How many amps constant?

[Erin]

Tried searching, but wasn't finding quite what i needed.

Running a berg, dual micros, 2-41 turns, bec @ 7.4, and gens ace 450mah 25c packs.

In a bind while steering, I'm starting to see servo stall, which wasn't there before switching to these smaller batteries.

My question, these are 25c( 25 x .45), so that is 11.25 amps constant, correct? but since they can be charged at 5c, can they put out a greater load, such as 56.25amps (25 x .45 x 5)? i'm sure the stall is coming from the batteries, as they are the new variable, just haven't read of anyone who switched to these having this issue.

I was running 40c 1050 c 3s packs before with no issues wat so ever.

any help would be greatly appreicated, thx

[JohnRobHolmes]

What voltage are the packs?

Those are pretty tiny to pull so much power from. Are they warm after a run?

[Erin]

They are 3s, so 12.5v fresh charge.

alot of guys have reccommended these, but none have said they were getting voltage drop.

I'd say nominally warm, maybe 85-95 degrees. not hot at all, though it was cool out where i was. haven't used them at 100+ yet.

[Charlie-III]

My personal opinion (for what it's worth) is that a 25C pack is just below the bottom limit.
If you went with a 35C or greater pack, you "may" aviod your current issue.

1-What rig?
2-Are you running an external BEC
3-If "yes" what BEC & what voltage
4-Is the BEC direct to the servo or through the RX?
5-What radio TX & RX??
6-If no external BEC, what ESC are you using?
7-What steering servo????
8-Since you are in the US, I will assume your temps are *F????

[Erin]

I understand a 25c pack is the bottom limit as i used to run 40c packs. A number of guys here have been using these packs w good results. Hence the reason for my question as i haven't seen this issue come up.

My bec is direct wired to servo at 7.4v. 4pk, dual micros.
rig weighs 5lbs 8ozs rtr.

I guess what i want to know is the low mah pack the reason its dropping voltage? If i was to run a larger mah pack w same c rating would things be different?

[Charlie-III]

Originally Posted by Erin

I guess what i want to know is the low mah pack the reason its dropping voltage? If i was to run a larger mah pack w same c rating would things be different?

Early in a run?? NOPE
Late in a run?? Yep

The mah rating is how long a pack can support a given load, the more mah (yes, you likely already know this) the longer it can support the load.
The "C" rating allows for spikes in load. The bigger the "C" the better it deal with loads.

[JohnRobHolmes]

Yes, either more mah or a bigger discharge rating should help assuming the battery is at fault.

My thoughts on the cause:

Battery is dropping and the BEC is not following the drop fast enough to keep the output voltage.
Servo is damaged
BEC is damaged


Hard to say what it is, but if you switch packs you can at least rule something else out.

[Erin]

Pretty sure its these packs because when i run the old 1050's theres no stall.

I only noticed it when bound up in a notch trying to turn and level the axle. Everywhere else they seemed fine. Could dig onto a ledge and lift the rig with steering without issue.

Guess i just need to be more precise with certain lines from now on lol

Thanks for the input

[ThunderVP]

Are you sure they were not recommending 850mah packs? That's what many of the guys in my club run for comp packs in their MOAs.
Two 540 motors and a high torque servo will easily draw more than 11A when they start working a little bit.
Another thing to concider is a 450mah pack even drawing as little as 5A constant will only last about 5 1/2 minutes before the LVC kicks in.
Your 1050 packs can put out a constant 40A and would last 12 minutes under the same 5A load. I'm sure you normally get 15-30 minutes run time on the 1050s under normal start & stop crawling since the current draw would not be constant all the time.

[Erin]

Originally Posted by ThunderVP

Are you sure they were not recommending 850mah packs? That's what many of the guys in my club run for comp packs in their MOAs.
Two 540 motors and a high torque servo will easily draw more than 11A when they start working a little bit.
Another thing to concider is a 450mah pack even drawing as little as 5A constant will only last about 5 1/2 minutes before the LVC kicks in.
Your 1050 packs can put out a constant 40A and would last 12 minutes under the same 5A load. I'm sure you normally get 15-30 minutes run time on the 1050s under normal start & stop crawling since the current draw would not be constant all the time.

Nope these guys switched from 850's to the 450's. Everybody seems real happy with them, hence my surprise when it happened. I've got 5 packs thru now, so will do some more testing yet. My current setup is even lighter then it was before.

[Illeagle]

Erin, I have almost an identical setup to yours and I have experienced the servo stall also. I would also attribute it to the 25c gens ace. So far thats the only down side I have noticed. No problem running the motors but I have stalled my 7950 and I'm 99% sure its the battery. I went from the 45c 850mah TP packs and experienced the problem almost immediately I went to the Gens ace. I would say going from a constant 38amps with the TP down to only 11amps with the Gens is a substantial factor. Not sure if Im going to live with it or go back to the TP's. Good luck with yours

[Erin]

Originally Posted by Illeagle

Erin, I have almost an identical setup to yours and I have experienced the servo stall also. I would also attribute it to the 25c gens ace. So far thats the only down side I have noticed. No problem running the motors but I have stalled my 7950 and I'm 99% sure its the battery. I went from the 45c 850mah TP packs and experienced the problem almost immediately I went to the Gens ace. I would say going from a constant 38amps with the TP down to only 11amps with the Gens is a substantial factor. Not sure if Im going to live with it or go back to the TP's. Good luck with yours

I'm kinda thinking the same thing. The size is great, so I'm going to give them a comp or two to make up my mind. We have so much traction at most of our sites that it does concern me though.

[SuperRoo]

Drop the voltage down on the BEC to 7.0 volts (or lower) and see the difference. If your running a Hitec servo the torque loss wont be that great a difference compared to the current saved.