First E maxx. battery question.
01-01-2016 | 01:22 PM
#1
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First E maxx. battery question.
my plan is to run 2 5s or 6s 5000 mah packs wired in parallel (so as a single battery) to the evx2 Also I will have a High amp UBEC. Dewalt 14.4 motor. And cooling fans.
Reason is of course for 10000 mah run times.
So Just asking if anyone is running this way or similar. And how are the run times? Thanks
Reason is of course for 10000 mah run times.
So Just asking if anyone is running this way or similar. And how are the run times? Thanks
01-01-2016 | 01:59 PM
#2
Joined: Apr 2009
Posts: 2,049
From: Long Island, NY
Sorry to say but you can't do what you're saying. The EVX2 esc has 2 battery inputs, each of which are meant for 2s. The esc then makes a series connection out of these 2 inputs inside the esc. One of these inputs can take 3s, the other input powers the bec and can only take 2s. So you can run 5s through the EVX2 but it has to be in the form of a 2s pack and a 3s pack, you cannot connect a 5s pack to the esc through either of the inputs.
I'd also like to offer a word of caution against running packs in parallel. The idea sounds great, double the mah for lots more runtime. But in reality you're adding a bunch of weight to the vehicle hurting performance and increasing strain on components while running and also in the event of a crash. Plus you still have to charge 10,000mah, whether it's 2 packs or one it's still going to take the same amount of time to charge 10,000mah.
My biggest opposition to parallel packs comes from having to connect them together though. Let say you put a Castle MMM (it has brushed mode) in there with a parallel harness and want to run a pair of 5s packs. When you connect the 2nd pack there is no resistance between the two packs. If the voltages are not equal one pack will be rapidly discharging while the other is rapidly charged until the voltages are equal. We know lipos don't like being charged or discharged too fast and the more of difference there is in pack voltage the more they're not going to like it. Then there's the fact that one pack is always going to be stronger than the other putting more strain on it. I've had a few packs that were made up of parallel cells (2s2p) and it never worked out well. One of the parallel cells would always drop out before the other way quicker than a comparable non 2p pack.
Just my opinion on the subject.
I'd also like to offer a word of caution against running packs in parallel. The idea sounds great, double the mah for lots more runtime. But in reality you're adding a bunch of weight to the vehicle hurting performance and increasing strain on components while running and also in the event of a crash. Plus you still have to charge 10,000mah, whether it's 2 packs or one it's still going to take the same amount of time to charge 10,000mah.
My biggest opposition to parallel packs comes from having to connect them together though. Let say you put a Castle MMM (it has brushed mode) in there with a parallel harness and want to run a pair of 5s packs. When you connect the 2nd pack there is no resistance between the two packs. If the voltages are not equal one pack will be rapidly discharging while the other is rapidly charged until the voltages are equal. We know lipos don't like being charged or discharged too fast and the more of difference there is in pack voltage the more they're not going to like it. Then there's the fact that one pack is always going to be stronger than the other putting more strain on it. I've had a few packs that were made up of parallel cells (2s2p) and it never worked out well. One of the parallel cells would always drop out before the other way quicker than a comparable non 2p pack.
Just my opinion on the subject.
01-01-2016 | 02:06 PM
#3
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From: Oconee County SC
my plan is to run 2 5s or 6s 5000 mah packs wired in parallel (so as a single battery) to the evx2 Also I will have a High amp UBEC. Dewalt 14.4 motor. And cooling fans.
Reason is of course for 10000 mah run times.
So Just asking if anyone is running this way or similar. And how are the run times? Thanks
Reason is of course for 10000 mah run times.
So Just asking if anyone is running this way or similar. And how are the run times? Thanks
01-01-2016 | 03:18 PM
#4
Joined: Apr 2009
Posts: 2,049
From: Long Island, NY
And if you want to try the 5s trick here's how you figure out which esc input powers the bec. Plug in a pair of 2s or whatever you have that totals 16.8v or less. Power on the esc and unplug one of the batteries noting how long the led on the esc stays lit. Plug it back in, power up the esc and unplug the other battery again noting how long the led stays lit. The led will go out quicker when you unplug the input that powers the bec, mark that input lead somehow (tape, zip tie or whatever) and only use 2s on that input. If you have a fan for the esc and want to try 3s on the other input do so at your own risk.
01-01-2016 | 03:29 PM
#5
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Thanks guys for the replys. I know people who run a single 4s through the evx2. You bridge the bec side battery lead. And use a UBEC.
