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I was reading another thread about making an external battery.

 
 

It was talking about a compact BMS like in the picture below.

Can anyone tell me where to get something like this?

Brand, part number any info would be appreciated.

 

57ffeb08da272_BE3.jpg.d620e891f33c7a6eda

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That just looks like a ChargeDoctor (not BMS) with multiple output connectors.  Could also be just one of the Asian V/A meters with connectors added.  Check back in that thread.  External battery has many risks if you do not know much about batteries, battery-packs, and multi-pack systems.  

Edited by FreeRide

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I was thinking about doing a pack with 15 batteries wired in series (15s1p).

Question is, is there even a need for bms as it is only one group?

Would the cells naturally balance during charging?

Or do you need some kind of battery protection?

If so, what would work best for this setup?

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6 hours ago, 68bugboy said:

I was thinking about doing a pack with 15 batteries wired in series (15s1p).

Question is, is there even a need for bms as it is only one group?

Would the cells naturally balance during charging?

Or do you need some kind of battery protection?

If so, what would work best for this setup?

If you have more than 1 battery in series you should have a BMS. You should probably stay away from from this approach.

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1 hour ago, FreeRide said:

If you have more than 1 battery in series you should have a BMS. You should probably stay away from from this approach.

Maybe you are correct.

What approach would you suggest to extend battery capacity?

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21 hours ago, 68bugboy said:

Maybe you are correct.

What approach would you suggest to extend battery capacity?

The approach I use is, extra batteries and hot swap when needed.  I don't necessarily recommend it for others, but it works very well for me. I've discussed in on here before.

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On 7/5/2019 at 8:47 PM, FreeRide said:

The approach I use is, extra batteries and hot swap when needed.  I don't necessarily recommend it for others, but it works very well for me. I've discussed in on here before.

The battery swap method works great!

I was trying to avoid carrying another battery around, but with

a draw-string backpack it was really no trouble at all.

Took all of 4-5 minutes to do the swap.

Easier and safer than building a battery pack.

Here is my next question:

When charging a battery not attached to the unit does the battery still

balance the cells? Or does it need to be connected for the balancing?

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4 minutes ago, 68bugboy said:

....

When charging a battery not attached to the unit does the battery still

balance the cells? Or does it need to be connected for the balancing?

It will balance the cells, but you must leave it on the charger until you get a blinking green light, not the solid green light.  Just like when you charge it on the machine, you must wait for all the segments to be flashing before you remove it from charger.  Sometimes the balancing part can take a while, as you know if you do it while charging in the device.  While tempting some times to remove the charger when it says fully charged,  I balance on every charge and my batteries are still working great.

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On 7/2/2019 at 7:29 PM, 68bugboy said:

Can anyone tell me where to get something like this?

https://fr.aliexpress.com/item/33008439523.html?spm=a2g0o.productlist.0.0.71eb78f9No5zVE&algo_pvid=2b226ee8-d8c3-4f17-b0a6-f247db260786&algo_expid=2b226ee8-d8c3-4f17-b0a6-f247db260786-23&btsid=e354d277-f18b-48ed-92dc-1442c4b693b8&ws_ab_test=searchweb0_0,searchweb201602_8,searchweb201603_53

it's very rare to find a compact 15S BMS, but you can use 16S BMS and make a shunt to the last equilibrate line.

External battery will perfectly work if you add an external plug like I did it how to add an external plug to raise battery capacity for a ninebot mini

Edited by smallexis

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