PDA

View Full Version : Best way to match batteries


rajiex
2010.11.29, 07:53 PM
I have seven sets of R1 Wurks 990, three sets of R1 750, two TRP 900, Peak 900 and Orion 900s. I understand voltage equals punch and MAH represents run time. I have a MAHA 9000 charger. How should I charge and discharge, and what #s should I pay attention to. Help getting confusing answers from everyone. Most qualifiers are five minutes and main are seven. I always put a fresh set in for every race.

EMU
2010.11.29, 08:05 PM
Here are a couple battery posts I wrote and I recommend reading.
http://mini-zracer.com/forums/showpost.php?p=343098&postcount=2

http://mini-zracer.com/forums/showpost.php?p=369082&postcount=2

This is a good thread...
http://mini-zracer.com/forums/showthread.php?t=28740

rajiex
2010.12.02, 08:07 PM
Emu,

Candle Power was good reading. I know I want to group the MAHs as close as possible but I have questions on voltage. Is lower better or higher volts better for punch ( or speed in mini z)

hpotter
2010.12.02, 10:43 PM
Emu,

Candle Power was good reading. I know I want to group the MAHs as close as possible but I have questions on voltage. Is lower better or higher volts better for punch ( or speed in mini z)

An easy way to decode batteries in the simplest terms is:
Voltage = Speed
maH = Capacity or runtime
IR = Internal Resistance of battery (lower equates to more punch)
Amps (Current) = Torque
Keep in mind there are also many other factors that can affect battery performance including:
Gearing
Charging method-You can charge batteries at a higher rate to get an initial boost, but will fall off quicker-charge at a lower rate and have less initial punch but will be more consistant throughout and will charge to a fuller capacity.
Also keep in mind that how you charge your batteries will dictate how long they will last-higher charge rates=less life
Something I always check on my batteries and electronics in general is heat, if I'm really hot after a run I'm either going to change my gearing or check for binding--if my batteries are coming out of the charger too hot I will lower the charge rate. I'm sure others have different opinions but this is what I go by.

bermbuster
2010.12.03, 05:37 AM
An easy way to decode batteries in the simplest terms is:
Voltage = Speed
maH = Capacity or runtime
IR = Internal Resistance of battery (lower equates to more punch)
Amps (Current) = Torque
Keep in mind there are also many other factors that can affect battery performance including:
Gearing
Charging method-You can charge batteries at a higher rate to get an initial boost, but will fall off quicker-charge at a lower rate and have less initial punch but will be more consistant throughout and will charge to a fuller capacity.
Also keep in mind that how you charge your batteries will dictate how long they will last-higher charge rates=less life
Something I always check on my batteries and electronics in general is heat, if I'm really hot after a run I'm either going to change my gearing or check for binding--if my batteries are coming out of the charger too hot I will lower the charge rate. I'm sure others have different opinions but this is what I go by.

this is good info and i will add to it....
From racing with larger scales the magic number for heat is 130 F...
any hotter than that and your destroying your batteries.
Some aaa s can take 130 F and some start weeping/venting/leaking at that temp so I personally use 120F as my indicator. In order to read temp correctly you need a thermometer (electronic ones are $10 and up)
You cannot gauge temp by feel.....
After a race if your batteries are coming off at 120F that means you are at the limit of the motor/gearing...(should be your fastest) if your hot and or slow
you have too powerful a motor/overgeared/ binding etc.....
never throw a hot battery on a charger.....but dont put really cold batteries on one either.
When a battery comes off the charger at 120F you know it has a full capacity charge.....all 4 must be around the same temp....if you have 1 cold cell it is your weakest....and if one happened to overcharge and vent....another weak cell. Not trying to confuse you....Battery technology is a serious business....
BTW I do this for fun and education....:cool:

EMU
2010.12.03, 12:29 PM
I dont use a temp gauge, but as Berm and Potter said, watch the temperature. If you cannot hold the battery without dropping it, its too hot and you wont have as much power as you would with it warm enough to hold. Plus, every time the cell is too hot to hold, it is being damaged long term.

For slower motors, you want your cells warm (120f is a great number as Berm said). Faster motors you may want a cooler cell. Warm cells have more punch, cool cells have more consistancy. For 70t class cars, I want the cells to peak right before I get on the track. This way they are nice and warm when I get them in my car.

I typically choose my charge rate by how much time I have for the next race and what class I am running. Faster motors I will charge in my Maha MH-C9000 at 1A and let trickle a little when finished. I wont have as much punch when I put them in. 70t I will charge on the Maha at 1A, and look to see when they say 'done', then pull the cell. When all four are done, I will use my LRP Pulsar charger to fully peak the cells in series at 2A right before I get on the track.

When the Maha charger says 'done', the cells are not fully charged, it switches to a trickle charge to finish the charge. Theres usually a good 50-100mah left to charge the cells. When you let it trickle, the cells will stay pretty warm for about 15-20 minutes as the cells are being topped off.

rajiex
2010.12.04, 11:49 AM
I discharged all my batteries, let them sit one day. I charged the 990s and 900 at 1A. I recorded the MAH and voltage. Very conistently, the MAHs were less than when I charged them at .8A last week. How do I get consistency out of these batteries. The 990s I bought last week and charged to 930s got only to low 800s this week. All the volts after charging were 1.44 to 1.45V.

Now I just match into sets of 4 with the least variation between cells. For example group a set of 720s togother rather than put a 800,770, 750 and 730

What #s should be a race set and what should be a practice set and what should be thrown away.

rajiex
2010.12.09, 05:27 AM
I need a stupid simple explaination on how to charge/discharge batteries and match them.

I have a MAHA C9000. I discharge at 1A and charge at .8. I got R1, Team Orion SHO, Peak, TRP. Everytime i use the batteries and attempt to match them the MAHs get lower. The cars also seem slower. Most of my batteries are less than two months old.

After charging, the 750s and 990 show almost the same MAHs and voltage. I got no hair so I cant pull it out.

egonzalez
2010.12.09, 10:11 AM
I need a stupid simple explaination on how to charge/discharge batteries and match them.

I have a MAHA C9000. I discharge at 1A and charge at .8. I got R1, Team Orion SHO, Peak, TRP. Everytime i use the batteries and attempt to match them the MAHs get lower. The cars also seem slower. Most of my batteries are less than two months old.

After charging, the 750s and 990 show almost the same MAHs and voltage. I got no hair so I cant pull it out.

You need a discharger that shows
1. average discharge voltage (AV)
2. Internal resistance (IR) (More Punch)
3. MAH (Capacity)
Charge your batteries at their 1C rating and peak them at 2C…. Exp… R1Wurks 990 I usually round off and charge all my batteries at 1amp…. Then I would peak these 1.8amps… You should discharge at higher rate like 5 amps….If you don’t have a charger that shows IR, just match your batteries based on AV and MAH. With New batteries, you won’t get true numbers until you cycle them 2 to 3 times.. Every time you charge/discharge your batteries you higher its internal resistance… This is just the nature of the battery technology. You should have race packs that only get charged/discharged once a week. When available you should charge/discharge your batteries individually and not as a pack. This would yield the best results. I usually just peak as a pack.
For stock….match your batteries in this order IR first, AV second and MAH last….
For Mod…..match your batteries in this order AV first, MAH second, and IR last…
Disclaimer: Everyone has their own opinion on matching/charging/discharging…. This just happens to be mine. Hope this helps..
Edel G.