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Another Lipo question .....
- Thread starter synthnut
- Start date
Critterhunter would be best to answer that as i only use them in the sovXS2aPro and GT so far and they give the battery low warning well before the critical low voltage of the lipos i'm using, but in other aparatus i would imagine they are designed from the ground up for lipos and hence an automatic cutoff voltage above the lipo low would be incorporated in the design like say in a telephone or laptop. For RC there are al types of sensor gismos to help not to over discharge
Critterhunter
New member
Yea, lipo intended things have the low voltage alarm set for that many cell lipo. For instance, in RC something called a speed control or ESC is what the lipo plugs into. This device feeds power to the motor based on your throttle position. The ESC plugs into the RX and the RX is fed 5V via a BEC (voltage regulator) in the ESC as well. The ESC plugs into the throttle servo plug connector on the RX, so when you increase throttle the RX tells the ESC that and it increased power to the motor by pulse width modulation (turning voltage on and off real fast, more throttle faster on/off pulses). The ESC, as said, also feeds 5V to the RX and thus the servos plugged into the RX via the same plug that the RX feeds back throttle position to the ESC with. The motor is fed the full lipo voltage and not the 5V that is stepped down for the RX/servos. Kind'a neat how it does it. Anyway, way off subject but figured you guys would be interested in how the RC stuff works. Back to the main point- The ESC is programmed by doing some on/off stuff with the throttle at power up to set certain things. This only needs done once. You increase the throttle to full, then turn on the RX, and because the throttle is full at the ESC's power up it puts it into a programming mode. Things like a prop brake (stops prop when no throttle and holds it still, instead of letting it spin freely in the wind when throttle is off), and more importantly the LVC (low voltage Cutoff). You can set it for using a nimh or nicad, or you can set it for a lipo. A 3 cell lipo's cutoff would be 3V per cell, so in series that's 9V. When the ESC sees the voltage get down to around 9V it cuts off the power to the motor to tell you it's time to land. You can turn off the throttle when that happens and then throttle back up for ten or twenty seconds at a time to get the plane ready for a landing, and the ESC will keep cutting off the motor every 10 or 20 seconds of run time to keep reminded you it's time to land.
WAY off subject to get to that point concerning lipo LVC. Sorry about that. Anyway, so things like cell phones or lap tops have a preset LVC for using a lipo. Luckily the Sovereign's LVC is well above 9V so you don't have to worry about draining a lipo too far, which can ruin it. Never below 3V per cell. So like Kered said your AT Pro probably isn't going to have a high enough LVC (6 Volts for a 2 cell series lipo....Remember it would be 9V for a 3 cell series pack). Bottom line- I'd use the lipo for say 5 hours and then check it's voltage. Is it still well above like say 7 volts? Then use it say another 3 to 5 hours and re-check the voltage. Once it gets down to say 6.5 to 7V then that's the time I'd re-charge, and now you know how long you can use one in it before re-charging. Lipos tend to hold their voltage high to the very end, so when it's say around 7 volts to maybe 7.5 or something that means it's ready to drop real fast after that. I wouldn't push more run time than it draining to 7V. Once it hits that re-charge. Time your field use for no matter than that amount of time. In fact, to be safe I'd shorten it by an hour or so because current draw might be quicker if say you were hunting a trashy area where the machine is sounding off to targets more (more current drawn when it's hitting targets).
WAY off subject to get to that point concerning lipo LVC. Sorry about that. Anyway, so things like cell phones or lap tops have a preset LVC for using a lipo. Luckily the Sovereign's LVC is well above 9V so you don't have to worry about draining a lipo too far, which can ruin it. Never below 3V per cell. So like Kered said your AT Pro probably isn't going to have a high enough LVC (6 Volts for a 2 cell series lipo....Remember it would be 9V for a 3 cell series pack). Bottom line- I'd use the lipo for say 5 hours and then check it's voltage. Is it still well above like say 7 volts? Then use it say another 3 to 5 hours and re-check the voltage. Once it gets down to say 6.5 to 7V then that's the time I'd re-charge, and now you know how long you can use one in it before re-charging. Lipos tend to hold their voltage high to the very end, so when it's say around 7 volts to maybe 7.5 or something that means it's ready to drop real fast after that. I wouldn't push more run time than it draining to 7V. Once it hits that re-charge. Time your field use for no matter than that amount of time. In fact, to be safe I'd shorten it by an hour or so because current draw might be quicker if say you were hunting a trashy area where the machine is sounding off to targets more (more current drawn when it's hitting targets).
