Charging LFP dropin questions

[SV Confianza]

We essentially have the same setup you’re proposing, except with a high amp relay in place of the ACR. The bats are paralleled when ignition is on. Different chemistry.

The setup was advised by Mr Rod Collins himself. The start bat only needs a top up, and it just sees float voltage while paralleled. Smartshunts show the start bats only take 1-2 amps off the bus while paralleled. And they always stay topped up at 12.7-12.8 volts.

About 1500 engine hours on this setup (two engines two start bats, 1000ah lithium). Simple and works well.

[CaptainRivet]

Originally Posted by SV Confianza

We essentially have the same setup you’re proposing, except with a high amp relay in place of the ACR. The bats are paralleled when ignition is on. Different chemistry.

The setup was advised by Mr Rod Collins himself. The start bat only needs a top up, and it just sees float voltage while paralleled. Smartshunts show the start bats only take 1-2 amps off the bus while paralleled. And they always stay topped up at 12.7-12.8 volts.

About 1500 engine hours on this setup (two engines two start bats, 1000ah lithium). Simple and works well.

Why do you need this lead at all?
just get rid of it, your 1000AH will start the engine any time...
2 engines is the prefect setup to start one directly from the house as hybrid house bank (like most mass production catamarans have it from factory as standard setup) and the 2nd engine starts a from starter/house backup.
Both alternator charge via an argofet both batteries. Like this you can anytime swap the lead of the 2nd engine to a lithium or LTO one without any changes.
Simple and cheap.
Doesn't matter from whom that recommendation came, if your boat has a battery relevant insurance claim in US the insurance will easly bail out as forbidden by ABYC.to combine different chemistry with Lithium.
It really just amazes me with what persistence boaters need to have this dreaded stonage and unsafe lead batteries onboard their vessels and even create unsafe and senseless installations to just keep them.

[SV Confianza]

Originally Posted by CaptainRivet

Why do you need this lead at all?
just get rid of it, your 1000AH will start the engine any time...
2 engines is the prefect setup to start one directly from the house as hybrid house bank (like most mass production catamarans have it from factory as standard setup) and the 2nd engine starts a from starter/house backup.
Both alternator charge via an argofet both batteries. Like this you can anytime swap the lead of the 2nd engine to a lithium or LTO one without any changes.
Simple and cheap.
Doesn't matter from whom that recommendation came, if your boat has a battery relevant insurance claim in US the insurance will easly bail out as forbidden by ABYC.to combine different chemistry with Lithium.
It really just amazes me with what persistence boaters need to have this dreaded stonage and unsafe lead batteries onboard their vessels and even create unsafe and senseless installations to just keep them.

I would debate the assertion that it is unsafe given proper class t fusing, and actually should have mentioned that in my original response. However, i have been debating your thought of just ridding the starter bats as you suggest. Would make things much simpler.

The problem is that the house bank is all the way midship in the stbd hull. So the cable run to the port engine is a bit of an issue. I’m still running a fully 12v system.

I thought about just replacing the starter bats with LFP and let them charge themselves off the house bank in parallel (with fuses in between) without a dc/dc charger. But based on the distance, it probably wouldn’t work. I might test it anyway and record the data with smart shunts just for fun for a bit.

Also have considered separating into a hybrid 24v/12v system.

[lifeofreilly57]

I just went simple.
Victron controllers for panels, an inverter/charger for the generator, dc to dc charger for the starter battery.
Built in BMS on lfpo batts.
Balmar controller on my 200 amp alternator with the top output reduced and a taper curve to keep from overheating.
I have enough panel power to keep the batteries topped up, even on a cloudy day.
Simple and effective. The dc to dc charger allows me to have dissimilar battery chemistry without issues.
Even when left on its own if I have to leave the boat for a bit the batteries stay topped up.
I considered different options prior to wapping over and found the simplest most direct application. Fortunately I have a friend whos a marine electrical engineer who helped cut through the multitude of options.
Of course you'll have your battery positives fused prior to the positive buss.

[hzcruiser]

Originally Posted by lifeofreilly57

I just went simple.
Victron controllers for panels, an inverter/charger for the generator, dc to dc charger for the starter battery.
Built in BMS on lfpo batts.
Balmar controller on my 200 amp alternator with the top output reduced and a taper curve to keep from overheating.

