critterhunter

Well, today I impulse bought a new Pirahna Digital Peak Charger at the LHS. I didn't really have any complaints about the two (same) Horrizon Hobby car chargers that came with my Challenger and new Stryker. However, after reading about false peaks and that you might get more power and air time with a better charger, I decided to take the plunge. Hope I bought a good one as I didn't do much comparison price shopping. Main thing was it had a LCD screen which helps to set up and report battery information as it charges. But it will also handle something like 1 to 8 cells, do Nihms or Nicads, and can go AC or DC input power and output adjust all the way up to 5 amps. I'd like opinions on this thing if someone could.

Now, onto the junk instructions it came with...I wish it would have gave examples of battery cell count, ma, voltage, and thus the desired input settings to use as I am VERY lost with it. I'm kind'a sure about a few of the settings but for the most part I want somebody to walk me through it so I don't fry anything. Here's the NIHMS I'll be charging and need *all* the settings for...

6 cell 7.2v 900ma (horizon)
7 cell 8.4v 900ma (horizon)
7 cell 8.4v 1100ma (Venom)
And the settings for the standard Extreme pack as well as higher ma Extreme packs as I'll be charging a friends for him and also be buying one soon. Thanks for any help you can give me!

critterhunter

I think I've figured most of the programming options out but still have questions. For example, a nihm 900ma 7.2v cell. Capacity should be 900ma, I'm pretty sure of that. However, what's the proper rate to charge the battery. I thought I heard it's based on a percentage of capacity. In other words, a 900ma cell would be charged at .9amps, an 1100ma at 1.1amps. Is this right? Also, would there be any advantage or disadvantage to charging at lower or higher rates? My next concern is the peak threshhold detection number. I guess the lower the number settings the more precise the peak detection shutoff will be. I've got it set at the suggest 8 (forget the rest of the letters to describe it) for Nihms. Should I lower this to the lowest value in order to insure a complete and total charge to my nihms? Next, the trickle rate. I currently have it shut off after the battery is peaked off but is it a good idea to set it to something and if so how many MA? I'm trying to insure a full and total charge to various packs in the field. The way I understand it it's a good idea to slow charge a pack once in a while to re-train it, and slower ma charge rates will give longer run times. How much better than say .9ma for a 900ma pack will a lower setting give me result wise? Also, whats the maximum safe rate I should charge a 900 or 1100ma pack without doing damage. I know this is a lot of questions but I'm new at these chargers.

PS- Plan to pick up some 2500 (2800?) Nihm Energizer AA rechargables to run my TX on. If I want to charge them off this charger I'd need to stick them in some form of battery holder and set it up. In series, parallel, or what to do and how to set up the charger for the configuration?

guver

My Feedback: (325)

critter I think you have most of it figured out. You are correct about chargeing at 1C, yet the batteries you have may be quite tiny cells and may be charged at half that rate. (.45 amps)

If your 1100 is a larger size cell then you can go upt even 2C especially if it is a high discharge rate cell like 2/3 A cells.

On the trickle rate it should be turned off for the all of them as the minimum is 100 ma, it is too much .

The peak threshold should be around 3-5 mv per cell for nimh. It is input as a mv / cell value. The manual is wrong, as nicads shoukld be 5-10 per cell.

For your 2500 AA you can get a radio shack holder and charge at .5-1 amp (up to 2 or so if you are in a big hurry) they will be in series just like they are in the radio. 3- mv per cell for the threshold setting.

critterhunter

Thank you VERY much for responding. You are thus far the only person (I've posted elsewhere) who gave me any information on how to charge Nihms let alone on the Piranha charger. It seems like a good charger for the money as most of the units out there in that price range don't even feature the LCD screen. However, I am REALLY let down with the poor instructions. Well, I wouldn't say they are bad instructions if you already know what parameters and technical terms are for charging batteries. Just that they don't give you any examples of battery packs and the correct settings (and explain WHY) to use as a guide. I feel sorry for people with even less knowledge than me who tries to understand them. I mean, I'm not an expert at electronics but I can read schematics, build minor circuits, and do know how certain electronics parts work (diodes, resistors, etc) and why. Also, thanks for the correction to the misprint in the instructions!

I think the individual cells are what they call "sub Cs". They MIGHT be AAs cut in half but they seem a bit bigger in diameter than AAs. The car peak charger both planes came with has a dial with the range that will go up to I think 1.2 or 1.5 amps, so I would guess I'm in the ballpark for the batteries used on those chargers that I'm replacing with the Piranha. I'll check and charge accordingly. If these are the tiny types the charge rate would be .45 amps for 900ma packs, .55 amps for an 1100ma pack? Or, if they are "sub Cs" it'd be .9 amps for a 900ma pack, or 1.1amps for an 1100ma pack?