I guess I first have to see how much room there's gonna be in the battery compartment ......That will better tell me how big a battery I can go with ....I may not be able to use a very big battery at all , in which case i will be stuck using AA's ......???......If the Lipo ends up running for less time than tha AA's since I have to keep a watch on it going too low in voltage , I might be better off just staying with AA's ....I'll have to see when I get it ......Thanks, Jim
I would think a good set of nimh 2900-3000mah would give a real good opp time, and its also easy to carry a spare set, say eneloop(low self discharge) or something similar for spare, they don't have a high mah as yet but they don't self discharge like normal nimh so would be better for emergency use, and use a set of normal high mah for usual use.
Critterhunter
New member
Usually a good nimh or nicad will hold more capacity than the label says, like say 2800 or 2900ma in a cell that is labeled 2500ma...So long as you set the m/v properly. 12 or 14 m/v for a nicad, 5 to 7 m/v for a nimh. I usually use 14 for nicads and 7 for nimhs, but will drop it down a few digits if I'm really slow charging the pack (say 1/10th C for a 10 hour charge time) because the voltage drop will be less at a lower charge rate.
I bet you can get a pretty high capacity lipo in there. Are all four cells laying flat? Remember in a GT the width of the battery allows up to a 1450ma size battery (in certain lipos) such as the TX pack Kered is using (I'm using a 750ma Rhino 3 cell like Synthnut is), but that's 3 cells in series and in the lipo pack those are laying on top of each other like a stack of cards. In a two cell lipo pack you'd only have two cells laying on top of each other so it would be 1/3rd thinner than a 3 cell pack, so you should be able to fit a much higher capacity lipo in there assuming it's length/width is within the size of your holder.
I like my 2500ma Energizer nimhs from Walmart, and I think they now have 2700 or higher cells there now but haven't checked. Either way, it's been about four years or more since I bought those and if the trend holds like it has over the last ten years then I expect the capacity they are selling is higher now. Back four or five years ago I think the highest AA capacity you could get was perhaps 2800 or 2900ma, but these days I bet it's 3300 or more if you look around. In fact, I think Hobby King/Hobby City (they changed the name a while back and can't remember which is which) where you got your Accucel and lipos also sells nimhs and nicad loose AA cells. I'd check there to see how high they are.
Hey, while you're at it I'd look at what other AA loose cells they have in other lithium type cells. LifePo and probably 2 or 3 other variations in lithium technology (somewhat different than the Lithium Polymer cells we bought for our Sovereigns). Some of those cells are going to have higher capacity than a nimh in an AA cell package, yet a least a few of them can withstand lower drain downs than our Lipos (3V per cell). Can't remember off hand what various lithium types our Accucels support so skim over those various types it will charge and then compare that to the various types of AA lipo cells Hobby King sells and what their qualities are. Also, some lithium make ups use the same charging technique as others I think, so find out which will work with what type of charge mode. Some of these names they call these cells are labeled as a brand name and that can get confusing as to what cell charging modes they can charge under, if you know what I mean.
If you say find an AA type lipo variation that will work with one of the charging modes the Accucel supports then you'd have to set the charger to that cell type, under which it also changes the per cell voltage. Note, for whatever odd reasion the voltage per cell it lists in the setup doesn't match what that type is. In other words, for Lipos we are using you would think it would say either 4.2V per cell (full charge voltage) or 3V per cell (minimum cell voltage), yet it says something in between that that is probably an averaged voltage level. Just like when selecting the number of cells it says something like 11.1V for a 3 cell series Lipo pack when you would think it would say 12.6V (4.2V per cell) for a 3 cell series pack. I always assumed that's an average voltage they show, just like the average voltage industry standard listed for nimhs/nicads is 1.2V per cell when in reality a good pack will charge much higher than that.
And you thought I had run out of things to talk about concerning chargers/battery chemistry.
Would have figured I spent myself out in all the stuff I rambled about in the big thread. Nope.
