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Reformed Nitroaddict
08-02-2005, 10:07 PM
Had a question come up to me that I couldn't really answer, and it made me wonder, as I am looking into a larger electric project sometime in the future.

How do you charge batteries that exceed 12V?

For example, I was looking at a 4S2P pack. This pack needs to be charged to about 16.8V. Obviously I cannot use a charger that gets it's power supply from a 12V car battery. How about some of the more simple packs such as 12-15 cell nimh packs? How are those charged?

jrb
08-02-2005, 10:55 PM
You’ve probably noticed that 6/7 cell chargers (i.e. for RC Cars) are ½ the price of 8+ cell chargers; the genesis of the “7 cell trap” axiom.


The rest of the doe pays for the DC to DC converter needed to get the volts up!


I’ve got a 6/7 cell AAA NiMh charger that will do 8 when plugged into a vehicle that has its engine/charging system running – higher input volts.

Reformed Nitroaddict
08-02-2005, 10:57 PM
jrb - very interesting - so, the chargers that can charge at over 12V have some sort of step up circuit in the charger to boost the input voltage?

If this is the case - then which chargers on the market today can charger lipo packs of 4cells in series or more? When charging packs that are wired in parallel, do you need to charge each pack differently, or can you plug a 4S2P pack in with one plug and charge it all at once?

jrb
08-02-2005, 11:11 PM
Here’s a couple of photos of some of my fleet; my primary chargers are: an older AF 110D (up to 18 round cells), a Robbe Infinity II (32R), and a Schultze 330d that will do up to 11S.

In this article you’ll see one way around the 7 cell trap is to use multiples of 6 (or 7): http://www.rcgroups.com/links/index.php?id=4485 (http://www.rcgroups.com/links/index.php?id=4485) .

Red Scholefield
08-02-2005, 11:48 PM
jrb - very interesting - so, the chargers that can charge at over 12V have some sort of step up circuit in the charger to boost the input voltage?

If this is the case - then which chargers on the market today can charger lipo packs of 4cells in series or more? When charging packs that are wired in parallel, do you need to charge each pack differently, or can you plug a 4S2P pack in with one plug and charge it all at once?

Triton, Multiplex LN 5012, Orbit Microladen, Astro 109 (LiPo only), Robbe Infinity II (Ni-Cd/Ni-Mh/Pb), Orbit SuperNova(Ni-Cd/Ni-Mh/Pb), Dymond Super Turbo (Ni-Cd/Ni-Mh/Pb) to name just a few.

You can charge LiPos in parallel, but it is better to charge separately just to check balance of the cells in the series section occasionally.

Reformed Nitroaddict
08-03-2005, 12:15 AM
Red - The Astro 109 - Ive seen that charger - it will charge lipo cells of 4 or more in series?

Jason T
08-03-2005, 01:28 AM
I have the Astro 109 and the 112 Deluxe. Both are capable of charging over 12V. My 112D charges a 16 cell pack of Nimh on my field car battery no problems.

Jason

Red Scholefield
08-03-2005, 02:01 AM
Red - The Astro 109 - Ive seen that charger - it will charge lipo cells of 4 or more in series?

The Astro 109 will charge more LiPo cells in series than probably you or I can ever afford. :o How does 9 cells ring your bell? :cool:

ragbag
08-03-2005, 03:59 AM
Red mention the Multiplex LN 5012.

Has anyone seen that available on the market yet? I ahve an interest in that one and waiting for it to become available.
George
Gainesville Fl

Reformed Nitroaddict
08-03-2005, 02:26 PM
wow - very interesting. Does anyone have a link for the Astro charger?

Jason T
08-04-2005, 12:49 PM
This is where I bought mine. Atlanta Hobby has the details of each charger on the website.
This is the 109: http://www.atlantahobby.com/shopexd.asp?id=1007
and this is the 110: http://www.atlantahobby.com/shopexd.asp?id=530
and the 112D: http://www.atlantahobby.com/shopexd.asp?id=1002

Reformed Nitroaddict
08-04-2005, 02:29 PM
The only problem I see here is that the 109 only charges one pack at a time, is this correct?

