System redesign to drop in LFP

[phantomracer]

Originally Posted by Pete7

Don't know. I just wired a lead acid in parallel with the LFP. That was a couple of years ago, still working fine and provides redundancy if the LFP BMS shuts down.

Pete

So literally just wire in a FLA battery in with the LFP bank, set the alternators regulator (614/618) to a LFP type?

I guess that would take care of the starting redundancy.. however, i need to find real estate on the boat for another battery!

Even if the LFP bank dumps, the FLA battery will take over.

Could a small motorcycle battery be used (possibly can't start the engine), or should it be sized near the capacity of the LFP batteries?

Edit.. added rough diagam of how I understand this option

[wholybee]

Originally Posted by phantomracer

Thank you...



I thought the BMS in a drop in is 'dumb' and just shut the battery down all together (see RC's pic below)? if the BMS cuts off due to being 'full' or high voltage, it will still provide power out?

Not that dumb. AFAIK every drop in has the ability to stop current in only one direction. Certainly, any decent one you should be considering will.

For the other questions, Argo vs DCDC, vs a battery directly in parallel. How large is your alternator? Is it a small 70A model, or a 200A model?

If you have a 200A alternator, a DCDC would limit you to about 30A depending on the DCDC you buy. With a 70A alternator, you probably don't want to run it more than 30A continuously anyway. The DCDC is usually reserved for small alternators with an internal regulator.

Between an Argofet or putting a lead acid directly in parallel. Putting a LA directly in parallel is a simple low cost fix to avoid a complex rewire. You already have the duocharge. Whether you use the duo charge(and accept its 30A limit) or replace it with the Argofet, you don't have a complex rewire. You already have the wiring you need. Maybe a LA battery to put in parallel is a bit cheaper than an Argofet, but it isn't an option I would consider in your case.

[phantomracer]

Originally Posted by wholybee

Not that dumb. AFAIK every drop in has the ability to stop current in only one direction. Certainly, any decent one you should be considering will.

For the other questions, Argo vs DCDC, vs a battery directly in parallel. How large is your alternator? Is it a small 70A model, or a 200A model?

If you have a 200A alternator, a DCDC would limit you to about 30A depending on the DCDC you buy. With a 70A alternator, you probably don't want to run it more than 30A continuously anyway. The DCDC is usually reserved for small alternators with an internal regulator.

Between an Argofet or putting a lead acid directly in parallel. Putting a LA directly in parallel is a simple low cost fix to avoid a complex rewire. You already have the duocharge. Whether you use the duo charge(and accept its 30A limit) or replace it with the Argofet, you don't have a complex rewire. You already have the wiring you need. Maybe a LA battery to put in parallel is a bit cheaper than an Argofet, but it isn't an option I would consider in your case.

Originally Posted by wholybee

Not that dumb. AFAIK every drop in has the ability to stop current in only one direction. Certainly, any decent one you should be considering will.

Really.. did not know that.. If that is the case, there is no need for a buffer FLA battery in parallel. I am just repeating what Balmar told me, that a "drop in" will likely totally disconnect if the battery gets overcharged, or even 'full' on initial bulk charging. then again, they don't make batteries.

Originally Posted by wholybee

Maybe a LA battery to put in parallel is a bit cheaper than an Argofet, but it isn't an option I would consider in your case.

Not looking for low cost. Failsafe and as simple as possible.
The alternator is a 100a balmar, with 614 regulator (planning on going with a 618), with the altmount 10 rib belt kit. Not opposed to upgrading the alternator, rather not, but not opposed.

If I understand you right, you would go with the argofet over DCDC. using the starting AGM instead of another FLA battery? (edit..adding Would this would likely eliminate/limit the use of the house battery to start the engine (3GM30) as the LFP's BMS might trip on over current ?

Using a FLA in parallel, sans DCDC/Argo, is acceptable but not ideal?

This is what I am leaning toward, 2 of these Epoch 105ah

[hlev00]

Originally Posted by hjohnson

If you’re building a mission critical power system based on LFP, you need to design it so that BMS disconnects will never occur …

But you still have to include protections in case they do.

[phantomracer]

Originally Posted by hlev00

But you still have to include protections in case they do.

Yes, will have the balmar APM-12 and have the regulator shut down the alternator if the LPF disconnects

[wholybee]

Originally Posted by phantomracer

Really.. did not know that.. If that is the case, there is no need for a buffer FLA battery in parallel. I am just repeating what Balmar told me, that a "drop in" will likely totally disconnect if the battery gets overcharged, or even 'full' on initial bulk charging. then again, they don't make batteries.




Not looking for low cost. Failsafe and as simple as possible.
The alternator is a 100a balmar, with 614 regulator (planning on going with a 618), with the altmount 10 rib belt kit. Not opposed to upgrading the alternator, rather not, but not opposed.