I might do some brushing up on those various lipo (lithium) types on there they sell in an AA and then do an overview on here of those and what mode on the Accucel you'd set to charge them. Might be some real nice AA cell types you can use in your GT, or in other machines such as that AT Pro where they might not have a good LVC for using the lipo type we are using in the Sovereigns.
I bet you can get a pretty high capacity lipo in there. Are all four cells laying flat? Remember in a GT the width of the battery allows up to a 1450ma size battery (in certain lipos) such as the TX pack Kered is using (I'm using a 750ma Rhino 3 cell like Synthnut is), but that's 3 cells in series and in the lipo pack those are laying on top of each other like a stack of cards. In a two cell lipo pack you'd only have two cells laying on top of each other so it would be 1/3rd thinner than a 3 cell pack, so you should be able to fit a much higher capacity lipo in there assuming it's length/width is within the size of your holder.
I like my 2500ma Energizer nimhs from Walmart, and I think they now have 2700 or higher cells there now but haven't checked. Either way, it's been about four years or more since I bought those and if the trend holds like it has over the last ten years then I expect the capacity they are selling is higher now. Back four or five years ago I think the highest AA capacity you could get was perhaps 2800 or 2900ma, but these days I bet it's 3300 or more if you look around. In fact, I think Hobby King/Hobby City (they changed the name a while back and can't remember which is which) where you got your Accucel and lipos also sells nimhs and nicad loose AA cells. I'd check there to see how high they are.
Hey, while you're at it I'd look at what other AA loose cells they have in other lithium type cells. LifePo and probably 2 or 3 other variations in lithium technology (somewhat different than the Lithium Polymer cells we bought for our Sovereigns). Some of those cells are going to have higher capacity than a nimh in an AA cell package, yet a least a few of them can withstand lower drain downs than our Lipos (3V per cell). Can't remember off hand what various lithium types our Accucels support so skim over those various types it will charge and then compare that to the various types of AA lipo cells Hobby King sells and what their qualities are. Also, some lithium make ups use the same charging technique as others I think, so find out which will work with what type of charge mode. Some of these names they call these cells are labeled as a brand name and that can get confusing as to what cell charging modes they can charge under, if you know what I mean.
If you say find an AA type lipo variation that will work with one of the charging modes the Accucel supports then you'd have to set the charger to that cell type, under which it also changes the per cell voltage. Note, for whatever odd reasion the voltage per cell it lists in the setup doesn't match what that type is. In other words, for Lipos we are using you would think it would say either 4.2V per cell (full charge voltage) or 3V per cell (minimum cell voltage), yet it says something in between that that is probably an averaged voltage level. Just like when selecting the number of cells it says something like 11.1V for a 3 cell series Lipo pack when you would think it would say 12.6V (4.2V per cell) for a 3 cell series pack. I always assumed that's an average voltage they show, just like the average voltage industry standard listed for nimhs/nicads is 1.2V per cell when in reality a good pack will charge much higher than that.
And you thought I had run out of things to talk about concerning chargers/battery chemistry.
Would have figured I spent myself out in all the stuff I rambled about in the big thread. Nope.I might do some brushing up on those various lipo (lithium) types on there they sell in an AA and then do an overview on here of those and what mode on the Accucel you'd set to charge them. Might be some real nice AA cell types you can use in your GT, or in other machines such as that AT Pro where they might not have a good LVC for using the lipo type we are using in the Sovereigns.
