Lithium Battery Charging Question(s)

[PaulCrawhorn]

Originally Posted by Melbourne Park

I think you guys may be wrong about Lithium being extended by avoiding using the top end of the capacity of the battery

No, sorry, but this is proven and 100% accepted consensus.

Now there are also many other factors with much greater impact on cycle lifespan.

For example as stated, high temperatures, both ambient and - especially - anything generated internally from high C-rates.

Also SITTING at high SoC% is 1000x worse than going near max spec voltage but then a load immediately pulling SoC back down, that would be a very low impact factor.

Finally keep aware many owners are hapot to get the paltry 3-4000 cycle lifespans from "normal abuse", not even interested in getting to decades, 10,000 and higher.

[Jerry Woodward]

I've done a lot of reading on CF, Marine How To, Nordykin, etc. in preparation for my eventual Lithium transition and I'm still confused.

Some points of confusion that maybe someone can help me understand:

1. Most everyone states that LiFePO4 batteries maintain a very constant voltage over a wide range of SOC, only increasing at the very last before "full". Yet, in this thread, many people seem to be using voltage cut-off to stop charging at a particular state of charge. How does this work?

2. Related to point 1. On a nice sunny day at anchor: Once the battery is full or maybe 90% SOC, (13.8 volts?) and you have your solar controller set to stop charging at that voltage, with no load, the solar controller shuts off. Now your refrigerator cycles on, drawing 4 amps in my case. Does the voltage drop enough for the solar controller to turn on and supply the 4 amps? Or, does the 4 amps come out of the battery for a period of time before the voltage drops enough to turn on the controller?

3. Regardless, it seems that in scenario 2 that the LiFePO4 bank is going to be microcycling all day long every time the refrigerator cycles (and all night long if you have a wind generator). Is this good for the battery?

4. Or, is it better to turn off all charging and let the battery disharge for a day, say to 25% DOD (100 AH for a 400 AH bank)? In other words, one charge cycle of 100 AH in a 24H period vs maybe 50 cycles of 2 AH.

[goboatingnow]

Originally Posted by Jerry Woodward

I've done a lot of reading on CF, Marine How To, Nordykin, etc. in preparation for my eventual Lithium transition and I'm still confused.

Some points of confusion that maybe someone can help me understand:

1. Most everyone states that LiFePO4 batteries maintain a very constant voltage over a wide range of SOC, only increasing at the very last before "full". Yet, in this thread, many people seem to be using voltage cut-off to stop charging at a particular state of charge. How does this work?

The voltage at both ends of the charge graph does change more rapidly so it can be used to indicate low SOC or high SOC. it’s the bit in the middle where the voltage is not a good indicator of SOC

2. Related to point 1. On a nice sunny day at anchor: Once the battery is full or maybe 90% SOC, (13.8 volts?) and you have your solar controller set to stop charging at that voltage, with no load, the solar controller shuts off. Now your refrigerator cycles on, drawing 4 amps in my case. Does the voltage drop enough for the solar controller to turn on and supply the 4 amps? Or, does the 4 amps come out of the battery for a period of time before the voltage drops enough to turn on the controller?

This is a function of the settings of your solar controller. Most will assume the load current if they can others have a “ re-bulk “
Settings ( a voltage ) where they will restart supplying power

3. Regardless, it seems that in scenario 2 that the LiFePO4 bank is going to be microcycling all day long every time the refrigerator cycles (and all night long if you have a wind generator). Is this good for the battery?

4. Or, is it better to turn off all charging and let the battery disharge for a day, say to 25% DOD (100 AH for a 400 AH bank)? In other words, one charge cycle of 100 AH in a 24H period vs maybe 50 cycles of 2 AH.

There is some scholarly debate and research papers on the effect of micro cycling on Li tech

What we do know is extended periods at 100% and large DoD ( depth of discharge )are not good for long life. However even when treated poorly the cycle life capability of LFP is still fantastic compared to LA

Hence I would focus on low DoD and recharge whenever possible as most charging on a boat is opportunity based.

[SOLAR SUPPORT]

Quote:
"Does the voltage drop enough for the solar controller to turn on and supply the 4 amps? Or, does the 4 amps come out of the battery for a period of time before the voltage drops enough to turn on the controller?"

Lifepo4 will turn itself off after the battery is full. The solar charge controller operating in the fixed system voltage sensing mode directly meets the electrical energy need on the boat without the battery being activated, as long as it supplies the energy source at a sufficient level to the extent of its capacity. If the energy need in the boat is high, the missing energy is met with the activation of the lifepo4 battery.

It is important that the charging voltage of the solar or wind charge controller to be used to charge the Lifepo4 batteries can be easily adjusted by the user. It is possible to adjust the charging regime of Lifepo4 batteries by changing the charging voltage setting.

