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Discussion Starter · #1 ·
Apologies if someone posted this already. Bought some Lithium Phosphate batteries and replaced my lead acid. MO magazine in Germany had a brief mention of these batteries--said they would work (can handle the heat unlike lithium polymer). Can't find the place I ordered them from right now, but they are 4 cells each and nominally 13.2V. Just one group of four cells has the same AH as the stock battery, but I figured I'd go for two since they are so small and light. the two together weighed 600 grams, compared to 4700 for the stock battery and box. Will let you know how it goes...

John
 

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Interesting idea. You test it for a while and give us a full reports. Now if you moved the voltage regulator into the breeze (since it gets real hot), like the way NCR does, you'd have a place for your two batteries.

 

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Discussion Starter · #4 ·

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The RC articles all mention that these batteries need a LiFePo/A123 specific charger.

Not sure why - is the charging cycle voltage or current sensitive?
Did you modify anything in the charging circuit ?
 

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I seem to have heard stories about these batteries (Li-Poly???) being kinda' sensitive to charging. As in BOOM :eek: if overcharged/overheated.

Just saw these aren't Li-Poly when re-reading first post. Might be OK then.
 

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Discussion Starter · #8 ·
OK, have to admit I embarked on this experiment without doing my own research--just relying on the MO article--and my German isn't so good. Did some more research on my own and this is what I came up with:

1) The rated Ah on the stock battery is 10Ah versus 2.3Ah for one A123 pack and 4.6Ah for 2 packs. However, the A123 packs keep up their voltage when discharged better than the lead acid and don't suffer like lead acids do when you deep discharge.

2) Based upon ratings for similar batteries, the stock lead acid battery probably provides around 170 cranking amps vs 120 (10 seconds) for one A123 packs and 240 for 2...glad I went for two packs.

3) Charging batteries seems to be based upon two variables: max amperage and max voltage. When initially charging a discharged battery, you want to limit the amount of current it absorbs (constant current phase). The A123s are rated at 3A per pack for standard charge and 10A in fast charge mode. I am not sure about the lead acid, but I believe they are rated for far less (anybody know this for a fact?).

After a while of charging in constant current mode, the voltage of the battery rises and you want to keep it from going higher than a max voltage (constant voltage). For lead acid batteries, this voltage is 13.6volts, but more sophisticated charges will provide 14.4V for a while, then reduce to 13.6V for charge maintenance. The A123s are rated at 14.4V (4 in series) constant voltage charging. I measured the voltage being provided to the batteries by the motorcycle and it came in at 14.2V--just about perfect. One thing I don't know is if it is OK to continuously charge the A123s at 14.4V. The positive, though, is I haven't read anything that says it shouldn't be done. Plus it's not like I ride my motorcycle continuously.

The tricky bit with charging the A123s seems to be cell balancing--although you may have 14.4 volts in total across the 4 cells, it is possible to have one cell at 5.1 volts and the other cells at 3.1V--for example. Although the A123s seem to be tolerant of some overcharging, if it's too much you will lose a cell. The good news here is that when the cells fail they don't explode/catch on fire. The cell packs have individual leads to each cell so that you could build a balancing circuit to avoid this. A123 systems actually sells lead acid replacement batteries with built in balancing circuits:

http://www.gyllingteknik.se/a123/ALM12V30 Spec Sheet July 2007_confidential.pdf

I'm going to try my luck without the balancing circuit. Reading the Radio Control web sites, there seem to be a lot of people going without balancing circuits without trouble. The tricky bit seems to be initially charging the batteries from a deep discharge--I don't plan on encountering that too often. If they are already fully charged and in balance, then they seem to stay that way--fingers crossed. BTW my batteries came fully charged. Will let you know if I lose a battery.

So to sum up, still don't know everything, but they seem to OK with the addition of a balancing circuit. Time will tell how they do without one.

regards

oh, here is the spec cheet:

http://a123systems.textdriven.com/product/pdf/1/ANR26650M1_Datasheet_AUGUST_2008.pdf
 

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hi there in switzerland. :)

as a german, i came across that article too,
and did some research also.

here is a nice link to the web-site of mr.
thomas durbahn, who has some experience
with the li-po's already, and sells them in
soldered packs.
There is some good information on his side.

cheers. :)


http://shop.durbahn.de/shop/en/products/Batteries_superlight_!
 

