LiFePO4 conversion

[Tim22]

I am planning on upgrading my batteries to LiFePO4 and would be grateful of comments on the attached system design. This is a work in process so details such as fusing etc. are not included. This is really just a component layout.

This design proposes that all charging sources go to the FLA Start / Backup Bank and then charge the LiFePO4 house bank via a DC to Dc charger. I’m not sure if this is feasible as most information on the DC to DC chargers only seem to address charging from the alternator.

Some of my main concerns are that the start / backup FLA bank always be charged and ready should the House bank fail. I also want to ensure the protection of the alternator. Finally, I share a shore power outlet with other boats so I need to be mindful of how much current I am drawing. I understand that the Victron Multi Plus allows the max current For charging to be programmed.

Thanks for your comments and suggestions.

Tim

 

[IStream]

Okay, if nobody else is going to jump in here, I might as well.

First, as you mentioned, all your charging sources will need fusing. Some might argue for manual cutoff switches as well but I personally don't like them due to too many age-related failures. I prefer to pull fuses when working on the system.

Second, except for the caveat below, I'd strongly suggest that you charge the house bank directly from the Victron/solar/alt and have the Sterling charge the start bank from the house. For one thing, I believe the Sterling can be equipped with a temp sensor, which your FLAs will benefit greatly from but your solar and alternator may not. The house bank doesn't need temp-compensated charging. The other reason to swap is that you're going to have a much slower shore charging experience as diagrammed when you're not shore current-limited because the Sterling can only do 30A DC. I don't know which Victron charger you're planning to use but keep in mind that even a 100A / 12V DC charger will draw less than 10A from the shore power connection. You could easily share a 30A circuit with two other boats and as long as all three of your aren't charging lithium banks or running electric heaters at exactly the same time, you can still be a considerate neighbor.

The caveat above is that you need to pay close attention to the charging profiles programmed into your solar, shore, and alternator regulators so make sure they're compatible with your lithiums. If they can't be programmed and you don't want to upgrade them to something that can, that would be the best argument for charging the house from the start bank (assuming the Sterling can be programmed for the lithiums). However, you need to pick your poison. If your solar / alternator can't be equipped with battery temp sensors and you'll do a lot of charging with them, you'll potentially be doing damage to your FLA bank.

Anyway, FWIW.

 

[Tim22]

Thanks for jumping in.
I would prefer to have all the charging sources go through the house bank but everything I read tells me that the LiFePo4’s will damage my small hitachi 55amp alternator pretty quickly. If there is something I can install to protect the alternator then I would go that route.

Another thought is that I have been looking at the 125 Ah Lithionics battery and see that it has sufficient cranking amps to start the engine. This is a bit of a game changer as I could drop the FLA’s all together and maybe have a house and reserve bank of LiFePo4’s. One 125 ah in each bank is more than I need and I would still have to resolve the alternator charging problem but I would be happy to be rid of the FLA’s Agm’s and any other heavy batteries.

In terms of components I would use what I have that is suitable. I gather that my sterling ultra charger is not good for lithium so would swap it out for the Victron Multi Plus 2000 which gives me an inverter also. I’m not sure if the profile for the Blue Sky solar controller would work, but it too could be replaced. Other than that there is really just the Balmar Smart Guage which may or may not be useful.

The new version would look something like the attached

Thanks
Tim

 

[IStream]

Some background/disclaimer: I have a ~400Ah 12V lithium bank consisting of 3 Valence 135Ah U27-12XP modules paralleled and managed with the Valence external BMS. I don't have a start bank. I use my house bank to start the engine and carry a ~$100 portable Lithium jump starter like this:

https://www.amazon.com/NOCO-GB40-UltraSafe-Lithium-Starter/dp/B015TKUPIC/ref=sr_1_3?dchild=1&keywords=noco+boost+plus&qid=1594441471&sr=8-3

as an emergency backup. I've tested it but never needed to use it in anger. I charge it at the beginning of the season and it stands ready for several months without needing a recharge.

Given this background, you won't be surprised to find that I think it's a terrible waste to have an expensive lithium battery as a start bank. You're better off paralleling it with the other house lithium battery and doubling the size of your house bank. Most reputable "drop-in" or BMS-equipped commercial lithium batteries are capable of delivery 1C current indefinitely and 2C-3C current for 30 seconds at a time. Given this, you can probably get away with two 100Ah batteries in parallel but if you put three ~100Ah Battleborn, Mastervolt, Victron, or similar batteries in parallel, you won't have any current limit issues at all. Lithionics are great but they're extremely expensive and if the only reason you're considering them is their starting current capability, just be cognizant of the fact that you can achieve the same current capability by going with a different brand and adding a third battery in parallel for probably the same or lower cost.

Regarding the alternator, the OEM Hitachis are notorious for their aggressive thermal self-protection. You very likely won't burn it up with a lithium bank but you probably can't count on getting 55A out of it for more than a few minutes before it throttles itself down to 25A.

