3s 5000mah lipo questions

[Steelfish]

ok folks, I was running 8-cell nimhs and 3s LIFE batts, my life batt is now dead and my current motors dont run on the nimh (xerun 3656sd 3400kv), so...

I now jumping finally to the lipo powa.. I have read and read about lipo cares, etc but I still have few questions.

1. Im running a rtr hpi fs-50 servo on my wraith and BHR 120a ESC, if I go 3s lipo do I need a bec to keep running the servo? I know is not the best but since Im just bashing I like it and dont want to burn it on the 1st run.

2. Im a every-two-weekend RC warrior, just bash with my nexx10sc 4x4 and my wraith, thats why I was happy with tacon motors and nimh power, but now I still dont know after bashing with my lipos, do I have to get home and immediately connect the battery to put it on storage mode for the next run on 15 days or can I just leave the battery at the LVC mark and next day charge it to storage voltage?

3. my local weather is like Vegas, Nv. but Im in Baja, Mex, here it can reach 115-125*f at shadow in summer time, where and on what kind of recipient I can leave my batts stored for 1 month other than inside the fridge? (my wife is a chemistry and will kill me if I put anything that is not food on the fridge)

 

[Trubble]

1. Im running a rtr hpi fs-50 servo on my wraith and BHR 120a ESC, if I go 3s lipo do I need a bec to keep running the servo? I know is not the best but since Im just bashing I like it and dont want to burn it on the 1st run.

You're up over 200oz. and you don't already have a BEC? Why?

2. Im a every-two-weekend RC warrior, just bash with my nexx10sc 4x4 and my wraith, thats why I was happy with tacon motors and nimh power, but now I still dont know after bashing with my lipos, do I have to get home and immediately connect the battery to put it on storage mode for the next run on 15 days or can I just leave the battery at the LVC mark and next day charge it to storage voltage?

Modern LiPos are pretty stable, if you bring 'em home at LVC voltage they should be fine for a while. Charge 'em back up to storage voltage at your next convenience.
Just make sure when you're done running, you completely unplug your LiPos. Don't leave 'em in the rig ("but I turned the switch off" is not the right answer), don't leave balancers, 'conditioners', or voltage monitors/LVAs plugged into the balance tap.

3. my local weather is like Vegas, Nv. but Im in Baja, Mex, here it can reach 115-125*f at shadow in summer time, where and on what kind of recipient I can leave my batts stored for 1 month other than inside the fridge? (my wife is a chemistry and will kill me if I put anything that is not food on the fridge)

Mine are in LiPo charging sacks, hanging on hooks on the wall in the basement. If you don't have a basement, I'd look for (preferably) an interior room (ie not along an exterior wall if possible) such as a coat closet, linen closet or pantry. Bathrooms and laundry rooms are generally too damp, avoid those. If you were going to store these things outside, under a carport or in a garage, I'd recommend a cooler with a tight fitting lid to keep 'em clean and slow any temperature swings. Even just a cheap styrofoam cooler would be fine.
Basically keep 'em out of the sun, and if possible, in an area where temps won't fluctuate wildly.





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[Steelfish]

You're up over 200oz. and you don't already have a BEC? Why?
.

- hmm well first of all, I considering myself new to the hobby, I though you only need a BEC if your servo is requiring 7v or more to perform good, as far as I know this is a 6v servo and I think it turns really good but now I thnki I need to see how this servo would act with a Bec, if I get one how many volts do I have to send to the servo?

Modern LiPos are pretty stable, if you bring 'em home at LVC voltage they should be fine for a while. Charge 'em back up to storage voltage at your next convenience.
Just make sure when you're done running, you completely unplug your LiPos. Don't leave 'em in the rig ("but I turned the switch off" is not the right answer), don't leave balancers, 'conditioners', or voltage monitors/LVAs plugged into the balance tap.
.

nice tips, I'll keep that considered for when my lipos arrive. although I have never leave the batts plugged even the nimhs or Life batts were disconnected and put them on special compartment on my tool box.

