ehong33234 wrote:
Wow, Mr. Buff, thank you for chiming in on my question with your wealth of knowledge. As you can probably tell, I really don't know much about batteries and the specs can be wrong of course. The brand of battery that I have are Thunder Power and Enerland. Here is a spec sheet that Thunder Power provides on their batteries. http://thunderpowerrc.com/PDF/ThunderPowerRC-Pricing.pdf
I wouldn't be surprised if companies are a bit generous with their battery specs.
On a side note, I just ordered my first pair of Alien Bees strobes with some accessories and can't wait for them to get in. I have heard so many great things about you and your products.
Thanks so much for the spec sheet. I'm going to analyze the data and comment further. The info given here goes a long way to explaining these packs and the stated performance, and brings it (barely) into the realm of scientific possibility. Your first info implied 3 or 4 cells in series and was simply not believable. However, the data sheet indicate 4 series by 4 parallel so it begins to look possible.
The missing spec is the all important internal resistance, which has a profound effect on usability with inverters. (I'll explain when I study more.) Also, the discharge rate IE 2C, 20C has a big effect on the number of charge/discharge cycles, heating, cutoff voltage and battery life.
I feel better about these packs now that I have more info.
I will say model TP4350-4SPL2 below is about half the size and weight and watt hour capacity as our Mini battery at nearly twice the price.
4350mAh 4-Cell/4S 14.8V
4C
20C
40C
17.4A
87A
174A
414
32 x 43 x 136
169.99
134.99
Also, it's important that these packs have onboard PCM boards that regulate and control the charge voltage, charge current and discharge voltage and current of each of the 16 cells individually. Without it there is a big explosion/overheating/cell damage potential. Omitting the PCM board can reduce the internal resistance and thus boost the available current, but usually require a complex multi wire "balancing charger"
Finally, using separate Lithium packs in series/parallel configurations is iffy and dangerous.
It may also be difficult to use 11.8 or 14.8V packs with off the shelf inverters. An 11.8V pack will fall below the shutoff voltage of most 12V inverters well before the battery is exhausted while 14.8V packs will reach 16.8V when fully charged and may exceed the max input voltage of 12V inverters. We have had to address all of this by using custom design of our inverter specs.
I'm not sure if this addresses the issue you referred to but my lipo packs have balancing connectors already built in that I use to hook up to my charger and charge each cell evenly. In regards to the discharge, corndog suggested a digital volt meter LCD to monitor the voltage. The r/c industry also has an alarm feature just in case of this voltage danger: http://www.bphobbies.com/view.asp?id=B1018380&pid=C1436802
I do see where selecting a proper inverter could pose a challenge. I'll look around some more and see what I can come up with.
Assuming PCB's new mini Vagabond ships on time and is everything promised, the idea of a Pelican pack is basically dead. I love mine, but it cost basically as much as PCB's new VML and doesn't have as good a battery or a warranty.
ehong33234 wrote:
Look forward to some more input on this Mr. Buff.
I'm not sure if this addresses the issue you referred to but my lipo packs have balancing connectors already built in that I use to hook up to my charger and charge each cell evenly. In regards to the discharge, corndog suggested a digital volt meter LCD to monitor the voltage. The r/c industry also has an alarm feature just in case of this voltage danger: http://www.bphobbies.com/view.asp?id=B1018380&pid=C1436802
I do see where selecting a proper inverter could pose a challenge. I'll look around some more and see what I can come up with.
This is what I expected. Balancing connectors control the battery charge and overcharge, but are complicated and offer no protection against discharge currents and can lead to exploding batteries.
They don't really explode per se, but they do they smoke/flame pretty quick. I lost nearly a hundred dollars worth of batteries once when I nosed my plane in, it was visually impressive. Had a near miss while soldering a pack too, did a little welding. Many people put them in an ammo box while charging them at home. Anyway, things can happen quickly, take a few simple precautions and they're pretty safe.
Like SLA batteries, they will heat and expand and either flame and burn or, if rigidly encased, explode. I was tempted to use non-discharge controlled Lithiums like this because their lack of output MOSFET current and temperature control lowers total internal resistance and cost. But I was warned by too many quality manufacturers not to go there . . . due to fire and explosion hazard. Instead, I demanded and got large, low resistance MOSFETs and an extremely low overall battery resistance.
By sizing the battery capacity generously to the inverter load current requirements, maximum efficiency is achieved as is maximum battery life and number of pops per charge. The battery remains cool under continuous firing until the battery is exhausted.
But don't attempt running say a 300W inverter from the Vagabond Mini battery . . . the current draw is beyond the battery's controlled maximum current output, so the battery will shut down. When I get ready to do a larger wattage inverter I will probably go up to an 18AH 14.8 or higher lithium (about 4lbs and twice as expensive) and have the capacity equivalent of about a 35AH SLA 30lb battery.
