[Jon]

I got a headache after 30 minutes and had to quit.

The example of life cycles stated for Lifeline 31XT’s as 300 compared to Lifelines data of 1,000 at 50% DOD is certainly questionable at best. That claim would require absolute verifiable data of DOD on each cycle during the life of the batteries in the Marine application noted.

Interesting article with lots of good information on Lifepo4 and those that think Lifepo4 is a drop in deal will learn otherwise regardless what the marketing info claims.

[David]

Excellent article. It’s taken me months to accumulate that knowledge found in that article.

Eventually I assume I will be going LiFePo4, probably when my lead acids show signs of end of life. I was planning on assembling my own battery, using something like the REC BMS, integrated with Wakespeed W500 alternator voltage regulator. I have not checked yet if the Trace inverters can be programmed to work with a LiFePo4 charging profile. If not, was going to move to Victron inverters.

[Jerry]

Hi Group,….I have made the change also. The article is full of info, but lots of words. Seems like the yacht industry has lots of info. I see folks who add a AGM battery to their LiPo system for certain loads.
I removed 6 AGM 8D lifelines. I have been using them since the 1990’s, in 3 different coaches, this is the 3rd house bank going into my 1997 Royale in the 7 yrs so far. I would like to see these 4 Amperetime 200a 8Ds preform.
I have 2 Magnum 2812’s working with the 800a bank. I am now setting up the charging program for my type of coachlife, and I want to thank Don for his input in this new world of batteries.

If I can recharge the LiPo bank in an 1.5hr of generator run, that is a plus. I will be posting with real world experience.

Jonathan Fine
1997 XL40 Royale #201

[Marshall]

One of the problems with doing these kinds of articles is the author usually only has direct experience with one coach or boat setup – the one they have – but have to use words to describe a bunch of different setups for all the potential readers. As in the case of our buses where some are 24v start, 12v house, some are 24v start and 24v house, and some are a hybred, that can take a lot of extra words. The one thing most in dispute is the phrase “drop in replacement”. That is never the case if you want to recharge from shore/gen power, engine alternator power and solar power. You will have to add some new electronic gizmos to make that work safely.

From the magazine articles and group presentations I have made the most difficult thing for the reader/audience member to get straight is you cannot directly connect any form of lead acid batteries with any brand name Lithium batteries. Most RVs, including our bus conversions, have some form of battery isolator or combiner designed to directly connect one lead acid battery to another under some conditions. To replace one of those lead acid battery banks with Li means you have to also get rid of that combiner or isolator and replace it with something else, most often a B-to-B charger of some sort. Once the reader/audience member gets this concept clearly in mind, my experience is they usually get quickly past the problem with the “drop in replacement” phrase.

The second thing most often in dispute is the notion that all Li batteries are the same – they are definitely not – and you cannot safely interconnect different brands or capacities of Li batteries. The type of cell used, the way they are wired internally and the type and capacity of the BMS can all be different one Li supplier to another. The only way to really tell is to take the batteries apart and look for yourself or have someone you trust do so and report what they find.

These things said, the one indisputable for most users is the superiority of a properly designed house Li battery bank over most stock Lead Acid battery banks in real world use for our Prevost conversions. If you live power pole to power pole, or religiously run your generator any time you are not plugged in, then the type of batteries used won’t matter much. But if you dry camp at all, even over night, you will see a great benefit.

Jerry

[Ron]

The other thing I forgot to mention, and something I believe Jerry’s comments might be relevant to, Is having 2 banks of 12v, which each bank might have 12v loads, and the two banks in series provide 24v to the inverter, but also battery balancing device to ensure both 12v banks are equally charged (as the house loads will draw unequally from two banks). This I believe would not be a good idea for LiFePO4, or at least I would not be comfortable with a setup like that unless I knew the balancing device was up to the task.

If I were to go 24v LiFePO4, I would assume I would need to include a 24v-to12v power supply to feed all of the house 12v loads. Not sure how many amps required, maybe 100 or so? Victron has these power supplies and can be paralleled.

I’d be really curious if anyone has drawn up a detailed schematic of what they did when doing a conversion.

And to throw another wrench into this, why not 48v system? I think the biggest detractor here would be alternator charging. 48v alternators are super expensive from what I have found (~$3k). Perhaps keeping a small 24v lead acid bank for the alternator and adding a 24v-to-48v charger fixes this, but then you have more things that can break. Or maybe just use existing chassis 24v, have both alternators charge that, and add the 24->48v charger to charge house.