If these are the bigger cells you are talking about then you are saying I can go to 2C, which then would mean 2.2 amps for the 1100ma pack? (Remember, you are walking an idiot through this...) What would be the disadvantage of charging at such a high rate? Less run time, potential heat damage over the long term, etc? For the reverse, is there any advantage to charging these packs at a lower level than even 1C? Longer run times, conditioning once in a while? And while on that topic, I know Nihms don't share memory problems to the degree of Nicads but is it still a good idea to cycle them dead say every 10 charges or so?

I kind'a figured the minimum trickel setting of 100ma was too much for these batteries. I would have guessed that something more like 5ma would be a safe and good rate while the pack sat idle on the charger between flight packs. Too bad the Piranha doesn't go that low. Still, my packs only see maybe 30 minutes to an hour or so of sitting idle after they've peaked as we have two or three planes in the air at a time, swaping packs.

Peak threshold is still the weakest link in my understanding of Piranha setup. 3 to 5 mv per cell for nihms. Does that mean I add up the number of cells in a pack and then multiply that by 3 to 5mv for the proper value? IE: 7 cells (on a 8.4v 1100ma pack) X 3 = 21? I don't think I've got that right so could you explain further. Also, what is your suggested setting (per cell mv value) to get the tightest window to insure a good peaked pack that hasn't falsely peaked?

Onto the 2500ma AAs. I know how to wire in series so I should just wire up a holder to configure all 8 (or is it 6?) in series and charge at .5 to 1 amps (2 to rush things) with a 3mv per cell (see above confusion on this setting....3mv X 8?) threshold setting? And, for the capacity...is it 2500ma x 8? No, thinking back to high school electronics I think capacity only doubles if the batteries are in parallel. Only voltage doubles in series. On the right track? Sorry for all the questions but I want to get the best performance out of this charger without blowing up mine and my friend's packs.

guver

My Feedback: (325)

Ok, I am not a typer like you, but I did read carefully everything you typed and everything you said is correct. You really do have a good handle on all this. On your second to last paragraph (Peak threshold) the piranha is set up for putting in the mv per cell so for any nimh put in 3-5 (3 for small batts like you have) I can't remember if you input the number of cells or it just detects it, but the max value is 20 anyways so you do not have to do the math. just set it to 3 or 4 or 5. To decide on a good value you can start with a dead batt and check the capacity and also the temp when it is finished. Example would be if you use 3 mv and the battery stops at only half it's capacity and is just slight warmer than room temp you should increase to 5. Example of a correct setting would be if you start with a dead batt and at the end it charged to about 100% of capacity and was 30 degrees over ambiant temp or (110 deg F) then that would be an accurate charge. example of too high would be if the batt got very hot b-4 it kicked off.

critterhunter

Thanks very much again. Only one more concern. I thought I read in the instructions that the LOWER the mv number the smaller the "window" to detect when the battery is peaked, and thus you are more prone to have a properly peaked pack. Where as, with the higher mv numbers the window is wider and thus the pack is more apt to falsely be peaked? Thanks again, as I searched the web for information like this any could not find any useful information.

guver

My Feedback: (325)

Hmm (neighbor) You may not understand what the mv is. I'll try to explain it. Using the word "window" leads me to think you have the wrong idea.

throughhout the complete charge process the battery voltage will continue to go up . When the battery is full the voltage will peak and then very slightly start dropping. The amount of this voltage drop is what the charger is looking for and is what you had programmed. If you had set it to 5 mv and are chargeing 6 cells then anytime during the charge process that the piranha detects a 30 mv drop it will simply stop. The problem with some batteries (old, new, ect.) is that the voltage can be unstable during the charge ( especially the first few minutes) and it happens to drop the required amount to stop the charger. Most users will check capacity and just restart the process. I have also noticed that when chargeing at the max settings sometimes even then a major appliance in the house starting can at times cause the voltage to drop enough to "false peak"

hope this helps. Here's what I really think , it is you will charge just a few times and be an expert very quickly.

critterhunter

OK, I understand what the mv threshold does better now. Thanks for the explaination. However...the instructions for the Piranha charger state that a lower MV setting will be more apt to do a true "peak" of a battery pack PROVIDING that the current charge rate is low. Where as a higher MV number will be a better choice when using higher current charging rates. They roughly saw that at higher current rates the charger might get "tricked" into thinking that the battery is peaked at a lower MV setting and thus terminate when it hasn't really peaked. See what I mean about these instructions...Can't understand why they didn't provide some examples of what they consider "high" and "low" current rates and the best MV setting for specific pack configurations at those rates.

