Topic: Battery Charging Math

[2speedy]

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]

Not sure what you're asking.

-Kevin

[2speedy]

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]

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

-Kevin

[leegeddy]

>.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]

nice write up! makes much more sense now

[blu666z]

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

-Kevin

[Ed.]

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]

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]

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.]

speaking of discharge....

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

[sexymexi]

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]

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]

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]

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