How to use wattsup meter for charging lipo

[mikejbb]

I just rec'd my wattsup power meter and now can say that my battery, exc, and prop combination is fine. I will test to see if it is optimal later this week, but the amp draw is within all 3's ratings, no problem.

So when I went to meter the charging of the 3c lipo, I just looked at it dumbfounded. I made male/male and female/female adapters so I could put the source as the charger and load as the battery. Well I connected the load side to the battery and got volts, great! But how to get amps. The balancing charger connects to each cell seperately. So do I have to measure each cell charging seperately?

I read the online manual and it indicates I will have to test each cell separately. Oh what fun. I'll have to modify the balancing lead to put in some deans on each cell, right?

Hope it's easier. Please help.

I have the hextronics balancing charger www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=2055

Mike

[mrmugen]

When the info flashes on the screen look for Ah. This is your capacity. You will not be able to check each cell alone with this meter. Simply plug it inbetween your pack and charger and watch the Ah increase. Move the decimal over 3 places and you got mah. It is quite accurate. 1.472Ah =1472mah

Kevin

[flyinghigh]

So what all can this meter do? I'm looking for an all around good meter.

Nevermind, I found a good article here : www.rcuniverse.com/magazine/article_display.cfm?article_id=468

[flydiver]

Found a problem with that Hextronic charger. If a balance wire breaks it'll charge 2 cells happily anyway without any notification. Next flight drains all 3 and one cell gets hosed. Big problem if using Loong Max batteries where the balance taps break easily.

You can't use the wattmeter for amp input on a balance charger unless you rig up something between the power supply and charger. It'll still be off a bit since the charger will use some itself to work.

fly

[mikejbb]

I soldered deans to the ground and to one of the cell outputs from the hextronics charger and got good readings for the one cell for a while. About .75 amps charging the one cell when the hextronics was set to 2 amps. The other 2 cells were also charging ok.

Then a funny thing happenned on the way to the airfield. The deans connector on the charger side just lost connection in the hot lead. Wierd. As it turns out, if the deans is pushed in half way, it works fine. But when you push them together the circuit breaks! Oh well, I'll solder another on. Mayby I got it too hot. I'll be more carefull this time.

Deans 1 me 0

So fly, I simulated a wire break with a bad deans connector and yes the other 2 cells kept charging. But I stopped it immediately and put my other set of wires in and the charging continued good as usual.

Mike

[mikejbb]

As it turns out I lucked out by attaching my deans to the red and black leads, the 2 end pins of the balancing tap. That intercepts the charging power and connects the wattsup to the whole pack during charging, not just one cell. That's why it shows 12+v when charging. If you want to measure one cell during charging, then you have to put the wattsup between 2 adjecent wires in the balancing tap, haven't figured out how to do that easily yet.

Here's a link to a wiring diagram of a 4S lipo. eflight.hedlunds.net/bilder/koppling.jpg

And some charger diagrams www.rcgroups.com/forums/attachment.php?attachmentid=674349

Mike

[mikejbb]

Using wattsup, I've watched the numbers for my hextronic charger and when the battery is at it lowest power just after flying, the charger charges at 1.52amps on the 2amp setting. Not too bad. It drops down to .5amps as it approaches shut off voltage. But that's within 10 minutes of shut off. So reports of the hextronics not really charging at 2amps were exagerated. It's not that bad. The 1.52amps is the standard rate to charge after many readings. Just to be sure, the wattsup is between the charger and the balancing tap, but connected to the 2 outside pins. Therefore it is measuring the entire pack during charging, not one cell.

Mike

[mrmugen]

What pack are you charging at 2 amp? Or should I say 1.52?

[SCC]

Hi Mike.
I have just got myself a wattsup and i'm looking forward to using it.

[mikejbb]

May 9, 2008 19:21:44 GMT 1 mrmugen said:

What pack are you charging at 2 amp? Or should I say 1.52?

It's a "Mystery" 2400mah.

cgi.ebay.com/2x-2400mAh-15C-11-1v-LiPo-Li-Po-Rechargeable-Battery-RC_W0QQitemZ360049832875QQihZ023QQcategoryZ34056QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

The last charge was at 1.79a. I did get 20 min's from the pack the first few flights with stock engine, but now it's about 10mins with brushless. Volts drop to 11, and recharge is only 1400mah. At 11 volts the sc can't fly. So I'm gonna test props next to see how that works.

Any other thoughts of why 11v doesn't keep her up. I've read that 3.2 is a better lvc anyway and at 11v thats 3.67v so a ways to go. She spins good, but just not with much force, won't even taxi on rough grass.

This is the motor: www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5112

Maybe bad battery?

Mike

[duck9191]

i have some 12c mystery 2400's and they are over rated. 20 amps and they sag to about 10.5-11 volts. but since i like to cruise with my cub at half throttle (still moves though with the brushless) i can get about 25 min of flight. when i cycled the batteries with my duratax ice i found that the capacity is only really about 2150 mah, and they are only about 8c but for $20 something dollars they arnt too bad.

what prop are you using? the suggested is only 8x3 to 8x5 but i would try a 9x6 if you are still using the stock prop just make sure it doesn't get too hot. 11 volts is ok under load, and should deffintally keep ya in the air.

also is the prop on the right way, and is the motor spinning the correct way? that will give you problems lol i know. i madined a plane with the prop on backwards and it wasn't good.

[mrmugen]

That motor is simply not enough I am afraid. I doubt the battery is shot.

Kevin

[mikejbb]

Since this it a chargers forum, I'm going to continue this discussion with a new post in the motors forum because I need more info.

mrmugen, please go there in a few minutes.

Mike

[flydiver]

May 9, 2008 19:16:10 GMT 1 mikejbb said:

So reports of the hextronics not really charging at 2amps were exagerated.
Mike

You mean this posting?

>>
Setting Actual
0.5A 0.2A
1.0A 0.68A
1.5A 1.1A
2.0A 1.32A

That's why it takes so long. It also does not charge 100%, more like 93%. This does NOT hurt the battery, probably better for it in the long run but it does ding performance a tad.
<<

To get the above data I used a 7A switched power supply and put the wattmeter in line using an adapter so I could use the balance port to charge.
The Hex 0808 was placed in 'serial' charge mode. This data was gathered on 3 separate chargers. None were remotely close to spec. All were fairly close to the numbers above.

For the price it is a decent charger but don't delude yourself about it's limitations. My buddy just hosed an 1800 3s because he used that charger on it while one of the balance tap wires was broken. Since the plane he flies is a slow flier he didn't notice the power loss until one cell was completely dead. Puff goes the Loong Max.

1 dead lipo + cost of a Hextronic charger = FMA Cellpro cost
Problem never would have happened. He won't put ANY lipo on that charger now without checking it on the FMA first.

Are you sure all the balance wires on your lipo are intact?

fly