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Is it worth it to get dedicated Lipo Discharger? 2s discharge amps?

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Is it worth it to get dedicated Lipo Discharger? 2s discharge amps?

Old 07-04-2022, 08:27 AM
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Default Is it worth it to get dedicated Lipo Discharger? 2s discharge amps?

So I've got a SkyRc D260w charger which has 10Wx2 discharging feature, at 2 amps max. Based on a video I saw on youtube by Amain they have a formula for 2s batteries which is WATTS/8.4 volts. So 10w/8.4v = 1.19 amps would be the max discharge my current charger can do with the battery at full charge hence the charged voltage of 4.2v x 2 cells. = 8.4V.

I was looking into the SkyRC BD250 which is capable for 250W discharge rather than 10W with my current charger. So 250w/8.4v=29.76 amps max discharge for my 2s batteries.

Is it safe to discharge my 4000mah 120c 2s battery at almost 30 amps vs my current charger 1.19 amps? If not what is the ideal max amps to discharge my batteries. Should I get a dedicated discharger or stick with my current charger 10w capabilities.

Another question is, is there a way to either make a harness is series or parallel in order for me to discharge multiple packs at the same time if using a higher capacity discharger like the BD250? The BD250 can only discharge 1 pack the way it is setup, vs my current charger which can do 2 packs, but at only 1.19 amps.

Thanks for the feedback.
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Old 07-04-2022, 09:43 AM
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yes its safe to discharge said battery at 30 amp.cant you turn that looked at discharger down to desired amperage?. I use old school dischargers from 1/2 amp to 35 amps along with a few brake light bulb dischargers I have made,,.you can make a Y harness to connect 2 of the same size batteries to the said discharger as in 4000 mah. they need to be at almost same voltage to be safe.
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Old 07-04-2022, 09:53 AM
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I actually got one of those old DEANS light bars with cutoff box, but I used it on my Nicads before, I didn't know if it would be okay to use on my Lipos, and I forget how many amps it draws and what voltage the box cut offs at.
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Old 07-04-2022, 02:36 PM
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You can safely draw a lot more amps with LiPo than you could with NiCd.

What are you trying to achieve? If you're trying to save time when discharging to storage voltage at the end of the day, it could be useful, but you'll be close to storage after a run anyway. The main benefit would be faster discharges from full charge. If you plan to do that, it'll make a big difference. However if the reason you want to do that is to cycle the packs to lower the IR, then it's really inconvenient to have to keep swapping the pack between the charger and discharger. And depending on where you race, external dischargers may not be legal.
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Old 07-04-2022, 03:29 PM
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I use a Skyrc BD250 and discharge my lipos at 10A. I take them down to 7.4V at 10A. This just makes discharging a whole lot faster than my normal charger. However it does not have a balance feature so may dis charge one cell more that the other. For this reason I would not put two batteries in series to discharge at once as you could finish up over discharging one of the packs. Once I have discharged my lipos at 10 amps on the Skyrc discharger I then put them on my normal charger to get to final discharge state.
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Old 07-04-2022, 05:33 PM
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put a vom meter to light box with a battery buzzer on lipo
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Old 07-04-2022, 05:42 PM
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Originally Posted by silence360
So I've got a SkyRc D260w charger which has 10Wx2 discharging feature, at 2 amps max. Based on a video I saw on youtube by Amain they have a formula for 2s batteries which is WATTS/8.4 volts. So 10w/8.4v = 1.19 amps would be the max discharge my current charger can do with the battery at full charge hence the charged voltage of 4.2v x 2 cells. = 8.4V.

I was looking into the SkyRC BD250 which is capable for 250W discharge rather than 10W with my current charger. So 250w/8.4v=29.76 amps max discharge for my 2s batteries.

Is it safe to discharge my 4000mah 120c 2s battery at almost 30 amps vs my current charger 1.19 amps? If not what is the ideal max amps to discharge my batteries. Should I get a dedicated discharger or stick with my current charger 10w capabilities.

Another question is, is there a way to either make a harness is series or parallel in order for me to discharge multiple packs at the same time if using a higher capacity discharger like the BD250? The BD250 can only discharge 1 pack the way it is setup, vs my current charger which can do 2 packs, but at only 1.19 amps.

