RoboSavvy Forum

Should I discharge the Battery?

2006-10-04T09:39:50+01:00

I've been playing with li-po's for my khr-2.

I did design a circuit to turn the robot off when the battry got low. the only problem was that I couldn't get the components to be very small. if you look at the rating you need them to be 5-15A that means that they will be quick big. So I just used the standard low warning led that you can just get from a rc shop. I mounted it in his head and turn the bot off then it comes on. not the best solution but simple and small.

bren

Statistics: Posted by Robo1 — Wed Oct 04, 2006 9:39 am

Should I discharge the Battery?

2006-10-04T01:52:10+01:00

I’ve googled but can’t find a cut-off for a 7.4v LiPo. At least nothing applicable for the RN-1. Certainly someone here must be using a cut-off for LiPos? Maybe I’m just using the wrong keywords in my searches.

I’ve read about the International Rectifier iP1203 Buck converter in another thread. Sounds great however, I’d like something more simple and lower cost.

Where can I order a small rinky dink voltage cut-off to solder between my LiPo and RN-1? Does such a thing exist?

Statistics: Posted by Zembot — Wed Oct 04, 2006 1:52 am

Should I discharge the Battery?

2006-10-01T19:04:45+01:00

Is the MPI ACC134 6-Volt Regulator the answer?

I was actually refering to the ACC234 for Li-Po Regulator, but No, you're right. I don't think either of 'em is what your looking for. You'll want an actual voltage cut-off circuit. I guess we did get a little side-tracked talking about regulators huh?

I do agree w/ Hivemind. I wouldn't go w/ a 5.5v cutoff either. I start charging typically before 3.3v/cell.

Statistics: Posted by bauermech — Sun Oct 01, 2006 7:04 pm

Should I discharge the Battery?

2006-10-01T18:14:50+01:00

bauermech wrote:
This one is one I was considering:
http://www.maxxprod.com/mpi/mpi-21.html
...15 Amp continuous, 30 Amp peak, adjustable output....

I could use some clarification. How would it react with a 2-cell 7.4 LiPo? If I understand correctly, when voltage drops below 6v it will negate one of the cells? So in effect, I’d have a voltage cutoff because the voltage would have dropped by 50 percent (with a 2-cell 7.4v LiPo)? Which is fine with me. I’m looking for something that will save my 7.4v Lipos from discharging below 6v in the RN. Is the MPI ACC134 6-Volt Regulator the answer?

Statistics: Posted by Zembot — Sun Oct 01, 2006 6:14 pm

Should I discharge the Battery?

2006-09-30T21:13:51+01:00

thanks Matt.they look more than good for the job.Nice to see they did there homework and selected the right colour for the heatsink !

Statistics: Posted by rep001 — Sat Sep 30, 2006 9:13 pm

Should I discharge the Battery?

2006-09-30T15:44:53+01:00

This one is one I was considering:
http://www.maxxprod.com/mpi/mpi-21.html
...15 Amp continuous, 30 Amp peak, adjustable output....

Statistics: Posted by bauermech — Sat Sep 30, 2006 3:44 pm

Should I discharge the Battery?

2006-09-30T09:16:10+01:00

I think you are correct in me not finding one,They are all rated much lower as i have been looking. so, if anyone has had success and can direct me to a stockist then rock on.

Statistics: Posted by rep001 — Sat Sep 30, 2006 9:16 am

Should I discharge the Battery?

2006-09-29T21:06:41+01:00

Well a default setup (6v) each servo draws 1.2A at max current (.2A for sitting), so if you have all 18 (default+matts grippers) servos loaded then you are drawing 21.6A total. But... realistically you will only have what? 6-8 at max current and the rest might be moving but without much resistance, do some math...

8 loaded is 9.6A and then 10 not loaded is 2A, so you get 11.6A total if you have 8 stalled... If i were you I would look for a regulator with a 15A rating or higher. You may not find one, but thats what you should be looking for.

Hope that helps

Statistics: Posted by hivemind — Fri Sep 29, 2006 9:06 pm

Should I discharge the Battery?

2006-09-29T12:05:06+01:00

Voltage aside,what sort of amp draw are we looking at through a lipo saver as there are many available through the model shops and i have a box of them from electric flight use ? i am thinking in the ranges of 1-5amp maybe........

Statistics: Posted by rep001 — Fri Sep 29, 2006 12:05 pm

Should I discharge the Battery?

