Hi Nick, pretty cool video, as always! :) I've some questions. My plan is to build an resistor for my Junsi 406 . Idea is to discharge with up to 40 amps 4s Lipo. Following your answers in this thread I calculated this. 4S = 15V, means 15/40=0.375 Ohm 40A means 40x15=600 Watts Assuming this calculation I would buy 8x 3R(3Ohm) 100W (3/8=0.375) resistors and connect them parallel. Right? Why 8 (means 800W)? To have some reserves and not so high temp. Makes sense? During winter saison my plan is to use the same resistor for 1s Lipos, restricted and controlled via Junsi charger, will this work? Thank you very much in advance Nick :)
Hi Thomas. Your calculations are correct. The resistors will get very hot, so add plenty of fan cooling. The 406 adjusts the voltage to the discharger to obtain the Watts dissipation. with a 1S lipo it will have to convert the voltage to obtain 160watts dissipation. Which in this case is about 3.75V for 40 amps.
Hi Milton If you want 40 amps discharge, then using the equation Resistance=Volts/Amps R= 4/40 =0.1ohm The watts is VoltsxAmps. so 4x40= 160Watts. So using 5 of your 0.5ohm resistors all in parallel you can get 0.5/5 = 0.1ohm You could use 50 watts each, but 100watt is better. Nick
Hi patrick I bought them from China/Hongkong. There are 100watt and 50watt that are all good: www.ebay.co.uk/itm/2-x-100W-Watt-0-68-Ohm-5-Wirewound-Green-Aluminum-Housed-Resistors-/191685310597?hash=item2ca155b885:g:RcAAAOSwOyJX7uQ1
Hi nick, great video. just a quick question. with a fully charged battery and using the resistors to discharge the pack how warm do they get during the cycle? also would you need a bigger fan then you are currently using? great videos. keep them coming.
Hi Mike The Lipo reach about 40degree C. after discharge. Depending on how you charge, they will cool down at anything below 10 amps charge. The fan is not necessary if you have a big enough box or metal heatsink. I was going to fit a small voltage booster to the fan, which you can buy cheap on Ebay. That will get the fan moving fast, especially if in a closed box.
greetings, very interesting design .... I have a question I have a discharger for nickel in series of 30 to 350voltios DC .... I currently use bulbs 500watts to download them, that resistance can be used to replace these bulbs. .. I thank you in advance for your help.
Hi The 500watt bulbs will have a variable resistance with voltage. They are 110V bulbs? The resistance increases with voltage, but at 110v they draw 4.5Amps. I am not sure what they draw at 30 volts. Lets say 10 amps. Resistance=Volts/Amps Watts= VoltsxAmps. So: You have 30 volts and 10 amps (500watt bulb) Amps= 10 So you need: 10/17 = 0.59 ohms. The power dissipation will be 10 x 30 =300watts. You will need: 4 x 2 ohm 100watt resistors in parrallel to give 0.5 ohms and manage 400watt heat dissipation. You can use other resistors such as 5 x 0.1ohm (100watts each) in series. Hope that helps. Nick
Hi Stable as possible? You need to stop the discharge at the minimum voltage. If you have a 30 volt Nicad pack, then there will be 20 cells in the pack. You will have to be careful that no cell goes below 0 Volt, as any reverse current flow will ruin the cell. Can you send me a photo of your battery?
Hi, I want to make a lipo discharge unit but I have an idea about the calculation of the resistance. 4S 5200mAh lipo battery pulling 10 amps to 50% storage level you want to download. What resistance should I use for this?
Hi hans 4S Lipo say 15V under load. For 10 Amps current R=V/I = 15/10 = 1.5 ohm Resistor dissipation = VxA = 15 x 10 = 150Watts. So you will need at least 3 x 100Watt resistors, so that they do not burn out. 3 x 0.5ohm (100watt) resistors in series shoould do it. They are available cheaply from Hong Kong. www.ebay.co.uk/itm/Green-0-5-Ohm-5-100-Watt-Aluminum-Shell-Wire-Wound-Resistor-2pcs/382420365314?epid=1938119842&hash=item590a07b002:g:iSkAAOSwmaVbmB8w:rk:1:pf:0
Thank you very much for your helpful answer. I'm working on a discharge project controlled by arduino and delays. Do you have any idea about the life of these high wattage resistors? I see the use of mosfets as an alternative to resistance. What do you think is the correct road map for stable discharge of 4s batteries?