Critter ,
Leave it to me to stretch that last bit of info from you !!..... I'm always coming up with things that are not the norm , and nobody can come anywhere near you when it comes to knowing batteries and chargers ..... The first thing I do before I load the batteries into this thing will be to measure the battery pack to see how much room I have to play with ....If it looks like I can squeeze a Lipo in there , it will happen !!!..... It will be here tomorrow , and while I am waiting I just took a dremel to my newly aquired SE to get the control box off of the arm rest !!..... I took my time , but it was a scary ordeal !!!..... I will have an SE/AT before long .... It will share coils with my E Trac so I don't have to buy 2 sets of coils ..... I will be building a seperate Lipo battery box for that one too !!...... I think my next order from H.K. will not be far off ....Another Accucell will be on the next list ....Always good to have a backup !!..... Thanks again for your help ....Jim
Leave it to me to stretch that last bit of info from you !!..... I'm always coming up with things that are not the norm , and nobody can come anywhere near you when it comes to knowing batteries and chargers ..... The first thing I do before I load the batteries into this thing will be to measure the battery pack to see how much room I have to play with ....If it looks like I can squeeze a Lipo in there , it will happen !!!..... It will be here tomorrow , and while I am waiting I just took a dremel to my newly aquired SE to get the control box off of the arm rest !!..... I took my time , but it was a scary ordeal !!!..... I will have an SE/AT before long .... It will share coils with my E Trac so I don't have to buy 2 sets of coils ..... I will be building a seperate Lipo battery box for that one too !!...... I think my next order from H.K. will not be far off ....Another Accucell will be on the next list ....Always good to have a backup !!..... Thanks again for your help ....Jim
Most of my AA's are Fujicell(2700-2900mah) but i have tried others, the Duracell(2650mah) ones i use in my garmin colorado don't seem to last as long by a big margin, bigger than the difference in mah. The wife bought me some Target brand at 2500mah that seem to be holding well too. Using the Accucel i can get more mah into all of them than whats on the label, even the 1600mah stock etrac battery takes over 1800mah charged from the cutoff point in the etrac.
Critterhunter
New member
Synthnut, make sure you take four new AAs and measure the in series configuration voltage of them. I'm curious to know if they are exactly 1.5V or if they are over that. If they are say 7 or 8V versus 6V then you'll be fine running a 2 cell lipo in the AT PRO. Make sure it's a 2 cell series pack, because they do sell various lipos wired in parallel configuration. I'd make sure I tested a few brand new quality brand name AA four cells in series and see what the voltage is. That would give me the confidence to run the lipo in there. Just the same, even if they are exactly 6V I still bet the AT Pro will work fine with the initial 8.2V of a 2 cell lipo. If you took the machine part and found the voltage regulator, which probably is a linear one...It would look like a flat square black thing roughly probably the size of your pinky fingernail. On top of it it'll have a flat metal piece that acts like a heat sink. This piece of metal might have a hole in it for bolting more metal to it to bleed off more heat for some applications. Anyway, turn the machine on. After about a minute feel that piece of metal. It can be slightly or luke warm but if it's getting hot stop right away. Check it again in say 5 or 10 minutes and see if it's still not getting hot. If not it's fine. Even if you get it too hot all the linear regulators I'm aware of have a thermal overload in them. What that means is once it cools down it should work again. But as said, if four new AAs measure say 7 or 8V you should be perfectly fine and wouldn't need to open it up and check this.
On the other hand, nimhs are great rechargable batteries. If four new AAs only measure 6V and you don't want to risk running an 8.2V 2 cell lipo in there then just use four rechargable AA nimhs and play it safe. Anything 2500ma or higher should run that AT Pro quite some time. Newer nimhs being made tend to hold their charge on the shelf better, but those Eneloopes (probably spelled it wrong) should be great as well.
Let me know what you end up doing. I'm real curious to see what four new AAs measure voltage wise. I don't have any new ones laying around to measure for you.
On the other hand, nimhs are great rechargable batteries. If four new AAs only measure 6V and you don't want to risk running an 8.2V 2 cell lipo in there then just use four rechargable AA nimhs and play it safe. Anything 2500ma or higher should run that AT Pro quite some time. Newer nimhs being made tend to hold their charge on the shelf better, but those Eneloopes (probably spelled it wrong) should be great as well.
Let me know what you end up doing. I'm real curious to see what four new AAs measure voltage wise. I don't have any new ones laying around to measure for you.
Kered,
Thanks for the info ...Much appreciated ...
Critter,
Great advise as usual .... I just ripped appart an SE .....I'm very happy about the way that Minelab builds their machines .....People talk about how expensive they are .....They are not only on top of technology, but the build quality of their detectors are 2nd to none .... Very well laid out , and put together .... Thanks again , Jim
Thanks for the info ...Much appreciated ...
Critter,
Great advise as usual .... I just ripped appart an SE .....I'm very happy about the way that Minelab builds their machines .....People talk about how expensive they are .....They are not only on top of technology, but the build quality of their detectors are 2nd to none .... Very well laid out , and put together .... Thanks again , Jim