I'm looking for some model of mini ups that can accept the AA Ni-MH batteries....

[ziomario]

Hello to everyone.

I'm trying to create a tablet made only with independent and replaceable hardware components. I'm looking for some model of mini ups that can accept the AA Ni-MH batteries. At least one,so that I can search more of them by myself by using the correct key words and features explained on the (amazon or whatever online shop) link. My hope is to find one that has a depth a little bit less than 2 cm. That's the size that I think acceptable for not having a brick instead of a tablet. The tablet that I'm trying to assemble has these fundamental hardware components :

1) soc = Rockchip RK3399Pro
2) display = https://www.waveshare.com/8hp-caplcd-monitor.htm

 

[DirtyDingusMcgee]

Perhaps? https://www.tindie.com/products/net4web/akku-batteriehalter-holder-fur-for-8xaa-12v-con/

check out

https://alchemy-power.com/

https://www.tindie.com/

https://www.pisugar.com/

 

[ziomario]

Thanks,but a depth of 7,5 I don't create a tablet,but a brick. Its not good.

 

[LabRat 891]

"OpenUPS"
IIRC, the project is set up for lithium and SLA chemistries.

OpenUPS

OPEN-UPS was designed to provide user specified regulated power output from a wide input voltage, battery backup, multi-chemistry charging and cell balancing in a single PCBA

www.mini-box.com

Alternatively, any USB-PD supporting 'AA Power Bank' should be able to output the voltage needed.

 

[ziomario]

"OpenUPS"
IIRC, the project is set up for lithium and SLA chemistries.

OpenUPS

OPEN-UPS was designed to provide user specified regulated power output from a wide input voltage, battery backup, multi-chemistry charging and cell balancing in a single PCBA

www.mini-box.com

Alternatively, any USB-PD supporting 'AA Power Bank' should be able to output the voltage needed.

I'm not experienced and I don't understand if the OpenUPS solution requires that I make some kind of soldering or not. How the batteries are supposed to be connected to the OpenUPS board ?

Please can u provide a link where I can buy one USB-PD 'AA Power Bank' board ? thanks.

 

[LabRat 891]

I'm not experienced and I don't understand if the OpenUPS solution requires that I make some kind of soldering or not. How the batteries are supposed to be connected to the OpenUPS board ?

Please can u provide a link where I can buy one USB-PD 'AA Power Bank' board ? thanks.

My apologies. The power banks I was thinking of took 18650 lithium cells, not AA NiCad/NiMH cells. The AA-supporting banks I can find, are all 'dumb' (unregulated) or 5V (regulated) only.
Sadly, since the proliferation of lithium battery technology, AA, AAA, etc. cells have practically become a 'legacy' battery form factor...


At this point, a Lithium power bank would be a more-affordable solution to your power needs.
I respect the design-goal of using common modular cells (that you probably have an ecosystem of, already). However, I doubt you'll find the 'perfect' off-the-shelf solution.

Kitbashing or homebrewing are your options, if the AA cells are a must.

 

[dragontamer5788]

NiMH is the wrong technology for UPS. Lead Acid is the best tech for this. There's a huge number of standardized Lead Acid batteries that have significantly more power-storage than any combination of AA cells you link up together.

If you need the portability of NiMH (lighter weight and smaller), then unfortunately the technology has moved onto Li-ion rather than NiMH. If you still need NiMH despite the superiority of Li-ion for portable applications (particularly: Li-ion will always be smaller and lighter than an equivalent NiMH), then what you're asking for is a NiMH charge controller.

Part of the reason why NiMH is the wrong technology is that the charge controller is the most complex out of everything. Trickle charge is doable but requires 13-hours+ and over-trickle charging still damages the batteries. So you need to have a microcontroller that has a clock that remembers 1-day to 7-day periods and re-trickle charges, as well as current senses to see when the cells are too low.

