Hybrid or No Hybrid Power system?

[MWGDVC]

Oh, and attempting to charge them when they are frozen. Don't do that.

[wholybee]

Originally Posted by MWGDVC

Dockhead,
I believe you have outlined the advantages of LiFePo very well, as so far as I understand them.
Two things that kill this chemistry I am told are heat and low current overcharge. Once any cell is charged to 100% stop the charge. No float of any kind. This will cause the Lithium Ion Salts to convert to Lithium metal. This is an unrecoverable condition that will reduce the capacity of the batteries. Keeping the cells top balanced means, ideally, they all reach 100% state of charge at the same time.

To be clear "no float of any kind", while technically correct, isn't correct using common nomenclature programming a charger.

"Float" is a low current charge a a voltage slightly higher than the resting voltage of the battery. Example, a 12V lead Acid battery has a resting voltage of 12.7V, and a Float voltage of 13.5 volts. But, for an LFP battery, the resting fully charged voltage is 13.8V. Any voltage lower than that is technically NOT floating, but that is what a charger will call it. Setting a "float" voltage of 13.5V on an LFP is perfectly fine, because by doing so when the battery charges to 100% at 14.x volts, changing to "float" stops all charging current, just like what you are supposed to do.

[wholybee]

Don't keep any Lead Acid batteries for house use. One thing is sure, Lead-Acid batteries are not as reliable as LFP. They require maintenance. They Require being fully charged a couple times per week. They quickly begin to lose capacity and that is difficult to judge and account for. You will replace that Lead Bank between 2 and 5 times before the LFP is end of life.

Why not more LFP in that space, if you want a backup bank to switch to? Or put 280Ah in each space if you don't want to buy more LFP? But get the lead out and keep it out, for sure.

[coldfish]

I've gotten several LifePO4 batteries from this company:
https://cerrnss.aliexpress.com/store/1101560622 (all 72v 50ah) They've been great, but take a long time to arrive. A couple months.

I'd seriously recommend converting from LA because of *weight*. Each is the equivalent of six standard car batteries, but I can pick up one of those batteries myself.

Each comes with a built in BMS with Bluetooth apps, so you can check their charing status. Each BMS will stop it from overcharging or undercharging. (and I'm 100% certain all standard LifePO4 batteries come with a BMS now, otherwise risk of overcharge is simply a lawsuit waiting to happen)

I actually use a step-down for my standard house bank and a 12v backup for a secondary bilge system + emergency lights. Many newer appliances run on 24v better (ie my electric head is 100% better using 24). Additionally, if you are installing something that's a distance from your bank, it can cause voltage drop that can affect things. For example, if you have a winch on the bow, but your batteries are 30' away in the stern, you're going to need a big fat cable, like 8awg or something to get up there without losing too much voltage. Whereas a 24v has less drop for the same distance on the same cable.

Just some ideas. Good luck.

[Renegde_Sailor]

Originally Posted by MWGDVC

Renegde Sailor,
I agree that minimizing distance is very helpful, I wish I could do what you did.. Regrettably on my smaller boat, I have a chain locker with 280'/85M of chain, a 55lb/25KG anchor on the bow, and 70 gallons/265l. of water in the fwd. tank. I haven't the space, nor could I afford the additional weight forward to add 50-60 lbs more forward for a windlass battery. Not such an issue in larger boats.

Moving batteries to the engine room is probably fine for AGM,(that is where my start battery is, short cable run that way), but as I understand LiFePo is best stored at 73F/23C for maximum life.

Hence forth why it is waiting till after I rebuild the space because I am building a partition that separates the engine from the space where the inverter and battery box is located. This way I can do a much better job of sound insulating the engine.

[Loredo]

Dockhead,
i sense that you're unable to make an educated decision. I fully understand, it took myself a couple years to get off the fence and build my own house bank. Different from you, I've got a rock solid 40 years of experience in electronics. I just had NO knowledge at all about any lithium system. If you keep asking questions on this (any) forum, all you will get is personal mostly -opinion- based answers and then the contrary of everything.
I ended up watching a ton of youtube mostly to understand the first step, actually building a battery made out of single cells. There's more to it than what you might think you know. This guy I found very helpful :

https://www.youtube.com/watch?v=0jAXjoC97dk

That's just one video, he's got several useful ones. For example, would you think it's needed to polish every single pole of the cells, the bus-bars and then use graphite based conductive paste on every single contact point?
Good build practice makes or brakes a LFP battery. I tested with and without graphite paste and the difference (mil-Ohm)is very measurable.



Anyhow, what I really want to tell you at the end is, do not go down into the LFP rabbit hole before you're fully convinced you know what you want, what you need, and how to get there. Either fully educate yourself or find a person you trust to assist you. Personally, I find it to be a horrible idea to mix LFP and lead. Unnecessary complication... YMMV

[carstenb]

Originally Posted by Loredo

Dockhead,
Personally, I find it to be a horrible idea to mix LFP and lead. Unnecessary complication... YMMV

I wish that you would expand on this- Everyone tells me that you need a lead battery to run your starter, anchor winch and thruster since they are deep draw and lithium isn't

Are you running everything off the lit?

[CarlF]

A lot of people are doing something similiar. A few things to consider.

You can easily make the lithium bank 24v or even 48v and keep the AGM bank 12v. Many are now doing this to use 48v DC watermaker and air conditioners. Much more efficient than inverting to 110v or 220v. And as you have already done- you can use a 24v or 48v alternator for much higher wattage charging. Paired with a Wakespeed - or even better the even more capable Argo Zeus - alternator controller you can reasonably consider removing the genset if you have one. I realize that you aren't likely to do this as your equipment is already purchased and you are going for minimium change,.

