Battery voltage when running

[jetboater4life]

Three years ago I started keeping my boat on a lift and I've struggled to maintain my batteries since I don't have shore power other than a 2000 Watt generator (Yamaha brand of course) in my dock box. I installed a 10 watt solar panel with a 45 watt rated charge controller that doesn't seem to help much. I have a blue seas add a battery kit installed with two deca type 24 AGM batteries. I measured the voltage last time out with the ACR swtich off meaning both batteries were isolated and disconnected from all loads and got readings of around 12.25 Volts which is on the low side. When I turn the ACR switch to on and fire up both engines I got readings of 12.65 volts on each battery. That seems low since a typical car alternator will charge up close to 14volts. I don't have any specs on what the stators are supposed to charge too. Does anyone know? It appears they are only boosting the batteries 0.4Volts. What else can I do to debug this?

 

[WREKS]

The Electrical Specifications for my 2007 SX230 HO under Rectifier/Regulator Output Peak Voltage @3,500 r/min (unloaded) states 15.0 V.

 

[ripler]

From experience check the plugs that are connected to the rectifier/regulator to see if they are melted. I had a bad battery that caused my plugs to get hot and melt. If they look good then I would check each engine running by itself and check the voltage to see if 1 is putting out a lower voltage than the other. If one is reading low then you have a bad rectifier/regulator on that engine. You will then have to check to see if its your stator or it the rectifier/regulator, the easiest way to do this is to swap them and check the voltage. If you still have low voltage then your stator is bad.

 

[Seadeals]

I replaced the crummy depth gauge with a volt meter. I see just under 14.5 volts.

 

[jetboater4life]

Thanks. What I have learned is that it depends on RPMs. I think with my low batteries, 12.6 might not have been unreasonable at idle. I'm going to add some battery monitors too because the last three years on the lift without shore power have been a challenge given my usage pattern of using tsunami pumps to fill and drain bags and my drive to my surf spot is literally 30 seconds.

I also plan to check the plugs as ripler suggests as I have had low battery warnings from the boat in past years. In one case the battery was so low my perfect pass was flickering on and off.

 

[Cambo]

Check the solar panels when they are in sunlight see what type of voltage is coming out it’s very easy to blow a fuse when they are being hooked up or when pulling the batteries out . With all the cabling it’s easy to forget that they are still hot . You won’t get the blinding spark and distinct zap that most are probably familiar with that have accidentally touched battery connections . Mine was blown on my factory installed solar panels . Your voltage reading does seem low when the engine is running but as mentioned above idling vs running at higher rpm . These boats have stators not alternators stators are designed to run at higher rpm and don’t produce as much current that may be needed to charge a depleted battery same with a solar panel low amperage output.

 

[FLJetBoater]

Today, sitting at idle my tach volt gauge read 14.3V. seems like it would be sufficient for charging at that level?

 

[212s]

Today, sitting at idle my tach volt gauge read 14.3V. seems like it would be sufficient for charging at that level?

Idle speeds will charge the battery, but slowly. Amperage output increases up to 3000rpm and then it levels out above that. So if you're idling at 14.3v, your batteries are essentially 95%.

After floating for a while with the tunes pumping, I typically see the house drop from 12.7v to 12.5v or about 80% before starting the engines. Once running, voltage will climb quickly to 13 then 14 and within an hour they're back to 100% at 14.4v while running. Cut the engines ard both batteries are at 12.7v which is 100% fully charged. I don't need a battery charger during the weekends this year as we've done enough running around to keep them topped off. Over the winter they'll be on the smart charger, and next summer might need to use it some times as we'll be doing more anchoring and floating where the house won't get a full charge back to the dock.

 

[FLJetBoater]

Idle speeds will charge the battery, but slowly. Amperage output increases up to 3000rpm and then it levels out above that. So if you're idling at 14.3v, your batteries are essentially 95%.

After floating for a while with the tunes pumping, I typically see the house drop from 12.7v to 12.5v or about 80% before starting the engines. Once running, voltage will climb quickly to 13 then 14 and within an hour they're back to 100% at 14.4v while running. Cut the engines ard both batteries are at 12.7v which is 100% fully charged. I don't need a battery charger during the weekends this year as we've done enough running around to keep them topped off. Over the winter they'll be on the smart charger, and next summer might need to use it some times as we'll be doing more anchoring and floating where the house won't get a full charge back to the dock.

Yesterday after I flushed my engines I checked the battery reading after I turned them off. They were showing 13.3V. I don't have my amp installed yet but it seems that my batteries are being brought back to fully charged after basically every run on the water.

