Battery overcharging-maybe?

H

Hunkydory

New member
Last summer, while cruising down the Yukon River, the port 40 hp Honda motor battery voltage climbed to approximately 17v. It would normally show 14.4v. We didn't have a spare voltage regulator, so the trip had to be cut short at Dawson City, Yukon. Upon arriving back home, I purchased & then changed out the regulator & after, while at Lake Yellowstone & Powell, the battery shows 14.7v when topped off & motor still running, while the starboard if run independently would be 14.4v. Is the 14.7v reading within specs on a 1999 Honda 40 hp or to high?? My internet search came up inconclusive, though it did show with AGM batteries, 15v wouldn't do damage. I have a spare charge coil, but don't want to replace if not necessary. If I hadn't had to just change out the regulator due to its for sure overcharging, I likely would not be concerned about the voltage differences or 14.7v being to high.

Jay
 
Jay, The 14.7 should still be fine for the absorption phase of charging which you may be operating in much of the time while out on trips. We are frequently running between 65-90% charge throughout our shorter travels.

If you are running closer to the final float stage and above the 90% mark while motoring, you would be charging a bit high for finishing the AGMs and could be overcharging but "overcharging" does vary by model and also by temperature. If you knew your batteries were staying relatively cool (less than 80 degrees), I would not personally worry about it. But if I was running them in hot environments, or in a space that didn't cool well, I would worry a bit and count on earlier replacement.

One of the many reasons I moved our house batteries up under the v-berth, was the cooling affect of the water in those forward (uninsulated) compartments. I know those spaces will always stay cool while we are using the boat.

Greg
 
probably a stupid question

Are the battery wires and connections on battery and OB side - clean and tight ? that is no loose wires, nuts, bad connections or corrosion
 
Jay, Gregs advise is spot on. 14.7v may be a few points on the high side of "optimum" but for the amount of time they would be held at this absorption level I don't think it is cause for concern. Wet cells will loose water faster at this rate and they will heat up more. If a maintainer held your battery at this rate over the winter for example then it would be a problem.

Brent, there are no stupid questions here. I asked our harbor master a question one day and said it was a stupid one - she told me "if you are going out on a boat and have a concern about something - there are no stupid questions". You do have a valid point - bad connections will raise resistance which will raise voltages. Not sure if Jay is talking about 2 separate batteries or charging the same battery with 2 different outboards. If 1 battery has become slightly sulfated compared to a second battery it may show a higher charging voltage and it will come up faster than the good battery.

Regards, Rob
 
Greg, Brent & Rob, much thanks for your advise & suggestions.

The 14.4v reading from the starboard motor charging & the 14.7v from the port motor are both top end readings after the motors have been charging from a long run & I presume at the 90% battery charged level. These high level readings are the same, no matter how I combine the batteries (single, combined & then switched back & forth between the charging output of the two motors or both motors, charging one or both batteries) with the difference only being to which motor is providing the charge. Port 14.7v - starboard 14.4v.

Brent your poor connection idea did come into play, but I don't believe now a reason for the continuing different voltage readings. During the middle of my trouble shooting, I starting getting varying voltage readings to & from the house power distribution. This I finally tracked down to the negative house wire connection at the battery selection & connector switch. A short had formed in the wire where the wire attached to the ring connector. Following solving this, I made sure all other connections were good also. It was a tough one for me to solve, but very glad I wasn't in some remote location doing it.

The temperature of the batteries seem to be the same, no matter which of the motors are doing the charging, so at this point with the boating season now done, I will wait to next year to see if it is still a problem needing a solution or a variance within a acceptable range. My inboard Guest battery charger, that I use to keep the batteries tapped off during the winter, also tops the batteries at the 14.4v reading. I don't totally trust this charger, so only use it a couple days at a time, about once a month during the winter.

Other then the regulator/rectifier that I already changed, the charge coil is the only other component in the charging system of these motors. Is there a possibility it could cause this?

Jay
 
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