It's unclear if you already own all the components in your diagram but if not, keep in mind that by going to a single larger house bank and deleting the start bank, you'd also eliminate the need for the Sterling unit and one of the battery monitors, which is money you can put towards batteries, a programmable solar charge controller, and/or a larger alternator with programmable voltage regulator.

Anyway, that's my two cents.

 

[heritage]

I would prefer to have all the charging sources go through the house bank but everything I read tells me that the LiFePo4’s will damage my small hitachi 55amp alternator pretty quickly. If there is something I can install to protect the alternator then I would go that route.

I use a 20 amp dc to dc charger to reduce the load on my small Hitachi alternator. The charger has a lifepo4 setting on its output. It is wired in parallel with the alternator and a small agm reserve battery on its input side. I only have a few hours of cruising with this set up, but I don't anticipate any problems, as the temps of the alternator and charger remain normal. My amp meter shows at startup 20 amps to the lifepo4 batteries and then falls to about 18 amps after an hour. This could be due to the throttling of the Hitachi alternator that was mentioned in a prior posting.

 

[Tim22]

The more I think about the change to lithium the more I think it best to have two banks each of which can start the engine, pull the anchor and do whatever else is required. My experience has been that engines fail to start at the most inconvenient times like when dragging an anchor transiting a shipping channel, or entering a new harbour. At times like these it is comforting to be able to switch quickly to the other bank and carry on. No guarantee that the cause is battery related but it does eliminate one cause of failure. This is why I would like a LiFePO4 with starting capability. Unfortunately I don’t have room for a 3 battery bank. I can fit two but I don’t know that this would provide the necessary cranking amps.

Tim

 

[Tim22]

Hi all
I have been doing more research and refinements to my LiFePo4 upgrade plan and would be interested in your comments on the attached drawing.

Some notes
1. I have decided to leave the Alternator charging only the start battery. I run the engine so little, and the alternator is so small that it is hardly worth installing a B to B charger
2. In normal usage the start / reserve battery (probably AGM) would be used to start the engine and run the windlass. The house (LiFePO4) would power everything else. If necessary the house bank could be switched to also power the starter and windlass. Similarly the start/reserve could be switched to power the house if possible. This is done with the two 1-2-off switches. I am particularly interested in comments on these switches as it seems too simple to work properly and not cause some sort of problem.
3.The solar panels are wired through a 1-2-off switch to allow the charge to be directed to either the start/reserve or house bank. Each route has it’s own solar controller set to the chosen battery profile.
4. Main charge from the multiplus Charger/inverter Goes to the house bank while the 4amp trickle charge goes to the start reserve.

Thanks for your help with this
Tim

 

[Tim22]

Sorry, I’m not trying to combine the two banks but rather let either of them power either of the two load busses. I have updated the drawing to show 1-2-off switches (no 1&2)

Thanks
Tim

 

[heritage]

OK, I see what you are doing. Should work fine, but I am not willing to give up being able to charge the house bank with the alternator. My alternator is also small but is still capable of charging the lipo batteries at 20amps with the dc to dc converter. I only have 100 watts of solar but am adding another 100 in the future. Pat

 

[Tim22]

Thanks Pat
I am thinking I can add a DC to DC charger later if it turns out I need it.

TIM

 

[CarlN]

It really is much easier to install a battery combiner between the start and house banks. That way when either one goes above 13.3V it will charge the other. And there is no way that the start battery can be accidentally drained flat.

Use an external alternator regulator (e.g. Balmar 614) with a temp sensor on the alternator. This will get many more amps out of your alternator but will also protect it against being overloaded by the Lithiums (the optional temp sensor on the alternator automatically reduces amps if it is getting too hot). Also use the Balmar "Belt Manager" to derate the alternator a bit. Won't reduce amps much and much kinder to the alternator. If your alternator is internally regulated there is likely a kit available to convert to external regulation.

I assume you are getting a drop in Lithium? These typically charge at 14.2-14.4 absorption which is fine with with AGMs too. The Lithium's shouldn't have temperature compensation but the slight difference in voltage is not going to bother a typical start battery which is usually fully charged anyways. Temperature compensation is imporant with big house banks but not so much with start batteries which aren't being discharged a large percentage..

With this system you can connect your alternator to which ever bank you prefer. Since the start battery is normally fully charged, the battery combiner will just funnel the alternator charge to the house bank. And there are no switches you have to remember to set (other than a on/off for each bank). It's pretty much foolproof.

Victron makes a great combiner. It also has a feature where you can wire a push button at the helm that will combine the batteries for 30 seconds if you need an emergency start.

Finally, there's very little reason to spend the extra money for AGM or even deep cycle for a start battery. A regular car lead-acid battery will be fine and have a great CCA rating to turn over the engine. Just replace it after 5 years. And wet lead-acid batteries are not at all picky about charge voltage so they'll be even happier at the Lithium settings.

