Lithium Battery Upgrade

[joe_db]

Either charge the start battery and let the DC-DC charger work or charge the lithium battery directly.

[joe_db]

Don't forget the majority of marine chargers with a lithium setting do NOT work correctly, they will overcharge the battery.

[W2ET]

So the DC/DC hardware eliminates the need for an isolator (yuck!) or combiner?

How long as this hardware been around?

Bill

[joe_db]

I am not sure exactly, I know I installed a few back in the mid 1990s. They are not a new idea. They do replace an isolator or combiner.
* of course the 90s versions didn't have lithium settings, Bluetooth, etc. etc.

[edwardc]

Has any forum member accomplished a partial or full upgrade to lithium batteries? Starting battery, alternator, one or more house batteries, control modules, solar panel or windvane interface, inverter, monitor, etc.?
Bill

Bill,

Sorry for the less than timely reply, but I've spent the last 10 days recovering from Covid and didn't have much energy.

About 2 1/2 years ago, I started a Lithium battery upgrade project. Unfortunately, family health issues, followed by personal health issues have twice caused this project to go into limbo for an extended period.

But during that time, I've done a tremendous amount of research, and am finally back at work on it. The prototype system has been assembled and tested on my workbench, and is ready for install.

As mentioned by others, Lithium Iron Phosphate (LiFePO4) is the chemistry of choice for boats due to its high degree resistance to thermal runaway and fire. Going heavily by the information provided by Rod Collins (MaineSail), I determined (at the time) that virtually all LiFePo4 batteries with internal, built-in BMS (Battery Management Systems) did not have sufficient external communication and control to meet the somewhat unique needs of a marine installation. Based on this, I purchased individual LiFePO4 cells, and an external BMS.

The cells I purchased are made by Chinese manufacturer EVE. I took care to select a Chinese distributor who had good ratings AND a warehouse in the USA, making potential warranty returns economically possible. I purchased eight cells with a rating of 270 Amp-Hours each for a total of just over $900. All tested perfectly. It takes four cells in series to come up with a voltage that is just a few tenths of a volt under the specs of a 12V Lead-Acid battery. Thus, by wiring the cells in a 2P4S configuration, I end up with a 12V 540Amp-Hour battery. This pack takes up slightly less volume than my two existing Group 31 batteries (200AH total), weighs just over half as much, and has over two and a half times the raw capacity.

But that doesn't tell the whole picture. Lead Acid batteries should only be discharged down to 50% of capacity to maximize lifetime. So my 200AH lead-acid batteries only have 100AH of usable capacity! And it gets worse! Lead acid batteries charge up to 80% pretty rapidly (known as the Bulk charge phase). The last 20% to get them up to full (known as the absorption phase) is very slow. On my boat, this phase requires running the engine or generator for FOUR MORE HOURS (!) to complete. When I'm out cruising and anchoring, I can't afford to burn up that much fuel, so I usually stop at 80%. This means that I'm almost always operating between 50% and 80%, giving me only 30% (or about 67AH) of usable capacity!

Contrast this to LiFePO4, which can safely be discharged down to around 10%, and stay in bulk charge up to 95%. This gives me up to 85% of usable capacity, or about 450AH, or around six times the usable capacity!!

The BMS I've selected is called the REC Active BMS. I chose it for several reasons: 1) Rugged all metal hermetically sealed enclosure 2) Single MIL grade waterproof connector for all connections 3) Responsive manufacturer 4) CANBUS, compatible with Victron equipment 5) Switchable external discrete lines that can be used to signal chargers of an impending battery disconnect 6) easy WiFi configuration 7) Uses contactors instead of Mosfets for high current switching

My plan is to install the system in phases. Initially, i will leave the 200AH lead acid batteries in place, and have the alternator charging them. They will normally be used for starting only. The capacity is excessive for that, but I will also wire a battery changeover switch that will allow them to be used as an emergency house bank in the event of a failure of the (complex) Lithium system. This also avoids "Load Dump" issues with the alternator in the event of a BMS disconnect.

In this initial phase, my non-lithium-ready shore charger will also remain attached only to the Lead Acid bank. The Lithium bank will have two sources of charge: A Victron solar controller hooked to 400W of solar panels, and a Victron DC to DC charger from the lead acid bank to the Lithium bank. This initial phase should allow me to use the system and work out any wrinkles.

