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WillBoxOwO
Posts: 116
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 6:35 pm

**Im answering W. H. Heydt in this post, I didnt do quotes since there was too much meta-stuff going on, lol**

You said: "The safe way to figure the power requirement is to assume the Pi is pulling all the power it can: 2.4A."
Its not 2.5A? Wont it cause the thunderbolt thing? Lets not forget I want to overclock this baby... Should I forget about it? 8-)

You also said: "Use the 2.4A port for the Pi and the 1.5A port for the speakers. "
The speaker is in fact, a bud light speaker. (Image here, sorry I couldnt find the exact specs of it. I tried 5v 1A and it seemed fine...)
Image

Wont it break the speaker to put 1.5A in it? The board inside it is probably really cheaply made, I wouldnt like it if it stopped working since its the only one I got. Should I open it and investigate?

Finally, you said: What I would suggest is that you get the Monoprice 10.4Ah unit and test it to see if it will run what you want to run and for how long.
I think this baby is the best option afterall- ill make the test. Im shure well be able to make it work. Thanks for your precious advice :mrgreen:
I like cats

drgeoff
Posts: 9743
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 7:16 pm

WillBoxOwO wrote:
Sat Nov 03, 2018 6:35 pm
**Im answering W. H. Heydt in this post, I didnt do quotes since there was too much meta-stuff going on, lol**

You said: "The safe way to figure the power requirement is to assume the Pi is pulling all the power it can: 2.4A."
Its not 2.5A? Wont it cause the thunderbolt thing? Lets not forget I want to overclock this baby... Should I forget about it? 8-)

You also said: "Use the 2.4A port for the Pi and the 1.5A port for the speakers. "
The speaker is in fact, a bud light speaker. (Image here, sorry I couldnt find the exact specs of it. I tried 5v 1A and it seemed fine...)
Image

Wont it break the speaker to put 1.5A in it? The board inside it is probably really cheaply made, I wouldnt like it if it stopped working since its the only one I got. Should I open it and investigate?
RPI 3B+ default clock speed is close to the limit. In fact it readily throttles back from default when working hard. IMHO not worth the effort trying to overclock.

You don't seem to appreciate that any device (not only a RPi) at its working voltage tries to take the current it needs. It is not a case of the PSU forcing more current into it.

Those little speakers usually have quite efficient amplifiers. If it gets to taking 1 amp at 5 volts the speaker will at least be distorting like h*ll and possibly on its path to physical damage.

W. H. Heydt
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 7:52 pm

WillBoxOwO wrote:
Sat Nov 03, 2018 6:35 pm
**Im answering W. H. Heydt in this post, I didnt do quotes since there was too much meta-stuff going on, lol**

You said: "The safe way to figure the power requirement is to assume the Pi is pulling all the power it can: 2.4A."
Its not 2.5A? Wont it cause the thunderbolt thing? Lets not forget I want to overclock this baby... Should I forget about it? 8-)
All Pis (other than the Pi0/Pi0W) have current limiting circuits and polyfuses. IIRC, the Pi3B+ and Pi3B are limited to 2.4A. I might be wrong and the Pi3B+ may be 2.5A, but I don't know of any 2.5A rated powerbanks. The lightning bolt icon is a indicator of undervoltage condition...which is usually caused by the current draw on the PSU dragging down the voltage through internal resistance (this is a major reason why "chargers" make lousy PSUs...they aren't really designed to provide the full, "rated" current and maintain 5v at the same time; the other major cause is thin power wires with too much resistance).
You also said: "Use the 2.4A port for the Pi and the 1.5A port for the speakers. "
The speaker is in fact, a bud light speaker. (Image here, sorry I couldnt find the exact specs of it. I tried 5v 1A and it seemed fine...)
Image

Wont it break the speaker to put 1.5A in it? The board inside it is probably really cheaply made, I wouldnt like it if it stopped working since its the only one I got. Should I open it and investigate?
I said "the 1.5A port" because that's what the specs on that battery state. What that really means is "up to 1.5A if the device wants it". Your speakers are not spec'd to draw that much...so they won't. This is the same basic answer as that given to people who ask if they can use <some arbitrarily high current rated> power supply for a Pi. The biggest risk of attaching a device to a massive power supply is that if there is an internal fault, when the device goes up in smoke it may do so in a truly spectacular fashion. A 1.5A supply into a device that runs on 1A doesn't really carry that particular risk. Destruction, yes, if there's a short, great flaming gouts of fire...not so much.

