RoboSavvy Forum

Some Questions abou the battery

2008-03-30T22:16:36+01:00

Hi there

When I use the lipo's on my KHR-2 they will dip down a couple of Volts do the the sudden demand for power. Two options to try and fix it (haven't tried yet so only my opinion).

1) try one of the newer batteries that have a 30-40 C discharge rate. I have one of these in another robot and there really good.

2) Put a big capacitor on the servo power lines.

Bren

Statistics: Posted by Robo1 — Sun Mar 30, 2008 10:16 pm

Some Questions abou the battery

2008-03-30T17:08:09+01:00

What is C for these cells ?

It really looks like they are not charged

Statistics: Posted by i-Bot — Sun Mar 30, 2008 5:08 pm

Some Questions abou the battery

2008-03-30T16:56:57+01:00

i-Bot wrote:
Did you just replace the existing battery with 3 LiPos cells ? Are you expecting the CM-5 to charge them

The charge circuit in the CM-5 is unlikely to be able to handle the charging of these, being set up for 9.6 V NiMH

A 3 cell LiPo which measures 8.6V sounds dangerous !

I didnt charge the LiPos battery by CM-5, I charged them with other charger.

And the seller says the LiPo cells can discharge up to 10C, is this value doesnt
enough for CM-5 ?

Can I directly connect the battery to the VDD and Ground pin on the Dervo Motor, then I can use 3 sets of battery for 3 strings of motor to reduce the load
of each battery???

Statistics: Posted by kongguan — Sun Mar 30, 2008 4:56 pm

Some Questions abou the battery

2008-03-30T12:41:07+01:00

Did you just replace the existing battery with 3 LiPos cells ? Are you expecting the CM-5 to charge them

The charge circuit in the CM-5 is unlikely to be able to handle the charging of these, being set up for 9.6 V NiMH

A 3 cell LiPo which measures 8.6V sounds dangerous !

Statistics: Posted by i-Bot — Sun Mar 30, 2008 12:41 pm

Some Questions abou the battery

2008-03-30T11:09:06+01:00

What is the discharge characteristic of the battery that you are using? When all 18 (or maybe 19) servos are cranking in your humanoid, it puts quite a demand for current out of the battery. The "drop" in voltage is a function of the source resistance plus your load resistance. If your source resistance is tiny compared to your load resistance, you would see minimal drop, and vice versa.

In a steady-state condition, the circuit can be modeled into a classic voltage divider. Where your series resistance shows the current sourcing capability of the battery and the parallel resistance is the load due to the servos...

If you are sure that your battery is charged fully and that the connect and wire on it is equivalent or better then the stock unit, all signs point to the battery being incapable of sourcing that kind of current...

Statistics: Posted by tom_chang79 — Sun Mar 30, 2008 11:09 am

Some Questions abou the battery

2008-03-28T10:47:30+01:00

I think everyone know about the duration time of the original battery is very short while a Humanoid Bioloid is functioning.

Then I tried to use a 3-cell Li-po battery which voltage is up to 12V while over charging on the Humanoid Bioloid, but it is weird, before I play the robot, the voltage of battery is 12V, during the playing time, it drops down to 8.6V and the Power LED on CM-5 flashes.

I check the original battery too, it is 11V, then the voltage also drops, but it is still about 10V.

How come the voltage of Li-po battery drops so much?

Did anyone replace the battery with other battery and get longer duration time successfully?

(I read the discuss about battery before in this forum, but information there is not so clear.)

Statistics: Posted by kongguan — Fri Mar 28, 2008 10:47 am