85 or 110 Ah battery for field cvharging?

[Dashik]

As per title. I'd like to get 6 to 8 charges of my 6s 5000mah lipos using my Cellpro 10s at the feild.

85Ah Leisure battery is a lot lighter and a bit cheaper than the 110Ah one. This makes it a lot easier to move in and out of the AA instruction car I drive. But its no use if it wont do the job.

So has anyone got a 85Ah battery and can they tell me if it can do 6 to 8 charges on a lipo as above?

Thanks

James

[xygax]

Ok...

Heres the techicnal bit...

6 cells x 4.2v / cell is 25.2v charging at 5 A (5000mAh C1) is 126W... Add aprox 20% for the efficency of the charger is a total of 150W for about 1 hour to charge a pack

so translate that into capacity required from a 12v battery

150 / 12 = 12.5A for an hour..... x 6 = 75Ah..... 0r x 8 = 100 Ah...

theres the maths it will work just as well for 5S... 6S 10S 12S ect... and give you Ah capacity.

Steve

[Dashik]

Ok cool so thats the 110 Ah one for 8 charges then ! Typical sods law lol.

OK I'll bite it and get one of those

[cjcj1949]

Do you have a link for the 85AH battery? Leisure batteries are'nt designed to give as many amps as car batteries. I remember someone complaining that they didn't give as much as they wanted. If you only want 12.5 amps I expect it would be ok. But low voltage stuff can be a pain. I remember our production manager rigging up a 12volt supply for our lights. Twelve volts went in one end but not much got to the other. Using your car battery backed up with a leisure battery might help. Depends how many batteries you charge at once and what C rating. Two at once at 3C would be about 70amps.

Might be worth asking when you buy it how low the volts will get at the current you want at the end of the day, and checking the minimum volts the cellpro 10 will work with. Or you could leave the car running.

[Kwickkwack]

Leisure batteries are able to cope with being run down further than automotive batteries, (one of the reasons they cost more) the question of amps wont be a problem, we sell leisure batteries into the marine market where they are used to start engines, and an 85ah battery will start diesel engines up to 200hp with no problem. i have read somewhere it is not a good idea to use a charger connected to a battery that is being charged, one of the reasons is that the input voltage may be too high. (can be 14.8v when charging from an alternator). I am sure someone with more knowledge than me will be able to add more detail.

[simon_t]

You won't have an 'amps' problem with either a car battery or a leisure battery - they are both capable of supplying hundreds of amps, at least for short periods. If you are charging you won't be drawing very much continuous current (10-12A in the case of a 6S 5Ah Lipo charged at 1C). You have rightly concentrated on the Amp Hour rating, which tells you how many charges you can make on a fully charged new battery - as indicated above, if you are charging 6S 5Ah Lipos, you will not get more than 4 or 5 charges out of an 85Ah leisure battery (I wouldn't take more than 50-60Ah out of it). So you need the bigger battery if you want more charges per session.

Simon

[Dashik]

Thanks guys. Too be honest I'm in the Electric heli side for the duration so I need a suitable sorce of power at the field. I dont know if there's a suitable safe adaptor to power the Cellpro 10s from the cars lighter socket but the Cellpro 10s can draw upto 28 amps continuous.........

An alternative that looks interesting is this generator,

IG1000 KIPOR SUITCASE DIGITAL PETROL GENERATOR SILENT

http://cgi.ebay.co.uk/IG1000-KIPOR-S...arms=72%3A1298


A couple of the guys at Fast lads use one and they reccommended it So just over twice the cost of a battery but all I have to do is chuck my home psu on it then run cellpro off that.

Looks like a long term solution......

[cjcj1949]

Amps problem

Cold cranking amps and longer term discharge are not the same. Neither is the voltage of any battery when it is full or nearly empty. The battery on charge in a car normally sits at 14 volt, but yes if a cellpro can't take 15 volts there could be a problem having the car running when a charger is connected. If in doubt look at the charger spec. Having a car battery at 14.8 means something is wrong either with the battery or the voltage regulator. Using the car's alternator was not meant to be taken seriously as you may as well put a proper motor in the heli.
There is a design tradeoff between different types of batteries depending on what you are trying to optimize. Either short term high current discharge or the ability to handle deep discharge. Using an ordinary car battery and a deep discharge one in parallel should give you the best of both worlds at no extra cost. I did say that 10 to 12 amps should be ok, but not necessarily 70amps. New types of lead acid come out all the time and you need to look at the specs to find one that will work.