If I understand you right, you would go with the argofet over DCDC. using the starting AGM instead of another FLA battery? (edit..adding Would this would likely eliminate/limit the use of the house battery to start the engine (3GM30) as the LFP's BMS might trip on over current ?

Using a FLA in parallel, sans DCDC/Argo, is acceptable but not ideal?

It's a judgement call between the argofet or the dcdc. In your case, I would probably use an argofet. I personally use a DCDC, but in my case I have enough solar connected to my LFP I don't need charging from the alternator. My alternator is connected to the lead battery, and the DCDC is switched off and only turned on very rarely if my solar isn't keeping up.

ABYC does not allow a lead-acid directly in parallel, and most professional electricians will advise against it. It isn't specific to this use case, just a rule that says mixed chemistries cannot be connected in parallel. However, there are many examples of it working fine for this purpose. Again, I think it is a judgement call. If your boat is insured then a survey would probably flag it as a problem.

[phantomracer]

Originally Posted by wholybee

It's a judgement call between the argofet or the dcdc. In your case, I would probably use an argofet. I personally use a DCDC, but in my case I have enough solar connected to my LFP I don't need charging from the alternator. My alternator is connected to the lead battery, and the DCDC is switched off and only turned on very rarely if my solar isn't keeping up.

ABYC does not allow a lead-acid directly in parallel, and most professional electricians will advise against it. It isn't specific to this use case, just a rule that says mixed chemistries cannot be connected in parallel. However, there are many examples of it working fine for this purpose. Again, I think it is a judgement call. If your boat is insured then a survey would probably flag it as a problem.

I was leaning toward the argofet, as it seems to be an elegant/simple solution.

Mixing FLA and LFP, on the surface, makes me nervous, but understand how it can work. I can see how a pro would flag it as a problem, however.

IF I do this DIY, I want it to look like a pro did it.

[phantomracer]

Thoughts on this setup?

Will lose the ability to start from the house bank. I guess I could wiring a third bank as a second starting battery on the 3rd output on the Argofet

The regulator will be set to LFP , I assume, will that be OK for the starting battery ?

[CarlF]

With my two years using KiloVault drop-ins I have never come close to a BMS shutdown because I am conservative about the voltage settings and charging and discharge amos

1. Kilovault specs a low 14.1v absorption charge. This is far below the level that would shut down the BMS. A advantage of the Kilovault BMS is that it does cell balancing at 14.0v so there’s no reason to ever go to 14.4v. The battery delivers the full rated AH at 14.1 voltage. But only my Victron solar charge controllers are set to 14.1 as they can be set to zero absorption time.

2. The alternator regulator is set to an even lower 14.0v absorption so that it shuts off early. The batteries can easily take 6 minutes at 14.0. My Victron Multi which has a minimum absorption time of one hour is set to the same 14.0.v. Kilovault techs approved this.

3. The alternator charges directly to the house bank because there’s no point in using a tiny 30 amp dc-dc charger to charge a large house bank. Instead, a Victron DC-DC charger charges the start bank. As it is always connected, it provides a load that will absorb any surge from a BMS shutdown safely into the lead acid start battery.

4. A Balmar alternator protector across the alternator terminals provides a “belts and suspenders” protection of the alternator should the impossible happen.

5. I installed four 300 AH batteries with a combined maximum charge/discharged rate of 800 amps. This is over twice what is required (the bank class T fuse is 400 amps).

[hjohnson]

Originally Posted by hlev00

But you still have to include protections in case they do.

That's why I'm running a system where the BMS has to actively "pat" the alternator. If it stops hearing from the BMS, or the BMS goes into alarm or warning state, the alternator is shut down.

[Pete7]

Originally Posted by phantomracer

So literally just wire in a FLA battery in with the LFP bank, set the alternators regulator (614/618) to a LFP type?

Perhaps watch this YT video.

A motor cycle battery might be a bit small. I know our auto pilot, two chart plotters, VHF and AIS etc can draw 10A. What I don't want is the BMS's cutting out at night as we enter an unfamiliar harbour.

https://www.youtube.com/watch?v=sqT2...k%27sAdventure

[krid2000]

Originally Posted by CarlF

3. The alternator charges directly to the house bank [... A] Victron DC-DC charger charges the start bank. As it is always connected, it provides a load that will absorb any surge from a BMS shutdown safely into the lead acid start battery.

Interesting. Can you expand on how the DC-DC charger would absorb the very short but high voltage surge? Can't find anything about that in the Victron manuals.