Onto yet another dumb question...I've heard elsewhere that many pack MA ratings are slightly under estimated. In that a 900ma pack might well be more in the range of a 1000ma pack or so. So, I'm wondering if I could tweak the capacity setting on the charger up just a bit, maybe 100ma over the battery rating. Might provide further insurance of a proper peak. What do you think?

guver

My Feedback: (325)

I see what you mean about the low/high rates and would have to agree. A low rate would be c/10 (for 10+ hours) in which the batt probably would not show a drop very well. A fast rate would be 3c (for 20 minutes) and will show a drop. Everyone seems to have their own ideas about rates, and it also matters what you are doing w/ the batter. On the low end are small radio batts that user is in no hurry for and cares about long battery life may charge at c/2 or less. On the other end of extremem is the car/truck racers that care little about battery life, but want maximum (punch) or discharge voltage and charge high discharge sub c's at 2c -3c.

I have had packs that are slightly under capaqcity and some that are over by 10-20%. I don't get your question though. If you are asking about the charge rate then you will see no difference hardly between chargeing at 900 ma and 1 amp. These are all general guidelines, not really exact rules.

critterhunter

What I mean is that I've heard the capacity rating on the pack (say 900ma) is said to often be under rated. In other words, a 8.4v 7 cell 900ma pack might really have about a 1000ma capacity. I'm not talking about the charging rate setting on the charger, I'm talking about the capacity setting. So....I was wondering if by changing the capacity rating on the Piranha charger from 900ma for the battery to 1000ma might this insure a more properly peaked pack as the battery might be capable of holding 1000ma of run time versus 900. I believe that the Piranha charger uses to or three criteria for determining when a pack has peaked. One is, of course, the MV setting. However, (and I may be wrong about this), I think the charger will also terminate if it has "counted" it's output up to 900ma (or whatever you set the capacity figure in the program at). I thought I read that this acted as a safety feature, in that if the pack never triggered the MV threshold to terminate the charger would stop once it had output 900ma of capacity. I believe the display shows a ma capacity counter on the screen while charging, slowly adding up to the specified capacity of the battery. Will have to (as you said) play with it a bit and see what mv and other settings seem to work best.

guver

My Feedback: (325)

Yes, some packs can hold more than they say. I guess I forgot about a max mah setting. Here's what I would do while watching the pack and temps. Start out w/ a completely dead batt and charge it up to note the actual capacity and then set the max for slight above that.

It will stop at what ever comes first. the voltage drop or the max mah setting. Hmm I still don't remember the digital having a max... I have to go see now....

critterhunter

I've been playing with the charger and learning more. Despite the poor instructions this charger is great and am very happy I bought it. For the $50 price range there isn't much out there that can compete with the LCD computer settings this unit features, and it still has most or all of the other features found on more expensive chargers. I would highly recommend this charger to anybody out there.

In fact, a friend had a "dead 1700ma NICAD pack that his charger (same price range) would not charge, saying that the battery was an "open circuit". This battery had sat in a tree for about two weeks stuck in an Extreme. Anyway, I hooked it up to the Piranha, set up a program for it with the m/v at 10, and blasted 5amps into it (his charger only goes up to 4). Within twenty some minutes the battery was fully charged and only slightly warm. I also brought some eight year old AA Nicads back to life that other chargers wouldn't charge. Watching the screen, it appears the charger's computer will even drop the amp output to the battery to adjust for battery condition as it goes through the charge cycle if it needs it. Being able to keep trickle from coming on after a peak is also a plus.

Now, the more I play with this charger the more I learn (and like it). For instance, peaked a 900ma 8.4v Nimh TWICE on the HobbyZone car charger and then, right after the second peak (which only took a few minutes), I placed it on the Pirahna. Set at .9 amps (same as I had the car charger set), 900ma capacity, 3 m/v threshold...The charger ran for around 10 minutes and put roughly 100 to 200 more MA of capacity into the battery. I did this with other "peaked" batteries and had similar results. This tells me that the car chargers are false peaking and the Piranha is getting more juice into them. They were only slightly warm to the touch after the charge too, so I know it isn't cooking them.

Now, my next test will be to take a Piranha "peaked" battery at 3 m/v and put it back on at 3 m/v right away to see how many more MA it puts in. I'll then use this as a guide and right away change the m/v setting to 5 and see if it puts more MA into the peaked pack than the re-peaking at 3 m/v. I figure this should be a good test to see what the best m/v setting for a normal charge would be to get the most complete charge into a pack.