That's one big alternator! And it's feeding the house bank? From there the DC2DC charger goes to the starter batt?

I have enough panel power to keep the batteries topped up, even on a cloudy day.
Simple and effective. The dc to dc charger allows me to have dissimilar battery chemistry without issues.
Even when left on its own if I have to leave the boat for a bit the batteries stay topped up.

You did take into account that LFPs don't want to be stored at 100% SOC?

I considered different options prior to wapping over and found the simplest most direct application. Fortunately I have a friend whos a marine electrical engineer who helped cut through the multitude of options.
Of course you'll have your battery positives fused prior to the positive buss.

Spec'ed to the wire or the batt's capacity?

All in all, this sounds like a good solution!

[hzcruiser]

Originally Posted by SV Confianza

[...]

I thought about just replacing the starter bats with LFP and let them charge themselves off the house bank in parallel (with fuses in between) without a dc/dc charger. But based on the distance, it probably wouldn’t work. I might test it anyway and record the data with smart shunts just for fun for a bit.

Also have considered separating into a hybrid 24v/12v system.

You should test it, as it will work!

What's the advantage of some hybrid system?

[lifeofreilly57]

Originally Posted by hzcruiser

That's one big alternator! And it's feeding the house bank? From there the DC2DC charger goes to the starter batt?

Yes, feeding the house bank with the starter battery isolated by the dc to dc charger. The Balmar charge controller for the alternator allows me to set a custom curve to protect the alternator from overheating. To be honest, it doesn't need such a large capacity alternator, the previous owner relied on the alternator and generator for his power needs, while running multiple systems, I wanted to get away from that. I also have a wind generator I traded 6 cases of beer for, the previous owner installed almost 2000 watts of solar panels on his catamaran and didn't want the year old generator. I just need to find a place to mount it that won't throw shade on the panels.



You did take into account that LFPs don't want to be stored at 100% SOC?

Depending on how you set up your charge controllers the batteries don't go to 100%, more like 99%
.

Spec'ed to the wire or the batt's capacity?

All wiring set to spec, all the proper size and tinned marine wire, not cheap, but I sleep well at night. When I got the boat there were multiple connections to the original lead acid batteries with no fusing for protection. Multiple contractors who installed systems for the previous owner did it cheap and loose. Bothered me to no end. Connections were rerouted to main buss bars and jut a single connection to the batteries with an appropriately sized fuse for protection. I use ABYC standards as my guideline, but did ampacity calculations based on battery capacity and loads. Replaced any wiring that was suspect. The previous owner used welding cable in some places, which is more flexible and easier to run, but doesnt have an acceptable heat rating for the casing. It wouldn't pass insurance standards.

All in all, this sounds like a good solution!

I now own tools I never thought I'd need to own, like a hydraulic crimper for up to 0/2 cable, but it was cheaper than paying a contractor. The benfit is that I know the wiring on the boat in detail. I also have a wire tracing unit since I'm still pulling dead wiring out. I've probably pulled about a mile of dead wiring left by past contractors who installed new systems and never pulled out the old wiring prior to my ownership. I currently have the motor out and am pulling dead wiring in the engine/ generator compartment. Motor gos back in in May, so i've got some cold days working in the compartment. I have enough old wire to rewire a more modest vessel. All fun. Not.

[hzcruiser]

Originally Posted by lifeofreilly57

[...]Motor gos back in in May, so i've got some cold days working in the compartment. I have enough old wire to rewire a more modest vessel. All fun. Not.

Yes, the work never ends.. good luck!

[Pete7]

Originally Posted by SV Confianza

I would debate the assertion that it is unsafe given proper class t fusing, and actually should have mentioned that in my original response. However, i have been debating your thought of just ridding the starter bats as you suggest. Would make things much simpler.

Agreed, I don't think ABYC have used the word "forbidden", instead probably "not recommended" to directly parallel LFP and LA. Unfortunately the advisory recommendations are hidden behind a paywall so difficult to read for more than a fortnight of free use. The good news is they are only advisory and have little impact outside the US.

Also worth noting that most people are not directly paralleling FLA and LA because there is a BMS sitting between the chemistries managing the whole set up. Something that didn't exist when AGM and deep cycle were wired up in the past. The BMS is a bit like the your smart phone charger. If it fails you could have mains AC going directly into your iPhone or Samsung.