What am I missing? I have been involved in R/C for over 20 yrs., and thus have been charging batteries for over 20 years. I have chargers, cyclers, timers, meters and charts. What is so special about LiPo chargers? Do they sense when charging is done? Are they fast/slow/pulse or auto-trickle? I shouldn't need ANOTHER specialized charger, should I???
Yes, you absolutely, without a doubt, need a special charger for li-poly or li-ion cells. The charger needs to be a very controlled constant voltage charger instead of the constant current charges you now own.
remove my-wife to reply :-)
The chargers you have been using to date are constant current devices, and if fast charge they have some means to detect the end of charger, usually when the voltage peaks and starts to go down. Lithium is more like lead acid. It requires a constant potential charger with current limit, but the voltages are different than lead acid so you would need a charger designed for the specific voltages encountered with lithium packs.
-- Red S. Red's R/C Battery Clinic
Yes.
LIPOLY need a charging regime that is closer to lead acid than Nicads or NiMh.
What is required is something that severely limits currents to a one hour rate, or even longer, and will detect the rising pack voltage and gradually reduce the current as the pack approaches full charge - 4.2v per cell I think, but check elsewhere first.
Astro 109 is about the best at the moment, if you can source one. That autodetects the clee count leaving you only to set up charge current, and checks teh pack voltage off charge periodically to assess hwo 'full' it is, and stops completely once its near enough full.
Overcharging is very dangerous, and will result in explosions and fires.
when you overcharge Lithium cells they BURN there is NO peak to sense to shut down, and the overcharge voltage is VERY close to the full charge voltage.
There are good reliable chargers available pretty cheap for the one and two cell packs, and a good one to four Lithium charger won't set you back over $100 US
the batteries alone will cost more than a decent charger for the low cell count packs
So unless you are now using bacon fat and hamburger grease from the kitchen to mix your own fuel, you are probably NOT so tight that you would try to save a few bucks at the risk of burning down your house / shop / hanger
The short answer is, you don't NEED a special charger, but unless you have way more time to babysit your charging batteries than most of us do, It's a good idea to go for the extra investment and spend the time while the batteries are on charge doing more productive things.
YMMV M>What am I missing? I have been involved in R/C for over 20 yrs., and thus
Joe, Can you spell 'KA-BOOM?'
Here's a good article on the Horizon Hobby Site.
LITHIUM BATTERY CHARGER WITH VOLTAGE & CURRENT CONTROL Feature By George Steiner
Auto detection of cell count can be a crap shoot. The MAHA C777 Plus charger was recalled because of this. The charger senses a voltage of 8.2 - do you have 2 cells nearly fully charged or 3 cells discharged? I note that the Orbit Micro Laden and Triton both allow you to verify the cell count before initiating charge. Chargers that claim to do it automatically are suspect. Lithium Specific chargers like the Kokam and Apache require that you select the number of cells, they will however do just what you tell them to. If you give them the wrong cell count you can end up with a silver sausage (or worse).
-- Red S. Red's R/C Battery Clinic
It can be. Astro seem to have got it pretty near right. The worst it does is overdetect - i.e. err on the safe side. If the partially charged pack is recomnnected it will the sense correctly and do the full charge.
Well, the feedback from the field so far seems pretty good. Never underestimated a pack count, and over estimates always recovered once the pack was partially charged.
You have to balance the possibility of inadvertantly connecting a charger set of for - say - 5 series to a 3 series pack, against the (IMHO ) smaller possibility that the Astro will under estimate the cell count.
There is a lot of software in it, and obviously the possibility of bugs exist. Neverteless I think it is teh best of te bunch, and probably most suitable for users nopt wanting to fiddle with too many buttons.
Indeed. that why the Astro wins IMHO. It won't overcahrge a decently balanced and not totally discharged pack. If a pack gets seriously out of balance, or a cell shorts, then pretty much any charger that does not individually monitor each cell is a potential sausage maker and suicide bomb generator :-)
Self balancing electronics for packs is just beginning to happen. It should help that. Those, plus teh Astro, are about as good as it gets I would say.
No doubt, next year it will be better...:-)
I know that the discussion here concerns Li Po batteries however I do not believe that all auto detection charging is a crapshoot. I am currently using two Hughes RC four station chargers on both NiCad and NimH packs ranging from 1100 to 4000 Mah. These are slope detection chargers an to date I have never found any evidence of overheating. As for the LiPo,s I am using an Apache Smart Charge 1500. It requires jumpers to be changed to select the number of cells and the cell capacity. While it seems to work well I would not trust it or any other LiPo charger to charge completely un attended while inside my house or vehicle.
IIRC my college chemistry, lithium is as reactive as sodium, and I DO remember the sparks and small flames that jump off a small chunk (~1/8" or 3mm) of sodium that is tossed into a lab sink with enough water to cover the bottom.
So, overcharge any lithium chemistry battery and you rupture it from overtemp..... there's moisture in the air...... voila' .... fire and/or explosion ! ! !
David
Please do not perpetuate the myth that Lithium batteries contain lithium metal. They don't.
The fire hazard is from the organic compunds used in teh electrolytes and constructium. liuthoum POLYMER./ The polymers burn.
The lithium is present as a compound of some sort.
This is not to say that a hot and nasty fire won't result - it will. But its not a lithium fire.
Actually Kokam has done a REAL stupid thing and added auto cell count to their latest charger. AND, it doesn't work any better than anyone elses auto detection scheme. BUT they still give you the option of setting the voltage for yourself just like the older model chargers.
bob
What model number would this be? The latest is the 402 and that requires that you set the cell number with the jumper.
-- Red S. Red's R/C Battery Clinic
There is the REALLY UGLY part they changed the charger, and did NOT change the designation
It still says LIPO-402 on the front the printing has been rearranged on the case, AND they added an extra pair of pins to the voltage selection section
bob
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