Start engine with Li housebank!?

[Opel]

Hello group,
anybody does start the engine(s) with his Li housebank?
If so, what's there experience??
Or is this not advisable / possible ?

Thank you

Jo

[Tupaia]

I am interested in this too. I have 2 identical house banks and no start batteries.
It seems that Li is capable of supplying the required cranking amps especially for relatively small engines. The problems revolve around the BMS cut out voltage. Over cranking to the point where this is reached will render the entire bank shut off. I personally don't see this as being any different than draining an AGM bank. I simply start the other engine and cross connect to the drained bank. I see this as a solution that excludes the need for additional LA start batteries that impact on any possible weight savings by changing to Li. Alternator regulators obvious need to be Li compatible. Also the max draw current on the BMS(s) itself has to be in excess of the starting current if it is to avoid being damaged.


There are specific Li start batteries used for motorcycles and race cars so the chemistry itself is up to the task.


It would be great to have anyone more knowledgeable chip in.

[Cheyne]

Dakota Lithium has come out with LiFePO4 batteries that are dual purpose.

https://dakotalithium.com/product/da...cycle-battery/

[Na Mara]

A 900W starter motor will require 75A at 12V once turning but can draw up to about 4 times that as inrush current on start up. My 3 paralleled 200Ah LFP batteries are all fused at 150A and so cumulatively are fused to allow 450A, which is about 50% over any anticipated current the starter might draw. The external BMS allows up to 500A from the bank. Thus in theory there should be absolutely no problem having my LFP bank start the engine assuming that all cabling is correctly sized (its oversized) and the alternator has an LFP adapted regulator (which it does). The starter´s peak current draw is no worse than my inverter´s and that doesn´t blow anything.

Basically, as long as the lithium system is dimensioned for it, it should be able to supply the starter with all the power it needs.

Myself, I am wondering about doing away with a separate AGM starter all together (or rather having it as an offline, in emergencies only, backup). There seems to be a short circuit between my banks that I cannot seem to source (a battery protector is preventing any damage but it wont allow the LFP bank to connect with the short there.). The easiest fix is just to take the AGM battery entirely out of the system and just have it sitting as a spare. Then the only voltage source in the system is the LFP´s So I have my own reasons for considering this. I also like the elegance and simplicity of it. Of course, if the BMS trips out the LFP bank then I would be screwed without a bank up hence why Im keeping the AGM as a reserve that can be coupled in at need.

[wingssail]

Originally Posted by Na Mara

A 900W starter motor will require 75A at 12V once turning but can draw up to about 4 times that as inrush current on start up. My 3 paralleled 200Ah LFP batteries are all fused at 150A and so cumulatively are fused to allow 450A, which is about 50% over any anticipated current the starter might draw. The external BMS allows up to 500A from the bank. Thus in theory there should be absolutely no problem having my LFP bank start the engine assuming that all cabling is correctly sized (its oversized) and the alternator has an LFP adapted regulator (which it does). The starter´s peak current draw is no worse than my inverter´s and that doesn´t blow anything.

Basically, as long as the lithium system is dimensioned for it, it should be able to supply the starter with all the power it needs.

Myself, I am wondering about doing away with a separate AGM starter all together (or rather having it as an offline, in emergencies only, backup). There seems to be a short circuit between my banks that I cannot seem to source (a battery protector is preventing any damage but it wont allow the LFP bank to connect with the short there.). The easiest fix is just to take the AGM battery entirely out of the system and just have it sitting as a spare. Then the only voltage source in the system is the LFP´s So I have my own reasons for considering this. I also like the elegance and simplicity of it. Of course, if the BMS trips out the LFP bank then I would be screwed without a bank up hence why Im keeping the AGM as a reserve that can be coupled in at need.

Na Mara, to me this is a cautionary tale we all should pay attention to: You have apparently a properly installed set-up with all the right pieces, yet you have a problem which you have been unable to diagnose, and it presents a handicap to your use of your system.

All electronics are subject to failure, and when we look at the wiring diagrams that are being shown on this forum we see dozens of devices with electronics in them. Are we so sure that some of them won't at some time fail? And if they do how easy will it be to diagnose and solve the problem. Also, how many spares will we have to carry?

I'll use the example I've used before: When you are anchored in a remote place in a third world country and one morning your gran-daughter wakes you up and says, "Granpops, my phone won't charge." What do you do?Where do you start?

Some members here are ultra confident that this scene will never happen, or it does they say, "If it's broke, just toss it out and put in a new one." But how do we know which one is causing the problem?

Maybe most boaters are smarter than I am, but I sometimes have trouble diagnosing my very simple FLA-Alternator-Regulator system. And I had an opportunity to see this actually happen. A new catamaran came into our marina with a professionally installed 9KW Integral charging system, a huge 48 volt LifePO4 battery bank, tons of solar, and every bell and whistle possible, installed by Victon staff themselves in Europe. This was a smart and successful guy and he was proud of his system. I asked him, "If this breaks, how do you fix it?" He said, "I call Victron."

Well, it broke. The system bogged down his engine and he could not get up to cruising speed. The single 4x6" display on the system didn't give him a clue. He called Victron. They didn't know. They hired a local electrician who came to the boat. He didn't know. Two weeks later the guy was still in a quandary, problem not solved. But the next day he was gone. I don't know what was done or how it was resolved, if it was or where he even went.

Now this is not Papua New Guinea. When this happens out there the guy will be in deep do do in my opinion.

So I think that we need to remember that serviceability and problem diagnosis is important, and I don't think it is there yet. Maybe we need OBD-II systems for boats, but then I guess we'd need common installations, not custom ones for each boat.

I'm keeping my system simple for now.

[Tupaia]

Originally Posted by wingssail

All electronics are subject to failure,



SNIP


I'm keeping my system simple for now.