On the capacity rating setting we've been discussing...The charger will indeed finish the charge if the capacity rating is met that you set the battery for. In other words, if the charger doesn't finish it's charge by the peak threshold being triggered then it will stop once it has hit the capacity rating you specified. It acts as a safety feature to keem from cooking a battery that isn't tripping the threshold for some reason. However, many batteries (as I'm finding out) will hold a bit more MA capacity than the rating on the pack. So, my suggestion is to set capacity a few hundred or so MA higher than the pack rating. This way, if the pack can hold more capacity it won't false terminate when a lower capacity setting is reached. However, I'd only do this if I'm around the charger for the duration because if peak threshold detection fails you might blow up a pack or start a fire or something.

Another example of the poor instructions is the example of screen one while charging. The instructions say the bottom numbers are the "output voltage". You would guess that this would be the output voltage from the charger. In reality, it's the pack's voltage reading. I noticed this when the upper right amp charge number would kick down to zero for a second or two (the charger does this as part of it's charging pattern). The voltage reading will instantly start stop it's slow climb and start dropping in voltage. A second or so later when the charging amps kick back in the voltage will instantly begin to climb again. As the battery reaches it's peak you'll notice that the battery voltage slows to a stop, then begins to go backwards. I guess this is what the m/v setting is all about. A fully charged pack will begin to drop in voltage and this is how the charger (via the m/v setting) knows it's peaked. By the way, again, poor instructions....the m/v setting is PER CELL. In other words, don't add up the cells and multiply the number. The charger does that for you. If you set it at 3 m/v and install a 6 cell pack the charger knows it's really 18 m/v total.

kb9vrg

That was the best explanation of this charger I've seen. I was growing concerned after trying to peak 3 new 1500mah nicad packs with the settings as they were in the manual and having them stop after 10 minutes.

After reading this, I'm glad I got this charger -- will be using it on my Traxxas Blast, Mini Mauler, and Micro Street force.

critterhunter

Spread the word. This charger can't be touched in it's price range but the instructions stink and there isn't a lot of advertising for it. I see other chargers by the same company get more advertising. Wonder why when they have such a winner on their hands.

guver

My Feedback: (325)

This is a great charger w/ lots of functions and adjustability. It has many thing I like about it, but here's what I don't like.

AC power is limited to 3 amps.

7 & 8 cell charging is limited to the amount of input voltage supplied.

It charges at the same rate as other 4.5 amp chargers at a max because of the open voltage test every minute.

critterhunter

Remember that many of the chargers out there in this price range don't offer both AC and DC inputs. My only complaint with it is I wish it would go below 100ma for the trickle rate at the end of a peak. If I could set it real low I could trickle a Nimh while it's in wait to fly. Not a big deal since they rarely rest more than ten or twenty minutes before I take them up. Now I wonder, is the 100ma minimum trickle rate setting too high for those huge Extreme packs? I'll be buying some 3000ma bad boys for the Extreme I'm parting together.

I mainly use mine hooked up to my car's battery in the field so I don't care if it won't go 5 amps on a wall outlet. You'll only need to go higher than 2 or 3 amps if you are charging some pretty big packs, like those on the Extreme, but again no problem in the field with the vehicle's battery. I also put a cigarette lighter fan on the car battery and have it blowing on the charger and the pack being charged. While it doesn't get hot on cool days, in hot sunny summer weather you are asking for trouble with any nimh or charger. Keep'em cool.

Also, by the way...so far my tests show no difference between 3 or 5 m/v settings for 900ma or 1100ma 8.4v nimh packs used in the Challenger/Stryker. On the other hand, when I was bringing some very dead Nicads (sat around for years) back to life I had to set the m/v setting to like 13 or 14. I think 8 to 12 is the normal range. Just if the pack terminates it's charge too quickly and you know it needs more charging bump the m/v number up a bit. Nimhs don't start dropping in voltage as much when they are peaked, while Nicads do...thus the lower settings for Nimhs and the higher for Nicads. If you adjust the charge rate to something drasticly high you may have to increase the number even more to avoid a false terminate. Remember also, keep trickle off for Nimhs after it's peaked, keep it on for Nicads while it's in wait to fly in the field.

turboex

OK I have the same charger, If I set it up the same way with no trickle on 9parkzone battyer). how do i know when its fully charged? It never seems to do anyhting but raise the voltage to like 10.xxx

guver

My Feedback: (325)

It is suposed to stop.... and the batt will be warm. If it is nicad or nimh.

