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Old 04-04-2012, 08:41 PM   #136
_cy_
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why LiFePO4 batteries in particular go out of balance without BMS
http://www.advrider.com/forums/showt...6#post18382326
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Old 04-04-2012, 10:09 PM   #137
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Originally Posted by _cy_ View Post
why LiFePO4 batteries in particular go out of balance without BMS
http://www.advrider.com/forums/showt...6#post18382326
I see that _cy_, but I am watching and measuring as LiFePO4 cells DO self balance.

Once a cell becomes full, the voltage goes up on that cell rather rapidly and current falls rapidly. This and the mechanics of the cell is what makes LiFePO4 highly tolerant of overcharging.

HOWEVER, once the knee is reached, current does continue to flow as the full cell experiences a rise in voltage. This current is doing nothing to charge the full cell as it is already full, but nearly being converted to heat in that cell.

Since all 4 cells (or groups of stacked cells) are in series, the only way for that current to flow is to flow through the full series.

The same current that is heating the full cell is simultaneously charging the lower SOC cells.

This effect would be minor if charged by a typical charger because the charger would shortly switch off once the voltage threshold was reached, but.........

The motorcycle charging system does no such thing, it maintains a constant voltage regardless as long as the engine is on, and a small current will continue to flow through the whole series of cells, always heating the full cells, always charging the less then 100% SOC cells.

Not only have I read about this effect, I have measured it.

Fully charge the Shorai At 14.4 volts for 5 hours, switch to a fixed and constant 13.84 volts, and effectively zero current flows through the series (2 micro amps) Below likely self discharge.

Fully charge a Shorai LFX21 at a constant 14.4 volts and leave it at 14.4 volts for the next 48 hours and nearly 40 mA continues to flow, which is plenty high to keep the series of cells in balance.

For the 16 cell Antigravity battery, owing to slightly different doping and construction the picture is even better. At 13.84 volts, 6 mA will continue to flow forever. 6mA is plenty to keep a battery of this size in balance if the bike is ridden often.

at 14.4 volts constant, 53mA flows through the 16 cell Antigravity battery. That level of current will correct 0.5% of imbalance per 24 hours. Not a lot, but as long as the cells are well matched, more then enough to keep a battery in balance that is in a bike ridden at least occasional in my judgement.

All of the above is no doubt why the 5th Shorai a BMW owner has sent me was perfectly balanced at 5 months of use. It was out of an R1200GS which charges at 14.4 volts where as the 2 Shorai batteries I received used that were badly imbalanced were out of F800GSs that charge at 13.84 volts.

Although it does not all of the exact mechanisms like I just have

#3 in this link eludes to it and explains one of them

http://www.rev-electricbikekits.com....0Batteries.pdf


longevity between the two is TBD and theres dozens of other differences, but both Shorai and Antigravity LiFePO4 SLI batteries will self balance and other things being equal, the Antigravity battery will at a lower voltage all the way down to 13.84 volts where as the Shorai won't start to self balance at anything under 14.38 volts from my measurements.
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Old 04-04-2012, 11:46 PM   #138
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It was out of an R1200GS which charges at 14.4 volts ....

Joel and how about to use R/R from R1200GS ? I was already for the last few days thinking to ask about it.The voltage at 14.4v is right and as stator output on 1200GS is 720 watts(I think).....that could be solution.
I might be wrong but I don't think reducing the wattage on F800 from 400watts to 380 watts to prolong the stators' life would be a good idea as those 400watts is already poor performance for so called "adventure bike".

RadoR6 screwed with this post 04-05-2012 at 12:00 AM
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Old 04-04-2012, 11:52 PM   #139
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Originally Posted by RadoR6 View Post
Joel and how about to use R/R from R1200GS ? I was already for the last few days thinking to ask about it.The voltage at 14.4v is right and as stator output on 1200GS is 720 watts(I think).....that could be solution.
Totally different. The R1200GS uses a wound rotor car style alternator with an internal regulator, not a PM alternator with shunt regulator.

Same story with the modern K bikes.
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Old 04-05-2012, 01:43 AM   #140
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Quote:
Originally Posted by JoelWisman View Post
sorry guys, took a 3 day ride so been out of the loop for a bit.

Mike C I am knee deep in testing an Antigravity battery and SO FAR it has passed everything the Shorai failed.

Riding! Jees mate get on with it, there's no time for riding batteries are a cookin.

3 days - Bloody Nora I wish, I'm layed up witrh a broken collar bone after crashing the MTB in a training run for the August ride. Hope it was a blast!

Which version of the Antigravity are you testing?
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Old 04-05-2012, 06:49 AM   #141
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Originally Posted by JoelWisman View Post
Totally different. The R1200GS uses a wound rotor car style alternator with an internal regulator, not a PM alternator with shunt regulator.