The 100W resistors have a long life between failures, as long as they are run at less than rated wattage, and well heatsinked. Run at 50 -60 Watts each resistor. Of course a sophisticated controlled FET discharge has the ability to sustain a constant current, and can be switched off at a selected votage. I do sell dischargers with auto switch off, but use resistor load for simplicity and reliability. FETs can blow out if they are subjected to unexpected overload. But in your case, it is a project, so sophistication, cost and reliability are probably not a factor. Hope it goes well.
@@nickadams5411 Hi, the resistors finally came from China.(100w 0.5 Ohm) Now is the test time. Please tell me if I am wrong: I will connect three 0.5 ohm resistors in series. My total resistance is 1.5 ohms. According to your calculation, 10 Amperes will flow from 4S batteries. Is such a design a threat to the internal resistance of the lipo battery? (Sorry for my amateur questions)
@@solosolo6398 Hi, yes that is correct. there is no threat to lipo. But make sure discharge is stopped before any cell falls below 3.0volts (12.0volts for the 4S pack). At 10 amps the lipo discharge temperature. should only be a few degrees above ambient. Note that the lipo 5200mah (5.2Amps per hour), at 10 amp discharge, will take 30minutes to discharge from a full charge.
Hey Nick! Thank you for your vids...very helpful for me! Question: What size & how many resistors would I need to discharge a 6000mah 100C 2S Lipo @ a rate of 30 amps? Thank you in advance!
Hi A 2s lipo will be about 8V at 30 amps, ehich is 8x30=240watts dissipation. So you will need 4 x 100watt resistors to be on safe side. The resistance is V/I, 8/30=0.27ohm. So, you can use 4 x 1 ohm (100watt) resistors in parrallel = 1/4= 0.25 ohm. Near enough.!
Nick Adams Nick Adams Thank you Sir!!! I just found a few 6 ohm load resistors left over from converting to all LED’s on my automobiles. Can I use a couple of those instead of the (4) 1 ohms? Thank you again!!!!
To get down to about 1/4 ohm (0.25) you will need 6/0.25=24. That is 24 x 6 ohm resistors in parallel. Total wattage, say 300. so each one would need to be at least 12.5watt rating.
Nick Adams Oh, ok. I thought you would need less resistors if they were higher in ohms rating. Shows you what I know! HaHa. Thanks again Nick! I appreciate your time!
I use an i charger and i charge at 30 amps and discharge at 35. I have a discharge bank that has 5 resistors that I purchased. how can I tell the value of the resistor? all the information is hidden and it has 4 mini fans with 2 thermo apoxied on top and 2 on bottom. my resistors reach about 130 degrees Fahrenheit. that's why I was wondering if you needed a bigger fan but you do have it attached to the metal case with thermo transfer compound.
Hi Mike Measuring the low resisatnce is difficult without an ammeter, or other measuring device. Most cheap multimeters don't go above 10 amps. The clamp meters (DC) used to be very expensive. But there are cheap Chinese ones if you look. (As long as they measure DC and go up to say 40 amps) Your charger should display the total amps being discharged from the inernal and external together? You still use fahrenheit! 130 degree is not that hot. 65degree C (150 F) is the max temperature that anyone should be able to touch. So unless the case is getting that hot, the fans should be fine. The thermal transfer compound is to transfer the resistor dissipation heat to the larger surface area of the case, which can radiate the heat away.
Hi Nick, I like your videos a lot! They are so detailed which I like the most. Can you please post which resistors you're are using? I didn't find the right one on eBay. This would help me a lot. I'll start to race with the GT12 class this winter, and we'll using 1S LiPo.
