Is it possible?

[SOLAR SUPPORT]

Making use of pure sine inverters can solve many problems in this field in terms of using alternators safely for LFP battery charging. By converting the DC power produced by the alternator to AC power with PSI, you can charge the 12-24-48 volt LFP battery bank by using an advanced hybrid inverter or a rectifier used only for charging. Considering that AC-DC chargers are generally available on all boats, I find it important for the widespread use of this system.

[SOLAR SUPPORT]

The use of pure sine inverters can solve many problems in this area in terms of safe use of alternators for LFP battery charging. By converting the DC power produced by the alternator to AC power with PSI, you can charge the 12-24-48 volt LFP battery bank using an advanced hybrid inverter or an AC-DC battery charger used only to charge the batteries. Both of these charging sources must have a battery charge current level that does not exceed the PSI's and Alternator's safe continous operating range limit. Considering that AC-DC battery chargers are generally found on all boats, this plan turns out to be more feasible.

[Joli]

Wouldn't the simplest system be a mixed chemistry bank charged by a standard alternator? IE half fla and half lifepo4. Not ABYC approved but simple and cheap.

[goboatingnow]

Originally Posted by Joli

Wouldn't the simplest system be a mixed chemistry bank charged by a standard alternator? IE half fla and half lifepo4. Not ABYC approved but simple and cheap.

And of course has potentially dangerous failure modes.

[Joli]

Originally Posted by goboatingnow

And of course has potentially dangerous failure modes.

I don't know, what would the failure be? It seems the lifepo4 would feed the fla's until the bms cuts them out? Then the draw would be on the fla's. Charging would be to the lifepo4 then the fla's.

[stevelex]

If I understand the question google Victron Orion. I have one running of an alternator in a camper.

[SOLAR SUPPORT]

Originally Posted by Joli

I don't know, what would the failure be? It seems the lifepo4 would feed the fla's until the bms cuts them out? Then the draw would be on the fla's. Charging would be to the lifepo4 then the fla's.

#1 Due to their chemical nature, LA batteries like to stay fully charged all the time. The situation is different for Li batteries. Being fully charged during long standby times shortens the life of Li batteries.

#2 When you connect these batteries that reach full charge at different voltage levels, you cannot charge the LA batteries to full charge. Therefore, the "absorption" charge required by LA batteries is missing. Since this stage is skipped, sulfate accumulation in LA battery plates increases, their performance decreases, and their lifespan, which is shorter than Li batteries, becomes much shorter.

#3-When you connect these batteries, which have different chemistry, there is a continuous energy transfer from LFP batteries to LA batteries, since the internal consumption of LA batteries is higher than Li batteries.

#4 It is very common for LA batteries to have a short circuit from the inside of the lead plates, which wear out much quicker than Li batteries. Considering this possibility, it is quite risky to use LA and Li batteries together.

[Joli]

Originally Posted by SOLAR SUPPORT

#1 Due to their chemical nature, LA batteries like to stay fully charged all the time. The situation is different for Li batteries. Being fully charged during long standby times shortens the life of Li batteries.

Wouldn't lifepo4 just sink to the fla until the bms cuts it off or the voltage are the same?

#2 When you connect these batteries that reach full charge at different voltage levels, you cannot charge the LA batteries to full charge. Therefore, the "absorption" charge required by LA batteries is missing. Since this stage is skipped, sulfate accumulation in LA battery plates increases, their performance decreases, and their lifespan, which is shorter than Li batteries, becomes much shorter.

Can't you just charge both to 14.4 volts and call it good?

#3-When you connect these batteries, which have different chemistry, there is a continuous energy transfer from LFP batteries to LA batteries, since the internal consumption of LA batteries is higher than Li batteries.

That's a bad thing?

#4 It is very common for LA batteries to have a short circuit from the inside of the lead plates, which wear out much quicker than Li batteries. Considering this possibility, it is quite risky to use LA and Li batteries together.

