help please , lipo cutoff for stock e-revo with 2s1p packs.

[Andreas_BL]

my friend got the e-revo and we bought two lipo battery packs 2s1p 4000mah 25c , what do you recommend for lipo cutoff so we do not destroy our batteries ??? thanx in advance .....

[clowkoy]

Novak smart stop 2S or 4S.

[Self Medicated]

I was told by someone on here that the "2S car lipo deep discharge protector" that True RC sells works good. Just connect it to the battery on the BEC side of your ESC, as that battery will drain faster than the other, thus protecting both batteries. I have mine ordered and waiting for its arrival so I haven't tried it out yet, but the reports I have heard are good.

Linky (you need to click on "Connectors & Misc", then scroll about halfway down the page):
http://home.comcast.net/~truerc/read...eady_packs.htm

[GotRevo?]

4s - that's if the batteries are wired together in a series, right?

2s - that would be to put on one of the 2s1p packs...presumably the BEC side battery because it will drain a little faster, right?

[HoovHartid]

4s - that's if the batteries are wired together in a series, right?

2s - that would be to put on one of the 2s1p packs...presumably the BEC side battery because it will drain a little faster, right?

No....4s if you run parallel....2s if you run series...

the E-revo FAQ is your friend. LINK


look at post #72;
http://monster.traxxas.com/showpost....4&postcount=72


all the wiring diagrams you need for what you are doing

[Andreas_BL]

i will connect them in series 14.8v , and i want to ask why the bec side battery discharges quicker .
r u sure about that ,?
so i only need a 2s cutoff. ?
, ok but somewhere i read that the novak cutoff some incompatibility issues with the evx .

[HoovHartid]

i will connect them in series 14.8v , and i want to ask why the bec side battery discharges quicker .
r u sure about that ,?
so i only need a 2s cutoff. ?
, ok but somewhere i read that the novak cutoff some incompatibility issues with the evx .

the bec side discharges quicker because that is the side that powers your servos, and receiver along with the motors....the other side just powers the motors IIRC.

look at the links I sent you.... the diagrams will set you up correctly depending on the way you decide to go.

If it were me....I'd want to protect both batteries, so I'd wire using a 4s LVC.


but in reality...i sold my evx-2 before I ever ran it and went to a brushless set-up with an ESC that had a cut-off built in....so my first hand knowledge here is limited. I do know, however, that the wiring diagrams in the e-revo faq are spot on.

[Andreas_BL]

just picked up from ebay this
and 2 of these http://cgi.ebay.com/ws/eBayISAPI.dll...m=200308168117

what do u think ??

[GotRevo?]

My understanding, is that series wiring before going into the ESC will combine the total number of cells, while capacity remains unchanged. In this case, OP has two 2s1p 4000mAh batteries. In a series, the ESC sees all four of the cells for a total of 14.8V and 4000mAh. I actually asked this question in another thread, but it was never answered, so I'll ask it again. How is wiring up two 2s1p 4000mAh batteries in series with one another before going into the ESC any different than wiring one battery into each of the two leads that go into the stock E-Revo ESC?

If the same two battery packs were wired in parallel with one another before going to the ESC, wouldn't the ESC only see 2 cells (7.4V), but double the capacity (8000mAh)?

If my understanding of series and parallel are correct, why would one use a 4s LVC if OP's batteries were wired in parallel, and a 2s if OP's batteries were wired in series (that's the impression I got from your response to me)? After all, the pic you linked me to even shows 2s packs wired in series before the ESC, and a 4s LVC.

[Self Medicated]

I looked at the manufacturers website for the CellShield and at the bottom of the product page it said this:

"CellShield is intended for aircraft with 0-100% style one direction only throttle. A future product will be aimed at cars."

[Andreas_BL]

I looked at the manufacturers website for the CellShield and at the bottom of the product page it said this:

"CellShield is intended for aircraft with 0-100% style one direction only throttle. A future product will be aimed at cars."

U R 100% right . i must send him an e-mail to abort .. thanx a lot

[Andreas_BL]

so , what about the novak cut off , ? is it compatible with the evx-2 ????

[Self Medicated]

I don't know about the Novak Smart Stop, but here is a link to some ebay sellers that have the deep discharge protector I mentioned earlier:

http://toys.shop.ebay.com/items/_W0Q...R&_osacat=2562

Only good reports from users so far.

[Andreas_BL]

cool , i ll try one of those , lot cheaper 2..

[Andreas_BL]

Threshold for deep discharge protection : 2.6V/Cell, 2.85V/Cell or 3.1V/Cell (Correspondingly, the total threshold for a 2S Li-Po battery pack is 5.2V, 5.7V or 6.2V)

what about that ??? i think the best setting is the 3.1v per cell just to be safe. what do you think ????

[Revo¹]

GotRevo?, I answered your question in the other thread

[Self Medicated]

Threshold for deep discharge protection : 2.6V/Cell, 2.85V/Cell or 3.1V/Cell (Correspondingly, the total threshold for a 2S Li-Po battery pack is 5.2V, 5.7V or 6.2V)

what about that ??? i think the best setting is the 3.1v per cell just to be safe. what do you think ????

Correct. I talked to Dan at True RC and he recommended using the highest setting.

