New battery technology ?

[DDW]

6 months is a long time. If I were laying up for that long, I'd try to completely disconnect the batteries and store them around 40% SOC.

6 months or a bit more is routine for me (and also most on the east coast). I am now in the middle of a forced, ongoing 18 months and counting layup. It would be a shame if that destroyed $4K worth of batteries.

 

[Hippocampus]

Have wondered why mix and match isn’t employed. Even in one technology there’s differences that favor a particular form for a particular function. FD trawlers aren’t that weight sensitive but are more likely to need to function autonomously.
So perhaps a malic acid fuel cell for house demands on cloudy windless days. Solar when the sun shines at a suitable angle and wind when available.
Thrusters, starters, compressor when they first start are high draw and may need that big bump Pb or C provide but for diurnal cycling Li seems to have a leg up.
Maybe an electrical engineer can chime in. Through the years have watched the dramatic improvement in smart chargers and invertors. What’s the obstacles on the other side. Why can’t you with a bit of AI have multiple sources ( different chemistry batteries, alternators, alt. energy, fuel cell, shore, genset etc.) and a black box decide where power goes and where power is drawn from? Seems all these work arounds and lack of utilization of the strengths of each technology would be eliminated. Throw in capability to accept any form of shore power and I’d buy it just for that.

 

[Jeff F]

6 months or a bit more is routine for me (and also most on the east coast). I am now in the middle of a forced, ongoing 18 months and counting layup. It would be a shame if that destroyed $4K worth of batteries.

Interesting discussion. FWIW I had a Nissan Leaf a few years ago and there was a lot of chatter then about parking the car for months at a time. Consensus was that leaving it at 60-70% SoC and ignoring it would be just fine. I think that was the manufacturer's recommendation. For seasonal storage I wouldn't have much concern. If it stretched out you could cycle ashore by plugging in a heater or something.

I'm just completing a project on my new boat that involved replacing all the batteries aboard. As part of that I rebuilt the 12v system, installed high quality regulation on the alternator and solar charging systems for the house bank, and dc-dc chargers to charge peripheral banks for starting and thrusters. I did this mostly to ensure optimum battery health in each bank, but it also allows for the use of different types of batteries in each bank.

I ended up using GC batteries for my house bank. The lower cost and my use case argued in their favor. The thrusters and start batteries are all AGM starting batteries. But I'm confident that I can seamlessly convert to lithium in the future as my need change and price drops.

 

[DDW]

Interesting discussion. FWIW I had a Nissan Leaf a few years ago and there was a lot of chatter then about parking the car for months at a time. Consensus was that leaving it at 60-70% SoC and ignoring it would be just fine. I think that was the manufacturer's recommendation. For seasonal storage I wouldn't have much concern. If it stretched out you could cycle ashore by plugging in a heater or something.

I'd have much less problem with managing the LFP if the boat where just down the street. But it is 1000 miles away (when stored) so just plugging in the heater or something isn't convenient. I'd have to depend on others, my experience with doing that is very mixed.

The algorithms required of a computer are simple enough, but the market is small and I suppose there are risks in automatically switching loads unattended are relatively large.

 

[twistedtree]

I'd have much less problem with managing the LFP if the boat where just down the street. But it is 1000 miles away (when stored) so just plugging in the heater or something isn't convenient. I'd have to depend on others, my experience with doing that is very mixed.

The algorithms required of a computer are simple enough, but the market is small and I suppose there are risks in automatically switching loads unattended are relatively large.

I think in your situation I would discharge the batteries down to 40% or so and disconnect them completely. And if temps are also out of range or borderline, I'd look for some sort of indoor battery storage.


One thing I did on my current boat is install an OFF-1-2-Both battery selector switch for the house bank that allows for paralleling it with either or both of the AGM start banks. I originally did this as a fail-safe against a BMS failure that might take the LFP bank offline. But now that you mention long term storage, I'm realizing that it could work well for that purpose too. Assuming you want to maintain minimal DC power on the boat during the layup period, you could simply parallel the house bank with one or both start banks, then disconnect the LFP batteries for storage. It would probably be good to also reprogram whatever charger remains on for the AGMs, but it seems a good way to completely idle the LFP bank for an extended period.

 

[DDW]

I do have that ability - but the question remains: how long can you leave them unloaded and uncycled with no (or little) effect on life? Have you seen any test data? From some other experience I'd think 6 months wouldn't be a problem, but I wonder about 18 months.

 

[catalinajack]

I was curious about whether this was true but it depends on how one defines a "long day". So, I have been experimenting with my setup to see just how long it takes to recharge my 920ah battery bank. I recently installed a Balmar SG200 battery monitor so that I would have accurate information on State of Charge (SOC). This was my experience.

I discharged the bank to 40%, twice. In other words, I consumed about 550 amp-hours. The charger spent 4:45 in bulk charging. Interestingly, the charger went to absorb at 90% SOC while the common knowledge is that this occurs at 80%. I have no explanation for this. In any case, it took 1:15 in absorb time to reach 100% SOC, six hours all together. I did not test to 50% SOC but a simple extrapolation of bulk time charge suggests that a full charge would have been reached in about five hours.

My charger is a Magnum 2812 inverter-charger that nominally puts out 125 amps. The Balmar SG200 consistently showed about 100 amps going into the batteries. The difference can be attributed to house loads.

My alternators are a pair of 100-amp Balmars. If I assume that they effectively, underway, due to heat, etc., whatever, they put out no more than 150 amps, together, that is still way more than what the Magnum produces and still less than the charge acceptance of a FLA 920ah battery bank. So, I think it is reasonable to assume that charging my bank from 40% to 100% would be no longer than six hours and probably less given the higher combined output of the alternators.

