Polimax B6 Charger & Mystery Balancer/Watt meter

[john66]

My Watt meter turned up just 20 min ago, which is pretty damm fast from HK to UK with a bank holiday in between as well as continued volcanic disruption to air traffic in between. I only hit buy it now and paid on the night of the 21st may. I still await an Ernst Ultra stand from my atomic in the US which was purchased on the 11th may!

Anyway I took out my stock battery which had been put away on storage rechecked the cells on my polimax, they read 3.79 each, I then plugged it into my mystery watt meter/balance/batt checker and they showed as 1. 3.84 2. 3.81 3. 3.81 one or both of them is a dirty cheap cloned liar! which one? both prob, but from what I can gather being within .02v - .05v there is nothing to worry about. My stock battery is currently on charge in order to test them on the watt meter with my XYH 1250kv & 1100kv with various props. I have 3 different 3 blades for the 1250 which is for my PZ spit and 2 diff 2 blades (exc stock) for the 1100 for my cub build. Will hopefully post the albeit inaccurate readings later.

John

[flydiver]

I've got one of those little field battery checkers. I know it lies on cell 3 to the tune of 0.05v.

That's one of the problems with cheap electrics-you can't entirely trust the readings and output. Mostly a few 1/10's of a volt don't matter. On a charger though 4.2v/lipo is pretty much the max. It's OK to charge less and this is actually better for the battery. I frequently stop at 4.1-4.15v (Cellpro). If you are consistently charging higher inadvertently due to inaccuracy it is harder on the battery.

One of the problems with the AC-6 & clones is the charge voltage is a lot more about where it intends to end up than what the actual battery state is doing. You can't use it to determine a specific stopping voltage by setting or by read out.

[john66]

Thanks for the input flydiver, I will try to remember to manually stop my charge in future just below the 4.2 mark.

John

[flydiver]

Again, listen up here, that will NOT work with ANY of the AC-6 clones since it tells you what it is FEEDING the battery but NOT what the battery voltage state is. If you wanted that capability you needed a better charger.

When you FIRST plug in a lipo and check the individual cell voltage you get a 'somewhat' accurate reading. NONE of them are dead nuts accurate at lower capacity reading. In pretty short order on the clones this reading will soon be very near 4.2v/cell but be no where near done. The only readout that may be somewhat reliable is the final mA put back in and final finished voltage.

You get lots of guys that spend time on line crowing about how these things are sweeter than their girlfriend and more reliable than their mother. This is just men parroting BS they got from other men that were BS'ing on the net. It gets deep fast. Very few have the skills or the equipment to back up their claims. Rumor is not knowledge or fact.

[john66]

Sorry I misread your previous post. I guess the real test of my charger and its use to me will be how long my batteries ultimately last.

[flydiver]

The charger will help with long term lipo longevity. You need at least basic info and reliable charging - minimum. The stock charger gives you neither.

How YOU use lipos ultimately will count more.

[john66]

Jun 1, 2010 18:32:16 GMT 1 flydiver said:

The charger will help with long term lipo longevity. You need at least basic info and reliable charging - minimum. The stock charger gives you neither.

How YOU use lipos ultimately will count more.

Understood, I always use my field tester between flights.

John

[Dillzio]

Actually, you can use the charger to read the voltage of the batteries, and it seems to be more accurate than the basic little lipo testers that plug into the balance plug. I'm certain it's not as accurate as a fluke multimeter of something like that, but I find it does the job. I've compared voltage readings from the charger, my two lipo tester boards and two multimeters. I found I got the most consistent readings from the multimeters and the charger. With the smaller checker boards some cells would read a little lower than it should, one board was out by .02v on cell two and the other .03v on cell three.

If you want to check your battery voltage with your charger, you MUST hook it up in a 0.1a charge or discharge cycle to avoid battery sag. If you start charging your battery at 1C you'll see an instant increase in the battery voltage, but this does not accurately indicate the charge state of the battery. Likewise, if you start using your motor at WOT, you'll see the batter voltage instantly go down. This is 'battery sag', momentary fluctuations in battery voltage caused by load on the battery.

Another tip in case you're afraid of overcharging your batteries... use the fast charge function. When the charger gets to the end of the charge cycle, it backs off the charging current all the way down to 1/10 of what it was when it started. Basically it charges at the set charge rate (1C for example) until the voltage per cell is at about 95% capacity, and then it backs down the charging current to prevent the battery from going over about 98%. As the battery gets more full, the charging current has to be backed down more and more to prevent the battery voltage from getting too high.

