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DIY NV. What Ah draw you got ?

Discussion in 'Night Vision Optics and Illumination' started by 32:1, Mar 23, 2014.

  1. 32:1

    32:1 Yea, I like it

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    Hi guys

    My first nv build is great apart from a power problem Ive found now Im in the feild so to speak !

    My first batt pack of 2300mAh lasted around 15/20mins, then I fitted a new pack of 2600mAh thinking the first pack was evilbay trash, this new pack delivered 25/30 mins ???

    On checking the draw of my build I have a steady 0.4Ah so by my math, had a few hours from either pack.

    Whats the expected draw from an E700 and screen ? Thats all Im running, so is 0.4 high, low or average, Ive also ordered a battery from livewire.

    Cheers

    Chris
     
  2. Chippy1988

    Chippy1988 Busy Member

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    I couldn't tell you mate but my blue battery is supposed to be 9800mah and I run a board cam with 5" screen. I have yet to run it flat while out. I am usually out for about 3 hours at a time, I go out twice and then charge at the most.

    hth

    James
     
  3. terry1001

    terry1001 Major Poster

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    Your current draw is about right. I suggest you fully charge your batteries and then let them stand for an hour or so then check the voltage without a load, plug in your equipment and check the voltage (on the spare connector) with it under load. Let it run flat checking how long it lasts and then check the voltage again. Some of the packs may have protection circuits which cut out too soon which could cause the problem.
    Repeat with the other pack, if you're not getting somewhere near what you should in runtime then contact the person you bought them from and complain. If you don't get a satisfactory response then take it up with ebay/paypal etc but do it asap.
    I wouldn't expect to get all the capacity from a battery pack but you should get half which would be 3 hours or so on the smaller one and a half hour more with the larger.
    I don't know which batteries you have but most of them should be turned on when charging as the switch isolates both connectors, quite a few people have reported dud batteries only to find that they haven't actually been charging them at all! There are usually no instructions with them and the lights on the charger don't really tell you what's going on.
     
  4. 32:1

    32:1 Yea, I like it

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    Not used the blue ones, first batts where marked GTL and second VP racing....

    So 0.4Ah sounds OK

    Ive since tested the GTL 2300 batt and with a 0.5Ah draw they lasted just 12mins ?
     
  5. audiguypaul

    audiguypaul Donator

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    Having not been too impressed with my blue battery which packed up after a few months ive gone for 3 x Panasonic 18650's and a 'series' case for them. have a look at these bay numbers 181311071822 and 281199951833, ive charged them fully and am currently seeing how long they will run the nv with continious use.

    atb Paul
     
    Last edited: Mar 23, 2014
  6. terry1001

    terry1001 Major Poster

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    Unfortunately the capacity claims for nearly every battery on ebay/amazon etc are grossly overestimated, if you expect about half of what they claim you'll probably be in the ball park. I tend to buy only from UK suppliers now and if anything were to fall short of claimed capacity by much I would be looking for a full refund or would refer to Trading Standards. So far I've been reasonably satisfied.
    You can easily make up your own packs using rechargeable cells such as AA, 18650, 14500 etc, the battery holders are readily available but you should remove them and charge the cells individually to be on the safe side.
    I have suggested using a cordless drill as the host for a hand held spotter and these could be charged using the ordinary drill charger, NiCads are more forgiving than the Lithium types. It is also possible to use an electronis voltage regulator so you could, for example, use 4x18650 cells (nominal 14.8 volts) and use that to provide a regulated 12 volts for camera and monitor. You may also find that the equipment will work quite well at lower voltages so that is worth checking if you do decide to make up your own pack.
     
  7. Tubs

    Tubs Active Member

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  8. audiguypaul

    audiguypaul Donator

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    Well so far my 3 x Panasonic 18650's 3400mah have been running my screen and camera for over 7hrs, that will do for me.
     
  9. Alex.mc

    Alex.mc Busy Member

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    After reluctantly buying an alleged 1800ma cased, switched Li-on pack...... and discovering it was as I expected... a pile of pooh! I went back to what I originally planned and bought a pair of these RC Model flight packs. http://www.ebay.co.uk/itm/271408285675?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
    I have a quite sophosticated charger and am able to measure charged and discharged capaities. These packs are reliably charging 2100-2200ma every time!

