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myxiplx · 11-28-2013, 10:58 AM

Hi folks,

I've got a Thunder Power 610 charger, but I'm not convinced it's properly charging some small LiPo cells I have for my night flying blades.

I believe this charger stops charging once it's gone to constant voltage mode, and has seen the charge current drop below 0.1A. This means I get a few minutes charge for these cells, not the 30-60 minutes that a full 1C charge should need.

I'm not at all convinced this is properly charging these little cells, is there any way to test that? Alternatively is there a better charger I could use, or can I modify the setup in some way to reduce current flow to the battery?

I'm no electrical engineer but I'm wondering if a resistor could be used to soak up some current, allowing the LiPo to charge at a slower rate, and hopefully top it up fully. Can anybody comment on whether that can be done safely?

Thanks all,

Myx

megawhacker · 11-28-2013, 11:22 AM

You do not need to be an electrical engineer to know you are not fully charging those cells.

1/10th C is a typical cutoff voltage for charging. It might vary from 1/3 C for a fast charge that somewhat undercharges to 1/20 C for a so called "accurate" charge.

100 ma is 2.5 C in a 40 mah cell.

You can do what I did and purchase a Cellpro product-PL 6 in my case which can be set to cut off as low as 5 ma.

You can do what I did before my PL6 purchase, and still do which is charge 1 S cells in parallel.

If you charge 25 of those batteries in parallel, that 100 ma cutoff is now 0.1 C and will appropriately charge your batteries.

This is not something I saw in any helifreak post, rather from trial and error. My Accucel-6 also cuts off at 100 ma. I charged many 200 to 300 mah mcpx batteries on it. I learned that an additional 45 mah per battery would go in after I started charging 6 or more in parallel with the same 100 ma cutoff. The 100 ma (0.5 C) cutoff was undercharging by 45 mah as compared to a 0.1C or less cutoff.

Cheap, high resistance charging leads probably aggravate the problem. My (small 1S batteries) charge much more accurately with one, thick, short lead from battery to charger than with 3 small gauge harnesses strung together.

I have to admit the PL 6 is a spendy solution for small 1S LiPos. However a week after the PL 6 purchase I made an impulse purchase at the 2013 Cali helifreak fun fly. The seller tossed into the deal four 6S 5000 mah batteries, two of which are Pulse ultra batteries rated at up to 5C charge.

11-28-2013, 10:58 AM	#1 (permalink)
myxiplx Registered Users Join Date: Apr 2013	Charging very small LiPo cells (40mAh) Hi folks, I've got a Thunder Power 610 charger, but I'm not convinced it's properly charging some small LiPo cells I have for my night flying blades. I believe this charger stops charging once it's gone to constant voltage mode, and has seen the charge current drop below 0.1A. This means I get a few minutes charge for these cells, not the 30-60 minutes that a full 1C charge should need. I'm not at all convinced this is properly charging these little cells, is there any way to test that? Alternatively is there a better charger I could use, or can I modify the setup in some way to reduce current flow to the battery? I'm no electrical engineer but I'm wondering if a resistor could be used to soak up some current, allowing the LiPo to charge at a slower rate, and hopefully top it up fully. Can anybody comment on whether that can be done safely? Thanks all, Myx __________________ Helis: Oxy 4 Max (day + night), Gaui X3 380, Oxy2 FE 215, Oxy2 Sport 190 Radio & FBL: Spartan Vortex, MSH Brain, Jeti DS-14, Spektrum DX8G2 Sims: RealFlight & AccuRC

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11-28-2013, 11:22 AM	#2 (permalink)
megawhacker Registered Users Join Date: Apr 2011	You do not need to be an electrical engineer to know you are not fully charging those cells. 1/10th C is a typical cutoff voltage for charging. It might vary from 1/3 C for a fast charge that somewhat undercharges to 1/20 C for a so called "accurate" charge. 100 ma is 2.5 C in a 40 mah cell. You can do what I did and purchase a Cellpro product-PL 6 in my case which can be set to cut off as low as 5 ma. You can do what I did before my PL6 purchase, and still do which is charge 1 S cells in parallel. If you charge 25 of those batteries in parallel, that 100 ma cutoff is now 0.1 C and will appropriately charge your batteries. This is not something I saw in any helifreak post, rather from trial and error. My Accucel-6 also cuts off at 100 ma. I charged many 200 to 300 mah mcpx batteries on it. I learned that an additional 45 mah per battery would go in after I started charging 6 or more in parallel with the same 100 ma cutoff. The 100 ma (0.5 C) cutoff was undercharging by 45 mah as compared to a 0.1C or less cutoff. Cheap, high resistance charging leads probably aggravate the problem. My (small 1S batteries) charge much more accurately with one, thick, short lead from battery to charger than with 3 small gauge harnesses strung together. I have to admit the PL 6 is a spendy solution for small 1S LiPos. However a week after the PL 6 purchase I made an impulse purchase at the 2013 Cali helifreak fun fly. The seller tossed into the deal four 6S 5000 mah batteries, two of which are Pulse ultra batteries rated at up to 5C charge.

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