LiFePO4 reference diagram, Alternator version

[s/v Jedi]

Originally Posted by zurk

reference diagrams are supposed to be correct. yours has obvious flaws. mine is designed by an electrical engineer.

Great, I look forward to your thread to discuss it. BTW, I am an EE and micro electronics designer.

[catalystcat]

I found the reference diagram very helpful and I appreciate all of the effort that went into it and the related version on the other thread. Thanks Jedi.

To forestall some attack on my competence, I'll note that I have a couple of EE degrees and a lot of wiring experience. Also, I am completing the build on my own design and collaborating with a couple of friends doing similar designs.

So, I think I can speak reasonably competently about electrical designs and how they would be interpreted by one who would use it. I have consistently found Jedi's posts to be informative, well-considered and defensible, even in those cases where my opinion might be different.

I often use reference diagrams in considering my design choices. In fact, about 4 different ones inform my current design. But, reference diagrams are useful tools that are based on assumed design criteria and priorities. Like all tools, they take some skill to use (or not) and they usually act as a starting point. Even though some of my design choices were different and some are highly similar, the reference design was helpful.

As for some of the objections in this thread, I will note that some of them are exactly that - objections, not errors.

For example, a large contingent of people use less costly approaches such as self-assembled LFEs. Not my approach, but a reasoable choice for many. Further, not all modern batteries have internal BMS and/or bluetooth. So, the design is not wrong. It just has some different assumptions regarding these aspects.

Similarly, objecting to an assumption that an alternator does not have a BMS is really just objecting to his design assumptions/choices. I'll note that my relatively new boat's alternators do not have BMSs. Neither do those of several of my cruising friends.

In fact, I (and a couple of my friends) have all implemented the Balmar alternator protection device (before seeing Jedi's design). It's becoming a pretty standard approach, though my original design contemplated something like the Sterling isolation device.

As for the "parallel" comment, it was clear to me that this was not a parallel connection and I think any person who is competent to use this reference design would understand that the switch is not in parallel.

As for the Cerbo, this is a design choice, not a design flaw. In fact, I think the sales numbers show a lot of people making this same choice. I personally love the convenience, simplicity, programmability, and other aspects of the Cerbo. This is not about data availability as a sole criterion. I have the data on my iPad, as well. But, having a dedicated tool/display was valuable to me for a lot of reasons beyond the scope of this forum. See, e.g., Will Prowse gushing over the Cerbo in his videos.

Overall, I do not understand what you are trying to accomplish. As nearly as I can tell, these are some objections to design choices, disagreements with a large body of experience about what is common commercially, and some opinions about the suitability of this reference design for a case you seem to think is universal.

I think most of the blowback you have received has arisen from a highly aggressive set of remarks attempting to "correct" something that is not actually incorrect, just different from your assumed case. Jedi has openly discussed his rationales with others who approached him in a collaborative fashion. They don't always agree, but they discuss things with respect and cordiality.

I hope your system works well for you and wish you well on it.

Thanks.


"When you find yourself in a hole, stop digging."

[catalystcat]

One clarification - Actually "alternator BMS" is not a thing. I meant to note that I was interpreting that to be a protected alternator to give the benefit of the doubt.
I forgot to include that. My bad.

[toolbar]

Jedi, you probably posted something in one of your other threads, but could you outline your thoughts on the pros and cons of two separate 4S batteries instead of one 2P4S configuration?

Is there any downside to your config except for a bit more investment for two BMS-Systems+Relays?

Paul

[goboatingnow]

Whilst systems can be built without a Cerbo Gx ( which is actually a custom beaglebone SBC) the Cerbo and even better the Venus Os can be used to tie different systems together. Turning on DVCC then turns the Cerbo/Venus from a monitor into a central charge controller

Bluetooth is useful but protocol issues means devices can’t talk to one another. So you get reporting but little device networking Victron Bluetooth Ve.smart goes a little way to addressing this but very limited.

