Testing out my jump starter…

[Ward H]

Consider the engine has a dumb alternator/regulator and just the normal Bat 1, Bat 2, Both, Off switch.
Engine starts and Alt starts pumping volts and amps.
Without a dead battery to absorb this energy, the alt is sending it to the jump pack.
What does that do to the jump pack?

From the jump pack’s perspective it’ll be connected to a voltage source providing about 14.3 V. That’s no different than being connected to a full battery on a charger.

Makes sense. I should have thought about that.

I'm kinda with @Scott T-Bird. I won't call it the dumbest idea but why do I want to have another piece of equipment to store on the boat and maintain.
I put my money in a dedicated charging battery isolated from the house bank. If it goes bad I can turn a switch and start from the house bank. It is tested everyone time I start the boat. Simple.

 

[Ward H]

This sounds contrary to most car mechanics that told me one way to check the alternator or battery for faults is to start the car and disconnect the negative terminal off the battery and if the car continues to run the alternator if functioning fine. If the car stalls and dies the alternator if faulty and needs either the diodes/regulator replaced and or entire alternator replaced. This should be about the same with the boat alternator although I’ve never done that. Usually just boost it with the jump starter and then remove it after it’s running.

I sure wouldn't do that on modern cars. The slightest arc/spark could do damage to the electronics/CPU.
On diesels it won't work because they don't require electric to run.

 

[dLj]

I'm kinda with @Scott T-Bird. I won't call it the dumbest idea but why do I want to have another piece of equipment to store on the boat and maintain.
I put my money in a dedicated charging battery isolated from the house bank. If it goes bad I can turn a switch and start from the house bank. It is tested everyone time I start the boat. Simple.

I carry a jump start battery pack on my boat. Not for jump starting my engine, although if need be I could use it for that. But rather as a portable 12V source that can be used for many trouble shooting problem solving techniques. I've also used it as an independent 12V source to run equipment temporarily when the ships 12V feed has stopped working for unknown reasons.

I've found it more useful than expected on my current trip.

dj

 

[BarryL]

Hey,

I disagree. I think a jump pack can be very useful.

Short Story:
A few years ago I was doing a multiday distance race (Spring OffSoundings). The boat owner and I are moving the boat from home port to the race area, about 55nm away (New London area). The weather cooperates and we sail all the way to the marina, near the race. The owner goes to start the engine for docking, and the engine won't turn over. I check and all three batteries are dead. No jump pack. Big problem. The owner calls tow boat US to arrange a tow into the marina. The tow boat us captain asks what is wrong, we tell him, he pulls along side and hands me a jump pack. I connect to the nearest dead battery and two minutes later the engine is running and we are able to tie up in a slip.

Longer version:
Once we were in the slip I started troubleshooting. The engine ran fine (mechanical fuel injection). Alternator belt was intact and the alt was turning. No power output from the alternator. All electrical connections appeared tight and clean. i saw there was an external regulator and it had a glowing red light. So we had no way to charge the batteries. Four crew were due to arrive the next morning (Friday) and we were supposed to race to Block Island that day, around Block on Saturday and then to return to Port Jeff Sunday. We talk to the marina we're at, it's close to 6:00PM and they are closing up. No time to get parts, new alternator, or anything like that. The marina offers to charge the batteries overnight. We decide to just charge all three boat batteries and the owner buys a jump pack. We can race but use minimal power.

Conclusion: After we finish racing we depart Block Island for the 12 hour return. There is no wind, the engine starts but all batteries are very slow. Not enough power to run the autopilot or the XM radio. So it's a boring motorboat ride home with each crew steering for 2 hours. I'm kind of hung over and not feeling great. After a few hours or motoring I'm down below looking for coffee. I see the bad voltage regulator with the glowing red light and I'm mad so I take my metal coffee cup and beat up on the voltage regulator. To my surprise the red light turns green and amps start coming out of the alternator. With autopilot on and tunes playing my mood improved.

The owner spent a decent amount of money having the regulator changed and some battery monitoring installed.

I carry one a jump pack on my boat. I've never needed it but I have loaned it to others on more than one occasion. My original jump back was a standard type large one. Last year I bought one of the small LION units. For under $100 I think it's very cheap insurance.

Barry

I think these portable jump starters are just the dumbest idea. If you are smart about maintaining your batteries, you will never need it. Don't bother testing it, you should never need it ...

 

[Stu Jackson]

1. With the batteries out of the loop the power will have no place to go.

2. This is like turning off the key before pulling the engine stop...

1. Quite true but ONLY when the engine is running. Which "batteries?" Assume you meant boat batteries, rather than the jump pack one.

2. Not necessarily and most importantly, It All Depends on How It's Wired. I have an external regulator with my alternator output wired to the house bank. I can turn off my 1-2-B switch and/or my cockpit key switch without damaging anything. The key switch turns off the regulator, the 1-2-B switch affects battery output only.

In discussing issues like this, generalities are not helpful and specificity may help folks better understand how things work.

 

[Scott T-Bird]

I'll concede, it does sound like a good option for a portable 12vdc power source. But, I still wouldn't carry one around just for the odd circumstance that 2 battery banks go dead simultaneously for some mysterious reason. I'm still trying to de-clutter my boat ... not add to the stuff that doesn't see the light of day. If I did have one (and I was given one many years ago), there's a better than even chance that I wouldn't even have it with me when it might be needed ... it would be in a storage cabinet somewhere. I'm trying not to be in the habit of carrying stuff around that isn't necessary. You can cite all the predicaments that folks have been in ... I'd still prefer to be more reliant on a dependable on-board electrical system than to carry a box around that I find essentially not very useful.

