Charging my $8 Lithium Transmitter Battery

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Charging my $8 Lithium Transmitter Battery

Postby prong » Thu Jul 28, 2011 3:40 pm

I've just made my $8 lithium transmitter battery pack following Bruce's excellent guide. It works fine but I have a question about charging it. I'm using the Accucel 6 4 button balance charger, which I haven't used before. If I use the Lipo setting to charge it with a charging current of say 1 amp and a voltage of 7.4 volts, after a minute or so the charger beeps and gives a "battery disconnect" error. I've played around with the settings and if I drop the charging current down, to say 0.1 or 0.2 amps, I don't get the error but the charging times out (safety timer is set to 120 minutes).

It seems like these betteries don't like it when the charging voltage gets too far above the 7.4 volts which seems to happen with the high current setting. Is this because of the built-in over-voltage protection that Bruce talks about in the guide?

What's the best way to charge these things - quickly?
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Re: Charging my $8 Lithium Transmitter Battery

Postby John_Edward » Thu Jul 28, 2011 4:46 pm

I have the same problem, and I'm pretty sure you are correct.

Mine stopped charging with the error when the battery voltage got to ~7.85volts, but the cells were very unbalanced, 3.82 and 3.96 volts.
Doing an non-balanced charge might not work at all, as when one of the cells gets full, the charger will try to overcharge it, and the protection circuit kicks in.
I'm currently charging the cells individually with some alligator clips, and lets see if I get the connection error when the cell hits 4.2volts.

BTW, the protection circuits are 2.75volts and 4.2volts, so with our pack its going to cut out when the battery pack voltage hits 5.5.
Set your low battery alarms accordingly.

[EDIT]
Well, the protection circuit never engaged with a single cell, and after they were quite closely balanced, it charged quite a while until I got the connection error again.
It seems to be pretty clear now that doing a non-balanced full charge is pretty much impossible.
But it did end when the voltage showed 8.40V, so if the accucell-6 is accurate at all, it did charge the battery itself full.
Not sure about the individual cells.

Next up, probing the TGY 9x charging socket and doing some modifications to it...
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Re: Charging my $8 Lithium Transmitter Battery

Postby bmsweb » Fri Jul 29, 2011 10:26 am

I haven't received my Batteries (Which seem to be taking forever to get here), so I have no experience in charging these batteries. I plan on building mine with a balance connector also. So am I correct in that I should be able to do a 2S Lipo Balance Charge setting with these batteries?
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Re: Charging my $8 Lithium Transmitter Battery

Postby John_Edward » Fri Jul 29, 2011 2:15 pm

bmsweb wrote:I haven't received my Batteries (Which seem to be taking forever to get here), so I have no experience in charging these batteries. I plan on building mine with a balance connector also. So am I correct in that I should be able to do a 2S Lipo Balance Charge setting with these batteries?


Yup, normal balance charge works great :)
Just have to be careful with the connectors, the balance and TX power use the same plugs.
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Re: Charging my $8 Lithium Transmitter Battery

Postby RCModelReviews » Fri Jul 29, 2011 8:36 pm

I've been non-balance charging my pack for quite some time so decided to balance charge it the other day -- one cell took about 100mA more than the other. That's not bad at all.
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Re: Charging my $8 Lithium Transmitter Battery

Postby prong » Sun Jul 31, 2011 1:23 pm

I've attached a balance lead now but haven't charged it yet. I'll see how that works. Has anyone done anything to protect the leads connected to these batteries? e.g. like encasing the whole thing in shrink wrap like Bruce showed with his A123 receiver battery?
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Re: Charging my $8 Lithium Transmitter Battery

Postby Sid Sideslip » Sun Jul 31, 2011 10:08 pm

bmsweb wrote:I haven't received my Batteries (Which seem to be taking forever to get here), so I have no experience in charging these batteries. I plan on building mine with a balance connector also. So am I correct in that I should be able to do a 2S Lipo Balance Charge setting with these batteries?


Yeah, I've been waiting two weeks so far for mine to arrive.

I'm also going to wrap them in heat shrink and label the Tx power and balance leads
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Re: Charging my $8 Lithium Transmitter Battery

Postby bmsweb » Tue Aug 02, 2011 8:11 pm

RCModelReviews wrote:I've been non-balance charging my pack for quite some time so decided to balance charge it the other day -- one cell took about 100mA more than the other. That's not bad at all.


Just wondering what charge setting do you use on your pack when charging them?
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Re: Charging my $8 Lithium Transmitter Battery

Postby RCModelReviews » Tue Aug 02, 2011 8:18 pm

I charge mine at about 1.5A -- mainly because I usually recharge at the field. The charge rate will fall as the battery becomes charged and eventually it will drop to zero when the battery is fully charged.

Although I've never had any problems, it's worth doing a balance-charge every 5-6 normal charges, just to make sure that one cell doesn't get out of whack with the other.
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Re: Charging my $8 Lithium Transmitter Battery

Postby bmsweb » Tue Aug 02, 2011 8:35 pm

Thanks Bruce, I assume that's on the Lipo 2S setting. I got more than 6 hours last night and I ended up switching the radio off because it didn't seem to want to go flat :lol: Looks like I won't be needing to charge as often now. Its a great mod!
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