Hi Stefan You can use 6 of these: www.ebay.co.uk/itm/2pcs-50-Watt-Power-0-68-Ohm-5-Aluminum-Casing-Wire-Wound-Resistor-Green-/191678601255?hash=item2ca0ef5827:g:gyoAAOSw3ydV5EXz or these: www.ebay.co.uk/itm/2-x-100W-Watt-0-68-Ohm-5-Wirewound-Green-Aluminum-Housed-Resistors-/191685310597?hash=item2ca155b885:g:e9EAAOSwHjNV7n2d
Wait, so the purpose of this is confusing (i'm dumb that way). Does this serve 2 purposes. A discharger for taking 1S lipos down to 3.85v (storage charge) from 4.x voltage? and also by seeing how fast a 1S will discharge for purposes of driving R/C cars. I am simply trying to take those really small 1S batteries down from a fully charged state of 4.2volts down to a place where i can store them until i need them. I can't find anything to take this voltage down on these little 1S LIPOs,i connect LED lights to them and it would take forever. My LIPO is the following: 3.7V 300mAh 25C LiPo Battery. These are used for quad copters and they have the little tine white two conductor molex or not sure what the end type is. but they are little two prong white connectors. Here is the amazon part link so you get an idea of what i'm dealing with. Just would love a way to discharge these little buggers before they start puffing up due to being kept at 4.1x or 4.xx volts and not being able to discharge them. Any help is appreciated. If you know of a product great, if not, i have those exact bronze looking resisters for car turn-signals anti-fast-flash syndrome...sorry, that's the only way i know how to describe those things. I have a handful of them , perhaps 5 or 6 that are all 50W 6Ohm J model
Hi Harpo. Your lipo are small capacity, and will not need much to discharge them quickly. I suggest 4 amps would be enough. So lets say the lipo is at 4 volts and you want a 4amp discharge. The formula to find the resistance is R=V/I which is 4/4=1ohm. The power dissipated is W=VxI which is 4x4=16watts. So a single 1ohm resistor rated at least 25watts (50watts is better) will be all you need. (They are cheap on Ebay) The time to discharge the fully charge lipo of 300mah will be 300/4000 x60minutes=4.5minutes. So to half discharge to 150ma will only take 2.25 minutes. Hope that helps. Nick
@@nickadams5411 Hey, im not that good at english.. so i ask to make sure: I have a bunch of 1S LiHv`s.. between 250 and 450 mAh.. I want to test the cells.. that way i want to build one myself..( discharger ) 4V / around 10 Ampere = 0,4 Ω Ohm which is 0,0004 Kilo Ohm right ?!
Fantastic information. Thanks for taking the time to share it with us!
Hi Nick, pretty cool video, as always! :)
I've some questions.
My plan is to build an resistor for my Junsi 406 .
Idea is to discharge with up to 40 amps 4s Lipo.
Following your answers in this thread I calculated this.
4S = 15V, means 15/40=0.375 Ohm
40A means 40x15=600 Watts
Assuming this calculation I would buy 8x 3R(3Ohm) 100W (3/8=0.375) resistors and connect them parallel. Right?
Why 8 (means 800W)? To have some reserves and not so high temp. Makes sense?
During winter saison my plan is to use the same resistor for 1s Lipos, restricted and controlled via Junsi charger, will this work?
Thank you very much in advance Nick :)
Hi Thomas. Your calculations are correct. The resistors will get very hot, so add plenty of fan cooling.
The 406 adjusts the voltage to the discharger to obtain the Watts dissipation. with a 1S lipo it will have to convert the voltage to obtain 160watts dissipation. Which in this case is about 3.75V for 40 amps.
@@nickadams5411 Thank you very much Nick!
for and cell of nissan leaf gen 1 with 500w 60ah 2s 8.2v max 3.1 min what resistor you advice to go ?
Good morning Nick.I couldn't find the 0.68 ohm resistors, so I got the 0.50 resistors. how many will I need to make the discharger?Thanks.
Hi Milton
If you want 40 amps discharge, then using the equation Resistance=Volts/Amps
R= 4/40 =0.1ohm
The watts is VoltsxAmps. so 4x40= 160Watts.
So using 5 of your 0.5ohm resistors all in parallel you can get 0.5/5 = 0.1ohm
You could use 50 watts each, but 100watt is better.
Nick
Hi Nick. Thank you very much for the quick reply. I did get the 100watt resistors. Have a great day.Milton
Hi Nick,
can you point me towards the 100 watt 0.68 ohm's resistors that you are using for this build ?
Hi patrick
I bought them from China/Hongkong.
There are 100watt and 50watt that are all good:
www.ebay.co.uk/itm/2-x-100W-Watt-0-68-Ohm-5-Wirewound-Green-Aluminum-Housed-Resistors-/191685310597?hash=item2ca155b885:g:RcAAAOSwOyJX7uQ1
Hi nick, great video. just a quick question. with a fully charged battery and using the resistors to discharge the pack how warm do they get during the cycle? also would you need a bigger fan then you are currently using? great videos. keep them coming.
Hi Mike
The Lipo reach about 40degree C. after discharge.
Depending on how you charge, they will cool down at anything below 10 amps charge.
The fan is not necessary if you have a big enough box or metal heatsink.
I was going to fit a small voltage booster to the fan, which you can buy cheap on Ebay. That will get the fan moving fast, especially if in a closed box.
greetings, very interesting design .... I have a question I have a discharger for nickel in series of 30 to 350voltios DC .... I currently use bulbs 500watts to download them, that resistance can be used to replace these bulbs. .. I thank you in advance for your help.
