H49/50 battery replacement

[Davidasailor26]

IMHO charging any LFP pack to 14.6v is at least bone headed and at worst dangerous to your battery. I have seen them and other manufacturers such as Battle Born make that comment but I think it should at best be "NEVER EXCEED 14.6V"
Let's do some quick math.

• 14.6v devided by -cells in series = 3.65v per cell.
• All of the cell manufactures say that the cell voltage should never exceed 3.65v.
• To charge to 14.6v the battery will need to be in perfect balance with a delta of 0.00v with all cells at exactly 3.65v.

Lets assum your battery is extreamly well balanced with only one over achieving cell with a 5mv delta. If you charge to 14.6v your cells will be at 3.649v + 3.649v + 3.649v + 3.653v = 14.6 and you just tripped the OVP and forced the BMS's FETs to shut off charging. If you use 14.6v as your charge voltage, you will be using the BMS as the charge controller rather than the safety value.

On my DIY build, I charge to 13.8v and let my JK keep everything in balance. On my Basen batteries, which have passive balancing, I charge to 14.2v with 60-minutes of absorption. In both cases I float at 13.3v or lower.

To be fair they only list 14.6 as the “bulk” voltage, and 14.2 as the absorption voltage. By definition the batteries will only actually be at the bulk voltage momentarily. Before that point the charger is putting out all it can but can’t hold 14.6V. Once it hits 14.6 it should drop to absorption until the tail current drops low enough that the batteries are considered full.

 

[Hayden Watson]

To be fair they only list 14.6 as the “bulk” voltage, and 14.2 as the absorption voltage. By definition the batteries will only actually be at the bulk voltage momentarily. Before that point the charger is putting out all it can but can’t hold 14.6V. Once it hits 14.6 it should drop to absorption until the tail current drops low enough that the batteries are considered full.

Not quite true. The charger will keep charging until the voltage gets to 14.6v but the battery can only get to 14.6v IF it is perfectly balanced. In most cases, even a very well-balanced battery will have 10mv - 50mv of delta so before the battery hits its bulk threshold at 14.6v and drops to 14.2v the BMS will be forced to shut off charging. I do not like to do anything on the charging side that will trigger a OVP shut down. It is better to set the bulk and absorption voltage to a level that will not trigger OVP.

 

[Georgedoyle]

I have an ARS-5 set up for AGM batteries hooked up to a Balmar 100 amp 7 series alternator. I need to go into the advanced settings and change the program. I got a cheat sheet from Dale. Now I just need to buck up for the programming with the screwdriver/magnet tool. It’s a real pain to use the reed switch.

 

[Hayden Watson]

Good to hear that you have external regulation. I am not familiar with the ARS-5 so can't help you there. I know that it has the ability to reduce the max output from the alternator which is important. I also believe that you can have it do some depowering based on alternator case temperature. I am not sure what all of the settings mean but 14.5 is higher than I care to charge my LFP. I set my regulator to 14.2v accept and 13.7v float which works for the LFP and my AGM start battery which is isolated from the LFP by an ArgoFET.

My regulator does not have the ability to check alternator case temperature, so I added my own. I used an Inkbird digital thermostat with the thermistor attached to the hottest spot I could find on the case using a Flir. The thermostats relay interrupts the delay start wire that is connected to a relay from the oil pressure switch. When the case temperature gets to 100ºC, it turns off the alternator until it cools down to 95ºC. I also have a 1ohm x 100w resistor in the field wire which reduces the output to about 60A max which keeps the alternator from shutting down due to overheat to only on hotter days or when I am running at lower rpm. I also plan to add a fan to blow cool air from the bilge area directly onto the alternator to supplement cooling. My engine space is small and fully enclosed with 1" sound-dampening foam, so it runs hot.

 

[tkwhalen]

As I noted earlier I replaced my ARS-5 with the Balmar 618 regulator because it include alternator temperature monitoring as well the lithium programing capabilities of my old ARS-5.

