pyramid power supply

[FALOPZ]

newbie need help:

planing to go bigger to eraptor son i want to buy a power supply just once, one that can charge to lipos (big ones) with 2 chargers...

people told me to buy pyramid, but i dont know how many amps its the optimum.......some people say 20 its ok some say at least 35.

someone can help me?

[jrohland]

I just got this (http://cgi.ebay.com/Tekpower-13-8V-12V-30A-Linear-DC-Regulated-Power-Supply_W0QQitemZ190047227879QQihZ009QQcategoryZ582 86QQssPageNameZWDVWQQrdZ1QQcmdZViewItem) one. I am trying it today for the first time.

I plan to charge two 5 cell packs together using two TP-1010C chargers. The maximum amps the 1010 charger can deliver to the pack is 10 amps. Since a 5 cell pack needs 18.5 volts, each charger will need to pull a maximum of 15.4 amps. As such my 30 amp power supply is just slightly to small but, the 50 amp is much more expensive.

How did I get 15.4 amps?
18.5 volts / 12 volts x 10 amps = 15.4 amps.

You see the power supply delivers 12 volts. The battery pack needs 18.5 volts. So, the charger needs to pull the delivered amps times 1.54 or 15.4 amps.

jrohland

[FALOPZ]

so 30 its not enough?

[jrohland]

If you have the funds, get a 50 amp. If not, 30 or 35 will work. 20 amps is too small.

The eRaptor should use two 5 cell packs wired in series. So it would be 10s1p. If you plan to run a single 10s pack (not recommended) you will need a LARGE charger.

For example; Say you get a 10 cell pack rated at 4900MAH and, that pack can be charged at 3C, the charger will need to deliver 14.7 amps. Since your power supply will likely be a 12 volt unit, the charger will need to pull 45.32 amps. So, a 50 amp supply will work.

Hope that answers your question.

jrohland

[kgfly]

Those amperage calculations are right as far as they go but do not allow for the losses in the system. Assuming the charger is 90% efficient then your example becomes (2 x 15.4 / 0.9) = 34A and (3 x 4.9 x 37)/(0.9 x 12) = 50.36A

Many of the bench power supplies are 13.8V which help, bringing the example currents down to about 30A and 43A.

Continuously running a power supply close to or above its maximum rated capacity will almost certainly reduce its lifetime significantly. If you know you want to be able to charge 2 batteries in parallel AND have a power supply suitable for larger batteries in the future, get at least a 50A unit.

[Clintstone]

Capable of being charged 3 c and actually being practical to charge 3 c can be 2 different things. I normally charge at 1 c and I am charging 10 s ( 2 x 5s1p ) and by the time I am ready to start the second charger it has ramped down and is ready to pump the second set. I feel the life of the packs are extended when used this way. If you get in a hurry then pump them but as far as a regular practice I don't recomend cutting the life of the pack without accepting the cosiquences. I have charged the big packs fast but I normally charge at the 1 c rating . I am using a 20 or 25 amp power supply and it works fine. I have a diesel truck with 2 big batterries and I like charging off of them as they put out good power without running the truck. I hope this helps.

[FALOPZ]

ur really taling chineese to me...im newbie, just flying trex 450 for the moment,,,but planing to go bigger soon, just need advice in amps i need to buy p supply just once,,,,,,,i dont think ill charge more tha two batteries at same time.....

[jrohland]

ur really taling chineese to me...im newbie, just flying trex 450 for the moment,,,but planing to go bigger soon, just need advice in amps i need to buy p supply just once,,,,,,,i dont think ill charge more tha two batteries at same time.....You need a 50 amp 12 to 14 volt dc power supply. If that is beyond your budget, get the most amps you can. Don't get less than 7 amps.

jrohland

[FALOPZ]

i got good offer here in my country,,,,13.8v 40 amp....litlle expensive.....like 200$

[Clintstone]

buy once within your budget I agree. The 25 is $100............at radio shack, but it works good for what I am doing. Good luck and let us know what you do.

[jrohland]

i got good offer here in my country,,,,13.8v 40 amp....litlle expensive.....like 200$That unit should work for any forseeable charging needs. Get that and you can check DC power supply off your list of needs for quite some time.

jrohland

[FALOPZ]

THANKS FOR ALL FRIENDS,,,ILL KEEP POSTED,,,,NOW MY BLADE CP 4-1 UNIT ALMOST GONE.....WENT CRAZY.....