Hi
The 500watt bulbs will have a variable resistance with voltage.
They are 110V bulbs?
The resistance increases with voltage, but at 110v they draw 4.5Amps.
I am not sure what they draw at 30 volts.
Lets say 10 amps.
Resistance=Volts/Amps
Watts= VoltsxAmps.
So:
You have 30 volts and 10 amps (500watt bulb)
Amps= 10
So you need:
10/17 = 0.59 ohms.
The power dissipation will be 10 x 30 =300watts.
You will need:
4 x 2 ohm 100watt resistors in parrallel to give 0.5 ohms and manage 400watt heat dissipation.
You can use other resistors such as 5 x 0.1ohm (100watts each) in series.
Hope that helps.
Nick
I just need something that allows me to download them with a current as stable as possible ...
Hi
Stable as possible?
You need to stop the discharge at the minimum voltage.
If you have a 30 volt Nicad pack, then there will be 20 cells in the pack.
You will have to be careful that no cell goes below 0 Volt, as any reverse current flow will ruin the cell.
Can you send me a photo of your battery?
hey Nick when i wire up the resistors, does the resistor have a positive and negative side?
Hi Sam
No, resistors are the same either way.
Awesome, thank you. Your videos are great and very helpful....
Hi,
I want to make a lipo discharge unit but I have an idea about the calculation of the resistance. 4S 5200mAh lipo battery pulling 10 amps to 50% storage level you want to download. What resistance should I use for this?
Hi hans
4S Lipo say 15V under load.
For 10 Amps current
R=V/I = 15/10 = 1.5 ohm
Resistor dissipation = VxA = 15 x 10 = 150Watts.
So you will need at least 3 x 100Watt resistors, so that they do not burn out.
3 x 0.5ohm (100watt) resistors in series shoould do it.
They are available cheaply from Hong Kong.
www.ebay.co.uk/itm/Green-0-5-Ohm-5-100-Watt-Aluminum-Shell-Wire-Wound-Resistor-2pcs/382420365314?epid=1938119842&hash=item590a07b002:g:iSkAAOSwmaVbmB8w:rk:1:pf:0
Thank you very much for your helpful answer. I'm working on a discharge project controlled by arduino and delays.
Do you have any idea about the life of these high wattage resistors? I see the use of mosfets as an alternative to resistance. What do you think is the correct road map for stable discharge of 4s batteries?
The 100W resistors have a long life between failures, as long as they are run at less than rated wattage, and well heatsinked. Run at 50 -60 Watts each resistor.
Of course a sophisticated controlled FET discharge has the ability to sustain a constant current, and can be switched off at a selected votage.
I do sell dischargers with auto switch off, but use resistor load for simplicity and reliability. FETs can blow out if they are subjected to unexpected overload.
But in your case, it is a project, so sophistication, cost and reliability are probably not a factor.
Hope it goes well.
@@nickadams5411
Hi,
the resistors finally came from China.(100w 0.5 Ohm) Now is the test time.
Please tell me if I am wrong:
I will connect three 0.5 ohm resistors in series. My total resistance is 1.5 ohms.
According to your calculation, 10 Amperes will flow from 4S batteries.
Is such a design a threat to the internal resistance of the lipo battery?
(Sorry for my amateur questions)
@@solosolo6398 Hi, yes that is correct. there is no threat to lipo. But make sure discharge is stopped before any cell falls below 3.0volts (12.0volts for the 4S pack). At 10 amps the lipo discharge temperature. should only be a few degrees above ambient. Note that the lipo 5200mah (5.2Amps per hour), at 10 amp discharge, will take 30minutes to discharge from a full charge.
Hey Nick! Thank you for your vids...very helpful for me! Question: What size & how many resistors would I need to discharge a 6000mah 100C 2S Lipo @ a rate of 30 amps? Thank you in advance!
Hi
A 2s lipo will be about 8V at 30 amps, ehich is 8x30=240watts dissipation.
So you will need 4 x 100watt resistors to be on safe side.
The resistance is V/I, 8/30=0.27ohm.
So, you can use 4 x 1 ohm (100watt) resistors in parrallel = 1/4= 0.25 ohm. Near enough.!
Nick Adams Nick Adams Thank you Sir!!! I just found a few 6 ohm load resistors left over from converting to all LED’s on my automobiles. Can I use a couple of those instead of the (4) 1 ohms? Thank you again!!!!