    My current draw is low, about 250ma so I happily get 8 hours if I want! You will need to do some soldering, and be aware that these packs.... although as safe as any other lipo, and well made by a well known manufacturer in RC circles, are very energy dense! And poor charging and shorts etc. will get you in trouble. Having said all that, some of the poor offerings on Ebay are undoubtably much more dangerous as their manufacturing standards are so bad!

    The claims for capacity for some of these packs are truly incredible.... or should that be incredulous? These unknown, untraceable origin packs are making claims that the bleeding edge big battery companies can't hope to achieve in anything like the near future! I've got a better chance of winning the lottery than achieving their claims!
     
  10. audiguypaul

    audiguypaul Donator

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    Update - over 12hrs run time.
     
  11. Alex.mc

    Alex.mc Busy Member

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    Small update, and not wishing to hijack the thread.....

    I disassembled the pack yesterday, and lo and behold... it contained 3 "Old" 18650's with some crappy wiring and soldering. The cells still had remnants of the old connecting tags left on them, and the brand stickers were manky and scraped in places! I looked up the brand and they were Laptop battery suppliers, so these were reclaimed from dead or old packs! They had possibly been Panasonic cells, but were certainly only rated at 1350ma on the Brand's own website!
    Despite trashing any warranty, I've written and sent photos to the vendor on the basis that the packs cannot be described as "Brand new", I doubt I'll get far but we shall see?
     
  12. stoogey

    stoogey Engaging Member

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    side info to thicken the plot...

    the capacity is whats in in, but if your drawing 400mah at the end of the capacity its drawig a higher and higher percntage of what its got, ot to word it from a different angle that 400mah is 300..200..untill the devise just fails.

    but....it depends what regulating systems in the device, pure analog burn off regs you get the dwindling effect, anything pulse width modulated or some cuson of it you get a low power draw at hi volts and a hi power at low voltage (near the dead end of the charge)..its worked in wat's ish..12v in to a 4volt out, the 'ideal' 8 volt drop is converted to amps for want of a metofore, so its draws less amps and uses extra unused volts to sort of make up the amps current, so a 0.4 amp draw would probly tale 150mah at the beging untill the volts lower at the cell enough to make use more amps because the volts are too low (like steppping up takes ,ore than the device would draw, steppimg down taking less amps).
    dont forget a lot of this stuff is rworked on the 'ideal' figures, the word 'ideal' in this case means on paper and things like 'we dont know yet so equate it to zero maths' untill ou get some figures that add up, in real life theres heat loss and efficiency losses etc to add to it theat enable you to get co,poinent values that will work to some where near what you want...ish.

    now to thw point, o.4amp draw om 2600mah batteries, the 'ideal math' sais 2.6 divided by 0.4 = 6 hours(rounded), from that i'd say any thing over 4 hours easy.(because of losses and the dwindling capacity thing).


    regaurding your ir light power suply, best keep it seperate, as a lot of torch drivers are pwm, they generate stray signal like a transmitter that picks up on the screen as floating line or noise etc etc...its bleeds over stuff in other parts the system./ fluctuates stuff that really dont want it

    the dimmers are the worste,m but best for showing where that floaty line is comeimng from, as you dim up and down the lines tune up and down, sometimes nearly stopping still at the same dim point lol.
    second on this list is the draw on the battery 'sags' the more you draw on that battery pack the larger the sag, so adding an amp driver to the screen and cam can lag the voltage way to low and fail the whole system.(particularly as you go brighter and brightest), if you adjust the regs to acount to the lag at hi on the ir illuminator, it may well pop or overload the screen/cam if you dim the light because the lag loss isnt there as much making the volts go up, so current flows much ore easily, in light bulb terms, you have three in the on state, you turn two off and the third blows instantly type of thing.
     
    Last edited: Apr 4, 2014
  13. Alex.mc

    Alex.mc Busy Member

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    The above is a good point. Stated capacity (assuming they are being honest about it and not lieing through their teeth!) will be at one particular current.... often a low one! That's where the best figures are devived from.

    From my model flying days, it was well known that you could not expect to see the stated capacity delivered in your usage.... as your usage for flight motors was often way further up the current scale. So, if a pack was rated at 2000ma...... becauyse tyou were drawing maybe 10 amps rather than the 1 amp it had been tested for capcity at... you would probably only see about 1500ma out of that pack at best.

    As electric flight became more popular, and sales better, more appropriate packs were offered and most pilots would indeed see the sateted capcity delivered in their usage situation.
    Top line packs now will deliver 50c continuous, that is 50 times their capacity in current, and up to 100c burst i.e. for a short period of a few seconds.
     

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