Mine are in LiPo charging sacks, hanging on hooks on the wall in the basement. If you don't have a basement, I'd look for (preferably) an interior room (ie not along an exterior wall if possible) such as a coat closet, linen closet or pantry. Bathrooms and laundry rooms are generally too damp, avoid those. If you were going to store these things outside, under a carport or in a garage, I'd recommend a cooler with a tight fitting lid to keep 'em clean and slow any temperature swings. Even just a cheap styrofoam cooler would be fine.
Basically keep 'em out of the sun, and if possible, in an area where temps won't fluctuate wildly.
.

thanks for pointing this out, I have read many things where people put their lipos, like fire-safe boxes, ammo boxes, ceramic pots with a bag of sand of top of the lipos, etc. I really was lost what can work for me on my high temp weather, on hand I have an ammo box 8x6x4, a small cooler (sixpack size)

 

[envious8420]

ammo can in a cool place is fine. i have 20+ lipos in my ammo can, i store it in the basement right on the floor. the cooler floor pulls any extra heat from the box and its never more than 70* inside the box.

just out of curiosity, why wont your gear run on nimh?

 

[Steelfish]

just out of curiosity, why wont your gear run on nimh?

I dont know.. I think this xerun 3656sd 3400kv is as power hungry as the tekin pro4 and tenshocks 411.

the settings on the ESC are correctly on NO LVC to run nimhs but they just last 2 minutes driving slowly and smooth on the wraith on the same BL combo and then just go tttrrrrr trrrrr and car stops try to move but just shakes (trrrrrr), the punch on the ESC is set on the lower 1

an identical same motor is installed on my nexx10sc but the punch is set on 7 (to have faster launching) and the car just move 2 feets and then starts doing the same shaking and dont move..

BUT if I put the Life battery there.. it comes to life and make some long rooster tails all over.


with my tacon motor 2700kv 3660 and my ACE ripper 540 2-pole 3300kv motor they run on nimh really good and last 15-20 minutes. go figure.

 

[Charlie-III]

Are you using the same packs on each ESC/motor combo?

If yes, then maybe some combos draw enough power to overdraw the packs (which are likely getting tired).

If no, what connectors are on the packs? If Tamiya, that is likely part of the issue there.

Some set-ups may have cold solder joints or other issues preventing high amp draws.

ESC's really don't care what chemistry creates the voltage, it cares about:
-What voltage
-What ampacity can be provided (wire size, connector type, "C" rating or mah, etc all contribute to ampacity).

 

[Steelfish]

Are you using the same packs on each ESC/motor combo?

no right now, I was using those motors on my 2wd Ruckus and the ran like if it was stolen, that ruckus is now retired so Im using same ESC on my wraith with the xerun 4-pole sensored and it just run 2 minutes and died.

If yes, then maybe some combos draw enough power to overdraw the packs (which are likely getting tired).
that I what I think, xerun motor must be as power hungry as the tenshock or tekin pro4


If no, what connectors are on the packs? If Tamiya, that is likely part of the issue there.
- using traxxas connectors currently

Some set-ups may have cold solder joints or other issues preventing high amp draws.
- Im doing all the soldering and I can say they are really good

ESC's really don't care what chemistry creates the voltage, it cares about:
-What voltage
-What ampacity can be provided (wire size, connector type, "C" rating or mah, etc all contribute to ampacity).
- yeah I understand this so, I think the motor the culprit for running nimh right now

 

[Trubble]

- hmm well first of all, I considering myself new to the hobby, I though you only need a BEC if your servo is requiring 7v or more to perform good, as far as I know this is a 6v servo and I think it turns really good but now I thnki I need to see how this servo would act with a Bec, if I get one how many volts do I have to send to the servo?

Alright, cool. I just know when I was running my stock servo, with as little as 7 cells (NiMh), I had a lot of problems with the truck stalling and/or cutting out. If it's workin' fine for you, then I can see why you wouldn't have one yet.

I put in a BEC and fed the stock servo 7.0 volts, snappy, but didn't last very long. Taking the chance with a <$20 stock servo, I didn't feel too much guilt. But with a mid/high-end servo like you're running, I'd recommend just sticking to the 6.0 volts it's good for.





