FireFly Battery Long Term Users - Speakup

[CarlF]

You need someone who installs a lot of LFP batteries in cruising boats to help you design the system and fill in the "Don't know what I don't know" areas. There really aren't many gotchas:

1) You need adequate cable size and proper fusing. Class T fuses.

2) All charge sources have to be able to meet the manufacturer's voltage specs (most are OK with 14.1-14.4Absorbtion, 13.5Float, 0-60 minutes absorbtion, no temp compensation)

3) You need to protect the alternator if the BMS shuts off (which should never happen in a properly designed system - it's never happened to me)

I ended up installing Kilovault drop in batteries which are recommended by Rod. Kilovault is a US firm associated with the very large and long established AltE in Massachusetts. Top quality. They are likely to be around if you need help down the road -- unlike the batteries on Amazon. The Kilovault 300AH battery list is $1895 - or $630 per 100AH.

One of the Kilovault dealers is TheYachtRigger in St. Petersburg who is selling a huge number of these for cruising boats. Boats are different than RV's where many LFP's are going. They know the ABYC standards and go beyond them in many important ways (such as recommending equal length cables to keep the batteries balanced). They can design the system, tell you how to set the chargers, and drop ship. They can even make up the cables. You'll still need a local ABYC electrican involved in the install since your insurance company may ask his name.

For my part, I am thrilled with my 1500AH of Kilovault battery. Far better than my experiences with flooded, AGM Lifelines, and Fireflys. A bluetooth app lets you check each battery's statistics. There's no need to charge them to 100% and they don't care if they are discharged way below 50%.

I now spend very little time thinking about my battery SOC and health - unlike all my previous boats. And it's also wonderful that LFP batteries spend virtually all their time beteen 13.1v and 13.5v. Pumps, fridge, watermakers, etc all run much better than at 12.5v.

[sailorboy1]

Originally Posted by CarlF

For my part, I am thrilled with my 1500AH of Kilovault battery.

wow, and here I am talking about a 400aH bank

[s/v Jedi]

Originally Posted by Adelie

96.2% efficiency.
Is that LiFePo?

Winston, they doped it with Yttrium but I don’t think it will matter for efficiency. The big difference is charge rate and in which range of SOC you are.

[crayiii]

Originally Posted by sailorboy1

wow, and here I am talking about a 400aH bank

I just ordered a few of the Kilovault batteries as well.

[FlyingScot]

We have 900AH @ 12v (6 batteries). They have been in constant use for 2.5 years. I took them apart to clean the terminals and check them.
Each battery is two 2v in one housing. After sitting for between 1-2 hours unhooked I measure the following voltages with my Fluke 87v DMM.
2.156v
2.153v
2.158v
2.153v
2.154v
2.162v
2.153v
2.162v
2.152v
2.149v
2.142v
2.150v
Average cell voltage of 2.154 with a total deviation of 0.02v between the highest and lowest.

I see no signs of failure but we are replacing with Victron 330AH x 4 in the near future.

[Nicholson58]

We gave up on ours at four years. We were extremely careful to maintain charge in the top end. Balmar external alternator controllers etc. They died precipitously last season. The cases were all bulged. Now replaced with Blue Heron LiFePo. These seem fantastic. We were running the generator daily 3-4 hours daily. Now 2 Hours, twice a week depending on solar performance. I did the swap in Trinidad with the batteries shipped into Power Boat Marine. Blue Heron was very supportive regarding programming assistance for the Balmars, Victron, solar.

[donradcliffe]

Originally Posted by Adelie

From the first test report:
https://batterytestcentre.com.au/wp-...port-1_web.pdf

For the LFP cycling was from 5% or 10% up to an undefined top cutoff. The top and bottom cutoffs were set by the BMSs provided by the battery suppliers, except maybe CALB.

For LFP charge & discharge cycle were at C/3.

The advanced Lead-Carbon battery was cycled 30-80% per supplier recommendations at C/4.

The regular Lead battery was cycled 50-100% at C/5. Still got 87% charge efficiency.

For all lithium batteries there was a 60m no activity period between the end of charging and the beginning of discharge and visa versa. Thus the we’re getting 3 cycles per day.

Testing was by an independent consultant paid for by the Australian government so nobody was skewing the data. .

Just do a little experiment with your battery bank. Measure the terminal voltage, then put a load of C/5 on it, and measure the terminal voltage again. The Internal Resistance of the battery is the difference in voltages (voltage sag) divided by the load current. My own experience is that LiFeP04 batteries have significantly less voltage sag.

