jump starting and charging

[Home Cookin']

I read an authoritative-sounding article that said not to jump-start outboards, charge boat batteries while hooked up, or use the OB motor to charge dead batteries; all of this would hurt the regulator (Rectifier?). Didn't seem to make sense to me, although his explanations were convincing. Comments?

I know that with OB motors, they are tough and can handle a lot of shortcuts that are not recommended, but are OK in a pinch. I have read about a lot of things that theoretically can hurt a motor, only to find someone who has done it for years with no bad results. I suspect this may be one where the guy is right in the laboratory but canbe ignored on the water.

 

[Silvertip]

Re: jump starting and charging

Well sir, you might be surprised to know that battery switches and similar devices are installed on a huge number of boats with dual, triple and quad battery setups and they are charged by the engine alternator just fine. Having all of those batteries in parallel makes the alternator think it is charging one giant battery and it has no idea how many are actually there -- nor does it care. Those batteries also constitute the same thing as "jump starting" so that's another myth. There is one truth to the things you read and that's if the alternator needs to operate at its maximum capacity all the time it may eventually fail due to overheating. The alternator however, cannot output more current than it is designed for so if it's design limit is an output of 80 amps, it can output 80 amps. The only question is for "how long". It may never fail if the design was solid or it may fail sooner if it is not. By the way -- a stone dead battery will not generally accept a charge.

 

[5150abf]

Re: jump starting and charging

Running the motor with the battery disconnected is bad, it will blow the rectifier, but I don't see how jump starting could hurt the motor, maybe jumping dirrectly to the motor but as Silvertip said, the engine has no idea how many batteries are hooked to it all it wants is 12 volts.

I have heard people say alot of things and have found if it sounds goofy it usually is.

 

[Silvertip]

Re: jump starting and charging

The batteries are already connected "directly to the motor" so that's not an issue.

 

[ENSIGN]

Re: jump starting and charging

Using the charging system of any outboard or inbard to charge dead batterys is not a good idea,It creates excessive heat witch can damage electronics.

 

[Faztbullet]

Re: jump starting and charging

Battery switches are used all the time but must be used correctly. Rules are:
(1)Never turn to off while engine is running (2)Never switch between banks while engine running...
The older battery cd ignition systems(Merc mainly) if battery is disconnected while running it is usually instant death to rectifier and usually switchbox or trigger is damaged.
On Omc models that use the water cooled rectifiers, loose battery connections(use locknuts) ,improper use of battery switch,onboard chargers, can blow the rectifier and it can actually catch fire under the cowling!!!! BRP & CDI had a field seminar several years ago and #1 cause of blown rectifiers on fishing boats where onboard chargers. It is recommended that NO charger should be connected to starting battery as it is a 40 amp system and should not need (remote)charging if correct size battery is installed. In my Javlin bass boat I use the Interstate 27M-XHD for starting battery, has 1000 MCA and 180 reserve min's.can run areators/Dfinders all day and never is weak after 6-10 hrs fishing.

 

[Texasmark]

Re: jump starting and charging

Last time I purchased an after market alternator for a car (from Autozone) it had a note in the box that recommended that you ensure that the battery was charged (didn't say how much) prior to operating with their alternator. Maybe they said that so that you wouldn't connect the new alternator to a short circuit.....since it was in warranty.

Like the guys said, it's a matter of heat and when the OEM says that an OB stator is "A" 16 amp alternator, one would think they mean continuous duty....since they didn't specify otherwise.

Then they (OEM) follow it with a voltage/current limited regulator (for those with such a critter) whose job it is to ensure that the flow from the alternator remains within specs so as to not damage it, nor overcharge the battery once full.

So, as said, a 16 amp alternator/regulator is designed to put out 16 amps max. On a full load, [discharged battery(ies)] the voltage will be low but that will slowly rise as energy is pumped into the batteries and will continue to do so until the battery voltage reaches the max regulated output of the regulator (14.5 give or take volts). The more batteries, the more the energy transfer requirement and the longer it takes because 16 amps is all you can put out, and as the battery takes on a charge, the "resistance" the charger sees increases and the current starts dropping off. Course by that time (time the batteries are obtaining full charge) the current theoretically drops off to zero.

Removing the charging circuit and allowing time for the battery to stabilize (some say 24 hours), the voltage will return to 12.75 or thereabouts depending on electrolyte specific gravity and ambient temperature.

Connecting and disconnecting jump circuits and the like can present two problems: 1.) Reverse polarity hookup (usually accidental) that, with alternator circuits, will burn up (short out) the half of the rectifying circuit that is grounded. 2.) Voltage transients (sparks) that could exceed the PIV (inverse voltage rating) of the rectifiers and damage them also.

On disconnecting the engine from the battery when using external charging methods, the only problem I can see causing that requirement is that the regulator on the engine, if running, is trying to control what it sees to be the load. If the load is being fed from an external source, the engine's regular would/could not be able to perform it's designed function. Otherwise, with the engine off, it would be similar to problems, mentioned above, encountered with jump starting.

Case in point. I have an onboard charger with two 5a circuits....one would think separate. One can be hooked to the engine battery, and the other to a TM battery. If two TM batteries, then each battery gets it's charger and the engine gets none.

I have a 24v TM and don't need the 24v for my boat; 12 works fine. So when I recently replaced batteries, I replaced with one (half the price, half the weight) so I now only have 12v performance. I decided to put both onboard chargers to this one battery. The charger has a red light for low charge, a red+green for charge nearing full (reduced current) and green for full charge. With both chargers connected to one battery, the red light would never go out. But I could disconnect either and the one on the battery was green only. Proves my point mentioned above.

Years ago I had a service station attendant reverse the jumpers on my car so I have been through that fiasco. On my engine battery, I use a Schumacher 10A auto/man portable charger (just happened to be the one Autozone had for sale....but Schumacher is a name brand) and seldom have to charge it. But when I do, I hook her up and go about my business. Never a problem.

Well, that's what I know about it.

Mark