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Improving Your Mokai

Shop Talk => Engine Performance and Modifications => Topic started by: stoplight on March 01, 2017, 02:09:28 PM

Title: Mokai battery
Post by: stoplight 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.
Title: Re: Mokai battery
Post by: Painlesstom 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
Title: Re: Mokai battery
Post by: The Man on March 01, 2017, 05:35:19 PM
Tom installed mine with Velcro, and it works great!
Title: Re: Mokai battery
Post by: The Man on March 01, 2017, 06:07:45 PM
Very easy to remove!
Title: Re: Mokai battery
Post by: stoplight on March 01, 2017, 07:19:39 PM
That's good to know. It was just a crazy thought that crossed my mind.
Title: Re: Mokai battery
Post by: happul3 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.
Title: Re: Mokai battery
Post by: Painlesstom 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+.
Title: Re: Mokai battery
Post by: happul3 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)? 
Title: Re: Mokai battery
Post by: Painlesstom 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.
Title: Re: Mokai battery
Post by: happul3 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.
Title: Re: Mokai battery
Post by: Painlesstom 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.
Title: Re: Mokai battery
Post by: happul3 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

Title: Re: Mokai battery
Post by: Painlesstom 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.
Title: Re: Mokai battery
Post by: happul3 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.
Title: Re: Mokai battery
Post by: Painlesstom 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 
Title: Re: Mokai battery
Post by: happul3 on March 05, 2017, 09:00:15 AM
Nicely packaged battery. Not clear if it incorporates a BMS and/or requires external balancing periodically. Probably can find out by calling the tall free number - if they put together the battery to be drop-in replacement for Pb, they supposed to give sufficient info about using it.
Title: Re: Mokai battery
Post by: 2mokaiman on March 05, 2017, 10:13:06 PM
I have used this SHORAI LFX07L2-BS12 for the last 2 years in both of my mokais. I have the KX21 engines in my mokais and they have a higher compression ratio than the EX21 and much harder to turn over. These batteries crank it over with ease. I have had no problems with them. The best feature about them is they weigh just under 1 pound. That is the reason I bought them in the first place. Weight is a big factor with the mokai speed. You cut it where you can. But after having these batteries and experiencing their performance I would never go back to a lead acid type. You just can't beat the size, weight & performance of this battery. They are worth the extra price you pay for them.  \./8
Title: Re: Mokai battery
Post by: Painlesstom on March 06, 2017, 07:18:06 AM
Nicely packaged battery. Not clear if it incorporates a BMS and/or requires external balancing periodically. Probably can find out by calling the tall free number - if they put together the battery to be drop-in replacement for Pb, they supposed to give sufficient info about using it.

There is no balance port, so there is no way to balance charge regardless. They were designed to directly replace a Pb battery and the only requirements given were charging voltage should be above 13.1v at idle and no more than 15.2v at full throttle. Like Tim said, they work great and he's been using them for years.
Title: Re: Mokai battery
Post by: happul3 on March 06, 2017, 08:10:09 AM
Thanks 2Mokaiman! Good to know that my speculation about using 4s LFP turned out to be reality. Do you use an external charger or just a regular use of battery in Mokai is sufficient to maintain it?

There is no balance port, so there is no way to balance charge regardless.

I think there is a balance port actually. In fact, Shorai recommends using specially designed charger if usage is less than couple times a month and  "The Shorai BMS01 charger or the Hyperion EOS 720 chargers are the suggested balance type chargers". If you look at BMS01 pictures you can see 5 pin balancing connector. 
Title: Re: Mokai battery
Post by: Painlesstom on March 06, 2017, 08:51:31 AM
Ahh You are right, I stand corrected then..  :-[
Title: Re: Mokai battery
Post by: 2mokaiman on March 06, 2017, 08:56:10 PM
When I bought these batteries I also bought the special charger that is specific to this battery. On the top front center is a small 5 pin charging port closed in by a plastic flap. I will try to upload photo to show it. However You really don't need this charger because the engine charges this battery in short order. I never used it. The battery comes with a sufficient charge that starts the engine just fine and then just let it run for a few minutes and your good to go. This battery really holds it's charge quite well. After letting it sit for 4 months it only dropped
3/10th of a volt. I will also try to upload a photo of the charger connected to the batter so you have a clearer understanding of this. Glad I could help

Title: Re: Mokai battery
Post by: happul3 on March 07, 2017, 12:00:12 PM
Thanks a lot for pics and for sharing your experience. Sounds like a good upgrade.

By the way, since you already have balancing charger it is not a bad idea to use it periodically. If your battery gets out of balance, charging it from engine does not guarantee that  all cells are charging properly. Let's say that the dumb charging circuit is producing 14.4V maximum. Normally, it is split between 4 cells equally, meaning that each cell is at ~3.6V each max, which is fine. But consider the following scenario, one cell somehow gets discharged more than three others. When charging at 14.4V total, the split is unequal, driving normal cells above target voltage and weak cell not getting there at all. In this scenario, charging results in a seemingly correct voltage, but one cell is undercharged and three are overcharged (already unhealthy situation). Suppose the battery is used again, taking equal current from every cell. This can possibly driving undercharged cell below its designated minimum voltage, which is now unhealthy for that cell. Subsequent charging/discharging cycles further increase disbalance without reflecting in charged battery voltage, and eventually produce enough damage to individual cells to render the whole battery useless. That's why people use balance chargers, which ensure that each cell gets exactly to the target voltage.

I want to stress that the progressive disbalance scenario I outlined above is not a certainty. It is also possible that, depending on charging circuit, cell capacities, and usage pattern, the disbalance is self-limiting and may never becomes a problem, like in lead batteries. But if balance charger is already available, I'd just use it once every month or two. 
Title: Re: Mokai battery
Post by: Painlesstom on March 07, 2017, 12:48:25 PM
He's aware of that, but even after a couple years of using these, his balance charger shows nothing out of balance. Seem to be pretty good batteries, best bang for the buck. In my experience with Li batteries, it's the discharge and charge cycle that leads to eventual imbalance. Especially if there was a substantial discharge with a large load. Starting the Mokai a couple times during the day, and running full throttle otherwise, pretty much keeps it topped off all the time and there is never any deep discharge going on to affect balance. Good to check it once in a while, but not something I wouldn't worry about under normal conditions. Certainly can't hurt if one wants to keep tabs on it and plug it in when they feel the need.
Title: Re: Mokai battery
Post by: strick on October 07, 2019, 09:30:34 PM
Question about those terminals...slip on is this even legal to use in a boat or did you change them somehow to post and nut ?

Strick
Title: Re: Mokai battery
Post by: Painlesstom on October 07, 2019, 09:46:24 PM
Manufacturer could be bound by rules about what they can and can't use, but what you do with your boat is up to you unless there is some inspection for registration that would dictate otherwise.
Title: Re: Mokai battery
Post by: strick on October 08, 2019, 08:15:26 PM
The reason I ask is because I recently bought one of those 10 amp batteries but the terminals are slip on maybe I can drill a hole in the middle and put a nut in them.

Strick
Title: Re: Mokai battery
Post by: Painlesstom on October 08, 2019, 08:18:03 PM
Nothing wrong with slip connectors, I use them in all my conversions and have for years. Not problem. Current draw isn't an issue and I've seen no problem with them. Not something I'd worry about.