Same story with the modern K bikes.
Know anything about the G450X charging system in regards to lithium based battery use? I have one in mine, and am wondering if a long walk or push out of the woods is in my future.
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Old 04-05-2012, 06:49 AM   #142
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New lithium batt 3rd Generation

I would like Joel to test and post results of the new LiFEpo4 battery I have.
I will send it to u free to test. Just return it after testing.
how do I contact you ?
Thanks
Andy
falconev at gma_ _ dot com
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Old 04-05-2012, 08:03 AM   #143
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Originally Posted by battman View Post
I would like Joel to test and post results of the new LiFEpo4 battery I have.
I will send it to u free to test. Just return it after testing.
how do I contact you ?
Thanks
Andy
falconev at gma_ _ dot com
Hey Andy,

Is this it? http://www.falconev.com/batteries.html

Are you using A123 cells?
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Old 04-05-2012, 09:40 AM   #144
battman
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Hi
I have a newer cell now. I was using the A123's, just like ballistic and A-gravity.
my testing shows a lower IR than A123 5-6 vs 8-9 mohms
am using the 18650's in a clear case, pretty cool looking. A see - thru battery.
email me for address exchange
thanks
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Old 04-05-2012, 10:08 AM   #145
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Mike C, OUCH, broken collar bones hurt! I assume they have you on good drugs? You are doing it wrong, you are not supposed to train for rides by getting broken bones, you are supposed to train for rides so that you don't get broken bones!

Heal fast my friend.

As to Antigravity, Im testing their YTX12-16. Waterproof YTX12 size case, so direct fit or direct fit with a little shimming in most adventure bikes. 16 cell as it gives an honest 9.2 amp hour that yes, will give a little better amp hour performance then a 9.2 amp hour lead/acid battery who's internal resistance would go up under continues discharge.


ScienceOfDirt, I know a LOT about the G450, including it's charging system, and a walk is in your future :) but not because on the lithium battery use

Okay, being serious now, fun at your expense is over :) The G450 has a tiny space for a battery where it is exposed to fling from front wheel. As you know, no way to turn headlight off when you shut the engine down, you just have to wait for it to time out, which guarantees it never sits with a full battery. Large starter draw as the motor is very high compression. Radiator heats the bottom of the battery, and if any snag gets caught near the battery, it gets smashed through the battery when the handle bars go to full lock.

This is a battery eating machine!

But, unlike lead acid, lithium batteries will actually last longer if kept slightly below full and your charging system finishes at 14.35 volts, so good on that front as well.

Waterproof is a BIG deal if you ride in any mud, in the rain, or water cross. Most LiFePO4 manufactures are not using sealed cases, especially with respect to where the battery terminals enter the case.

Oh, and unless you have had the recall done AND it was done right (i.e. the tech cleaned all oil off of threads before applying locktite) the flywheel likes to come off which does no good for the charging system as it is the rotor with the magnets.
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Old 04-05-2012, 10:30 AM   #146
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Quote:
Originally Posted by battman View Post
Hi
I have a newer cell now. I was using the A123's, just like ballistic and A-gravity.
my testing shows a lower IR than A123 5-6 vs 8-9 mohms
am using the 18650's in a clear case, pretty cool looking. A see - thru battery.
email me for address exchange
thanks
e-mail sent
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Old 04-05-2012, 02:24 PM   #147
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Laugh

http://www.ballisticparts.com/

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Old 04-05-2012, 06:15 PM   #148
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Quote:
Originally Posted by JoelWisman View Post
ScienceOfDirt, I know a LOT about the G450, including it's charging system, and a walk is in your future :) but not because on the lithium battery use

Okay, being serious now, fun at your expense is over :) The G450 has a tiny space for a battery where it is exposed to fling from front wheel. As you know, no way to turn headlight off when you shut the engine down, you just have to wait for it to time out, which guarantees it never sits with a full battery. Large starter draw as the motor is very high compression. Radiator heats the bottom of the battery, and if any snag gets caught near the battery, it gets smashed through the battery when the handle bars go to full lock.

This is a battery eating machine!

But, unlike lead acid, lithium batteries will actually last longer if kept slightly below full and your charging system finishes at 14.35 volts, so good on that front as well.

Waterproof is a BIG deal if you ride in any mud, in the rain, or water cross. Most LiFePO4 manufactures are not using sealed cases, especially with respect to where the battery terminals enter the case.

Oh, and unless you have had the recall done AND it was done right (i.e. the tech cleaned all oil off of threads before applying locktite) the flywheel likes to come off which does no good for the charging system as it is the rotor with the magnets.
I'll mention the oil on the threads issue to the tech. I'm waiting for puma to approve my torque limiter replacement at the moment. For what it's worth, I pulled the pin on the headlight switch so that it's not always on. It now has a working off portion.

I think the stock AGM is going back in for the first adventure/enduro. It was a mud fest last year. Luckily, it was my riding partner who burried his bike in the creek, and not me.

If a LiFePO4 battery gets submerged, is it OK after drying. We're not talking salt water here.

Anything else you want to share about the 450 I'd like to hear, but this thread is not the place.
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Old 04-06-2012, 03:24 PM   #149
ebrabaek
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This just came in the mail.....


Preliminary results are in line with what you said Joel.... " as they get older...they drift" comparative test shows my trusty...or should I say rusty old meter is 0.25 volts high... I will do the test and mod in the am....

Erling
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Old 04-06-2012, 05:18 PM   #150
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Originally Posted by HighTechCoonass View Post
Funky sizes! Ballistic went with big cruiserisc sized cases so nothing bigger then the 8 cell is going to fit in the usual adventure bike battery box.

Trust me, an 8 cell A123 based battery is NEVER going to pass my test for adventure / touring use.

If someone sends me one, be happy to test it, but 16 cell for adventure / touring. 8 cell for scooters or low cc sport bikes.

Also, as amusing as it is to read their warranty policy, water intrusion NOT being warrantied is likely fine for scooters, big dumb cruisers and sport bikes, but won't work so well for tourers / adventure riders.
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