 

[Georgedoyle]

Well, I got the new lithiums hooked up. I ended up with a new Victron inverter/charger. It runs silent and is pure sin wave. Worth the upgrade not to hear the whine that my old inverter had. We also added the Cerbo GX and smart shunt. Now everything works together. I programmed the ARS-5 for lithium and used the belt manager to limit the amp draw to about 80 amps. This will save my belt and keep the alternator from overheating. Tk Whalen was right about the little Dakota starting battery. It weighs about 16 pounds, but cranks my engine and generator better than my old group 31 AGM. I especially noticed it on my generator. The old battery always produced a sluggish start. Now it cranks over in about a second. Thank you everyone for your input.

 

[artboas]

Looks like my original Xantrex Freedom 20 won’t work with the lithium batteries. Now I'm having trouble finding a dual input charger/inverter. I need shore power and generator input. It looks like Xantrex doesn't make an updated model that is compatible with lithium batteries.

Firstly, I recommend the Magnum Energy unit very highly. Their customer service is excellent, and the unit is very reliable.
I don’t think that wiring the genset and shore directly into your charger / inverter is a good idea, and I don’t know of any units that have dual feeds,
You need to use a shore/ gen switch
Furthermore, you need to ensure that your water heater and airco units are on a different branch.
I’m going to assume that you possibly have dual 30 amp service, which splits the airco from other house loads. Not sure about the HW tank.
This work isn’t trivial. If you aren’t 100% comfortable with AC branch wiring, you much want to hire someone

 

[Georgedoyle]

We left the generator wiring as original. There is a transfer switch near the breaker panel , so it is not directly wired to the Victron inverter/charger. The Victron unit gets shore power in and sends inverted power out using the original wires. We weren’t sure how it worked until we got elbows deep into the wiring. The water heater circuit is also original, and we don’t have air conditioning.

 

[Georgedoyle]

We have everything set up with our new system and spent yesterday charging the batteries with the generator. We should have charged them at home before the install, but they checked out at high voltage so I assumed they were pretty near full charge. When we checked the state of charge, however, they were only at 25%. Not sure why they would be delivered from the manufacturer in that state. Anyway, we fired up the generator and got to full charge within a couple hours of charging. That was an eye opener. The batteries accepted over 100 amps the entire time so the charge time was really fast. We reached 100% state of charge and continued charging because the individual cells were still in the 3.4 range. We stopped at about 320 AH for each battery, but never reached full charge at the individual cell level. The cells were balanced very well in the 3.5 range across all batteries. I’m not sure if we should keep charging to 3.6. Let me know if you have any thoughts.

 

[dlochner]

When we checked the state of charge, however, they were only at 25%. Not sure why they would be delivered from the manufacturer in that state.

LFP batteries do not want to be stored at 100% SOC. They prefer 25-30%.

 

[Georgedoyle]

That would make sense if it's better for the battery.

 

[Hayden Watson]

We have everything set up with our new system and spent yesterday charging the batteries with the generator. We should have charged them at home before the install, but they checked out at high voltage so I assumed they were pretty near full charge. When we checked the state of charge, however, they were only at 25%. Not sure why they would be delivered from the manufacturer in that state. Anyway, we fired up the generator and got to full charge within a couple hours of charging. That was an eye opener. The batteries accepted over 100 amps the entire time so the charge time was really fast. We reached 100% state of charge and continued charging because the individual cells were still in the 3.4 range. We stopped at about 320 AH for each battery, but never reached full charge at the individual cell level. The cells were balanced very well in the 3.5 range across all batteries. I’m not sure if we should keep charging to 3.6. Let me know if you have any thoughts.

The battery was shipped at between 20% and 50% because that is a regulation for shipping LFP. They will always need to be charge once you get them. They will take as much current as the BMS will allow which in the case of the Epoch 300AH is 200A continuous, each. So you could charge them at 400A and go from 0 to 100% in just over 1.5-hours if you had that much current available.

All of the fun regarding the delta voltage happens between 3.4v and 3.65v so stopping at 3.4v will tell you little about balance.

The first time you charge to full, the BMS will not be calibrated and will give you a false SOC. You need to charge to the 14.4v range to get it to reset and with the cell voltages at 3.4v you cannot tell much about the cell balance.

If they were my new batteries, I would set the absorb voltage to 13.8v and watching the delta. Then move up in 0.2v steps until you get to 14.4v. If the delta is in the range of 50mv then I would drop my charge voltage down to what I think is the best range for absorption and float.

