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Old Aug 13, 2014, 06:49 AM
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United States, AL, Daphne
Joined Nov 2009
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LiPo and Charger Questions

Been out of the hobby for 15 years and getting back to open class thermal duration and DLG. All this LiPo, LiFe, etc. battery stuff is daunting. Back in the day of NiCd's I had a charger with two Tx outputs and four Rx outputs so I could charge extra batteries and take to the field for a day of flying. I have a few questions:
1. I've read that LiPo chargers only charge one battery at a time. Isn't there a charger with several outputs so you can charge back-up packs?

2. I've read about overcharging and causing fires. Don't chargers have circuitry that senses charge current, voltage, or whatever and shuts down at the correct time?

3. 1S LiPo's put out 3.7V but Airtronics says their receivers operate at 4.8-7.4V. ( I asked Airtronics about this and they said they don't recommend it but people get away with it) People I've talked with say they do this all the time. They can fly for an hour (and longer)and the 3.7V doesn't drop enough for the Rx to quit working?

4. I've read about voltage boosters for upping 1S voltage to 5V which is correct for the Rx. Do these boosters shorten usable battery time? Are they reliable?

5. I've read about 2S LiPo's with a regulator to drop the voltage to the correct level. Is this a better way to go than the 1S and lower voltage?

6. I know there are many variables but let's take a 1S 1,000 mAh LiPo Rx battery, discharged to where it's not safe to fly, how long would it take to fully charge? I know it depends on the charger, amount of discharge, etc. but are we talking a few hours or overnight?

Thanks from a battery newb.

Trey
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Last edited by Trey4U; Aug 13, 2014 at 07:11 AM.
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Old Aug 13, 2014, 07:28 AM
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United States, MN
Joined Feb 2011
4,349 Posts
Quote:
Originally Posted by Trey4U View Post
1. I've read that LiPo chargers only charge one battery at a time. Isn't there a charger with several outputs so you can charge back-up packs?
Yes in two different ways. There are multi-port chargers, but they tend to be low power and slower on larger packs. The other and very popular option is parallel charging:
http://www.tjinguytech.com/charging-...allel-charging

Quote:
Originally Posted by Trey4U View Post
2. I've read about overcharging and causing fires. Don't chargers have circuitry that senses charge current, voltage, or whatever and shuts down at the correct time?
Yes they do. Most lipo fire videos you see on the internet were caused by using a charger in Nimh mode to intentionally over charge and cause the fire. If you use a lipo charger and connect the balance lead it will never over charge.

Quote:
Originally Posted by Trey4U View Post
3. 1S LiPo's put out 3.7V but Airtronics says their receivers operate at 4.8-7.4V. ( I asked Airtronics about this and they said they don't recommend it but people get away with it) People I've talked with say they do this all the time. They can fly for an hour (and longer)and the 3.7V doesn't drop enough for the Rx to quit working?
I would not do it. Many people use LiFePo4 (also known as A123) if they want to use a lithium type battery for their receiver. A 2S LiFePo4 pack is 6.6v which is about the same voltage as a 5-cell Nimh/Nicd pack. So in most cases a 2S LiFePo4 is a direct replacement for Nimh/Nicd. Also LiFePo4 is more tolerant of being stored fully charged then LiPo so it is better suited for use as an Rx pack.

Quote:
Originally Posted by Trey4U View Post
4. I've read about voltage boosters for upping 1S voltage to 5V which is correct for the Rx. Do these boosters shorten usable battery time? Are they reliable?
Typically you don't boost, but rather buck. People use a 2S or larger LiPo and a UBEC to drop the voltage to 5V. They are for the most part reliable but as with any electronics they can fail.

Quote:
Originally Posted by Trey4U View Post
5. I've read about 2S LiPo's with a regulator to drop the voltage to the correct level. Is this a better way to go than the 1S and lower voltage?
I think so. I've never heard of anyone using 1S.

Quote:
Originally Posted by Trey4U View Post
6. I know there are many variables but let's take a 1S 1,000 mAh LiPo Rx battery, discharged to where it's not safe to fly, how long would it take to fully charge? I know it depends on the charger, amount of discharge, etc. but are we talking a few hours or overnight?
With right battery and charger as little as 10min or even less.

There's tons of good info to get you started here:
http://www.tjinguytech.com/charging-how-tos
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Old Aug 13, 2014, 07:31 AM
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Thanks for the info and link!
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Old Aug 13, 2014, 04:44 PM
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United States, WA, Woodinville
Joined May 2014
434 Posts
If you're running on 1S a boost converter can be used to power the rx. They're usually around 80% efficient so it does increase the load on the battery some but it's still a tiny draw compared to the motor powering the plane.

I would probably just use a receiver that others have found to work fine on the lower voltage though.
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