Author Topic: Battery Charging Math (Read 9110 times)

blu666z · « **on:** January 31, 2004, 01:11:59 AM »

Am I way off base here?

UA-5 draws 500mah w/ phantom power on.

Charger rate is 280mah.

So would I charge it almost 2hours(500/280) for every hour I intend to use it or longer?

-Kevin

caymanreview · « **Reply #1 on:** January 31, 2004, 01:29:11 AM »

sounds about right, what type battery -sla or rc pack? does your charger have a trickle charge once the battery is full, it then tops it off? you may want to run it a touch longer to insure full charge

280mah charge rate isnt going to cause any damage by overcharging, the extra juice will be let off as some heat correct?

my rc charger charges at 2000mah, then trickles at 50 untill topped off and the packs always get warm before it shuts off, it is an auto shutoff smart charger

blu666z · « **Reply #2 on:** January 31, 2004, 01:41:35 AM »

Its a 3000mah batteryspace pack. Charger is a 5 hour charger from Rat Shack.

I had been looking at this theard and wasn't sure if the charging to 1.5x applied to basically dead batteries or if you could apply based on how much power you intended to use.

http://www.taperssection.com/yabbse/index.php?board=25;action=display;threadid=12035;start=msg147389#msg147389

-Kevin

caymanreview · « **Reply #3 on:** January 31, 2004, 01:50:04 AM »

im not sure if the 1.5x applies to non-dead packs or what

i also have the 3000mah packs from batteryspace, and i highly reccomend the charger they have. it charges at 2000mah and trickles at 50mah untill topped off and then has auto shutoff. automatic voltage detection for any of the different rc packs. at 30 bucks, it is a steal

blu666z · « **Reply #4 on:** January 31, 2004, 01:56:08 AM »

Cool, I'll go track it down. +T

-Kevin

caymanreview · « **Reply #5 on:** January 31, 2004, 02:02:19 AM »

i originally used the rat shack 5/7 hour charger, but at 280mah, i had to run the charger a few times to fully charge a dead pack

so when i ordered my 2nd and 3rd 3000mah packs i just bought the combo with the smart charger. now each pack is charged in 1.5hrs instead of a whole day!

good for multi day runs or festivals imho

+T right back at ya!

blu666z · « **Reply #6 on:** January 31, 2004, 02:07:48 AM »

This the one?

http://www.batteryspace.com/product.asp?3=353

Full charge in 90mins would be great! Doesn't require as much planning to get enough charge in.

-Kevin

caymanreview · « **Reply #7 on:** January 31, 2004, 02:10:18 AM »

yep. its great. and a solid little thing too, i figured from the pictures it would a cheapo little thing, but its not!

with me having 3- 3000mah packs, i could be fully charged and back in action in no time, or at festivals, always have a pack charging on an inverter in the car, and never be without juice!

for 30 bucks it is well worth it! buy it, you wont be dissapointed!

caymanreview · « **Reply #8 on:** January 31, 2004, 02:11:13 AM »

and right now if you spend >50 bucks you get a nice little set of binoculors! added bonus!

blu666z · « **Reply #9 on:** January 31, 2004, 02:24:57 AM »

The only feature I wish it had was a discharge option.

-Kevin

caymanreview · « **Reply #10 on:** January 31, 2004, 02:31:48 AM »

i second that, i looked around and couldnt find any with that option. i just did a cycle or two at home with myy gear, and everything was cool. would be way easier to have a charger that would do it though...

leegeddy · « **Reply #11 on:** January 31, 2004, 02:35:17 AM »

Quote from: blu666z on January 31, 2004, 01:11:59 AM

Am I way off base here?

UA-5 draws 500mah w/ phantom power on.

Charger rate is 280mah.

So would I charge it almost 2hours(500/280) for every hour I intend to use it or longer?

