Possible future add-on to use any kind of battery?

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Possible future add-on to use any kind of battery?

Unread postby putputer » Thu Dec 15, 2016 9:14 am

Will there ever be a good Universal Power Supply add-on meant to take any kind of battery configuration available in the future? Preferably one that can deliver up to 6A for all the passive usb add-ons and the VU-7 Plus display?

One of the things that has me wondering is wanting to take an Odroid-C2 or XU4 (or C0 if being a bit extreme) and turn it into a laptop using either spare parts, stuff off the Odroid or AmeriDroid store, or the Amazon shop. However, one of the things that is required is a battery pack capable of running it for at least a couple hours or long hours without being connected to an outlet. The problem is the logistics like connecting the VU-7 or another screen, an SSD, a stripped down powered USB hub, Wifi, and Bluetooth would drain the 3A battery in less than an hour from what I've read on the forum, even much much less with the normal regulator installed. And even while I tried to study Ohms law, lithium-polymer battery banks are notoriously fickle that I would either have to build a custom circuit board or find the right parts to have it charge the battery and power 4 things at once, including the Odroid. Pretty sure I would make one explode if I tried without a lot of study.

I did look up other threads that had this problem and the only thing I can think is that it looks very complicated. viewtopic.php?f=97&t=14807 and viewtopic.php?f=97&t=14988
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Re: Possible future add-on to use any kind of battery?

Unread postby crashoverride » Thu Dec 15, 2016 10:01 am

It seems the issue with a "universal" charger is that it has to either know information about the battery or use a "lowest common denominator" strategy for charging. I have been using cell phone charging battery packs for various projects. Eventually, everyone runs into the "I need more amps" problem.

This is my understanding of the situation. Different capacity LiPo batteries require different charge rates to prevent damage, poison gas, fire, or explosion. While in theory you can increase the mAh by using larger capacity batteries or adding more cells in parallel, they all charge slower than they discharge. When charging larger capacity batteries you need to increase the amount of charge current to decrease the charge time. This can not be safely done without knowing the specification of the battery. Because of this, most circuits charge at a set rate and specify a minimum capacity battery for use. No matter what battery is attached, the charge rate is the same.

If battery charge rate is half of discharge rate, then for a 5V@6A battery that lasts 1 hour, you would need to charge it at 5V@3A for 2 hours. Most generic chargers will use less than 5V@1A but some are available that deliver 1A. Charging at 5V@1A would take 6 hours for a battery that only lasts 1 hour. This is why it is necessary to select a matching battery and charger that meets your requirements.

[edit]
Its important to note that a 6000mAh battery at 5V is not the same as a 6000mAh battery at 3.7V. Most batteries are rated at low voltages such as 3.7V.
Volts * Amps = Watts
3.7V * 6A = 22.2W

Amps = Watts / Volts
4.44A = 22.2W / 5V

3.7V@6000mAh = 5V@4440mAh

Additionally, there is a percentage of power loss when converting the voltage in real life.
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Re: Possible future add-on to use any kind of battery?

Unread postby putputer » Thu Dec 15, 2016 11:38 am

Since your experienced with phone battery packs, will this one be a good replacement without the need of a custom battery bank and circuits? https://www.amazon.com/Anker-PowerCore- ... B01JIWQPMW

If not, I've seen only one charger of what I've described on Adafruit. https://www.adafruit.com/products/259

Everything else, I'm going to have to read up on these batteries and beginners electric engineering to really understand it. I was able to find a place that sold the type I wanted. https://www.alibaba.com/product-detail/ ... 72424.html

(Most of the pages I've been looking at when trying to find a battery is usually built for radio controlled vehicles or come in a series of AA-sized 18650 batteries you have to wire up.)

Also, yes it's a testament to how little I know of electrical engineering, because I see 3.7V that most batteries has as too low while the Odroids need a 5V input to keep itself active. (And trying to read the cryptic tutorials how RPi laptops work don't help too much.)

Side note, I did find some more information within the Magazines twice. http://magazine.odroid.com/wp-content/u ... df#page=14
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Re: Possible future add-on to use any kind of battery?

Unread postby rooted » Thu Dec 15, 2016 12:03 pm

Take four 3000mAh 18650 (Samsung 30q is what I recommend) batteries run in two parallel sets (8.4v) and an inexpensive buck converter and 2A micro charger.

You could cobble this together for $29 or so, or use something like the Anker you linked above.
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Re: Possible future add-on to use any kind of battery?

Unread postby crashoverride » Thu Dec 15, 2016 2:17 pm

I can not recommend any particular battery. I will, however, warn you that when buying a battery online, the stated capacity is usually fake. Look for reviews from others that state what the actual capacity is.

putputer wrote:If not, I've seen only one charger of what I've described on Adafruit.

That charger has a maximum charge rate of 1A. It will take several hours to charge anything of a large capacity as noted earlier in my post.

putputer wrote:I did find some more information within the Magazines

Laptop batteries have a chip that provides information about the cells in them. This allows them to be charged safely at higher rates (assuming the chip data is not faked).
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