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Thread: 5s Works

  1. #1
    RC Turnbuckle Jr. Wolfslash16's Avatar
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    5s Works

    Hey guys, I've seen people asking if 5s works on the X-Maxx in different threads, so I tried it. Yes, it runs and drives when I plugged in a 2s and a 3s battery.

    EDIT: I only tried it to see if it was possible. I do not at all recommend doing it though. I do not like the idea of two different batteries being run together if they're not the exact same cell count, mah, and C rating. The low voltage is a great question, it would probably drain the 2s too far. I know you can, but I don't recommend it.
    Last edited by Wolfslash16; 12-22-2015 at 03:21 PM.
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    RC Qualifier Fuglio's Avatar
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    Its bad practice to mix batteries in series.

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    Quote Originally Posted by Wolfslash16 View Post
    Hey guys, I've seen people asking if 5s works on the X-Maxx in different threads, so I tried it. Yes, it runs and drives when I plugged in a 2s and a 3s battery.
    I think the real question is whether it will detect low voltage properly.

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    Quote Originally Posted by Fuglio View Post
    Its bad practice to mix batteries in series.

    No it's not. It's very common to put a 3s and 2s in series to get 5s. You just want to use packs with the same mAh and C rating.
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    RC Turnbuckle Jr. Wolfslash16's Avatar
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    Edited above post.
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    Quote Originally Posted by Fuglio View Post
    Its bad practice to mix batteries in series.
    This isn't true, what do you think a 2S pack is? It is 2 cells in series. A 3S pack? Bam, 3 cells in series. What do you think the X-Maxx runs on? 6S, a pair of 3S packs in series which are internally 3 cells in series!

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    Quote Originally Posted by Wolfslash16 View Post
    Hey guys, I've seen people asking if 5s works on the X-Maxx in different threads, so I tried it. Yes, it runs and drives when I plugged in a 2s and a 3s battery.

    EDIT: I only tried it to see if it was possible. I do not at all recommend doing it though. I do not like the idea of two different batteries being run together if they're not the exact same cell count, mah, and C rating. The low voltage is a great question, it would probably drain the 2s too far. I know you can, but I don't recommend it.
    Glad to see 5S doesn't cause any problems, but since 4S and 6S work... it isn't a huge surprise. The only concern I can see is the low voltage cut off. Any chance you'll run your truck on 5S until it gets low?

    And as long as the packs are similar capacity and both meet the minimum discharge rating, you're fine. Just follow all the same precautions you would for a pair of 2S or a pair of 3S. They should be charged to similar levels. Your 3S battery is actually 3x 1S batteries, so you're *already* doing this when you use any battery that isn't a 1S.
    Last edited by fryfrog; 12-22-2015 at 03:33 PM.

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    RC Turnbuckle Jr. Wolfslash16's Avatar
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    Glad to see 5S doesn't cause any problems, but since 4S and 6S work... it isn't a huge surprise. The only concern I can see is the low voltage cut off. Any chance you'll run your truck on 5S until it gets low?
    Ha ha ha no thanks I'm good, I'll let some one else try that, I don't want to ruin one of my batteries.
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  9. #9
    RC Qualifier Fuglio's Avatar
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    Quote Originally Posted by fryfrog View Post
    This isn't true, what do you think a 2S pack is? It is 2 cells in series. A 3S pack? Bam, 3 cells in series. What do you think the X-Maxx runs on? 6S, a pair of 3S packs in series which are internally 3 cells in series!
    Its bad practice. Even with 2 identical batteries you want to keep them together always use them in the same car and charge them at the same time. 2 batteries of different sizes will discharge unevenly, never mix batteries even identically speced batteries from different brands should not be mixed. Its bad practice.

    Are these batteries of the same capacity, discharge rate?

    Will low voltage cut off work when the 2s battery is depleted?

    Its fun to try things to see if they work, but just because it works doesnt make it a good idea.



    Quote Originally Posted by fryfrog View Post
    Glad to see 5S doesn't cause any problems, but since 4S and 6S work... it isn't a huge surprise. The only concern I can see is the low voltage cut off. Any chance you'll run your truck on 5S until it gets low?