-Kevin

kevin;

not quite the way you should see things....

you need to keep things separated: 1. charge calculations and 2. discharge calculations (UA-5 consumption).

first, your UA-5 does not draw 500mAH. mAH is a measure of "capacity". you probably meant that it draws "500mA" per your manual, etc.

depending on what type of battery, capacity of battery and the environment, your charge curve and discharge curve my well be different.

you can always use ballpark figures, but i would calculate how long it would fully charge your battery based on your charger/battery combo. then, figure out how long the fully charged battery will power your load source (UA-5). keeping one calculation separated from the other.

equating your charger's output capacity to your UA-5's current draw is totally incorrect.

hope this helps,
marc

2speedy · « **Reply #12 on:** January 31, 2004, 03:18:14 AM »

blu666z · « **Reply #13 on:** January 31, 2004, 03:34:21 AM »

Not trying to argue, just want to understand. If I know how much power my UA-5 will draw in one hour, why can't I divide that by the rate of charge to the battery to determine how long I need to charge the battery for each hour I intend to use it?

-Kevin

blu666z · « **Reply #14 on:** January 31, 2004, 03:36:41 AM »

+Ts all around BTW

2speedy · « **Reply #15 on:** January 31, 2004, 03:38:27 AM »

Quote from: blu666z on January 31, 2004, 03:34:21 AM

Not trying to argue, just want to understand. If I know how much power my UA-5 will draw in one hour, why can't I divide that by the rate of charge to the battery to determine how long I need to charge the battery for each hour I intend to use it?

-Kevin

thats what i was thinking. if that ua5 is using 500mah per hour, what is the difference in the mah the charger puts back into the battery?

blu666z · « **Reply #16 on:** January 31, 2004, 03:53:50 AM »

Not sure what you're asking.

-Kevin

2speedy · « **Reply #17 on:** January 31, 2004, 03:56:43 AM »

if the ua5 is drawing 500mah from the pack. and your charger charges at 280. why wouldnt those numbers be feasible to compare when doing the math for charging?

blu666z · « **Reply #18 on:** January 31, 2004, 03:58:28 AM »

My bad...I thought you were the guy who said I was doing it wrong....its late.

-Kevin

leegeddy · « **Reply #19 on:** January 31, 2004, 04:10:11 AM »

>.Not trying to argue, just want to understand.

no argument here either, just trying to explain few things.

first, let's make an assumption that the UA-5 under normal operating conditions has a current consumption of 500mA.

>>If I know how much power my UA-5 will draw in one hour,

this is incorrect. your UA-5 continuously draws 500mA, whether you operate for 1minute or 10hours. a current consumption is not a rate.

>>why can't I divide that by the rate of charge to the battery to determine how long I need to charge the battery for each hour I intend to use it?

1. you're not charging your UA-5. you're charging your battery to power your UA-5. 2 totally independent and different operations.

2/ because your battery's "mAH" rating is based on a full charge. if you want to partially charge your battery, it will affect your voltage. it's quite difficult to know how much a partially charged battery will supply the needed current an keep the voltage up.

let's take a look at this example based on your scenario:

you want to operate your UA-5 for 1hr.

calculation: 500mA X 1 hr = 500mAH

your charger's output: 280mA. divide the 500mAH by 280mA = 1.78hrs.

so, if you take your fully discharged SLA and charge it for 1.78 hours and hope that it will operate your UA-5 for 1 hr.

can you see where the logic fails to make sense? your battery's capacity is missing in the scenario. depending on the capacity of your battery, you'd have no idea whether you'll have enough voltage to operate the UA-5.

marc

2speedy · « **Reply #20 on:** January 31, 2004, 04:13:29 AM »

nice write up! makes much more sense now

blu666z · « **Reply #21 on:** January 31, 2004, 06:29:31 PM »

Didn't think about voltage differences depending on charge. I understand now. Thanks.

