LFP+BMS+Ultracapacitors? or (2)(LFP+BMS)?

[wholybee]

Originally Posted by SOLAR SUPPORT

I think the importance of a simple and safe installation consisting of a LFP house and LA engine battery is not emphasized enough. When Service LFP and Engine LA batteries are connected to the alternator using a battery isolator, you have continuous alternator protection against HVC phenomenon. Additionally, energy transfer between LFP and LA batteries is isolated. Two birds with one stone. Put a current limiting dcdc charger device on the battery isolator output and charge the LFP house battery without taxing the alternator. Just add a simple Coloumb Meter to monitor LFP battery charge level and that's it.

You are mixing two workable approaches. If you intend to use a DCDC to limit current, there is zero reason for an isolator. Just connect the alternator to the LA battery, and use the DCDC to charge the LFP.

If you want to use the full charging capacity of the alternator with a good external regulator, use the isolator and skip the DCDC.

There isn't any reason to use both.

[s/v Jedi]

Originally Posted by SOLAR SUPPORT

I think the importance of a simple and safe installation consisting of a LFP house and LA engine battery is not emphasized enough. When Service LFP and Engine LA batteries are connected to the alternator using a battery isolator, you have continuous alternator protection against HVC phenomenon. Additionally, energy transfer between LFP and LA batteries is isolated. Two birds with one stone. Put a current limiting dcdc charger device on the battery isolator output and charge the LFP house battery without taxing the alternator. Just add a simple Coloumb Meter to monitor LFP battery charge level and that's it.

Originally Posted by wholybee

You are mixing two workable approaches. If you intend to use a DCDC to limit current, there is zero reason for an isolator. Just connect the alternator to the LA battery, and use the DCDC to charge the LFP.

If you want to use the full charging capacity of the alternator with a good external regulator, use the isolator and skip the DCDC.

There isn't any reason to use both.

This is interesting. The battery isolator is the choice for those who believe the drop-in battery tale and don’t mind using 14.6V absorption voltage for their LFP batteries. They state that the BMS will fix it when needed and during HVC the start battery, via the isolator, will prevent the transient surge. And while I don’t agree with charging drop-in batteries with 14.6V, I do agree that this method works just fine. The advantage is that you get a lot of charge current into your LFP battery with just a couple diodes or FET’s instead of smart DC-DC chargers.

Then there’s the camp who wants to use the correct charge algorithms for each chemistry. This is a good start. Here you have options. First one is to keep the engine and start battery the way the engine manufacturer designed it. If budget allows, you upgrade the LA battery to a nice AGM designed for starting engines. Now you connect a smart dc-dc charger between start battery and LFP battery and program it to detect the active alternator and start charging the LFP at that time.
This is a great option, I have this, and it keeps things simple while doing everything right. I actually have two DC-DC chargers in parallel so that I can take 12V 60A from my alternator and charge my lithium at 24V 30A. See that, I also change the voltage, something that doesn’t work with the isolator but is just a matter of ordering the right DC-DC charger otherwise.

But the last group of people have another option: they can change their setup so that the alternator charges the LFP battery directly. For this they use a high power alternator with external regulator. The start battery gets charged by a small DC-DC charger which is enough to recharge what is lost with starting the engine. Now this group gets to deal with a possible HVC. They must assume that when one battery does HVC, all the others will follow very quick and you need an automated system to prevent this.

One option is more expensive batteries with Victron compatible CANbus. Add a Cerbo GX and get a more expensive regulator that also does this CANbus protocol and it will stop the alternator and prevent HVC.

Then there is a subgroup who can’t afford the pricy stuff but still for some reason, probably money related, still want to charge LFP straight from the alternator. For this group I gave the option of doing some tricks with a relay and battery monitor. Not as solid as the other options but that’s what you get when corners are cut

[wholybee]

Originally Posted by s/v Jedi

This is interesting. The battery isolator is the choice for those who believe the drop-in battery tale and don’t mind using 14.6V absorption voltage for their LFP batteries. They state that the BMS will fix it when needed and during HVC the start battery, via the isolator, will prevent the transient surge. And while I don’t agree with charging drop-in batteries with 14.6V, I do agree that this method works just fine. The advantage is that you get a lot of charge current into your LFP battery with just a couple diodes or FET’s instead of smart DC-DC chargers.