 

[Hayden Watson]

LFP batteries do not want to be stored at 100% SOC. They prefer 25-30%.

This is correct. When I have by batteries in storage mode (more than a few weeks between usage) I lower the float voltage to 13.2v. This lets them drop down to 50%-70% SOC. When I am heading out for a cruise, I change to my full charge settings, and it gets topped back up while I am in the process of loading a preparing for departure. If I am going out for a day sail. I don't worry about topping it up.

 

[Georgedoyle]

Good information. Thanks. The Bluetooth app on my Epochs showed 100%, but, just to be certain, you're saying that is a false reading. I think my final charge voltage was 13.8. It never reached 14 volts. I guess I'll charge beyond 100% until my individual cell charges go higher. Should I shoot for 3.65 or is that too much?

 

[Hayden Watson]

Good information. Thanks. The Bluetooth app on my Epochs showed 100%, but, just to be certain, you're saying that is a false reading. I think my final charge voltage was 13.8. It never reached 14 volts. I guess I'll charge beyond 100% until my individual cell charges go higher. Should I shoot for 3.65 or is that too much?

3.65v is too much because it would force the BMS to disconnect and I try to never let it. I prefer to sneak up on the max charge at 0.1v steps on the charger while watching the app. If I see any cell getting above 3.60v I stop charging. The delta at that point is your unbalance. The max that I ever charge to for any reason is 14.4v which is 3.60v/cell if the battery is perfectly balanced.
When I first got my 460Ah batteries, one of them was so badly out of balance that I could not get to 14.0v without sending one cell over 3.65.
I look at the BMS as a safety valve which should not normally be needed and is there only to prevent a complete mess if the defecation hits the rotary oscillator.
You would not set the water temperature on your water heater so high that it caused the water to get almost to boiling which would trip the over temperature safety valve that they all have. It would defiantly cool down the water because as it blows out scalding water, cold water is coming in to replace it. If you Charge to 14.6v, like Battle Born recommend, that is exactly what you are doing with the LFP.

 

[Johann]

This is a good article on charging LFP. Charging Marine Lithium Battery Banks | Nordkyn Design
The site has a lot of good information. In this article there is a chart which you can use to derive what 100% SOC is based on voltage and current. Epoch uses Eve cells, which specify 100% as 3.65Vpc with a 0.05C tail current. So at 3.45Vpc (13.8V) you would be full once the accepted current drops to 0.014C. At 3.55Vpc (14.2V) it is 0.032C.

 

[Hayden Watson]

This is a good article on charging LFP. Charging Marine Lithium Battery Banks | Nordkyn Design
The site has a lot of good information. In this article there is a chart which you can use to derive what 100% SOC is based on voltage and current. Epoch uses Eve cells, which specify 100% as 3.65Vpc with a 0.05C tail current. So at 3.45Vpc (13.8V) you would be full once the accepted current drops to 0.014C. At 3.55Vpc (14.2V) it is 0.032C.

This is an excellent article and when I go for a full charge, I use the tail current function on my shore chargers. My EVE 280K cells are specified at 0.05C cutoff so given that I charge to 13.8v [3.45v/cell] I use an 8A tail current for my 560Ah battery.
When I am on shore charger for a long time, I drop absorb and float to 13.2v and let the battery sit down in the 50% - 70% range when I am connected to shore power.

 

[Georgedoyle]

Now that we have been running on our lithium batteries for a while, a new concern has come up. While the generator is running and supplying power to the new battery charger to charge the house bank, the small alternator on the generator is charging the start battery. Since this battery is also lithium, I am worried about damaging the alternator. I have a Balmar regulator on my main engine alternator so I have set the belt manager feature to keep that alternator from burning up. What should I do about the other alternator? It is charging a Dakota 65 ah 1000 cca lithium starting battery. Last I checked, it was putting in about 40 amps.

 

[marcham]

I don't think this is an issue. Your start battery has a very very low depth of discharge after having started the generator. It's probably fully recharged in 5 minutes.

 

[Stu Jackson]

What should I do about the other alternator? It is charging a Dakota 65 ah 1000 cca lithium starting battery. Last I checked, it was putting in about 40 amps.

How big is this alternator? Other than that, marcham is right, and if it is that close to full already you'll be hitting the charging knee right away,, wouldn't you?