# 12s5p 30Qs charge rate?

I promise I have tried to search for this, but with no luck…

I’m doing my best in building a 12s5p battery with Samsung 30Qs. All info I find says I should be able to charge this pack with maximum 15A rate - but this seems really high, even for this size pack. My BMS is 12s 60A version from eBay, and I’m looking at this charger. Any inputs? (pun intended)

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look at the datasheet for samsung 30q

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While 15A for the whole pack itself should indeed be fine, you need to make sure your balance wires can withstand that much current, even if you go with 10A.

There are some stories here on the forum of people melting their balance wires and BMSs while charging even at 8A.

Hmm - good point.They are very thin. This is the BMS I got, it states in the text: “Max Continuing discharge Current : 60A Max Charge Current : 30A”

Sorta the reason I bought it, but china-ware isn’t always very reliable. Any way to test this before hand?

I got chargers… And details there about wiring… 4amp max per cell… × 5 = 20amp charging potential… But as others mentioned making sure the wiring can.handle it… Input charge port should be atleast 20awg… And a proper connector =)

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generally speaking liion max charge rate is 0.5c, so 7.5a per cell for 30q.

that means your 5p pack should be able to accept a charge rate of 37.5a. so if you can find a charger than can do 2000 watts (50.4v * 38amp) then go right ahead.

whatever your charge rate is in amps, divide that by 5. that’s your per cell charge rate.

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0.5c -> 0.5 * 3000mah=>1.5A each cell -> 1.5*5p= 7.5A

7.5A*50.4=378watt

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7.5a per cell * 5p = 37.5amp

37.5amp * 50.4v = 1890watt, round up 2000

Not true. Charging does not take place through the balancing leads. In most BMSs the balance leads only bleed current to balance the cells. Charging is done via the - and + poles of the whole pack so you just have to make sure your charging leads and BMS can withstand the charging current. eg If you are using a Bestech D140 your maximum charging current is 15A whereas with a D223V1 it is 20A provided all the other components (wires, connectors etc) can take it.

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ehm…what? 30Q has 4A Max Charge. So i don’t know where you get those numbers from.

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oop, you’re right.

official spec sheet says 4a

i got .5c from this: https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

so for 5p pack, at 4a per cell, max pack charge rate would be 20a.

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I didn’t mean to imply that, but I can see why you interpreted this way.

I guess the takeaway is it’s generally good practice to upgrade the balance wires if you intend to charge at high currents.

Why? As I wrote the balance leads will only see the BMS discharge current which is 100-200mA for most BMSs

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0.5c means 0.5* the capacity. the capacity of a 30q is 3000mah=3Ah… 0.5c * 3Ah stays still 1.5A

I know the 30q can take 4A, that is the fast charging.

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damn, i was wrong again. i mistook C for discharge, but you’re right, C is capacity.

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Why do you need to charge at the max rate? A 4a 50.4v charger will charge a 12s5p pack in under 3 hours with 18awg wire. Working to charge faster than that you are asking for trouble and certainly a short pack life.

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i wouldn’t charge at max rate. hell, i still use a 2amp charger.

but i think the original question was max charge rate for 30q.

sup dave.

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Since the standard charge current for 30Q cells is 1.5A going to 5x1.5A=7.5A will not compromise cell life. Of course finding the proper charger and connector is another story. Personally I would like to have a 15A charger for those times I need to use the board at the last minute and as usually it sits at 50-70% charge. All the other times a slower charger will be the one I use.

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https://batteryuniversity.com/index.php/learn/article/ultra_fast_chargers

bet you can charge with very high current when the cells are at a low state of charge