Secondly I am a newb to the e-maxx. First one ever. But I have been around a little while in rc. The evx's internal Bec is rated at standard voltage. Like 7.4- 11.1. But by running a UBEC I bypas any voltage running to the internal BEC. Now at this point you throw away the speed controllers voltage rating. It no longer applies. This goes for any ESC. The only thing you need to be concerned about is amps, and overrunning the rpm limit of the esc.
Many have run 6s (2 batteries)through an EVX2 using both battery leads. I have read about. So this tells me the esc can run 20+ volts.
Weight, yes. A concern. The dewalt should eliminate any weight issues as far as torque. Handling yea, I will have to work with the suspension. So its something to consider for certain.
Heat? of course. More heat = more amps. PLanning on a fan for the esc and motor.
Mainly concerned with just how much run time I should expect.
Thanks again.
Secondly I am a newb to the e-maxx. First one ever. But I have been around a little while in rc. The evx's internal Bec is rated at standard voltage. Like 7.4- 11.1. But by running a UBEC I bypas any voltage running to the internal BEC. Now at this point you throw away the speed controllers voltage rating. It no longer applies. This goes for any ESC. The only thing you need to be concerned about is amps, and overrunning the rpm limit of the esc.
Many have run 6s (2 batteries)through an EVX2 using both battery leads. I have read about. So this tells me the esc can run 20+ volts.
Weight, yes. A concern. The dewalt should eliminate any weight issues as far as torque. Handling yea, I will have to work with the suspension. So its something to consider for certain.
Heat? of course. More heat = more amps. PLanning on a fan for the esc and motor.
Mainly concerned with just how much run time I should expect.
Thanks again.
01-01-2016 | 03:32 PM
#6
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Yeah 6s is going to equal bbq no matter what you try to do. But the 1st gen EVX2 without lipo cutoff has been proven to handle 5s (with a fan added to the esc) many times with the hack I mentioned in my last post. It should be noted that I haven't seen anyone run 5s on the newer EVX2 with lipo cutoff though. So I'd do some more research before trying it with the newer EVX2 that has lipo cutoff unless you're ok with possibly bbq'ing an esc and have that fire extinguisher handy.
And if you want to try the 5s trick here's how you figure out which esc input powers the bec. Plug in a pair of 2s or whatever you have that totals 16.8v or less. Power on the esc and unplug one of the batteries noting how long the led on the esc stays lit. Plug it back in, power up the esc and unplug the other battery again noting how long the led stays lit. The led will go out quicker when you unplug the input that powers the bec, mark that input lead somehow (tape, zip tie or whatever) and only use 2s on that input. If you have a fan for the esc and want to try 3s on the other input do so at your own risk.
And if you want to try the 5s trick here's how you figure out which esc input powers the bec. Plug in a pair of 2s or whatever you have that totals 16.8v or less. Power on the esc and unplug one of the batteries noting how long the led on the esc stays lit. Plug it back in, power up the esc and unplug the other battery again noting how long the led stays lit. The led will go out quicker when you unplug the input that powers the bec, mark that input lead somehow (tape, zip tie or whatever) and only use 2s on that input. If you have a fan for the esc and want to try 3s on the other input do so at your own risk.
01-01-2016 | 07:49 PM
#8
Joined: Apr 2009
Posts: 2,049
From: Long Island, NY
The evx's internal Bec is rated at standard voltage. Like 7.4- 11.1. But by running a UBEC I bypas any voltage running to the internal BEC. Now at this point you throw away the speed controllers voltage rating. It no longer applies. This goes for any ESC. The only thing you need to be concerned about is amps, and overrunning the rpm limit of the esc.
Yup, gotta be concerned about amp draw. Increasing the weight with more batteries is going to increase the amp draw. How much? Probably about the same amount as increasing the pinion size 3 teeth would. As far as the rpm limit of the esc, that's only for brushless and doesn't apply to brushed motors.
Sorry for the long post. And don't take it as picking anything apart I love discussing this stuff. Don't forget to show us what you come up with.
01-02-2016 | 05:50 PM
#9
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I've always wondered if this was possible but had never read about anyone who had done it. My experimentation with an EVX2 was brief, came with a truck and was done mostly to see what a dewalt could do.
Bypassing the bec side does eliminate that particular voltage restriction on this esc. But there are other voltage restrictions in the esc, namely the capacitors and mosfets. Sure there's usually some headroom built in but there's always a limit that you can't just throw away. Open up a MMM and you'll find 25v rated capacitors, doesn't matter what you do to the Bec the capacitors won't take more than 6s. In the EVX's case 18v capacitors would've provided some headroom for its intended 16.8v but they obviously must've used higher rated capacitors if it can survive 5s and 6s. The mosfets can usually take more voltage but the control circuits that connect to the receiver and tell the mosfets to open and close is anyone's guess.
