Topic: how long to charge a NiMH battery + other q's

[smanky]

Well last night I hit my first - battery-went-dead-on-my-ua5 problem.
And I didnt know it had died, because I had to do merch at the show I went to last night so I just had to set up my rig and let my friend watch over it.

I have a 1700mA NiMH battery and a "4 hour quick charger" that says it outputs 12v DC @ 200mA.  Doesn't that mean that it should take 8 1/2 hours to fully charge a completely drained battery?  I had the battery partially drained and I charged it for a little over two hours, which I figured would give me about 2 1/2 hours of juice on the ua5, but the battery died after an hour.

Also, if you accidentally overcharge the NiMH batteries, will they lose some of their life?

[busknuckle]

do you have the owners manual for your charger? It should say.

[smanky]

I don't  

[rabhan]

pagin skalinder, paging skalinder!...............

[Brian Skalinder]

Well last night I hit my first - battery-went-dead-on-my-ua5 problem.
And I didnt know it had died, because I had to do merch at the show I went to last night so I just had to set up my rig and let my friend watch over it.

I have a 1700mA NiMH battery and a "4 hour quick charger" that says it outputs 12v DC @ 200mA.  Doesn't that mean that it should take 8 1/2 hours to fully charge a completely drained battery?  I had the battery partially drained and I charged it for a little over two hours, which I figured would give me about 2 1/2 hours of juice on the ua5, but the battery died after an hour.

Also, if you accidentally overcharge the NiMH batteries, will they lose some of their life?

If you charged it at 200ma for 2 hours, you've stored up around 400ma capacity.  However, the UA5 draws 450ma with phantom power on, so...yeah, that 2 hour charge would only get you around an hour of actual usage with the UA5.

Your math is right on the 8-1/2 hr charge at 200ma to power up the 1700mah battery.  I'm not so sure about overcharging as my NiMH chargers are all float chargers - they switch to trickle when they reach full charge.

[dklein]

yeah - they're not perfectly efficient when charging.  You have to put in about 150% of the capacity.  So 1700 * 1.5 = 2550
You need a good 12 hours with that 200mA charger.  

When they're fully charged, NiMH batteries can also generally handle a current of .05-0.1C (C is the capacity) and just safely release it as heat.  So in the case of your 1700 mAh battery, about 170 mA on the high end.  If you have access to a meter, it might be worth measuring the current output on the charger (make the meter part of the path with the battery charging).

The charger you have would definitely not qualify as a fast charger.  A fast charger would run anywhere from 0.3 to 1.0 C (so in your case between 500 and 1700mA).  Fast charging can slightly decrease the overall life of the battery (as in number of charges) but isn't anything to worry about.  BUT, if not terminated at the right time - the battery can become damaged.  You will feel the battery start to warm up when it's at capacity and is receiving too much current.  In fact, the good chargers stop based on measuring temperature change.

So...as long as you're not in a rush, your charger is fine and you don't have to worry too much about the time.  I wouldn't leave it permanently on but you won't do too much damage if you forget about it overnight.  As far as when to stop - 12 hours or when the battery starts to warm a bit.

[smanky]

Thanks for all the tips.  I'm still clueless on how to do t+'s (read the faq, still in the dark).  I thought the battery I was using was 1/2 gone, so I thought I'd have enough juice to last me if I just charged it up a little but I guess I miscalculated and I had used more than I thought :/

Anyone have the link to the 3000mAH NiMH battery, or a little bit faster trickle charger?  I just drained both of my batteries completely by just leaving the UA5 on so I'll give em both a complete charge of around 12 hours

[teamakg]

Thanks for all the tips.  I'm still clueless on how to do t+'s (read the faq, still in the dark).  I thought the battery I was using was 1/2 gone, so I thought I'd have enough juice to last me if I just charged it up a little but I guess I miscalculated and I had used more than I thought :/

Anyone have the link to the 3000mAH NiMH battery, or a little bit faster trickle charger?  I just drained both of my batteries completely by just leaving the UA5 on so I'll give em both a complete charge of around 12 hours

to give out +T's you need to have 50 posts.

here's the link to the 3000 battery
http://www.batteryspace.com/product.asp?3=54

i've got it and love it.  

[smanky]

nice, thanks.  Does batteryspace have faster chargers as well?

slowly making my way up to the 50 post mark...