Need to couple my device with a back-up battery

Thread Starter

morzh

Joined Jan 18, 2017
26
Hi!

What I need to do is to couple my device (a table-top optical fiber-processing tool) with a back-up battery that should be enough for a full shift operation (8hrs). This makes it about 3,000-4,000 mAh @ 12V. A regulated 12V.
So the batteries should be being charged while device is operating from an AC/DC tabletop power supply (your typical 1-2A 12V adapter) and should the power plug be removed, the battery pack should take over.
Due to the device being not very large, the battery pack should also not be large/heavy, so I am looking at some variety of LiON cells.

This is where my expertise is lacking. LiON batteries for me is murky thing with regulations, shipping restriction, controllers etc etc.
So I am looking for some advice from those who have been through it.

From recommending the type of LiON, method of controlling it, charging it, holding it etc.

PS. The battery pack should go inside the device and not be an external pack with a battery charger bought from Amazon. (in essence, a new mechanically and electronically re-designed device will result).

Best

Mike
 

Yaakov

Joined Jan 27, 2019
1,612
To help, we'll need more information including dimensions and current draw (not in AH, but in peak and continuous A).
 

Thread Starter

morzh

Joined Jan 18, 2017
26
To help, we'll need more information including dimensions and current draw (not in AH, but in peak and continuous A).
Yaakov,

Yes we are (electronics-wise, I am as the only EE here) the manufacturer of the device. Our devices so far have not crossed into the "portability" realm; they are lab-grade table-tops. Which does not necessarily mean they are huge (some are, some not).
This particular device is about 10"x5"x5" box.
We do not intend to make a "portable" device meaning "usable in the field", but we want an operator to be able to move anywhere within a building where the device is being used (workstation to workstation) without having to necessarily plug-unplug to/from Mains.

It draws not above 400mA @ 12V with all motors running (330mA as I remember). Which to me means 3Ah is enough; to be on the safe side maybe 3.5Ah. In fact we've tested it with 3000mAh 12V "sigaret pack" size pack and it was performing fine after 8hrs without degradation of performance.

Oh....the dimensions will be increased (the box re-designed, the battery holder + charging circuitry etc added) as needed.
 
Last edited:

Yaakov

Joined Jan 27, 2019
1,612
Broadly speaking, then, I would say you are probably best off with an off the shelf BMS module and a 4S cell LiPo pack.

Only for example: https://www.amazon.com/dp/B07CYRTBQY and https://www.amazon.com/4S-Battery-Protection-Capacity-Tester/dp/B073STX56L/

Once you have a good idea of what you want to do, you could make your own BMS and get a bare pack, but these are well tested designs with standard connectors.

I don't know how price sensitive you are, but you can certainly reduce the cost after development.
 

Thread Starter

morzh

Joined Jan 18, 2017
26
Yaakov

Thanks. Oh...did I say, I'd like to avoid the "copter" batteries capable of 50C currents....... :) Too dangerous.
Price-sensitive......somewhat. We are not large number manufacturer (expensive device / lower numbers). So if I could design something on a dime (meaning 100 bucks) in qty of 100, that would be acceptable. Of course, the lower the better.

Speaking off the shelf - depends on off whose shelf. If it is Amazon / Ali Baba...I'd like to stay away. It's always better owning the design.
 

Yaakov

Joined Jan 27, 2019
1,612
You aren't going to avoid high currents with LiPo batteries, the obvious candidate, or even 18650 cells, another possibility. The BMS design isn't trivial, but you can get the chips to make it work.

I don't know exactly what advice you are looking for. I can say, "use LiPo in a 4S configuration" and "use an NVD601 type chip for the BMS" https://www.ablic.com/en/doc/datasheet/battery_protection/S8254A_E.pdf

Is that helpful? If build your own pack, you'll have to buy cells, and decide on connectors, and you will need a balance connector for the BMS.

Even if you want to roll your own BMS, you might want to reconsider making your own pack. In any case, the battery you want is going to have a lot of power in it. You can always fuse it, but you can't keep out the electrons, you need them.
 

Thread Starter

morzh

Joined Jan 18, 2017
26
This might be more to your liking, you can work with a company like Energy, and you will pay a premium but it's not Amazon nor Alibaba:

https://power.tenergy.com/at-tenergy-li-ion-18650-14-8v-2200mah-stick-rechargeable-battery-pack-w-pcb-4s1p-32-56wh-4a-rate/

A little over 10" long, very low profile.

You still need a BMS, but Tenergy might be able to help point you in the right direction.
Thanks, could be. No, I don't intend building my own battery pack; I know it is onerous.

So why not just use that battery pack?
SG
I would love to. Somehow the bosses don't see it as a good-looking solution.
 

Thread Starter

morzh

Joined Jan 18, 2017
26
One helpful thing would be to make the battery user installable and ship it separately.

You should talk to your logistics or shipping company for more details about what they require in particular.
yes, this was the latest thought - this is why that cigarette pack thing I found, I made sure it is sold around the world and could be bought and installed by the user.
 

Yaakov

Joined Jan 27, 2019
1,612
yes, this was the latest thought - this is why that cigarette pack thing I found, I made sure it is sold around the world and could be bought and installed by the user.
You recognize that is also true of standard "hobby" packs? And they are solidly connectorizedz as well.
 

Thread Starter

morzh

Joined Jan 18, 2017
26
So.....a bird-eye view: when I plug a power supply in my device, with battery present, it should be able to make the system run while charging the battery. With the power supply unplugged, the system runs off the battery.

Pretty much like a laptop, except the current draw is about 400mA.
 

Yaakov

Joined Jan 27, 2019
1,612
I mean the prismatic LiPo packs, like the one I linked.

Tenergy can build those too, but they want a lot for them.
 

Yaakov

Joined Jan 27, 2019
1,612
Once more thought: use 18650s, and provide a battery holder for protected cells. Harder to design the case but much easier for the end user to supply and install.
 

Thread Starter

morzh

Joined Jan 18, 2017
26
When you say "protected battery holder", does it mean it is intended for protected batteries/that 18650 is a protected cell (doubt it, the pack will probably need a BMS) / or it has space for protection circuitry?
 

Yaakov

Joined Jan 27, 2019
1,612
When you say "protected battery holder", does it mean it is intended for protected batteries/that 18650 is a protected cell (doubt it, the pack will probably need a BMS) / or it has space for protection circuitry?
I mean a cell with a protection circuit builtin, they are a bit longer so you need to be sure the cell holder can accommodate that. It adds safety as well. You would still need a BMS solution, but you might not need a balancer.

It wouldn't be a bad solution. You'd need high capacity 18650s, but it would be easy from the user perspective.
 
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