# Some thoughts on batteries for small tin boats.



## JNG (Apr 8, 2019)

I am blessed with an enormous amount of water within 30 minutes drive time for me. All are small lakes/ponds. The largest is 1000 acres and has no hp or speed limits. One is 180 acres and has a 10 hp limit. The rest (literally dozens and dozens of bodies of water) are just a few acres in size to about 70 or 80 acres. These small lakes/ponds are ALL electric motor and oar/paddle only. So I've always had a small jon boat setup for electric propulsion only plus my larger aluminum deep vee with an outboard for the 1000 acre lake. This small jon has always been a 1436 until last summer when I bought a 1542. While I was rigging the boat over the winter I decided to use different batteries this time around.

I've always used a single group 29/31 to power a 50 to 55 # thrust transom mount and a 40 to 55 # thrust bow mount. I typically would use a minimum of 25% to as much as 60 or more % of the batteries capacity. Using more than 50% of the capacity is very hard on batteries. It shortens the usable life of the battery greatly. Also at the end of the day, I would find myself using a higher speed setting on the motor just to maintain the same speed trolling. There have been many, many occasions where I struggled to get back to the dock because the battery had been drained down that far. 

Now a simple solution would be to buy 2 group 29/31 batteries and wire them up in parallel. However I decided to buy 2 golf cart batteries and wire them up in series. Both are identical 6 volt Interstate Extreme Cycle GC2-ECL-UTL batteries. Golf cart batteries are typically still true deep cycles unlike most of the 29/31's, which are 'dual use' batteries now. So by buying the golf cart batteries I now have proper deep cycles, higher amp hours, higher reserve capacity minutes, and slightly less weight. Here are the facts-

Interstate Extreme Cycle GC2-ECL-UTL
62# times 2 equals 124#
total of 225 amp hours
total of 447 reserve minutes

AutoZone 29DP-DL (typical battery of this type)
63.3# times 2 equals 126.6#
total of 212 amp hours
total of 420 reserve minutes

Now in actual use the few times I have taken the boat out this spring so far, I have been draining the batteries down anywhere from only 10% to 25% of capacity. And better yet, no loss of performance at the end of the day. This is with a new Motorguide R-3 55# digital variable speed transom mount and a Motorguide Xi-3 45# digital variable speed bow mount.

The subject of golf cart batts instead of 12 volt batts comes up every now and then on this forum and others on the 'net and the idea is usually dismissed because no one ever really tries this. Well I have now and so far I think it's a terrific idea for smaller electric only boats. Larger electric only boats that have the weight capacity for more batts and need higher amounts of thrust would likely benefit from a 36 volt system or one of the 48 volt RayElectric's. But I think it's a great idea for the 1232 through 1542 jons. Just my thoughts on the matter.


----------



## gnappi (Apr 12, 2019)

It sounds like you have a plan, but I wouldn't call a 15 footer exactly small. 

With such small waterways I'd think you could get by with less TM's and smaller batteries. I go all day on two 35Ah solar deep cycle batteries in my fully loaded "small" 10 footer and never go below 50% state of charge


----------



## JNG (Apr 13, 2019)

Two factors I deal with that are ' battery drainers '. One is I troll a lot for stocked rainbow trout. I also troll for saugereye. Almost constant running of the trolling motors for the entire time on the water. Number two is I live in the wind swept plains of Illinois. Invariably the wind is blowing when I'm fishing and there is lots of chop and waves to contend with.


----------



## EZ707 (Apr 15, 2019)

This was really helpfull as I’m starting to build a small boat for my smaller lakes in the area. I want to go fully electric this time around since I already have two Watersnake motors.


Sent from my iPhone using Tapatalk


----------



## muddywaders (Apr 15, 2019)

Great thread on The hull truth about guys building their own 12v lithium batteries.Lipo4 and Lito cells can be fully discharged with very little voltage loss,charge quickly and will last 20 000 cycles.Incredible energy/weight.


----------



## gnappi (Apr 16, 2019)

LifePo4 are going to break some new ground, but maybe not economically for a while. 

I've been watching the price and Amp hour ratings of the 38120 Lifepo cells, but so far to get the Ah of even a small 35Ah Deep cycle solar battery @ $56 each I'd have to get 16 38120's (4x 3.2V 8AH in series plus 12 more 4x3 in parallel to get 32Ah) at $300 (new) plus fabrication costs. Going for used cells will cut that by about half.

I don't know if the charge profile is compatible with AGM or lead acid chargers yet, so that's another expense if needed. 

