BEC and Power Switch?

[GizmoB73]

I finally put my Twister Storm 3D together this weekend. However I found that the Deans connector for the battery is quite tricky to get apart. Also that once the canopy is fitted, it would take quite a while to take the canopy off and then disconnect the battery.

I am thinking of a few mods and wondered what opinions you might be able to give.

1. I am thinking of fitting a switch for the battery that is accessible with the canopy on so that I can disconnect the power more quickly. Obviously it will need to be able to handle a lot of current...

2. I would like to be able to monitor the LiPo level on-board more easily. Can anyone recommend something for this? Is it worth fitting something permanently on-board for this? Weight etc?

3. I am a little nervous of what will happen of the ESC gets fried. What are the recommendations regarding a BEC or rx batt on such a small heli?

Thanks

Gary.

[trebor27]

I would not put a switch in the main power circuit... The switch will have to be quite beefy to not cause voltage drop across it when the battery is under full load.

The deans get easier to plug and un-plug over time.... My recommendation woudl be to keep ti as it is mate...

Rob

[GizmoB73]

I would not put a switch in the main power circuit... The switch will have to be quite beefy to not cause voltage drop across it when the battery is under full load.

The deans get easier to plug and un-plug over time.... My recommendation woudl be to keep ti as it is mate...

Rob

Thank Rob,

Any views on separate BEC or batt versus the in the ESC? Do you use any on board voltage level checker?

[trebor27]

Persoanlly I use the timer method of flying.. I started out flying for 5 minutes.. Then when recharging check to see how much juice the batt took... (Charger tells me total Ah put back in)... Then I slowly increased my flight time until I was happy I was getting a good trade off fo flight time vs. dischard level of the batt. (I have a JR PCM9X 2, so I use the build in countdown timer to time my 8 minute flights)

I just use the build in bec, that is build into my ESC.... If the ESC fails I doubt my autorotation skills would allow me to save the bird anyway... Personnaly I wouldn't put separate RX batt's ont eh heli because there really isn't a huge point... If your paranoid get an external BEC? Powered off of the Main battery pack, but you will have to isolated the ESC's built in BEC so that your TWO BEC's aren't "fighting" each other.

Rob

PS I use a CellPro 4s charger.. it both gives an "estimate" of "fuel" level that seems pretty damn accurate when compared to total AH put back in... So you can see at a glance what level your battery pack got down too... ou need a margin for error though as teh battery pack might have a slightly higher cell voltage when unloaded, whe compared to flat out in yoru heli!

PPS. I too am a "beginner" but this is just what I do and I can't see any major failings in my logic/method to be honest.

[Sesame]

When I started with leccys I got all the lipo alarms, now ive been doing it a little while i'm convinced(it takes time to sink in) that timing is the best way of judging the batterys endurance, always erring on the side of caution.

[Cobham]

Switch - it would need to handle 20-30 amps so it would end up bigger than the heli! Dont use one.
Deans - use Eflite connectors they take over 60amps and I think are far easier to fit and pull apart.
Battery monitor - yes you can get Lipo monitors with three LED's that you can attach to the side of the heli. But timing is best.
BEC - not needed on a small heli - the ESC BEC should be fine as long as you dont run the battery down too low. Aim for 60-70% use each time.
Hope that helps

[trebor27]

Aim for 60-70% use each time.

I usually run to aobut 90% useage in 8 mins!

[Sesame]

I usually run to aobut 90% useage in 8 mins!

Then Ideally you should be running for 6.30 - 7 mins tops.

with the numbers you quoted 7.11mins will give you the 80% but for a margin of safety reduce this.

I run my 450 on 2100's for 6.30 I could probably get 8 mins but im looking at never putting more than 1600mah back into the pack.

[GizmoB73]

Thanks all, I guess I am probably being a bit cautious but I will take your advice and stick to the timed method.

As my charger doesn't have any indication of the battery status as it is charging, it sounds like I need to use something to test the batt. I have seen a few voltage testers like the one below, but do these really give much of an indication? I thought that the voltage curve on a lipo was pretty flat?

http://www.brchobbies.co.uk/?page=shop&item=426

[GizmoB73]

I am also wondering whether those little testers give a loaded reading? Do LiPo voltages change much under load?

[Cobham]

You are right, voltage testers wont tell you how much battery you have used. You need a charger that shows you how many mA's its put back into the battery so you can work out the percent used. Bantam 6 is a good one - takes up to 6 cells lipos - but its quite expensive at around £100.

[Sao]

And with the FMA Cellpro 10 about to come out at £99 you'd be mad to get a lesser charger

[GizmoB73]

You are right, voltage testers wont tell you how much battery you have used. You need a charger that shows you how many mA's its put back into the battery so you can work out the percent used. Bantam 6 is a good one - takes up to 6 cells lipos - but its quite expensive at around £100.

I already have a charger with built-in balancer so all i was really hoping for was a cheaper add-on tool. £100 quid on a charger is a bit steep for me at this stage when I already have an adequate charger/balancer.

Do you think it is worth getting one of the voltage testers just to see the approximate state of the batt after a flight?

[Sao]

No, it'd be a complete waste of time IMHO, the only way you know is by checking how many MAH's go back into the pack after a short flight.
Voltage is no true indicator of capactiy and the Voltage off the heli will be higher than when it's under load.

[Smoothound]

As a rule of thumb I find most of my packs seem to be around 80% discharged if the resting voltage is around 3.7-3.8v around 5 mins after a flight but it's not a good way of checking really