12V Lithium Ion Battery for starting

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12V Lithium Ion Battery for starting

Post by Whiskey7 » Mon May 01, 2017 3:42 am

So here's my setup on my 44MB. I have a dedicated 12v battery which is only used for turning the starter motor. It must be charged from an external source as the generator is 6v and runs the electrics for ignition, lights etc and charges the 6V battery. Why do I have this system? My engine rebuilder recommended it and has installed it on a number of jeeps and says it is a good compromise between the problems with 6v starting and converting everything to 12v. Please let's not get into a discussion on 6v V 12v, because I would like your help on a mod I am considering to my current setup.

The 12v lead acid battery was mounted on a temporary battery tray located below the regulator and secured at one point only to the frame rail. It's a tight fit there and the battery is also very heavy. Hence I am considering a move to lithium ion. The benefits are lighter, smaller and more starts between recharges. I was also thinking of relocating this battery to the right toolbox. I have a repro tub so I don't mind drilling holes in it. This would keep the engine Bay looking more original and accessing the 12v battery for charging/jumping much easier. I was going to ground the negative terminal to one of the tub to frame mounting bolts (under the frame) and run the positive underneath the tub to the starter switch.

2 questions - Has anyone done this or similar and what gauge cable do I need for the + terminal to starter switch.

Thoughts etc?


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Re: 12V Lithium Ion Battery for starting

Post by Wolfman » Mon May 01, 2017 5:31 am

I will by-pass why. You have already made up your mind.
Don't know much about lithium ion batteries other than what I have seen on the evening news. They catch fire and burn things up.
As for putting the battery in the tool box. No problem other than the distance.
The longer the run, the more voltage drop you will have. That would defeat the purpose of going to 12 volt.
I would use a 1-0 cable. Larger would be over kill.Too bulky and stiff and smaller would contribute to the voltage drop problem.
A lot of off the shelf cables these days are 4 gauge. That would be too light for an 8 to 10 foot run.
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Re: 12V Lithium Ion Battery for starting

Post by W. Winget » Mon May 01, 2017 6:48 am

Not sure if there is a retail device (I'm sure its out there) with a transformer to convert 6 to 12 volt, but if you put that device in line with your 6V system you could charge your Lithium battery off your vehicles 6V system, then you'd have one less thing to fumble with.

Interesting concept, I find it easier to just keep it 12V and use the older two wire GM Alt with one wire fed back on itself making it a one wire system. Headlights, some tailight bulbs soldered in, 2 dash bulbs and a fuel gauge are not that hard to replace, and EVERY friends 6 Volter seems to miss multiple parades or events, mine's never had a problem with exception of ONE starter in 25 years now (which is a LONG time for any starter)

As to wires from the rear, it's not going to take much or heavy cables as it's 12V, so check with the local RV store whom will have a decent selection of 12V cables or a reel to cut to length.
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Re: 12V Lithium Ion Battery for starting

Post by ndnile » Mon May 01, 2017 8:18 pm

Wolfman wrote:As for putting the battery in the tool box. No problem other than the distance.
The longer the run, the more voltage drop you will have. That would defeat the purpose of going to 12 volt.
Very true, but lets remember that a handful of cars now keep their battery in the rear trunk for weight distribution, so it is doable, and they are cranking a much higher compression engine than our beloved L134. I know Audi does this and I think BMW does too.

For the record, mine does just fine on 6V, but then California isn't quite the cold weather battery test ground of the world anyway.

Sorry to hijack your thread, but the nerd in me has previously thought of how to deal with this sort of thing. It is easier to regulate a DC voltage down than it is to increase it. If I was doing it from scratch I would have a single 12VDC battery. I would run the starter and headlights at 12VDC (I want the headlights brighter anyway). Anything that is left is low power and would be easy to run off of a small 12-to-6 VDC converter. Best of all worlds.
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Re: 12V Lithium Ion Battery for starting

Post by Whiskey7 » Tue May 02, 2017 4:21 am

Thanks for the reply guys - all give food for thought! Will let you know what I do with a pic or two.

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Re: 12V Lithium Ion Battery for starting

Post by Wolfman » Tue May 02, 2017 4:25 am

The big difference between the old L-134 and the modern cars is the starter.
The old starters draw amp wise was 300 to 400 amps. The new high torque starters are only pulling 180 amps. Considerably less. Why the new cars get away with lighter cables and W*7 needs the heavier cable.
No need for two cables from the back. The 6 and 12 volt setup can use a common ground. The frame. Be sure there are good ground straps in place, especially between the frame and engine block.
The B+ side of 6 and 12 needs to be isolated from each other.
The 12 volt battery in the tool box needs to be connected to the starter switch, same as the 6 volt battery used to be. The 6 volt power lead to the amp gauge, that used to be connected to the starter switch, needs to go directly to the 6 volt battery. not the starter switch.
Don't see why a 6 to 12 volt inverter would not work to keep the 12 volt battery charged. Again, be sure all the frame to engine ground straps are in place. Don't want the inverter box to get caught up in the ground circuit side between 6 and 12. French fried is the term.
But just keeping the 12 volt charged for start only is an easier course. I have a young lady customer that inherited her fathers 6 volt Allis Chalmers C tractor. It has a 12 volt battery that she charges every so often. It has a magneto. No lights. All the 6 volt generator does is keep the fan belt tight. Starts with ease.
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Re: 12V Lithium Ion Battery for starting

Post by Whiskey7 » Wed May 03, 2017 8:08 am

Thanks Wolfman, good info. Probably going to use welding cable for the + due to its flexibility and the limited voltage drop. Be a couple of weeks before I get to this job.

