Magnum with Charging Base

[mjp808]

I would like to start this thread as a home for this mod that seems an inevitable evolution on MadDog's design. I am working on one, but have some initial questions:

With the original Magnum you remove the batteries to charge them in the the charger. The charger has 4 contacts, 2 pair, trickling 3v each. Can I just jump a wire on the charger to get just 1 pair of contacts trickling in 6v so that I can charge the batteries while they are configured inline?

 

[secondson2929]

Usually a lithium charger monitors each cell by itself. It can be done in series though, just not sure of the safety.

Here's a link to a diagram...

http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm#lithium.gif

--scroll down--

 

[mjp808]

Thanks secondson. I was afraid it was a schematic--I can't read em. But everything I need to know is there, for sure--good find.

When I get my batteries from xtrmedeal, I will work on the one-3.7 battery type mod first. A charging station will be easier to make for one battery.

 

[ratfink]

Thanks secondson. I was afraid it was a schematic--I can't read em. But everything I need to know is there, for sure--good find.

When I get my batteries from xtrmedeal, I will work on the one-3.7 battery type mod first. A charging station will be easier to make for one battery.

A 555 timer is never going to fully charge a Li battery safely, they have a very tight curve and have the potential to vent flame when improperly used. You are much better off with a specialized charge IC to base things around.

If you want to run things from a regulated supply take a look at the TI BQ2057C or BQ2057 (sorry can't post links). They are pretty much the same price but one charges to 4.1 the other 4.2 the difference is about 10% of the charge but not all batteries will go to 4.2 and it puts a lot more wear on the battery. These charge circuits are bare bones (externally they only need a regulated power suppy and 1 transistor, 1 cap + decoupling and a few resistors) models and don't have fancy LED displays and such but are not hard to solder in the SOIC package. Another solution is the bq2054 or bq2954, it comes in a throughhole dip so it's dead easy to work with and it has LED indicators, only problem is you need to program the voltage requirements with resistors which requires math .

If you are just working with one cell and you absolutely must have it powered by USB, TI has a few good solutions too. The bad news is that they are damn small and not the easiest to solder (but not that hard). Look at the BQ24026, BQ24038 or BQ24072.

Whatever you do, be careful and test the charger on a place that can handle the battery venting flame without burning down your house.

 

[ratfink]

I forgot to mention in that other post, for safety you should mount a thermistor along side the battery if you can fit it.

 

[RayJ1]

One of my hobbies is racing radio controlled cars powered by li-poly and li-ion batteries. Charging multiple batteries connected in series requires special chargers that require a balancing lead to balance the charge on cells individually . LI-ion batteries are very sensitive to overcharging and over discharging the cells. Overcharging batteries can be very dangerous!!! Also......discharging these cells below there operating voltage threshold can internally damage the cell as well. Once these bagtteries have been over discharged....there life cycle is dramatically reduced.