Yup, gotta be concerned about amp draw. Increasing the weight with more batteries is going to increase the amp draw. How much? Probably about the same amount as increasing the pinion size 3 teeth would. As far as the rpm limit of the esc, that's only for brushless and doesn't apply to brushed motors.
I don't get out to many other forums these days so I haven't seen this and couldn't find any in a quick Google search. I did find a post on rcgroups a few minutes ago stating some EVX2's won't run right over 23v. Guy hooked up an adjustable power supply to test and got funky throttle response over 23v. But there's been numerous revisions to the esc and this was one guys test.
Sorry for the long post. And don't take it as picking anything apart I love discussing this stuff. Don't forget to show us what you come up with.
Bypassing the bec side does eliminate that particular voltage restriction on this esc. But there are other voltage restrictions in the esc, namely the capacitors and mosfets. Sure there's usually some headroom built in but there's always a limit that you can't just throw away. Open up a MMM and you'll find 25v rated capacitors, doesn't matter what you do to the Bec the capacitors won't take more than 6s. In the EVX's case 18v capacitors would've provided some headroom for its intended 16.8v but they obviously must've used higher rated capacitors if it can survive 5s and 6s. The mosfets can usually take more voltage but the control circuits that connect to the receiver and tell the mosfets to open and close is anyone's guess.
Yup, gotta be concerned about amp draw. Increasing the weight with more batteries is going to increase the amp draw. How much? Probably about the same amount as increasing the pinion size 3 teeth would. As far as the rpm limit of the esc, that's only for brushless and doesn't apply to brushed motors.
I don't get out to many other forums these days so I haven't seen this and couldn't find any in a quick Google search. I did find a post on rcgroups a few minutes ago stating some EVX2's won't run right over 23v. Guy hooked up an adjustable power supply to test and got funky throttle response over 23v. But there's been numerous revisions to the esc and this was one guys test.
Sorry for the long post. And don't take it as picking anything apart I love discussing this stuff. Don't forget to show us what you come up with.
"I just received today 2 ***** 5S 20C Lipos from Hobby King, 5 days from purchase to delivery in Scotland from Hong Kong is pretty impressive. As I have the setup you are thinking of running - 14V DeWalt motor and stock EVX2, I thought that in the interests of science I'd give them a run or two with the DeWalt motor before installing MMM combo which is sitting on my workbench awaiting the arrival of Spectrum 2.4GHz .
Battery connectors changed to TRX type and lipos balanced/charged. All 10 cells were 3.85 or 3.86 volts as delivered before charging, I mention that because I have heard of some Zippies being way out of balance when new, no problems with these.
First, the batteries are a tight squeeze in the compartments but after removing spring clips at the top and the 2 retainer tabs , they were in and the doors closed - just. The power cables need a bit of persuading into shape to come out of the slots, maybe need a bit of a mod to the compartment door to make this easier.
Parallel harness and jumper connected, it's time for a trial run in the garden. After a bit of a careful warm up to make sure nothing was going to smoke, everything was fine. The extra voltage sure makes a big difference to the power of the DeWalt - flipped straight on its lid from standstill on paved area with good traction, not that I condone that sort of behavior . Torque and top speed were also much improved over 4S setup.
After 15 minutes of driving I thought I'd check on temperatures and, in the absence of a 5S LVC, the battery voltage. Motor was pretty hot compared to running 4S, sorry I don't have temperature reading , no temp gun yet. ESC was a good bit hotter than on 4S as well. Lipo voltage still at 20.1V, no problems there. Ran for another 10 minutes and thought it safer for lipos to call a halt and recharge. My gearing was 20/68 as it has been for running 4S.
So far, so good. I was very impressed with the performance increase, if it could run reliably on 5S it would be an ideal waterproof alternative to going brushless. The biggest concern was how hot the DeWalt motor and EVX2 were but without a temp gun I can't be sure it was anything to be too worried about.I'll try another run once my temp gun arrives.
Also, I couldn't find a 5S LVC or even a 5S low voltage warning led, which is all I use for my 4S setup, just something else to consider if you go for this.
So, it's all down to how reliable this setup is, I might just postpone my MMM install to see how it holds up, I suspect it's on the limit of what both motor and EVX2 can handle and it will run hot or overheat."
Battery connectors changed to TRX type and lipos balanced/charged. All 10 cells were 3.85 or 3.86 volts as delivered before charging, I mention that because I have heard of some Zippies being way out of balance when new, no problems with these.
