Will I Do Damage without a Regulator ?

[Ericsn25Chespk]

I'm a novice at marine electrical systems and am beginning my journey to become more knowledgeable. Once I learn more I plan to make some updates to my boat's electrical system. In the meantime, I'm wondering if I can pick up two new batteries and use them for a few weekends without doing damage to them.

I just bought two Deka Marine Master Dual Purpose Deep Cycle Batteries (DP-24). I have a 25 foot sailboat with an inboard Volvo MD5A engine (9.9 hp). My specs say the alternator is 35A (420 W). I don't believe I have a regulator. We're thinking about taking a trip where we'd potentially run the engine for 4-5 hours (if there isn't enough wind) on two consecutive days. Given I don't have a regulator, would that much motoring do damage to my batteries?

Any advice would be appreciated
George

[BUBBABADBOYNO1]

It is built in in the alternator no problems.
Charlie Barnacle Bills brother.

[s/v Beth]

I just fried some very expensive batteries this way. I would suggest at least a voltmeter (can use a multimeter tool) to make sure your batteries don't go above about 14 volts while charging.
I would recommend a regulator for a long term solution.

[Blue Stocking]

Originally Posted by s/v Beth

I just fried some very expensive batteries this way. I would suggest at least a voltmeter (can use a multimeter tool) to make sure your batteries don't go above about 14 volts while charging.
I would recommend a regulator for a long term solution.

What happened Newt. Just curious. Your contribution here is always right on. Just wondering how this got by you.

[Ex-Calif]

The alternator is self regulating. On a smaller boat with a setup like this I usually recommend a cigarette lighter plug voltage monitor. You can get these at auto parts stores, target, walmart etc.

The voltage while motoring should read around 13.5-14v and with motor off around 12.5v.

What is bad for the batteries include high charge rates - >14v or so, draining them to dead and sometimes mixing of battery types.

What will kill your alternator is shutting of the battery switch while motoring. This is something new boaters sometimes don't understand.

The regulator receives a sense or feedback, from the system voltage. If the voltage is below the regulated voltage (~14v) the alternator cranks up the output. If the battery switch is turned off the alternator sense zero and goes into an over-output mode which can and will fry the alternator.

The other reason the alternator can go in overvoltage mode is if the sense line breaks or is corroded. Monitoring a voltmeter as mentioned above can alert you to something going wrong. Periodic inspection (annually?) of the sense line and cleaning the connection is also good preventive maintenance.

During haul out every year I remove and clean all the battery terminals, I disassemble and clean all the connections on the main switch and I remove and clean the connections on the alternator. The sea is a harsh environment.

[s/v Beth]

I see you want the story Blue Stocking. Okay,this is embarassing but I have a minute. When my Valiant was rewired, they attached the sensor part of the regulator to the engine battery bank, and the charging wires to the house bank. Did not figure that out till one day, while motoring down the Puget sound, I looked at my house bank and it was 17 plus volts! Apparently my alternator was giving full charge because in sensed the engine bank was down- basicly unregulated charging for my deep-cycle batteries. My batteries were starting to boil. In a panic I ran down and turned the battery switch to both banks (yep you guessed it- while we were still steaming) and managed to burn out the diodes on the alternator.
A very expensive lesson

[Ex-Calif]

Hi newt - sorry to drag out a tale of woe...

Shouldn't things have been OK on the "both" position in terms of the alternator? It still would have been a messed up situation but the system would be charging and sensing "both" banks.

Frying the alternator should have occurred on "house" or off because in either of those two settings there would be no sense to the regulator.

Just wondering if I am screwed up here somehow.

[Ericsn25Chespk]

Thank you everyone for the advice. I really appreciate it.

Ex-Calif- Is the cigarette lighter plug voltage monitor connected to the alternator? Would you "permanently" install the cigarette lighter plug voltage monitor? (as opposed to just periodically checking the voltage with a meter)?

[CSY Man]

I looked at my house bank and it was 17 plus volts!

That is good for the batteries:
It is called Equalization:

Battery Basics

[Ex-Calif]

This link should show you the item I am talking about. I wired in a cigarette plug on the bulkhead next to the vhf. I also run the ipod dock from the plug and it has a 3 amp inline fuse.

The best part is I can see the lights from the helm and have caught an alternator problem. We were motoring and the green light (full voltage) went off. Traced it to a corroded wire on the alternator.

Amazon.com: Equus 3721 Battery and Charging System Monitor: Automotive

.

[Ericsn25Chespk]

Thanks. Ah, so it's not directly connected to the alternator, but just part of the battery system. So I could plug this into our existing cigarette lighter onboard and it would tell me the battery and charging system voltage?

[Ex-Calif]

My DC bus is in on the bulkhead between the cabin and the v-berth. About 10 feet from the main switch where the bus supply comes from.

My monitor is plugged into a plug I installed next to the VHF on the same bulkhead. I can see it from the helm.

There may be a little voltage drop from the DC bus wiring run so I am not "strictly" measuring the batteries. I does give a good idea of the system (bus) voltage at any time.

[s/v Beth]

Sorry I am a little late with the reply. What Ex-Calif. said was true. I fried the diodes by changing the battery bank which were on separate banks to combined while the engine was running. In that instant the switch was changing over, all the current from my 100amp alternator had no place to go.
Before that, I had gone to my batteries and found them boiled over, bowed out and partially melted. Sorry, that is not equalization. And me in my infinite wisdom could see the fire danger- So with someone else at the helm and me not wanting to waste a second....I turned around and flipped the switch- thus burning out the alternator and stopping the fire danger
(this is not the recommended way to stop charging the batteries)