-------------

Lead Acid is the better tech for UPS because you just trickle-charge forever. (Lead Acid WANTS to be at 100% charge, unlike all other chemistries. So keeping a trickle-charge at 100% is the best way to keep lead acids lasting as long as possible)

 

[ziomario]

I've just bought this battery pack :

12V 50000mAh Li Ion Rechargeable Battery Pack For CCTV Camera +Charger Portable | eBay

Battery capacity: 50000mAh (50Ah). 1pcs 12V-50Ah lithium battery. Lithium battery knowledge 4 prohibited dismantling, short-circuit the battery, most likely caused by a short circuit. 2: maximum instantaneous current: 10A.

www.ebay.com

it seems perfect with the dimensions,with the protections added to the package and it is very powerful....

 

[dragontamer5788]

At this point, a Lithium power bank would be a more-affordable solution to your power needs.

Even then, Li-ion power banks are not normally built for UPS usage. Li-ion goes bad at higher charges, and having timers / temperature sensors / battery conditioning that keeps Li-ion happy in the face of long-term trickle charging is actually rather hard.

 

[R-T-B]

Thanks,but a depth of 7,5 I don't create a tablet,but a brick. Its not good.

Unfortunately thats kind of the tradeoff with NiMH chemestry. Cheer up, at least its lighter than lead acid. Oh and it tends to live longer (service life) to but that does not help us much here.

I've just bought this battery pack :

12V 50000mAh Li Ion Rechargeable Battery Pack For CCTV Camera +Charger Portable | eBay

Battery capacity: 50000mAh (50Ah). 1pcs 12V-50Ah lithium battery. Lithium battery knowledge 4 prohibited dismantling, short-circuit the battery, most likely caused by a short circuit. 2: maximum instantaneous current: 10A.

www.ebay.com

it seems perfect with the dimensions,with the protections added to the package and it is very powerful....

Looks like a viable one if willing to accept Li-Ion.

 

[ziomario]

Unfortunately thats kind of the tradeoff with NiMH chemestry. Cheer up, at least its lighter than lead acid.


Looks like a viable one if willing to accept Li-Ion.

What are the dis-advantages of the Li-Ion ?

 

[dragontamer5788]

What are the dis-advantages of the Li-Ion ?

For the hobbyist EE? It explodes if you don't use Li-ion correctly.

NiMH will leak hydrogen and destroy itself of course. But the H2 goes away rather quickly and has almost no explosion risk. Meanwhile... an entire industry exists for making bags for Li-ion fires on airplanes.

Lead-Acid and NiMH have virtually no fire-risk at all. Your main fire-risk is standard electronics (miscalculating the resistance of a wire or causing a short, which always increases temperature to the point where a fire could start).

Speaking of which, as an EE hobbyist, you have your fire-extinguisher ready, right? I haven't had a fire since my college lab years but I feel like every hobbyist / beginner EE gets into fire-risks as we are so n00b at this in general.

 

[LabRat 891]

Even then, Li-ion power banks are not normally built for UPS usage. Li-ion goes bad at higher charges, and having timers / temperature sensors / battery conditioning that keeps Li-ion happy in the face of long-term trickle charging is actually rather hard.

Look into LiFePO4 chemistry cells.
Less density, but much better 'durability' and 'tolerance' for abuse in both charging and discharging, with a much longer cyclic lifespan.
-Also, impossible to 'go nuclear' (ie, they can't runaway into catastrophic failure from internal malfunction or physical damage).

 

[R-T-B]

What are the dis-advantages of the Li-Ion ?

If you get them wet, watch out (they tend to runaway violently if exposed to water). Also they tend to inevitably die within a lot less recharge cycles than Li-Ion. But they hold a ton more power for the weight, so... tradeoffs. Most tablet manufacturers choose lithium ion for the weight benefits.

 

[1freedude]

Speaking of which, as an EE hobbyist, you have your fire-extinguisher ready, right?

Mine is called Dave. It keeps everyone calm when the time comes. As in, "I think we need need Dave's help."

On subject...dont abandon AA form factor. Use it as a supplement when things go sideways.

