I agree with that, all tests have proven the cells to be reliable in both heavies and feathers alike, stop messing about with tests and allow them already.
I agree with that, all tests have proven the cells to be reliable in both heavies and feathers alike, stop messing about with tests and allow them already.
From what Ive heard
Although you are correct the initial tests have been good, currently there is no commercial 10 cell balancer on the market.
You can get 7 cell balancers, but not 10, which is what people need before they start using them in the further tests.
I think everything is on hold at the moment until they are available.
On the weight issue.... remember that the only time when robots are really checked for weights is at Championship events. If the new rule does come about, then the new Ripper EVO will need to loose 4kg, as i see it, by 2009 when it would come in force, I would most probably go for A123s, saying that by 2009, i will most probably have built another 3 versions by then !
John
Roaming Robots
(Message edited by roamingrobots on November 19, 2007)
There are 14 cell balancers on the market (Schulze LipoProfibal14) as already reported in the lithium cell test thread.
(Message edited by leorcc on November 19, 2007)
Nobody holds it impossible to put 2 times 5 cell packs in series. It will take a bit more effort and chargers to recharge in a suitable time. But that is in effect the only restriction in creating high Volt and ampere packs, even within the current ruling of 7 cell packs.
Actualy, the only reason why somebody wont go to A123s is because the cost/benefit isnt big enough.
No use to replace the SLAs for £100 even £1000s of new batteries and chargers.
I find it a little anoying that we not only have to wait for the illusive commercial cell balancers. As Leo pointed out, they are here already. Apart from that, this holds back innovation as there are a lot of roboteers who are capable of implementing this themselves on a professional level.
What realy rattles my cage is that not only do we have to wait until they are available, we then have to wait until they are approved in the rules, which can take quite a while.
What id like to see is that we make rules based on what is acutally needed, not on what people are screaming on the forum. Most of the time this involves stating that there are no cell balancers for more then 7 cells, or that a certain speed controller has a cutoff voltage set to X which means that Y number of cells should be obligatory.
I propose the following, a lot of which is already in the rules as they are:
Rule:
- On lithium batteries, cell balancing is obligatory.
- On lithium battery packs, fuses rated at their peak maxiumum discharge current are obligatory.
- Using lithium batteries, All power electronics (motor drives, etc.) are obliged to have a cut-off voltage to prevent over-discharging of the batterypack.
For approval of the tech-check, the roboteer has to be able to produce the following:
- A datasheet of the cells in the batterypack
- A datasheet of the cell-balancer used
- The configuration settings used on the cell balancer and a wireing diagram.
- A datasheet of the charger used.
- The configuration of the charger and a wireing diagram.
- Datasheets of the powerelectronics used (motor drives, etc.)
- The configuration settings, specifically the cut-off voltage, and a wireing diagram.
If you are unsure that your system will be allowed on an event, gather the information you need for tech-checking and consult the event organizer.
Because battery technology changes very quickly there is no use for stating specific number of cells or voltages. In the end its up to the tech check to determine if its safe.
As there is always an issue with the maximum voltage 36V, it is up to the FRA to recommend a maximum number of cells for a specific technology, but only based on the maximum allowed voltage. That is the only limit that makes any sense to me.
This would translate in the following way, for maximum cells in series (based on nominal voltage): Pb: 18 cells, NiCd/NiMh: 30 cells, LiFePo: 11 cells.
Just my 2 Eurocents
It may also be a obligatory idea to have a separate, supervised charging area. Weve had one incident of a A123 leaking which involved the charging of an over-dischraged cell. Some HF escaped although the concentrations where very low.
maybe mr Trevor, or Mr Admin needs to create a seperate thread, or move it for this battery discussion.
John
i and jason wish the weight to stay the same please. its ok for all you rich bods to buy a123 but there are some of us that cant. and i will struggle to lose 2kg and jason even more.
Well put Shane..
Thanks for getting the thread back on topic Shane, and, as Jonno wrote the discussion of A123 batteries should move to another or its own thread.
Just one point on A123s, it is hard to vote - at the FRA meetings - on matters of safety when very few of us understand the technology. We are aware what can happen when it goes wrong so we have to err on the side of caution until someone can prove to us that it is safe.
Trev
PS I like Craigs suggestion.....
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