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› Charge times with Gen PS on 6s 5000
01-23-2013 08:44 PM  4 years agoPost 1
Marcus24

rrNovice

Manchester, TN

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Hey guys I need some help. I am trying to get a estimate on charge time with the following equipment.
Yamaha 2000 watt Gen (1600 cont)
2x dell 6650 server power supplies (24V, 1800 watt, 72amp)
2x Icharger 3110B
I will run both chargers at the same time and will be charging 2 packs in parallel off each charger.
I would like for someone to check my math.

Icharger can only charge 6s packs at 756 watts do to
Watts= 25.2V*30amps
Taking account for charger efficiencies
756 / .8 = 945watts from PS
Taking account for power supply efficiencies
945 / .8 = 1181 watts from generator

So 1181 watts from generator will allow me to run one icharger at max capacity while charging 6s lipos.

But what if I run two chargers. Accounting for the loss in the power supplies, 1600 watts of continueus power should provide 1280 watts input to the chargers now accounting for loss in the chargers there is 1024 watts available for charging.

1024 watts / 25.2V = 40 amps

This will allow me to run both chargers at 20 Amps when charging 6s lipos.

Finally two questions.
1. How quickly (meaning time in minutes) will I be able to charge?
2. Should I run two chargers at 20 amps or one at 30 amps?

Thanks guys I know this is a long post with a lot to it.

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01-23-2013 09:21 PM  4 years agoPost 2
Wynn1427

rrApprentice

Ca. 93612

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Your math does make sense. I am not sure that you would need to increase the watts calculation based on efficiency of the generator since the spec. already says it can provide 1600watts continuous (output efficiency has already been tested here). I would tend to take efficiency loss factor in charger and power supply to be about 0.85.

Based on my quick estimate it would be (1600 * .85) / 2 = 680watts per charger and chage rate of 26amps for each charger.

- I always take the full pack capacity to figure time since the CV and balancing at the end of the charge can take some time depending on the health of a pack. So take a pack capacity 5amp-hr / 26amp = .19hr * 60 = 11.5min for each battery.
- Only thing I can think about running the two at different currents is that when one charger starts its CV stage and draws less power the power supply voltage should rise. Just don't know how tolerant these charges are to a voltage increase. I understand the voltage increase is over a period of time so it might be fine. Maybe someone else can shed some light on this aspect of multiple chargers on a single power supply.

Wynn

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01-23-2013 10:10 PM  4 years agoPost 3
AWittleWabbit

rrElite Veteran

O.C., CA

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There's a good entry by Tyler in the Honda generator thread about staggering the charging so both chargers aren't drawing peak current. It might be of interest to you.

Heli-itis sufferer.

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01-24-2013 12:05 AM  4 years agoPost 4
Marcus24

rrNovice

Manchester, TN

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Thanks guys so it sounds like the best I can do with that setup is about 26amps per a charger. Thank you for checking my math this stuff can get confusing the first time around. I am working on making the switch from nitro to electric and am trying to get ahead of the learning curve.

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