Can I charge 3 Cell Lipo from a 12V 7Ah bat?

I have a feeling that his source battery voltage drops to the point that it can only deliver 20ma. My charger stops charging if the current goes below 100ma.

My cheapo celectra lipo charger step the voltage up, it only sto
charging when my gel-cell drop near 10V. I always use gel-cell, sinc I get them at my job for free
-- Hugeon ----------------------------------------------------------------------- Hugeone's Profile: http://www.rcgroups.com/forums/member.php?action=getinfo&useridR29 View this thread: http://www.rcgroups.com/forums/showthread.php?threadid7665

It depends on the charger. Some, like the AstroFlight 109D will step up the voltage; most simple ones will not. In fact, they lose a little voltage.
As far as ampere hours go, You probably won't ever get more than 3 charges, and it might be hard on the battery.
There is a battery made for wheelchairs that is about 30 AH. It is designed for deep cycling.
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Your gel cell doesn't have enough poop. Go buy yourself a garden tractor battery at your local auto parts store. They're only about $18! That's what I use and it's good for all weekend and then some before it needs to be charged.
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Are these garden tractor bats still only 12v?
...Im begining to thing I might need 18v and was thinking of buying 3x 6V10Ah bats from Maplin (£9 each) and wiring them in serial to give me 18V and 30Ah.(enough for several charges of my 1600mAh packs)
Does anyone know where I can buy an 18v battery with decent Ah for less that £27?
Thanks
David Bevan http://www.davidbevan.co.uk

| >Your gel cell doesn't have enough poop. Go buy yourself a garden tractor | >battery at your local auto parts store. They're only about $18! That's what | >I use and it's good for all weekend and then some before it needs to be | >charged.
The problem with that idea is that they're not deep cycle batteries -- they won't last long if discharged repeatedly.
| Are these garden tractor bats still only 12v?
Well, 12 to 13 volts or so, depending on the state of charge.
| ...Im begining to thing I might need 18v and was thinking of buying 3x | 6V10Ah bats from Maplin (£9 each) and wiring them in serial to give me | 18V and 30Ah.(enough for several charges of my 1600mAh packs)
Why not just get a charger that can bump up the voltage as needed? There's many to choose from, and the cheaper models aren't that expensive.
There's also a very good chance that hooking up your charger designed for 12-14 volts to an 18-21 volt power source will fry it.
| Does anyone know where I can buy an 18v battery with decent Ah for less | that £27?
12v batteries are so much easier to find, you ought to just get a better charger ...

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WOuldn't it still be 10Ah? mk

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...er I had a think about this and I think the Ah would add as the current will be shared across all three bats? ie to chage at 1.6A each bat would be 0.53A (ie 1/3 of total current)
...or would it be 1.6A per pack? Youve got me thinking now!
David Bevan http://www.davidbevan.co.uk

snipped-for-privacy@davidbevan.co.uk wrote:
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...had a bit more of a think and 3 batts in series would not add their Ah, but would add their voltage. 3 batts in parrallel would add their current (and so add Ah), but not their voltage.
So, not a lot of point in getting the batts from Maplin! What chargers do people recommend? Ideally I want to beable to charge 4 batts at a time since this will allow almost continous flying.
Regards
David Bevan

Look at the new Tower Hobbies 4 battery charger. It will only do about 2A per battery, but it allows you to charge 4 at a time.

The lithium only one? mk
wrote:
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Yea, the one that isn't available yet!

On Fri, 03 Jun 2005 02:42:58 -0700, junk1 wrote:
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Great Planes has a 4 port Lipo charger than can charge 4 cell lipos. Just what you want.
I have no experience with it, but the people at the rcgroups website that have one seem pleased. Obviously to charge that many batteries you are going to need a good source of 12v power, either a good battery or a beefy power supply.

Which charger do they have? The latest one they advertise isn't available until June now.

On Sat, 04 Jun 2005 00:36:38 +0100, Paul McIntosh wrote:
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Great Planes PolyCharge4 DC Only 4 Output LiPo Charger
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXKAU0&P=ML
This charger was available earlier, but the initial stock must have sold out or those guys on rcgroups picked one up at their local hobby shop.

That's the one I was talking about. I asked them when it will be available and they keep saying a month later (since April)

On 3 Jun 2005 02:42:58 -0700, snipped-for-privacy@davidbevan.co.uk wrote:
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If you're doing only Lipoly the Astro Flight 109 D is one of the best out there. It ONLY charges Lipoly. The LCD display is lighted ,tells how many cells are in the pack you're charging , the charge rate , voltage , time , and how many amps you put into the pack. Kinda like filling up at the gas pumps. You know how much you used during your last flight. It auto detects how many cells are in the pack (s) you are charging. It only has ONE adjustment and that is the rate of charge in amps. It's as near foolproof as any I have seen. I like that part LOL
I charge 5 3 cell 1500 ma packs regularly. It will do more but thats the most I have charged. I love this charger and would highly recommend it.
I also have a Triton which does every battery under the sun. For all around use it's a very good charger. It's fully programmable for charge rate , discharge rate, charge voltage cut off and discharge voltage cut off. Even the Melody to signal when charging is done has about 10 selections. I would recommend this for all around use as I;m sure many here would also.
I have other chargers , Tekin , Pro Tech and a Hobbico field charger. FWIW , Astro Flight and Triton are my favorites. I use either my car battery or an old AT PC power supply ( 8 amps) for a power source.
Ken Day

| So, not a lot of point in getting the batts from Maplin! What chargers | do people recommend? Ideally I want to beable to charge 4 batts at a | time since this will allow almost continous flying.
In theory you could charge 4 LiPo packs in parallel off the same charger if 1) they're all the same number of cells (this is vital!) and 2) are all at approximately the same voltage/charge level when you start. Ideally all the packs involved would be identical, but this isn't absolutely essential.
However, there are some dangers. Violating #1 will almost certainly destroy at least one battery and could cause easily a fire. Violating #2 will cause high currents to flow if the voltages are signifigantly different, and this could destroy a battery or start a fire as well.
Beyond that, there's also a danger that a battery pack with a much lower internal resistance will get most of the charging and so you could charge it at too high of a rate ...
So I would not suggest trying this unless you know what you're doing and understand the dangers.
You can also charge two or more NiCd/NiMH packs on one charger by putting them in series, but similar dangers/concerns exist. Again, don't do it unless you understand what you're doing.
Personally, I have two Triton chargers. Usually one stays in my car and one in my garage, but they are portable, and if I think I'll be doing a lot of charging at the field, they'll both go with me. Having two chargers and at least three battery packs and somebody to talk to usually means I can fly all I want, and yak about flying in between flying ...

On 2 Jun 2005 06:30:37 -0700, snipped-for-privacy@davidbevan.co.uk wrote:
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If you connect three 6 volt 10 amp batteries in series you will get 18 volts but you will still only have 10 amps. If connected in parallel you will have 30 amps but only 6 volts.
You can get NO more out than you put into it.
Ken Day