After reviewing the recommended settings on this site it appears all that you’d have to change is the Capacity and Charge Current values to that which would be suitable for your particular battery, Pi Juice will likely have more specifications about the battery to determine the Charge and Termination current but they should be around the 20000mAh and 10000mA range if the 1:2 ratio is maintained (10000mA will probably be too high as I believe the highest value will be 2500mA).
Very understandable and accessible. Thanks for the clarifications. I am not very well versed in physics to make such calculations, so I prefer to rely on the opinion of more experienced people.
EDIT: The following is about LiPo batteries in general. As will all circuits, there is a weak link and it has been brought to my attention that the leads on single-cell Lithium polymer batteries are only rated for 1A max! Do not exceed this as it could lead to something nasty!
Hey Clark,
As dangerous as LiPo batteries can be, if treated properly they are rather unlikely to fail catastrophically.
Usually what would lead to fire with these would be Charging at to high of a current, charging at a voltage higher than 4.2 volts per cell, and damage to the cell’s internal construction.
To extend the life of a LiPo as much as possible, It is recommended to charge at 1-2C.
The battery C Rating is the measurement of current in which a battery is charged and discharged at. The capacity of a battery is generally rated and labelled at the 1C Rate (1C current), this means a fully charged battery with a capacity of 10Ah should be able to provide 10 Amps for one hour.
So for the 20,000 mAh battery that you have, a 1C charge rate would be 4.2V@20A.
It’s not really considered best practice for LiPos to charge at less than 0.5C as this can lead to the internal resistance of the cell/s increasing.
Another thing you could do in this instance is raise your cutoff voltage up to 3.2-3.5V instead of having it at 3V. Having a slightly higher cutoff, therefore not discharging the battery as far, will extend the cycle life and the overall life of the battery.
So just to clarify, as previously mentioned in this post I think that the highest charge current that can be set on the PiJuice is 2500 mA? This would mean the closest charge rate that I could set on the PiJuice for this battery would be 0.125C?
While that won’t raise the risk of spontaneous fire it will affect the life of the battery. On average, a LiPo in its lifetime will be good for 250-300 charge cycles when charged at 1C. In my experience, charging at double 1C or half 1C drops this number by anywhere from -10-20% and is cumulative. For example, charging at 3C would make this -30-40%, 4C would be -40-50%, and so on. Same for 0.5C, 0.25C, 0.125C…
All that being said, it isn’t going to cause any damage to your components and there isn’t an increased risk of fire.
Ideally, you could go to a 2500mAh battery if you were concerned about the life of the battery, and then could guarantee a 1C charge but having that much lower of a capacity, would lead to more charge cycles, and more than likely the battery wouldn’t last as long as the 20000 mAh.
Hi Jesse
Just having a bit of a look at this thread. Particularly the bit re Pi charging capacity apparently not being enough for optimum charging of this battery pack.
This seems a bit strange when the original splurge says it is suitable for use with a PiJuice (whatever that is, I assume some sort of management system) albeit with a note saying the profile needs to be changed to suit. But it seems the maximum charge rate that can be set with the profile settings is 2500mA which you have just stated is not enough for this battery. I have not gone into the details of optimum charge/discharge rates so I would not dispute your statements but I would question the claim (based on your discussion) that this battery is suitable for use with a PiJuice when it is pretty clearly not the case (for optimal operation anyway).
Interested to hear your thoughts on this.
Cheers Bob
Regarding the charge cycles, if the PiJuice is essentially being ran as a UPS and the RPi is under 24/7 operation. The battery shouldn’t be going through many charge cycles over its life time, unless its power source is cut and then the battery would start to be depleated.
Is this assertion correct?
Just to add to this, the primary power source for the Pi is from a solar panel, but the solar system has its own battery so the feed from that should be relatively constant. I got this battery and PiJuice so that the RPi can continue operating in the case that the solar systems battery is depleated from other sources.
While 1C will always be the optimum charging rate for LiPo batteries, it is not a requirement for their charging or operation.
In an ideal situation, you would want to charge and discharge at 1C and this would give you the maximum available life for the battery. This of course is the ideal situation. While the PiJuice will only charge at 0.125C at max current with the 20,000mAh battery, It still is a compatible battery, but would not be able to charge at the 'Ideal C rate".
All this being said, it has been brought to my attention that the batteries that we stock, only have wire ratings for a max current of 1A, and therefore anything larger than 1000mAh wouldn’t be able to safely charge at 1C anyway.
As you have your regulation voltage set to 4180 it will keep it at as close to 4.18V as best it can while ever it has incoming power like from your solar panel for example.
The assertion is correct that it will keep this in a ‘charged’ state till power loss from the external source.
Just to clear up for you, as i have already made an amendment to the previous post, the batteries that we sell have wires that are only rated to 1A so that will be the max charge rate for the battery regardless of any other factors. Weakest link breaks first
On that note that should be the maximum current you should draw from the battery also which is fair enough, C/20 which should ensue battery longevity.
Cheers Bob
that would work and would certainly be conservative!
I don’t expect 2000mA would actually give any trouble unless you notice the wires get unacceptably warm, or if you cycle the connection under charge/discharge loads.
For example, I would expect the Pi itself would draw a fair bit more than 1000mA through the cable during heavier loads.
Let me test a bit and post back, I had it at 2500mA for a while and noticed the cables got slightly warm to touch while charging. At 1000mA there is no noticeable temp change on cables while charging.
