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Offline stoplight

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Mokai battery
« on: March 01, 2017, 02:09:28 PM »
Ok so spring is just around the corner and I've started getting things and ideas ready for the upcoming  season. I need two new batteries and as I sat in my shop thinking about that I looked at the multitude of Dewalt batteries  I have for various cordless power tools and thought I wonder if one of the bigger ones would start a mokai?  Now I know absolutely nothing about electrical things but I think  a couple of you guys on here do. I like the idea of being able the easily/quickly remove it in between use and drop it on a charger.

Offline Painlesstom

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Re: Mokai battery
« Reply #1 on: March 01, 2017, 05:29:23 PM »
I wouldn't recommend using a NiMh, or Lithium type battery as the charging system has no sensing circuitry to prevent overcharging. I use 12v 10ah AGM batteries in mine, they hold a charge very well and last for years.


http://www.ebay.com/itm/111268132777?_trksid=p2060353.m2749.l2649&var=410283354902&ssPageName=STRK%3AMEBIDX%3AIT
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Offline The Man

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Re: Mokai battery
« Reply #2 on: March 01, 2017, 05:35:19 PM »
Tom installed mine with Velcro, and it works great!

Offline The Man

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Re: Mokai battery
« Reply #3 on: March 01, 2017, 06:07:45 PM »
Very easy to remove!

Offline stoplight

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Re: Mokai battery
« Reply #4 on: March 01, 2017, 07:19:39 PM »
That's good to know. It was just a crazy thought that crossed my mind.

Offline happul3

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Re: Mokai battery
« Reply #5 on: March 01, 2017, 07:29:46 PM »
Personally, I am happy with stock battery, but 4s cell LiFePO4 has max charge voltage 14.4V, basically the same as charging circuit supplies. They are also supposed to be much safer and last longer than regular Li. So it might be ok as drop-in replacement if someone wants to save about 4 lbs (5.5 lbs 6Ah stock battery vs 1.5 lbs 4s2p 6Ah LFP).

In comparison, I would not recommend NiMH as it requires special charging circuit, weight savings aren't so great, and majority of NiMH cells suffer from relatively fast self-discharge.

Offline Painlesstom

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Re: Mokai battery
« Reply #6 on: March 01, 2017, 07:59:33 PM »
Personally, I am happy with stock battery, but 4s cell LiFePO4 has max charge voltage 14.4V, basically the same as charging circuit supplies. They are also supposed to be much safer and last longer than regular Li. So it might be ok as drop-in replacement if someone wants to save about 4 lbs (5.5 lbs 6Ah stock battery vs 1.5 lbs 4s2p 6Ah LFP).

In comparison, I would not recommend NiMH as it requires special charging circuit, weight savings aren't so great, and majority of NiMH cells suffer from relatively fast self-discharge.

On boats that came stock with the Subaru Electric Start engines, the 40w system has the regulator which does keep things at 14.4v. BUT, anyone with a conversion engine came with the 15w system and a rectifier only; that system will get up to 18v+.
Tom

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Offline happul3

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Re: Mokai battery
« Reply #7 on: March 02, 2017, 01:27:59 PM »
. BUT, anyone with a conversion engine came with the 15w system and a rectifier only; that system will get up to 18v+.

I did not know that. Thanks for clarification. By the way, 18V is not healthy for Pb battery. My lawn tractor had unregulated 16-18V  and that resulted in need to replace the battery every couple of years until I reduced the voltage to 14V. AFAIK,  AGMs are more robust if charging current is not excessive (they convert hydrogen and oxygen back to water), but why not install a regulator ($20 part)? 

Offline Painlesstom

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Re: Mokai battery
« Reply #8 on: March 02, 2017, 05:14:53 PM »
Swapping in the regulator is no problem at all, I just wanted to put that out there in case anyone decided to jump the gun, and go Lithium, without knowing that there will be problems. I didn't like 18v on mine so they all have regulators now, compatible with the 15w charging coil so nothing to change there.
Tom

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Offline happul3

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Re: Mokai battery
« Reply #9 on: March 02, 2017, 06:46:00 PM »
I agree about Li.

To re-iterate for folks not familiar with these battery types, Li-ion (aka Lipo) is absolutely no-go because of possibility of spontaneous fire near gas tank even if a regulator is present. On the other hand, 4 cell LFP (aka LiFePO4) might be ok provided that a ~14.4V regulator is present.

