[Archived]

Everything seems to indicate that that is the direction we are moving towards and you are probably right that Liberty will be there first. I can only imagine what the cost will be for those first generation coaches. For me, I’m just trying to figure out how to use technology to simplify the lifestyle that we think we want to have and not complicate it. Using technology in this way only makes sense if it is reliable and I do not want to be on the bleeding edge, and in 17 months (when we retire) hopefully we will not be.

Good to hear that you seem to be over your battery issues.

[Larry]

A very interesting discussion. I replaced a 1350 Ah flooded bank with 1200 Ah of LFP in 2012…on a boat. It is impossible to compare on equal terms. The performance off grid is night and day different. However, that said, they still seem to loose about 8-10% of capacity per year. Notably, this observation is not universal. Other cells seem to be doing better. See the mentioned Cruisers Forum discussion for more. RC Collins posting as Mainesail has had better results, but over a shorter timeframe. Our cells are the same as the Technomadia RV Bloggers which have observed the same things I have.

Used for lots of cycles or at dock, doesn’t seem to matter much on capacity lost. But 1200 Ah of lithium is equal to 2000+ Ah of AGM because of the usable range of 10-90% SOC vs 50-100% of AGM. So even degraded, the lifetime is long on a comparative basis.

My other direct experience was with a customer who purchased 160 100Ah cells and they got stored for 1 year prior to install. Based on sampled capacity testing, these lost 5-6% over the year. These Forzatec cells. Digging into this, there is some research supporting capacity loss over time. Temperature does seem to count for something. Both the storage of these cells in a warehouse in Florida and my cells in the engine room were not exactly cool places. Research has also shown a correlation to high temps and capacity loss.

2000 cycles seems like a myth, I’d put the number at 800-1000, unless you can do 2000 in a short timeframe.

I’ve also had a cell failure, one in 48. The 160 cell customer had 2 of 160 fail shortly after install. Finding the problematic cell is not so simple in banks with 10-12 cells in parallel. The failures I’ve observed benign, a high resistance internal short causing high self discharge. Not catastrophic, but still a PITA.

Also as pointed out, the adjustment to systems designed for regular batteries is not trivial. One example is alternators, they don’t take well to losing a battery on the fly if the battery management system decides they are over or under voltage at the cell level and disconnects the bank. Tends to blow diodes on an open circuit, so if the lithium battery disconnects, there must still be some sort of load. I keep 200Ah of AGM in parallel. Not an elegant solution, the Lithium have the parasitic load of trickle charging the AGM when no charging sources are online.

Don’t let anyone convince you there is a drop in replacement. That simply doesn’t exist!

There are some new conversions coming out now with Lithium designed in from the start. There is a lot of promise to the technology. But until there is more positive experience, if you don’t boondock months at a time, or have a situation where weight is critical, or like to tinker with the latest tech, it’s going to be prudent to let this shake out a little more.

Further, LiFePO4 is the only lithium chemistry reasonably safe enough for most people to play with today. And while that’s a good bet with proper precautions. its not guaranteed. Other chemistries are not as intrinsically safe and require more engineering to keep away from the Boeing or Samsung like safety related problems.

Bottom line…for most of us…watching developments is wiser than adopting in the current state of affairs. In my opinion anyway….

[AL]

Andy, I don’t want to sound like I have a clue about batteries and technology, but what is your experience level with AGMs that you are ready to kick to the curb?

Among our PC members we have folks that range from power pole to power pole users ro folks that dry camp a lot and I am not getting any sense that a typical set of AGM isn’t going to last from anywhere from 3 to 5 years, trouble free.

And I get it that you are averse to running a generator more than you have to, but very few of our coaches have generators that even make as much noise as an air conditioner. Surely it isn’t the use of fuel that has you concerned?

[Deleted User]

Hi Bob, I would not put to much credence in my EE for the applications relating to Prevost ownership. One advantage that I may over most is just being able to understand the theories and logic behind different designs.

Tom moved most of the dialogue from this thread over to the Lithium battery thread where you have also been active. I’ll comment here but if you could answer in the other thread it might have more meaning for those that read it in the future.

I think that the technology to make the new battery chemistry a success is here but the execution in high volume is still yet to be proven. I will point out though that if you are using the same technology as the Technomads you should expect to have a similar experience so I’m sure you were not surprised. They acknowledge that they were on the bleeding edge and sounds like you were also since you gave the technology. However, they freely comment that technology has improved so your YMMV but probably on the positive side with newer technology.

I would be curious to get your take on the battery construction shown on http://www.lithiumion-batteries.com/ watch the “how it’s made” video which is in the middle if that page under Video Sources. How does that compare to what you currently have? I won’t jump in to this market until I see customer and independent objective reviews and right now they are hard to come by. I’ll probably stop by their booth in January at the Hybrid and Marine show in Tampa and see what they have to say.

If they can perfect their bms to work as they did describe then there is a market for their product. Again, I need to see proof that the execution of the claims are real and not just marketing hype.

