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Two-battery question

Started by ducatiz, May 15, 2010, 05:29:35 PM

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ducatiz

May 15, 2010, 05:29:35 PM
My 98 900ss has a mono seat with a lot of space under it.

I was thinking of relocating the battery there.

THen I think, why not split the battery into two?  Move only part of the weight there...

Connecting two batteries in parallel looks like a big battery, this I know.  I have charged up multiple car batteries with a single charger this way.

But how does calculating CCA work across two separate batteries, or am I overthinking (cause it's just double the number of cells...)

Seems to me you could -- with proper wiring -- run two smaller batteries with the same or higher Ah rating and have the same cranking.

Can anyone comment on this?

It would be nice to be able to move both batteries to more weight-distribution friendly locations.
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"Yelling out of cars, turning your speakers out the window to blast your music onto the street, setting off M-80 firecrackers, firing automatic weapons into the airâ€"these are all well and good. But none of them create a merry atmosphere of insouciance and bonhomie quite like a revving motorcycle.

suzyj

#1
May 15, 2010, 05:55:16 PM
From an electrical perspective, you want to have the battery as close to the starter motor as possible, to minimise voltage drop.

Assuming the batteries are the same, you'll only double the CCA with a second battery if the resistance of the wiring between each battery and the starter motor is also equal.  Otherwise the lower resistance one does most of the work, and the other one is mostly for decoration.

As a rule, if the difference in cable length is two times, you'll need cable with twice the cross sectional area.  At a guess, the cable run from behind the seat to the starter motor would be four times or more longer than the one from the stock battery, so the cables would have to be four times the area (twice the diameter) to make up for the extra length.



2007 Monster 695 with a few mods.
2013 Piaggio Typhoon 50 2 stroke speed demon.

ducatiz

#2
May 15, 2010, 06:17:59 PM
That's the kind of info I am looking for.

I would be moving both batteries, so I could fab the wires to be the same IF I decide to do it.

Basically, you're saying to keep everything equal between the two batteries and they will both work, but if one is on shorter/lower impedance wires, it will do more work.

That makes sense.

The other idea I had was to put the second battery on a solenoid for the starter.  The second battery would only be on the circuit when I hit the start button.  That is how my truck is set up.  Would the wiring have to match resistance under that setup?

But then I have the issue of charging it.  I don't want to have to keep it on tender.

The point is to keep a relatively simple system in place, but figure out some weight and space advantages.



Check out my oil filter forensics thread!                     Offended? Click here
"Yelling out of cars, turning your speakers out the window to blast your music onto the street, setting off M-80 firecrackers, firing automatic weapons into the airâ€"these are all well and good. But none of them create a merry atmosphere of insouciance and bonhomie quite like a revving motorcycle.

scott_araujo

#3
May 16, 2010, 09:33:18 PM
What you're doing is feasible but you could also just get a smaller, lighter battery.  There are some folks on this board who have done it.  Once you add all the extra wiring you may not save much with two smaller batteries

You could also get the super light SpeedCell:
http://www.motowheels.com/italian/myProducts.cfm?parentcategoryid=915|Batteries%20and%20Battery%20Accessories&productID=6814&showDetail=1&categoryID=915|Batteries%20and%20Battery%20Accessories&vendoridtodisplay=0&filterFor=&collection
http://ducatimonsterforum.org/index.php?topic=27995.0

Scott

Speeddog

#4
May 17, 2010, 08:38:27 AM
There's issues with charging batteries that are connected in parallel.

I don't know how the dual-battery trucks deal with it, but that might be a good place to start.
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krista

#5
May 19, 2010, 08:56:23 PM
Get some thousand+ strand 4ga concert speaker cable and use that for all your connections and all will be ok. Frame to (-), (-) to (-), (+) to (+), (+) to solenoid, solenoid to starter. And engine to frame, too, if you're anal like that.
Krista Kelley ... autist formerly known as chris
official nerd for ca-cycleworks.com

ducatiz

#6
May 20, 2010, 03:01:46 AM
4 ga?  Lol that will add 10lbs to the bike!

My goal would be to distribute weight IF reasonable and keep the same overall Ah/crank capacity. 

