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Old 22-09-2011, 07:29   #1
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Jump Start Fail

Will an electrical guru help me understand this situation? We were at dock last weekend and accidentally turned off the shore power battery charger and ran the batteries down to 10.5 volts.

When I discovered that the batteries were down I thought it would be a good opportunity to pretend we were at sea with dead batteries and to try out my battery jumpstarter (like the one pictured below). I pushed the charge level button on the charger and it said it was fully charged, and then I connected it to my battery bank. The voltage on the system went up to something like 11 or 11 1/2 as read on my Xantrex Link 2000, but the engine would still not turn.

After I tried it and it didn't work the I disconnected the charger and it registered as having a low charge. It's only 6 months old, so I doubt it is a bad battery in the jump charger.

So had we been at sea we would have been screwed. The question is, when I use the jump starter am I supposed to connect it directly to the starter or something? Is my dead battery bank "absorbing" the power from the charger? What is my problem.

Battery bank is 4 31T Lifeline AGMs...each ~105 AmpHr. The charger says it has 900 cold cranking amps.

Any feedback will be appreciated.


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Old 22-09-2011, 08:14   #2
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Re: Jump Start with

As soon as you connect the jump starter to your bank it is charging the bank, and discharging the jump starter. You're putting something designed to barely charge one small car battery just enough to turn over the engine onto a large bank of batteries. And you're trying to start a diesel engine, they are harder to start than a gas engine and will require more cranking amps.

Do you have a starting battery or just the house bank? It would be better to hook it to the start bank, and buy a commercial version designed for the size battery and engine start requirements you have.

John
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Old 22-09-2011, 08:26   #3
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Re: Jump Start with

For just that reason we keep the genset starter battery completely separate from the rest of the system. If your main engine starter batteries go flat, start your genset and you should have enough power to go.
If you do not have a genset, you might do well to keep your starter batteries separate from the house bank.
No way is that silly little thing going to turn over one of Rudolf's beautiful diesels.
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Old 22-09-2011, 08:44   #4
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Re: Jump Start with

This is why I separated my Genset battery (or your ICE Bat) from the house bank. Since the only purpose of the ICE battery is to start it then there are no loads to drain it unless you need it. IF for some reason your ICE bat goes dead then you could run a set of jumpers to the house bank(12V) to get it started. Failing those 2 banks you then could use the jump starter right to the solenoid (battery side) and ground at the block disconnect the feed to the house bank so it doesn't back charge (draw from the jump starter) the house bank. This should allow you to start as usual with the key and eliminate any other power draws. As Lorenzo said this is exactly why we have a dedicated battery for this start.

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Old 22-09-2011, 08:44   #5
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I'm in the process of reworking our charging/battery system. I have been told by everyone (unanimous!) to isolate my start bank with an echo charger. Also to make sure my alternator went to the house bank. The echo charger will bleed off enough charge to take care of the start bank whether plugged in or under power. If my start bank was large I'd probably start directly from the jumper box rather than hooking it to the bank or isolate one battery to hook it to.

Nigel Calder has a good book I'd suggest: Boatowner's mechanical and electrical manual

That said I have one of these (different brand and stronger) too and would have made the same mistake if not for my current exercise. SC
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Old 22-09-2011, 09:04   #6
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Re: Jump Start with

The "Jumper" packs come in various sizes. The bigger the better. You boat will need a midsized or better. The JNC 950 will start anything you could possibly have in your 43.

Jump-N-Carry JNC950 Jump Starter Review
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Old 22-09-2011, 09:21   #7
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Re: Jump Start with

SailCruiser,
I also have the Echo Charger to install. It's use is to just maintain the starter battery with a small enough charge to maintain the battery but shut down if there is a problem with the house battery it's hooked to. I have a small control (parasitic) draw on the start battery (a gage) that has drawn the battery down in the past and want to eliminate the problem.

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Old 22-09-2011, 09:34   #8
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Re: Jump Start with

I think it's been said already, but to avoid any misunderstanding:

Those gadgets pour charge out of the on-board battery into your starting battery. It won't work if the dead battery you've hooked up to is very much larger than the on-board battery. They are designed to pump up a single car's starting battery, not a huge bank of deep-cycle batteries on a boat.

That's one problem. The second problem may be that the amps are in any case not enough to start a diesel engine.

The other sensible comment was that you really, really want a starting battery which is separated from your domestic batteries. There are about a thousand ways you can accidentally discharge your domestic batteries. You don't want to end up dead in the water because someone accidentally left the light on overnight in your heads compartment, just to name one possible example.

You can separate your start battery from your domestic batteries with an echo charger. A far better method is to have an entirely separate alternator. This can be achieved by adding a heavy-duty alternator to charge your domestic batteries, leaving the standard alternator to deal only with your starting battery.

