Re: [electricboats] advice not on sailing boat

I agree with this.  And the battery is the only part of the system that is scalable.  You can save some now with  smaller battery bank and expand that later. 

Dan Pfeiffer

On 2022-04-30 6:16 am, Randy Cain wrote:

Trying to save money by avoiding an efficient motor and speed controller will force you to spend more than you need to on batteries. I recommend that, to minimize the overall system costs while achieving your performance goals, aim for an efficient design rather than trying to cut corners too early in the process.

Re: [electricboats] advice not on sailing boat

Trying to save money by avoiding an efficient motor and speed controller will force you to spend more than you need to on batteries. I recommend that, to minimize the overall system costs while achieving your performance goals, aim for an efficient design rather than trying to cut corners too early in the process.

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[electricboats] Thoughts on 12 volt Lifepo4 batteries

Hello, 

I have a 20 foot bass boat that is mainly used on lakes that restrict the use of my 150hp gas motor.  

The electric motor is a 36 volt trolling motor. I would like to have mor reserve run time than my current setup and was looking the 12 volt LifEPo4 batteries that are sized as replacements for AGM or Flood Acid type deep cycles.  Most are 100 amp hour and that should be fine.

Does the group have any suggestions as to a good battery brand and/or would it be better to build a separate set of cells instead of purchasing 12 prebuilt ones?

My current batteries are Optima group27 blue top. Replacement are in the $330 range and from my research they are now manufactured in a different location and will not last 6 or 7 years like my current ones have.

I am familiar with Lifepo4 as I have constructed 12s2p 2400mah packs for some R/C helicopters. Torn out of old Dewalt packs, A123 cells.  I know they are smaller but the concept seems similar.

Thank you for the help

 

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Re: [electricboats] advice not on sailing boat

i've been a bit distracted the past couple of weeks but have some data on the current propellor and rpm. 

I have a (odd) 400 mm diameter , 290mm prop. 
my current engine runs stationary with a propspeed of 340rpm with a speed of 3.5kmh (1.8/19.9knots) - i like to go a bit slower then that as well
at 545 rpm the speed of the boat is about 3 knots
600 rpm 3,5knots
840 rpm 4,5 knots
975 rpm 5 knots, about max speed on the engine.
i'll probably cruise around 500-700rpm 90% of the time. 
but do need to brake/manouvre and cross a big canal occasionally, so woudl like to get 900-1000 rpm sometimes.

Taking into account my attempt to keep the prop (as long as it's not against me), i was hoping to get some advice on the engine. is a used 48v dv (series wound) dc engine a possibility? I'm trying to avoid a brushless because of cost of engine and controller. 

also I thought to find an engine with a low rpm to make it work without a reduction (less elements, less costs, less noice). 

Any thoughts?

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Re: [electricboats] Storage of LiFe PO4 Battery for 6 Months

Every summer I store Sunshine in dry dock. Some summers I’ve left the battery on with my fridge running all summer unattended. Others, I’ve turn the battery off and let it sit all summer. Each fall, battery is charged - not full - but certainly not empty. 

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Re: [electricboats] Storage of LiFe PO4 Battery for 6 Months

The biggest problem we have seen is from a bms that puts a drain on all or just a new cells, best to disconnect bms from pack

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Re: [electricboats] Storage of LiFe PO4 Battery for 6 Months

I also have several LFP batteries of various brands.  All are 12V stacks with BMS boards in them.  I've left some of them unused for several months.  I have not noticed any self-discharge.  I'm quite impressed with this technology!
In order to forecast storage loss, you could record the battery's voltage now and check it again (same meter) in a month.  Extrapolate from that difference if you find one.   Make sure the meter and the battery are at the same temperature for both tests.  Cheers,
Halden VE7UTS

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Re: [electricboats] Storage of LiFe PO4 Battery for 6 Months

I just received the following from the supplier. Better than nothing, but just. 

Maximum allowable charging current :100A
Maximum allowable charging voltage :14.6V
Maximum allowable discharge current 15S: 100A
Recommended charging voltage: 14.4V
Recommended float voltage: 13.4V
Recommended charging current: 20A
Recommended cut-off charging current: 5A
Recommended torque:M8*12

And a big thank you to all who responded, especially Myles. All good advice.

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Re: [electricboats] Storage of LiFe PO4 Battery for 6 Months

I think the advice you got from Myles was pretty comprehensive. If you don't have any BMS turned on I think you will see very little self discharge. I've got powerwall batteries that have been stored for a year powered down and had no detectable self-discharge. The paperwork that came with them says 1%/year. 

On Apr 5, 2022, at 14:05, Draggett@live.com wrote:

Latest. The manufacturer was of no help. Just suggested they not be stored more than 6 months. No tech specs. I guess I'm on my own. When I get back in the fall I'll test them again and let you all know how they fared. I connected them in parallel for several days to let them balance, Then charged them together. Disconnected them all from each other and stored them flat. Fingers crossed.

Re: [electricboats] Storage of LiFe PO4 Battery for 6 Months

Latest. The manufacturer was of no help. Just suggested they not be stored more than 6 months. No tech specs. I guess I’m on my own. When I get back in the fall I’ll test them again and let you all know how they fared. I connected them in parallel for several days to let them balance, Then charged them together. Disconnected them all from each other and stored them flat. Fingers crossed.

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