LiPo Ready - Is My Rifle LiPo Ready? How can I tell?

[m102404]

Originally Posted by Timely A.

What if the gun is LiPo ready, then do I have to get a LiPo? or will it work with a "normal" battery?

Not at all. If the mechanical system is working properly (i.e. all the gears/shimming/setup/etc...) then power is power is power. As long as the battery you choose can supply enough Amps to power your system efficiently, at a voltage you desire...then you're good to go. Be it NiCd, NiMh, LiPo, LiFe/LFP, etc...

[Shooting Addict]

Whats a PCB I've heard thunder cactus say it's necessary for lipos setups?

[Scalpel]

The PCB monitors the voltage of the Lipo, giving you a series of warnings.
Some are apparently not very accurate, but for just a few bucks and a bit of piece of mind, I say even a cheap one is worth it.
I just switched from a mini 9.6v to a 7.4v 20c lipo and the rof is identical.

[m102404]

Originally Posted by Shooting Addict

Whats a PCB I've heard thunder cactus say it's necessary for lipos setups?

That's not entirely correct (as per his last/latest post). He's said that a PCB is not absolutely necessary...but a good thing to consider.
Personally, I do not use one.

A PCB (protection circuit board) is a set of chips/circuits that cuts off the draw of power when the voltage drops below a given threshold.

The primary reason for doing so is to help ('cause everything can fail) ensure that the voltage of your lipo cells do not drop below their safe lower threshold.

A typical LiPo pack is made up of 1 or more cells. Each cell has a nominal voltage of 3.6v...so a 7.4v pack has 2 cells...a 11.1v pack has 3 cells...etc...

Each cell has a lower threshold of 3v. Once it drops below that there is a high risk that the cell is permanently drained and will not charge up properly. They have an upper limit of 4.2v...they are not designed to be charged up past that.

So if you take your "11.1v" LiPo and charge it up...it's going to charge to 12.6v. If you've got a "dead" cell that's not charging up properly...and don't have a smart charger that will 1) prevent overcharging any given cell, 2) detect that there's a problem cell in the pack...and you just charge it up to 12.6v, you'll be driving the remain 2 good cells WAY past their upper threshold. Can't be good right?

*** A quality smart charger and balancing system (often built into the charger) is a MUST HAVE for LiPo batteries. ***

When you rapidly drain a battery (any battery)...the chemical reaction produces heat as a by-product. The heat produced can often be sufficient to "boil" the contents of the battery...damaging 1+ cells. So it wouldn't be a good idea to try to charge that now damaged pack right?

When you "normally" drain a LiPo...you don't want to take any given cell past 3v ('cause then you have issues when charging it up). That's where the PCB comes in.

For a "11.1V" PCB...it'll cut off ~9v (3 cells, 3V/cell). For a 7.4V PCB...it'll cut off at 6v (2 cells, 3v/cell). Obviously you can't use a 11.1v PCB for a 7.4v battery...cause even at 2 cells x 4.2v = 8.4v max charged up it'll trip the circuit and cut power. Guess what will happen if you use a "dumb" 7.4v PCB for a 11.1V battery?

Now, in practice...when your battery (any type of battery) starts to run out of power you should be able to notice a drop in ROF, and slowness in the trigger response and a longer "wind up" of your gears in the mechbox. When that happens, your battery is almost depleted. How fast it gets there is dependant on your battery, your rifle/setup and how much/fast you shooot. When I notice this drop off, I stop using the battery....you're just over draining the battery and performance sucks anyways. LiPo's tend to drop off quicker and more suddenly than other batteries.

Now, in reality...some guys are so stupid that they might as well stick their heads in a hole and have their buddy fill it in. They'll never notice how their rifle is performing, they'll not take care in checking how it's charging, how it's changing over time, etc... Those dummies should be using LiPo's...and perhaps even they shouldn't be shooting at other people (that may be overly harsh ).

Also note...some PCB's that are just simply "in-line" between the motor and battery simply detect the overall voltage and not the voltage of any one specific cell. They are cheap...and should be avoided like the plague. To be effective a PCB should be monitoring the voltage of each cell of a battery pack.

Additionally...batteries are basically bags of layered chemicals. Hopefully they are produced consistently and held to high quality control standards. In reality....how much QC to you think goes into a $12 discount, no-name battery that you're buying off some faceless dude on e-bay?

Each cell can last/behave/react a bit different from another. Each cell has multiple contact points that can be damaged by/though use and handling.

Due to the consequences of mishandling/use of LiPo's...they require that their users understand what they are, how they behave, how they'll react and how to care for them.

Same should go for NiMh and NiCd batteries...but they are not likely to burst into flames and kill everyone in your building.

[Shooting Addict]

Alright thanks Ty for explaining that up for me

[ThunderCactus]

I'd just like to add in, although a PCB isn't necessary running an older model TM, the new triggermasters are setup for 6v and 9v cutoff on LiPo's.
I'd say it's pretty well mandatory to use PCB's on the newer models. Older models cutoff at 80% of input voltage, which was a nice safe margin above your minimum voltage. But the new models cut off right at your minimum voltage, but with no individual cell voltage monitoring.