To count the advantages of changing the charge voltage:
- Keeping Lifepo4 batteries at 50-60% SOC for a long time when not subjected to any load
-To keep the %SOC of the batteries at the desired level when a continuously working freezer or similar device is on.
-Adjustment of the charge controller to the required voltage level to produce maximum energy again.
-Measuring the possible voltage drop in the cable going from the charge regulator to the batteries and adjusting the charge voltage to reach the highest efficiency.

It is also important that the charge voltage detection setting can be adjusted steadily. When the Lifepo4 turns itself off after the batteries are full, the solar charge controller loses charge voltage control for a very short time. Meanwhile, if the charging voltage detection setting is made automatically, the system may experience chaos for a short time and the system may be exposed to the wrong voltage.

During this chaos in a very short time, your sensitive electronic devices may be damaged. Charge controller must be able to operate at a constant charge voltage sensing setting of 12 or 24 volts as well as automatically detecting the charge voltage.

[goboatingnow]

Originally Posted by SOLAR SUPPORT

Quote:
"Does the voltage drop enough for the solar controller to turn on and supply the 4 amps? Or, does the 4 amps come out of the battery for a period of time before the voltage drops enough to turn on the controller?"

Lifepo4 will turn itself off after the battery is full. The solar charge controller operating in the fixed system voltage sensing mode directly meets the electrical energy need on the boat without the battery being activated, as long as it supplies the energy source at a sufficient level to the extent of its capacity. If the energy need in the boat is high, the missing energy is met with the activation of the lifepo4 battery.

It is important that the charging voltage of the solar or wind charge controller to be used to charge the Lifepo4 batteries can be easily adjusted by the user. It is possible to adjust the charging regime of Lifepo4 batteries by changing the charging voltage setting.

To count the advantages of changing the charge voltage:
- Keeping Lifepo4 batteries at 50-60% SOC for a long time when not subjected to any load
-To keep the %SOC of the batteries at the desired level when a continuously working freezer or similar device is on.
-Adjustment of the charge controller to the required voltage level to produce maximum energy again.
-Measuring the possible voltage drop in the cable going from the charge regulator to the batteries and adjusting the charge voltage to reach the highest efficiency.

It is also important that the charge voltage detection setting can be adjusted steadily. When the Lifepo4 turns itself off after the batteries are full, the solar charge controller loses charge voltage control for a very short time. Meanwhile, if the charging voltage detection setting is made automatically, the system may experience chaos for a short time and the system may be exposed to the wrong voltage.

During this chaos in a very short time, your sensitive electronic devices may be damaged. Charge controller must be able to operate at a constant charge voltage sensing setting of 12 or 24 volts as well as automatically detecting the charge voltage.

A good mppt controller like the Victron stores the battery voltage after first detection. It does not re-sense it again unless you do a restart. You can also override the voltage sensing completely

You can also set all the voltages but the situation is that the LFP will almost always power the load as the solar controller will be set to be slightly below the charge stop point

[SOLAR SUPPORT]

Originally Posted by goboatingnow

You can also set all the voltages but the situation is that the LFP will almost always power the load as the solar controller will be set to be slightly below the charge stop point

Setting a charge voltage below the HVCutoff voltage of the lifepo4 battery will fix the problem, but since some drop in lifepo4 batteries have an HVCutoff voltage close to 14.0 volts. You need to set the charge regulator voltage setting below this value. This setting may reduce mppt charge controller performance. In a charge regulator with a fixed voltage detection setting, you can use the charge voltage setting which is above the HVCutoff limit of the battery. Charge regulator would give the higher charging performance.

Even if the HVCutoff event is triggered, the charge regulator continues to feed the system uninterruptedly with the fixed voltage value set.

[goboatingnow]

Originally Posted by SOLAR SUPPORT

Setting a charge voltage below the HVCutoff voltage of the lifepo4 battery will fix the problem, but since some drop in lifepo4 batteries have an HVCutoff voltage close to 14.0 volts. You need to set the charge regulator voltage setting below this value. This setting may reduce mppt charge controller performance. In a charge regulator with a fixed voltage detection setting, you can use the charge voltage setting which is above the HVCutoff limit of the battery. Charge regulator would give the higher charging performance.



Even if the HVCutoff event is triggered, the charge regulator continues to feed the system uninterruptedly with the fixed voltage value set.

No Li system should trigger HVCutoff on a regular basis. The charge stop voltages/tail current algorithm should always stop charging below the HVC point in my opinion. Preferably all charge stop and resume commands should be centrally determined by the BMS and not the individual charge sources.

