DIY Battery Box

... At work I charge them with a 4 output variable DC power supply with voltage dialed to 12.75 volts and amperage around 700 to 800 ma.   Because of enclosure size restrictions, I have only worked with the 6800 and 9800 mAh versions of these batteries at work.   I keep a meter on each and pull them when balanced voltage reaches around 12.60 volts.   When pulled from operations,  they are typically drained down to around 10.5 - 11 volts and take around 8 hours to charge back up.

A 12.6V Li-ion battery is composed of 3 cells in series.

Check the links I posted in #67 above.  The charging plot for Li-ion is not linear and shows that capacity trails voltage by quite a lot.  Full charge is attained in about 3 times the time it takes to get to 12.6V.  So to get your batteries to a full charge at 700-800mA maximum current would take about 24 hours.  Two conditions determine when the Li-ion battery is charged, the voltage hits 12.6V AND the charging current drops to 3% of the maximum, and I have been monitoring both parameters manually.  Most "Smart" chargers stop charging when the voltage attains 12.6V AND the charging current drops to 10% of maximum.

I believe I am getting these charge times because of the higher amperage that I am charging them at.  Could you post the specs of the charger you ordered. 

1500mA maximum current, stops charging when battery voltage attains 12.6V AND charging current drops to 10% of maximum.

I am familiar with how these and other similar Li-ion batteries obtain their voltages via combining 3.7 cells.    I can also only post what has provided very good results with several dozen of these battery packs with 14 or so discharge / recharge cycles each at this point.

Are you going with a smart charger as a redundant safety backup should the battery packs PCB fail vs. just a standard 1.5 amp transformer?

I am going to experiment with some cheap1 amp transformers I have .  I have one battery that I have drained down to where it's PCB kicked off at 8,5 V.   I will see how long it takes before the PCB's overcharge protection disconnects. 

I'm going with a smart charger because I need a higher charge current, I am unsure of the electronics in the blue-brick itself, and it was cheap and easy - $18

I received the Li-ion "smart charger" and tested it.  From a charged battery I used it for about 5.5 hours with a draw of about 650mA.

I plotted the battery voltage and charging current over the length of the 6 hour charge.  The voltage and current plotted a graph very similar to the one in the previous links.  The battery started at 11.58V with charging current of 1.17 A.  After 6 hours the voltage was 12.61 with a charging current of 0.119A.  I stopped it then since the charging voltage had reached 10% of the initial value. 

The charger has a dual color LED.  It started red and sometime in 4-5 hour time range it changed to green.  At 5 hours, when green, the voltage was 12.48V and the charging current 0.214A.

For my FF/GPS (650mA draw) it looks like I should charge for about the same amount of time as used on the battery.  YMMV.  Also the charger is behaving properly, so leaving it on longer (within reason) will likely not hurt the battery. 

Here's the link to the "smart charger" I got. 

http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=320879811549

Version 2.0 x 2





If you're wondering about the extra wires  inside, it's so I can still plug in a lead acid battery.

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Wow, Lee, those are really nice. Pack foam inside to keep things in place when in use?

Not really necessary.  The batteries are light, and won't damage anything if they move around a bit.  I put foam in with the lead acid battery because it was so dense I could see it potentially doing damage.  Maybe I'll put wallet, keys and sidearm in there.

Use the foam.  When the wind waves are breaking over the bow and your hull is slapping down into the wave troughs, letting everything bounce/slide around will stress the connectors, pass-through points, and waterproofing. 

  Maybe I'll put wallet, keys and sidearm in there.

I'd advise against that.. may sound strange but you may run a risk of demagnetising any swipe cards you have in the wallet, plus it might affect the chip in your key fob if your car uses one of those types. We've found in our Tallahassee test lab when doing isolation testing, that even the button cell or coin type batteries will produce an Em or RF field while in use that can disrupt things like that.

who woulda thought that just two hearing aid batteries could cause so much trouble?

Am not at all sure if this would be true with LiOns but after what i've seen , wouldnt want to  chance it. 

Last thing I want to deal with is calling for new cards.  Blech.

I hear ya Demonick, but I'm gonna live dangerously!   

Kidding aside, I pulled the cable all the way to the connection, and backed it with a zip tie and copious amounts of Goop.  Should be fine.  The only turbulence it will see is my Huli's.  Maybe I'll add a piece of spare pipe insulation after I re-do my car racks.

What kind of run time are you getting out of one of these puppies with like a lowrance elite ff?


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Take a look at these weatherpack (Packard) connectors... I'm ordering a handfull of these and will have some extras at ORC if anyone wants one....

Erik

^^ Those look nice, what do they run $$

My cost is about $3.50 for a set plus shipping.

The thing is, to do this right, you need the special crimpers tools (which I already have).

Those are what Hobie uses for the Hobie Livewell.  They're nice!