Conversion to Lithium Ion battery power...

[MetroMan]

As you guys may or may not know, my kayak (OK Torque) is recommended to be powered with a 12v, group 24 deep cycle battery. While this powers the kayak just fine and dandy, transporting this class of battery can be a pain in the butt at times. A group 24 battery will weigh in the 50lb range. My current unit weighs 53lbs to be exact. I was able to manage just fine, but I wanted something lighter without sacrificing power capacity. I began researching lithium ion battery solutions. I've spent countless hours of reading thread after thread on various electric vehicle and electric bike message boards...also gained useful information from sailboat forums.

I found a website where I could order a 60aH 12v LiFePO4 (lithium iron phosphate) battery pre-assembled and ready to go, weighing a mere 20lbs. This battery cost $569, not including shipping. Definitely not for the faint of heart or wallet. I wanted a cheaper solution. I began research on building my own lithium battery.

I went through plenty of email conversations with people from china, representing various battery manufacturers. All of the LiFePO4 cells come from china. I figured I'd explore the option of buying direct. This was difficult...downright frustrating at times. The time difference made timely correspondence difficult. The language barrier made emails hard to comprehend. And overall was the trust factor. Every question I asked was pretty much responded to with " yes, no problem. We can make for you." Buying direct from manufacturers is catered to distributors, not single item consumers. So finding a supplier to sell a single battery was one hurdle to jump. Even still, shipping from china is a killer...both in cost and time. I'm talking like a few months from some suppliers. These transactions mostly require you setting up a bank/wire transfer...ehhh. I decided to search domestically.

After thoroughly researching which brand to buy (ThunderSky), I decided to risk the purchase through a guy/company in San Fancisco. Www.alliancerenewableenergy.com. I did some online researching about this company, with mixed results...but I gave it a shot anyways. Although it took longer than it should have (with horrible communication on their behalf) I got my product after mailing them a certified check.

Assembling the pack was rather straight forward. I wired the four cells in series (3.2v each). I got my battery terminal bolts and other connectors from both radio shack and the local hardware stores. I secured the cells together using heavy duty zip ties. I wanted something that allowed me to easily swap out a cell should I need to do so.

Since lithium batteries are sensitive to being over discharged, I wired up a control board that is designed to protect the cells.



This circuit board protects the battery pack from over discharge by cutting power once it reaches 9.2v. It also protects it from overdrawn current...it'll shut down if it senses a 30amp draw. The torque motor pulls 25a max at full power. I got everything all soldered up, and I used Andersen PowerPole connectors for all of my wire connections. These connectors are great. I also installed a Doc Wattson meter, which tells me pertinent information such as amp-hrs used, current load, and pattern charge that I have remaining.

Before hitting the water, I did a test on land. I was testing. Both the battery, as well as my newly installed/upgraded/relocated trolling motor plug (Marinco). It worked out just fine.

http://youtu.be/nVyReEDQuG8



Excited to have my battery constructed...and my trolling motor plug replaced, I was ready to get on the water. Wanting to explore water closer to home, I went to launch at a local spot on Jam 16th...only to find THIS



Not only was the ramp iced over, but the river had a good bit of ice too. I opted to delay my testing. I was finally able to give it another shot on Sunday afternoon. The video below shows my trials...

http://youtu.be/cT_Jw74WQ2Q (2:26 is when I realized something was wrong...)

When I spoke to the vendor of my lil circuit board back in the planning phases, I asked him what gauge wire I needed to go to the individual cells. He said small, 14ga wire would be fine. I mistakenly used this small gauge wire to the pos & neg outputs from the battery pack. Once the juice got flowing, the heat generated burned the insulation. Notice the look on my face when I realized something was wrong. Notice the two [now] black wires in the pic below...



Oops. I redid the wiring that night with 10ga wires, which is originally used throughout the system. I was able to get out on the water yesterday...

http://youtu.be/sosDSYALxcM

[MetroMan]

The wiring looks complex, but it was pretty straight forward. I was on the water yesterday for a couple of hours and used around 20% of the battery's capacity. I have materials to construct a custom box for the battery. Well...I plan on trying at least. I will be using fiberglass material for this enclosure. As of now, I just have the battery sitting in the bow storage hatch as is.

Freeing up the center storage area on my kayak was a big deal. This area was originally designed to house the Group 24 battery. I was fine with just sitting my plano boxes in the storage area behind my seat, but I am happy to have some dry, below deck storage now that is readily accessible.

My old trolling motor plug was really worn out.



It would often short out during trips last season....requiring me to lean back and fumble with it. This new plug is much more sturdy, and in a more convenient location.

[J.A. Veil]

My old trolling motor plug was really worn out.


It would often short out during trips last season....requiring me to lean back and fumble with it. This new plug is much more sturdy, and in a more convenient location.

I installed a Minnkota trolling motor on my Scout center console boat last summer. I had all sorts of problems dealing with the wiring. A list of my frustrations can be seen at http://www.tidalfish.com/forums/show...trolling+motor.

I eventually created a portable battery box that had a Minnkota female plug receptacle on the outside. I could plug the male lead from the motor into the box. During an on-water trial, it ran for a few minutes, then shut off. The wire and connectors were very hot to the touch.

I showed the setup to Jim Maier at BOE Marine. He told me I had wired everything correctly but that due to a twist in the heavy 10-gauge wire I used, not all the current was making it through to the engine. Instead, it was getting lost as heat.

He suggested that I rewire the motor cable directly to the battery. I did that plus added a circuit breaker inside the box. Now the system works fine.

For me, electrical circuits remain somewhat of a mystery. I wish you good luck in getting things straightened out.

