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Old 01-29-2020, 11:06 AM   #1
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LFP batteries in the engine room?

I’ve been researching lithium batteries and am having trouble finding anything definitive on my question. My batteries are currently in the engine room and there is really no alternative to this location. The engine room generally tops out at about 105F while underway. I’m never in colder climates so lower temperature thresholds aren’t a concern.

I’ve seen some sites/videos suggest that the LFP batteries can be discharged across a wide temperature range (clearly between 40f-105f) but elevated temperatures only become an issue when charging. If this is the case would I have good results with LFP batteries in the engine room if I ensured the batteries only charged when the engine room temperature was 90f or lower? My generator running by itself never gets the engine room temperature above 90f. The only charging source would be a 120v AC, I would ensure the alternator wasn’t connected to the LFP batteries.

All inputs appreciated, particularly anyone that currently has LFP batteries in the engine room.
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Old 01-29-2020, 11:11 AM   #2
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I have mine in my engine room. It never gets above 103F or so and my batteries have a BMS that cuts them off from charge if they see 135F. That would be pretty bad to get to that level in the battery box - I would assume it would be even warmer outside of it and my engine room temp sensors would have gone off far before that.

I charge using two small case alternators at about 320 amps total out of those, plus if I’m running the generator I can get an additional 120 amps and have seen no issues. I’ve run this way for a full season including hot days at 90F plus. That may be different for warmer climates of course.

I would have loved to have my batteries elsewhere but I had no choice but to have them where they are.

I have various pictures and such of my setup at https://seabits.com/victron-wakespee...-power-system/
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Old 01-29-2020, 11:16 AM   #3
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Most battery chemistries perform better at higher temperatures, but live a longer lifespan at lower temps. From what I know, LFP is somewhat less temperature sensitive than lead acid (other than low temp charging limitations). But it's still better to keep them out of the hot engine room if possible.
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Old 01-29-2020, 11:58 AM   #4
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LFP lifespan drops off as the batteries get warmer.


CALB, one of the bigger cell manufacturers, says charging from 0C to 45C, and discharge -20C to 55C. These same limits appear in a lot of product brochures as well. Those are absolute limits, and lots of research shows that life starts to reduce above around 40C. My own goal is to stay below 40C, preferably closer to 30C. A few excursions above wouldn't be the end of the world, but less time is better.


One thing to consider in where in the ER your batteries are located, and what the temps in that location might be. A friend and I did some initial temperature observations in a laz for our installations and found that the laz, despite very hot outside temps, and some heat sources in the space, tracked sea water temp pretty closely. So if your batteries are low in the ER, adjacent to the hull, and compartmentalized from the rest of the ER, the actual battery space may be much more moderate. Getting a min/max thermometer and placing it in the battery location for a few weeks might help you zero in on an answer.
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Old 01-29-2020, 08:22 PM   #5
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I use a remote thermometer in my E.R. THe base unit measure the salon, the remote measures the E.R. Many are available with two or more sensors so you could check two locations at a time.
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Old 01-29-2020, 09:21 PM   #6
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I phoned the people at Battleborn about this very question and they said that periods of elevated temperatures within the engine room is only a small percentage over the life of the battery. I understand what TT is saying but as with everything, there are trade offs.

Transport Canada Ships Electrical Standards: “19.4.2 Batteries shall not be installed in sleeping quarters.”

Interpretation of that regulation in consideration of pleasure craft means that almost all spaces within the vessel where people reside are affected including the saloon and pilothouse as these might be sleeping quarters. The regulations don’t specify type of battery.

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Old 01-30-2020, 12:21 AM   #7
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The regulations don’t specify type of battery.
So, can't have a flashlight by the bed then?
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Old 01-30-2020, 09:53 AM   #8
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Steve, thanks for the reply. I read your write up and it was very helpful. I currently have 2 8D wet cells as my house bank and am trying to find the optimum LFP batteries that will fit in my existing 8D boxes. I have not found any 8D LFP batteries and 2 type 31 batteries won’t fit in the 8D dimensions. I’m trying to achieve 400Ahr of LFP capacity in 2 8D boxes. Any suggestions on a particular battery brand/size?
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Old 01-30-2020, 10:56 AM   #9
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Originally Posted by Wdeertz View Post
Steve, thanks for the reply. I read your write up and it was very helpful. I currently have 2 8D wet cells as my house bank and am trying to find the optimum LFP batteries that will fit in my existing 8D boxes. I have not found any 8D LFP batteries and 2 type 31 batteries won’t fit in the 8D dimensions. I’m trying to achieve 400Ahr of LFP capacity in 2 8D boxes. Any suggestions on a particular battery brand/size?
There are probably some off-brand options but Lithionics and Victron are two established providers which have 8D sizes. Some claim to be “drop-ins” with internal controls, others require external controls. Also saw one on an LBP website. I am in the process of replacing one 8D with 3x275Ahr Lithionics models which almost fit into the same space.

One can(should) spend considerable time reading on pro’s/con’s, systems, charging, costs, etc. before spending multiple $K.
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Old 01-30-2020, 12:32 PM   #10
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Steve, thanks for the lead. I checked out the 8D 200Ahr Victron battery and it looks like a good drop in replacement except it’s max discharge rate is 70 amps. So 2 of these in parallel wouldn’t be able to support the 3000 watt victron inverter. I know the battleborn 100Ahr battery says it supports a discharge rate of 100 amps so not sure why this victron is so low. The 50Ahr victron supports 35 amps or 70% of its capacity so why when it’s scaled up to 200Ahr does it only support a discharge rate of 35%?
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Old 01-30-2020, 02:57 PM   #11
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This is a long, but thorough review of LiFePO4 batteries for boats:

https://marinehowto.com/lifepo4-batteries-on-boats/


They explain current limits as a function of internal switches which manage current distribution between internal cells. The model you mentioned is a drop-in with internal BMS.