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Re: 12V Lithium Ion Battery for starting

Post by Mark Tombleson » Wed May 03, 2017 9:23 am

Here is a chart showing various loads. http://www.wiringproducts.com/battery-c ... ty%20Chart

I have three batteries in my MZ-1... from the factory. 6v for the primary and two 12v running off the 12v 55amp generator via the 18W PTO. The 12v sit in two separate battery boxes behind the seat.

Now, when I'm not showing the MZ-1 I run a 1/0 from one of the back batteries to the starter switch and disconnect the cable from the 6v battery and the wire from the ammeter connecting them together so the 6v system is independent from the starter circuit.

I have done this since the fall of 2008... I think. :wink:
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Re: 12V Lithium Ion Battery for starting

Post by JIMN » Fri May 05, 2017 1:35 am

I have one jeep on 6 volts, and another converted to 12 volts.

Here are two more thoughts if you really don't want to start the motor with 6 volts :
To keep the appearance of the 6 volt battery in the tray, choose to run two 6 volt batteries. When you hit the foot starter, it could have a system that puts the two 6 volts in series and sends 12 volts to the starter. You would also add a selector switch to independently charge or operate either battery from your jeeps generator. you would still be running the rest of the jeep on 6 volts. In this instance I believe both 6 volt batteries would need to be the same size.
Or just run one 6 volt battery, and use the hand crank for starting. It only takes a quarter turn, and when it is warm, starts much easier than with the battery.
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Re: 12V Lithium Ion Battery for starting

Post by Wolfman » Fri May 05, 2017 5:26 am

Your idea is a valid one, JIMN.
Cosmetically, it would look the same ( almost) and original as W*7s 12 volt idea.
Positive cable from the battery under the hood to the negative post of battery in the rear.
Positive post from the battery in the rear to the starter switch.
DO NOT GROUND THE REAR BATTERY TO THE FRAME. Keep it isolated.
Remove the B+ load wire, to the amp gauge, from the starter switch and attach it to the positive post of the original front battery under the hood.
This will give 12 volts for starting. 6 volts to operate everything else on the jeep. Only the front battery would get charged during operation. You would still have to charge the rear 6 volt battery occasionally. All it is for, is to work in series with the front battery to start the jeep on 12 volts.
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Re: 12V Lithium Ion Battery for starting

Post by tamnalan » Fri May 05, 2017 6:19 am

My starter crapped out last year and I went a couple of months with just the hand crank. People walking by found it fascinating. They would often stop and watch. Sometimes I looked like an expert and it would start on the 1st or 2nd pull ... other times, well....
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Re: 12V Lithium Ion Battery for starting

Post by Whiskey7 » Fri May 05, 2017 11:45 pm

Hi Jimn

Your first idea has given me a plan - for now. The issue was locating the 12 volt starter battery somewhere. I'm actually going to put it on the battery tray and relocate the 6v to behind it on a separate shelf. I'm going to run it like that for this year and if it's all well and good I'll leave it if not I'll just convert to 12 and be done with it.

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Re: 12V Lithium Ion Battery for starting

Post by JIMN » Sat May 06, 2017 3:58 am

That will work.
Another thought. Almost nobody will ask why you have a 12 volt battery, but I am certain people would ask why you have two batteries.
I think if I was going to have a 12 volt battery, I would just make my charging system 12 volt.
Then you would have two choices. You could add separate resistors throughout the jeep to accomodate 6 volt components.
Or what I did was change all bulbs to 12 volt because I would get better lights. Always use a separate resistor for the fuel gauge. The coil should get its own resistor.
Mine does work good with 12 volt. It was easy to change the bulbs in the blackout lights, I just soldered in new bulbs. The headlights you just buy.
That being said, someday I might switch back to 6 volt for originality.
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Re: 12V Lithium Ion Battery for starting

Post by tamnalan » Sun May 07, 2017 3:43 pm

To me, the best single reason for going all-twelve volt is that you could then install a pair of seat heater pads under that canvas. Think how nice those heated seats would feel on a cool day with the top down!
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Re: 12V Lithium Ion Battery for starting

Post by Wolfman » Mon May 08, 2017 5:18 am

Better get two heaters, Alan.
Otherwise you will only get to drive your jeep on warm days.
Your wife be driving on the cold ones !
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