Later phases will involve switching to a Wakespeed alternator controller for charging the Lithiums directly, and a new Lithium-ready Victron shore power charger, as well as reversing the DC to DC to charge the Lead Acids from the Lithium. Some sort of inverter is also in the works.

Per MainSail's recommendation, my system is using 500A contactors, instead of Mosfets, to do the switching. These consume a little power, but are vastly more reliable. I am using an architecture that has separate "charge" and "load" busses that are controlled by separate contactors. I believe this makes the most sense on a boat. Here's why.

The BMS can initiate a battery disconnect to protect the batteries for any number of reasons, including overvoltage, undervoltage, overtemp, undertemp, and overcurrent. In a single bus system, an undervoltage condition would disconnect the batteries from the chargers, requiring some manual intervention to correct the fault. Similarly, an overvoltage condition would disconnect the batteries from the loads, the very thing you need to get the batteries down to a safe level! A dual bus system can be smart about which bus it disconnects, depending on the fault, allowing for automatic correction of some faults.

Lastly, there's the monitoring system. Victron makes a pretty slick device called the Cerbo GX. This device acts as both a "hub" for all of the different Victron physical interfaces (serial, RS485, CANBUS, ethernet), as well as a central monitor and control node. And its compatible with the REC Active BMS too. It can use a dedicated LCD display, or local webpage display.

But its pricey. Over $600. However, the software (called Venus OS) is based on Linux, and Victron has ported the code to the Raspberry PI, keeps it updated, and makes it freely available! I have this installed on an rpi4, with a canbus-USB dongle, and it works perfectly.

I apologize for the long post, but this is just the tip of the iceberg. I'm trying to collect all I've learned into a whitepaper. I'll keep you posted.

[W2ET]

Thanks for all this, Ed.

I'm rapidly coming to the conclusion that the lithium ion battery technology and related hardware is as consequential to the boating industry as AIS was when I first stumbled upon it.

Something like a once in a generation breakthru.....

Bill

ps: I have been known to exaggerate, but this stuff is a big deal.

[W2ET]

Hi, Ed:

When completed, will your system be capable of starting the engine using the house battery(ies)?

Hope you are feeling better.

Bill

[ndutton]

Any cost vs. benefit conclusions?

[joe_db]

Thanks for all this, Ed.

I'm rapidly coming to the conclusion that the lithium ion battery technology and related hardware is as consequential to the boating industry as AIS was when I first stumbled upon it.

Something like a once in a generation breakthru.....

Bill

ps: I have been known to exaggerate, but this stuff is a big deal.

It is, but don't forget that these batteries STORE energy, they don't create it. If you have a standard A4 with a 35 or 50 amp alternator and take your boat out with the huge lithium bank and cook dinner on the induction stove, watch a movie on the big screen TV, and then spend a restful night with the air conditioner running off the inverter, once you get the coffee made you will then realize you need to run the engine for 8-10 hours to recharge the batteries
The next thing you will realize is you are buying a lot of alternators
* running them 100% for hours a day is more than they can do for long, my big Odyssey thin-plate battery looks like a dead short when low, I need my alternator temperature control to keep it alive.

[joe_db]

FYI: This switch is a SPDT without an "ALL" position. When I set up my lithium bank this switch will allow me to switch house loads to the engine battery if needed.
Besides for emergencies if the BMS craps out, that might be the best way to deal with lay-up periods when you want some power for pumps and so on but don't want to deal with the float issues on the lithium bank.

https://www.bluesea.com/products/11001/e-Series_Selector_3_Position_Battery_Switch_with_AFD

[edwardc]

Hi, Ed:

When completed, will your system be capable of starting the engine using the house battery(ies)?

Hope you are feeling better.

Bill

Yes, I'm all better. Just a lingering bit of sinus congestion and still an occasional cough to clear out the residual gunk in my lungs.

My initial plans did not include engine starting with the lithiums. Looking back, I realize that this was driven by my early designs, which utilized a BMS with 100A mosfet switches.

Since I'm now using high current contactors, I guess the only thing stopping me from doing that is the max current I design and fuse for. Since I don't currently have an Inverter, or other high current loads, I was leaning towards a 100A system. If I ever add an inverter, it would likely be only 1000W (~83A @ 12V), and this would allow for that.

I would have to size and fuse for at least 150A to provide for engine starting, and that would increase costs. But its worth considering.

