Battery Sanity Check

[lxskllr]

I use a couple of these at work to power some gear...

As you can see, they come with male and female plugs, and you use the wallwart to charge them. Do you see any issue in taping two batteries together, and connecting a male to a female to double the capacity, and hooking the wallwart to one battery to charge both(though it should of course take longer)?

 

[BoomerD]

That would double the voltage at the output...not just the capacity. You'd want them connected in parallel, not in series...right?

https://www.batterystuff.com/kb/articles/battery-articles/battery-bank-tutorial.html

 

[cbrunny]

Well, me personally, I see no problem with it whatsoever. I have zero experience manipulating batteries and I also do not understand the physics of batteries. My understanding of electricity is that of a lay-person. But I see no issue whatsoever. I'm pretty sure that most electrical tape will hold.

 

[lxskllr]

That would double the voltage at the output...not just the capacity. You'd want them connected in parallel, not in series...right?

https://www.batterystuff.com/kb/articles/battery-articles/battery-bank-tutorial.html

Both connectors are center post+, so I'd be going ++/--. I think my biggest concern is charging logic. I wonder if there's any circuitry that would be affected by doubling up, especially since they're cheap Chinese parts. I've been using them individually for awhile, and so far have only had a cable failure, but still... A ~20Ah battery failure could be spectacular :^D

 

[BoomerD]

Both connectors are center post+, so I'd be going ++/--. I think my biggest concern is charging logic. I wonder if there's any circuitry that would be affected by doubling up, especially since they're cheap Chinese parts. I've been using them individually for awhile, and so far have only had a cable failure, but still... A ~20Ah battery failure could be spectacular :^D

OK...give it a try...what's the worst that can happen...right?

 

[lxskllr]

OK...give it a try...what's the worst that can happen...right?

It could burn my autographed picture of Richard Stallman that's right above my charging station! D^:








and the rest of the office :^D

 

[BoomerD]

It could burn my autographed picture of Richard Stallman that's right above my charging station! D^:

and the rest of the office :^D

Who?

But yeah...lithium batteries and their circuits can be...touchy.

 

[PottedMeat]

it looks like they have independent protection circuitry

offhand i don't see an issue charging them up individually the first time to minimize the voltage difference, wiring them in parallel, and using them as a dual pack. charging would be done in parallel also.

 

[John Connor]

If you connect both of those together you will get a very hot battery I imagine. I think you're connecting positive to positive and negative to negative. I think it would be analogous to connecting two 9 volts together.


Upon further thought from this tired mind I think it would just be in parallel which jumps the voltage. You want series.

But if you connect like you want it's in parallel and you just double the voltage which will fry your device. If I remember right, in series you increase current and keep the same voltage.

 

[Red Squirrel]

In paralell, I don't think there would be an issue, though where is the charging circuitry, is it right in the battery or in the wall wart? Either way I think it will work just make sure that there actually is charging circuitry and that it's not just dumping voltage straight to the battery.

Now if you want to put them in series it gets more complicated, you need a balance charger.

In paralell you'll keep the same voltage but add up the capacity (amp hours, and general ability to deliver high current). In series you add up the voltage but it will be same capacity.

Technically you can put as many batteries in parallel as you want, they'll self balance. The danger is if one fails badly all the others will try to keep charging it and eventually you just kill all your cells, or if a battery fails short circuit you'll get a North Korean style rocket launch, AKA a RUD.

 

[Charmonium]

You really shouldn't screw around with lithium ion batteries. Whatever charging circuitry you have in each battery is going to calibrated for the output of the wall wart.

So the input current will never exceed a certain level. If the circuitry is set up to only deal with that level of current coming in and you exceed that by having one battery try to charge balance the other, you might exceed that level especially if you have a high drain application.

Besides that, since the direction of flow is always going to be from the wall to the battery, there's never an issue of the charging circuitry having to deal with a reverse flow. In theory, it shouldn't matter but you don't know how the charging circuitry is programmed.

 

[John Connor]

Ah, I got series and parallel wrong.