Re: [electricboats] 39' sloop conversion

A cycle is generally a large draw down of your battery, under 20% to nearly full again. It takes many small draw downs to say 90% and back to nearly full again to equal one "real" cycle.  As for If solar or A generator while under way, Is counting against your cycles. Probably not if no charging and or drawdown is happening, if your batteries are not gaining or losing any charge then the internal resistance is higher then the resistance of your loads, so all the power from solar is going directly to loads.  The battery really can not tell the difference between that and doing nothing. With the caveat that they would notice some fluctuations or ripples in the voltage.  

Generally speaking it takes 100 of small draw downs and recharges to equal one cycle lost.  You are a probably losing more capacity to just plan calendar life lose then from cycle life lose is most situations with LiFePo4, when not doing large drawdowns to under 20% back to full, they maintain they Capacity very well.  

My pack is now 10 years old, I have lived aboard for over eight years of there life using them as a house bank (many small drawdowns to say 90-85% daily, and have Cruised the last 2 years meaning large draw downs a couple of times a month when I switch anchorages/marines as I travel. Generally I only draw them down to a little less then 50% on most travel days.  But occasionally go down as far as 30%.  I like to keep plenty of reserve capacity incase things don't go well.  After 10 years, I have no measurable difference in there rated capacity.

What follows is "internet theory"  Some of that amazing lack of capacity lose may be do to Winston manufacturing  there 1000ah cells with some reserve capacity. Meaning they may have Really been 1010 ah Cells originally.  Most cell manufacturers no longer under rate there cells anymore.  When large prismatic cells where new, they where a little over engineered for warranty purposes, but once the manufacturers had real word data on actual reliability they did less over engineering.  

But either way my Winston LiFePo4 cells are still delivering like new performance ten years later.  

On May 23, 2020, at 9:23 AM, Robert McArthur <rjmcarthur@gmail.com> wrote:

Something I have wondered about hybrids and use of regular solar plus gensets...

If you are going along and using power from the battery, and each moment there's some solar going in and you are running a genset so that's going in to the battery too: a battery has a certain number of cycles that it's good for ("good" being relative, but let's pretend it means that it still retains a useful amount of charge). The manufacturer may say a particular battery may be good for "2000 cycles".

But given at every moment you are taking out, say, 100amps, while at the same time putting in 100amps (let's say), how much does that eat into the "cycles" if you do that hour after hour, day after day?

Now what if you're pulling 100amps from a pack and that after an hour it takes The battery to 50% without anything going in (nice quiet motoring). At the start of the hour you start your oversized genset which, over the next hour, replaces the original 100amps AND the 100amps that the motor is using while the genset was running. So at the end of the second hour the battery is full. Then you run another hour quietly. Rinse and repeat. Under that scenario, are you eating into the cycle lifetime of the battery by 12 times every day? More? Less?

I'm happy to assume LiFePO4 if that helps answer :).

Thanks

Rob

On 17 May 2020, at 11:36 pm, MATT <msteverson@gmail.com> wrote:

Hello all, I'm a longtime lurker, this is my first post, so please, be gentle.

We have lived on our 39' sloop for about 5 years now and are ready to convert to hybrid...this is the plan I've come up with and am looking for your critical analysis.

The boat is a custom build. It displaces about 18000 lbs all full, has a 3/4 length "scheel" keel, and only draws about 50".  We currently have a very good running yanmar 3gm30f that turns a 17" 2 blade max prop.  We've put in about 20k nm over the past few years and she solidly averages 6kts.  The engine is in the middle of the boat under the galley sink and makes A LOT of noise and stink and we're sick of it.  We've got a little extra time and money so we think this project could go a long way.

The plan
- 48V 12KW Thunderstuck ME1616 kit - currently its on backorder - with a 3:1 gear reduction
- About 15kw lithium battery bank (right now Thunderstruck has Valence 1.6kw batteries used for $350 each, so 8 of these, and the VC1 BMS they sell, I think would be easy to install and work well.)
- A 3.5-4kw diesel generator that is PURELY for recharging batteries using the thunderstruck TSM2500 kit with 2 chargers.  This should get me 70amps at 48volts running from 240VAC.  This is important because we live at anchor in the PNW year round.  We often have a long way to go with no wind, or sun and generally avoid marinas.  I will buy this used or rebuilt to save dollars.
- Run existing loads off of a DC-DC converter

- We have 500W of PV installed with 12V Victron charge controllers that keeps up with our daily usage.  I would like to get them putting electrons into the 48v bank and am wondering if there is a work-around with DC to DC converters or something so I don't have to buy all new CCs.  

I will be doing this install myself.  I'm confident with basic stuff like solar installs and alternators but this project will be a little out of my comfort range, I'm very much looking forward to it.  What is most important to me is to keep the system as simple and user friendly as possible mostly for resale purposes.  

Any advice/comments/questions/trashtalk would be appreciated.  

Matt