So, if you think it's great to have, just in case, for your auto and your boat, do you transfer it back and forth every time? I wouldn't. I'd get tired of that shit (and Sue would get tired of it even quicker than me! ). So, the car battery goes dead when the box is on your boat, or vice versa (or it's in a cabinet somewhere). Would you buy a duplicate and have 2 devices that are rarely useful (if ever)? Not me. Just my thoughts about it!

P.S. I don't really understand the reasoning behind the poster's idea to disconnect the battery cables ... which has stimulated all this talk about killing the diodes.

 

[Stu Jackson]

P.S. I don't really understand the reasoning behind the poster's idea to disconnect the battery cables ...

Could it be that by connecting the jump pack to an already dead boat battery it would drain the jump pack before the pack was used?

 

[Scott T-Bird]

Could it be that by connecting the jump pack to an already dead boat battery it would drain the jump pack before the pack was used?

I thought about it a little more ... I think he is only interested in testing the jump pack. He doesn't have dead batteries so the test would only be valid if he disconnects the batteries. This begs the question, why is a test even necessary? If it can jump a vehicle, why would there be any question about its ability to jump an itty bitty boat engine?

 

[Ken13559]

I used to carry NOCO GB40 Jump Starter. One got to remember to charge it.
So finally I gave up and got myself an Autowit Supercap II. Super capacitor. No need routine charging. It works great. Start the engine everytime I tested it. It even starts my son's diesel van.

 

[sailme88]

1. Quite true but ONLY when the engine is running. Which "batteries?" Assume you meant boat batteries, rather than the jump pack one.

2. Not necessarily and most importantly, It All Depends on How It's Wired. I have an external regulator with my alternator output wired to the house bank. I can turn off my 1-2-B switch and/or my cockpit key switch without damaging anything. The key switch turns off the regulator, the 1-2-B switch affects battery output only.

In discussing issues like this, generalities are not helpful and specificity may help folks better understand how things work.

Stu because not all boats are the same, generalities are actually the best way to proceed. Sounds like your set up is a bit different from many others. That is neither pro nor con. When general questions are asked, it is incumbent that the answers also be along the general lines.

That being said, do agree that if: Batteries are disconnected, a booster pack attached to the battery cables and the engine fired and said engine has a " typical " alternator set up with an intrinsic regulator, that there is potential for damage? Maybe the boat in question is set up like yours and no damage would happen, but the onus is on US to impart info that mights cause the asker to reassess his situation before doing something that hadn't been anticipated and thus prevent injury or damage.

 

[LaDonaMina]

Would the manufacturer of said jumper have designed into it a fail safe system to insure this type of use would be safe for both the vehicle and the jump/booster unit ?

I will admit I’ve started my 2018 Mustang with my booster without the battery hooked up and car started right up, unit checked the alternator system and I removed it and installed the battery with no ill effects to the car or the booster unit.

I have never tried it on the Sea Ray without the battery hooked up but use the booster when I haven’t used the boat in months. No issue so not sure where others are finding issues where there isn’t one.

 

[BarryL]

Hey,

I am not an electrical engineer but I sometimes play one when on boats.

When you have an external battery (jump pack) connected to your boat electrical system, or just engine, and you start the boat engine, the alternator will put out power and that power will go to the external battery / jump pack. If you remove the battery when the engine is running you could damage the alternator. The alternator doesn't know or care if the 'battery' that is taking the power is the boat engine battery, boat house battery, or jump pack battery. As long as the power can go to a battery it is fine.

I SUPPOSE that the jump pack could have in line diodes or something that prevented power from going INTO the jump pack but I have no idea why anyone would do such a thing. The jump pack needs to be charged. That can happen from external AC - DC power supply or from the alternator on a running engine.

As mentioned, the original poster wants to TEST his jump pack to see if it can start his diesel engine. To do that you must remove the boat batteries from the equation, otherwise you aren't testing anything. He wanted to know if he needs to remove both positive and negative cables. The answer is no, you only need to remove one. The boat batteries can't power the boat if EITHER the negative OR positive are leads are removed.

Barry

 

[dlochner]

I SUPPOSE that the jump pack could have in line diodes or something that prevented power from going INTO the jump pack but I have no idea why anyone would do such a thing. The jump pack needs to be charged. That can happen from external AC - DC power supply or from the alternator on a running engine.

Like Barry, I'm not an EE or even a certified marine electrician. With that said, there is one condition in which diodes in the jump pack might be beneficial.

If the jump pack is only partially charged, for arguments sake the voltage level is at 12.3 v and it is connected to a battery that is also partially charged, say at 12.4 v the battery will begin to discharge into the jump pack yielding 2 weak power sources. With blocking diodes in the circuit the little power remaining in the jump pack in combination with the battery might be enough to start the engine.

I think it was Ben Franklin who said, "An ounce of prevention is worth a pound of cure." In the case of preventing dead batteries the prevention is pretty straightforward, isolate the start/reserve batteries from the house batteries to prevent accidental discharge of both batteries and have a good battery monitoring system that indicates the state of charge and state of health.