Do I really need a separate starter battery

[CarinaPDX]

Originally Posted by Davidla

I also carry a jump pack as a reserve. Note my jump pack is Lithium and I would not try to start the engine with it. I would connect it to the start battery for five to ten minutes to put some charge into the start battery and then try to crank the engine.

This is not the recommended way to use a lithium jump starter. The total charge in the starter is fairly small (mine is about 6Ah) and would be depleted by leaving it hooked up to a discharged battery. The genius of the lithium jump starter is that it is able to put out a very high current, albeit for a relatively short time. So the recommended usage is to connect it to the battery and then immediately start the engine, not allowing time for the battery to deplete it. The starting power is quite amazing: mine turns over V-8 engines faster than with a new battery. Just last week I jump started a 350 cu.in. V-8 in an I/O across the dock from me - it took about 5 seconds of fast cranking.

Be careful when buying lithium jump starters as they are largely lithium batteries (commonly 18650's), and there are a lot of low quality cells on the market. Look for a reputable brand featuring quality branded cells. They are often rated for the engine sizes, gas and diesel, that they are intended to start. I think it is best to pay for the larger ones and have some safety margin. In my case the jump starter is for large V-8s and medium diesels IIRC, which is more than I should need for my car and boat but has come in handy for helping about a half dozen people in the last few years.

Greg

[Mickeyrouse]

Nah, you don’t need no stinkin’ separate start battery. And you could probably do without a bilge pump…or fire extinguisher….or first aid kit…or spares…or tools…or VHF…Just keep an eye on things.

[Dieseldude]

Mickeyrouse has a great equipment plan together... for those seeking disaster. The rest of us will sail with a good kit to keep ourselves out of trouble. If money is too tight for some basic gear, best to delay the trip long enough to make some cash for some essentials. I know, all sailors are are not idle rich who live of family trust funds. But if ya can't pay the piper, ya just can't dance.

[Don C L]

yeah I think he may have been bein' a bit sarcastic there... or is it sardonic? I always confuse the two... in any case I don't think he's bein' serious.

[goboatingnow]

Originally Posted by Mickeyrouse

Nah, you don’t need no stinkin’ separate start battery. And you could probably do without a bilge pump…or fire extinguisher….or first aid kit…or spares…or tools…or VHF…Just keep an eye on things.

Definitely sardonic but the last line is more sarcastic

[goboatingnow]

Originally Posted by Dieseldude

Mickeyrouse has a great equipment plan together... for those seeking disaster. The rest of us will sail with a good kit to keep ourselves out of trouble. If money is too tight for some basic gear, best to delay the trip long enough to make some cash for some essentials. I know, all sailors are are not idle rich who live of family trust funds. But if ya can't pay the piper, ya just can't dance.

The middle ground is many people can do several things but have to balance budget with the various options available. Not everything needs gold plating.

[donradcliffe]

Originally Posted by goboatingnow

I have two battery monitors. How does anyone “ wake up “ to a dead battery these days. Answer cause they are incompent or couldn’t be bothered to install a monitor.

In the last 20 , yes twenty years , I’ve never had an unexpected battery failure or unexpected dead battery situation. I can see batteries slowly failing etc. But not the “ wake up “ to a dead battery.

That’s not a failure sceanario that’s just incompetence quite frankly

These days a separate lithium jump start option is widely available so systems that don’t want a permanent starter battery can easily carry a backup. I do agree an alternative method should always be available but that does not excuse ending up with dead batteries

Its only been once in 15 years, but I woke at 0330 to the sound of the battery monitor alarm going off when a cell shorted in one of my gel batteries. The 500 ahr bank was down to 10.5 volts, but the good news was it was able to start the engine. The bad news was that the battery isolator tried to put the full alternator output into the shorted battery and burned itself up. It only took a minute to isolate the shorted battery because I had a 1-2-all switch, but it took until dawn to bypass the isolator and charge the remaining batteries.

There was absolutely no warning--the battery voltage was 12.8v when I went to bed. It happens.

[goboatingnow]

Originally Posted by donradcliffe

Its only been once in 15 years, but I woke at 0330 to the sound of the battery monitor alarm going off when a cell shorted in one of my gel batteries. The 500 ahr bank was down to 10.5 volts, but the good news was it was able to start the engine. The bad news was that the battery isolator tried to put the full alternator output into the shorted battery and burned itself up. It only took a minute to isolate the shorted battery because I had a 1-2-all switch, but it took until dawn to bypass the isolator and charge the remaining batteries.



There was absolutely no warning--the battery voltage was 12.8v when I went to bed. It happens.

My comment was in relation to the normal run of things.

Your issue is exactly why all of us recommend an alternative means of starting the engine.

There are a number of such alternative strategies.

[Zzmeyer]

Originally Posted by Mickeyrouse

Nah, you don’t need no stinkin’ separate start battery. And you could probably do without a bilge pump…or fire extinguisher….or first aid kit…or spares…or tools…or VHF…Just keep an eye on things.

A world cruiser once told me he didn't carry a life raft. He argued you probably will never use it, it probably won't work, and if you do need it and it works but don't have it, you won't miss it for very long.

[Don C L]

Well, the little old Volvos had hand cranks to start them too. My old Citroen car had one. Sure miss that car.

https://www.youtube.com/watch?v=H43SyaFxTms

[rslifkin]

Originally Posted by Don C L

Well, the little old Volvos had hand cranks to start them too. My old Citroen car had one. Sure miss that car.