Neil,

As to cost/benefit conclusions, it depends on whose numbers you believe, and the timeframe you are considering.

First the benefit side of the "equation".

In my current Gel Cell system, the 12V air cooled refrigeration is the "400 lb gorilla". It consumes about 76 AH per day in summer temperatures. All other loads are inconsequential. On days when I motor (such as on the ICW), I arrive at my night's anchorage with 100% charge, and have no trouble making it through the night. When spending multiple days at anchorage, if its full sun, the solar can get the Gel Cells up over 80% by sunset, and I can just barely make it through the night without going below 50%. On even slightly cloudy days, I usually have to run the 1000W Honda suitcase generator (which runs the 40A shore charger) for a couple of hours after sunset to get it up over 80%.

One of my main goals for the LiFePO4 upgrade is to be able to go through about three days at anchor, with no or little sun, before needing to run the generator. The only way to do this with the Gel Cells would be to triple the bank size, and I just don't have room for that.

Of course, there's no free lunch. All of those Amp-Hours I've pulled out will have to be put back. To support this, I've increased my solar panels from 200W to 400W. And I have plans to repair and upgrade the wind generator. But I figure it will still take a couple of days to put it all back.

As for the cost side of the "equation":

100AH marine Group 31 deep cycle Gel Cells are currently going for as much as $500 ea. I was able to find equivalent wheelchair batteries for around $200 ea. Gel Cells have a rated lifetime of about 600 charge/discharge cycles. In cruising mode, you're cycling pretty much daily. This works out to about 2 years (!!) or about $200/year in battery costs. And this is with no improvement in capacity. in order to compare apples to apples, if I triple the bank size (as discussed above) this brings it up to $600/year.

The LiFePO4 cells I purchased have a minimum published lifetime of 2000 cycles. This further increases to 6000 cycles if the cells are mounted in a compression frame.

I roughly estimate my DIY system cost will be around $2500 to $3000.

Using the more pessimistic 2000 cycle number, this works out to about 5 1/2 years cruising. $3000 divided by 5 1/2 gives about $545/year.

So the conclusion of my admittedly simple-minded cost/benefit analysis is that my existing system is more cost efficient than the LiFePO4 upgrade, but doesn't meet my needs, and the expanded Gel Cell system (which I don't have room for) is a break-even with the LiFePO4 upgrade.

But as a boat owner, we've already established that it's not all about cost efficiency (Don't EVER calculate your cost per trip! It'll depress you!).

[joe_db]

The most cost effective batteries are golf cart batteries. Run the hell out of them, 80% discharge no problem, and when they croak get more for under $100 a battery. They will also survive gross abuse for a while, they are not easy to kill.

[sastanley]

Joe, I initially agree with you from an amp hour to dollar value, and they are readily available most anywhere.

I also appreciate Ed's approach, and I have read most of MaineSail's articles too about all of this. Especially now that I have a power boat with refrigeration, and as it turns out, the power boat has less amp hours in lead acid than my sailboat had, and the sailboat only had to charge our cell phones, the iPad, and the nav instruments the iPad were feeding only burned 0.3 amps. My powerboat does have the advantage of two (I think) 70 amp-ish alternators, while I am still learning her systems. There are lots of variations among "350 Crusaders".

I am trying to figure out how to get enough battery to run an inverter that would let the air conditioning cycle occasionally so I could quietly enjoy a cool night at anchor. I would never want to be that dude running a generator.

[W2ET]

Hi, Shawn:

If planning an upgrade, your system raises some interesting questions.

Do you run the two alternators in parallel to combine their charging capacity?

Do you split them, with one feeding the starting battery and one feeding the house bank?

Do you just use one alternator to manage the charging requirement?

How is the system currently configured?

Hope all is well and that you are enjoying the new vessel.

Bill

[Dave Neptune]

FWIW

I mentioned my son's set up earlier on this link. Spoke to him yesterday and he just had his Lith/Iron/Ph battery fail. The manufacturer asked him to run some tests of which he had already run being knowledgeable. The company Renogy asked for him to send it back and they replaced it immediately.
My son thinks it may have "broken" inside which it was due to some particularly hard running off road. He said he had some cream in the fridge however it was about half whipping cream that evening and that was when the battery failed.
He was impressed with Renogy's service department.

Dave Neptune