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 Post subject: battery chargers
PostPosted: Sun Aug 14, 2011 8:04 am 
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Joined: Wed Feb 04, 2009 4:56 am
Posts: 39
Hi everyone- sorry I have been out of circulation this summer- house painting/maintenance/vacation ect- anyway- I am looking for a good LIPO/nicad/nihidride? charger- would like to charge 2-4 batteries at a time, want to look ahead to when I might have an electric equivilant of a .40-.60 size plane with batteries to match for charging needs. Any suggestions/for sale? Thanks, Dennis Miller


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 Post subject: Re: battery chargers
PostPosted: Sun Aug 14, 2011 1:04 pm 
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Joined: Fri May 15, 2009 4:14 pm
Posts: 17
My personal experience has been with thunder power and Hyperion chargers. With the newer battery technology and higher recharge rates that they are able to withstand I would recommend a charger that has a minimum of 500w charging capability but personally I would go ahead and get one with 800 to 1000 watts. For a .40 to .60 size electric setup is normally a 5s or 6s (18.5v or 22.2v) so if you want to charge a pair of 5s 5000Mah at a 4C rate (20A ea) is approximately 800w but it would only take 15-20 minutes to charge. Keeping the cells balanced especially at the higher charge rates is crucial so the cell balancer needs to be up to the task as well. Also remember the power supply for the charger will need to be up to the task. The charging example above will require around 65A @ 12v and needs to maintain at least 11v under load to keep the charger from dropping off due to low input voltage. If you get a charger with a variable input voltage, usually 11 to 28 you can hook up 2 deep cycle batteries in series and eliminate the low input voltage issue and lower the input amperage as well. Try to look at the instruction manual for the charger as some chargers, Schultz as an example are extremely versatile and high quality but are more complicated than necessarywrong the average user
The wrong charger can shorten battery life or cause a battery to catch fire.

_________________
An aircraft is a 1000 parts flying in close formation.


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 Post subject: Re: battery chargers
PostPosted: Sun Aug 14, 2011 2:06 pm 
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Joined: Tue Jan 15, 2008 8:50 pm
Posts: 186
Dennis,

Here are my thoughts on the subject:

You don't want a charger that will charge less than 6 cell batteries and it would be better if you could charge 8 cell if you ever want to get a large airplane or heli. That said, chargers are rated in total overall watts and watts = volts x current as well as amps and cell count. Be careful to look at all three because you don't want to end up with a 6s charger that claims 10A charge rate, but really can't do it very well.

This charger: http://thunderpowerrc.com/html/TP610C.html Is a 6s charger that can charge at up to 10A, but it's max output power is 80 watts. If you take 80 watts and divide by 25v (6s battery nearing full charge) then you only get 3.2A.

Another thing to keep in mind is that the more charge rate you get the faster you can charge or the more packs you can charge at once. Lipo packs with the same cell count can be connected together in parallel and charged at the same. So if you had three 5s3300 packs, then you would need a 5 cell charger able to put out 10A in order to charge them at the 1C rate (1 hour charge). Rob points out that newer batteries can handle a 4C or even greater charge rate, so if you want to charge these batteries at 4c you would need 40 amps. That's over 800 watts!!!!

As far as which charger to get, I prefer the name brand chargers as I find that the quality and support is better. Safety is very important to me so I want my charger to double check everything I do. For this reason I like the FMA chargers. They will ask you to confirm that the battery is a lipo to prevent you from using the wrong settings which can cause a fire. They also don't have any provision to define the cell count, they force you to plug in the balance tap then the charger can see each cell.

I know this is a lot of information so here is the punch line:

Newer batteries can be charged very fast so your better off buying a nice high powered charger and two batteries, then buying a lot of batteries and a slow charger because you get a nicer/safer charger and you can fly continuously. I agree with Rob, don't get anything less than 800 watts, then be prepared to get a big power supply. I use old hp server power supplies and they work well.

To give you an idea how far this has come, I have a FMA power lab 8 charger, and I can charge every 3 and 4 cell pack I own from a 50% storage charge in the field in about 40 minutes.

schu


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