[SOLAR SUPPORT]

Originally Posted by goboatingnow

No Li system should trigger HVCutoff on a regular basis. The charge stop voltages/tail current algorithm should always stop charging below the HVC point in my opinion. Preferably all charge stop and resume commands should be centrally determined by the BMS and not the individual charge sources.

All the materials needed for the LA-Lifepo4 battery upgrade that I applied on my own boat are of cheap Chinese origin and there is no central charge control system on the boat.

All chargers work independently of each other. Drop in Lifepo4 batteries, charge voltage adjustable mppt charge controller, Columb meter and voltage sensitive relay, timer relay and the system that I have installed on my boat with the mechanism that turns the excitation current of the alternator on and off works very well.

The information I have explained here is based on measurements and observations I have made on a very modest and simple Lifepo4 battery and solar charger that I have built on my own boat.

DC-dc charger, externally regulated new alternator, battery-alternator protector, Bluetooth smart solar charge controller, shore charger with Lifepo4 setting, central system smart bms, Bluetooth-enabled smart lifepo4 batteries have a total cost close to the quarter of my 35 feet sail boat's value. That is why I didn't use them.

[Melbourne Park]

[QUOTE=Jerry Woodward;3655611]I've done a lot of reading on CF, Marine How To, Nordykin, etc. in preparation for my eventual Lithium transition and I'm still confused.

Some points of confusion that maybe someone can help me understand:

2. Related to point 1. On a nice sunny day at anchor: Once the battery is full or maybe 90% SOC, (13.8 volts?) and you have your solar controller set to stop charging at that voltage, with no load, the solar controller shuts off. Now your refrigerator cycles on, drawing 4 amps in my case. Does the voltage drop enough for the solar controller to turn on and supply the 4 amps? Or, does the 4 amps come out of the battery for a period of time before the voltage drops enough to turn on the controller?

The voltage or charge - IMO - should not change because when power is drawn, the solar controller will turn on. So the charge state of the batteries will simply be maintained.

If the solar power is less than the new power draw - then the batteries will not be charged, because the solar power is less than is being drawn.

When the compressor for the fridge turns off - and the battery has been depleted - then the solar would continue on and charge to batteries.

In that scenario, I do not see much much switching going on.

[Melbourne Park]

Originally Posted by SOLAR SUPPORT

... the system that I have installed on my boat with the mechanism that turns the excitation current of the alternator on and off works very well.

I am interested in what you did!

[SOLAR SUPPORT]

Originally Posted by Melbourne Park

I am interested in what you did!

https://www.cruisersforum.com/forums...ml#post3568254

The link above explains how the alternator work is done. Since then some additional information and a brief update are required.

After the voltage sensitive relay, a time delay relay was required to break the frequent on-off cycle of the VSR. Those are small relays with 20a-30a capacity to control the alternator charge by turning on and off the rotor excitement current. They work in harmony and serve to protect all the electronics working at the same time on the whole system during alternator charge. I also have a manual on-off switch to cancel my alternator.

In addition, the NC thermostat mounted on to the alternator should be 90 °C scale. I can provide more detailed information if anybody interested.

[PaulCrawhorn]

The ideal situation for optimal longevity is one thing, and requires sophisticated design and equipment. Maybe achieving 6000+ cycles even 10K is IMO possible.

If just making do with reasonably priced gear, there will be compromises. But if the bank "only" lasts 3-4000 that is more than enough for most owners.

Don't let perfection become enemy of the good.

[goboatingnow]

The issue of whether the mppt controller or the Li back meets the load is largely irelevant and is effectively a function of the relative output resistance of each power source. So in real life the actual division between the solar controller and the battery may be hard to define. In end it doesn’t matter , if the battery trigger a charge cycle restart power will flow into the battery

[Melbourne Park]

Originally Posted by SOLAR SUPPORT

https://www.cruisersforum.com/forums...ml#post3568254

The link above explains how the alternator work is done. Since then some additional information and a brief update are required.

After the voltage sensitive relay, a time delay relay was required to break the frequent on-off cycle of the VSR. Those are small relays with 20a-30a capacity to control the alternator charge by turning on and off the rotor excitement current. They work in harmony and serve to protect all the electronics working at the same time on the whole system during alternator charge. I also have a manual on-off switch to cancel my alternator.

In addition, the NC thermostat mounted on to the alternator should be 90 °C scale. I can provide more detailed information if anybody interested.

Thanks, I'll read that thread.

My boat has a small motor, a Yanmar twin cylinder, with a stock 125 Amp rated alternator, the motor typically has 80 amp alternators, and the boat is setup for AGMs. From reading, I think the alternator is very average, and someone who seems to have it, have posted that its capacity is at best 90 amps, and under load it throttles back to often 60 or 50 amps.

