Get rid of the starting battery?????

[Pizzazz]

You need to have dual batteries. With a single battery the chance that you will not be able to start your engine one day increases dramatically.

The starting battery needs to be of minimum size to supply starting current and to be a true backup source. Imagine you deplete your main bank and you cannot start your engine? A sizeable starting battery (100AH) will give you at least a day to sort things out. A smaller starting battery will die after (say) 10 attempts of cranking. It usually happens at midnight. What would you do?

[smac999]

if you take your palm sized jump pack and attach it to a dead group 27 battery.

vrs taking it to a dead 700ah house bank. that is a big differance.

the group 27 might go from 7v to 12v. and start the motor and the house bank would probably go from 7v to 7.5v and not do a dam thing.

it would be an interesting test.

[skipmac]

Originally Posted by a64pilot

The Prius 12V battery is just there to boot the computer and bring the large traction battery online, it doesn’t start anything.

Did not know that. Thanks for the info. I only looked at it once and thought it looked pretty small to crank anything but figured the engine is pretty small so maybe it's enough.

Originally Posted by a64pilot

A Prius, just like all modern cars does have “dark current” though, small drains on the battery.

Cars and just about anything electronic these days is always sucking a little bit here and a little bit there. In a house it just adds to the power bill. In a car left sitting it will leave you dead.

Originally Posted by a64pilot

Be very, very careful if you ever jump a Prius, you can damage the inverter if your not careful, and that is thousands of dollars. Read the manual.

Again thanks. I do vaguely recall reading about this in the manual when we first bought the car but very good to keep in mind.

Originally Posted by a64pilot

On the Boat, I see a starting battery as silly, why have a separate battery to crank a baby Diesel when you have a monster bank that can do it with much less voltage drop.
I have two banks, one 440 AH the other 220 AH. I leave them combined as one bank. I can’t see the logic of a stand alone battery to start anything.

Having been stuck once a long way from anywhere with no way to start the engine because someone forgot to switch from both to 1 (can't imagine who that was) I really like having an independent, isolated, fool proof, no way to accidentally run it down battery to crank the engine.

[Olddan1943]

Originally Posted by smac999

if you take your palm sized jump pack and attach it to a dead group 27 battery.

vrs taking it to a dead 700ah house bank. that is a big differance.

the group 27 might go from 7v to 12v. and start the motor and the house bank would probably go from 7v to 7.5v and not do a dam thing.

it would be an interesting test.

The key is to start the generator and relax as the generator charges the start battery. Once the main engine is running, let the generator and or the main engine charge the house batteries.

[skipmac]

Originally Posted by Olddan1943

I sort of doubt the LI jump could start my Cummins 380 but I suspect it would start my Northerlights. Once the gen is started, it's just a matter of waiting until the battery charger does enough work to start the main engine.

You might be surprised. I looked at the specs on some of the heavy duty models. Some rated up to 4000 amp output and claim ability to start large engines including diesels.

Specs didn't give the amp hour capacity but state they can give up to 80 jump starts. Considering an easy start will only use a couple of amp hours I'm guessing maybe 150-200 amp hour capacity.

[daletournier]

I do this for the reasons you you are suggesting . The starter battery was 220amp/hr just sitting there, a complete waste imo. I combine the three now to give me 660amp/hr. And you can definitely start your engine with deep cycle house batteries, I've been doing this for years. The lithium jump start is there for the unlikely event I've drained the entire engine bank, it is a separate start battery, just not hardwired in. Because the bank is combined I can isolate a bad battery easily enough if need be, I have good solar and a generator to charge dead batteries if I was really stuck.
Why wouldn't the lithium start battery suffice? How is different from a dedicated starter battery that never gets used, just not wired in.

Regarding the comments of the lithium starter battery catching fire, this is no more likely to be (less) than the lead acid battery and associated fumes being an issue.

A64 got me thinking along this track.

[skipmac]

Originally Posted by daletournier

I do this for the reasons you you are suggesting . The starter battery was 220amp/hr just sitting there, a complete waste imo. I combine the three now to give me 660amp/hr. And you can definitely start your engine with deep cycle house batteries, I've been doing this for years. The lithium jump start is there for the unlikely event I've drained the entire engine bank, it is a separate start battery, just not hardwired in. Because the bank is combined I can isolate a bad battery easily enough if need be, I have good solar and a generator to charge dead batteries if I was really stuck.
Why wouldn't the lithium start battery suffice? How is different from a dedicated starter battery that never gets used, just not wired in.

