Lithium on boats - For idiots

[rgleason]

No you are not missing anything. It is just me thinking. I guess I don't need a delay. Thanks.

Originally Posted by flightlead404

Why 5-10 seconds? Aren't you just waiting for the field to collapse? That happens well under a second. In real life alternators are shut off instantaneously all the time without issues

Am I missing something?

[rgleason]

Regarding solutions for LFP BMS cutoff of Alternator (frying alternator).
This thread is excellent.

Balmar 614 vs Li battery BMS cutout

[rgleason]

Here is one of Dsanduril's favorite links on this subject.
Lithium Hybrid: https://www.zwerfcat.nl/en/lithium-hybrid.html
Lithium Hybrid Implementations: https://www.zwerfcat.nl/en/lithium-implementations.html

This last link has excellent configuration graphics. The first link is one Dsanduril favors.

[rgleason]

Frans Veldman has given us a very simple configuration Lithium-Hybrid and OpenHybridBMS system which appears to meet all my needs.

I particularly like the approach to disconnect the LFP Bank (protecting it) and allow the FLA batteries an alternator continue as before.

OpenHybridBMS will control a single relay for the disconnection and control a heating pad to keep the batteries warm when temperature drops as well as control cooling fans. The OpenSource code is on Github and there is a list of Hardware

Full SoC Determination Method

So, there is open source code, but no schematic to build the BMS! Too bad, for me, that makes the BMS not available.

[Epicurean]

Originally Posted by rgleason

You are assuming the charger suggested in the second post is used which was suggested because the alt was going to be connected to bank #1 FLA and the 200ah LFP in bank #2 were being. charged by the FLA through the dc/dc 12/12 charger so the smaller the charger the slower the charge.

OK THanks I didn't really understand why the alternator would be connected to the FLA instead of the LFP. I know you need a different regulator to charge the latter. I need a way to charge my (small) FLA batteries because I charge the house lithiums. I usually just connect them in parallel for a while, but I realize that isn't the best way.

[Randy P]

Thanks again. I’ve been working my way though this, as well as contacting Battle Born and Victron. The boat’s a 1977 Trojan F26 with hardtop (“HT” model).

The power from the Alternator (a “dumb” 70A model) and out to all DC loads is in one cable harness. I added 340W of solar this year to the hardtop and a Victron MPPT 100-30 Smart controller. This is connected to the house bank (now FLA but going to LFPs with built in BMS).

The battery switch is “1” for starter and other engine DC loads (blower, temp, volt, nav lts, etc) The “2” is for all loads, engine and otherwise). The central post of the switch is connected to the power harness, as described above. I will add the Victron Orion 12/12-30 Smart DC-DC charger to the 100AH deep cycle FLA engine/starter battery on switch “1” post and out to the 2 100 AH Battle Born LFPs wired in parallel. I am also adding the Victron Smart 712 BMV to monitor the LFP house bank.

I will use the switch as wired, and switch to “1” before starting the engine and unplugging the shore power (which also powers the ProNautic charger, with will be configured to LFP and ONLY wired to the LFP house bank, and my Norcold AC/DC fridge. This will not allow alternator charge to go to the LFP house bank, but will allow a correctly programmed charge to go the the house bank, while underway. The Victron DC-DC charger is Bluetooth enabled, like the solar controller and temp monitor, and I use/will use Victron Connect to monitor everything on my iPhone and/or iPad.

When off the dock and anchored, moored or remotely docked without shower the engine will be off, and I’ll switch to “2”. The house bank will be charged via solar during the day, and the LFP house bank will have more than enough capacity to handle the loads of lights and AC/DC fridge during the night. The Victron BMV will also enable me to monitor the house bank, either directly from the gauge or via Victron Connect on my phone/pad.

I may not use the ACR as this served its purpose when both banks were FLA deep cycles.

I’ve also changed all lights over to LEDs to further reduce current consumption at anchor.

