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Old 02-21-2013, 03:39 PM   #294
JoelWisman OP
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Joined: Apr 2009
Location: STL, MO, USA
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Quote:
Originally Posted by Bli55 View Post
JoelWisman, oh how I missed your experiments!!
Just last night I studied the whole thread and remember wishing you would carry on with the envistigation, because there's so much more...

I mean, not only the aspects of your testing such as cold performance, chargers etc, but the LiFePO4 field itself is developing rapidly, with new names and products appearing.

I'd really appreciate if you could clarify a few points...

Imagine I have a bike with iron phosphate and a voltmeter.
Riding along, would probably see ~14.2-14.6 V
Imagine then some eqipment gets switched on - lights, heated gear etc...
Voltage might drop to ~13.0-13.5 on the voltmeter...
Does that mean - battery is discharging as the alternator is not able to support the consumers.
- battery is not discharging, as the alternator output is sufficient, but WILL get out of balance due to lack of current passing through it?

In other words, what minimum voltage would you suggest needs to be maintained (by regulating additional power consumption) in the system when riding as to ensure the cells are charged AND balanced?
A voltage below 13.8 will certainly mean the battery is discharging, however as voltage lowers further, current output from the stator will increase slightly. This is due to the efficiency of magnetic flux lines creating electromotive force and is beyond the scope this thread for me to explain (it would take me cracking open text books and typing a novel) but if any electrical engineers want to take a crack at it, be my guest.

In round approximations, a stator can put out perhaps 1% more current at 13 volts then at 14. Further purely resistive loads such as heated gear and incandescent lighting will draw less current as voltage falls, so though you are likely not charging at voltages below 14, you may not be discharging the battery, at least not completely but simply drawing the battery down some until rising stator output and lowering resistive draw come to equilibrium. OR if the current draw is truly excessive, yes your going to run your battery dead as you ride. So the answer is: MAYBE. Keep riding and if the voltage keeps lowering, you will have your answer as the voltage falls below 10.2 volts and the fuel injection shuts down lol.

A number of things affect cells getting out of balance.

1: Manufacturing differences. Cells from the manufacture may have slightly different internal self discharge rates, differing capacities and differing internal
resistance. All of this is a matter of the manufacture quality control and this has far and away the largest effect on a batteries tendency to go "out of balance".

A123 has great quality control! Further battery manufactures that care carefully test each and every cell before assembling. Since there is typically considerable time between A123 making a cell and a battery manufacture putting those cells into a battery, super accurate 5 digit voltage tests will reveal any cells with different internal discharge rates. Great manufactures test for and exclude these outlier cells and always complete a battery with cells from the same manufacturing lot.

2: Cells at different temperatures will have different internal resistance and will go out of balance quicker. This is an issue of application. In the F800GS the basic module heat sink is pressed against one side of the battery and the cool air box the other. This is not helpful for keeping a battery in-ballance.

3: usage: If a battery spends most of its time fully charged rather then deep cycling it will age slower. Actually it will age slower yet if it's always at 50% state of charge but thats not practical. Use a battery heavily and it will age quicker and slightly different manufacturing tolerances will show up quicker.
This is the way of the world but another reason to size your battery large. Not only will it have more overhead for emergencies but it will age slower and last longer

4: Lastly there is a very slight tendency that SOME chemistries of LiFePO4 have to self balance. It only occurs when the battery is fully charged and a regulated voltage continues to be applied. This effect is measurable with expensive test equipment in the range of 14.3 to 14.7 volts. This effect is very slight, so....

No your bike drawing on the battery at times will not make it out of balance any quicker as long as it does come up to at least 14.3 volts for considerable periods of time, but will age the battery quicker.

Quote:
Originally Posted by Bli55 View Post
Why would the starter get damaged operating at lower than optimal speed/voltage?
Or is this only applicable to certain types of starter engagement?
This ONLY applies to starters that use a solenoid to ram a pinion into interface with a ring gear. Neither the Ftwins or singles are damaged by under voltage starting, the R series boxer ARE DAMAGED by under voltage starting.


Quote:
Originally Posted by Bli55 View Post
I have a charger with one knob controlling the current (0 -10A), but obviously is i set it to, say, 1A, and connect to a poorly charged battery, it will only need a small overvoltage to maintain that amp.
As the battery gets charged, my charger ups the voltage to maintain this set current, until it reaches 15V.

Do you know if this is a what you call manual charger and if its suitable, or do I need to search for one with a set max. charging voltage of 14. what ????

Thanks for your time on this topic!!
Manual can mean quite a few things when speaking of chargers. Your charger is specifically classified as a "constant current charger with 15 volt cutoff". It is awesome and I wish I still had one, but is totally unsuitable for charging LiFePO4 or AGM batteries. A charger for LiFePO4 MUST cut off no higher then 14/7 volts and the industry is moving towards a cutoff of 14.5. Also it is not particularly desirable to keep applying regulated voltage after you reach, say 14.5 volts but better to disconnect completely and monitor and recharge if the LiFePO4 battery gets below say 13.5 volts.
This: http://www.tecmate.com/u_optimate_lithium.php is one charger that is doing all the right things according to current theory and evidence.
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Owned to date. Honda Aero 50, Honda Elite 80, Honda Elite 250x2, Suzuki Katana, Suzuki RF600, Yamaha YZF1000R, Kymco Xciting 500, Suzuki GS500, Suzuki Burgman 650, BMW F800GSx2, BMW S1000RR, Aprilia Scarabeo 200, Aprilia Caponord, Aprilia Sportcity 250
I love and miss you Jeneca and I'm sorry.
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