critterhunter

Watch the voltage at the bottom of the screen while it's charging. As the battery reaches full it will slow down it's climb, then start to fall when the pack is peaked. Based on the m/v setting you put it (should be set in the 3 to 5 m/v range) the charger will terminate when the pack drops it's voltage below it's peak voltage minus the m/v X number of cells in the pack. It automaticly multiplies the m/v setting X the number of cells (IE: 3X7 cells=21m/v). So, when the peak voltage begins to fall it will terminate when the pack drops 31 m/v below the highest voltage reached by the pack during charging. Don't get confused if you see the pack voltage drop off and on, as it does this when the charging turns off the charging amps every minute or so through the charge cycle. You'll see the amp rating in the upper corner go to 0 when it does this for a few seconds. I also noticed that based on the battery condition the charger may change the charging amps to compensate for battery condition. Nice feature. I have a Venom 8.4V 1100ma pack that it likes to drop the charging rate lower on. It turns out this pack is weak as it doesn't have the juice it once did. In order to correct this I'm going to drain the pack completely, then charge at a real slow rate of .1 to .5 amps. This should help the pack rebalance it's self, but will take probably 3 to 7 hours to charge it. It's good to do this with a new pack for the first charge or for any pack after 20 or 30 charges. In normal field charging, I try to follow the rule of .9 amps for a 900ma pack, 1.1 amps for a 1100ma pack. If I'm in a hurry I may crank either pack up to 1.2 to 1.5 but this isn't as good for the battery as the normal charge rate. The slower the charge the more juice you get into the pack and the better it is for the battery.

critterhunter

The more I use this charger the more I like it. Yesterday I took an 8.4v 900ma pack and wanted to charge it quicker than I probably should. I set the charging amps to around 1.8 and I noticed that for a while the pack was charged at this rate, but as it went on the charger would lower the amps to 1.3, 1.1, or even as low as .8 amps. I kept feeling the battery through out the charge and it never got hot. So, for now on when I'm in a hurry I'll charge my packs at close to 2 amps for the Stryker/Challenger, as the charger appears to read the condition of the pack and safely lower amps as needed. When I'm ahead of my packs at the field I'll simply stay with the .9 amps for 900ma, 1.1 amps for 1100ma pack rule. Did some more testing and after peaking batteries on the Hobbyzone car charger several times and then plugging them into the Piranha I'm still getting 80 to 200ma of more juice in the pack and it isn't getting hot.

guver

My Feedback: (325)

The digital piranha is lowering the rate because it is "wide open" the input voltage is not enough to maintain the output amps. By increasing the input voltage it will maintain the original setting (charge amps)

critterhunter

Hmmmmm....Are you sure? I was charging from my vehicle battery, which isn't more than two years old. The input voltage was roughly 12.70 volts as I always check it to see if the battery is weak. When I charge an Extreme sub C pack at a higher rate it never lowers the output amps, but if I try to charge the Sub As (?) that are used on the Challenger and Stryker at a "high" rate of 2 amps it will maintain this charge rate for about one half of the charge time, then drop it lower and lower down to .8 or .9 amps as the pack approaches full charge. I assumed it was doing this if the voltage up drift wasn't as fast as it should be for the pack at the specified amps, thus lowering it to try to get a fuller charge into the pack. Will have to do some further investigation on that. Perhaps on a wall outlet where I know the input voltage isn't being decreased.

guver

My Feedback: (325)

Yes I am sure, to test just charge 4-6 cells and it will charge at full 5 amps then charge 7-8 cells and you will see that it will keep dropping the more it charges. It's really not a bad concept though.

critterhunter

Got a quick but somewhat unrelated question for you...Aren't there pretty much two types of cell sizes for various electric planes out there....Sub A and Sub C? The reason I'm asking is because I'm parting together and Extreme and just ordered two 10 packs of Sub C 3300ma cells with solder tabs. $25 per 10 pack aint bad. I'm going to solder two 7 cell packs and one 6 cell out of them for the Extreme. Anyway, now I'm wondering if I bought the right size cells? I'm almost positive that the bigger cells used in the Extreme are Sub Cs. By the way, batteryspace.com has some great prices. 7 cell 1100ma Nimh flight packs for the Challenger/Stryker are only $19.99 for TWO packs plus like $5 shipping. Have read nothing but good things about these packs and they are rated at 15C. Even comes with the proper connector. On the other hand, my 7 cell Venom 1100ma pack is acting slugish now...like a 6 cell. I drained it completely and am slow charging it at .1 amps...which should take around 11 hours. If that doesn't recover it then I guess I've got a toasted cell in there that needs replaced.

guver

My Feedback: (325)

I really don't know, but I would guess they are sub C and then 2/3 A.

I'm a car/truck guy and use only sub c and AA's.