Not related to charging my TT batteries, but a question about the on-board 12V charging system in my Yamaha 2400 inverter generator. The other weekend I needed to fire up my new-to-me riding lawnmower and found that the battery was dead. I decided to try using the 12V charging system on the Yamaha gen for this, I had never used it before. I had my multimeter across the battery terminals while it was charging and I was surprised to see the voltage continue to rise. After around 30 minutes on the charger, the multimeter was showing over 16V. The battery started the lawn mower up just fine, but does that sound normal or safe for the on board 12V charger? I don't plan on ever using this charger except for unusual circumstances like this, but I still would like to know how it works. Thanks.

People mistakenly assume that a 12V battery puts out exactly 12V. Reality is they vary from around 11V (dead) to around 12.7 (fully charged). In addition, to push power into a nearly charged battery, you need a voltage difference so the charger will actually exceed that fully charged reading and the battery will show that higher voltage for a half hour or so after disconnecting. 16V is a bit on the high side. I think most alternators run around 14V. As long as you only use it occasionally and disconnect before overcharging, it shouldn't hurt anything. I wouldn't leave it hooked up for hours on a little lawn tractor battery.

I was expecting the charger to provide a regulated constant voltage in the high 12's to low 13's. Instead, the voltage reading across the terminals continued to rise.

Page 18 of the owner's manual has some interesting information.

Automotive type voltage regulators should NEVER be used to recover the charge of an almost DEAD battery. These are VOLTAGE REGULATORS ONLY!No method for regulating, tapering the charge rate, of the battery.A 90 AMP automotive/VR system will dump that FULL 90 amps, ~1000 WATTS, into a "dead" battery, boiling the electrolyte away fairly quickly.Most gensets have a maximum battery charge rate of ~2 amps, 24 watts, not enough to harm the battery even with an unregulated voltage charge rate of 16 volts.

2oldman wrote:Page 18 of the owner's manual has some interesting information.Consulting the manual would have been a great idea, I guess I figured it wouldn't be complicated enough to warrant it! Murphy's Law.I did try pushing the DC Protection button in but it wouldn't budge. So does anyone know if, when operated properly, the voltage reading should remain constant when using the generator's 12V charger?

Yamaha 2400 generator's on-board 12V charger | Good Sam Community

wwest
Explorer
May 20, 2015
Automotive type voltage regulators should NEVER be used to recover the charge of an almost DEAD battery. These are VOLTAGE REGULATORS ONLY!

No method for regulating, tapering the charge rate, of the battery.

A 90 AMP automotive/VR system will dump that FULL 90 amps, ~1000 WATTS, into a "dead" battery, boiling the electrolyte away fairly quickly.

Most gensets have a maximum battery charge rate of ~2 amps, 24 watts, not enough to harm the battery even with an unregulated voltage charge rate of 16 volts.
2oldman
Explorer II
May 20, 2015
Page 18 of the owner's manual has some interesting information.
ewarnerusa
Nomad
May 20, 2015
I was expecting the charger to provide a regulated constant voltage in the high 12's to low 13's. Instead, the voltage reading across the terminals continued to rise.
valhalla360
Navigator
May 20, 2015
People mistakenly assume that a 12V battery puts out exactly 12V. Reality is they vary from around 11V (dead) to around 12.7 (fully charged). In addition, to push power into a nearly charged battery, you need a voltage difference so the charger will actually exceed that fully charged reading and the battery will show that higher voltage for a half hour or so after disconnecting.

16V is a bit on the high side. I think most alternators run around 14V. As long as you only use it occasionally and disconnect before overcharging, it shouldn't hurt anything. I wouldn't leave it hooked up for hours on a little lawn tractor battery.

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Yamaha 2400 generator's on-board 12V charger

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