CALB CA series cell performances

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Beemer
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Re: CALB CA series cell performances

Postby Beemer » Tue Jul 17, 2012 9:18 pm

Errr, next year they did not wear Cedrics boards,

GregsGarage
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Re: CALB CA series cell performances

Postby GregsGarage » Tue Jul 17, 2012 9:30 pm

Beemer wrote:JR needs no BMS. He has an indicator to say his pack is low by counting the AH.
His charger simply does not overcharge.

If he needs to get off the highway AFTER his indicator has cut the controller; all he has to do is press two buttons together and he can still drive it until there is no power left to drive the car... They simmer down as one. No busted cells!

What's he have to be a human BMS for?


Cedric reported in the latest BVR that he has just tested the capacity on his 7 year old thundersky pack. It still has 90% of its new capacity and because of the way his cell protectors work the pack is virtually indestructible. No funny buttons to press and risk damaging the pack. With the cell protectors they gradually start to reduce power as the pack depletes. When the pack is empty the vehicle won't move. You can leave the pack like that for months without damaging it due to the very low drain of the cell protectors and then recharge it, again his cell protectors will control charger, top balance and prevent any cell getting over charged. You always have the risk with JR's vehicle that someone can press the buttons and then drive too far, ruining the pack. Cedric's bms, properly installed will never let you drive a pack to destruction. That should be the goal of every bms. 7 years, 90% capacity and these are the old LCP cells that have a supposed inferior life to the latest cells. :shock: Beat that! :mrgreen: :mrgreen: :mrgreen:
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

Beemer
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Re: CALB CA series cell performances

Postby Beemer » Tue Jul 17, 2012 9:57 pm

Li cells are stable if nothing depletes them. you know this.

No matter what JR does with his pack it is very, very difficult to wreck them. He HAS run them down to the point where the car had to be pushed into the garage the last few feet. Matt Hauber driving Speedster uno for range; an extra 20 miles or so. No damage due to being bottom balanced.

Oh, he also done the same thing with the van. 100 miles at its top speed of 25mph. Crawled back in with barely any power. Still no damage, no BMS no low voltage issues.

Beat that :mrgreen: :mrgreen: :mrgreen:

GregsGarage
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Re: CALB CA series cell performances

Postby GregsGarage » Tue Jul 17, 2012 10:16 pm

Just have to compare notes again in a few years. :D
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

Beemer
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Re: CALB CA series cell performances

Postby Beemer » Tue Jul 17, 2012 11:03 pm

mid 2009 to mid 2012.. How many is that? :D

GregsGarage
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Re: CALB CA series cell performances

Postby GregsGarage » Wed Jul 18, 2012 9:01 am

Less than 7.

I have no problem with people advocating JR's ideas. I have never said they wouldn't work, but I am not a fan of them. However, when you claim "Top balanced packs suffer from the BMS cutting the power because the whole pack shows a low voltage condition under load as if its going empty.... This happens while accelerating and it still has plenty of charge in it. What good is that? There is no way over this unless its bottom balanced..." I have to take exception. There are many top balanced bms systems in use, they work fine, have done for many years, have taken first place finishes in racing and have stood the test of time. Cedric's report of 90% capacity after 7 years shows how successful and effective these systems can be. That's the bench mark, lets compare notes when one of JR's packs gets there, I am interested in seeing how they compare.
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

mikethebike3
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Location: NE Norfolk, UK

Re: CALB CA series cell performances

Postby mikethebike3 » Wed Jul 18, 2012 9:04 am

So, to BMS or not to BMS, is that the question? :shock:

However, interesting and important though this discussion is, the fact remains that Calb require active battery management.

The main warranty document states the warranty is for "18 months after deliver with free exchange of the cells and additional 18 month 50% if a high class battery monitoring and balance system is used." Their "Technical Requirements for Battery Charging & Discharging" reads like the technical spec of a BMS, with requirements that the BMS monitor and react to both cell voltage and temperature during both charge and discharge. It may not be totally comprehensive, but you can't fault them for making their requirements clear.

So unless Calb can be persuaded to relax their warranty requirements, I'm stuck with it, BMS is required. I'm sure that many, Jack Rickard in particular, will feel they know better (and probably do, as a newbie I can't judge), but if I'm to invest pushing £7K of my hard earned cash in a set of batteries I sure as hell want to know that there's backup if things don't work out! Once the warranty period is up I can do what I like, but by then I'll be experienced too. :lol:

Mike

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Re: CALB CA series cell performances

Postby GregsGarage » Wed Jul 18, 2012 9:11 am

mikethebike3 wrote:Their "Technical Requirements for Battery Charging & Discharging" reads like the technical spec of a BMS, with requirements that the BMS monitor and react to both cell voltage and temperature during both charge and discharge. It may not be totally comprehensive, but you can't fault them for making their requirements clear.


Do you have a direct link to the document?
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

Beemer
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Re: CALB CA series cell performances

Postby Beemer » Wed Jul 18, 2012 9:23 am

Seems the man in the EU wrote the warrantee based on his beliefs.
Oddly. Considerably more cars as a percentage of users have burned down due to having a bms than otherwise. How many bms makers guarantee their product will not let the cells/packs/cars/garages/homes destruct and will pay for the damage if it does happen? I know EXACTLY how many... None!

Tom Hardy using headways on 340 cycles (so far) proved beyond any doubt there is no such thing as Lithium cell drift. You bottom balance and never overcharge.. How simple can that be?

The document:-
http://www.batteryvehiclesociety.org.uk/bvsorguk/forums/download/file.php?id=332

I summarised here:-
Thanks for that Matt. There we have it.

Something to consider for the lovers of small packs
Standard (dis)charge rate is 0.3C

Limits
3.6V per cell/pack max.
Trickle to no less than 0.05C
Float charging to 3.4V.
Warning alert at 3V

Absolute max Voltages
Cut-off charger when the first cell hits 3.9V
Cut-off controller when the first cell hits 2.5V
2V or under is considered unrecoverable.

Temperature ranges
Cool the cells at 40°C
Reduce power at 50°C
Kill the pack at 55°C
Range 5°C to 45°C
Never charge at 0°C or below.

mikethebike3
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Re: CALB CA series cell performances

Postby mikethebike3 » Wed Jul 18, 2012 10:08 am

I've just sent the following to Andy Zhou of Calb (the EU contact on Calbs Chinese website).

Dear Andy (also copied to Peter at Calb Europe for his information)
I live in the UK and am at the stage of upgrading my EV battery pack to LiFePo4. I have been very impressed by the reported performance of your CA cells.
I contacted your Europe Agency Office who have been most helpful (thanks Peter!).
I see from your documentation that an active Battery Management System is required to meet the terms of the warranty. This states that the warranty is for "18 month after deliver with free exchange of the cells and additional 18 month 50% if a high class battery monitoring and balance system is used." (taken from the CalbWarrantyEurope document which Peter kindly sent me when I asked for details of the warranty on these cells). Another document is more specific about what is technically required of this BMS.
As my experience in these matters is limited, I've joined a UK EV forum discussion regarding your cells:
http://www.batteryvehiclesociety.org.uk/bvsorguk/forums/viewtopic.php?f=3&t=3334
Would you care to comment on these by joining in this discussion? It seems that there are many who believe that an active BMS is not a good idea, but as this is a big personal investment on my part, I don't want to break the terms of your warranty.
Hoping you can join in!
Best wishes
Mike

Hopefully we'll all see what happens, I'll advise if I receive anything in the form of a personal reply.
At the end of the day, I just want to buy some batteries and enjoy them knowing I have backup, BMS or no BMS!

Mike


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