My issue is the auto pilot, which draws 8 amps, along with the electronics and the compressor factory fridge. I have arrived at 8 amps because a friend has a larger version of my boat, and he has done several short handed races (including the Melbourne - Osaka) , and his undergraduate degree is electronic engineering. Since his boat uses 8 amps, mine would be the same - 8.5 amps at worst. I do not know for sure, because my instruments do not reveal amps being used. I've not gone out with a ring meter either, to try and it all out.

Singled or two handed sailing, that autopilot etc. draws lots of power in a day. So even if I have lithium, whatever capacity I have, it will soon be used up - in a day, or the second day, and even with Lithium, if I bought lots of capacity, by the third day.

With a bank of 4 AGM type batteries, they would charge just as quickly as the lithium, due to the lack of charge ampage available, and due to a parallel bank distributing the total charge of the ampage available, during their initial bulk charging stage. However, from my reading of many AGM batteries' charging characteristics, after the bulk stage reaches 75%, their charging resistance increases enormously, the time versus volts curve starts to flattens out at 76% Which thereby would result in beyond a 75% AGM charge, one would run the motor for many hours, with hardly any charging being gained.

So, I have rated the on water capacity of an AGM at being only 75% of it's claimed capacity (and those are often exaggerated). If I buy AGMs, I would buy carbon lead, as they seem to handle partial charge better than straight AGM. However most carbon lead batteries are designed for solar house / factory / farm etc power storage. The best are 6 volts, and even need to be used vertically. There are some extraordinary claims for carbon lead, but IMO those are based on such large scale 6 volt batteries.

There are few normal sized carbon lead batteries available, and some are costly and seem no better in performance than a LifeLine AGM battery. But LifeLines are very expensive in Australia - they cost much less in the USA. And interestingly, LifeLine have not made a carbon lead battery. Instead, they seem have decided that the cost of engineering carbon lead was from a business point not worth it, instead, they've invested their new plan t into lithium (presuming they make their new Lithium batteries themselves).

So - even if I got 4 OK carbon lead AGM batteries, at 32.5 kg each, I would be putting in 110 kg of batteries. I do have the cabling already in place for 4 house batteries though. But 4 AGMs in my boat, is quite a lot of space and weight. Fairly OK quality AGMs such as Full River, or a Victron 105 AH carbon lead, weigh 36kg each. So that is another 10 kg. And such batteries take up lots of space. The cost of a carbon lead of a claimed 120 AH if I buy 4, would be Aus $ 400 each. Full River standard AGMs would cost $450 each. A 150 AH OK quality lithium would cost about $Aus 1,000 each. I want two batteries in case one fails. It is possible to buy pretty good lithium batteries in Australia 280 AH capacity, for Aus $1,800, with a 20 amp charger thrown in. But when one has two, there is quite a difference in cost between $3600 for Lithium, and $1,600 Aus dollars. Plus, there is the charging issue via I presume DC-DC, which adds more cost.

Also, I will need some solar, so if the DC-DC handles solar (ie incorporates an MPPT capability), then the extra cost of DC-DC reduces.

So, lithium offers more space and I can use most of their capacity if at sea, and I save weight.

But ... there is the cost issue. So I am trying to work out the cheapest way to get a good solution.

I therefore - as mentioned previously - I have to add some solar, which on my boat is not easy, but it is possible, and I've yet to work out how much I can install, there are places down aft which others have utilised.

For solo or two handing racing - such as the Melbourne to Osaka, etc etc., boats like mine are equipped with hydro generators, and they pop the impeller into the water and get lots of power. From 5 to 25 amps is easy to achieve. So an auto-pilot is unnecessary in a dead calm, so really, such a device makes lots of sense. But they cost $6,500 Australian dollars, or around $US4,000 . So for my use, I would only use one on a long voyage, and I am not planning one. So some solar would lower the daytime 8 amps workload down quite a lot.

Lithium though adds complications - as mentioned - but the real issue is the alternator. So I'll look at your or "the" thread with interest.

I am not getting anything for 3 weeks as I am going away, but I'll do something in 3 weeks or so. It's time for my final research. I've also been bemused by the lack of tech details on different lithium batteries. With AGMs, makers often show pictures of their products, and list their technological differences. Not so with Lithium - they never show a picture of the way the cells are attached, the BMS is rarely listed, the kind of electrical connection between the batteries is not mentioned (or rarely), the best one gets is a capability of the BMS and the capabilities of the Cells. It's even difficult to find out if the cells are prismatic, and if so, whether their cases are metal or plastic.

So the Lithium decision requires a lot of work. Which is a tactic of makers IMO - they want buyers to give up and trust, and if one is doubtful, then one tends to spend more money, in the expectation that more money will give you a better product.

[goboatingnow]

If you don’t go Lithium , stay away from AGMs also especially if your usage patterns result in frequent partial charging