Regarding the comments of the lithium starter battery catching fire, this is no more likely to be (less) than the lead acid battery and associated fumes being an issue.

A64 got me thinking along this track.

I also used deep cycle, house battery banks to start engines for years with no problem except, as I mentioned, when due to human error, I ran down the house banks and was left without engine.

I also now have solar and generator as well that will recharge me if left dead but I still want to have the capability to crank the engine immediately for one of those just in case situation, hence the lithium jumper battery.

Have been doing further reading and research and have found several models that will start even large V8 engines so capacity doesn't seem to be a limitation.

Now it comes down to what brand. Anyone have any recommendation for or against any specific models?

I also found a brand, EnergyFlo that says it has no batteries of any kind but doesn't mention how the power is stored. From the comment that it recharges in minutes I'm guessing it might be capacitor based but I have not heard that the problem fast self discharge of capacitors had been solved.

[john61ct]

The biggest OEMtools powerpak claims to start diesels. Also has a handy 19V output as well as 12V, USB and a flashlight.

[john61ct]

I also agree a dedicated starter batt is a waste, but you must design around not having one.

A big Main bank made up of 12V sub "blocks", could be 6V pairs, 4 x 3v, whatever.

Put an adjustable high-ampacity LVD on one (or more) of those blocks, call that Reserve bank. Big enough for cranking and all (separated out from House) essential safety, lights, navigation circuits.

In normal operating conditions, the closed LVD combines, full advantage of Peukert, start engines off the Main bank.

When House loads pull voltage below your setpoint, LVD opens, isolating Reserve so it is protected, always available for cranking.

Of course, large non-essential load circuits like entertainment should have their own LVD cutoffs set higher (earlier) refrigeration quite a bit lower, etc.

[Matt Johnson]

Yes, if starting primarily with the house bank, a lithium jump pack works great as an emergency bank. Just ask any Northern car dealership what they use on the lot during winter.... We could get about 10 diesel trucks fired up before needing to charge the tiny 800A lithium jump pack. Previously, we used a 1000cca LA jump pack (large/heavy) and could only do 2-3.

We did install a start battery since it does double duty as our hookah battery, but we also have two lithium jump packs... One does double duty as a charging source for cameras and computers off the boat and the other just sits close to the starter circuit's on/off switch (already has the jumper leads wired, but still needs to be plugged in and turned on to use). At under $100 each, why not?

Not for starting, but we can run our vhf and other things off our cordless power tool battery packs too in an emergency. Always good to have multiple back-ups aboard for some of these critically important items.

Matt

[S/V Alchemy]

Originally Posted by sailorchic34

I've used the house bank to start the engine for many years. I do have a G27 start battery, in the off chance that the house bank (4-GC2's) die together. But I've not used the G27 for starting in ages. I also have a extra G27 for windlass, so a backup to the backup.

Having a jump pack for emergency starting should be good enough, I would think.

Close to my setup. Basically, if the house bank (which is massive) fails massively, I have a start and a windlass Group 27 to work as an emergency house/start bank in "get me home" mode.

[john61ct]

Originally Posted by funjohnson

we can run our vhf and other things off our cordless power tool battery packs too in an emergency.

Interesting. Did you find ones that are in the 12V range?

I've been looking at creating a high-capacity portable bank system based on Ryobi' ONE+ series packs at 18-21V lithium at 4AH each module, bigger ones coming soon.

But for sensitive electronics I'd use a buck converter to step down to 14V output.

[roland stockham]

On the boat batt ( rather than cars). When you press the start button the batt drops to nominal 8v. If you regularly use a large house bank that can maintain 12v at 100+a you may burn out the starter. If the back is not big enough all you nav gear drops out.

[john61ct]

Starting isolation feature can take care of that.

But also note a big healthy bank won't drop V by much, 8V sounds crazy low to me.

And starters are fine with 13-15V all the time, most much higher, built very robust

[senormechanico]

Near the end of our 2 month vacation, we had been anchored for several days in Desolation Sound during last summer's wildfires.
The smoke got really bad, the solar was bust, the place got cold.
We finally decided to head home early as our LFP cells were down to 23%.
We held our breath when we cranked the 18 hp Volvo.

It cranked as fast as if the battery was completely full, and started normally.