Topic: Ultra lightweight batteries

[coverman]

Just been talking with a manufacturer of racing batteries for my competition cars .As an aside I learned that  they could custom make deep cycle lithium batteries with battery monitor systems , economic quantity 50 sets, at circa £200/set. They would need to know the running time desired, ie range, and the level of interest, to see if its a worthwhile project for them and us. 
As an example, a battery with half hour constant running time would weigh only between 1 and 2 kilos,. NB lithium baterries deliver the full voltage until they run out of curent, but their batteries do not experience thermal runaway.They will also endure very many cycles.

[Jonny]

interesting, what type of lithium batteries though?

[alexbromo]

Very interesting ! Modern LIFePo4 (litium polymer) are very efficent and lightweight.

I would want add a further hint: in the CZ (Prague) there is the european distributor of ThuderSky:

http://www.ev-power.eu/?p=productsMore&iProduct=302&sName=lp12v40ah-12v-40ah

they ship also only one piece, and in my opinion the prices are good (believe the sharp technology of these batteries).

They sells also the specific chargers and the accessories.

 

Alex Bromo

[coverman]

The starter batteries are lithium nano phosphate: whether the deep cycle type will be I don't know. The weight saving is great for energy saving handling, braking, or th possibility exists to greatly extend the range without exceeding the maximum permitted battery weight (but at some monetary cost for such a large lithium battery set)

[coverman]

Just looked on the Czech site, the 12V 40Ah battery is certainly well-priced. Is it though a deep cycle type suitable for our use? What about battery management and charging? I admit to not knowing much about battery management. My original need was for  lightweight starter batteries for my
competition cars and then I got talking to the manufacturer at
 www.racing-batteries.co.uk 
who said he could build deep discharge cyclic batteries specifically for C5 use.

[alexbromo]

I seen the site (www.racingbatteries.co.uk), the batteries proposed are of the same technology of Czech site: LIFePO4.

The problem is that these batteries of racingbatteries.co.uk are engeneered for start the motor of a racing car, so are imperative the weight and the max current in a very little time (only few seconds to start the engine).

Infact the stronger battery (http://racingbatteries.co.uk/index.php?option=com_content&view=article&id=50 priced £ 699) is only 13Ah.

With a battery like this on a C5, i guess you can run max. three / five miles max. 

Alex Bromo

[coverman]

No, you don't understand. Racing Batteries would be willing to build special cyclic batteries for us plus battery monitors, but they need a minimum order quantity of 50. These would be cheaper than starter batteries and they would be specifically for the C5

[alexbromo]

No, you don't understand. Racing Batteries would be willing to build special cyclic batteries for us plus battery monitors, but they need a minimum order quantity of 50. These would be cheaper than starter batteries and they would be specifically for the C5

Ok.

What capacity (Ah) battery they can build for £200, supposing we can find a total of 50 users interested in buying ?

For the deep cycle of the LIFePO4, i seen it is a manufacturer data: generally rated voltage is 12.8V, max charge voltage is 14.6V, cut-off voltage is 8V. The batteries needs a special charger with a pre-charge cycle and an automatic cut-off, to avoid damage. Futhermore also the discharge has to be controlled to avoid too deep discharge..

About this, the Czecs, for example,  allways proposes to buy this controller module (AKUMON) http://www.ev-power.eu/?p=productsMore&iProduct=336&sName=akm-a1-akumon with their batteries.

Alex Bromo

[Jonny]

most of us robot builders use A123 lifepo4, either buying them directly from a123 racing or getting them out of dewalt drill batteries. recently theres been some cheaper cells on the market:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16575

they work out about £5 a cell

[coverman]

They want to know what capacity we all settle on then they can quote a final price including the battery monitor. They build batteries that are charged by automotive on-board charging systems, so that should mean  hope that ordinary automatic car batery chargers should work.

[Lancealot]

May I suggest that a battery spec could include for utilising either quick release claps or the original C5 battery cover. This would then dictate the size and capacity of the battery. If they work out to be that light most would look at 2 batteries per C5.

thanks

Lance