Battery pack info

hello all here,

sorry for my bad english, i am from holland.

i want to make a 7s14p /… 29,4v/37,5A aacu pack for my scooter, which pull 16A .

i have a few questions to make sure i make the right one.

what i now have my old pack 22x Nimh cell.
i already orderd the bms 7s 30A
i want to make the pack with the 25r samsung 18650 batteries because they can draw 15A, but i thougt later when they are 14p then the motor only pulls around 1A per cell is that correct ?

the battery charger gives 8A that would not be a problem ? i did the calculation from this site 7s14p-- 14 x (2500/3000) = 11,66 A can someone say that’s right

sorry for the silly questions, i will make the pack with the kweld spot welder…

thx Marco

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He so not really sure what you are saying but with a 25r pack you would be able to have a massive amount of range and current since it is 14p

To work out ah of the pack you do 2500x14

To get max constant discharge you do discharge of a single cell x 14

Charging at 8amps will be fine for this pack

The current drawn is determined by the load. No matter what battery, the motor and esc will try to draw all it needs. if you have 14p based on a cell that can do 15A you have max. cont. draw of a butload(15x14). So you’re fine there.

You’ll probably need to wire the BMS as bypass tho. Charger should be fine aslong as its made for 7s Li-on. You can not use the charger for your Nimh cells to your Li-on pack (unless specified). The distributor of the BMS probably have an appriopriate charger.

okee thank you for the quick reply,

it is actuallie for a onderwaterscooter , so for the original nimh pack i can only do one hour , so with this pack i will do almost 3 hour on full power.

the battery will do actuallie 20A max per cell,
is it correct that when the motor pulls 16 A from the pack from each battery it will only pull around 1A ?

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Yes if the motor only pulls 16a then the it will pull just over 1amp per cell

so i can actuallie do a cell that can do less discharge current, its a bit over rated or do you think it will be beter for the batteriy to have a higher discharge current, maybe a longer life for the cell ?



So if the max you will ever need is less then 20amps I would advise a cell called the samsung35e

It has 3500mah so more capacity and 8amps discharge which in 14p would be way more then you need also you can buy them for 2-2.5$ per cell

You sure about that? That’s a really big pack. At 15A discharge you’re gonna have like 50 mi range
You could save a ton of weight.

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Most Nimh charger iv come acros are not suitable for lithium ion because thay are normally a cv You need a constant current constant voltage charger for lith ion

Cell wise thay would work fine but your could get larger capacity ones, with longer life span, that are cheaper.

Not quite 25r are 2500mA Ish (from memory) that’s 2.5A*14P=35A you can’t take 35amp decided by max load because you need to consider duty cycle and rpm. As a very rough idea I’d guess it last more 6hour ish

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If you read the entire sentence you’ll see that I agree with you.

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Sorry you’r correct I missed that

i know to get a new charger i was looking for somthing like this

the weight is not a issue, because i need to make the total pack around 6 kg , the same as the nimh pack, this is because else my underwater scooter will only float :grin:

Do you have a picture for this spectacular invention?

That charger looks alright. Those cheap chargers on ali/ebay are abit of a gamble tho. Some last forever, some seem to just die or not charge properly. Some are super noisy on the fan.

Might be worth to check different suppliers if you want something that lasts

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That will take 5 hours to charge the battry


Should be 1 1/2h charge

While that is a very nice charger, it’s not the correct one. You need atleast 29.4V on output.
The one you linked only goes up to 24. You’ll need the HLG-600H-30 or HLG-600H-36 (check table in datasheet)

this one :smiley:


nice, thats some James bond shit


Defaulted to 24v with out thinking got some hiding around hear. 36v one only goes down to 30.2V so still to much

James Bond would have been faster

Ah yeah thats true, if the BMS controls the final voltage its fine tho (like the diebims for instance).
the HLG-600H-30 should be the one then :slight_smile:

so its the same like ali :sweat_smile: