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Old Jan 28, 2005, 08:39 PM
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Melbourne, Victoria, Australia
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Multiplex 3s2p 4000 mah LiPo pack - charging/balancing?

I am new to LiPos and this is my first pack. I just went with a supplier's recommendation for a hotliner setup. I probably should have done some more research beforehand, but from what I can make out this is supposed to be a decent quality pack. It is rated at 50A discharge.

My question is whether I need to check individual cell voltage and do any 'balancing' as is recommended in certain threads on this forum? If so, this may be a problem as the battery is all sealed up in clear shrink wrap and I am unsure exactly where the cell +ve and -ve terminals are.

Does anyone else have experience with MPX LiPo packs like mine?

Another related issue is whether or not it needs to be slow charged initially. I have just discovered that the new charger I have just bought (Swallow Advance) has some limitations with LiPo charging and only puts in 1C if you want a full charge. Otherwise, you can set it to less but you have to keep restarting it. (E.g., if you set it to '400 mah' it will reportedly cut out after 400 mah has been put in, instead of charging at 0.4A until the pack is full.)

Thanks for any advice.

Anton
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Old Jan 28, 2005, 09:12 PM
Southern Pride
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Haralson County GA. USA
Joined Oct 2004
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Quote:
Originally Posted by AntonL
I am new to LiPos and this is my first pack. I just went with a supplier's recommendation for a hotliner setup. I probably should have done some more research beforehand, but from what I can make out this is supposed to be a decent quality pack. It is rated at 50A discharge.

My question is whether I need to check individual cell voltage and do any 'balancing' as is recommended in certain threads on this forum? If so, this may be a problem as the battery is all sealed up in clear shrink wrap and I am unsure exactly where the cell +ve and -ve terminals are.

Does anyone else have experience with MPX LiPo packs like mine?

Another related issue is whether or not it needs to be slow charged initially. I have just discovered that the new charger I have just bought (Swallow Advance) has some limitations with LiPo charging and only puts in 1C if you want a full charge. Otherwise, you can set it to less but you have to keep restarting it. (E.g., if you set it to '400 mah' it will reportedly cut out after 400 mah has been put in, instead of charging at 0.4A until the pack is full.)

Thanks for any advice.

Anton
Multiplex 3s2p 4000 mah LiPo pack -

If I were using this pack configuration in this stressful of an application I would have taps for checking and balancing cells.
Some Li Poly manufactures recomemd charging at 0.3C-0.7C. 1C is the maximum and it is believed that a lower rate will give better life and help prevent cell imbalnce. If you use balancers with every charge then cell imbalnce should not be an issue but you would have to have taps and balancers for this or charge each cell ,one at a time ,also requiring taps..
Some manufactures also advise limiting the maximum discharge to 70% of the cells maximum rated discharge rate for the first 3-15 cycles.
A hotliner is a very stressful application for Li Pollys.
In general the harder you push Li Polys both in charging and discharging the more likely they are to get out of balance.

Charles
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Old Jan 30, 2005, 05:00 PM
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Melbourne, Victoria, Australia
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Thanks for the info, Charles.

How might I go about installing taps into this pack? It is encased in a tough, clear shrinkwrap and I can't make out any +ve or -ve symbols on the terminals by looking through the sides at the circuit boards on the end of each cell.

Anton
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Old Jan 30, 2005, 07:28 PM
Southern Pride
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Haralson County GA. USA
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Quote:
Originally Posted by AntonL
Thanks for the info, Charles.

How might I go about installing taps into this pack? It is encased in a tough, clear shrinkwrap and I can't make out any +ve or -ve symbols on the terminals by looking through the sides at the circuit boards on the end of each cell.

Anton
Multiplex 3s2p

I do not know how the Multiplex packs are assembled. If they have a PCB
(Printed Circuit Board) for the cell(s) terminations and you know how to use a DVM and are good at soldering then it really is not a big deal. If the connection are just the cell tabs them self then you have to have a special flux and solder and it takes practice to get good at soldering to tabs without damaging the cells.Not a task which I recommend to those who ask how do you do it.

Charles
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Old Feb 01, 2005, 07:47 PM
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Yes, I have a DVM and can do basic soldering but I don't enjoy soldering.

Do you think it is possible that the little circuit boards between the cells are built-in balancers?

Anton
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Old Feb 01, 2005, 08:21 PM
Southern Pride
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Quote:
Originally Posted by AntonL
Yes, I have a DVM and can do basic soldering but I don't enjoy soldering.

Do you think it is possible that the little circuit boards between the cells are built-in balancers?

Anton
I went to their US site
http://www.multiplexusa.com/product_fs.htm
and did not see any balancers listed. They do have an over voltage protection device available but thes do not dalance cells, they just limit maximum voltage in case charger is set wrong(cell count).
My guess and it is only a guess is that the printed circuite boards are just used for cell terinations. E Tec and Kokams use these. The cells tabs( positive and negatives) go through slots are folded over and soldered to the lands on the board. This makes adding taps much easier (at least with mine were)as standard solder could be used. Many users use JTS connectors with leads (pig tails) to add taps. You need one for each cell normaly.Located each cells positive and negative contact point on the board(s) and attach leads. You will have to charge one cell at a time. Fastest/easiest way is to first series charge to 4.1 volts per cell and then set charger for single cell and finish charge each cell one at a time. Depending on your useage it may be only necessary to balance every 10 th cycle or so.

Charles
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Old Feb 01, 2005, 08:22 PM
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Most likely they are not. They are PCB's because of the copper on them and because the cells are soldered to them. The PCB is just a hookup for the cells in a Lipo pack, nothing more.

EDIT:
Charles you just beat me!
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Old Feb 01, 2005, 08:22 PM
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Melbourne, Victoria, Australia
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Quote:
Originally Posted by AntonL
Do you think it is possible that the little circuit boards between the cells are built-in balancers?
Actually, after closer inspection I can't make out any components on the boards so looks like they are just there to hold connections b/w cells...
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Old Feb 01, 2005, 08:26 PM
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Thanks for the info. I have a feeling they may be balanced to start with but I would like to find out. Sounds like it may be worth adding taps.

Quote:
Originally Posted by everydayflyer
You need one for each cell normaly.
So I need 6 for this pack (3s2p)?
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Old Feb 01, 2005, 08:47 PM
Southern Pride
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Haralson County GA. USA
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Quote:
Originally Posted by AntonL
Thanks for the info. I have a feeling they may be balanced to start with but I would like to find out. Sounds like it may be worth adding taps.

So I need 6 for this pack (3s2p)?
That's the math however I still do not know how that pack is assembled. If there are two packs of 3 cells each in series and then these two are connected in parallel then yess 6 taps . If the pack is made up of 3 pairs of paralled cells then you only will need 3 ,one for each pair of cells.
Large capacity Thunder Power packs are cells in parallel such as 2 each 2000 mAh for 4000 mAh capacity then 3 pairs in series for 11.1 volts. Apogee uses 3 2080 mAh in series for 11.1 volts then parallels these (end to end) for the 4160 mAh capacity.

Charles
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Last edited by everydayflyer; Feb 01, 2005 at 09:02 PM.
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Old Feb 01, 2005, 10:01 PM
antipodean recalcitrant
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I studied the pack for a bit, stripped off the labelling to get a better look, and determined that it is wired as a series of 3 pairs of parallel cells. I cut out some access holes in the shrink wrap and electrical tape and checked the voltages with the DVM.

As suspected, the cells appear to be balanced initially by the manufacturer, with each pair of cells reading 3.80V, giving 11.4V for the whole pack. Would I be safe to not worry about balancing for a while, assuming I treat the pack well?

Do you think it will be OK to use ordinary solder to attach 3 sets of tap wires to the solder blobs on the PCB boards?
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Last edited by AntonL; Feb 01, 2005 at 10:02 PM. Reason: typo
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Old Feb 01, 2005, 10:10 PM
Southern Pride
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Haralson County GA. USA
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Quote:
Originally Posted by AntonL
I studied the pack for a bit, stripped off the labelling to get a better look, and determined that it is wired as a series of 3 pairs of parallel cells. I cut out some access holes in the shrink wrap and electrical tape and checked the voltages with the DVM.

As suspected, the cells appear to be balanced initially by the manufacturer, with each pair of cells reading 3.80V, giving 11.4V for the whole pack. Would I be safe to not worry about balancing for a while, assuming I treat the pack well?

Do you think it will be OK to use ordinary solder to attach 3 sets of tap wires to the solder blobs on the PCB boards?
The best time to check cell balance is when they are close to fully charged.The only time to be concerned about out of balance on discharged cells is if they are 0.1 different. Yes I am sure they will be OK for a while and you atleast know how to check them . Regular solder should work fine or atleast it has for me on E tec packs with PCBs.

Charles
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