The 'new' 1.5V (typically USB-)rechargeable Li batteries - Page 1
Forum section: electronics / general

author: 6SN7WGTB
author_rank: Regular Contributor
timestamp: February 13, 2022, 07:32:34 pm
content: Thought I could find something on this via search but failed, so please redirect me if I missed the obvious.Expensive yes, but aside that seem to be without peer for gear that baulks at the lower voltage of NiMH.Aside what I assume is zero warning of end of life, what am I missing?

author: mariush
author_rank: Super Contributor
timestamp: February 13, 2022, 07:52:53 pm
content: Can be lower capacity than actual ni-mh rechargeable batteries, because they have to squeeze a dc-dc converter and a lithium battery charger and a usb jack inside the cell.So for example, you could have a 2600 1.2v...1.35v mAh ni-mh battery, or a 600mAh 3.7...4.2v with conversion to 1.5vThe dc-dc converter inside that converts 3v-ish ... 4.2v to 1.5v will have some idle/quiescent current (very little but not 0), so battery will discharge over time...Same converter have some conversion losses, efficiency will vary depending on current - i would guess something like 90-95% efficient when used in some high current applications (ex 100mA or higher), probably less efficient if used in some low current applications ( ex wall clock, clock backup on a radio, etc )If they're really bad designs, there may be issues with some applications like remote controls for example, which consume basically nothing and when you press a button they push 2+ amps in the infrared led for a few ms to send the code to TV.Then there's also the issue of making battery levels pointless ... because the regulator will keep outputting 1.5v until the battery is depleted ... so you discharge down to 3v or whatever the cutout point and the battery instantly stops working.

author: 6SN7WGTB
author_rank: Regular Contributor
timestamp: February 13, 2022, 08:03:33 pm
content: Thanks.Yes I did think the short-duration high-drain applications might prove troublesome.Might be good in my VTVM though for ohms range... ...only because it's far less likely to leak than an alkaline D cell.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 13, 2022, 08:33:31 pm
content: If the device in question is sensitive to such things there is also the EMI concern of putting one or more cheap buck regulators into the mix.EDIT: For a VTVM I'd probably just use a Panasonic carbon zinc battery, in my experience they don't leak nearly as often, badly, or destructively as alkaline. That or AA/AAA lithium in an adapter as suggested below, if the higher voltage (something like 1.8V open circuit) is workable.

author: edpalmer42
author_rank: Super Contributor
timestamp: February 13, 2022, 10:09:07 pm
content: You're not missing anything. That's the way most of them work. However, there is one brand, Jugee, that drops the output voltage from 1V5 to 1V1 when there's about 10% capacity remaining. This gives you some warning that it's time to recharge. There's a video on youtube that says that Jugee batteries don't work very well, but he didn't mention that feature so I don't know if he even recognized that it existed.Another thing to keep in mind is that all these 'USB batteries' have a maximum output current limit that's typically in the 1 - 3 amp range. If you try to draw too much current weird things will happen.There are many other videos on youtube that give pros and cons to different brands.As for your VTVM, I think it's overkill to use one of these batteries. I'd recommend a non-rechargeable 1V5 lithium AA cell that you can buy in any drug or hardware store. If necessary, put it in a plastic holder to bulk it up to the size of a D cell. You might find that the voltage is too high to zero the meter so a few tweaks to the circuit might be required.Ed

author: ralphrmartin
author_rank: Frequent Contributor
timestamp: February 14, 2022, 04:26:38 pm
content: Quote from: 6SN7WGTB on February 13, 2022, 07:32:34 pmThere are also NiZn batteries, which are rated at 1.6v.