The hand crank is a viable backup, but it requires extra features designed into the engine (such as the ability to decompress the cylinders). And in general, the maximum engine size where it's workable is fairly small, especially for diesels.

[Dieseldude]

Yes, the old time hand crank is probably the most reliable back up. I think that the life boats of every large vessel that I have seen have them, and I have had the experience of testing some. They do require a bit of skill, so if anyone has an engine so equipped, it is good to do some practice. For your own safety, do read the manufacturer's starting procedure for your engine before attempting.

[CaptainRivet]

Originally Posted by Zzmeyer

I started sailing when a sailboat had one battery. You woke up in the morning and the engine wouldn't start. Someone figured out to separate the engine start battery from the house bank. My new boat will have 900 amps (12.8 volts) lithium and 1200 watts solar with a Victron battery monitoring system. So why do I still need a separate starter battery? It is very unlikely I'll ever run the house bank down both because of its size and monitoring capabilities and if I do, wait a couple hours for the solar to recharge. While redundancy is always nice, the complexity of multiple battery types and their charging requirements seems to offset the advantage. It would give me more space, less weight and less complexity if I just skipped the starter battery. Help me with my idiocy.

What alternator setup do you have for your Lithium house?
High current with external regulator or standard one with external regulator or DC to DC charger via lead starter?

Very simple if your BMS can handle Peak 600A you can use your house as starter.
If not there are dedicated Lifepo4 drop in starter(!) batteries.
Or you get 6 LTO 40Ah Yinglong in series, no BMS and you are set and forget your starter battery forever... 30000cycles will outlast your boat.

[Ninedotsix]

Originally Posted by Zzmeyer

I started sailing when a sailboat had one battery. You woke up in the morning and the engine wouldn't start. Someone figured out to separate the engine start battery from the house bank. My new boat will have 900 amps (12.8 volts) lithium and 1200 watts solar with a Victron battery monitoring system. So why do I still need a separate starter battery? It is very unlikely I'll ever run the house bank down both because of its size and monitoring capabilities and if I do, wait a couple hours for the solar to recharge. While redundancy is always nice, the complexity of multiple battery types and their charging requirements seems to offset the advantage. It would give me more space, less weight and less complexity if I just skipped the starter battery. Help me with my idiocy.

Starting inrush currents are very high, since the torque required to turn a diesel is very high. This can run the battery output way up, almost to that of a short circuit current, if only instantaneously. This places much stress on the battery, which lead acid batteries have been designed to withstand.
I won't argue anything here, except to say that if you consult the technical support people at the lithium battery manufacturer of your lithium batteries, you may be admonished to use a fuse, to prevent cascading breakdown of a lithium battery.
In days of yore, fuses were never a part of cranking circuits, since the safety of getting started in a crowded seaway with heavy iron about preempted the safety provided by a fuse. Fuses prevent burning wires and exploding batteries, but can't stop a freighter with a fuse.
Take a chance on asking the lithium battery manufacturer, and please share what you are told.
The issue of breaking circuit continuity while under load is that the arc which can erupt may jump over to a grounded part, or opposite polarity part, and effectively short the whole battery bank. Also, the force of the arc can cause failure of the interrupting device. Use a vacuum breaker relay or other properly sized device with the interrupting rating needed to extinguish an arc, or withstand the forces that would cause the device to rupture.
Again, I won't debate this, but defer opinion to the manufacturers of the storage batteries and overcurrent protection devices.
Best Luck ~ 9.6

[CaptainRivet]

Originally Posted by Ninedotsix

Starting inrush currents are very high, since the torque required to turn a diesel is very high. This can run the battery output way up, almost to that of a short circuit current, if only instantaneously. This places much stress on the battery, which lead acid batteries have been designed to withstand.
I won't argue anything here, except to say that if you consult the technical support people at the lithium battery manufacturer of your lithium batteries, you may be admonished to use a fuse, to prevent cascading breakdown of a lithium battery.
In days of yore, fuses were never a part of cranking circuits, since the safety of getting started in a crowded seaway with heavy iron about preempted the safety provided by a fuse. Fuses prevent burning wires and exploding batteries, but can't stop a freighter with a fuse.
Take a chance on asking the lithium battery manufacturer, and please share what you are told.
The issue of breaking circuit continuity while under load is that the arc which can erupt may jump over to a grounded part, or opposite polarity part, and effectively short the whole battery bank. Also, the force of the arc can cause failure of the interrupting device. Use a vacuum breaker relay or other properly sized device with the interrupting rating needed to extinguish an arc, or withstand the forces that would cause the device to rupture.
Again, I won't debate this, but defer opinion to the manufacturers of the storage batteries and overcurrent protection devices.
Best Luck ~ 9.6

I just see that its debated to death and all excuses found but on the ones that actually done it, it works troublefree... My starter and anchor windlass never turned so fast with lead....

Your only problem to run starter of your lithium house is the BMS which needs to withstand 300A+your normal laod on the house. An average starter has 2000W on a 30-100hp engine in your sailboat and typical current draw 150-300A, with startup current doubles for some millisecs. Run the starter with a direct connection to the battery poles and you won't have a problem with the rest of the curcuit and no arcs.
I have one 840AH 12V lithium house and starter and eletrodacus BMS that doesn't carry any current. this combo can do 1600A shorterm, will turn every starter without any stress for the house at all....
Use a 40AH LTO battery with a DC-2-dc charger as emergency backup, will always turn the starter even at 9V depleted down. Better and 1000% more reliable than any lead, costs doubled one time but LTO lasts 30000 cycles while lead 300 if you are lucky.