In practice, we do not often consume more than 50% of availability overnight. That means we can fully recharge in about five hours of cruising. I consider five hours not a long day. A long day to me starts at six hours. We do try to limit our cruising day to four hours so, indeed, there are days when we do not get to full charge. No matter though cuz we always get them to 100 SOC in no more than four or five days which is just fine for FLA batteries to live a long enough life.

I welcome the thoughts and questions of others.

Plenty of boats can get the batteries topped off with a decent day of motoring. But unless you've got solar, etc. or are running a generator a lot of hours, or traveling long day after long day, you won't get them topped off every single cycle. And that's what FF was getting at. If you don't get them perfectly topped off every single time you draw them down, you're not working under the same conditions the life cycle graphs are based on.

 

[twistedtree]

I was curious about whether this was true but it depends on how one defines a "long day". So, I have been experimenting with my setup to see just how long it takes to recharge my 920ah battery bank. I recently installed a Balmar SG200 battery monitor so that I would have accurate information on State of Charge (SOC). This was my experience.

I discharged the bank to 40%, twice. In other words, I consumed about 550 amp-hours. The charger spent 4:45 in bulk charging. Interestingly, the charger went to absorb at 90% SOC while the common knowledge is that this occurs at 80%. I have no explanation for this. In any case, it took 1:15 in absorb time to reach 100% SOC, six hours all together. I did not test to 50% SOC but a simple extrapolation of bulk time charge suggests that a full charge would have been reached in about five hours.

My charger is a Magnum 2812 inverter-charger that nominally puts out 125 amps. The Balmar SG200 consistently showed about 100 amps going into the batteries. The difference can be attributed to house loads.

My alternators are a pair of 100-amp Balmars. If I assume that they effectively, underway, due to heat, etc., whatever, they put out no more than 150 amps, together, that is still way more than what the Magnum produces and still less than the charge acceptance of a FLA 920ah battery bank. So, I think it is reasonable to assume that charging my bank from 40% to 100% would be no longer than six hours and probably less given the higher combined output of the alternators.

In practice, we do not often consume more than 50% of availability overnight. That means we can fully recharge in about five hours of cruising. I consider five hours not a long day. A long day to me starts at six hours. We do try to limit our cruising day to four hours so, indeed, there are days when we do not get to full charge. No matter though cuz we always get them to 100 SOC in no more than four or five days which is just fine for FLA batteries to live a long enough life.

I welcome the thoughts and questions of others.

That all sounds about right.


Where I think the differences between lead and LFP come into play the most is when you anchor out for multiple days, and/or have shorter runs between anchorages.


When anchored for multiple days (and assuming you don't have enough solar to carry all loads and recharge), you will be recharging from your generator. LFP lets you cut the generator time down by a) charging at a higher rate, and b) charging at full current for the entire charge cycle. In my experience this cuts the charge time by 1/4 to 1/3. Plus it loads the generator consistently through the whole process.


Now I think it was in this thread where someone (Sunchaser, maybe?) was not charging fully on generator, and only running through the bulk mode. In that case, there is much less difference between the two, other than available capacity. If you run your lead batteries between 50% and 80% SOC to avoid absorption mode, you only have 30% of your battery capacity usable. With LFP you can get the same charging performance, but utilize 90% of the battery capacity.


In the end, you just need to pick based on what matters to you,

 

[rslifkin]

That all sounds about right.


Where I think the differences between lead and LFP come into play the most is when you anchor out for multiple days, and/or have shorter runs between anchorages.


When anchored for multiple days (and assuming you don't have enough solar to carry all loads and recharge), you will be recharging from your generator. LFP lets you cut the generator time down by a) charging at a higher rate, and b) charging at full current for the entire charge cycle. In my experience this cuts the charge time by 1/4 to 1/3. Plus it loads the generator consistently through the whole process.


Now I think it was in this thread where someone (Sunchaser, maybe?) was not charging fully on generator, and only running through the bulk mode. In that case, there is much less difference between the two, other than available capacity. If you run your lead batteries between 50% and 80% SOC to avoid absorption mode, you only have 30% of your battery capacity usable. With LFP you can get the same charging performance, but utilize 90% of the battery capacity.


In the end, you just need to pick based on what matters to you,

Or if you have almost enough solar, you can use the generator to bulk up in the morning, then let the solar handle absorption during the rest of the day with lead acid batteries. That avoids the PSOC problem, but it does have the downside of requiring more strict usage patterns than LFP would.

 

[catalinajack]

Another good idea. All along in this discussion, in addition to trying to understand the technology, I have questioned some who have asserted that LFP batteries are "better". I have become convinced that they are not, just that they are a different technology , presents different maintenance considerations, but are a good solution to some use cases. This suggestion demonstrated another way to use FLA batteries without having to use a generator to go beyond the bulk stage of recharging. In a sense this method obviates one of the chief advantages of LFP but does require a large enough solar array.

It also demonstrate that, often, there are several ways to solve boating choices, all good, all work, and none wrong. One example would be whether one should have separate batteries for starting instead of using a sufficiently large house bank to also start engines.

If I were planning to go to the Bahamas for weeks every year, I would invest in a large solar array. I happen to have a lot of unused real estate on my boat deck because our dinghy is transom-mounted rather than stored on the boat deck. But, for our use profile, solar (and LFP) would not be a cost-effective choice. With some exceptions, we rarely spend more than three days away from shore power or a long enough run, five hours, to fully recharge our FLA batteries.

Or if you have almost enough solar, you can use the generator to bulk up in the morning, then let the solar handle absorption during the rest of the day with lead acid batteries. That avoids the PSOC problem, but it does have the downside of requiring more strict usage patterns than LFP would.