As far as power source, also look at LiFePO4. Much safer and more suited to 12v use. 4 lifepo4 nominal voltage is 3.2v per cell, or 12.8v. Hot off the charger is a bit high, but typical 12v charging methods (and possibly the BMS) will keep this in check. The hot-off-the-charger voltage is still well below 4 Li-ion voltage.

But, as others have said, for use in a commercial UPS, they are not a direct replacement. But if homebrewing from scratch, you can do it.

I have a homebrew Power Delivery UPS in the works. My plan is to use 6 Li-ion in series for 26.1v hot off the charger. The PD I chose will deliver 24v from 10-30 volts. And, I have a ton of AA holders as parallel/swap power.

Have fun!

 

[ziomario]

Give a look at this one :

Baseus Blade 2 Smart Power Bank 65W 12000mAh

Redefine Laptop portable charger with Baseus Blade2 65W PowerBank. Experience 65W fast charging, digital display, and a slim design perfect for your laptop. Shop now!

www.baseus.com

 

[Wirko]

I've just bought this battery pack :

it seems perfect with the dimensions,with the protections added to the package and it is very powerful....

This will disappoint you but your battery pack is nowhere close to 12V/50000mAh. It's obviously made up of six standard 18650 Li-ion cells. Each cell has about 3.7V and 3500 mAh if it's from a good brand such as Samsung (see here). You will burn down your tablet, your house, and your city block *before* you stuff 600 watt-hours into this pack.

 

[ziomario]

ahahahahaha. And what do u think about this one ? --->

https://www.amazon.fr/Baseus-Powerbank-contrôle-Application-Batterie/dp/B0CXS6VT3P

This will disappoint you but your battery pack is nowhere close to 12V/50000mAh. It's obviously made up of six standard 18650 Li-ion cells. Each cell has about 3.7V and 3500 mAh if it's from a good brand such as Samsung (see here). You will burn down your tablet, your house, and your city block *before* you stuff 600 watt-hours into this pack.

@qxp : if I will buy that battery pack my house will explode,bro.

 

[dragontamer5788]

On subject...dont abandon AA form factor. Use it as a supplement when things go sideways.

Actually, I love the AA Format.

Just don't try to build an AA NiMH charger by yourself. Just... buy more batteries and install them.

Like seriously, is it really that hard for you to pull the batteries out and install new ones in whenever you need them? Why do you need to charge AA batteries while they're inside the device? By a charger (even a $10 trickle charger), and just swap AA Cells out.

If you need 12V that's 12x NiMH (they have 1.2V nominal for the bulk of their life. But will be 1.35 or 13.5V when freshly charged). So just pull out those 12 AA cells when you're done, and put new ones in.

Buy 24 cells and a big enough group charger to charge all of those 12 cells.

----------------

Uggggh. 12V really?

PS-1212 - 12V 1.4Ah Rechargeable SLA Battery

Power-Sonic PS-1212, a quality 12.0V 1.4Ah SLA rechargeable battery with F1 terminal. Fast Delivery. In Stock Now!

batteryinthecloud.com

Its just that Lead Acid is so cheap and good for this use-case. Its probably cheaper to buy 1x 12V Lead-acid battery rather than 12x AA NiMHs, and really you'd need 3x copies of that anyway. (While you're using one, you should be charging the other two).

Look into LiFePO4 chemistry cells.
Less density, but much better 'durability' and 'tolerance' for abuse in both charging and discharging, with a much longer cyclic lifespan.
-Also, impossible to 'go nuclear' (ie, they can't runaway into catastrophic failure from internal malfunction or physical damage).

Right. LiFePo4 is the new tech that's finally getting cheap enough to consider. I don't know much about them though, but good point bringing them up.

LiFePo4 is becoming very popular as a Lead-Acid replacement however. So if you're working on Lead-Acid batteries, then these LiFePo4 batteries are in the _exact_ same shape and form factor.

You can find a 12V 7Ah Lead-Acid... and in the exact same weight / sizes, you can find 12.8V 7Ah LiFePo4. LiFePo4 is more expensive but should have far more endurance than any Lead-Acid.

