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Being a tightarse, I'm leaning towards the lead acid.  As my wife said, I could lose 5kg to make up for the battery.    (Notice she didn't volunteer...)    

When I bought Mabel I thought about 12 months to do the repair/rebuild...hahahahha yeah right..its turned out to be complete rebuild. I only bought the rear fuseage frames and firewall from ICP the re

Ok, so I decided to get the info from the horse's mouth and asked Bert Flood's what they recommend.   The bloke there said Panasonic LC-XC1221P, which is a deep cycle battery (21AH).  So I r

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1 hour ago, tillmanr said:

I recently replaced the battery in my Foxbat like for like with a Fusion 

CBC12V22AH. 6kg. The Rotax  is a 912 ULS 100HP

Bought it on eBay $84 delivered

I could not find the CCA for this battery.  This makes it hard to compare with others. 22AH very nice though.

Great price

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One way to use the extra voltage of a LiFe battery would be to lose some voltage by using lighter leads if the battery was behind you.

If you do put the battery back there, make sure it is in a compartment which has an external vent. If venting fumes does occur, they will not kill you.

Yes, I know that LiFE does not catch fire and it is wise to fuse it close to the battery, but still there is a lot of energy there and I reckon nasty fuming is a possibility.

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the thing is, you cannot permit much voltage drop from the front to the battery in the back  because what will happen is that the alternator charging system will force current into the battery via long leads, and the charging system will see a voltage higher than the battery  (due to voltage drop in the cable) , and the battery wont get charged correctly. and the charging system will be very noisy- read on :

 

Let's explore this a bit more.

I've already done the numbers and assumed we use 16mm2 cable , 3 meters distance .(6 meters of wire) . that's a resistance of 6.4 milliohms.
That will be a volt drop of 150A (jabiru 6cyl )  =0.96V which will be OK for a LIFEPO battery that will crank at at least 12V . (no good for lead acid, would need to double the wire size) 
So, for the alternator pushing in 20 amps, that is 0.128 V. probably OK.

However ! the ROTAX and Jabiru charging systems both generate their power in pulses, and  rely on having a very close battery low resistance, or large capacity capacitor at the regulator.

So, while you might get away with the 16mm2 cable, be sure to use the 22,000uF capacitor, rating 25V or more , 105C temp rating  at the regulator if you move the battery  a way.  A 25 V  leaded transzorb should be put across the capacitor .

Oh there is another requirement. If the battery isolator was triggered, the alternator charger would feed to electrical system directory- potentially very very bad !

What's really required is that the charging system either has another set of wires that runs back to the battery , then a separate set run back to the front of the plane (IE the LOAD circuit).

 

(Unless the alternator battery charger is replaced with something a little more capable.) . There's something I need to do.  I've so far done a prototype.
 

So overall, it might be just easier to leave the battery where it is, and provide a proper battery contactor isolator.  keeps the plane nose heavy.

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This is the contactor I am using to connect the battery to everything else but the starter motor. 

IE the master electronics solenoid , its called an     SW60-360P   

 

 

this one is a nice well rated solenoid,  80A all day, and rated for 150A for 250 seconds .

very nice for rotax/ jab 4 cyl starter. jab 6 cylinder makes it work a bit. 

it has double breaking silver plated contacts.  and IP66.  rated to 60 deg C for full spec, unlike most. still dont stick it next to the exhuast manifold. 

 

https://www.farnell.com/datasheets/2290076.pdf

 

goto element 14 and search for the SW60-360P. $35

 

https://au.element14.com/albright-engineers/sw60-360p/contactor-c-o-12vdc/dp/1137938?CMP=KNC-GAU-GEN-DSA-PDP-PAGE&mckv=s_dc|pcrid|435342446126|pkw||pmt|b|slid||product||pgrid|98446732062|ptaid|aud-956906391805:dsa-922446159331|&gclid=CjwKCAjw3_KIBhA2EiwAaAAlitj6d0OuAzqioR63y4ykAqHRMFyJpTuDiQRRVah82p74GpUwet-smRoCTt0QAvD_BwE

 

 

 

 

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3 hours ago, RFguy said:

This is the contactor I am using to connect the battery to everything else but the starter motor. 

IE the master electronics solenoid , its called an     SW60-360P   

 

 

this one is a nice well rated solenoid,  80A all day, and rated for 150A for 250 seconds .

very nice for rotax/ jab 4 cyl starter. jab 6 cylinder makes it work a bit. 

it has double breaking silver plated contacts.  and IP66.  rated to 60 deg C for full spec, unlike most. still dont stick it next to the exhuast manifold. 

 

https://www.farnell.com/datasheets/2290076.pdf

 

goto element 14 and search for the SW60-360P. $35

 

https://au.element14.com/albright-engineers/sw60-360p/contactor-c-o-12vdc/dp/1137938?CMP=KNC-GAU-GEN-DSA-PDP-PAGE&mckv=s_dc|pcrid|435342446126|pkw||pmt|b|slid||product||pgrid|98446732062|ptaid|aud-956906391805:dsa-922446159331|&gclid=CjwKCAjw3_KIBhA2EiwAaAAlitj6d0OuAzqioR63y4ykAqHRMFyJpTuDiQRRVah82p74GpUwet-smRoCTt0QAvD_BwE

 

 

 

 

Thanks RFguy,

 

I have the standard solenoid -came with the engine I bought.  (This one is brand new, obviously when the flight school owner changed out the engine on his Foxbat he left all the old ancillary stuff in the engine bay - muffler, electrics etc).  He gave me the brand new muffler and solenoid.