So far my three 35Ah batteries are three years old, and at $56 each they are now disposable. I can't say how long it will be till Lifepo4 can replace AGM batteries but it's not soon enough for some, but 20,000 cycles will be L-O-N-G past my lifetime when they are economically feasible


----------



## JNG (Apr 19, 2019)

Been out a few more times since my last post. I still have not pulled the batteries down more than 25%. Last Saturday's trip was a doozy. Windy and I was pulling cranks for saugereye. Really expected to see a significant drop in the batteries state of charge after that trip. Nope, only pulled about 20% from the batteries. For frame of reference, I could not of trolled for as long as I did last Saturday using a single group 29/31. If I had, I would of had trouble getting back to the dock going into the wind and chop. With this setup, I had NO loss of power/speed last Saturday. I am completely satisfied with this battery arraignment. I'm very happy I decided to give it a try.


----------



## gnappi (Apr 23, 2019)

Two 6v batteries (@225Ah/2x62lb.=128lb.) shouldn't be any more than marginally better than two 12v group 29 batteries (@ 106Ah x2 =212Ah/126lb.) but if one of the 12v batteries shorts or has another issue, no problem, switch to the other, but if one of the 6v cells go kaput, it's dead in the water. 

For sure since the 6V batteries are smaller in footprint and more easily stowed, you found a sweet spot in battery use for your purposes.


----------



## onthewater102 (Apr 24, 2019)

I've read that golf cart batteries are a much higher quality than your typical off the shelf deep cycle battery but that you pay for it upfront. How much were those batteries if you don't mind me asking?

Each time I look the lithium ones come down a little in price, but never enough to make it palatable. Looks like a 200 AH 12v battery is running $2,000 but only weighs 72lbs...a lot of weight savings but way too much cash up front, not to mention the risks that come with using lithium.


----------



## JNG (Apr 28, 2019)

I bought the batteries last fall when I started wiring the boat. Without looking for the receipt and going by memory, I want to say I paid $153 +/- for each battery. I had no battery to turn in for the 'core charge'. So after tax and core charge the cost was just under $350 +/-. I'm still impressed by the performance. Last Friday was horrible with the wind and waves. Should not of gone out. Steady 30mph winds kicked up 2' waves that had whitecaps on my favorite lake. Only stayed out about 2 hrs. Was really expecting to see a much deeper state of discharge than what I did. I really had to run the trolling motor hard. Still only used 15% of capacity. I get the argument that two 12 volts are better than 6 volts if a battery goes bad on you while on the water. But in nearly 30 years on the water I have never had that happen.


----------



## Weldorthemagnificent (Apr 28, 2019)

It's a good idea. Lots of RV guys do this for dry camping. Wiring in series doubles the amp hours over two 12 volt in parallel. 

Sent from my CLT-L04 using Tapatalk


----------



## gnappi (May 8, 2019)

Weldorthemagnificent said:


> It's a good idea. Lots of RV guys do this for dry camping. Wiring in series doubles the amp hours over two 12 volt in parallel.



Research alert! 

Wiring in series doubles the voltage, AH stays the same.

Wiring in parallel doubles the AH, voltage remains the same.


----------



## Weldorthemagnificent (May 9, 2019)

gnappi said:


> Weldorthemagnificent said:
> 
> 
> > It's a good idea. Lots of RV guys do this for dry camping. Wiring in series doubles the amp hours over two 12 volt in parallel.
> ...


I stand corrected. I have a couple friends who have gone to two 6 volts over a single 12 for RV use and they rave about it. How they get so much longer on a charge. So I just looked into it. Why not two 12 volt batteries? The main answer I found was longevity. Because of the size of the cells and plates in the 6 volts, they will withstand more charge/discharge cycles. 
Thanks for helping me learn something. 

Sent from my CLT-L04 using Tapatalk


----------



## gnappi (May 9, 2019)

Weldorthemagnificent said:


> >>SNIP<<
> I stand corrected. I have a couple friends who have gone to two 6 volts over a single 12 for RV use and they rave about it. How they get so much longer on a charge. So I just looked into it. Why not two 12 volt batteries? The main answer I found was longevity. Because of the size of the cells and plates in the 6 volts, they will withstand more charge/discharge cycles.
> Thanks for helping me learn something.



Reasons for getting more time on a charge is it's likely they replaced old batteries, or the new ones had a higher Ah rating? I doubt anyone would R&R new 12 volt batteries on a whim.


----------



## LDUBS (May 9, 2019)

gnappi said:


> Research alert!
> 
> *Wiring in series doubles the voltage, AH stays the same.
> 
> Wiring in parallel doubles the AH, voltage remains the same.*


*
*

Learned something new. Thanks!


----------



## The John (May 14, 2019)

Weldorthemagnificent said:


> gnappi said:
> 
> 
> > Weldorthemagnificent said:
> ...




I use two 6v golf cart batteries in my trailer as we dont usually stay in campgrounds (more then 50% of land in the state of Oregon is Public land so there are lots of places to camp by yourselves). The real difference between 6v and 12v "marine" batteries is that the golf cart batteries are designed to be discharged to a lower level of charge and recharged more frequently compared to 12v marine batteries.


----------