[HoovHartid]

My understanding, is that series wiring before going into the ESC will combine the total number of cells, while capacity remains unchanged. In this case, OP has two 2s1p 4000mAh batteries. In a series, the ESC sees all four of the cells for a total of 14.8V and 4000mAh. I actually asked this question in another thread, but it was never answered, so I'll ask it again. How is wiring up two 2s1p 4000mAh batteries in series with one another before going into the ESC any different than wiring one battery into each of the two leads that go into the stock E-Revo ESC?

If the same two battery packs were wired in parallel with one another before going to the ESC, wouldn't the ESC only see 2 cells (7.4V), but double the capacity (8000mAh)?

If my understanding of series and parallel are correct, why would one use a 4s LVC if OP's batteries were wired in parallel, and a 2s if OP's batteries were wired in series (that's the impression I got from your response to me)? After all, the pic you linked me to even shows 2s packs wired in series before the ESC, and a 4s LVC.

ok.... I realize the confusion comes from my first answer....because I didnt complete the answer. So let me apologize for that

When you connect two bateries to the EVX-2 it automaticly connects them in a series internally. In order to add a lvc in this situation (without using a jumper on one side) the best solution is a 2s cutoff. But this leaves the other battery w/o a LVC. Most people believe this does not matter because the bec side will drain faster than the other, so as long as its connected on the bec side, you should be fine. Wiring like this would look like the following;



I, however, would feel safer if I had both batteries protected. When I mentioned 4s cutoff being used for parallel I was refering to wiring like this;


I see that it was confusing now, because it doesnt apply to the OP's question. oops!

However (and here's the part I left out earlier ) You can use a 4s cut off and still protect both batteries if you wire like this;

It uses a series connection on the BEC side and a jumper on the other. This allows both batteries to be protected.

sorry for the confusion. I hope this helps clear it up

[Andreas_BL]

what about this ? : if you install a 4s lvc with the positive cable to one connector of the battery and the negative cable to the other connector.
i say that because the speed control conects them in series inside. what is the point of pouting the jumper..

like this ::

[GotRevo?]

Whew! I was halfway worried I had everything backwards about series/parallel for a little bit when I saw your first answer. But everything you just said was exactly how I understood it to be. I've still got a lot to learn. baby steps...baby steps.

Except you did point out something that I hadn't thought of, and let me make sure I'm getting it right: it's better to wire two batts in series/parallel depending on one's application onto the BEC lead of the ESC (and a jumper on the non-BEC side) so that the LVC is protecting both batteries.

[HoovHartid]

what about this ? : if you install a 4s lvc with the positive cable to one connector of the battery and the negative cable to the other connector.
i say that because the speed control conects them in series inside. what is the point of pouting the jumper..

I'm not positive, but I dont think that will work.

There isnt anything to close the circuit going to the lvc....you could be asking for burnt wires

BrianG would know.

Except you did point out something that I hadn't thought of, and let me make sure I'm getting it right: it's better to wire two batts in series/parallel depending on one's application onto the BEC lead of the ESC (and a jumper on the non-BEC side) so that the LVC is protecting both batteries.

Thats my opinion. some may disagree.

[GotRevo?]

And I may be wrong for doing so, but I hold your opinion in high regard.

[martin_dk]

However (and here's the part I left out earlier ) You can use a 4s cut off and still protect both batteries if you wire like this;

It uses a series connection on the BEC side and a jumper on the other. This allows both batteries to be protected.

Just to make sure: in order for both batteries to be protected they still need to start off with an equal charge right (a bit like the bec-side lvc option)? Else the batt with the lowest voltage might drop too low while driving before the LVC kicks in.

[skeppley]

^
Yup, both packs must be fully charged and balanced before using. Never run a pack that was already used or drained with a fully charged pack.

[skeppley]

I'm still not convinced that wiring the EVX2 like this is a good idea. The BEC is designed to run off of 1 battery pack and is expecting 7.2 to 8.4 volts.By doubling up the volts on the BEC side of the ESC, your just asking for trouble.
If Traxxas had a high voltage BEC inside the ESC, I dont think that they would have wired it to only one side of the battery inputs.

This is just something to keep in mind when doing this.

[fmj40]

Skeppley, I think you may be right... the above diagram shows a series/parallel circuit and if I understand the evx2's innards.. you'll be showing the full series voltage on the bec side of the esc. As Chinsy as these esc's are, I doubt the bec is designed to handle that full voltage here.. but then, I know some have used it, just don't know how well they've held up.
Edit:, after looking at my comments I realized that all legs of the ckt are series, no parallel.. sorry about that, that is, the batts are wired series outside of the esc, and the internal wiring of the esc is series. Personally I don't see any pluses to wiring this way.

[skeppley]

Yeah, your better off just using a 2S cutoff on the BEC side. That way the internal BEC is still gonna get the factory voltage.

[martin_dk]

Yeah, your better off just using a 2S cutoff on the BEC side. That way the internal BEC is still gonna get the factory voltage.

That was kinda what I thought, as the series setup doesn't give full low voltage protection anyway, you might as well go with the lvc on bec side option since thats closest to the default setup.

[Hillbillymedic7]

I tried this in two different trucks and the Jumper idea didn't work for me....I ended up doing the one sided LVC with the 2s Novak Smart-Stop.....worked until my motors burnt out. Now I'm BL in both.

[GMRC]

when i start running lipo batteries i still want to use my nimh packs to for running in water and stuff wut is there a way to disable the LVC without switching a bunch of wires around. or opening the waterproof reciver box every time. (thats where i plan on putting the LVC at) if u add a switch in on the LVC - wire would that disable it or would that stop the truck completley.