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Time to go Lithium Ion on Sailing Catamaran

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Driftwood Cat

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May 20, 2020
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Newbie to the forum.

Present set up on catamaran:
6 x 400ah Rolls AGM’s operating as 1200Ah 12v bank – 540W solar – 60W Morningstar Solar Controller – 2 x 140A Amptech Alternators using Balmar MC614 Regulators – 9kw generator – Magnum 3kw MSH3012M Hybrid Inverter/Charger.

Boat is heavy on electrical load with three 12v fridges, one 12v chest Freezer and one 110v U-Line Icemaker. Based in tropics, so they all work hard. Plus many 12v pumps on board, though only running short periods, plus microwave, electric kettle, toaster, coffee maker.

Batteries need to be replaced, so considering following, partly based on all the superb information gained from Will Prowse’s Youtube sessions and from SeaBits excellent article on his refit with Battle Born Lithium Ion units.

Retaining Magnum, Morningstar Controller, Amptech Alternators, 9kw generator.

Planning a switch to Wakespeed WS500 Regulators, Sterling Alternator Protectors, Sterling 12v DC to DC chargers for Engine batteries and Battle Born Batteries.

Have no problem charging 2-3 hours a day and use one engine most of time when motoring.

Main question is what Ah battery bank to aim for using Lithium, to give me a 12 hour no charge period. Overnight draw can be 500Ah when all cabins used. Solar usually good for 5 hours + here in Belize. Present charging set-up not sufficient to keep 1200Ah AGM's charged, so very fast decline.

Any thoughts/recommendations from the members
 
Driftwood Cat said:
... Main question is what Ah battery bank to aim for using Lithium,...
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The good news is you already have an amount of power that works for you and Watts is watts.

Take the voltage of your existing system and multiply it by your existing number of amp hours, that's the number of watt-hours you have (add more Amp hours if what you have now isn't enough). For the math, you had 1200 Ah x 12V = 14.4 kWh.

Now comes the fun part.
What's the Depth of Discharge (DoD) you currently run your AGMs to? Let's say it's 40% and you pick 80% as the DoD for your LFPs.
So, out of the 14.4 kWh you only use 60%, or 8.64 kWh. If you run your LFPs to 80% DoD, then you'd need 10.8 kWh of LFP batteries.

AGMs are rated at a 20 hr drain rate. For example a 100 Ah battery provides 100 Ah if drawn slowly over 20 hours. If you drain the battery in 2 hours you'll only get 65 amps out of it. So, if you're draining your batteries over 24 hours, you might have slightly more than 1200 Ah. If you're draining them in fast spurts, you might have a lot less. LFPs are more insensitive to this, but you might need to adjust slightly based on your usage patterns.

Driftwood Cat said:
... Have no problem charging 2-3 hours a day...
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In general, LFPs have higher charging C-Rates than AGMs so your current charging setup should work with them... although if there's any smart's embedded in the chargers for managing AGMs you'd need to reset it (or swap) to LFP settings.

Driftwood Cat said:
... Any thoughts/recommendations from the members ...
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LFPs don't weigh as much as AGMs, about half. 1200 Ah of AGMs is probably around 900 lbs, so the boat will be a bit lighter, ~400 lbs.
 
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Let us know how it goes, and post pictures please! I'm definitely a cat-lover!
 
i recomend this sites in case you havent checked them:

nordkyndesign.com
marinehowto.com

DIY LiFePO4 Batteries On Boats - Marine How To

DIY LiFePo4 On Boats Last edit;3/26/23:The base of this article was written a number of years ago (2010) but this does not mean the information here is outdated. We have been keeping it updated and have added to it when ever we had the time. This article deals
marinehowto.com
 
I just bought a cat that is in need of lithium upgrade, so I'm following with interest
 
Roleo. It will be a slow process as based in Belize and taking time to get system priced and shipping sorted. But we'll get there.
 
Driftwood Cat said:
Roleo. It will be a slow process as based in Belize and taking time to get system priced and shipping sorted. But we'll get there.
Click to expand...
All good, mine will take a while as well. All though Sydney based finances will dictate the pace.
 
I had originally thought that Battle Born batteries were the way to go, until I read the history and performance of Valence, now Lithium Werks. However it seems Lithium Werks will not see to private individual requirement, but sell on B2B basis only.

Other than risking the purchase of used Valence/Lithium Werks batteries, does anyone know if new ones can be purchased through a retailer?
 
I saw a listing on Amazon .... but the price was VERY HIGH.
 
I am not sure if Battle Born is a good choice as a engine starting battery. Mine trip and fault out on just a half second inrush to startup my 4k inverter. I would guess they would trip instantly with a starter. To reset them you have to disconnect the load and they internally power back up.

I have 2 (24VDC) batteries in series for 48 VDC. 50 AH.

FYI
 
newbostonconst said:
I am not sure if Battle Born is a good choice as a engine starting battery. Mine trip and fault out on just a half second inrush to startup my 4k inverter. I would guess they would trip instantly with a starter. To reset them you have to disconnect the load and they internally power back up.

I have 2 (24VDC) batteries in series for 48 VDC. 50 AH.

FYI
Click to expand...
You could try one of these pre-charge units http://www.rec-bms.com/EVproducts.html
 
Still dithering on battery choice/cost. Anyone have any thoughts on merits of Lead Carbon Batteries?
 
I'm still dithering between Lithium and Carbon Foam AGM....depends on my funds in about 2 months ;-) (for my catamaran). This video is about battery types and use in the marine world, but does mention Carbon Foam AGM batteries a bit as they perform better than standard AGM, but not quite to Lithium....so it's a good compromise according to this presenter.
 
I was considering those for my RV ... There is a manufacturer near me. I decided to go with LiFeP04 because of weight considerations.
 
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