about Lipo charger & powerboost

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RichardHaight
 
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about Lipo charger & powerboost

Post by RichardHaight »

Back in April (maybe March) this year I bought the following items from Adafruit:

a. a 1200 mAh 3.7v Lipo battery
b. Adafruit Micro Lipo w/MicroUSB Jack - USB LiIon/LiPoly charger -- ID 1904
c. Adafruit Powerboost 1000

Using information from the Internet (esp. from https://www.youtube.com/watch?v=RiZ0g1bJ8sw) I connected the devices as follows:

See http://dicks-arduino-nano.blogspot.com/, post 11

After charging the battery I tested the setup with 3 different "computers":
1) a Raspberry Pi model B/rev2,
2) an Arduino Nano, and
3) a Particle (then "Spark") Core.

All three worked both with and without the USB-IN cable which was connected to a powered USB hub (1A out). Unfortunately, I did NOT think to test with the battery disconnected. I did check to see how long each setup ran on battery alone (satisfactory) but had not left the systems running a long time with both USB-IN + battery.

To my surprise, the latter arrangement did not keep the battery charged. Furthermore, once the battery ran down the circuit dropped well below 5v. Here's some results:

A. Input from charged Lipo + 1A/5v USB -> 5.0+v to the USB-OUT
B. Input from 1A/5v USB only (or battery depleated) -> 4.18v to the USB-OUT.
C. Input from 2.1A/5v USB only -> 5.1v to the USB-OUT

Obviously, case B doesn't work. Also, powered hubs don't usually provide a 2.1A port.

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adafruit_support_bill
 
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Re: about Lipo charger & powerboost

Post by adafruit_support_bill »

What was your load? The micro-lipo charger only charges at 500mA. Then there is the charge efficiency of the battery (say 85%) and the boost efficiency of the PowerBoost (~90%) and the current drop that will be proportional to the voltage boost.

0.85% * 0.9% * 3/7v/5v * 500mA = 283mA. Anything more than that will yield a net discharge of the battery.

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RichardHaight
 
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Re: about Lipo charger & powerboost

Post by RichardHaight »

My surprise about the setup was that 5v/1A USB into the charger (battery NOT connected) did not provide 5v output through the powerboost.

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adafruit_support_bill
 
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Re: about Lipo charger & powerboost

Post by adafruit_support_bill »

It can't. The output of the charger stage is 500mA max. And that is only when it detects that a healthy battery is connected and ready.

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RichardHaight
 
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Re: about Lipo charger & powerboost

Post by RichardHaight »

So, my setup: 5v/2.1a into charger, charger connected to Lipo plus jumpers to Powerboost 1000; Powerboost USB out to Particle Core (or Arduino Nano -- doesn't matter) runs the battery down and current drops to about 4.1v and the Core (or Nano) quits.

My question is: does Adafruit sell something that DOES work as a small-scale UPS?

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PandaMonium
 
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Re: about Lipo charger & powerboost

Post by PandaMonium »

adafruit_support_bill wrote:What was your load? The micro-lipo charger only charges at 500mA. Then there is the charge efficiency of the battery (say 85%) and the boost efficiency of the PowerBoost (~90%) and the current drop that will be proportional to the voltage boost.

0.85% * 0.9% * 3/7v/5v * 500mA = 283mA. Anything more than that will yield a net discharge of the battery.
I guess I don't get it, then. These are being advertised as a sort of UPS for a Raspberry Pi. I had assumed that if I used a ~1.8A USB-plug power supply, the RasPi would run off the power supply UNLESS the wall socket power was interrupted, and then the PB500 would draw from the battery to power the RasPi until wall socket power was restored.

Most RasPi models draw a minimum of 330ma even at dead idle, though (only the A+ draws less, and that's only at idle). So, does that mean I, for example, have to swap batteries daily? Do I need to design a completely different circuit to behave as an actual UPS? Would using a PB1000 work as a real UPS, maintaining the battery as fully charged and then powering the RasPi during short-term blackouts/brownouts?

Thinking about it, I can use two battery holders through a switch, charge one battery on a separate charger, insert it into the second holder, hit the switch, and hope that the switchover is fast enough that the RasPi doesn't glitch or power down. Then remove the first battery and charge it overnight for the next day's swap. . . .

If it makes any difference, I'm using Li-Ion (18650 cell, 2600ma), because I don't like the fire risk that LiPo presents.
Last edited by PandaMonium on Sat Aug 29, 2015 2:37 pm, edited 1 time in total.

