Ei + ibec + a123 = ?????
 

OK this is not a thread about whether the information I am getting is correct or not. It is whether the risk I am thinking about taking is high, medium, or low, knowing that what is suggested might happen. I wasn't sure exactly where to put this because it involves engine, batteries, optical kill switch, so if it should move, I am ok with that.

A lot of you probably know I am working on a Hangar 9 Pulse 125 XT. I am at the point where I am making my choice for the electronics. The choice comes down to either a single battery system with an Optical Kill Switch (IBEC) or the suggestion that I should consider using a dual battery system in parallel. The cost of the dual system (including switches for internal charging and charging cable) is $152 for two 1100 MAH A123 batteries. Or right at $105 for a single 2500 MAH A123.

The indication has been that a short in the EI system could lead to a nice hole in the ground where the plane goes in. With only 1 battery this has been deemed as a possibility. I don't have any evidence to say that is wrong, and I believe what I am being told.

The issue is this: Is my risk using the EI + IBEC + 2500 MAH single battery scenario that big of a risk? How often or likely am I to have a short that would mean a straight trip to the ground? Or is the risk significant enough to warrant the additional cost of around $47? The engine is a DLE20 and I have a Hitec X4 DC only charger, so I have what I need to charge.

A short will likely cause a crash regardless if you are running dual batteries or not. A dual battery setup gives you redundancy from a bad cell or bad switch, and it lets you have enough battery capacity and amp capacity for a high drain electrical system. The redundancy is always a plus, but thousands of planes fly every day all around the world with only one battery and switch with no problems. The capacity and amps issue isn't a concern for a plane that size at all.
On a side note, the prices you are quoting sound pretty high. I got that same battery from www.hangtimes.com and am using the ED high amp switch they sell on a 50cc plane. I didn't spend nearly as much as you're talking about. The one thing I did do different though is I got a 4.8v NiCd for the ignition.

jester...the cost includes: (2) 1100 MAH A123 Batteries / 2 Switches with Charge port / a combined charging/balancing cable. So the cost may be the difference between the NICAD and the 123. I say that because that is what the cost is at hangtimes which is where the numbers come from.

$79.95 for an 1100mah A123, ultra switch, and combo charger cable plus
$59.95 for the second 1100mah A123
is $139.95 plus shipping

So I am not sure where the less cost comes from unless it is the battery. Although the cost seems high, that is what is on their site and I am willing to pay it if the extra battery is going to buy me that much more security. I too have flown for years with only 1 battery, but have not dealt with electronic ignition.

I have been running single Li-Ion with a Tech-Aero Ultra IBEC in all my planes for near four years now. I don't do it this way because of cost I do it for simplicity. In these four years I have not had one single glitch, not to say there can't be one. As stated by Jester a short can and will kill the aircraft irregardless of a single or dual batteries. One could use a battery redundant system to aid in minimizing such a scenario but that comes with it's own risk. There is the risk no matter how we build, or power, our planes. So in my opinion just KISS and go with one battery with the Ultra and enjoy. The only caution I will advise on would be to measure the mah's through recharging after each flight for the first couple to see what your system will use.

I would like to add that with the redundancy built into the Ultra even a short is unlikely to reach the Rx. There are a couple videos on You Tube where guys are intentionally shorting the Ultra and nothing reaches the Rx.
So in short to answer the question, the risk is virtually non existent.

Thanks Ace....The Tech Aero IBEC is exactly what I have and will be using. I too am not that concerned about the cost, just the reliability, and the kiss principle. I am electronically challenged to begin with. So the more complex the electrical is, the more my eyes glaze over. Oh I keep reading and learning, but in this regard, electrical components are my weak point.