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May 19, 2014, 03:28 PM
A different attitude to RC
extremewing's Avatar
Thread OP
Mini-HowTo

1S LiPo with battery protector


Ok, it's not really bullet proof but pretty much eliminates the risk of catching your plane on fire from overcharging the battery, giving you piece of mind and also eliminating the chances of destroying the battery by leaving the aircraft turned on by mistake.

It will prevent:
- Over charging
- Over discharging
- Short circuit

The battery protector circuit is, in my mind an essential part of any LiPo battery pack and can be found here: http://www.all-battery.com/protectio...mit-32133.aspx (costs less than $1).
UPDATE: The battery protector used in this thread seems to have gone from the site.
Here is a link to others they carry: http://www.all-battery.com/1S_Li-Ion.aspx
Another potential source for the 15mm diameter pcb: http://www.batteryjunction.com/prcimopfor3l.html

The battery in this thread is here: https://www.hobbyking.com/hobbyking/s...und_lipo_.html

Suitable chargers:
SparkFun ($7.95): https://www.sparkfun.com/products/10217
eBay ($1.50 and up): http://www.ebay.com/sch/i.html?_from...rging&_sacat=0

NOTE: The linked protector circuit is specified for Li-ion but is also suitable for LiPo and I have personally used it in this (DLG flying) and other applications where the 1S HK round LiPo was drained completely as well as charged by a "non LiPo" charging source with no problems at all. It really WORKS. Here's how I put them together.

WARNING: You want to make sure there are really good solder joints and no exposed or shorted components since a problem here may cause a BIG problem in your plane!! Work neatly.
Last edited by extremewing; Jun 11, 2015 at 01:36 PM.
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May 19, 2014, 03:55 PM
G_T
G_T
Registered User
I was working with an application which unintentionally built such circuitry into their batteries through an unrecognized supplier revision. There was a situation where the application needed to briefly pull high current. The circuitry associated that with a short, and cut the circuit until the "short" was removed. This resulted in a reset of some processors and erroneous results afterwards, with potential real world consequences. The details are more interesting than I'm making it out to be here but are not a subject for this thread.

Sometimes the life or state of the battery is of lesser importance than the supply of any available voltage and current. Use such circuitry intelligently.

Gerald
May 19, 2014, 04:04 PM
A different attitude to RC
extremewing's Avatar
Thread OP
Gerald, the cutoff in this part is 4A and I have NEVER had it trip out on me - even when drawing close to the trip point with a string of 196 high bright LED's that would draw way more than a DLG.

Having also seen a plane on fire from a wrong charge setting, I feel this addition is important. Not to mention how many stories I have heard of the battery being destroyed from over discharge.
May 19, 2014, 04:34 PM
G_T
G_T
Registered User
If a plane is in the air, over discharge is preferrable to fly away, or impacting a person or person's property. Overcharge prevention I like. Overdischarge though is more iffy. I prefer an alarm for the low voltage end. Battery providing whatever it has while the plane is in the air is mission-critical. Battery surviving is not as critical. Important, yes, but not critical.

Gerald
May 19, 2014, 04:46 PM
A different attitude to RC
extremewing's Avatar
Thread OP
Gerald, if you look at the specs, you will see the over discharge trigger is 2.5V and there is no way any receiver is going to work this low. If you go below 3.5V or so on a 1S you are looking for trouble.

See https://www.rcgroups.com/forums/show...57&postcount=7 (I agree with their numbers)

This device will just prevent the battery being destroyed as far as low voltage goes.
May 19, 2014, 05:07 PM
Blind Hawk
rdjay's Avatar
I've seen Adrian mention these a few times. Ordered a dozen of them to try a couple weeks ago. Installing was really simple, took maybe an extra 10 minutes when wiring the battery. Have only used it a couple times but so far all is good. In the past I've left a plane plugged in a time or two and drained the LIPO completely dead, this should solve that dumb mistake and I like the added security of the over charge protection. All for $.99, probably less than a gram and 10 minutes time.

Thanks Adrian!