I have separate alternators as part of the original spec of my boat. The main engine start battery lives next to the generator start battery. The main engine start battery has not only a separate alternator charging it, but also a separate battery charger. I can monitor its state of health from the nav table - it has a separate voltage meter.

I keep jumper cables on board just in case something goes wrong. I can then jump it from the generator start battery.

But if you keep your engine start battery entirely isolated from any electrical equipment other than your starter, you are very unlikely to have any trouble with it. It will never get more than 2% discharged and will always be fully charged. And that's exactly what you want, because starting your main engine can be a matter of life and death in some circumstances.
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Old 22-09-2011, 09:42   #9
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Re: Jump Start with

Still confused and always am about battery issues. The charger I have has 900 cranking amps and that is alot more than the West Marine 400 CA that I had before.

I guess the question is, could I have strated the engine by disconnecting some of the batteries or could I have gone straight to the starter (somehow?)
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Old 22-09-2011, 09:53   #10
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Re: Jump Start with

Dockhead...Great explanation. I think we are wired as one bank. I used at have battery bank A,B,Both but I thought now people like Nigel Calder say that is not the best way.

The echo charger on our Freedom charger goes to a V Berth battery for our Deck Washdown. I have thought I could always use that in a big emergency though it would be lots of trouble to move it etc.

I just looked up the exact charger I have and it is a Cobra CJIC 350. Here is the description:

Quote:
Need maximum power? The CJIC 350 jump starts most vehicle batteries including V8 engines with its 900W starting capacity and power UPS refrigerators and space heaters with its 400W AC power output, plus mobile portable devices with 12V and 5V USB outout.
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Old 22-09-2011, 10:04   #11
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Re: Jump Start with

In theory you could go to the starter with the key in the on or run position but it's not recommended for you or the motor to do so. That wet environment and electric thing. To see if the jumper pack you do have will work disconnect the feed from the batteries to the starter solenoid and connect the jumper pack to the solenoid and try to start the motor. If it does then your ok, if it doesn't get a bigger one. Jumpers don't like long cable runs (electricity in general doesn't), by running the jumper through the batteries and (assumption here) down the long cables to the motor you could have a voltage drop that didn't deliver the full punch to the solenoid. By going to the solenoid directly you give it the best shot. One other thing I just thought of, you may want to check the alternator that you can run without the batteries hooked up, some don't like that.

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Old 22-09-2011, 10:07   #12
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Re: Jump Start with

Quote:
Originally Posted by PamlicoTraveler View Post
Dockhead...Great explanation. I think we are wired as one bank. I used at have battery bank A,B,Both but I thought now people like Nigel Calder say that is not the best way.

The echo charger on our Freedom charger goes to a V Berth battery for our Deck Washdown. I have thought I could always use that in a big emergency though it would be lots of trouble to move it etc.

I just looked up the exact charger I have and it is a Cobra CJIC 350. Here is the description:
That unit has an internal battery of only 14Ah. The single engine start battery on my boat is 110Ah. I don't know what kind of engine you have on your boat, but that's sounds pretty small to be hoping to start a boat diesel with.

Nigel Calder -- and pretty much everyone else -- argues against splitting your domestic batteries into multiple banks. As far as I know, he does not argue against keeping your start battery separate. So if you have and "A, B, Both" switch which has been bypassed to permanently connect your starting with domestic batteries, I would reverse the modifications and restore that function. If I were you.

Or better yet, put in a separate heavy-duty alternator for your domestic batteries, and perhaps a separate shore power battery charger as well, and keep everything completely separate.

The Cobra gadget might be better left in your car.
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Old 22-09-2011, 11:05   #13
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Re: Jump Start with

Quote:
Originally Posted by PamlicoTraveler View Post
Battery bank is 4 31T Lifeline AGMs...each ~105 AmpHr. The charger says it has 900 cold cranking amps.
It doesn't have, nor does it say that it has, 900 CCA. It can supply 900 peak amps. That's totally different than CCA. It means it probably has about 450 amps of instant starting current. The "350" in the model number leads me to believe it really has 350 amps of instant starting current. Instant means that it should be enough to start an engine that uses a single starting battery that is too weak to start the engine on it's own. It can't supply that current for very long. That's why it's called a booster. It's only a small 14 ampere hour battery. Placing it across a bank of 4 discharged batteries is going to suck the life out of it.

Eric
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Old 22-09-2011, 11:35   #14
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Re: Jump Start with

what about a dry stored lead acid battery.
wrapped sealed in plastic etc... so no contamination.
Then in an emergency pour in the new electrolyte and the battery is ready to use.
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Old 22-09-2011, 11:51   #15
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Re: Jump Start with

On a pitching sailboat at 30d heal with waves breaking over the bow....

Steve in Solomons MD
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