First, the batteries are a tight squeeze in the compartments but after removing spring clips at the top and the 2 retainer tabs , they were in and the doors closed - just. The power cables need a bit of persuading into shape to come out of the slots, maybe need a bit of a mod to the compartment door to make this easier.
Parallel harness and jumper connected, it's time for a trial run in the garden. After a bit of a careful warm up to make sure nothing was going to smoke, everything was fine. The extra voltage sure makes a big difference to the power of the DeWalt - flipped straight on its lid from standstill on paved area with good traction, not that I condone that sort of behavior . Torque and top speed were also much improved over 4S setup.
After 15 minutes of driving I thought I'd check on temperatures and, in the absence of a 5S LVC, the battery voltage. Motor was pretty hot compared to running 4S, sorry I don't have temperature reading , no temp gun yet. ESC was a good bit hotter than on 4S as well. Lipo voltage still at 20.1V, no problems there. Ran for another 10 minutes and thought it safer for lipos to call a halt and recharge. My gearing was 20/68 as it has been for running 4S.
So far, so good. I was very impressed with the performance increase, if it could run reliably on 5S it would be an ideal waterproof alternative to going brushless. The biggest concern was how hot the DeWalt motor and EVX2 were but without a temp gun I can't be sure it was anything to be too worried about.I'll try another run once my temp gun arrives.
Also, I couldn't find a 5S LVC or even a 5S low voltage warning led, which is all I use for my 4S setup, just something else to consider if you go for this.
So, it's all down to how reliable this setup is, I might just postpone my MMM install to see how it holds up, I suspect it's on the limit of what both motor and EVX2 can handle and it will run hot or overheat."
He was using the internal BEC I think with a external bec it would work even better. I just tried 6s (3 and 3) on the evx. It was very glitchy. So that is a no go on the internal BEC. I have a castle external bec I may hook up tonight. When I do I will post my results on 6s
01-03-2016 | 05:27 AM
#10
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From: Oconee County SC
Here's the thing the EVX2 is built to handle 16.8v usually one can safely go 10% higher with no issues. Bringing that close to 18V which we know the caps are rated for. But you're looking to go near 40% more. I still say have the fire extinguisher handy.
01-03-2016 | 01:10 PM
#11
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But as I already said i tested the evx2 with 6s and it is very twitchy. So i won't use 6s with the evx. In fact i think I will go 4s. The 5s is fine but i cant get 10000 mah with 5s without creating a tank. 10000 mah though is dooable with one 4s and roughly the same weight as a 2s x2 5000 combo.
So most likely I will end up with one 10000 4s battery with the EVX2 and a 12 volt dewalt. Still running the math.
Last edited by holycaveman; 01-03-2016 at 01:35 PM.
01-03-2016 | 03:17 PM
#12
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From: Oconee County SC
01-03-2016 | 05:45 PM
#13
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I already have. I have a ton of people running 3-6s on them in scale trucks. 5 and 6s for mud bogs. But normal trailing 3 and 4s. When you go to 6s you lose low speed crawlability.
You can run 4s on almost any esc. In fact I don't think I have ever had an esc that would not run it.
I have ran 6s on the sidewinder also
01-03-2016 | 09:32 PM
#14
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Well i ended up going with a single 8000mah 4s lipo. With some fab work i could parallel one more of the same. And i ordered a 12v dewalt motor. Yes i know about brushless. I was running them in rc trucks before most anyone. Anyways i will post up results and run times when it comes in. Thanks for all the replies.
01-05-2016 | 12:21 PM
#15
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Sounds like an awesome idea but like mentioned above your vehicle won't last very long.
I have a quick question because in my e Maxx the 3s plastic strap down things I set to the higher side which is 28mm I believe but I have to use that to run 2x 2s 5200mah batteries how are you guys even running two 3s without using like 2800mah's.. Custom Velcro wrap around a of some sort? Because for the heck of it I tried Velcro on the bottom of my 2s batteries and the other side of Velcro on the battery tray and that wouldn't even hold in for more than a 2 min casual flat street infront of my house ride.
Any suggestions?
I have a quick question because in my e Maxx the 3s plastic strap down things I set to the higher side which is 28mm I believe but I have to use that to run 2x 2s 5200mah batteries how are you guys even running two 3s without using like 2800mah's.. Custom Velcro wrap around a of some sort? Because for the heck of it I tried Velcro on the bottom of my 2s batteries and the other side of Velcro on the battery tray and that wouldn't even hold in for more than a 2 min casual flat street infront of my house ride.
Any suggestions?