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Re: Amel is going lithium

Paul Brown
 

Hi Scott 

I do like your thinking and see you have muchbmore understanding than I.

I generally run my 720ah lithium MV down to around 30% before I top them up with the generator and usually only to about 50 or 60 %, maybe every 2 weeks I will charge to 100% when I’m making water or washing machine or aircon or all, otherwise I’m relaxed at anchor and keep them around 50%, the 550w 24v solar contributes to 75% of my general 24v/220 inverter power consumption 

How many cycles do you think I’ll get and how many years of life seeing the boat is wintered 6 months a year?

The MV technician said he would think 15 to 20 years total life, as they are relatively new technology they don’t really have those statistics but at a guess.

Regards Paul-Fortuna II 55#17


On 8 Aug 2019, at 2:31 pm, Scott SV Tengah <sv.tengah@...> wrote:

Nick,

When I run the WM, the Dessalator gauge reads well over 100 liters per hour but it appears a bit optimistic. I assume you're checking the dipstick prior to running it for one hour and then checking again after 1 hour of runtime? I am aware of the effect of salinity and temperature but I'm loathe to try to put it higher into the red in order to try to squeeze out some more output. I'd rather just keep it in the recommended green and run it a bit longer.

In any event, with respect to the battery charging routine, it's really just a math problem. I average a bit over 200 AH a day from my solar panels. I run two fridges and a freezer. I cook with induction. I use the electric kettle to make coffee. I use my laptop. Those uses are more or less fixed. With that usage and decent sun, the battery bank doesn't drop below 35% for days. The recommended/acceptable practice is to run it down to 20% SOC, but I get nervous at 30%. So I have 450*.7 = 315AH of usable capacity. Add in 200AH of solar output and I have 515AH per day to work with. We don't use that much per day so it lasts a few days.

Lately I've been trying to keep between 40-80% state of charge, if possible. That's the least stressful for the batteries and extends their life. I won't run the genset early in the day if I think solar will push the bank above 80% that day and I don't run high draw appliances if I'm near 40% without running the genset. I'll charge to 100% if I know it won't be staying there long - eg I may run the genset to charge to 100% before a full night of air conditioning on battery. Keeping a lithium bank at 100%, especially in high ambient temps, is not good for them.

I treat my batteries very well due to the initial cost. Most would simply take it to 20% and fire up the genset to take it to 100% without any other adjustments.  Even with that "abuse", they'll get 2000 cycles out of them. It's certainly simpler and I may be overthinking it, but I don't mind a bit of extra thinking to make them last a few thousand extra cycles.

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com

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