-Kevin

Ed. · « **Reply #22 on:** February 02, 2004, 05:05:28 AM »

http://www.batteryspace.com/product.asp?0=278&1=280&3=209 <-- i just got that...how long should i charge that battery with that charger to get the battery to full charge...all this battery stuff is confusing.

teamakg · « **Reply #23 on:** February 17, 2004, 11:41:55 AM »

Quote from: SpeshulEd on February 02, 2004, 05:05:28 AM

http://www.batteryspace.com/product.asp?0=278&1=280&3=209 <-- i just got that...how long should i charge that battery with that charger to get the battery to full charge...all this battery stuff is confusing.

i've got the exact same battery setup. basically i charge the battery 2 hours for every 1 hour of use. have yet to have a power problem with it yet.

caymanreview · « **Reply #24 on:** February 17, 2004, 06:20:05 PM »

do yourself a huge favor and get this

http://www.batteryspace.com/product.asp?0=208&1=337&3=353

it makes life so much easier. i have 3- 3000mah packs i use, and this thing is by far the best 30 bucks ive ever spent!

charges at 2000mah and then tricles at 50 to top off
auto voltage detection
auto shut off when the battery is charged

what more could you ask for (besides a dishcharge cycle)

Dustin

Ed. · « **Reply #25 on:** February 18, 2004, 12:49:04 AM »

speaking of discharge....

how often should i drain my battery down to nothing? or should i do this at all?

sexymexi · « **Reply #26 on:** February 18, 2004, 01:06:29 AM »

Quote from: leegeddy on January 31, 2004, 02:35:17 AM

Quote from: blu666z on January 31, 2004, 01:11:59 AM
Am I way off base here?

UA-5 draws 500mah w/ phantom power on.

Charger rate is 280mah.

So would I charge it almost 2hours(500/280) for every hour I intend to use it or longer?

-Kevin

kevin;

not quite the way you should see things....

you need to keep things separated: 1. charge calculations and 2. discharge calculations (UA-5 consumption).

first, your UA-5 does not draw 500mAH. mAH is a measure of "capacity". you probably meant that it draws "500mA" per your manual, etc.

depending on what type of battery, capacity of battery and the environment, your charge curve and discharge curve my well be different.

but wouldn't you have to take into account how much your mics take for power, like my 391's take i think 2ma, but u look at the earthworks, and they draw 10ma. i think from talking to becky, she has had problems with her batt's draining so fast. but from the math, would not different mics make your battery time different, the difference from 2 to 10 is huge. much much more power being used. oh well, i just plan on not having anymore stupid battery problems.. peace.

leegeddy · « **Reply #27 on:** February 18, 2004, 01:09:24 AM »

Quote from: SpeshulEd on February 18, 2004, 12:49:04 AM

speaking of discharge....

how often should i drain my battery down to nothing? or should i do this at all?

it doesn't matter with SLA. for NiMH, full discharge is recommended. for NiCd, it's advised that you always run a full discharge cycle to avoid "memory effect".

marc

BCostigan · « **Reply #28 on:** February 18, 2004, 07:31:15 AM »

Quote from: leegeddy on February 18, 2004, 01:09:24 AM

Quote from: SpeshulEd on February 18, 2004, 12:49:04 AM
speaking of discharge....

how often should i drain my battery down to nothing? or should i do this at all?

it doesn't matter with SLA. for NiMH, full discharge is recommended. for NiCd, it's advised that you always run a full discharge cycle to avoid "memory effect".

marc

Fully draining an SLA is NOT good for it. Fully discharging an SLA a few times will probably not be noticed but it does effect the capacity of the battery and over time will deminish its life/charge.

caymanreview · « **Reply #29 on:** February 18, 2004, 07:48:37 AM »

batteryspace.com claims thier nimh packs dont have a memory, is this just a lie?

Brian Skalinder · « **Reply #30 on:** February 18, 2004, 08:14:43 AM »

Quote from: caymanreview on February 18, 2004, 07:48:37 AM

batteryspace.com claims thier nimh packs dont have a memory, is this just a lie?

I haven't noticed any serious memory effect with my NiMH rechargables like I used to with old NiCDs. However, I have noticed my NiMH batts do benefit from an occasional full cycle: full charge/full discharge/full charge.

caymanreview · « **Reply #31 on:** February 18, 2004, 08:18:08 AM »

thats exactly what i do, a full cycle every once in awhile if they have had a few partial discharges/recharges

but i dont really have any history with any nicd batterys to know a difference