It will be interesting to see what they read today with the voltmeter after sitting overnight. I should be able to get a more solid reading.

Once I have my new batteries and amp, is it going to be better to let the engine charge the batteries from say, like 50% back up to 75% then maybe off for an hour then on the charger from 75% back up to 100%. Or should I just remove the DVSR, just leave the engine charging on the start battery, and only use the shore charger to bring them right from 50% to 100%? I guess what I'm asking is does the small incremental charges hurt it?
Say in a day, starts at 100. Stays at 100 while travelling...parked, drops to 90%, driving again charges back up to 100, parked, drops to 50, driving again charges up to 75, etc....Does that have an effect on the life on an AGM battery?

 

[212s]

Yesterday after I flushed my engines I checked the battery reading after I turned them off. They were showing 13.3V. I don't have my amp installed yet but it seems that my batteries are being brought back to fully charged after basically every run on the water.
It will be interesting to see what they read today with the voltmeter after sitting overnight. I should be able to get a more solid reading.

That 13.3v was a fresh off charge voltage and is not accurate. Batteries never really charge above 12.7v but in order to push them to fully recharged levels and de-sulfate the lead plates, the charge voltage needs to be a couple volts higher, hence 14.4v. Once the batteries cool, you should show an idle off load or resting voltage of 12.7v when fully charged (AGM is a tad higher at 12.8v).

As you noticed, without an amp, the engines are easily able to keep the batteries charged and quickly. I'm running a small digital 500w 4-ch amp and with some running around, I'm usually charged back to full by the time I return to the launch ramp, unless I'm really close. However my amp is very efficient and I'm not pounding music for 6 hours at a sandbar. And since this is a new boat this year, we've been using it much more so more engine running time. I expect next year will be more floating, but plenty of zipping around still. That's why I put a good smart charger in the boat now, ready for winter storage and usage next summer to keep the batteries in good shape.

Once I have my new batteries and amp, is it going to be better to let the engine charge the batteries from say, like 50% back up to 75% then maybe off for an hour then on the charger from 75% back up to 100%. Or should I just remove the DVSR, just leave the engine charging on the start battery, and only use the shore charger to bring them right from 50% to 100%? I guess what I'm asking is does the small incremental charges hurt it?
Say in a day, starts at 100. Stays at 100 while travelling...parked, drops to 90%, driving again charges back up to 100, parked, drops to 50, driving again charges up to 75, etc....Does that have an effect on the life on an AGM battery?

All lead-acid batteries should always be fully recharged as soon as possible, even AGM. Having said that, your scenario of charging for a while, then stopping for a bit, then charging some more, won't be too detrimental as long as you fully recharge with a smart charger that is suitable for AGM each day. AGM are more durable and can handle more and deeper discharges, but they still must be fully recharged every day or sulfation will occur and slowly reduce capacity. As long as you can get a full charge into it at the end of the day, you should be fine. I would leave the DVSR alone as it will still put some good juice into the battery when running, and then fully recharge when you park the boat.

 

[FLJetBoater]

That 13.3v was a fresh off charge voltage and is not accurate. Batteries never really charge above 12.7v but in order to push them to fully recharged levels and de-sulfate the lead plates, the charge voltage needs to be a couple volts higher, hence 14.4v. Once the batteries cool, you should show an idle off load or resting voltage of 12.7v when fully charged (AGM is a tad higher at 12.8v).

As you noticed, without an amp, the engines are easily able to keep the batteries charged and quickly. I'm running a small digital 500w 4-ch amp and with some running around, I'm usually charged back to full by the time I return to the launch ramp, unless I'm really close. However my amp is very efficient and I'm not pounding music for 6 hours at a sandbar. And since this is a new boat this year, we've been using it much more so more engine running time. I expect next year will be more floating, but plenty of zipping around still. That's why I put a good smart charger in the boat now, ready for winter storage and usage next summer to keep the batteries in good shape.

All lead-acid batteries should always be fully recharged as soon as possible, even AGM. Having said that, your scenario of charging for a while, then stopping for a bit, then charging some more, won't be too detrimental as long as you fully recharge with a smart charger that is suitable for AGM each day. AGM are more durable and can handle more and deeper discharges, but they still must be fully recharged every day or sulfation will occur and slowly reduce capacity. As long as you can get a full charge into it at the end of the day, you should be fine. I would leave the DVSR alone as it will still put some good juice into the battery when running, and then fully recharge when you park the boat.

Thanks! I’m planning to pick up a promariner 44021 20A 3-bank those seem to receive good reviews.