need your help to achieve big battery and safely - Page 1
Forum section: electronics / projects

author: eevblogfan
author_rank: Frequent Contributor
timestamp: October 06, 2014, 03:20:36 pm
content: HelloSpecs :30AH and north72V pack , considering 144VProgramable BMS2Hr charging or faster if possiblebudgets:1K$ for the BMS1k$ for the chargerBattery budget is not marked yet due to considerations , cimestry, voltage rating , and weightThe final product is working system , no hazards and dameg for the cells (no abuse at all if possible )I need to discharg at 20 to 100A , 500A peaks ( less then 2 minuts)Have any one tried those Ev porpused BMS's for long period ? , i need good system so I can't buy good battery but low priced BMS .. and same goes for the charger . I must have balancer as part of the system , the battery and the BMS must be as low weight as possible , 30-40Kg is ok , but any higer then that and it would not work .If i need to post it in other thread/forum , please notify meSo far I am expecting to hear from you proper name(s) of product ,and read about and make my final choice , but I am also looking for "one solution" that has been tried for some period and can be suited for my specsAlso , 2000Cycles and above are requierd as much as reasonable to ask that .Thank you in advance

author: tonyarkles
author_rank: Regular Contributor
timestamp: October 06, 2014, 04:03:55 pm
content: Well, using hobby LiPos could probably get you pretty close. Using this one:http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16225you get 11.1V at 8Ah. To get close to your target voltage, you need 7 in series, and to get your Ah rating, you need 4 banks in parallel.Back of the envelope math gives: $44 * 7 * 4 = $1,232 for 77.7V @ 32Ah. If you can compromise on either the voltage or the capacity, you could get it under your $1,000 target (e.g. if you can do with 24Ah, you eliminate 7 batteries and get it down to $924)Charging that thing? Well, that's going to be a bit trickier... I have no idea what it'd take to do that safely. The packs are rated for 5C charging, which would be 40A charging current... That works out to ~440W/pack charging, if you're charging them as fast as you can ~= 12kW power while charging.

author: sacherjj
author_rank: Frequent Contributor
timestamp: October 06, 2014, 04:18:17 pm
content: LiFePO4 cells. Nominal 3.2V 3.0-3.6V range. These are replacing Lead Acid with 4 series cells. The supplier we are sourcing from are making little cells for us, but typically make monster cells for hybrid buses and the like. Has 30% less energy density than consumer LiCO type cells, but is safer and can last much longer with more abuse.10C-20C discharge is common with LiFePO4. So 500A, is a possibility. I know there are some that can handle 50C discharge.

author: TankaaKumawani
author_rank: Contributor
timestamp: October 08, 2014, 07:48:06 pm
content: 72*500A = 36kW, or about 47hp at peak, and 7.2kW (~9 hp or so) nominal. That's enough to propel a late-1960s Beetle...You'll be doing a lot with thermal management, that's for sure.

author: eevblogfan
author_rank: Frequent Contributor
timestamp: October 09, 2014, 08:42:24 am
content: Has anyone heard of "orion" -orionBMSI am planning to aquier the 24cell one , my question is for the quallity of the product as well as understanding what's inside ? , is it over rated ? , is it durable ? , remember , it's high energy mess ...The 72v*500A is not 100% dutiy cycle you know , it's more of A demand for assuring the battery won't be demaged when 100A+ is requierd , i know for sure i want that battery to last as much as possible , after 1 year , demanding 300A for 20 sec , won't be easy for battery rated at tops 300A peak , hence calculating the extreams here is not nisscesery at all , i need nominal 4-15Hp if it matters , but planning to use it for 2-3 years at least

author: Phoenix
author_rank: Frequent Contributor
timestamp: October 09, 2014, 10:20:08 am
content: http://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_problemsSome food for thought when considering management, packaging and handling...

author: sacherjj
author_rank: Frequent Contributor
timestamp: October 09, 2014, 02:32:56 pm
content: Quote from: Phoenix on October 09, 2014, 10:20:08 amThis is the worst part about the situation: "There is still concern that because the root cause of the fires were not identified, the solutions put in place by Boeing will not be able to cover the full range of possible failure modes."