I was also looking at the GP charger that does 4 at a time, but is only capable of charging up to 3S. Now I have to decide which is best for my needs, or maybe get both.

ekotil
08-04-2005, 04:48 PM
My Astro 109 does my 7s2p 5000mah Predator lipo in less than an hour @29+ volts. With lipos one at a time is all you need to charge because of safety considerations. Call Kirk at New Creations R/C in Willis, Tx., he has the 109's in stock.936-856-4630.

Matt Kirsch
08-04-2005, 06:26 PM
RNA,

That is correct, the 109 can only charge one pack at a time. You won't find a high-capacity charger that can do more than one at a time. From a cost standpoint, a dual-output 109 would cost nearly as much as two standard 109s. With both outputs going at full tilt, you'd need to make special provisions for power. Plus, when you blow an output, you're completely out of business while the charger is out being repaired. At least with two separate chargers you can still fly while one is in the shop...

Unbalanced prop
08-08-2005, 02:23 PM
Now I have to decide which is best for my needs, or maybe get both.

Get both!! I have toooo many chargers (or so my wife says) but then how many is too many. :rolleyes: I have the following chargers:

2 AF 109
1 AF 110D converted to a 109
1 Triton
1 TP 425
1 GP Polycharger 4
1 Duratrax ICE

Tweet
08-09-2005, 11:36 AM
I have two AF-109s and a Triton (which I mainly use to charge my transmitter). I can keep up with the glow guys without a ton of battery packs.

kermitdafrog
08-09-2005, 06:49 PM
Nitro,

A DC-DC converter can step up 12-volts to pretty much any voltage you want. (A good example is a 12-volt flourescent light). I have some solar powered Cisco radios (wireless access points) that operate from 48-volts, and I use a 12-volt battery and a 12 to 48 volts DC-DC converter to get the correct voltage.

Most field chargers that operate from 12-volts that are capable of charging 3SxP or 4SxP have the DC-DC converter already built into them.

Rick

Reformed Nitroaddict
08-09-2005, 07:10 PM
Thanks Rick - All this information has really helped.

stuff
08-09-2005, 09:16 PM
Using a RIGrunner 4005 I am able to charge up to 4 packs with triton chargers for each pack.I run these off the same 12cell deepcyle battery or power supply when home with a watt meter to monitor the amps. The runner is fuse protected and has sermos connectors.I plug my battery to the runner under a 40 amp fuse and then two tritons into plugs that have 25 amp fuses with another charger Fma at 10 amp fuse this leaves me with 5 amp and a 1amp to use my watt meter to monitor the amps so they wont be more than the power source. This is made byWest Moutain Radio.It sure cuts the charging time down from 1hour per pack to 3packs an hour. Stuff

Unbalanced prop
08-10-2005, 01:59 PM
I use the rigrunner 4005 also at the field and at home. Keeps everything organized and neat. Great little product as I can run up to five chargers off my field battery at the field or my power supply at home. And since one of the chargers is a GP 4 port charger, that could be eight batteries at once.:D

Doug

Daniel G
08-15-2005, 05:11 AM
My Triton can charge 24 volt gell-cells off of 12 volts. :cool:

SargentM
08-19-2005, 03:04 AM
More to the topic of how you charge things at greater than 12V: The charger uses step up circuitry to get the voltage to where you need it, But you can not get something for nothing. What else must change? THE CURRENT!

If you want to charge a battery that is 1.5 times the supply voltage, then the current that the charger draws from the power supply must be 1.5 times the current required to charge the battery.

For example, that 4S 16.8V battery. 16.8/12 is 1.4

Say we have a nice meaty 4S pack of 4000mah that we want to charge at 1C, we want 4A going to the battery so the current drawn from the charger supply needs to be 4x1.4 = 5.6A!

We will probably need yet a more current to run the chargers circuitry and to make up for losses in the power transformation. How much I dont know.

As you can see, if you were betting on your cheap 5A power supply being able to do these packs then you are out of luck!

Hope this helps.
Sarge.

Daniel G
08-19-2005, 07:31 AM
Of course, if you only charge at 2 amps then you won't have any problems. :)