Offline Painlesstom

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Re: Mokai battery
« Reply #10 on: March 03, 2017, 09:52:37 AM »
Lithiom Ion (Li-ion) and Lithium Polymer (Lipo) are two different chemistry types, they are not the same. I use LiFe on a regular basis for my large scale planes, but even still I balance charge those every time. Since these batteries are made up of single cells combined in series to make a pack, they need to be balance charged and the Subaru charging system doesn't accommodate that requirement. There might be some commercial battery that is meant for standard charging systems, my experience with these battery types is revolved around the RC side.
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Offline happul3

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Re: Mokai battery
« Reply #11 on: March 03, 2017, 10:31:02 AM »
I agree that (external) balancing might be required at some intervals. Nonetheless, the 4s LFP might work as drop-in replacement. How often it will require maintenance/balancing that is an unknown.

Lithiom Ion (Li-ion) and Lithium Polymer (Lipo) are two different chemistry types, they are not the same.

That is not correct. Their chemistry is the same, it is only the separator/filler/case material that is different. Lipo is still Li-ion battery, which was renamed (marketing?).

From wikipedia:

A lithium polymer battery, or more correctly lithium-ion polymer battery (abbreviated variously as LiPo, LIP, Li-poly and others), is a rechargeable battery of lithium-ion technology in a pouch format. Unlike cylindrical and prismatic cells, LiPos come in a soft package or pouch, which makes them lighter but also less rigid.

The designation "lithium polymer" has caused confusion among battery users because it can be interpreted in two ways. Originally, "lithium polymer" represented a developing technology using a polymer electrolyte instead of the more common liquid electrolyte. The result is a "plastic" cell, which theoretically could be thin, flexible, and manufactured in different shapes, without risk of electrolyte leakage. The technology has not been fully developed and commercialized[1][2] and research is ongoing.[3][4][5]

The second meaning appeared after some manufacturers applied the "polymer" designation to lithium-ion cells contained in a non-rigid pouch format. This is currently the most popular use, in which "polymer" refers more to a "polymer casing" (that is, the soft, external container) rather than a "polymer electrolyte". While the design is usually flat, and lightweight, it is not truly a polymer cell, since the electrolyte is still in liquid form, although it may be "plasticized" or "gelled" through a polymer additive.[6] These cells are sometimes designated as "LiPo"; however, from a technological point of view, they are the same as the ones marketed simply as "Li-ion", since the underlying electrochemistry is the same.[6]



Here is another informative article on the subject:   
http://batteryuniversity.com/learn/article/the_li_polymer_battery_substance_or_hype


Offline Painlesstom

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Re: Mokai battery
« Reply #12 on: March 03, 2017, 05:51:38 PM »
Apparently there is some debate about that, but I understand the differences now that you made me do more homework. LOL

Lithium-Ion Batteries began their development in 1912. However, they did not become popular until they were adopted by Sony in 1991. Lithium Ion Batteries have high energy-densities and cost less than lithium-polymer batteries. In addition, they do not require priming when first used and have a low self-discharge. However, lithium-ion batteries do suffer from aging even when not in use.

Lithium-polymer batteries can be dated back to the 1970s. Their first design included a dry solid polymer electrolyte that resembled a plastic film. Therefore, this type of battery can result in credit card thin designs while still holding relatively good battery life. In addition, lithium-polymer batteries are very lightweight and have improved safety. However, these batteries will cost more to manufacture and have a worse energy density than lithium-ion batteries.
Tom

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Offline happul3

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Re: Mokai battery
« Reply #13 on: March 03, 2017, 10:22:36 PM »
 
Lithium-polymer batteries can be dated back to the 1970s. Their first design included a dry solid polymer electrolyte that resembled a plastic film. Therefore, this type of battery can result in credit card thin designs while still holding relatively good battery life. In addition, lithium-polymer batteries are very lightweight and have improved safety. However, these batteries will cost more to manufacture and have a worse energy density than lithium-ion batteries.

Yep, that's the great promise of lithium polymer tech that unfortunately still have not made it to the market.

Offline Painlesstom

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Re: Mokai battery
« Reply #14 on: March 04, 2017, 11:10:52 PM »
This would be the perfect battery to use, intended for use in applications like this it would be idea. Would still require a regulated charging system though. http://shoraipower.com/lfx07l2-bs12-p46 
Tom

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