I would love to get rid of the absorb cycle in the charging regiment and not have to worry about having to top off the batteries before heading off to fly fish in the early morning while dry camping. That is not going to happen with AGM’s without some negative effects on life expectancy so for now I can only hope that my AGM’s will hold out long enough for the current claims to prove themselves out. I’m hopefull but not holding my breath.

[Gary]

We are selling a 1985 DeFever 44 sun deck trawler. Or trade for a Prevost?

Great Bahamas, Caribbean or Great Loop boat. Send me an email if you want more information. Bob at Ebaugh dot Net

[DON]

I see where the latest Liberty offering has a high voltage DC system and a 12.5K ONAN generator. Very interesting. I read elsewhere that Onan is/has developed a system where the smaller generator is augmented by inverters when loads exceed the capacity of the generator. The inverters are in electrical sync with the generator, paralleled.

[Robert]

I don’t have a system like Les describes on my coach, but after watching our coaches grow in the sense of how much electrical power they could ingest. I saw my generators grow along with the load potential to the point where mine is now 20KW.

Along with the increase in electrical consumption has come slides which grow the size of the coach meaning the coach now also has more interior space to cool. Where I am going with this is I question how a small output generator can cope, unless when boondocking it is run continuously. If someone opts to stay off a power pole that means the coach is going to require the use of its on-board power. That’s perfectly acceptable when there is a big generator. We would have to try very hard to overload a 20KW output.

But if we have a system as Les describes we need to start out with fully charged batteries and are running the generator if we intend to run 3 or 4 AC units plus have all the other electrical loads such as aux compressor, water pump, HW tank, interior lights, maybe the grille or cook top or microwave. At that point we likely are drawing from the batteries.

This scenario gets real bad real fast if instead of having the generator running all the time we rely on batteries alone and expect autostart to kick on the generator as needed to charge the batteries. If you add the inverter charging as part of the loads listed above the generator is going to be incapable of handling everything so some energy management is going to be required.

I realize few of us push our coach and its systems to the limit, but I can easily see someone that pays as much as these cost expecting to do just that. I am likely missing something here and everything may actually be OK with a set up as described by Les, but I would need to see the proof. This is not in my opinion a debate about Li batteries, but a concern that energy we use has to be provided or restored and I cannot get my brain wrapped around a system that is getting smaller in output while the ability to consume electric seems to get greater with every year.

[Archived]

The way to think of this is averaging out the load on a generator. A generator sized for the absolute peak demand is going to be chronically underloaded some of the time. There are really two different power operating profiles for a coach, air conditioning needed and air conditioning not needed. The daily power requirements of the two are substantially different.

Lets take with air conditioning first. In the hottest climates, the genset needs to run 24/7. But even a power hungry coach won’t average near 15 kW of demand in the hottest climates. So for discussion purposes, size the genset for simultaneous running of all A/C units plus about 1.5 kW. A 9-10 kW generator gets the job done. For peak demands, the genset is supplemented by the inverters powered by the batteries. Other times when demand is reduced and a compressor or two goes offline, the battery gets recharged. This keeps the generator more fully and evenly loaded. And the batteries at or near full charge.

However operating in a marginal climate, you may only average one A/C compressor running, so you may find yourself running a turbocharged 20 kW genset for 3kW of needed power. Now you can occasionally shut off the generator and run for a period off battery power. At 50-60% SOC the generator auto starts and carries the load while recharging the batteries. If there is a sudden cooking demand, there is still battery capacity remaining for the excess power requirement. Or…just leave the genset running, but while not optimal, this load is less likely to cause harm to a smaller naturally aspirated diesel.

Operating without A/C, it would seem near impossible to properly load a big generator. Even with full on battery charging, that’s maybe a 4 kW load on many coaches. Call it 5 with all the other misc loads averaged out.

Is this worthwhile? Not sure. Electrically it’s all possible. I’ve been told the sweet spot for a generator is about 75% of its rating. I’ve also heard extended periods at no load is bad. What is a minimum safe extended load? No idea.

There is an excellent white paper on this concept here:

https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

[Archived]

I have never come close to running my generator at 75%. That would be a continuous 120 amps approximately and that is never going to happen, even with all 4 ACs running continuously. Even if I was grilling the entire time the water pump was running, the aux compressor was running, the HW tank was drawing current and the microwave and cooktop were both working, and I wanted a cup of coffee while my wife dried or curled her hair.

And I have run my generator for hours with very light loads. So far so good. I’ve never had a generator issue. And apparently entertainer coaches do not either, with their 5 AC roof top AC units being the principle current draw. They also are unlikely to run anywhere near 100% of the time, because like ours the only time more than 2 are running is when the sun is beating down on the coach and it is a hot day.

But it sure is nice knowing I have enough generator capacity to deal with the heaviest imaginal loads.

[Jerry]

And some of us piggyback our race car trailer off our bus gen. 12.5kw seems a little wimpy to me.