    And as long as the packs are similar capacity and both meet the minimum discharge rating, you're fine. Just follow all the same precautions you would for a pair of 2S or a pair of 3S. They should be charged to similar levels. Your 3S battery is actually 3x 1S batteries, so you're *already* doing this when you use any battery that isn't a 1S.
    A 3s battery could be 6 cells ran in a combination of series and parallel to get the desired Amp Hrs. You wouldn't run a 3s 8000 and 3s 5000 together either.... it may not be a big deal but when it comes to an online fourum that people come to for advice we gotta give good advice.

    I see somone that wants to mix batteries as a person that wants to save money. It would be a shame for somone in that financial situation to end up with 2 non working batteries and some puffed cells from over discharging.

    Theres tons of things you can do with lipo batteries (or any batteries) that you shouldn't
    Last edited by Fuglio; 12-22-2015 at 03:51 PM.

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    Now try 8 s with an xl2 lol

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    Quote Originally Posted by Fuglio View Post
    Its bad practice. Even with 2 identical batteries you want to keep them together always use them in the same car and charge them at the same time. 2 batteries of different sizes will discharge unevenly, never mix batteries even identically speced batteries from different brands should not be mixed. Its bad practice.

    Are these batteries of the same capacity, discharge rate?

    Will low voltage cut off work when the 2s battery is depleted?

    Its fun to try things to see if they work, but just because it works doesnt make it a good idea.
    I think you're mixing a few things up.

    There is nothing wrong with using a pair of 2S batteries to make 4S. There is nothing wrong with using a pair of 3S batteries to make 6S. This is exactly what the X-Maxx and plenty of other vehicles do. There is *also* nothing wrong with doing the same thing with a 2S and a 3S to make 5S.

    But you're right about some things. The batteries should be very similar (nothing in real life is identical, even the cells inside your 2S or 3S pack). Each individual cell should be very close to the same capacity (both in a single pack and between both packs). As an example, a 2S 5,000 mah and a 3S 5,000 mah. They should start in similar charge states. They should have similar discharge capacity. You're right that you shouldn't just rely on the specs of the battery, but even in the same brand or "identical" pack, these could be different so it might be worth a charge/discharge cycle to confirm *any* pair of batteries you'd use. But this is true of using *any* collection of batteries in series!

    For the low voltage cut off, it has nothing to do with the mixing of packs. It isn't that it detects the 2S being depleted, it needs to know what the cut off is for a 5S pack. It clearly knows what that is for 4S and 6S because it was designed that way, but did they include 5S? I don't know, seems logical that they'd include it... but someone will have to test or Traxxas confirm. There isn't any reason you couldn't hook up your own low voltage warning to the balance port of the 2S or both packs. That is what I'd do to test that the ESC knows about 5S.

    And there is no reason to always use the same pair of batteries and always use them with the same car. I hope you feel free to re-use your batteries in other vehicles, what a waste otherwise.
    Last edited by fryfrog; 12-22-2015 at 04:08 PM.

  12. #12
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    Quote Originally Posted by fryfrog View Post
    I think you're mixing a few things up.

    There is nothing wrong with using a pair of 2S batteries to make 4S. There is nothing wrong with using a pair of 3S batteries to make 6S. This is exactly what the X-Maxx and plenty of other vehicles do. There is *also* nothing wrong with doing the same thing with a 2S and a 3S to make 5S.

    But you're right about some things. The batteries should be very similar (nothing in real life is identical, even the cells inside your 2S or 3S pack). Each individual cell should be very close to the same capacity (both in a single pack and between both packs). As an example, a 2S 5,000 mah and a 3S 5,000 mah. They should start in similar charge states. They should have similar discharge capacity. You're right that you shouldn't just rely on the specs of the battery, but even in the same brand or "identical" pack, these could be different so it might be worth a charge/discharge cycle to confirm *any* pair of batteries you'd use.

    For the low voltage cut off, it has nothing to do with the mixing of packs. It isn't that it detects the 2S being depleted, it needs to know what the cut off is for a 5S pack. It clearly knows what that is for 4S and 6S because it was designed that way, but did they include 5S? I don't know, seems logical that they'd include it... but someone will have to test or Traxxas confirm. There isn't any reason you couldn't hook up your own low voltage warning to the balance port of the 2S or both packs. That is what I'd do to test that the ESC knows about 5S.