My reasoning is the opposite of that. You set your external alternator to charge parameters appropriate for LFP, and the Lead Acid doesn't care. If you charge your LFP to ~14V give or take, that's just fine for charging Lead Acid. And when it drops to a float voltage of anywhere between 13V-13.4V that is fine for both as well. Maybe you don't charge the Lead Acid as quickly, but starting uses so little energy it doesn't matter.

Edit: and no need for anything else to protect from and HV event.

[s/v Jedi]

Originally Posted by wholybee

My reasoning is the opposite of that. You set your external alternator to charge parameters appropriate for LFP, and the Lead Acid doesn't care. If you charge your LFP to ~14V give or take, that's just fine for charging Lead Acid. And when it drops to a float voltage of anywhere between 13V-13.4V that is fine for both as well. Maybe you don't charge the Lead Acid as quickly, but starting uses so little energy it doesn't matter.

Edit: and no need for anything else to protect from and HV event.

Unfortunately LA needs higher charge voltage. If you limit it to 14V, you will reduce lifespan significantly. Always use the manufacturer recommended settings.
.

[wholybee]

Originally Posted by s/v Jedi

Unfortunately LA needs higher charge voltage. If you limit it to 14V, you will reduce lifespan significantly. Always use the manufacturer recommended settings.
.

In every other way, a battery only used for starting is being babied. The alternator on my 1965 ford only puts out 13.8V(considered normal), and the battery lasts 5-7 years.

[s/v Jedi]

Originally Posted by wholybee

In every other way, a battery only used for starting is being babied. The alternator on my 1965 ford only puts out 13.8V(considered normal), and the battery lasts 5-7 years.

A 1965 Ford?! Didn’t they have 6V starters? Why are there always such extreme outlandish cases brought against completely valid statements I make!

Today there is not a single 12V battery where the manufacturer claims 13.8V absorption voltage, period.

[sailorboy1]

bet most early readers/posters in this thread have drifted away

[Fuss]

Originally Posted by sailorboy1

bet most early readers/posters in this thread have drifted away

No No... we had a huge party , it was great, really great, one of the best ever, the champagne, the nice ladies...


oh, you didn't , oh I see, you didn't get an invite, strange, very strange...oh well , I'll tell the organisers next time to make sure you're not left off the list!!

[s/v Jedi]

Originally Posted by sailorboy1

bet most early readers/posters in this thread have drifted away

Yes… I put some time and effort in my post #32 but see it was a waste of time. Won’t be doing that any time soon, back to just the reference diagrams

[Fuss]

Different points of view should be welcomed, turning off the good posters should be not. We don’t have to all agree and healthy arguments should be encouraged.
You thread drifted the thread too SB1 by introducing the overheating alternator post.
Not you SB1 but we have enough internet regurgitators on here that ram their concepts down our throats, turning many posts into LTO battery topics is one such example.
Let’s support the posters who speak from personal experience SB1 and not deinspire the good ones!

[rgleason]

This is really nice simple idea to protect the Alternator from a drop-in battery disconnect.
BTW what are the disadvantages of a Victron Argofet 200-2 with an alternator energize circuit for protecting the alternator?

Next problem is to wire a simple alternator case temperature sensor to open the same relay, but I think it would be better for the alternator to simply use a Balmar MC-618 with an alt temp sensor.

For a boat moving or on a mooring, perhaps the solar with the correct controllers will occasionally top charge and balance the Lfp Drop-ins?
I cannot fathom why the Balmar so called Smart Battery Monitor SG200 doesn't have the same shutdown feature as the Victron Smart Battery Monitor BMV-712 integrated into their system!!!!

Originally Posted by s/v Jedi

Let’s say 100% LFP house bank and a LA battery for starting. You can:

- Add Victron Smart battery monitor (not SmartShunt) to monitor house bank and the voltage of start bank.

- put a relay in the Alternator field wire or into whatever the regulator manufacturer recommends to shut down the alternator. (Ignition or B+ wires etc.)

- connect the relay to the NC contacts on the backside of the Victron BMV.

- program the BMV to open the contacts when SOC% > 95% or Voltage > 13.8V etc. etc. You have countless options to stop charging well before the battery gets to a HVC.

So simple it can be.

[s/v Jedi]

Originally Posted by rgleason

This is really nice simple idea to protect the Alternator from a drop-in battery disconnect.
BTW what are the disadvantages of a Victron Argofet 200-2 with an alternator energize circuit for protecting the alternator?