As an example... When I use that battery, I connect the 2.4A port to the Pi2Bv1.1 (which is limited--IIRC--to 1.8A) and the 1.5A port to the 7" RPF display, which only need 250mA. Works really well and I never get the undervolt lightning bolt.
Finally, you said: What I would suggest is that you get the Monoprice 10.4Ah unit and test it to see if it will run what you want to run and for how long.
I think this baby is the best option afterall- ill make the test. Im shure well be able to make it work. Thanks for your precious advice :mrgreen:
I like Monoprice. They have good equipment--and cables--and reasonable prices. Next major thing I plan to get from them is a set of $50 noise-cancelling headphones.

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WillBoxOwO
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 8:49 pm

W. H. Heydt wrote:
Sat Nov 03, 2018 7:52 pm
As an example... When I use that battery, I connect the 2.4A port to the Pi2Bv1.1 (which is limited--IIRC--to 1.8A) and the 1.5A port to the 7" RPF display, which only need 250mA. Works really well and I never get the undervolt lightning bolt.
Awesome! All of my concerns about this project are out of the way now, except for this: Can you split power between the speaker and the screen?
Im also starting to think I could simply connect a low-end adafruit speaker directly in the jack port.

Again, thanks for your help.
I like cats

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WillBoxOwO
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 8:57 pm

drgeoff wrote:
Sat Nov 03, 2018 7:16 pm
RPI 3B+ default clock speed is close to the limit. In fact it readily throttles back from default when working hard. IMHO not worth the effort trying to overclock.
Ill put a good heatsink on it- I doubt it could throttle back to 1.4Ghz. It only does that kind of thing when working at 80 c. temperatures
drgeoff wrote:
Sat Nov 03, 2018 7:16 pm
You don't seem to appreciate that any device (not only a RPi) at its working voltage tries to take the current it needs. It is not a case of the PSU forcing more current into it.
W. H. Heydt just explained me the same thing! Thanks :mrgreen:
drgeoff wrote:
Sat Nov 03, 2018 7:16 pm
Those little speakers usually have quite efficient amplifiers. If it gets to taking 1 amp at 5 volts the speaker will at least be distorting like h*ll and possibly on its path to physical damage.
In case you didn't know, this speaker have a micro USB input on it for power- I then plugged it into my iPhone charger and it seems to works just fine. :) (no distorsion, been using the same setup for a month now) ;)
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drgeoff
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 9:13 pm

You cannot get enough power from the 3.5mm socket on a RPi to make a loudspeaker audible from the other side of a wet newspaper. You need a powered amplifier.

Your bud speaker is not drawing 1 amp. Rather less.

Ger_Pa
Posts: 55
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Re: A good battery for the Pi 3B+?

Sun Nov 04, 2018 4:37 pm

The Mi Power Bank 20000mAh it's rated at 5.1v 3.6a. So it should do the trick for what you want. But remember that power banks are meant to charge and not act as a power supply. They will work sure, but sometimes you may V drops. I used to use a romoss 5v 2.5a with a Pi3b and it worked fine but in some odd instances it dropped V (guess i could blame the USb cable too) and with the 20000mAh it lasted a few hours.

drgeoff
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Re: A good battery for the Pi 3B+?

Sun Nov 04, 2018 4:51 pm

My rule of thumb is to halve the quoted capacity and use the resulting figure when calculating run time.

1. The quoted capacity is invariably that of the cell which is of lower voltage than 5. Converting to 5 volts reduces the mAh figure by about 25% even if the dc-dc converter is 100% efficient.

2. The dc-dc converter is not 100% efficient.

3. The capacity is usually, shall we say "optimistic".

4. The type of cells used begin to lose ability to store charge from the moment they are produced.

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WillBoxOwO
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Re: A good battery for the Pi 3B+?