[m102404]

Originally Posted by ThunderCactus

I'd just like to add in, although a PCB isn't necessary running an older model TM, the new triggermasters are setup for 6v and 9v cutoff on LiPo's.
I'd say it's pretty well mandatory to use PCB's on the newer models. Older models cutoff at 80% of input voltage, which was a nice safe margin above your minimum voltage. But the new models cut off right at your minimum voltage, but with no individual cell voltage monitoring.

I got kind of confused...but think I sort of got it.

So main point is that new TriggerMasters with built in cut off are like "dumb" (sorry Don) cutoffs...they won't really accomplish what needs to be done...which is monitor each cell of the pack.

And, unless I'm mistaken, the 80% cutoff isn't a cutoff...it's a warning buzz. The cutoff is lower isn't it?

80% of a fully charged "11.1v" battery is really 0.8 * 12.6 = 10v..so that's ok. But if your 3 cell LiPo doesn't start off fully charged you could run into an over discharged state by the time the cutoff kicks in.

I think the cutoff works for a 2 cell LiPo though.

[ThunderCactus]

Actually, Don, in all his infinite wisdom, actually has a safety device for that exact scenario on the old TM's
If you read the instructions it says to consistently use the same type of battery with your TM. If you have a 9.6v 1500mah pack, ONLY USE 9.6v 1500mah packs. Don't be switching between an 8.4v large and 9.6v mini, etc.
Now obviously the triggermasters have memory since they remember settings, well they also remember the highest recorded input voltage!
This means, you plug in a fully charged 11.1v LiPo, it records the input voltage at 12.6v. You game with the LiPo for a few hours and drain the cells down to 10.8v. You don't charge your LiPo and come back next week, you plug in your batt at 10.8v, but because the TM remembers the 12.6v input voltage, your cutoff is still 10v
By experience I learned this by switching from 9.6v NiMH immediately to a 7.4v LiPo. I plugged in the LiPo, tried to shoot and it just gave me the battery low warning and refused to function. 80% of the peak voltage of a 9.6v NiMH is around 8.4v.

IMO the old TM MKIII is the safest SW-comp to be used with LiPo's if you don't have a PCB. Internal fuse, MOSFET, input voltage memory, and 80% cutoff that's safely above the minimum voltage of LiPo's

[m102404]

That's cool. After the last time I discussed this with him I came away with the impression that it was 80% (or 82% or something like that) of the voltage of the battery when it was plugged in and the unit powered up. So start with a fully charged battery and you're ok...otherwise not so good.

Thanks for the correction though...that's significantly different from what I understood.

[Jackarutu]

ThunderCactus,

Becasue you have all this experience would you be so kind as to provde us with some quality pictures of how to route the mosfet wiring through the version 2 gearcases wried to the rear and the stock tubes?

[ThunderCactus]

I've done it before, I don't have pics though, but I can tell you how I did it.
Route your motor wires (18 gage) as per normal rear stock configuration. So from motor to rear end of the mechbox with one wire going underneath the pinion gear of your motor.
And run the trigger wires (20 gage or smaller) around the OUTSIDE of the mechbox, one on each side.
As I recall they don't fit in the lower reciever, so they run across the side of the mechbox and sit on the inside of the UPPER reciever once you slap the gun back together.
Once the mechbox is back in the lower reciever, the motor wires run out the back end just like they normally do, and the trigger wires have to drop into that area before they reach the end of the lower reciever, because the upper and lower have a lip that locks them together right at the back.
Now the tricky part is on some AEG's you MAY require some modification.
Some lower recievers have tabs that will prevent the wiring from going in. This spot is geographically directly under the back end of the spring guide. You may have to dremel in grooves to run the wires, no big deal, took me 5 minutes.
So once you get that out of the way, you have all 4 wires coming out the back of the lower reciever.

Things to watch for-
don't pinch the wires anywhere, especially around where the mechbox meets the lower reciever.
Take care installing the buffer tube so you don't crush the trigger wires, because they're thin and flexible they can easily get caught under there. Just hold them tight while you screwing the buffer tube back on.

Hope that helps, let me know if you need pictures and I'll try to get them done around 0900 ZULU

[Jackarutu]

Outstanding,

I thought about running them on the outside but gave up early on becasue I feared getting them pinched and cut in the lower reciever but you have inspired me to take a second look.

I work mostly wth Modify gear cases on custom work with version 2

[phloudernow]

Not will a lipo damage your gearbox if it isnt set up properly, but you can also burn out your switch, this happened to me before, i threw a 7.4 lipo into my King Arms Larue 9 inch and had to sit out a middle of a game and replace it before getting back into the next one

[ThunderCactus]

Like I tell everyone, the whole point of upgrading to LiPo is better energy efficiency (and this is especially important for people wanting buffer tube LiPo batteries) therefore it only makes sense to get a MOSFET switch and upgraded wiring as well. It makes SUCH a big difference in efficiency, and helps you squeeze every last drop out of that tiny little stock tube battery lol

[SniperVann]

I got a question an if its been answered here im sorry but my question is how can you tell wat amp your motor safely runs at and how much amps your battery put out whether its lipo or not