mulligan
Posts: 1147
Joined: 4/14/2002
From: Sanford,
FL, USA
Status: offline
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[QUOTE]Originally posted by MonkeyBoy
They won't go BOOM (OK, probably won't go boom.) There is nothing magical about charging Li-Po. All you need is a charger that limits output above a certain voltage. I have a home made dual charger I made for about $15 with RadioShack parts. I have two outputs, it is selectable form 1 to 3 cells, and charge rate is selectable from 50ma to 1000 ma in 50ma increments, independently on both channels. I use it all the time to charge my 1000mah and 2000mah Li-Po packs. Probably over 100 cycles now. Nothing went boom. It works just fine.
My charger isn't a slick as a charger that uses a ready made Li-Po charging IC. Mine slowly reduces charging current as the cutoff voltage is reached. Once cutoff voltage is reached, the packs are floated at that voltage. The purpose built ICs tend to charge at a higher rate longer and then quickly shut down... all this really does is just shorten the time required to fully charge the pack. In other words, my home built charger will fill a 1000 mah pack to 90% in say an hour, just like the brand name chargers, but it will take my charger another hour to get the last 10% into the battery while the IC based charger would only take another 10 minutes or so. I get around this extra wait by only using the brand name charger for finishing the packs off that I charged to 90% on my home made charger... mainly becasue I don't like to wait. If I left the pcak on my home made charger, they would charge to full eventually and then the charger floats the pack, i.e., you could leave the pack on forever without causing damage.
When I get home, I'll open my charger up to see what I did to build the circuit... I can't remember off the top of my head, but I think I used an adjustable voltage regulator with feedbacks to set charging current and cutoff voltage.
Cheers [/QUOTE]
"Probably won't go BOOM"... Geez, I hope you're not in sales anywhere.
There's nothing "magical" about a building a bomb either, but's that's what you've got if you don't do it right. For me, it's silly to introduce that kind of risk to amateurs with "homebuilt" designs. And that's what I and most of us are here when it comes to electrical/circuit design/building- amateurs (if you're not an amateur, chances are you don't need the schematic in the first place- you could design/build your own).
I don't mean to flame anyone- just understand the audience and disclose the risks involved. In any case, I recommend that for Li-ion, folks shell out the few extra bucks to buy from a reputable vendor for safety's sake.
- George
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Home made Lithium Ion battery charger - 
Home made Lithium Ion battery charger - 
