LiPo battery protection circuit and altimeters.

[kweaver]

Altus Metrum says to remove LiPo Protection circuit.
Perfectflite and MissileWorks do not mention it.
Is it helpful to remove or just as good to leave the lipo as is, with either the Missile Works or Perfect flite altimeters?
Anyone!

 

[catman001]

I use no low voltage protection on any rocketry related electronics. When a LiPo is discharged past a certain point , it is damaged and needs to be tossed. While some people say that a over discharged LiPo can be saved by first charging with a Ni-Cad charger and then switching to a LiPo charger, even if it works, I would never trust that battery again. Low voltage cutoff is a good thing on items that are easy to over discharge like cell phones, laptops, cordless tools, ext. Save's you from having to buy a expensive battery, just charge them up and your good to go. While having a phone or laptop die is a bother, it is not mission critical. Having a battery on a dual deploy altimeter or GPS tracker cut out in flight is mission critical. I would rather loose a battery than loose a rocket or have one come in with no deployment. Battery's are cheaper than rockets. One problem that I see is that many people do not have good chargers and have no way to measure the internal resistance of a LiPo, which gives you a indication of it's health, so they think that if they use low voltage cutoff they don't have to worry about damaging the battery. I think it's one of those, penny wise-dollar foolish things.

Just what works for me.

Mike

 

[JohnCoker]

Is it helpful to remove or just as good to leave the lipo as is, with either the Missile Works or Perfect flite altimeters?

I believe this warning was only for certain LiPo cells, particularly the small ones Altus Metrum sold originally. I have used 2- and 3-cell LiPos with a variety of electronics without modification, and would be wary of modifying batteries.

 

[jderimig]

If you choose to use LiPo's with altimeters first I would simply email the manufacturer to see what LiPo or specifications for Lipo he/she recommends if recommended at all.

For MARSA alitimeters I recommend RC type liPo's with NO protection circuitry. I am not interested in protecting the battery, I want the battery protecting the rocket.

 

[ksaves2]

If you choose to use LiPo's with altimeters first I would simply email the manufacturer to see what LiPo or specifications for Lipo he/she recommends if recommended at all.

For MARSA alitimeters I recommend RC type liPo's with NO protection circuitry. I am not interested in protecting the battery, I want the battery protecting the rocket.

John,

Is there a particular liPo capacity you'd recommend for the MARSA family? Some makers say use too large a capacity and the mosfets are toast.
Your 54L looks pretty cool.

I agree about no protection for rocketry electronics. Lose then find after a long period of time and the battery will need to be tossed anyways no matter
what the device. Some of the Beeline trackers have a low voltage cutoff in the setup program and that will provide some protection in the short term but heck,
liPos are getting cheap now so why risk it. Kurt

 

[jderimig]

For the Marsa54 I recommend a 180-260mah HobbyKing 2S battery but you still have to be careful.

The Marsa54L has output current limiting so you can use any LiPo capacity you want safely. I hope to make this current limiting feature available in the Marsa54 as well with a future firmeware update.

 

[MWC]

Altus Metrum says to remove LiPo Protection circuit.
Perfectflite and MissileWorks do not mention it.
Is it helpful to remove or just as good to leave the lipo as is, with either the Missile Works or Perfect flite altimeters?
Anyone!

Leave it as is for the RRC2+/RRC3 when using the Sparkfun LiIon batteries...
I'd guess other LiPO's with current protection employ the same silicon, so I'd leave those as is too.

 

[SolarYellow]

Worth a necro on this thread, I reckon. It's getting to the point where there are certain combinations of capacity and form factor that are desirable and are readily available, but only with the battery protection circuits attached. I had not heard of removing them, so I searched and the goo took me to the AltusMetrum page:

https://altusmetrum.org/Documents/FixBattery/

Looks silly simple to do if you've already built an Eggtimer Apogee or Quark.

It also might be easier to just swap the leads than to try to repin tiny connectors or cut and splice the wires to resolve the issue of polarity conflict between battery ecosystems.

 

[K3LAG]

I have had a Altus Metrum TeleMetrum reboot when the battery limiter activated. When the ematch was fired for the apogee charge the limiter kicked in and rebooted the altimeter so the main never went off. Fortunately there was no damage to the rocket or anyone but obviously not desirable. Usually the cutoff of small LiPo's is a percentage of the total capacity of the battery. I typically remove the limit circuit these days on those small single cell LiPo's. What kind of initiator you are using will make a difference. If you don't want to remove the limiting circuit (and I understand why you might not want too) then you should do some ground testing with the the batteries and initiators you plan to use to make sure it's not going to cause a problem. If you have the space for it, using a bigger battery may make a difference as well as the cutoff current will be higher.

 

[cerving]

The 1S 110 mAH Lipo's we sell for the Eggtimer the Apogee altimeter have a battery protection circuit, never had an issue with them.

 

[SolarYellow]

Have you measured the maximum current they will deliver before limiting/shutting off?

 

[Azamiryou]

Does the protection circuit protect against high current, low voltage, or both?

 

[cerving]

Have you measured the maximum current they will deliver before limiting/shutting off?

No but it will reliably fire two MJG yellow ematches in parallel... that's a higher load than we recommend. And that's from a BJT, not a FET.