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adafruit_support_bill
 
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Re: about Lipo charger & powerboost

Post by adafruit_support_bill »

You want the PowerBoost 1000 C. https://www.adafruit.com/products/2465

This has an integral charger with a load-sharing circuit so you can run the Pi from the input power while the charger current goes to the battery.

The OP was trying to run a Pi AND charge a battery from a micro-LiPo charger which has a 500mA max charge output - and no load-sharing circuit.

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PandaMonium
 
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Re: about Lipo charger & powerboost

Post by PandaMonium »

adafruit_support_bill wrote:You want the PowerBoost 1000 C. https://www.adafruit.com/products/2465
Glad I got one of those too, then! I'll have to solder it all together. Wish I'd bought more of those instead.

Thanks!

Do you happen to have the maximum draw amps figures for the PB1000? Based on some stats I've found, I am guessing my Pi will be drawing a max of 460ma, more likely 400ma.

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adafruit_support_bill
 
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Re: about Lipo charger & powerboost

Post by adafruit_support_bill »

The PB 1000 can comfortably provide 1000mA (1A) at 5v continuously - assuming a 3.7v LiPo input capable of a 2A discharge rate.

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RichardHaight
 
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Re: about Lipo charger & powerboost

Post by RichardHaight »

None of the responses since my post of May 14, 2015 answers the question I posted at that time. I still need reliable battery backup for RasPi and Arduino. I would think that plenty of others need this too.

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adafruit_support_bill
 
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Re: about Lipo charger & powerboost

Post by adafruit_support_bill »

You want the PowerBoost 1000 C. https://www.adafruit.com/products/2465

This has an integral charger with a load-sharing circuit so you can run the Pi from the input power while the charger current goes to the battery.

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PandaMonium
 
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Re: about Lipo charger & powerboost

Post by PandaMonium »

Just an update on the PB1000 with the RasPi. It's working fine with a single 2600mAh Li-Ion (18650 type) cell.

I soldered the USB connector in, charged a cell until the green LED came on, then plugged everything together with the RasPi. Booted up fine. I've been unplugging things and plugging the cell back in to see if it all keeps functioning. Starting with a fully charged 2600mAh cell, the BP1000 was flashing its red LED after a little over an hour; at that point I realized I'd forgotten to plug in the USB-plug power supply (hereafter, "wall wart"). :-} Oops. Well, that would've been another test anyway! Popping the battery out, the RasPi died even though it was plugged in -- the PB1000 eats some of the power from the USB charger itself, so if your charger is already minimal, it won't keep the RasPi on while running through the PB1000. Solution is to use a larger (more amps) USB wall wart.

With the larger wall wart in place, I can pop the battery in and out, or unplug and plug in the wall wart, and the Pi continues to function. Obviously cannot unplug both at the same time. The PB1000 charged the cell while running the Pi, from flickering red LED to green LED, in under two hours.

I don't know how long it will run until the battery drains low enough to kill it, but most power outages in this place are over in a matter of minutes, so it's more than sufficient for my needs. I was expecting 4 hours (500mAh per hour, with an efficiency of around 80%), but the flickering-red level came on a lot sooner than that, so maybe not. Or maybe these 18650s aren't really as big as the package claims, which is very possible (cheap Chinese cells).

Is it possible to charge multiple cells in a parallel battery box? I'm not really planning on it, but for future projects it might be something I'd want to try eventually. I don't know if that would work safely, though.

Hope this helps someone!

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adafruit_support_bill
 
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Re: about Lipo charger & powerboost

Post by adafruit_support_bill »

It is not safe to charge (or discharge) individual cells in parallel. There are multi-cell packs, but the cells in these packs have been precision matched at the factory for compatible charge/discharge characteristics.

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RichardHaight
 
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Re: about Lipo charger & powerboost

Post by RichardHaight »

After seeing the post about needing a Powerboost 1000C (instead of the Powerboost 1000) I coughed up another $19.95+shipping. I've tried this with both a Raspberry Pi and a Particle Photon. It ran the Pi for three weeks just fine. If I unplugged the USP line input it kept working; if I unplugged the Lipo the Pi restarted. Not nice, but not a deal breaker. See http://dicks-raspberry-pi.blogspot.com/, post 88 for interesting details. I'm surprised that with millions of Pi's and Arduinos around that this is not a hot topic.

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knossos
 
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Re: about Lipo charger & powerboost

Post by knossos »

Could you take two Power Boost 1000 C's and parallel the outputs? I'm looking at running a RPi B+ or RPi 2 with a PI Foundation Display, SATA HDD, WiFi, Camera, etc. I have yet to measure current but I'm fairly certain it will exceed the capability of a single Power Boost 1000 C.

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