 

[ziomario]

Actually, I love the AA Format.

Just don't try to build an AA NiMH charger by yourself. Just... buy more batteries and install them.

View attachment 381877

Like seriously, is it really that hard for you to pull the batteries out and install new ones in whenever you need them?

When you use your tablet or your phone how many times you need to pull the batteries out and install new ones in ?
Anyway,please share an AA form factor battery enclosure that has a depth lower than 2 cm that has a cable that I can connect to the barrel connector of the board + the link for buy the proper batteries to use with that. I have bought this one :

https://www.amazon.co.uk/Yushu-Universal-Battery-Mobile-Charger/dp/B09ZQFQLSW

but it has a depth of 2.7 cm and it cannot fit inside the enclosure.

Very thanks.

 

[Wirko]

Give a look at this one :

Baseus Blade 2 Smart Power Bank 65W 12000mAh

Redefine Laptop portable charger with Baseus Blade2 65W PowerBank. Experience 65W fast charging, digital display, and a slim design perfect for your laptop. Shop now!

www.baseus.com

Are you looking to buy one and use it as power supply for your tablet? Or are you just wondering what's inside? Here's a teardown of a similar Baseus power bank, not the thinnest one though:

 

[qxp]

@qxp : if I will buy that battery pack my house will explode,bro.

From a battery pack - probably unlikely, unless it is really big. You could get a fire, especially if you buy too many questionable Li-Ion batteries. But I remember reading about explosions in California, when people were playing with hydrogen energy storage in a garage. I tried to find a link, but turns out there were many more hydrogen explosions in California since, at many alternative energy firms, and the link got lost in entropy. Hydrogen has a very wide range of fuel-oxidizer mix ratios when it explodes, best use it tied to something like a few carbons.

 

[ziomario]

Are you looking to buy one and use it as power supply for your tablet? Or are you just wondering what's inside? Here's a teardown of a similar Baseus power bank, not the thinnest one though:

yeah that's the idea. Check well the video...it's the 100W / 20.000mAh model,that's not as thin as the 65W / 12.000 Mah model. This model has less that 1 cm of depth. The first one can't fit inside my enclosure,the latter can. Not sure if 65W / 12.000 mAh is powerful enough for my board and how long can it last.

 

[Wirko]

yeah that's the idea. Check well the video...it's the 100W / 20.000mAh model,that's not as thin as the 65W / 12.000 Mah model. This model has less that 1 cm of depth. The first one can't fit inside my enclosure,the latter can. Not sure if 65W / 12.000 mAh is powerful enough for my board and how long can it last.

If that's important, do a triple check of the thickness, and also try to measure from the available photos. Baseus' own site says 0.4 inch (but 7.3 mm "at its thinnest edge"). It's from China *shrug*. The Nitecore NB10000 might be another option, it's 10.6 mm thick (but triple check that too). Or maybe something else from this list at Geizhals if it's available for you to buy.

There's something that might make power banks unsuitable for your application, though. They are basically intended to charge phones etc. When there's no load, or the load current drops below certain level, they tend to turn off after a while, to conserve their own battery. Some of them have a special mode that keeps them from powering off. You'll have to check the user manuals and reviews to see if that's the case.

 

[ziomario]

If that's important, do a triple check of the thickness, and also try to measure from the available photos. Baseus' own site says 0.4 inch (but 7.3 mm "at its thinnest edge"). It's from China *shrug*. The Nitecore NB10000 might be another option, it's 10.6 mm thick (but triple check that too). Or maybe something else from this list at Geizhals if it's available for you to buy.

There's something that might make power banks unsuitable for your application, though. They are basically intended to charge phones etc. When there's no load, or the load current drops below certain level, they tend to turn off after a while, to conserve their own battery. Some of them have a special mode that keeps them from powering off. You'll have to check the user manuals and reviews to see if that's the case.

The Nitecore NB 10000 fits perfectly inside the case.
[DEL]But I'm not sure if it is 12v/3Mah. It is not written at all on the page.[/DEL]