48v is kind of interesting to me because there are a couple true 48v mini-split heat pumps out there, and if you could make those work, you could heat/cool without any inverter requirement.

[Ed]

I have never collected data on charge cycles on my house batteries, and I could never predict their life because at 5 years my house batteries were replaced with new ones.

But I also never used autostart which tends to take the DOD down to a very low level. My batteries in all but extremely rare situations were always charged when batteries were at 50% or above.

I now have LiFePo4 house batteries and since they provide more available power than my previous AGM I am likely well above 50% when they get recharged. According to the charts and curves provided by a number of Li battery providers I should get about 30 to 40 years of life, something I should never say out loud because it doesn’t seem right

I am doing everything by the book. My Li batteries are in a heated compartment so they have never been below 50 degrees. When being charged the charge rate is modest compared to the rate allowed by the manufacturer. Additionally my Outback inverters are set for “silent mode” which means when at 100% the inverters stop bulk and absorb charging and go into float mode and then are not provided with any charge at all until they get to 25.2 or 25.4, at which time the inverters go back to float charge until they reach about 26.6 or 26.8. As long as the coach is not being used and is stored the Li batteries are stored in an ideal range.

I like the Li a lot but I will never tell anyone I made the choice for financial reasons. When I bought them it made no financial sense, other than I saved a lot of weight and in exchange got batteries that still had a SOC well above 505 even with all normal house stuff working like the refrigerator, water pump, aux compressor, etc on all night.

[Archived]

Andrew, review Jon’s LI conversion in the article section for his Liberty. Jon’s Relion’s are 24v in parallel and uses 2 DC to DC converters for his 12v needs.

[Michael]

Actually I have three 24 to 12 converters but the point is and I forget to mention it, the house on my coach was originally set up for series/parallel battery connections. The Li literature said that was OK. It was not. When I found out charging Li batteries through and equalizer was not going to work they were replaced at Relion’s expense with all 24V and the converters added to take care of the 12V needs.

---

Mike Harper

2004 Marathon XLII

[Jerry]

Another thing to keep in mind in this discussion is the economics and quality of offerings pertinent to a Li conversion have changed dramatically in just the last couple of years. This is true both in terms of the Li batteries themselves and also of the needed extra/replacement electronic components. Where Jon’s comment about not making the change for economic reasons was true for him when he did his conversion, for many of us that would not be true today.

The price per available amp hour for seemingly good quality, well supported batteries has dropped by at least 50%. The price for seemingly good quality B-to-B chargers, alternator protection devices, battery monitors, and MPPT solar chargers have also seen a similar drop in price. What has not changed in price is the cost of quality marine grade multi-strand large gage wire, the required terminal ends and the crimping devices. Be especially careful with the inexpensive crimping devices. Many, especially the hydraulic ones, are incapable of making the gas tight crimp you need to prevent unwanted resistance at the wire connectors. The crimp may look “good” but not be electrically good which can drag down the performance of the whole system.

Jerry

[Billy]

Generally speaking, the simplest Li conversion to make is where you have two house inverter/chargers, one for each side of the coach. Leave at least one lead acid battery in the system and install two new Li house battery banks.

Connect the alternator charging to that/those lead acid batteries. Be sure any DC isolators or combiners are attached only to the lead acid battery(ies). Use two B-to-B chargers, one connected to each of the two house Li battery banks, to keep them and the start battery bank charged from the alternator. Connect each inverter/charger to one of the Li house battery banks.

The two B-to-B chargers will keep the Li house battery banks charged while driving. The two inverter/chargers will keep the each of the house Li battery banks charged while on shore/gen power and also will keep the Li and lead acid batteries isolated from one another at all times.

Use two separate MPPT charge controllers connected to the DC side of the inverter/chargers to solar charge the Li house battery banks while parked. If you feel the need to keep the lead acid battery charged while parked, add a simple AC to DC battery converter/charger connected only to the lead acid batteries.

Again, generally speaking, the most difficult Li conversion will be where your existing set up allows you to run one or more AC units from the house batteries while driving or where you are now wired for the house battery bank(s) do load sharing with the incoming shore or gen power lines.

When selecting the necessary electronic components, be sure to keep in mind the possible amp loads you will be putting on those components. Over engineering here will be a blessing. Under engineering here can lead to premature failure. Also, keep in mind the fact that Li batteries experience very little self discharge so they do not need to be connected to a charger while parked unless you leave the inverters on and one or more AC loads on. Your residential refer, incandescent light bulbs and any form of resistance heater will be the largest potential loads so make sure they are off, not just turned down.

Jerry