 

Today I managed to get the steel case off the battery.  They had used a weak glue-like substance - similar to what you get on jar labels.  Haven't yet weighed the case.

 

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Note the FullRiver HC18 and PC625 (used in the Jab) have their positive terminals on opposite sides so that may not work for Jab owners, depending on current lengths.

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On 07/08/2021 at 11:58 AM, Bruce Tuncks said:

But do not be fooled by "lead-acid equivalent" amp-hours which means nothing except a rip-off.

I am no expert, but isn’t lead-acid equivalent relevant because lead acid batteries have better cranking current capacity, relative to Li  batteries, if they have the same Ah’s? 

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actually most LIFEPO will do 3C,  a good percentage will do 5C continuous , and 10C for a short time - 10 seconds 

but some will only specify for 2C max

 

for example, standard Thunderskys ( a economical brand) 

https://www.evlithium.com/thunder-sky-winston-battery/lifepo4-40ah.html

 

they'll do 3C all day, 10C for 15 seconds. entirely suitable for a 6 cyl jab. 

*putting aside the charger issue*

 

These cylindrical cells will do 10C

https://www.evlithium.com/Headway_Battery/headway-40152s-17ah.html

 

 

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With a new build plane I wouldn't decide the placement of the battery until I was doing   the Weight and balance bit. It's the obvious thing to use to adjust  the Cof G. Nev

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About charging LiFe batteries: I just use the inbuilt Jabiru alternator setup, but I have a digital voltmeter so as to switch the charging off as soon as the battery is at 14.2 volts. This is usually achieved before the plane has moved.

In flight, there are a few big capacitors which the alternator thinks is the battery and the radio works ok from this, the voltage is about 15 volts from the Jabiru regulator. I do have a power-supply cleaner for the radio, bought from a 4WD place.

The standard Jabiru setup would soon ruin the LiFe battery without some protective charging electronics.

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47 minutes ago, Bruce Tuncks said:

...The standard Jabiru setup would soon ruin the LiFe battery without some protective charging electronics.

My PowerMate regulator seems to do the job, letting 14v get to the LiFePO4 battery. Its resting voltage is 13.2v, which it holds for weeks.

 

 

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3 hours ago, facthunter said:

With a new build plane I wouldn't decide the placement of the battery until I was doing   the Weight and balance bit. It's the obvious thing to use to adjust  the Cof G. Nev

Bit late for that!

 

Hopefully I don't have to put a lot of weight down the tail end.  I can move the battery if necessary but I'd rather not.

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4 minutes ago, Marty_d said:

Bit late for that!

 

Hopefully I don't have to put a lot of weight down the tail end.  I can move the battery if necessary but I'd rather not.

A lead battery is a major component of your W&B.
After I replaced my 4kg Decca with a 1.6kg lithium, I had to move the wing aft 18mm.

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3 minutes ago, Old Koreelah said:

A lead battery is a major component of your W&B.
After I replaced my 4kg Decca with a 1.6kg lithium, I had to move the wing aft 18mm.

You had to move the WING?

 

That seems like a big step for a 2.4kg reduction in weight (presumably at the firewall if you're moving the wing aft).

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Just now, Marty_d said:

You had to move the WING?

 

That seems like a big step for a 2.4kg reduction in weight (presumably at the firewall if you're moving the wing aft)

First of all, I moved as much fixed equipment like toolkit, spare parts, etc. forward as far as possible.

Because of my aircraft’s design, it wasn’t a monumental job and was an opportunity to install new mounting bolts and brackets. 
Afterwards I did lots of testing and CoG stays well within the original designer’s range.

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probably depends a bit of the overall weight of the aircraft..... 

in the J230, for 2 pax  no bags and 2/3 fuel, moving the 6kg battery from up front to behind the front seats (which is under the max chord on the wing approx) moves the CG aft about 1.2%, which is very welcome actually for these rather nosey aircraft.

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Mabel most likely will be a different beast to The Girlfriend.

I am leaving the battery install until she is all together and I do the W&B. I have a 13kg chute installed also heavier main wheels and the exhaust and muffler will be heavier. So really not sure where the battery will end up. The battery on the S model is just behind the pilot..in the XL it was down the back. The rear of the S is much heavier than the XL so hence the battery is more forward. But with the accessories I have I think I am going to be a bit tail heavy. I think the battery may end up at the firewall between the rudder pedals and the firewall. Also of course if I have a issue then it will be a heavier type battery but if it works out I am close then maybe a lighter battery behind the pilot. I did install the battery holder behind the pilot just in case.

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fine business Mark. where is the chute  ?
even with LIFEPO batteries, I'd still budget at least 4kg  (912ULS) (6kg JAB 6 cyl )  in a LIFEPO battery. anything less and it doesnt have good starter discharge capability....

LIFEPO can save some space though. 


 

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it's not printed on LIFEPO batteries
LIFEPO discharge capability can depend on a bunch of things , just like lead acid batteries. If you have a lead acid battery  not specified for high discharge currents, you'll strip the plates off it whenyou hit the starter !

So you got to look up the numbers for that battery.

 

The upside is :

Is that the LIFEPO will usually be 11.5 - 12V instead of 8 to 9V when subject to starting currents, so the starter may run at a slightly lower current (because there is more voltage) .. (or do much more work - depends on the winding and motor) .

 

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