Next problem is to wire a simple alternator case temperature sensor to open the same relay, but I think it would be better for the alternator to simply use a Balmar MC-618 with an alt temp sensor.

For a boat moving or on a mooring, perhaps the solar with the correct controllers will occasionally top charge and balance the Lfp Drop-ins?
I cannot fathom why the Balmar so called Smart Battery Monitor SG200 doesn't have the same shutdown feature as the Victron Smart Battery Monitor BMV-712 integrated into their system!!!!

The ArgoFET is great when you have the same chemistries connected to it.

[rgleason]

S/v Jedi Thanks for your post #32! I had not seen it before I wrote my previous post, but you have clarified the approachs. I am exactly the last guy you posted about.
I want a simple and inexpensive way to do this, and the Epoch Battery with comms and an early version of the Wakespeed ws500 (Smart alternator regulator) is hopefully going to solve one of the main problems.
Thanks for clarifying the condition where an argofet is used.

One option is more expensive batteries with Victron compatible CANbus. Add a Cerbo GX and get a more expensive regulator that also does this CANbus protocol and it will stop the alternator and prevent HVC.

Then there is a subgroup who can’t afford the pricy stuff but still for some reason, probably money related, still want to charge LFP straight from the alternator. For this group I gave the option of doing some tricks with a relay and battery monitor. Not as solid as the other options but that’s what you get when corners are cut

[SOLAR SUPPORT]

Originally Posted by wholybee

You are mixing two workable approaches. If you intend to use a DCDC to limit current, there is zero reason for an isolator. Just connect the alternator to the LA battery, and use the DCDC to charge the LFP.

If you want to use the full charging capacity of the alternator with a good external regulator, use the isolator and skip the DCDC.

There isn't any reason to use both.

Generally, there are two main devices preferred to be used in battery and alternator connections of boats. One of them is the battery isolator. It is used to prevent batteries from transferring energy to each other and to charge all battery groups with one alternator. The other one is battery combiner smart relays. Although they seem to do the same job at first glance, the battery combiner works depending on the changing voltage. The battery combiner smart relay does not constantly isolate the batteries and sometimes allows current to pass in both directions. So, you don't have constant HVC protection when using battery combiner smart relays.

Let's say, the Battery Isolator was present in the installation and isolated all LA battery banks before the LFP switchover. Is this isolation unnecessary when you use the LFP service battery? By using it you get free continuous HVC protection for the alternator. That's why I use the saying of killing two birds with one stone. For LA-LFP transition, if there is a battery isolator in your existing installation, you should use it; If it is not available, you should add one of suitable capacity.

Using a DcDc which limits the alternator capacity. Using the alternator with a smart external regulator without using DcDc. The only difference here is not the increase in capacity. It is possible to achieve the same capacity by using a larger DcDc or two DcDcs. That's why I say there is no point in removing the battery isolator when using DcDc.

If you can charge your LFP batteries using different energy sources in addition to the alternator, using a small DcDc is a very reasonable option.

[rgleason]

Just to beat a dead horse into the ground... How about this setup?

1. Victron Argofet 200-2 with alternator energizing, (see diagram) with an normal sized 70a AGM starter battery and 300a LFP drop-in with the alternator as shown. External Alternator Regulator is user programmed for LFP and has Alternator case temperature sensing.
2. Victron Dc2Dc charger powered from the LFP and charging the AGM, with user adjustable settings and ability to charge at a higher voltage to charge the AGM. It could be 30a but 60a might be better considering autopilot + radar etc. Wish Victron made 60a.
3. All loads would be connected to the AGM, except the Refrigerator, to insure that power would remain on in case of an LFP shutdown. Often when we start the 30hp engine, no navigation is running, and we can shut those down if necessary when starting.
4. Solar Charging to LFP.
5. Shore power is seldom available. Use a small portable charger.

What are the advantages of this setup?

1. Alternator is protected from BMS shutdown by Argofet. (use Balmar APM to)
2. AGM is properly charged by the Dc2Dc
3. Built-in LFP can be less expensive, without comms.
4. Nav equipment remains powered off of AGM in a BMS/LFP shutdown.

What are the disadvantages of this setup?

1. Alternator still requires an external LFP regulator with alternator temp sensing.
2. Argofet could fail, but the APM would likely protect the Alternator.