Would be nice to get that 15 lb battery low on the frame
Check out my oil filter forensics thread!                     Offended? Click here
"Yelling out of cars, turning your speakers out the window to blast your music onto the street, setting off M-80 firecrackers, firing automatic weapons into the airâ€"these are all well and good. But none of them create a merry atmosphere of insouciance and bonhomie quite like a revving motorcycle.

suzyj

#7
May 20, 2010, 03:35:51 AM
Here's a thought.  Rather than using two parallel 12V batteries, and having to ensure they charge evenly etc, why not use two series connected 6V batteries...


2007 Monster 695 with a few mods.
2013 Piaggio Typhoon 50 2 stroke speed demon.

ducpainter

#8
May 20, 2010, 03:40:15 AM
Here's another thought...

why not leave well enough alone? :P
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
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ducatiz

#9
May 20, 2010, 04:10:01 AM
Nate I have to assume that's a crank reply given the amount of mods around here

I checked on the dual battery trucks and there are a few ways but the most common is the use of an battery isolator on the charge wire from the reg.  It allows the two batteries to be used and charged wo equalizing the wiring. It also allows you to use diff batteries.  I had one on the vw camper I had in college for the electric heater I put in...

Hmm
Check out my oil filter forensics thread!                     Offended? Click here
"Yelling out of cars, turning your speakers out the window to blast your music onto the street, setting off M-80 firecrackers, firing automatic weapons into the airâ€"these are all well and good. But none of them create a merry atmosphere of insouciance and bonhomie quite like a revving motorcycle.

ducatiz

#10
May 20, 2010, 04:12:27 AM
The downside is that they tend to be heavuy and I'd still need a second starter solenoid for batt#2.

Check out my oil filter forensics thread!                     Offended? Click here
"Yelling out of cars, turning your speakers out the window to blast your music onto the street, setting off M-80 firecrackers, firing automatic weapons into the airâ€"these are all well and good. But none of them create a merry atmosphere of insouciance and bonhomie quite like a revving motorcycle.

ducpainter

#11
May 20, 2010, 04:18:19 AM
Quote from: ducatiz on May 20, 2010, 04:10:01 AM
Nate I have to assume that's a crank reply given the amount of mods around here

I checked on the dual battery trucks and there are a few ways but the most common is the use of an battery isolator on the charge wire from the reg.  It allows the two batteries to be used and charged wo equalizing the wiring. It also allows you to use diff batteries.  I had one on the vw camper I had in college for the electric heater I put in...

Hmm
Of course it is, but what started out intended as a relatively simple mod has gotten pretty complicated.

Is it worth it?


Seriously.

"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


ducatiz

#12
May 20, 2010, 04:35:03 AM
It might be worth it if the weight advantage is there.

That still isn't settled.  I might actually look into it the solid state isolators are smaller than I thought.  And the 4ga wire is overkill but functional.

If it drops a couple of lbs and I can move half of the batt weight a foot lower it would be an interesting option for the track bike.  I haven't moved up to a bump starter
Check out my oil filter forensics thread!                     Offended? Click here
"Yelling out of cars, turning your speakers out the window to blast your music onto the street, setting off M-80 firecrackers, firing automatic weapons into the airâ€"these are all well and good. But none of them create a merry atmosphere of insouciance and bonhomie quite like a revving motorcycle.

cyrus buelton

#13
May 20, 2010, 04:49:57 AM
Just hook up 5 D batteries to keep it going and push start each time
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1999 M750 (joint ownership)
2004 S4r (mineeee)
2008 KLR650 (wifey's bike, but I steal it)

ducatiz

#14
May 20, 2010, 04:53:44 AM
Jud gimme your address.  Gonna mail you a shoe.  You can stuff it.  Otherwise ill do it forcibly when I see you.

Anyhow that woulkd only be 7.5 v.  Not enough
Check out my oil filter forensics thread!                     Offended? Click here
"Yelling out of cars, turning your speakers out the window to blast your music onto the street, setting off M-80 firecrackers, firing automatic weapons into the airâ€"these are all well and good. But none of them create a merry atmosphere of insouciance and bonhomie quite like a revving motorcycle.
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