While not all agree, the DC-DC charger to the AGMs protects the alternator should there be a BMS shutdown in the lithium bank. This removes the biggest risk of connecting an alternator directly to a lithium bank. The DC-DC charger is always on and will bleed any surge from the BMS shutdown into the AGM's (the surge lasts less than a second). While I'm not sure all brands of DC-DC chargers can handle this I was told by a Victron engineer that theirs will without damage. BTW, the new Victron 50Amp DC-DC charger is much improved over the older 30amp model.

Since the AGM's will almost always be at 100% charge, they will last just about forever without the damage of PSOC sulfation that normally plague them when use for house bans.

Whether you can run your bowthruster depends on the lithium battery bank maxium amps. Many have a maximium of 150amps before BMS shutdown. If you have four batteries in parallel you can handle 600 amps which would support the bow thruster. But many prefer to use Lead Acid for engine start and bow thrusters for this reason.

If connecting more than 2 lihtium batters in parallel, it's best to wire them with equal length cables going to a bus bar. Lithium batteries are much more prone to unbalanced charge and discharge due to different resistance from unequal cable length. This can cause one battery to be at a much lower state of charge than the others.

Be sure to use a Class T fuse in the Lithium bank. If the lead unfused length are more than the ABYC allowed 18"(?) before the fuse, consider also adding a BlueSea terminal fuse on each battery positive post (although this is a bit of belt and suspenders)

[Loredo]

My boat is actually very similar, battery layout wise, to Dockhead's. Engine and generator have dedicated 12V (Lead) starter batteries. Each with their own dedicated alternator and battery charger. There's also a dedicated 12V lead battery for the 12V services like VHF and a few other things. It's charged from the engine's 12V alternator. House battery is a 1680 AH @ 24V LFP bank (now). There is a second externally regulated 24V HD alternator on the engine. Bow and stern thrusters have each their own LTO battery bank (80 & 40AH). Those are charged through a B2B from the house bank. The house bank supplies the all winches. With that large of a house bank not a problem. The induction cooking and soon to come electric oven are more power hungry than the winches. I think the highest power draw I've seen thus far was roughly 360ish amps. Way less than 0.5C EVE recommends. Thus far, seems to work nicely.

[Nicholson58]

If to
OP is having trouble or doubts with the system design please consider using the free, expert assistance provided by Hank. Refer to my post #12 above. Much assistance, design, software, special hardware provided. Hank started with model and serial numbers for every relevant device. We worked together on many aspects regarding the desired functions and operation. Hank is a boater and Lithium early user.

House bank and starting bank high amp output.

[Na Mara]

Hi Dockhead,

When I sent the litium route the advice I got from the victron guys was to have dedicated AGM batteries for the engine starter and bow thruster, and to have constant loads (AIS, bilge, etc) off the thruster battery, and to have everything else coming off the Lithium.

The reason was that these two items have large surge currents that can cause a temporary voltage drop on the lithium batteries which the BMS interprets as the batteries being at low voltage which then causes an ATD cut off event. This is temporary (30s) and does no damage but if it happens every time you engage the thruster… you get the gist.


System works well for me.


Best Na Mara

[Dockhead]

Thanks to everyone for the great input. I hope this thread is useful to others who are going through the same thing.


So a vision is starting to form of keeping one lead bank for "technical loads" -- thruster, windlass, winches. This solves several different problems, and is elegantly and easily solved since my boat was originally built with a separate bank with separate battery box, buses, etc., for this very purpose. So all I have to do is buy 4x AGM batteries (unfortunately a lot more expensive than lithium now) and a B2B charger and there's practically no reconfiguring or rewiring of anything.


Then I build my 560AH bank of 2x 24v batteries each made from 8x 280K Eve cells, 2x inexpensive Mosfet BMS's, appropriate shunts, contactors, fuses, and a Cerbo to monitor the whole thing, and I should be good.



Maximum amp draw from the house bank -- which is not connected to the "technical" loads -- is whatever my inverter can draw, which is about 275 amps for a few seconds when surging 6kW, plus regular house loads. It will not be too hard to design for this.


I would need some kind of changeover to draw power from the AGM's for backup house loads use (especially nav and comms as we were discussing). Perhaps a two-way B2B charger would work for this; otherwise maybe just use a battery switch.


I was intrigued by the idea above of using the B2B to protect the alternator but I have to think through those circuits. The alternator will be connected only to the lithium bank, but I guess I could connect the B2B upstream of any contactors -- yeah, maybe that would work. Otherwise, Sterling sells an inexpensive alternator protector -- I don't think this is a difficult problem.


Thanks again for all the input. I'll post some designs when I get that far. This will be a nice winter project.

[Na Mara]

As I said before, that is almost exactly the Victron specialist recommendation I received, it’s what I installed, and it works flawlessly.

Here’s hoping the install goes well.

[Tupaia]

Originally Posted by carstenb

I wish that you would expand on this- Everyone tells me that you need a lead battery to run your starter, anchor winch and thruster since they are deep draw and lithium isn't

Are you running everything off the lit?

I converted from LA to LI but did not want to upgrade my engine alternators, my engine hours (50hr/yr) are so low as not to make this necessary, so I installed 2 high output race car batteries for engine start. https://www.mlperformance.co.uk/prod...tery-26ah-600a


With enough LI in parallel they are more than able to supply deep draw loads. However, I found that I always had my engine running when using the anchor windlass and my Li bank is not that big and with no immediate charging, especially during early morning departures, I installed a 40A B2B that enables the engines to replenish the windlass draw.


It's not so much that the LI can't start engines because they can but the LI requires expensive upgrades to the alternators or regulators.

[Dockhead]

Originally Posted by Na Mara

As I said before, that is almost exactly the Victron specialist recommendation I received, it’s what I installed, and it works flawlessly.

Here’s hoping the install goes well.

Thank you!