[s/v Jedi]

Originally Posted by catalystcat

One clarification - Actually "alternator BMS" is not a thing. I meant to note that I was interpreting that to be a protected alternator to give the benefit of the doubt.
I forgot to include that. My bad.

I would almost say that I’ll eat my hat if an alternator regulator with built in BMS exists, but I won’t for fear some whacko in India came up with such a thing

[s/v Jedi]

Originally Posted by toolbar

Jedi, you probably posted something in one of your other threads, but could you outline your thoughts on the pros and cons of two separate 4S batteries instead of one 2P4S configuration?

Is there any downside to your config except for a bit more investment for two BMS-Systems+Relays?

Paul

Let me start with the negatives:

1. It costs more.

Now the positives:

1. The setup is meant so that you can just get by with just one battery. I have 10kWh batteries and with one it’s still luxurious so for 12V I recommend 9kWh because that fits four 700Ah Winston cells. A friend just asked if he gets away with 8kWh and knowing he served in uniform as well, I said sure, you’ll get by with just one battery if the other fails.
So this point is about redundancy, if you loose a cell, you can continue without blinking an eye.

2. I also recommend to start with just one battery, get the experience, see if you can live with that, enjoy a couple years, using some old batteries as the second/backup battery. Then buy/build the second one to replace all the leftover old batteries. Now you have true double capacity plus you have a couple of years difference for lifespan. You can keep using the oldest battery for as long as it lasts, then when it fails you run on the newer second battery, giving you all the time in the world to select and buy a new battery and you have gotten everything out of the old battery, while with a single battery, people replace it early to prevent a failure with total power loss.

3. The extra costs also get you a second BMS, Fuse, Switch and battery monitor. If any of these fail on a passage or somewhere far from civilization, you can keep going.

4. More power. Because you select capacity for each battery so that you can work with just ine of them if need be, you will have more capacity than for a single battery where such reasoning isn’t followed (most choose “more than enough” capacity for a single battery).

These reference diagrams only show one MPPT, Inverter/Charger etc. but I recommend to get two of each for those as well, for similar reasons

[s/v Jedi]

I feel sorry for Zurk; he may have deserved some of this but it should stop now. I’m sorry zurk, I think I steered you into a position you couldn’t know how weak it was

I hope you see this diagram is okay and I’m here to explain any part of it that you don’t understand. I’ll also discuss your diagram to help you see the differences:

- first you obviously have a catamaran so you have two engines, two alternators and two regulators. Just imagine all that double in my diagram.

- you have isolation for your start batteries using dc-dc converters, this is cool, I have the same thing. But it seems you have one start battery for each engine and can’t start an engine from the battery that’s with the other engine. I recommend you install a service A-B-OFF-A+B switch at each engine to choose a battery to start from.

- you seem to have two 260Ah start batteries plus two 260Ah house batteries. I guess they are all the same and all are LiFePO4. In that case I recommend to buy new start batteries, using two Odyssey PC2100 AGM batteries that are only 100Ah each, and add the two 260Ah batteries to your house bank so that you double it’s capacity.
The reason is that you have way too much capacity dedicated to starting the engines and rather low house bank capacity. Also, start batteries are always fully charged and this kills LiFePO4 batteries while AGM’s love it.
You need to reprogram the dc-dc chargers for an AGM charge profile

- Make sure each battery has a fuse and a disconnect switch. It’s required.

[zurk]

lol. interesting take.
1. yes i have a cat obviously.

2. i could install an A/B switch but it just adds more wiring. if i really need to i can flip cables manually from one to the other since the start batteries for both engines are located together within 2 feet of each other.

3. All my batteries are 460Ah not 260Ah. I have 2 x 460Ah house and 1 X 460Ah start batteries for each engine (2 start total). So a total of 4 x 460Ah batteries.

Yes they are all LiFePO4. The reason for that is the start batteries always power network, bilge pumps and engine start so there is always a minimum 50W draw on them 24 x 7. A batteryprotect cuts them off at 60% should they get excessively low.