Our's haven't shorted internally after 40 years, why would they do that now?

It seems like mixed chemistry parallel battery banks remove the risk to alternators and eliminates the need for a DC DC converter to protect the alternator?

[SOLAR SUPPORT]

Perhaps you can cancel the set maximum charge voltage limit under the HVCutoff protection voltage of Lifepo4 batteries, which applies to all charging sources onboard, and continue charging to reach 14.4 V. when you mix LA and Li batteries.

We try to maintain the balance between the batteries by choosing the cable lengths used for parallel connection of Li batteries equally. Do you think the balance will not be disturbed when you connect a LA battery between them? Besides, you might think that you can solve the high voltage problem in the alternator by mixing the batteries, but; the overheating problem of your fabricated alternator will continue.

[goboatingnow]

Originally Posted by Joli

Our's haven't shorted internally after 40 years, why would they do that now?



It seems like mixed chemistry parallel battery banks remove the risk to alternators and eliminates the need for a DC DC converter to protect the alternator?

The risk to the alternator is entirely over stated anyway

[SOLAR SUPPORT]

Watch the video showing how to make a car alternator a pure sine inverter.

https://youtu.be/fz2-e9pxIFc

A small gasoline engine used to power a 120 A alternator in the video. It doesn't work properly like well designed commercially available inverter generator sold in the market because the motor is underpowered to produce the required electrical power.

When you connect the alternator output on the boat to a pure sine inverter of suitable power as in the plan, you will have an inverter generator on the boat that works just fine. You can use the pure sine AC power obtained from here in your existing battery charger onboard or in the AC mains power input of the hybrid inverter to charge your LFP batteries.

[T1 Terry]

Umm.... that is just an inverter running off a 12v battery being recharged by a 12v alternator. There is nothing making the alternator output pure sine wave, the alternator is connected to the battery and the inverter is turning the 12v battery DC into 120vac .... nothing there shows it to be pure sine wave either, that is a brush type electric motor on the grinder and it will run on DC and AC and anything in between including square wave and modified sine wave.

T1 Terry

[SOLAR SUPPORT]

Originally Posted by T1 Terry

Umm.... that is just an inverter running off a 12v battery being recharged by a 12v alternator. There is nothing making the alternator output pure sine wave, the alternator is connected to the battery and the inverter is turning the 12v battery DC into 120vac .... nothing there shows it to be pure sine wave either, that is a brush type electric motor on the grinder and it will run on DC and AC and anything in between including square wave and modified sine wave.

T1 Terry

In the picture below the previous post, the structure of the inverter generator is shown schematically. This schema fits perfectly with what I have described.

https://www.mortonsonthemove.com/wha...ter-generator/

Detailed information is available at the link above. The setup in the video is actually in line with the plan I sent and leaves no room for doubt. I think I need to find a full sine inverter and try it out on my boat. Everyone is ready, waiting for the job to be put in front of him..

[T1 Terry]

I'm guessing you don't really understand how an alternator works. The rectifier shown as the next step after the alternator is mounted inside the alternator. That is how these things work, the alternator generates 3 phase AC fed into a bridge rectifier that converts half the wave through one diode and as the wave form drops below 0V that diode acts as a blocking valve and the other diode paired to the AC phase passes through that diode. Because it is 3 phase there is virtually no ripple on the DC output. This now DC current charges the start battery.
In your first post you show a diagram of the alternator and start battery feeding into the inverter, then that inverter feeding into a battery charger ...... all you are creating with this alternator/start battery to inverter to charger is a very inefficient DC to DC charger.
If you plan to use Victron gear, an Orion Smart DC to DC will do what you want far more efficiently and can be programmed via asmart phone to do exactly what you want. The output is limited to 30 amps, this means even if you set it up for low start battery voltage cut off, the max you will draw from the start battery is 40 amps, 10.5v x 40 amps = 420w, the same as the the DC to DC output at the end of lithium bulk charging voltage of 14v. 14v x 30 amps = 420w. The Orion Smart DC to DC even knows to lower the charging rate when the start battery voltage is low enough to cause the required input to exceed 420w due to losses within the DC to DC charger itself. This is actually a self preservation thing on the Orion's behalf, it is to stop overloading the circuitry and creating excessive heat.

