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zbitx batteries, safety and monitoring

 

I hope the zbitx will have reverse voltage protection this time? Since it might be too easy to install batteries the wrong way around.

I hope it will have a way to monitor its own input voltage. I would prefer to shut down the radio gracefully before it’s too late, and can probably figure out how to put a battery indicator somewhere visible on the UI (such as a tray icon) if that’s not already done. As it is, when I operate the sbitx from laptop batteries, I don’t get any warning unless I’m monitoring the voltage externally; 9v is pretty low but still working, but at some point a few minutes after it gets down that low, the DC/DC converter cuts power to the pi, while transmitting of course. So for portable use I sure wish I didn’t need an external voltmeter to keep from discharging the batteries that far.

And what about using LiFePO4 batteries? They have a reputation for enduring many more charge cycles. (And also safer, and lower energy density.) But the voltage is 3.2 instead of 3.7. 18650 with 2500mAh capacity apparently exists but is hard to find. 2200mAh here: Sag under load might be about 0.1V per cell; and by the time the voltage reaches 6V for both, they are probably discharged quite a bit, from what I read. So can the zbitx really operate all the way down to 6V? If the 5V regulator is linear LDO, it should even be more efficient at a lower voltage, right?
 

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The zBitx has a DC in jack, allowing you to use whatever external power source you want.

If I remember correctly, the battery clips are sized for the 18650 batteries that have polarity identity (a bump on the positive end, like a dry cell battery), so I don't think the reverse polarity from the batteries is unlikely thru the battery clips.

The schematic has been posted, I'm certain it will answer your question regarding reverse polarity protection:


Ken, N2VIP

On Jan 7, 2025, at 14:45, Shawn Rutledge K7IHZ <social@...> wrote:

?I hope the zbitx will have reverse voltage protection this time? ?Since it might be too easy to install batteries the wrong way around.

I hope it will have a way to monitor its own input voltage. ?I would prefer to shut down the radio gracefully before it’s too late, and can probably figure out how to put a battery indicator somewhere visible on the UI (such as a tray icon) if that’s not already done. ?As it is, when I operate the sbitx from laptop batteries, I don’t get any warning unless I’m monitoring the voltage externally; 9v is pretty low but still working, but at some point a few minutes after it gets down that low, the DC/DC converter cuts power to the pi, while transmitting of course. ?So for portable use I sure wish I didn’t need an external voltmeter to keep from discharging the batteries that far.

And what about using LiFePO4 batteries? ?They have a reputation for enduring many more charge cycles. ?(And also safer, and lower energy density.) ?But the voltage is 3.2 instead of 3.7. ?18650 with 2500mAh capacity apparently exists but is hard to find. ?2200mAh here: https://eu.nkon.nl/rechargeable/li-ion/18650-size/jgne-18650-2200mah-6-6a-lifepo4-3-2v.html ?Sag under load might be about 0.1V per cell; and by the time the voltage reaches 6V for both, they are probably discharged quite a bit, from what I read. ?So can the zbitx really operate all the way down to 6V? ?If the 5V regulator is linear LDO, it should even be more efficient at a lower voltage, right?
 

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I didn't see anything that obviously looked like battery protection.? I'd be pretty concerned about undervolted batteries and reverse polarity.? There should be some sort of BMS when using 18650s, but I didn't see anything on the schematic.?

From: [email protected] <[email protected]> on behalf of Ken N2VIP <ken@...>
Sent: Tuesday, January 7, 2025 12:58 PM
To: [email protected] <[email protected]>
Subject: Re: [BITX20] zbitx batteries, safety and monitoring
?
The zBitx has a DC in jack, allowing you to use whatever external power source you want.

If I remember correctly, the battery clips are sized for the 18650 batteries that have polarity identity (a bump on the positive end, like a dry cell battery), so I don't think the reverse polarity from the batteries is unlikely thru the battery clips.

The schematic has been posted, I'm certain it will answer your question regarding reverse polarity protection:


Ken, N2VIP

On Jan 7, 2025, at 14:45, Shawn Rutledge K7IHZ <social@...> wrote:

?I hope the zbitx will have reverse voltage protection this time? ?Since it might be too easy to install batteries the wrong way around.

I hope it will have a way to monitor its own input voltage. ?I would prefer to shut down the radio gracefully before it’s too late, and can probably figure out how to put a battery indicator somewhere visible on the UI (such as a tray icon) if that’s not already done. ?As it is, when I operate the sbitx from laptop batteries, I don’t get any warning unless I’m monitoring the voltage externally; 9v is pretty low but still working, but at some point a few minutes after it gets down that low, the DC/DC converter cuts power to the pi, while transmitting of course. ?So for portable use I sure wish I didn’t need an external voltmeter to keep from discharging the batteries that far.

And what about using LiFePO4 batteries? ?They have a reputation for enduring many more charge cycles. ?(And also safer, and lower energy density.) ?But the voltage is 3.2 instead of 3.7. ?18650 with 2500mAh capacity apparently exists but is hard to find. ?2200mAh here: https://eu.nkon.nl/rechargeable/li-ion/18650-size/jgne-18650-2200mah-6-6a-lifepo4-3-2v.html ?Sag under load might be about 0.1V per cell; and by the time the voltage reaches 6V for both, they are probably discharged quite a bit, from what I read. ?So can the zbitx really operate all the way down to 6V? ?If the 5V regulator is linear LDO, it should even be more efficient at a lower voltage, right?
 

something like this would kill a few birds with one stone.?
https://www.aliexpress.com/item/1005006860598580.html
 

On Jan 8, 2025, at 06:41, David T-- VE3TOS via groups.io <digiital@...> wrote:

something like this would kill a few birds with one stone.
Yeah. So I bought the 9V version of that: I hope it’s really ok to give the radio 9V. Maybe that’s the upper end of the range it can support? And then maybe it would be ok to use LiFePO4 cells with that step-up circuit. It arrived, and I can confirm that the contacts are open, so they would work fine with flat-tops; and they’d better be 65mm long: 70 would be too long to fit (unless perhaps mashing the contacts down really flat).

Looks like I’ll have to design a 3D-printed case for it to mount on the radio. That’s fine.

I didn’t buy batteries yet, because it’s still ambiguous whether the radio’s included battery holder is better for button-top or flat-top cells, isn’t it? But the picture on the update that was just sent (the only picture I can see in that update!) is showing flat-top ones. "Aspire 2900mAh" seem to be intended for vaping, to such a degree that all the web sites are asking for confirmation that I’m 18 and then not showing tech specs very well.

From what I read so far, if you want LiPo, Panasonic NCR18650BD seem to be one of the best values: 3180 mAh, new safer chemistry first released in 2020, tested for surviving a lot of charge cycles, and Panasonic generally makes some of the best quality batteries (speaking of which: I bet the radio could alternatively run off 6 Eneloops in series, but that would be bulky). Anybody have any better recommendations?

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