Sun Nov 04, 2018 6:27 pm

Update:
Took the speaker out of its case. Had to do some desoldering and resoldering to remove the male-jack thing from the case, here is the result:
Image
drgeoff wrote:
Sat Nov 03, 2018 9:13 pm
Your bud speaker is not drawing 1 amp. Rather less.
You were right.

I noticed in the back of the speaker it was using a Lithium cell (I didnt expect that!). Did some research about it and I found similar sizes of this battery delivering currents similar to 3.7v - 250mAh (Couldnt find the exact model). Here is a photo of the back of the circuit board:
Image
Could I desolder the battery and attach it directly to my battery pack? If I use the MicroUSB port, for some reason, sound gets a little distorted and theres lots of white noise.

Cheers. :mrgreen:
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dchislop
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Re: A good battery for the Pi 3B+?

Sun Nov 04, 2018 8:12 pm

I've been trying to work portable as well, I had no luck with 4x1.2Volt rechargeables or even 4x1.5Volt AA batteries. They didn't have enough power to even boot up the Pi 3. I even tried a 5.1Volt Zener Diode circuit but didn't work either. I now trying a 6Volt sealed lead acid battery from Toolstation priced £6.38, it's rated at 1.2Ah and small too, just 97x24x58mm. It drops to 5.7 Volt once up and running but the voltage soon falls away only giving me a operating time of 15 minutes before the low voltage indicator appears and another 5 mins before conking out completely. I know I should really supply a steady 5.1Volt so I would interested to hear of other solutions.

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Imperf3kt
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Location: Australia

Re: A good battery for the Pi 3B+?

Sun Nov 04, 2018 9:11 pm

WillBoxOwO wrote:
Sun Nov 04, 2018 6:27 pm
Update:
Took the speaker out of its case. Had to do some desoldering and resoldering to remove the male-jack thing from the case, here is the result:
Image
drgeoff wrote:
Sat Nov 03, 2018 9:13 pm
Your bud speaker is not drawing 1 amp. Rather less.
You were right.

I noticed in the back of the speaker it was using a Lithium cell (I didnt expect that!). Did some research about it and I found similar sizes of this battery delivering currents similar to 3.7v - 250mAh (Couldnt find the exact model). Here is a photo of the back of the circuit board:
Image
Could I desolder the battery and attach it directly to my battery pack? If I use the MicroUSB port, for some reason, sound gets a little distorted and theres lots of white noise.

Cheers. :mrgreen:
That looks like a mini USB port - far inferior to micro USB.
But ultimately, it seems the port only charges the battery and the speaker actually runs off the battery. You get the noise because you have created a ground loop by trying to charge the speaker at the same time as use it.

Yiu could desolder that battery and use it elsewhere, but be very careful with lithium batteries. If improperly handled or incorrectly charged or even over discharged, they can be extremely dangerous. I suggest some research first.
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W. H. Heydt
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Re: A good battery for the Pi 3B+?

Sun Nov 04, 2018 9:19 pm

dchislop wrote:
Sun Nov 04, 2018 8:12 pm
I've been trying to work portable as well, I had no luck with 4x1.2Volt rechargeables or even 4x1.5Volt AA batteries. They didn't have enough power to even boot up the Pi 3. I even tried a 5.1Volt Zener Diode circuit but didn't work either. I now trying a 6Volt sealed lead acid battery from Toolstation priced £6.38, it's rated at 1.2Ah and small too, just 97x24x58mm. It drops to 5.7 Volt once up and running but the voltage soon falls away only giving me a operating time of 15 minutes before the low voltage indicator appears and another 5 mins before conking out completely. I know I should really supply a steady 5.1Volt so I would interested to hear of other solutions.
1.2Ah * 6v = 7.2Wh. On the Pi side, 2A * 5V = 10W, so even at best (100% conversion, batter is able to supply total capacity, etc.), you would only expect to get 45 mins. Since a Pi3-class device might draw more than that, the battery rating may be...fictional, you can't drain a battery all the way down, and no voltage converter is going to be 100% efficient, 15 to 20 minutes is reasonable.

