Computerized Outboards/Onboard Chargers

[reelapeelin]

Has any one blown a computer on an outboard while charging the cranking battery with an onboard(or other) charger...marine tech saw my onboard charger(permanently) attached to cranking battery and 'bout busted a gut...concerned charger could malfunction, sending too much voltage to outboard, blowing it's brains out

[Robalobob]

I just purchased a new rig and the onboard charge is connected to my 3 troll motor batteries and also my cranking battery. Never seen this before. should I disconnect the one on the cranking battery?

[theoldwizard]

I can not imagine that power is being supplied to the computer with the key in the off position. At least in the automotive world, all computers are protected from over voltage up to about 28V.

[Mentalic]

I installed an isolation switch to disconnect the cranking battery from the boat because the engine was using 110ma (.11amp) while every system is turned off. I noticed this because every time I went to charge the cranking battery it really needed it, so I measured the current draw with all systems “off”. So yea the computer is not isolated from power even with the engine turned off. When I swith on the battery I hear something briefly click in the engine. I have a Yamaha F150 engine, yours may behave differently.

As far as a charger making the voltage rise to some dangerous level I think that to be very unlikely. Think of a battery as one serious big capacitor, its going to eat up power surges.

[reelapeelin]

Rabalobob...I'd tell you to install a battery switch btween the engine and cranking battery...it's what I'm gonna do for the remote possibility a surge, plus it'll reduce battery drainage ...

[Thom]

You guys are looking at the wrong end of the wire to discredit this notion. Not only would the computer be protected by its overvoltage capacity, and the key switch, and the battery switch, but also if the battery charger fails its not going to put out more power, its going to put out LESS power. While one might suffer some sort of melt-down catastrophic failure where a nasty dose of AC could get shot out of it (though to be absolutly honest I can not immagine how that would happen) but under no circumstance at all would it have a mighty increase in DC output.

Every now and then you'll hear about a run-away charger that 'cooked' someone's batterys, but that is something quite different. In that case what happens is the charger gets itself stuck on its high output rather than drop down in output voltage, as they should as the battery charges. But even when that happens, which is rare, they still only put out around 14.4 volts or so. While prolonged exposure to that sort of current (with sufficient amperage backing it up) the battery will fry after a while but it shouldn't ever hurt an outboard's computer.

Thom