As a side note, your mentioned that all the lithium batteries you considered came from China. To some extent, that is because China is one of the few countries in the world with abundant lithium mineral reserves. From an energy policy perspective, there has been some concern that China and a few other countries might create an "OPEC for Lithium" to control the price of lithium in the future.

[MetroMan]

I wish you good luck in getting things straightened out.

As a side note, your mentioned that all the lithium batteries you considered came from China. To some extent, that is because China is one of the few countries in the world with abundant lithium mineral reserves. From an energy policy perspective, there has been some concern that China and a few other countries might create an "OPEC for Lithium" to control the price of lithium in the future.

Thats interesting information. I didn't know that!

I got everything ironed out, as seen in the last vid I linked. Now I just need to catch fish!!

[MetroMan]

Seen below is one of my high tech wiring diagrams I made here at work...

[Memory Maker]

Seen below is one of my high tech wiring diagrams I made here at work...

Wow ........ even color coded

[On the fly]

So how much did you save in $$$ by building it yourself?

[tufnik]

When you load the prop, the current goes up. Any idea of the current draw? Got a amp meter? My guess is you'll pull 25-35 amps at full throttle.

On my Trident and Minn Kota (with lead acid batt), I estimate my pull is 30+ amps at full throttle. I use 12 ga wire, which can handle well over 30 amps. I may go to 14 ga, but will have to recalculate based on getting a new motor with a variable speed control.

At 20 pounds, capacity is 60 AH. That's pretty good. With greater efficiency than the lead acid batts, your li-ion with 60 AH may be good for my application. How far down can you discharge the batt? I'm guessing down to 10-20%. I believe the voltage stays up there pretty well too, so good power is still there.

[MetroMan]

So how much did you save in $$$ by building it yourself?

It ended up costing me just around $400 in the end (shipping included). Most of the peripheral accessories are cheap, like bolts, wires, ring terminals, etc.

So I saved over $200 by taking the DIY route.

[MetroMan]

When you load the prop, the current goes up. Any idea of the current draw? Got a amp meter? My guess is you'll pull 25-35 amps at full throttle.

On my Trident and Minn Kota (with lead acid batt), I estimate my pull is 30+ amps at full throttle. I use 12 ga wire, which can handle well over 30 amps. I may go to 14 ga, but will have to recalculate based on getting a new motor with a variable speed control.

At 20 pounds, capacity is 60 AH. That's pretty good. With greater efficiency than the lead acid batts, your li-ion with 60 AH may be good for my application. How far down can you discharge the batt? I'm guessing down to 10-20%. I believe the voltage stays up there pretty well too, so good power is still there.

Tufnik,

You are pretty close in your estimates. At full throttle, I hover around the 30A mark. I've seen 29-31, with the highest numbers peaking when I slam the throttle to full speed. Its quite amazing to see the drop in current draw you get just by backing off the throttle even slightly. The conservation of energy by far outweighs the small speed gain you get by running at max throttle. The battery can be safely ran down to 10%. (I forget where I learned that, but I remember reading about people running them down that low). To be safe, I plan to have 20% as my threshold. That gives me 48usable amp hours. This is more usable aH than my AGM battery. It delivers almost full voltage till it dies.

I am using a doc wattson meter. It shows quite a bit of information. Most important to me thus far are current draw, and aH. It shows how many amp hours have been consumed. Having that information tells me exactly how many aH I have remaining.

I hope to get out more to get more accurate, experimental run times...opposed to calculated numbers. It's hard to do so while fishing. Realistically, unless you're launching far from your fishing spot, you spend most of the time drifting...or anchored up. The two times I've ran my battery dead was 1. Fishing the susky with moc in tow, and 2. Fishing with foursteps (we launched from the G dock...I towed him to the east side rock pile...we fished there..Luther towed him all the way back. LONG haul)

Next on the "to do" list is to build the fiberglass enclosure...

[tufnik]

That's about the most I've used on my outings, 50 AH. My 85 AH batt weighs 50+ pounds. So, I'm interested in your set-up.

Do you use a circuit breaker? I have the Minn Kota device, and it works well. On several occasions, the weeds at Mattawoman stopped the prop. The auto-reset circuit breaker worked great. I had to wait only 2-3 up to 10 seconds before the circuit was reconnected.

Yeah, I'd like to see how you enclose the thing. Do you have a waterproof design in mind?

[MetroMan]

No traditional circuit breaker (I plan to add one later), but the circuit board in the pic serves the same purpose. Check it out here...

http://www.batteryspace.com/PCM-with...30A-limit.aspx



So far, I am not planning on making a waterproof enclosure...

[tufnik]

Looks good.

Hey, have you looked into a step down transformer? With this transformer circuit, I'm thinking of using the 24-v torqeedo battery for a Minn Koto 12v motor. Of course, it'll bump the total costs up, but you'll have a waterproof floating $400 battery. It's only a thought right now.

[MetroMan]

Since I have planned to keep the power supply at 12v, I have never looked into a stepdown transformer. I am pretty sure the torqueedo uses 29.6V Lithium manganese batteries.

[MetroMan]

Just an update. The battery has been working GREAT. I went out on the Patuxent on Saturday morning (didnt fish though). I love having the Doc Wattson meter to be able to analyze critical things such as amp draw and amp hours used. Its pretty amazing how non-linear the amp draw incrases as the throttle increases. At full power with the lever at the max stop, the motor draws about 29amps. Back off just a little bit, and that draw drops down to around 17-18A. The difference in speed is pretty negligible...so needless to say I'll be staying away from absolute full throttle to extend my range.

Also, it is working out just fine in the bow storage hatch. I love having the free storage space in what used to be the battery box mid-cockpit. The has increased the convenience factor a whole lot. I have a dry bag that I will be modifying for use with the battery.