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Hmm, interesting. The Durbahn site is entirely focused on total loss systems for the track and quick chargers in the pits. There's no information on they're site about running these with the stock charging system, although they do make a tiny mention that you can.
 

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Discussion Starter · #11 ·
doooh!!!

took it out for a test drive today and something strange ahppened. When I get on the throttle hard--I mean really hard--the power cuts out and the engine light comes on. Back off the throttle and everything is fine again. Don't see what the battery could have to do with this unless it is affecting the fuel injector somehow. I would have thought the voltage regulator would take care of any voltage deviation relative to a lead acid battery. Could it be coincidence that an unrelated problem occurs right when I swapped out the battery? Anyone run across this problem of the power cutting out when on hard throttle? Just about crushed my b*lls the first time it happened.

John
 

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Could it be coincidence that an unrelated problem occurs right when I swapped out the battery?
John
Of course. This kind of thing happens all the time for two possible reasons:

1. Coincidence

2. You loosened some connection, or otherwise messed up something else WHILE you were working on the battery setup


This doesn't change the fact that it is also quite possible that somehow the battery switch did it, but it is in no way certain that it's the battery.
 

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I would have thought the voltage regulator would take care of any voltage deviation relative to a lead acid battery.
I have no idea how a motorcycle voltage regulator works, but the audio gear voltage regulators I've worked with have regulated voltage down only - not upwards. That is - They don't take care of sagging power.
 

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Discussion Starter · #15 ·
OK, found the problem...

the positive lead was rubbing against a sharp piece of metal and made a tiny hole in the insulation tape--so tiny I didn't notice it before. Upon hard acceleration, it was making contact with the metal and shorting--the inside layers of tape had burnt evidence of the momentary shorts. Anyway, moved the lead and everything is running fine.
 

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that is fine, everybody here was thinking of a battery
related problem i guess, something like
a not properly tightened pole or so...

anyway, there were some interesting readers
comments in the following MO issue, regarding
safety and capacity of the LiPos.
one guy wrote about a company in the states,
who supplies similar LiPo batteries but with a
greater capacity, so they are even more adoptable
to motorcycle use.

i see if i can come up with some link or more
detailed info later on, because i am busy in the
shed right now.

cheers. :)
 

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Discussion Starter · #17 ·
that is fine, everybody here was thinking of a battery
related problem i guess, something like
a not properly tightened pole or so...

anyway, there were some interesting readers
comments in the following MO issue, regarding
safety and capacity of the LiPos.
one guy wrote about a company in the states,
who supplies similar LiPo batteries but with a
greater capacity, so they are even more adoptable
to motorcycle use.

i see if i can come up with some link or more
detailed info later on, because i am busy in the
shed right now.

cheers. :)
Would be greatly appreciated. Which issue was it? I have been checking to see if there were any follow ups, but didn't think to check the reader's comments. My German is so bad it is really a struggle to read. Must learn German...

thanks, John
 

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hi there.

it is in issue #8, the one right after to which
the LiPos had been mentioned first.
is to find in the same section called "Werkstatt",
there are several letters concerning
this topic.

the shop in the states should be

www.splendidbattery.com

but i hadn't time to check it yet,
they are said to have LiPos up to
8000 m Ah instead of 2300 m Ah
from the ones we are talking about
here so far.



-> no need to learn german, if you didn't grew
up with it.

:)
 

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Discussion Starter · #19 ·
the shop in the states should be

www.splendidbattery.com

but i hadn't time to check it yet
thanks Muschi,

I just checked it out. It's actually a chinese factory. I'm still a little fuzzy on these things, but from what I can tell, there are various proprietary blends of LiFEPO4 batteries. I've seen some references that the ones produced by A123 systems (in the US) are better, but haven't seen anything definitive on that. The ones I bought from the web site in Germany that MO mentioned were advertised as A123 batteries, but I can't actually see the batteries under the plastic wrap to verify. The wikipedia page gives some more info on what makes LiFEPO4 batteries special:

http://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery

regards, John

RE learning German...that's my problem, it is too easy to get by with just English here. And then when someone does speak German with me, it's Swiss German.
 
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