To get down to about 1/4 ohm (0.25) you will need 6/0.25=24. That is 24 x 6 ohm resistors in parallel.
Total wattage, say 300. so each one would need to be at least 12.5watt rating.
Nick Adams Oh, ok. I thought you would need less resistors if they were higher in ohms rating. Shows you what I know! HaHa. Thanks again Nick! I appreciate your time!
I use an i charger and i charge at 30 amps and discharge at 35. I have a discharge bank that has 5 resistors that I purchased. how can I tell the value of the resistor? all the information is hidden and it has 4 mini fans with 2 thermo apoxied on top and 2 on bottom. my resistors reach about 130 degrees Fahrenheit. that's why I was wondering if you needed a bigger fan but you do have it attached to the metal case with thermo transfer compound.
Hi Mike
Measuring the low resisatnce is difficult without an ammeter, or other measuring device.
Most cheap multimeters don't go above 10 amps.
The clamp meters (DC) used to be very expensive. But there are cheap Chinese ones if you look. (As long as they measure DC and go up to say 40 amps)
Your charger should display the total amps being discharged from the inernal and external together?
You still use fahrenheit!
130 degree is not that hot.
65degree C (150 F) is the max temperature that anyone should be able to touch.
So unless the case is getting that hot, the fans should be fine.
The thermal transfer compound is to transfer the resistor dissipation heat to the larger surface area of the case, which can radiate the heat away.
Hi Nick, I like your videos a lot! They are so detailed which I like the most. Can you please post which resistors you're are using? I didn't find the right one on eBay. This would help me a lot. I'll start to race with the GT12 class this winter, and we'll using 1S LiPo.
Hi Stefan
You can use 6 of these:
www.ebay.co.uk/itm/2pcs-50-Watt-Power-0-68-Ohm-5-Aluminum-Casing-Wire-Wound-Resistor-Green-/191678601255?hash=item2ca0ef5827:g:gyoAAOSw3ydV5EXz
or these:
www.ebay.co.uk/itm/2-x-100W-Watt-0-68-Ohm-5-Wirewound-Green-Aluminum-Housed-Resistors-/191685310597?hash=item2ca155b885:g:e9EAAOSwHjNV7n2d
Great thanks a lot. I'll try it.
Wait, so the purpose of this is confusing (i'm dumb that way). Does this serve 2 purposes. A discharger for taking 1S lipos down to 3.85v (storage charge) from 4.x voltage? and also by seeing how fast a 1S will discharge for purposes of driving R/C cars. I am simply trying to take those really small 1S batteries down from a fully charged state of 4.2volts down to a place where i can store them until i need them. I can't find anything to take this voltage down on these little 1S LIPOs,i connect LED lights to them and it would take forever. My LIPO is the following: 3.7V 300mAh 25C LiPo Battery. These are used for quad copters and they have the little tine white two conductor molex or not sure what the end type is. but they are little two prong white connectors. Here is the amazon part link so you get an idea of what i'm dealing with. Just would love a way to discharge these little buggers before they start puffing up due to being kept at 4.1x or 4.xx volts and not being able to discharge them. Any help is appreciated. If you know of a product great, if not, i have those exact bronze looking resisters for car turn-signals anti-fast-flash syndrome...sorry, that's the only way i know how to describe those things. I have a handful of them , perhaps 5 or 6 that are all 50W 6Ohm J model
Hi Harpo. Your lipo are small capacity, and will not need much to discharge them quickly. I suggest 4 amps would be enough.
So lets say the lipo is at 4 volts and you want a 4amp discharge. The formula to find the resistance is R=V/I which is 4/4=1ohm. The power dissipated is W=VxI which is 4x4=16watts.
So a single 1ohm resistor rated at least 25watts (50watts is better) will be all you need. (They are cheap on Ebay)
The time to discharge the fully charge lipo of 300mah will be 300/4000 x60minutes=4.5minutes.
So to half discharge to 150ma will only take 2.25 minutes.
Hope that helps. Nick
@@nickadams5411 Hey, im not that good at english..
so i ask to make sure: I have a bunch of 1S LiHv`s..
between 250 and 450 mAh..
I want to test the cells.. that way i want to build one myself..( discharger )
4V / around 10 Ampere = 0,4 Ω Ohm
which is 0,0004 Kilo Ohm right ?!
@@Cre8ionz. Yes. You can buy low ohm resistors on ebay. Get the 100 watt ones.
@@nickadams5411 thx !
Sound like old man in Family Guy with the whistle when he talks haha