These things are really smart, the start battery to inverter to battery charger isn't near as smart and will waste a lot of the energy generated by the alternator because of the number of changes of voltage and conversions from DC to AC, then from AC back to DC.

There is no value in trying to reinvent this process, I've been there and done that 11 yrs ago and learnt the hard way that it just doesn't work over the longer term.

T1 Terry

[SOLAR SUPPORT]

The transition from LA battery to LFP battery requires new chargers, batteries, alternator adjustment-change works and new installation works that fill your budget. I was not surprised when I saw the facebook post of a boat owner who received a price of 25,000 USD for the smart system required for the operation of Li batteries with a capacity of 600 Ah.

I don't think that small and medium boat owners would want to allocate such a budget for the LA-LFP transition. They also want to take advantage of the new LFP battery technology and are researching to do so by finding solutions that fit their budget. Safe LFP technology batteries have come to affordable prices, and everyone wants to use this technology with moderate additional expenses. My goal is to help people like me who are sailors and trying to keep it going.

Consider a scenario that is usually rare during the summer months when solar power is not enough after two or three cloudy days. Coastal electricity is not available. It is possible to use the AC battery charger by running the existing generator on board to charge your batteries. If you don't have a generator, the second option to charge your batteries is to start the boat engine.

With the energy produced by a powerful engine and the alternator connected to it, you want to fill the batteries as soon as possible or charge them to a healthy level and get rid of the engine noise and exhaust fumes that disturb everyone. You can use an advanced smart DC-DC charger to do this job. The power of this device can be at most half the tag power of the alternator. To purchase such a device, which is connected to the engine battery without replacing the factory alternator, you have to pay three times the price of a pure sine inverter device of the same power.

There are other advantages to using a pure sine inverter as an alternative to a DC-DC charger. With the AC energy produced by this device, you can charge your batteries using the AC battery charger available on board. If your solar energy and/or AC charger is not compatible with your new LFP batteries, it is possible to charge a hybrid device that you can buy at very reasonable prices with an alternator-inverter. It should be noted here that the AC energy power produced using the alternator should not exceed half of the alternator label power.

For example, the maximum power of a 100A alternator is 100 X 14 = 1.400 watts. In order to prevent the alternator from overheating, you can get half of this power, 700 Watt, from the alternator. This power is lost 10% when converted to AC power in a pure sine inverter. You can transfer 630 watts of power to your charger. While the charger converts this energy to DC, energy losses will be around 10%. The highest charging power you can transfer to the batteries is reduced to 567 watts in this way, so you can charge the batteries with a maximum current of 567W/14V=40Amp. Below this current level is safe, and above it is risky as it will cause the alternator to heat up.

In order to prevent the inverter to be connected to the alternator from heating up, it will be beneficial to be mounted outside the engine compartment and be easily accessible. It is possible for pure sine inverter power to be below 80% of alternator tag power. The higher the inverter's capacity, the less it will heat up when running. As explained above, the capacity of the AC charger used to charge the batteries should be below 40% of the maximum charging capacity written on the alternator label.

There is another issue that needs attention in the alternator + pure sine inverter solution. When the engine is stopped, the inverter must be turned off, as the inverter will continue to draw small amount of energy from the engine battery. Since there will always be the possibility of forgetting this, it would be beneficial to use an automatic mechanism that activates the inverter at the same time when the motor switch is opened, and turns it off when the motor switch is closed.

I am going to try the 115A Mitsubishi Alternator + 1000Watt pure sine inverter setup soon in my boat to charge my 400Ah LFP batteries through the existing 25A AC battery charger.