Victron Energy Cyrix-ct 12/24V-120A Intelligent Battery Combiner

 

[Maine Sail]

It really is much easier to install a battery combiner between the start and house banks. That way when either one goes above 13.3V it will charge the other. And there is no way that the start battery can be accidentally drained flat.

You need to be careful using a standard lead-acid VSR on LiFePO4 batteries. A LiFePO4 bank is going to need to be at or darn near 0% SoC before a Cyrix CT will open and isolate the batteries. This means your AGM and LiFePO4 bank would be in parallel near 100% of the time. In other-words, when a LiFePO4 bank is at 0% SoC a lead-acid bank is at 100% SoC.

Victron does however make a version of the Cyrix that is specifically for LiFePO4 voltages. Of course that does not help alleviate the loads placed on the alt, by the LiFePO4 bank, and if you feed the start bank first, you can wind up with a relay-cycling event....

 

[Hayden Watson]

One option that gets used a lot on RV's is the Li-Bim 225 which you put between the LFP bank and the charger. It closes the FLP side to charge for 15 minutes than opens to let the alternator cool for 20 minutes. When the LFP resting voltage gets to 13.4 it opens to stop charging. It doesn't give you as much charging as you would get from a lith ready external regulator.

 

[Maine Sail]

One option that gets used a lot on RV's is the Li-Bim 225 which you put between the LFP bank and the charger. It closes the FLP side to charge for 15 minutes than opens to let the alternator cool for 20 minutes. When the LFP resting voltage gets to 13.4 it opens to stop charging. It doesn't give you as much charging as you would get from a lith ready external regulator.

We have a customer with Battleborn batteries who burned up his first Hitachi alternator.

He bought a cheap Chinese replacement alternator and one of the Li-Bim units thinking it was the greatest thing since sliced bread.
Three weeks later he ripped it out, contacted us and wound up installing a Balmar XT170 and a Wakespeed WS500 regulator. He is now charging at 80-90A vs. the knock off alternator, and Li-Bim, which was producing about 16--19Ah for each hour of charging. Once he decides to add the serpentine kit he can bump it up to about 120-130A.

 

[Hayden Watson]

He bought a cheap Chinese replacement alternator and one of the Li-Bim units thinking it was the greatest thing since sliced bread.
Three weeks later he ripped it out, contacted us and wound up installing a Balmar XT170 and a Wakespeed WS500 regulator. He is now charging at 80-90A vs. the knock off alternator, and Li-Bim, which was producing about 16--19Ah for each hour of charging. Once he decides to add the serpentine kit he can bump it up to about 120-130A.

I fully agree. As I said in my post, the best you can get from a Li-Bim is 15/35 = 42.8% of your charging capacity. It was more in response to people who refuse to upgrade their alternator to proper regulation with alternator temp control. That very reason is why it is more common in the RV market because they are less dependent on charge from motoring and when the travel, they often run for a longer amount of time.

 

[Maine Sail]

That very reason is why it is more common in the RV market because they are less dependent on charge from motoring and when the travel, they often run for a longer amount of time.

RV's also have massive stock alterntors compared to boats, and they're not really doing much work, so in the 15 minutes that it is ON you are actually getting a much higher charge rate than the diminutive 30A - 80A stock alternators found on most boats can deliver when warm.

Heck even my truck, charging a single Group 24 battery, is fitted with a 180A Denso hairpin alternator. It barely of ever breaks a sweat and is why the original alternator is still purring along just fine at 250K.

 

[Tim22]

I am continuing to simplify my design to the point that I now have virtually two systems. The AGM is charged by the alternator, 20w solar, and 4A secondary MultiPlus 2000 charge source. The LiFePO4 bank is charged by 200w solar and the Multiplus primary charger. The systems only intersect at the two load selector switches which allow either bank to supply either load bus. The version 5 drawing is attached

Tim

 

[sirk76]

Tim I'm interested to hear more about your setup. Have you started implementation yet? I have bought Lifepo4 280Ah cells from China and built my own battery. Still testing at home and trying to determine the best way to integrate into the charging circuit. To start with I believe I will charge with my small amount of solar and inverter/charger. One debate I have is if I should replace my aging Freedom 25 inverter/charger. While anchored out I can supplement solar by running the generator for a few hours every few days.

Looking forward to hearing your progress.

Kris

 

[Tim22]

Hi Kris
Installation is underway and most of the components are installed. I am having to build a new battery box for the LiFePO4’s and also a switch box for the three Blue Sea switches. I have attached the latest iteration of the drawings as they have changed quite a bit.
As you will see, I have fused the LiFePO4 bank with a 250A T Class fuse which is the recommended size for the inverter. I may have to upsize this and add a separate TClass for the inverter if it turns out to be too small.

Tim

 

[Renegade135]

I like your approach of separating the LIFEPO4 batteries from the alternator. It seems the alternator adds a lot of complexity to the system when connected with Lithium. Is 200 W a good match for the 200AH of battery capacity ?