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[Johnnysplits]

Another reason to run a BEC is to take the additional load off the esc. It will run cooler and it already has enough work to do, why add more stress to it.

 

[Olle P]

... my current motors dont run on the nimh (xerun 3656sd 3400kv), ...

I can't see why the motors won't run. :shock:

... do I need a bec to keep running the servo?

I though you only need a BEC if your servo is requiring 7v or more to perform good, ...

A BEC is a voltage regulator that can only bring the (battery) voltage DOWN to a level acceptable by whatever you hook it up to.

A servo rated for "6.0V" can be fed directly from a 6V NiMH battery (charged to 7.0V when full).
It can't be fed from a >7V nominal voltage battery without going bad, and that's when a BEC is handy.
The typical user will then utilise the BEC built into the typical ESC (providing some 5-6V), but that BEC can't handle the currents drawn by strong servos.
Therefore we crawler guys use a separate BEC that can deliver more current to the servo.

... do I have to get home and immediately connect the battery to put it on storage mode... or can I just leave the battery at the LVC mark and next day charge it to storage voltage?

There are two don'ts that come into play with storage:
1. Never ever get any one cell discharged to below 2.75V at no load. (Temporary dips during load are acceptable.)
2. Don't store LiPos at >3.80 V/cell or they will have a permanent capacity loss.

Typically the LVC is set in the region 3.0-3.3 V/cell and measured as the total voltage on the leads. Unless one cell is much worse than the rest no cell will discharge to below 2.75V before the LVC is triggered.

This means that as long as the battery pack is okay you can safely wait for a day or two before adjusting the charge level to 3.8V.
If you're not quite sure on the battery condition you can use a cheap cell checker after the run to make sure all cells are above 2.9V before leaving the battery pack for a day or two.

Personally I'd feel more stressed to discharge the cells for storage if they are at 3.95V than to charge them if they're at 3.65V.

 

[Steelfish]

I can't see why the motors won't run. :shock:

me either..
more strange is that I have the same ESC/motor xerun 3400kv on my wraith and nexx10sc and my wraith can run for two minutes on nimh 8-cell 5000mah for two minutes and then stops but on the nexx10sc 4x4 it just dont run at all, it just stall but if I put the life batt pack on it run like mad.

A BEC is a voltage regulator that can only bring the (battery) voltage DOWN to a level acceptable by whatever you hook it up to.

A servo rated for "6.0V" can be fed directly from a 6V NiMH battery (charged to 7.0V when full).
It can't be fed from a >7V nominal voltage battery without going bad, and that's when a BEC is handy.
The typical user will then utilise the BEC built into the typical ESC (providing some 5-6V), but that BEC can't handle the currents drawn by strong servos.
Therefore we crawler guys use a separate BEC that can deliver more current to the servo.

well my servo is rated for 6v, I know some strong servos need 7v to work at their peak, but I think I will get a servo for my wraith anyway.

There are two don'ts that come into play with storage:
1. Never ever get any one cell discharged to below 2.75V at no load. (Temporary dips during load are acceptable.)
2. Don't store LiPos at >3.80 V/cell or they will have a permanent capacity loss.

Typically the LVC is set in the region 3.0-3.3 V/cell and measured as the total voltage on the leads. Unless one cell is much worse than the rest no cell will discharge to below 2.75V before the LVC is triggered.

This means that as long as the battery pack is okay you can safely wait for a day or two before adjusting the charge level to 3.8V.
If you're not quite sure on the battery condition you can use a cheap cell checker after the run to make sure all cells are above 2.9V before leaving the battery pack for a day or two.

Personally I'd feel more stressed to discharge the cells for storage if they are at 3.95V than to charge them if they're at 3.65V.

cool, thanks for this tips I will have them on hand for when my Lipo arrive, I already have 2 cell checkers with a loud alarm that I was using with the Life batts.

what would you recommend to put the lipos (storage box) when are going to be used every other week?

Another reason to run a BEC is to take the additional load off the esc. It will run cooler and it already has enough work to do, why add more stress to it.

this really sold me the idea of the Bec