In a normal charge cycle, it backs the charging current down to 1/10 of what it was when it started, and then when the battery gets to the point the cells are about to click over to 4.21v it turns off and the charge cycle is complete. If you put it in the FAST CHARGE cycle, it only backs the charging current down to 1/5 of what it was when it started, then switches off in the same manner as the normal charge cycle. Once the charging current stops and the battery settles, you'll find that it's only actually charged to about 4.15v, giving you a nice margin of safety :-)

I've never had any overcharging problems with my particular Polimax unit, but the components they're made with are only to about 5 or 10% tolerance so there's likely be variation between units. I've never tested a battery I've charged with my Polimax and found a cell to be overcharged. It does on occasion let cells get to 4.21 during the charge/balance cycle, but I've never seen a battery settle on over 4.2


Oh, and one more tip, regarding the watt meter. Be sure to bench test your props with the ESC timing set to med and high, and compare.

[flydiver]

Dill, the low charge rate is clever to use the charger for a battery check. Never thought of that.

[ginginho]

Jun 2, 2010 6:38:25 GMT 1 flydiver said:

Dill, the low charge rate is clever to use the charger for a battery check. Never thought of that.

I tend to do this quite often, as the charger is the most accurate tool I have. Also worth doing prior to connecting multiples packs for a parallel charge to make sure one isn't a long way off of any others.

[john66]

Thanks for the suggestion dill.

John

[Dillzio]

Thanks fly. What is it they say? "wow, praise from Caesar"

Other than ringing my own bell, i wanted to advise John of a couple of simple mods to the polimax charger that make it a bit easier to use. First of all take the banana plugs that plug into the charger, and cut the crappy Tamiya connector from the end and replace it with a deans, that way your lipos can connect directly to the charger without going through any crappy connectors that may make the battery voltage read lower than it actually is. You can also connect a female deans to the tamiya plug you just cut off, so that you can still use the rest of the accessories that came with the charger.

Another thing that makes it a bit easier is to buy some 3s lipo wires/plugs from ebay like this one here, and solder a female plug to the end of the wires that go into the male plug to make yourself an extension cord for the balance plug. I just leave my extension lead plugged into the charger all the time. I find having 15cm to work with is much easier than 3cm. If you wanted to be a girl about it, I suppose you could just buy a 3s extension plug off ebay instead of making your own, but where's the fun in that? I used my extra plugs to make a parallel charging array.

The polimax charger (and most of the clones for that matter) also have a calibration function. You bring it up by holding down on (if buttons numbered left to right 1-4) buttons 2 and 4 while you're starting it up, then keep holding them until the calibration screen comes up. At this point it will show you the voltage of any battery you have connected to it, and you can adjust the calibration up or down and see what effect it has on the readout of the battery voltage. I have mine set to +2, which makes the voltage read .01v higher. Remember to adjust it up and not down, because you want it to think the battery is fuller than it actually is so that it doesn't risk overcharging it.

[john66]

Jun 2, 2010 13:05:42 GMT 1 Dillzio said:

First of all take the banana plugs that plug into the charger, and cut the crappy Tamiya connector from the end and replace it with a deans, that way your lipos can connect directly to the charger without going through any crappy connectors that may make the battery voltage read lower than it actually is. You can also connect a female deans to the tamiya plug you just cut off, so that you can still use the rest of the accessories that came with the charger.

Another thing that makes it a bit easier is to buy some 3s lipo wires/plugs from ebay like this one here, and solder a female plug to the end of the wires that go into the male plug to make yourself an extension cord for the balance plug. I just leave my extension lead plugged into the charger all the time. I find having 15cm to work with is much easier than 3cm. If you wanted to be a girl about it, I suppose you could just buy a 3s extension plug off ebay instead of making your own, but where's the fun in that? I used my extra plugs to make a parallel charging array.

The polimax charger (and most of the clones for that matter) also have a calibration function. You bring it up by holding down on (if buttons numbered left to right 1-4) buttons 2 and 4 while you're starting it up, then keep holding them until the calibration screen comes up. At this point it will show you the voltage of any battery you have connected to it, and you can adjust the calibration up or down and see what effect it has on the readout of the battery voltage. I have mine set to +2, which makes the voltage read .01v higher. Remember to adjust it up and not down, because you want it to think the battery is fuller than it actually is so that it doesn't risk overcharging it.

I put the deans on pretty much as soon as I got it out of the box. I havent added a deans to the tamiya yet for the other cables, though again nice idea.

Good idea on the balance lead extension it is a pain as short as it is.

I will definitely look at the calibration.

Thanks for the suggestions.

John