Thanks!
Dirk

[rgleason]

Originally Posted by maine-cruiser

On my LFP setup I have the Charge Enable/Disable output from the Victron VE.bus BMS connected to the IGN. input of the Balmar 614 regulator (through a solid state relay). If the BMS signals to disable charge then the Balmar is turned off and alternator output is disabled. I'm not sure this has ever happened though since the Balmar is programmed for 14.1 v and the trip point for the BMS appears to be cell voltage >4v. I guess in the case of 'Drop In' LFP you don't have externally available charge disable output so it's possible that if BMS in battery triggers you will lose DC power. As others have said, it should not happen if charging devices are properly programmed.

I do have a separate start battery that is charged via a Balmar Duo charge from house bank. There is a battery switch that connects either start battery or house bank to starter for emergency start from house bank.
Bill

Bill can you describe your system more completely, or do you have diagram? I am interested.

My friend Goboatingnow posted a diagram that I worked on in this thread
https://www.cruisersforum.com/forums...ml#post3682941
The goal was to have an easily established procedure for emergency operation when the LFP or BMS failed and to be ABYC compliant.
This thread generated a lot of discussion and thought. This diagram was based upon great input from Goboatingnow, Hjohnson and Wholybee. It is somewhat similar and derived from the system that Hjohnson has on his boat. After costing it out I found that it would be more $ than I could afford for the purpose.

Later s/v Jedi Nick who is very active and knowledgable in this forum posted another good diagram which makes the Alternator the primary charge source https://www.cruisersforum.com/forums...ml#post3681055

Since doing the diagram and thought process that Goboatingnow posted, I have some other ideas for a system, which I may more completely develop, but right now I find this drop-in approach very interesting.

We need to develop a really simple system that complies with all aspects of ABYC, and I can't understand why Dropin manufacturers refuse to add canbus communications with a remote alternator regulator (Balmar or Wakespeed or Nordkyn, or ??) which will alert and send a simple signal (NO/NC contact) to the regulator to shutoff the alternator field.

This simple improvement would make a huge difference in safety and operation of LFP. How many years will we have to wait?

The other essential improvement would be to beef up the BMS FETS and wiring so that Alternator charging at good C rates is reasonably achievable with some factor of safety.

My problem is also finding the space below for the batteries and BMS.

[rgleason]

Originally Posted by krid2000

Interesting. Can you expand on how the DC-DC charger would absorb the very short but high voltage surge? Can't find anything about that in the Victron manuals.
Thanks!
Dirk

I am not so sure you can depend on this alone. It is the FLA battery that does the absorption of the spike, I like to think of it acting like a big capacitor. For that matter you might be able to use a big capacitor for both help ing to start the engine and to help with absorbing spikes. There was one thread that discussed this idea.

I think the problem with directly paralleling LFP with FLA is that they are different chemistries and if the FLA develops a short there is an instant meltdown including all the power from the LFP!

I don't know if ample fusing would comply with ABYC. Perhaps S/V Jedi or someone else would know.

[phantomracer]

Originally Posted by rgleason

Bill can you describe your system more completely, or do you have diagram? I am interested.

My friend Goboatingnow posted a diagram that I worked on in this thread
https://www.cruisersforum.com/forums...ml#post3682941
The goal was to have an easily established procedure for emergency operation when the LFP or BMS failed and to be ABYC compliant.
This thread generated a lot of discussion and thought. This diagram was based upon great input from Goboatingnow, Hjohnson and Wholybee. It is somewhat similar and derived from the system that Hjohnson has on his boat. After costing it out I found that it would be more $ than I could afford for the purpose.

Later s/v Jedi Nick who is very active and knowledgable in this forum posted another good diagram which makes the Alternator the primary charge source https://www.cruisersforum.com/forums...ml#post3681055

Since doing the diagram and thought process that Goboatingnow posted, I have some other ideas for a system, which I may more completely develop, but right now I find this drop-in approach very interesting.

We need to develop a really simple system that complies with all aspects of ABYC, and I can't understand why Dropin manufacturers refuse to add canbus communications with a remote alternator regulator (Balmar or Wakespeed or Nordkyn, or ??) which will alert and send a simple signal (NO/NC contact) to the regulator to shutoff the alternator field.

This simple improvement would make a huge difference in safety and operation of LFP. How many years will we have to wait?

The other essential improvement would be to beef up the BMS FETS and wiring so that Alternator charging at good C rates is reasonably achievable with some factor of safety.

My problem is also finding the space below for the batteries and BMS.

I just assumed they did, when I started this thread, more I dug in, I realized there is a potential problem !! I initially thought, just wire the regulator to the battery BMS.. only to find out that can't be done on Drop ins!

Thoughts on using the argofet on my previous comment ?

Alternator to the argofet, split to the starting and LFP. should this mitigate most changes of the BMS disconnecting?