Thanks for the feedback.
I've seen this "high discharge rate" for the one cell racers but don't see a reason for 2 cell.
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Old 07-04-2022, 06:22 PM
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Thanks for everyones feedback. I need to bring down fully charged lipos as there are some weekends races get cancelled, or I simply change my mind going racing. So I've decided to keep cost down and use my old Deans Light Bar, and wire a 10 USD discharge cut off box controller. Which is good for 6v-80v. So it should work. I can set the lower voltage limit where the relay will trigger the relay to turn off load, and set a high voltage limit where the relay is activated again. I can then do a balance charge as someone suggested once I've drawn the packs down a little under storage voltage.



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Old 07-09-2022, 09:02 AM
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Originally Posted by silence360
I actually got one of those old DEANS light bars with cutoff box, but I used it on my Nicads before, I didn't know if it would be okay to use on my Lipos, and I forget how many amps it draws and what voltage the box cut offs at.
I still use one of those (not the actual Deans) bulb dischargers. Works great... just gotta be around to monitor voltages, or have some way/something to let you know the voltage is getting low... so you can stop the discharge of a LiPo from going too far. With ten bulbs (1157?) I can discharge at 20-ish amps.

People will use resistors nowadays for a "modern day" look? Resistors, or light bulbs just do the same thing... converting that battery energy into heat.

If you got a charger with an external discharge feature, then you could setup the parameters where you want the amperage to be (15A max on charger shown), and where to end the discharge voltage. I normally will have the cutoff voltage at 3.75v/cell and the voltages will "bounce back up" close to 3.8v/cell after undoing the load.




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Old 07-09-2022, 12:21 PM
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Originally Posted by silence360
So I've got a SkyRc D260w charger which has 10Wx2 discharging feature, at 2 amps max. Based on a video I saw on youtube by Amain they have a formula for 2s batteries which is WATTS/8.4 volts. So 10w/8.4v = 1.19 amps would be the max discharge my current charger can do with the battery at full charge hence the charged voltage of 4.2v x 2 cells. = 8.4V.

I was looking into the SkyRC BD250 which is capable for 250W discharge rather than 10W with my current charger. So 250w/8.4v=29.76 amps max discharge for my 2s batteries.

Is it safe to discharge my 4000mah 120c 2s battery at almost 30 amps vs my current charger 1.19 amps? If not what is the ideal max amps to discharge my batteries. Should I get a dedicated discharger or stick with my current charger 10w capabilities.

Another question is, is there a way to either make a harness is series or parallel in order for me to discharge multiple packs at the same time if using a higher capacity discharger like the BD250? The BD250 can only discharge 1 pack the way it is setup, vs my current charger which can do 2 packs, but at only 1.19 amps.

Thanks for the feedback.
How far ahead of race day are you charging your batteries? Leaving a Lipo fully charged for more than 24 hrs. is not a good idea. I can see charging them in the morning before you leave or the night before if you're on the road early.
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Old 07-10-2022, 04:46 PM
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Originally Posted by Andy Koback
How far ahead of race day are you charging your batteries? Leaving a Lipo fully charged for more than 24 hrs. is not a good idea. I can see charging them in the morning before you leave or the night before if you're on the road early.
I never charge my batteries before race day. I charge them at the track. Travelling with a fully charged lipo in the trunk on a hot day can kill them quickly.
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Old 07-11-2022, 10:26 AM
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Sometimes (although rarely), I do charge batteries at home. But a) only right before I leave (not the day before!) and b) the track is only a few minutes (5 or so) away, so they don't have a chance to heat up in my trunk. But most of the time, I charge at the track. It doesn't take long, even with our limit of 12A max. and I set up charger and battery first, so it charges while I unload the rest of my stuff and set up my pit table.
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Old 07-11-2022, 11:44 AM
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I made my own 500w (max) discharger Building a discharger - R/C Tech Forums (rctech.net)
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Old 07-11-2022, 08:44 PM
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Is anything plugged into the balance board in those pics?
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Old 07-18-2022, 12:30 AM
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Got it all together and worked perfectly. So glad I was able to use what I had and make it work. Could have gone the resistor route but wanted to use the bulbs since I had them already. Storage discharged my 3s in no time. A bit nostalgic since I have had this deans discharge bulbs probably since 1995 or so.
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