I have to restrain myself... The analysis needed here is basic electrical theory. It isn't rocket science (which is good, because I'm not a rocket scientist). Just convert all activity to Watts (W) and capacities to Watt-hours (Wh) and the math becomes simple. Allow for a generous dollop of losses and you'll be reasonably close. Things like this are why engineers are conservative and allow "margin for error" in specifications.

And, for those watching at home, the bit about giving LiPo battery "capacities" in Ampere-hour (Ah) or milliAmp-hour (mAh) is *advertising*. It gives the impression that the battery is more capable than it really is. The same is true of commercial USPes, where the rating is given in Volt-Amperes (VA) or Kilo-Volt-Amperes (KVA). In AC systems, you have to take the time average of voltage and current, which are sine waves. The true power out (assuming 100% conversion efficiency) is the Root Mean Square (RMS value of the peak-to-peak value. So to find out how much power a UPS will deliver, multiply the VA or KVA by (1/2)*sqrt(2), or close enough to 70% to use that. Thus, a "1 KVA" UPS should provide 700 W.

drgeoff
Posts: 9743
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Re: A good battery for the Pi 3B+?

Sun Nov 04, 2018 9:27 pm

dchislop wrote:
Sun Nov 04, 2018 8:12 pm
I've been trying to work portable as well, I had no luck with 4x1.2Volt rechargeables or even 4x1.5Volt AA batteries. They didn't have enough power to even boot up the Pi 3. I even tried a 5.1Volt Zener Diode circuit but didn't work either. I now trying a 6Volt sealed lead acid battery from Toolstation priced £6.38, it's rated at 1.2Ah and small too, just 97x24x58mm. It drops to 5.7 Volt once up and running but the voltage soon falls away only giving me a operating time of 15 minutes before the low voltage indicator appears and another 5 mins before conking out completely. I know I should really supply a steady 5.1Volt so I would interested to hear of other solutions.
RPi models except the Zero and ZeroW have an overvoltage diode which attempts to protect the onboard circuitry. When well charged the voltage of your 6 volt SLA is too close for comfort to the activation point of that diode.

There is currently no cell chemistry which can provide a battery which can be connected directly to a RPi and produce the specified 5 volts for a useful portion of its discharge time. You should always use active circuitry to convert the battery voltage (which varies) to 5 volts for the RPi. USB powerbanks contain such circuitry. They also contain charging circuitry and protection from overcharging and overdischarging. Lithium cells do not take kindly to electrical or mechanical abuse. Loss of property, limb and even life are not out of the question.

dchislop
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Re: A good battery for the Pi 3B+?

Mon Nov 05, 2018 12:52 pm

I will try out a UBEC, Universal Battery Eliminator that they use in drones, they also require 5.1 Volt. It will be interesting to see if it can power my Raspberry.

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Imperf3kt
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Re: A good battery for the Pi 3B+?

Mon Nov 05, 2018 8:56 pm

dchislop wrote:
Mon Nov 05, 2018 12:52 pm
I will try out a UBEC, Universal Battery Eliminator that they use in drones, they also require 5.1 Volt. It will be interesting to see if it can power my Raspberry.
Generally, to a degree.
From my research, they get hot and waste a lot of energy.
Try to get one rated for at least 4 amps
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boomonster
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Re: A good battery for the Pi 3B+?

Fri Nov 09, 2018 3:13 am

I briefly tried making a laptop with my pi (wooden case, wireless keyboard + mouse)
and I used an Aukey 20000 mAh power bank (find it on amazon), which had 2 ports,
a 1 amp port, the other 2.1 amps. It worked with my Pi 2b, but I constantly got the lightning
bolt warning and some flickering pixels.

As for emulation performance, I TRIED to use Windows 98 SE on it, but it was so slow
that I coulden't even use the desktop before Qemu froze up... :lol: I had to close the window.

That power bank cost $50 CAD, however. It could last me for probably 6-8 hours running
a 7" adafruit screen with my pi 2b... I would get one more powerful.

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