I feel confident this set up will work and am looking forward to using some good 21st Century tech to update this sweet old lady.

[rgleason]

Randy,
Draw a diagram for both of us, take a picture of it and post it here so we can all see. Sounds like you intend to keep your Alternator B+ to "C" post connection. I don't visualize this and need to do my exercises.

[Randy P]

I did one then my brain shut down again. I’ll get to it after I get back up to the boat and check out what goes where and take more measurements for wire distances, sizes, fuses, etc. I’m waiting to place the order with Battle Born in late December. I’m sure that after I go through all of this my engine will conk out and I’ll be obsessing about how to repair/replace it!

[rgleason]

Does Battleborn provide a BMS normally open/normally closed contact to control a relay (user provided) that will disconnect charge devices, for example? Does it have any communication ports?

[Randy P]

The BMS is built in. Do a web search for Battle Born LFP and you’ll come up with a YouTube video by Will Prose (sp?) who is a young EE who tears one apart. Also get on the web and contact Battle Born. They will follow up and provide answers to your questions. I’m certainly not the one to supply knowledge. I’m only focused on my particular boat and its evolving electrical power needs. I have found the web to be an excellent source of preliminary information with the caveat that you need to validate your sources.

[CarlF]

People are right to worry about the BMS cutoff hurting the alternator but there are multiple easy solutions.

First, this is a very RARE problem. If the alternator regulator is programmed correctly the BMS should NEVER shut off when the alternator is running. The BMS is conceptually like a fuse - you should never need it.

But if it does shut off you don't want to fry your alternator diodes. It's just the same to your alternator as if some idiot turned off the the main battery switch while the engine's running.

Fixes

The easiest fix is to have a non lithium battery somewhere in the charge circuit. This will never "shut off" if the lithium BMS shuts off so the alternator still has something to charge. You can do this using a DC-DC charger or a VSR (voltage sensitive relay) to a start bank. You can also just wire a small AGM battery into the Lithium bank.

Most drop ins are designed for a 14.4v charge and 13.6 (or less) float. This is the same as most AGM's. So you don't have to worry about damaging your start batteries by charging them at the same voltage as the drop-in lithiums. And they are just start batteries that only gets a tiny bit discharged when the engine starts - so they aren't all that worried about the perfect charging profile.

You should not temperature compensate when charging Lithiums. Without temp compensation the charging voltage to the start bank AGM batteries might be a little off spec in very hot or cold conditions. But again it won't be enough to damage them.

Finally, even before Lithium, it's always been a good idea to protect the alternator with a "zap stopper" or equivalent as a 2nd level of protection. The one I like is the Sterling Alternator Protector

https://www.youtube.com/watch?v=03SQMDnY6O0

[Randy P]

Thanks for this information. It’s about the same that I’ve gleaned from all of the many sources I went to when I started thinking about making over the house bank from FLA to LFP. I went with Battle Born because I felt more comfortable with their reviews. I’ve added a Victron 712 BMZ and their 12/12-30 DC/DC charger to BB’s sales quote and they bundled the 2 100AH’s with these additional goodies and gave me a better price/component than I could find on other sites. Plus, no shipping charges. It’s still a BIG jump from buying FLAs, but it has the advantages of longer term reliability and, at the end of the day, satisfies my compulsive need to always fiddle around with my old girl.....

[rgleason]

Randy,
I think you really need to draw that diagram and think hard about what you are doing first, before buying anything.

[rgleason]

Carl
Apparently you don't know where he has his B+ connected, to his "c" post on the 3way.. It is definitely not as simple as you seem to think.

...but FLA battery and zap stop are good ideas.

[Randy P]

Train’s already left the station. Really not that hard if you don’t get paralysis by analysis. If I blow up something it won’t be the first, or last time. Seriously, I appreciate all your advice, thoughts and comments, but found I was going down the rabbit hole. I’m not doing this in a vacuum. I’ll have plenty of help from a few qualified marine electricians who are members of my yacht club.