RdJay
May 20, 2014, 07:43 AM
ClearView Rocks!
Quacker's Avatar
I invite you to put an ammeter on one of your servos and then stall it with a fresh battery, and read the locked rotor current. Multiply this number by 4 for the 4 servos in your plane. Then test the 4A cutoff current of the battery protection. (As you know, the spec may be pretty far from the truth). If your 4 servo number is well below the actual cutoff, you are good to go. These are easy tests to make. Until you do this, you are flying on speculation.

Then take a look at the battery voltage when the battery is loaded with your 4 servo, locked rotor number. Discharge the battery until it's at 20% or even 10% capacity and apply your 4 servo current. What voltage did the battery dip to? Did it get near the low voltage cutoff voltage that you tested to? You did test this, didn't you? There is margin built into this test since a low voltage will not produce the same current you measured earlier with a fresh battery.
Last edited by Quacker; May 20, 2014 at 07:49 AM.
May 20, 2014, 08:05 AM
Registered User
elkski's Avatar
Its, I am using these on many of my planes. Would you be willing to test a couple if mine? I assume testing won't harm the unit? What is stalling a servo? Is that if it hits physical limits but we are calling for more. I make sure my flap settings are off the stops. Is stalling really ever going to happen real life and be a valid operational need?

PS. These weigh in at 27.12 grams with a 4" servo lead. Yes my scale is that good .
May 20, 2014, 08:21 AM
ClearView Rocks!
Quacker's Avatar
I will test any aspect of anyone's radio gear that I am capable of for free, as a service to the community.

To stall a servo, turn on the tx and rx and apply maximum force to the output arm while observing the servo current. Alternately, hold the arm still while moving the stick. The validity of this test comes from the fact that in real life, about this much current can sometimes be drawn for a brief moment, just as the servo starts moving. Although very brief under normal circumstances, it can still be long enough to trip an over-current circuit that is not designed to filter peak currents.
May 20, 2014, 08:31 AM
Registered User
elkski's Avatar
To be valid test you would need the same servos. Or is there a current hog of the ones we commonly use? Mks65, I have Jr285,mks DS6100 ,94802 and DS09.
Last edited by elkski; May 20, 2014 at 08:43 AM.
May 20, 2014, 08:49 AM
ClearView Rocks!
Quacker's Avatar
It goes without saying that each servo type would need to be tested.
May 20, 2014, 09:34 AM
Registered User
elkski's Avatar
Well if your prior testing has revealed one of those servos to be the max current draw champion we could just use that type. It wouldn't be a complete test matrix but it doesn't sound like an easy test to do or setup?
May 20, 2014, 09:38 AM
G_T
G_T
Registered User
Think of a treed plane or one on the ground in bushes or weeds. The servos can easily be stalled for a while by obstructions. Moving the sticks and using the DS09 sound to home in is an old technique - which also can draw high current when the servos are pushing the plane around against an obstruction. Additionally, if one does ballistic descents from altitude with ballast and then some high speed maneuvers possibly involving flaps, the current drain may get up there, particularly if the voltage is low (single cell, and battery getting low).

Gerald
May 20, 2014, 09:58 AM
ClearView Rocks!
Quacker's Avatar
Quote:
Originally Posted by elkski
Well if your prior testing has revealed one of those servos to be the max current draw champion we could just use that type. It wouldn't be a complete test matrix but it doesn't sound like an easy test to do or setup?
As you may be aware, manufacturers (especially in Asia) frequently change their designs without notifying the buying public. Therefore I think a test matrix, however complete or not, is not as good as an actual test of the servos the individual intends to use. This philosophy extends to any ESC or battery protection circuit that is being contemplated.

Would I risk my $1000 investment on someone else's published numbers - even if the person that published them was credible? Not if the test was something I could easily do myself.

All I'm offering is a resource for those that want to do their own testing, but don't have the equipment or background.
May 20, 2014, 10:43 AM
One Idiot is plenty...
Dbox's Avatar
I use single 1200mha LiPo in one of my planes with 2 Hyperion D09 and two Dymont 4.7 servos.
After 72 min of non stop flying ( different air conditions at the beach )
Battery was drained down just 174mah,
I never fly more then about 1 hour on ANY battery pack or single cell and rather have spare
instead of more electronics on board.
More electronics= more chances for disaster.
Yuri


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