2006-09-29T02:14:32+01:00

I wouldnt do the 5.5v if i were you because you could damage the battery. I think that 6v is the right number to go with.

Statistics: Posted by hivemind — Fri Sep 29, 2006 2:14 am

Should I discharge the Battery?

2006-09-29T01:25:05+01:00

Hey everyone,
I’m looking for a 6v cutoff that isn’t overly complicated to install. Will this work? I’m ready to give it a try. The price is right.

CaptKill4Fun wrote:
#43355 - Duralite Low Voltage Cut Off PRICE: $24.95 USD
The Low Voltage cut off will turn the battery off at a safe 5.5 volts. Protects your battery.

Is 5.5v actually too low for a 7.4 LiPo? If so, what would a Robosavvy recommend?

Statistics: Posted by Zembot — Fri Sep 29, 2006 1:25 am

Should I discharge the Battery?

2006-08-12T13:39:30+01:00

Also, I would not trust my expensive lithium polymer batteries to a AtoD monitor subroutine running in robobasic. The robobasic template only monitors the battery voltage at idle not under load. This choice may be ok for NiMH batteries but for lithium polymer batteries I think it is unwise.

Statistics: Posted by Bullit — Sat Aug 12, 2006 1:39 pm

Should I discharge the Battery?

2006-08-12T13:35:35+01:00

CAUTION!
Do not dischage a 7.4V lithium battery below 6V or the battery will be permanently damaged!!

I have many years of experience with lithium polymer batteries and I have lost many expensive batteries due to over discharging.

Batteries that are damaged are also prone to failure during charging. Which as stated above can cause a fire. There are many horror stories doccumented on r/c forums of people losing automobiles and homes due to fires that start by overcharging lithium polymer batteries.

Please be careful.

Statistics: Posted by Bullit — Sat Aug 12, 2006 1:35 pm

Should I discharge the Battery?

2006-09-29T02:40:50+01:00

Hi,

Actually, if anybody plans on using Lithium batteries LiPoly or LiIon it is much safer to use a real automatic Low-Voltage CutOFF switch ... this protects both the batteries from too much drain and also helps to prevent exploding batteries when you try to re-charge your damaged Lithium battery ...

My house and contents costs too much money to rely on a toy LED circuit when I can better protect it with a $25 part designed exactly for the job ...

#43355 - Duralite Low Voltage Cut Off PRICE: $24.95 USD
The Low Voltage cut off will turn the battery off at a safe 5.5 volts. Protects your battery.

5.5V LowVoltage CutOFFf (2.75V/cell) is the worst-case cutOFF when the operator isn't aware the batteries are running down ... a 5.5V cutOFF is still within the normal operational range of LiPoly/LiIon batteries ... however, the lower you take the batteries the faster they age ... and is why some users prefer 6V cutoff to get the most battery performance/$.

One thing to know ... millions upon millions of R/C hobbyists use these regulators in their cars, tanks, trucks, trains, helicopters and airplanes on NMiH's and LiPoly's ... If somebody finds something better please post a link in the forum so we can find it ...

BTW, I'm trying to get Duralite to manufacture a new combination Low Voltage CutOFF with a 6V Regulator for Lithium battery use in our bots ... I've specified two (JST type) inputs from the batteries and one output to the RoboNova-1 power connector ... so if you buy from Duralite ... please send a note to Jack Price and ask for that specific device ... I think they only need a few people calling and asking for it to get it out of the conference room and into production for the robotic world ...

Statistics: Posted by CaptKill4Fun — Sat Aug 12, 2006 1:16 am

Should I discharge the Battery?

2006-08-12T00:28:48+01:00

I believe the low-voltage regulator has been included only in the newer models of the RN-1, as mine stock, and still now, does not have one, my ports are busy anyway though.

But if you were to use the low-voltage resistors and the stock template program it still would not work, the stock battery is 6v and probably will not be damaged by dropping a little bit, where a 2-cell lithium battery is 7.4 and needs to remain relatively close to that voltage. THe stock template program (i could be off slightly here) triggers the blinking LED at 3v which is half of the battery. If a lithium got this low it would be cooked. You would need to change the program so it triggers closer to 6.9v or maybe a little higher, because you dont want to ruin the battery.

Granted I have kind of verged off the original topic, so i apologize, but if you are feeling adventurous and want to switch to lithium which keeps a nice voltage thorughout use, and is what i will be switching to shortly, then hopefully this will help

Statistics: Posted by hivemind — Sat Aug 12, 2006 12:28 am