One word of caution - LIGHTNING

[wholybee]

Originally Posted by wingssail

Na Mara, to me this is a cautionary tale we all should pay attention to: You have apparently a properly installed set-up with all the right pieces, yet you have a problem which you have been unable to diagnose, and it presents a handicap to your use of your system.

All electronics are subject to failure, and when we look at the wiring diagrams that are being shown on this forum we see dozens of devices with electronics in them. Are we so sure that some of them won't at some time fail? And if they do how easy will it be to diagnose and solve the problem. Also, how many spares will we have to carry?

I'll use the example I've used before: When you are anchored in a remote place in a third world country and one morning your gran-daughter wakes you up and says, "Granpops, my phone won't charge." What do you do?Where do you start?

Some members here are ultra confident that this scene will never happen, or it does they say, "If it's broke, just toss it out and put in a new one." But how do we know which one is causing the problem?

Maybe most boaters are smarter than I am, but I sometimes have trouble diagnosing my very simple FLA-Alternator-Regulator system. And I had an opportunity to see this actually happen. A new catamaran came into our marina with a professionally installed 9KW Integral charging system, a huge 48 volt LifePO4 battery bank, tons of solar, and every bell and whistle possible, installed by Victon staff themselves in Europe. This was a smart and successful guy and he was proud of his system. I asked him, "If this breaks, how do you fix it?" He said, "I call Victron."

Well, it broke. The system bogged down his engine and he could not get up to cruising speed. The single 4x6" display on the system didn't give him a clue. He called Victron. They didn't know. They hired a local electrician who came to the boat. He didn't know. Two weeks later the guy was still in a quandary, problem not solved. But the next day he was gone. I don't know what was done or how it was resolved, if it was or where he even went.

Now this is not Papua New Guinea. When this happens out there the guy will be in deep do do in my opinion.

So I think that we need to remember that serviceability and problem diagnosis is important, and I don't think it is there yet. Maybe we need OBD-II systems for boats, but then I guess we'd need common installations, not custom ones for each boat.

I'm keeping my system simple for now.

This has nothing to do with LiFePO4. In my travels, I met again and again boaters who had no idea how the electronics on their boat work, and inevitably something broke, and no one local could figure it out. LFP installations can be (nearly) as simple as you want, to very complex. So can Flooded batteries, chart plotter installations, i've even helped diagnose fuel system issues that were a head scratcher with a dozen valves for switching filters, 3 lift pumps, a transfer pump, etc, and an owner that knew nothing about what any of it did. Fortunately for him, because I was there all he had to do was turn some valves instead of shipping a new pump to Costa Rica.

An LFP installation that is more simple than complex, will have fewer issues and be easier to diagnose than an FLA system. Just determining state of charge and how degraded an FLA battery is, is beyond the ability of most boat owners, and that is the minimum understanding you should have. But with LFP, SOC is super simple to determine.

Many of the diagrams on this forum are complex, and unfortunately I think that scares people away.

To the original question. There is no issue with an LFP battery starting an engine. There is an issue with low cost BMS's starting an engine. So, most drop ins are ruled out. A few companies (Dakota as mentioned) support it, but look at the specs. 1000A for 2 seconds, or 300A for 10 seconds. Thats fine as long as your engine starts quickly.

But any LFP with any BMS that uses an external contactor would have no trouble at all. I know of several boats that do this, even giving up a secondary emergency battery because LFP is so darn reliable compared to LA.

[skipperpete]

Thanks Wingssail for one of the most thoughtful and helpful responses I’ve ever read on this Cruisers forum......Touchè.

[hjohnson]

The thing that I would be worried about is welding the solenoid. On my 27’ sailboat, I just run a cheap Marine Start battery (I think it was $90?) that only powers the engine, and is continuously kept in float by an Orion DC to DC. It’s cheap and reliable.

[newhaul]

Originally Posted by Opel

Hello group,
anybody does start the engine(s) with his Li housebank?
If so, what's there experience??
Or is this not advisable / possible ?

Thank you

Jo

If you want lifepo4 starting get an LFP starting battery to do the job.
Recient info from ABYC says you have to have two separate batteries if house is LFP you need a separate battery to keep critical systems running . Chemistry of backup battery can be lead or LFP.

[T1 Terry]

I have been using my LYP house battery to start my 4 cyl diesel engine in my motorhome for around 10 yrs with few problems. Once we decided to have a cup of coffee each before starting the motor and heading off after 3 days or rain .... should have looked at the Victron BMV first ..... so we had to wait for the sun to come out for an hr before there was enough in the battery. We designed a fix into this by holding 5% capacity in reserve using the Victron BMV relay function and an over ride switch so the last 5% was available for the starter and glow plugs.
I even start my 680 cu in 6 cyl truck engine using 4 a 100Ah second hand Winston LYP cells, they no longer had the range capacity to be electric vehicle batteries, but they are still fine for starter batteries and house batteries.

Quality Li cells and a properly thought out battery build and battery management results in virtually no limit to the peak current draw. A 400Ah battery using 4 x 100Ah cells in parallel x 4 sets in series can deliver 1200 amps for around 15 mins, the cables and starter would have melted long before that.

But ...... if you are using a DC to DC charger between the start battery and the house battery, you need somewhere for the alternator to feed any current still being produced if the BMS wants to cut the charging. It also removes the requirement for a rather technical set up to get the alternator protected from the lithium battery, the continuous heavy drain and sudden charging cut can do real damage to the alternator and anything connected to that part of the circuit due to the sudden voltage spikes.
Easier to add a small cheap lead acid battery at the motor end and switch the lithium house battery to a direct connection for starting, then drop the lithium battery link back to the DC to DC charger/s to act as the cushion between the two power systems.

T1 Terry