No they wont be fully charged as they have a constant draw down. also no AGM because an AGM wont be able to handle my engine start and network power.

4. Yes obviously mega fuse but im skipping the disconnect switches since i have batteryprotect instead.

[JRM]

This tracks quite closely with what I have sketched out for myself initially, however as I work on actually installing it, I would like to bounce a few variations off the collected wisdom here. Boat is a 40' monohull.

I've moved my house batteries from the engine space into a newly built compartment that is on the opposite side of the boat. I've upgraded from golf carts to drop in LiFePo for a total of 800Ah. All Victron goodies, very similar to the diagram. A lot of the equipment is stuff we cruised with (on a trawler), but I'm taking with me as I re-refit a sailboat (long story.) Upgrading to electric galley "soon..."

The original starting battery is a Group 31 AGM that is just foreward of the engine space on the starboard side. Originally charged with a Blue Seas ACR that has been removed.

Trying not to outhink myself, but the original windlass wiring terminates just aft of the starting battery (at the old house bank.) My plan is to run the alternator output to the starting battery and use an Orion to the house. It's a 120 amp alternator, but it won't last long charging LiFePo at that rate. I can either extend the windlass cables about 20' (40' run total) to the new batteries, or upgrade the starting battery to a 4D to also run the windlass. The starting battery needs to be replaced regardless, and there is plenty of room for the larger battery. Your reference diagram shows the windlass running from the house positive bus. This I can do, but I rather like the idea of keeping the windlass on a traditional lead acid battery to account for the possibility of a load spike if/when the motor loads up. The estimated transient current max for my windlass size is within the spec of my total BMS OCP (400A), so it boils down to the cost delta for the additional 2/0 wiring or larger battery. And the PITA of running it.

Is there something I'm missing? Am I using the max draw argument realistically or am I just trying to confirm my desire not to run another set of 2/0 cables?

Thanks in advance,

JRM

[catalystcat]

One observation relating to the disconnect switches - in addition to the ABYC guidance of section 13, battery disconnects can be super convenient for when you do battery balancing because they make it easy to fully charge individual batteries without physically disconnecting the connections. Since you only have 2, that may not be a big deal to you.
In my case, I have 6 house batteries. So, to me it means a lot of convenience.

[catalystcat]

JRM - Maybe consider a smaller Li battery located in a convenient location and dedicated to the high current (e.g. windlass)? Maybe near the old house bank location.
You can get the high amperage tolerance at very light weight, and it would probably cost in the neighborhood of that many feet of marine grade 2/0 plus lugs, etc. (Marine grade 2/0 from Ancor was about $6/ft a few weeks ago and lugs were about $5 in small quantities.) You may have to add a separate charger (or DC-DC from the start bank) or run a lower gauge wire to charge it. I don't know your setup, but that might be a convenient, lower weight, comparable cost alternative.

[catalystcat]

Alternatively, do you have a spot for a small 80Ah or so Li battery near the windlass? Ideally with an easy way to provide charging.
I think there was a thread here on this concept a couple of years ago.

[newhaul]

Originally Posted by catalystcat

Alternatively, do you have a spot for a small 80Ah or so Li battery near the windlass? Ideally with an easy way to provide charging.
I think there was a thread here on this concept a couple of years ago.

Or go my route a manual windlass
This one is actually mine now
https://www.cruisersforum.com/forums...ss-210265.html

[zurk]

Originally Posted by catalystcat

One observation relating to the disconnect switches - in addition to the ABYC guidance of section 13, battery disconnects can be super convenient for when you do battery balancing because they make it easy to fully charge individual batteries without physically disconnecting the connections. Since you only have 2, that may not be a big deal to you.
In my case, I have 6 house batteries. So, to me it means a lot of convenience.

actually mine are modern batts so they self balance. they have +,- and CAN terminals and you run canbus wiring between them.