First dna20d mod- few questions

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gavijal

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Nov 18, 2013
17
1
Zagreb, CRO, EU
Hy! This will be my first dna20 mod and I have few question- If the answers are posted- sorry couldnt find them :)
I thought to go with Panasonic 3400mAh NCR18650B 3.7V Rechargeable 18650 not protected (do I need protected with dna20? ). What are disadvantages of that battery and of 18650 batteries over cellphone stile batteries in general?
What I purchase for now is dna20d chip, EVOLV dna 20D MICRO USB CHARGER BOARD, connestors Prewired 510 Battery Connector, Sealed, Silver 510 Sealed Battery Connector and case for batteries in case I will use 18650 2 Pcs Black 18650 Flat Tip Batteries Battery Holder Case w Wire Leads | eBay.
Did I bought something wrong at this stage?
Sorry, but English is not my mother language , so if I made some grammar mistakes dont shoot me :D:toast:
 

Innocuous

Super Member
ECF Veteran
Mar 23, 2013
508
149
Washington (the desert)
afaik, "protected" would conflict the processor of the DNA20 (or 12) - so, no: use unprotected cells. However, the DNA20 can be killed by a reversed battery. You'll want to find Mamu's "reversed battery protection" thread for the DNA20 if you use a removable cell. If you are building it inside and charging from the USB, then this is unlikely to be an issue.

However, almost all the mods will install a small fuse, too. Read the threads, download the PDF's, read some more.
 

ecat

Full Member
Oct 7, 2013
42
31
uk
Panasonic 3400mAh NCR18650B http://shop.battex.cz/pdf/NCR18650B-D.pdf appears to be protected, at least the data sheet says it has an internal PTC. Lacking in the data sheet is any mention of 'Maximum Discharge Current', the highest the charts show is 6.5A (with about a 0.5V drop!) but without a specified number this may be misleading.

DNA20 specifies unprotected 7A max discharge current or better iirc. I think I would look to a different battery, maybe something like the CGR18650CH http://www.houseofbatteries.com/documents/cgr18650ch.pdf : 10A max discharge, unprotected and even though it is only 2.25Ah capacity maybe the (I assume) lower internal resistance will make up some of the deficit.

The flat style batteries also come in various combinations of capacity+discharge current and again it is important to chose one which at least satisfies the 7Ah requirement of the DNA20. The unprotected ones used in model aeroplanes are often specified for incredibly high discharge rates, 20A or 40A is not unusual, and in order to achieve this level of delivery they have a very low internal resistance.

Internal Resistance:
Think of this as a way of measuring the amount of power which is lost due to the chemistry and internal construction of the battery. It is much like having an extra resistor in your circuit that reduces the voltage and current available, converting the losses to heat.
 

ecat

Full Member
Oct 7, 2013
42
31
uk
But it needs to be 3.7v right? And what that 25c,30c etc means?

Okay, lets use vewdew's link 5X 3 7V 1000mAh 1200mAh 25c LiPo Battery RC Walkera Wklipo 5 10 5G4Q3 Syma S006 | eBay as an example

1-cell Lithium Polymer Battery
Volt: 3.7V
Capacity: 1200mAh
Plug-type: JST
Maximum Continuous Discharge Rate:25C
Size :62mm x 31mm x 8mm
Weight : 28g
Temperatur: 0°~45°(charger); -20°~60°(discharger)
Charger Time: about 30 minutes

It is a LiPo battery so 3.7V is the nominal voltage (Max voltage is 4.2V, minimum usable voltage is around 3.3V), this is the same for all LiPo batteries.

It has a Capacity of 1200mAh, this is another way of writing 1.2Ah. The word Capacity is usually shortened to the letter C and is often used to specify the maximum charge current (eg 1C charge = 1.2A charge current) and also the discharge current which for this battery is 25C = 25 * 1.2 = 30A

It has a continuous Maximum Discharge Rate of 25C which equals 30A as shown above.
 

gavijal

Full Member
Nov 18, 2013
17
1
Zagreb, CRO, EU
Okay, lets use vewdew's link 5X 3 7V 1000mAh 1200mAh 25c LiPo Battery RC Walkera Wklipo 5 10 5G4Q3 Syma S006 | eBay as an example

1-cell Lithium Polymer Battery
Volt: 3.7V
Capacity: 1200mAh
Plug-type: JST
Maximum Continuous Discharge Rate:25C
Size :62mm x 31mm x 8mm
Weight : 28g
Temperatur: 0°~45°(charger); -20°~60°(discharger)
Charger Time: about 30 minutes

It is a LiPo battery so 3.7V is the nominal voltage (Max voltage is 4.2V, minimum usable voltage is around 3.3V), this is the same for all LiPo batteries.

It has a Capacity of 1200mAh, this is another way of writing 1.2Ah. The word Capacity is usually shortened to the letter C and is often used to specify the maximum charge current (eg 1C charge = 1.2A charge current) and also the discharge current which for this battery is 25C = 25 * 1.2 = 30A

It has a continuous Maximum Discharge Rate of 25C which equals 30A as shown above.

Ty m8-really helpful :)
 
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