More robust designs have higher capacity switches.

The Lithionics have recommended charge/discharge rate of 50%/100% with maximums of 100%/100%. Victron's external BMS models have recommended charge/discharge rates at 50%/100% of capacity and maximums of 200%/200%.
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Old 01-30-2020, 04:57 PM   #12
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Steve, thanks for the lead. I checked out the 8D 200Ahr Victron battery and it looks like a good drop in replacement except it’s max discharge rate is 70 amps. So 2 of these in parallel wouldn’t be able to support the 3000 watt victron inverter. I know the battleborn 100Ahr battery says it supports a discharge rate of 100 amps so not sure why this victron is so low. The 50Ahr victron supports 35 amps or 70% of its capacity so why when it’s scaled up to 200Ahr does it only support a discharge rate of 35%?


You might check the 180Ah batteries at this site.
Two of them would get you close to your desired 400Ah capacity, they have a slightly smaller footprint than 8D’s but they are .9” taller. They also spec a continuous discharge of 150A.

I think they are what I’m going to go with.

https://www.custommarineproducts.com...batteries.html
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Old 01-30-2020, 06:27 PM   #13
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If you have a decent LA bank, you could add LFPs remotely to augment the LA batteries until the LA batteries fail. Just connect them via a DC to DC converter and makes sure the LA bank is discharged last in normal use. In this manner, you get all the advantages of the LFPs, the LA batteries will last a really long time, there's no waste, and you get a much bigger house capacity for just the added cost of the DC to DC converter.
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Old 01-31-2020, 07:34 AM   #14
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Jim (JDCave), I misled you back in another thread about temp limits for LFP. I think I said 30-40C was the limit, but that's actually a goal for preferred conditions, not a limit. The manufacturers' limits are higher per an earlier post in this thread, but with corresponding reduction in life span. But the good news with LFP is that even when run at the extremes (max temp, max charge and discharge rates), they have been consistently demonstrated to yield 2000+ cycles. So with lighter use, it's just a question of how much more you might get. I know lots of people who are expecting 5000 to 10000 cycles, but only time will tell, and a lot of time at that :-)
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Old 01-31-2020, 05:26 PM   #15
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Operating LFP batteries in the "normal" engine room will degrade the capacity relatively quickly.

A good friend installed GBS cells in his trawler between the engines while down island. After about 15 months he ran a capacity test and found that the bank lost about 30%. He also experienced two cell failures in 30 months.
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Old 01-31-2020, 09:07 PM   #16
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LFP batteries in the engine room?

Quote:
Originally Posted by CharlieJ View Post
Operating LFP batteries in the "normal" engine room will degrade the capacity relatively quickly.

A good friend installed GBS cells in his trawler between the engines while down island. After about 15 months he ran a capacity test and found that the bank lost about 30%. He also experienced two cell failures in 30 months.

That might be the case in FL. Probably not severe where I live. The only time I know where this might be an issue is when I’m cruising through Desolation Sound, where the surface water temperature might push 25 C...

Which begs the question: has anyone monitored the temperatures in the engine room whilst traveling or anchored in Desolation Sound?

And while engine room temperatures may be high for the period when the vessel is running or immediately after anchoring, how high are the temperatures in the living areas on an unattended vessel at the dock? I’m pretty certain in that case that my engine room is cooler than the saloon.

Edit: I just searched GBS cells and evidently, these are cheap LFP batteries from China. Having reviewed CMS’s web post on LFP and other sources, I think you really can’t discount the likelihood hood that the source of batteries may be the problem rather than the siting in the engine room.

Jim
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Old 01-31-2020, 10:02 PM   #17
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Which begs the question: has anyone monitored the temperatures in the engine room whilst traveling or anchored in Desolation Sound?
Jim

I did this last year. My LFP bank is in my engine room down low against the hull. It was 4-5 degrees F higher both in the whole engine room and maybe one higher in the battery box. Within the margin of error.

My engine room usually sits at 60F year round at the dock. I have heaters in it for the winter months and block the air intakes then too.
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Old 02-01-2020, 07:54 AM   #18
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Quote:
Originally Posted by DCDC View Post
This is a long, but thorough review of LiFePO4 batteries for boats:

https://marinehowto.com/lifepo4-batteries-on-boats/


They explain current limits as a function of internal switches which manage current distribution between internal cells. The model you mentioned is a drop-in with internal BMS.

More robust designs have higher capacity switches.

The Lithionics have recommended charge/discharge rate of 50%/100% with maximums of 100%/100%. Victron's external BMS models have recommended charge/discharge rates at 50%/100% of capacity and maximums of 200%/200%.
Thanks for the link, that article was very detailed and informative. The more I read the less certain I get that LFP batteries are for me. I’m now researching the Firefly batteries as these batteries can supposedly be used in the 30%-85% SOC for extended periods without sulficating.
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Old 02-01-2020, 08:00 AM   #19
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Operating LFP batteries in the "normal" engine room will degrade the capacity relatively quickly.

A good friend installed GBS cells in his trawler between the engines while down island. After about 15 months he ran a capacity test and found that the bank lost about 30%. He also experienced two cell failures in 30 months.
Thanks, I’ve been reading numerous sources advising the same thing, hence the purpose of my original posting. If I lose 30% capacity after a year then a primary reason for converting to LFP is lost.
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