    And there is no reason to always use the same pair of batteries and always use them with the same car. I hope you feel free to re-use your batteries in other vehicles, what a waste otherwise.
    Excellent post!

    This is absolutely true. There is no difference in mixing a 2s and 3s to get 5s than mixing 2x 2s for 4s or 2x 3s for 6s, as long as you're not using mismatched capacities or C ratings.
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    All that said, Traxxas's site *does* literally say 4S / 6S. So while the ESC obviously works w/ 5S (How could it not? The voltage for 5S is right between 6S and 4S!), that may be the *only* thing that works about it.

    I pre-ordered super late, so I'm sure someone else will get to this before me... but I'll throw one of my tiny 2S and 3S batteries (for a 1/16 e-revo) in after pre-draining them close to LVC and carefully see what happens.

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    I've run 5S on my E-Revo multiple times and it always worked flawlessly.
    Like it's been said, same capacity and same discharge rate ( C rating ) and try to pair batteries as close as possible ( not a new one with one that has 200 cycles ) and you'll be good.

    When running 5S I plug a "Low-Voltage Alarm" on the balance wire of each battery, never had any issues.

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    I run nothing but 5s in my Emaxx for the last 5 years and don't treat the batteries any different than normal. I mix them into different cars at different times as well and just make sure they always balanced.

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    Like mentioned above, I run 5s religiously in my Emaxx every run, 7200mAh 2s and 7200mAh 3s, both 60c and both spc lipos. I run my truxk down to lvc evey run and balance charge those lipos, they are great every time. Like what was said, long as they are same mAh, and dishcarge and same manufacturer, then there shouldnt be a problem.

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    Quote Originally Posted by Fuglio View Post
    A 3s battery could be 6 cells ran in a combination of series and parallel to get the desired Amp Hrs. You wouldn't run a 3s 8000 and 3s 5000 together either.... it may not be a big deal but when it comes to an online fourum that people come to for advice we gotta give good advice.

    I see somone that wants to mix batteries as a person that wants to save money. It would be a shame for somone in that financial situation to end up with 2 non working batteries and some puffed cells from over discharging.
    You're absolutely right, just like you shouldn't run an 8,000 mah 3S and a 5,000 3S to get 6S... you also shouldn't run an 8,000 mah 3S and a 5,000 mah 2S to get 5S. And every time I've mentioned this or seen it mentioned, it has always been said that you should follow the same guidelines for running a pair of "identical" batteries.

    And so what if someone wants to save money? The *reason* for running 5S doesn't matter. Maybe they think 6S is too fast and 4S is too slow. Maybe they happen to already have a 2S and 3S pack that are identical in all the ways that matter. Maybe they have two sets of 2S and two sets of 3S and instead of having one 4S session and one 6S session they'd rather have two 5S sessions.

    Just like any battery combination, if you follow some basic guidelines you'll be fine.

    Blanket statements like "charge them at the same time" and "its bad practice to mix batteries in series" and "always use them in the same car" are simply wrong and unhelpful.

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    So what does the esc recognize when you plug in a 5s pack? If the esc thinks it's 6s, then the low voltage cutoff would kick in right away as soon as voltage starts to drop. Or if the esc sees 4s then the low voltage cutoff will not kick in before the batteries are run dangerously low. If the truck runs fine on 5s, I would think the esc is seeing 4s.

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    Quote Originally Posted by forescott View Post
    So what does the esc recognize when you plug in a 5s pack? If the esc thinks it's 6s, then the low voltage cutoff would kick in right away as soon as voltage starts to drop. Or if the esc sees 4s then the low voltage cutoff will not kick in before the batteries are run dangerously low. If the truck runs fine on 5s, I would think the esc is seeing 4s.
    Yeah, good question. I'm going to make an educated guess that they didn't design an ESC from the ground up, so they're probably re-using code and components... which probably means the ESC knows about all the various LiPo sizes it could be hooked to. Does it power up with just a single 3S in the right port? A 2S? I think my Summit does, but I don't recall if I've ever actually tried *driving* it w/ 2S.

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