Now think of the energy LOST (converted to heat)when charging AND discharging. It is equal to the SQUARE of the current times the Internal Resistance. The efficiency of a charge cycle is based on the sum of the charging and discharging losses.

Now tell me why your "unskewed" tests used a current which was 5/3 higher for the lithium battery than the lead acid battery, which would result in theoretical efficiency losses 2.8 times higher?

[Adelie]

Originally Posted by donradcliffe

Just do a little experiment with your battery bank. Measure the terminal voltage, then put a load of C/5 on it, and measure the terminal voltage again. The Internal Resistance of the battery is the difference in voltages (voltage sag) divided by the load current. My own experience is that LiFeP04 batteries have significantly less voltage sag.



Now think of the energy LOST (converted to heat)when charging AND discharging. It is equal to the SQUARE of the current times the Internal Resistance. The efficiency of a charge cycle is based on the sum of the charging and discharging losses.



Now tell me why your "unskewed" tests used a current which was 5/3 higher for the lithium battery than the lead acid battery, which would result in theoretical efficiency losses 2.8 times higher?

The tests were not skewed by the testing agency, they followed the recommendations of the suppliers.

The batteries are fundamentally different and will need to be treated differently. Using LiFePo you will get faster charge and discharge rates at the cost of a higher upfront price, a higher price per Whr delivered over the life of the battery and a more complex electronics system to manage the battery.

[s/v Jedi]

Originally Posted by Adelie

The tests were not skewed by the testing agency, they followed the recommendations of the suppliers.

The batteries are fundamentally different and will need to be treated differently. Using LiFePo you will get faster charge and discharge rates at the cost of a higher upfront price, a higher price per Whr delivered over the life of the battery and a more complex electronics system to manage the battery.

The price per Whr delivered over the life of the battery is much better for lfp vs la.

[sailorboy1]

well yeah easy to say since I just paid 62% of the price for LFP than I did for FF 2.5 years ago

but all these price things other than upfront costs are just based on assumptions

2.5 years ago it was borderline crazy to get FF instead of LFP. Now it would be insane even if it was possible.

[Adelie]

Originally Posted by s/v Jedi

The price per Whr delivered over the life of the battery is much better for lfp vs la.

I did the analysis a year or so ago and FLA was cheaper than Plug-n-Play LFP. NewHaul’s DIY LFP was cheaper. See attached. I’ll redo in the next couple days.

[s/v Jedi]

Originally Posted by Adelie

I did the analysis a year or so ago and FLA was cheaper than Plug-n-Play LFP. NewHaul’s DIY LFP was cheaper. See attached. I’ll redo in the next couple days.

With my “expensive” Winston cells I get 12,800Wh per dollar. If I could do 70% deep cycles instead of 80%, my Wh per dollar increases to 15,680.

Here’s the problem: when you buy easy or cheap you’re not getting the cycle life. At 80% deep cycles Winston does better than 5000 cycles and at 70% it increases to better than 7000 cycles.

I will never run out of cycles because I do shallower cycles.

[crayiii]

Usable volts has been our biggest issue with LA. Sure, take it down to 50% but then good luck with how much voltage drops. A steady 10-15 amp draw and you’ll be wishing for that sweet lithium voltage.

[Adelie]

Originally Posted by s/v Jedi

With my “expensive” Winston cells I get 12,800Wh per dollar. If I could do 70% deep cycles instead of 80%, my Wh per dollar increases to 15,680.



Here’s the problem: when you buy easy or cheap you’re not getting the cycle life. At 80% deep cycles Winston does better than 5000 cycles and at 70% it increases to better than 7000 cycles.



I will never run out of cycles because I do shallower cycles.

As I wrote previously, if you DIY, yeah they can be cheaper, and probably longer lived as you can replace the BMS which I feel is the limiting factor for Plug-n-Play LFP.

How much did you pay for the cells and the BMS and what are the capacities? What are their dimensions, cells & BMS? How many cells?

[s/v Jedi]

Originally Posted by Adelie

As I wrote previously, if you DIY, yeah they can be cheaper, and probably longer lived as you can replace the BMS which I feel is the limiting factor for Plug-n-Play LFP.

How much did you pay for the cells and the BMS and what are the capacities? What are their dimensions, cells & BMS? How many cells?

Here’s the cells: TSWB-LYP400AHA – Sky Power – Winston LiFePo4 Battery Provider

I have 8 in series.

I built my own BMS, cost is almost nothing, but I’m working on a model that I will publish free to copy which has more features like BT and Wifi and will still be under $100

Oh wait, I use a BlueSea Systems remote battery switch… that’s $125 by itself.

Edit: lol, forgot the price of the cells. Julia Yu sells them for $1/Ah/cell.