[CraigHB]

The hobby LiPos are much cheaper, this one, for example. The drain is also much higher so you don't have to be as concerned about going over-current. However, you do need to protect them from shorts. A PTC fuse is a good way to do that. Something like this would do the job.

The hobby packs are designed to be charged with a "balancing charger". You can get them pretty cheap if you shop around.

Depending on the regulator you use, you may need to protect them from over-discharge. There are some simple ways to do that people have discussed in threads here.

Alternatively, you can buy protection modules for LiPo packs. There's some various protection modules here. It greatly simplifies protection, but you can't use a balancing charger in that case. It's much better to use a balancing charger than a "pack" charger. Pack chargers can cause mismatched cell voltages which can greatly reduce cell life and run time performance.

There's a way to use USB to charge a pack. Use two charging modules and add a switch that pulls the batts out of series and connects them as required for charging. Switching can be done either by a separate slide switch or by using a multi-pole momentary switch as the trigger. You would probably have to dissassemble the pack and rewire the cells. Hobbyking also sells individual cells for making your own packs.

You should be able to parallel the charging units with a single USB jack. Would require some fine soldering work.

Using two USB charging modules would be equivalent to a balancing charger.

Okay, best of luck with it.