View Full Version : Accessory battery not getting charged by alternator

05-21-2011, 07:34 PM
I have an 08 x-2 and I recently upgrade some stereo components. I understand that I probably have too much running to one battery but I have a problem now and need to know how to fix it. Or at least where to start. I have the stock 6 channel jl am running the in boats and the stock sub. a 400 watt digital designs running two wetsounds pro-80 then a kicker 750.1 running a 12 inch sub. Before the kicker I had a smaller amp on a smaller sub. About 350 watts and everything seemed to be fine for an entire season.

So anyways here is the problem. We were going along the other day and the stereo starts cutting out like the battery is dead. Even while we had been running the boat. So I turned all of it off and let it charge up. But after the entire day of wakeboarding and running the boat the stereo did the same exact thing. The stereo components are all ran to the accessory battery. The starting battery is isolated. So I thought at first that the alternator was shot and it was a matter of time before the started battery drained. But I checked the volt meter and it was showing about 14.7 with the boat running and the about 12.3 when the boat was off so that would indicate the alternator works. So after that day I hooked up the accessory battery to a charger and charged it up overnight. Went back out on the water the next day and the stereo worked fine (until the battery drained). So the battery is good. I brought multimeter with me that day and checked the voltage at both batteries. At the starting battery the voltage was 14.8 or but then at the accessory battery the voltage was only showing 12.4 or so. So where do I start to figure out where the problem is. I was thinking possibly something in the battery switch under the back passenger seat because that is where the power coming from the alt switches up. None of the breakers are tripped it didnt seem but I may not have check it correctly.

Any suggestions would be great.

05-21-2011, 08:58 PM
I had the same problem with mine last year, on my 07' X45, It turned out one of my battery's was bad. Take it to an Auto Zone or something and they will test it properly. I also replaced my battery switch at the same time. (Blue Sea #6011) The knob on the switch wore out and it was spinning freely. Does yours have a VSR?

05-21-2011, 10:31 PM
Not sure was a vsr is but, I have had the battery tested and it is good, plus like I said when I charge it with a charger on shore it holds charge. I also have the blue sea switch 6011 and the knob is working fine. I feel like its a break in the line to the accessory battery at the switch somehow. I know the problem happened after I increased the load to the accessory battery with the new larger subwoofer amp. Maybe a breaker or a fuse? I'm not too familiar with this.

05-21-2011, 11:05 PM
The VSR (voltage sensitive relay) its that little grey box that connects to the back of your battery switch, I got a crash course on this last year by the way! It
has 2 red wires and a smaller black ground wire, In a nutshell it simply determines which battery has lower voltage and directs the charge to the less charged battery. There also is a red LED that comes on during normal use. I believe yours should have one of these but I know there is another system Mastercraft uses as well. Maybe its a bad ground or loose connection etc. Hopefully thats the system you have and sounds like what might be wrong. There is a guy on this forum named David with Earmark Marine who has helped me out that is very knowledgeable in this department, hopefully he'll see this. Good luck!

05-22-2011, 02:45 AM
Mine does have this relay. I just checked a little bit ago. I guess it could be the problem if it is stuck on only sending the charge to the one battery. I noticed it says something about 100 amps on there. Could it be possible that the new amp I added has put me over the amperage limit and caused a problem. I have removed the ground for the new amp for the time being to fix everything but it still seems like it wont charge the accessory battery. Could it be possible that the started battery is bad somehow and the relay is constantly directing power to it. Although the boat starts fine and it doesn't seem like it is losing any charge what so ever.

05-22-2011, 09:35 AM
If the batteries are checking out the VSR is going to be the key to this. You mentioned that you recently added a bunch of gear which probably included wiring to the battery. This is probably the most likely place to start as it worked before you made these changes. The thing I try to do is reduce the problem to the most basic configuration. In this case it would mean tracing all the wires from the charging circuit to ensure you have the VSR and battery cables from the switch connected correctly. From the description of your problem it would appear that you don't and that only one battery is getting charged.

I'm not sure of the manufacture of your VSR but if you can find out who it is you should be able to get a wiring diagram to ensure you have the cables connected correctly. These all work pretty much the same so you may be able to use the one on the Blue Seas site for their "add a battery" kit.


05-22-2011, 11:06 AM
There are a couple of issues to look into.
First, a bad battery may initially take a charge and read okay with a volt/multimeter which has no real current draw. How the voltage sags under load may be another story. So that is why load testing is essential to get an accurate assessment. You can also disconnect the battery entirely and see if it holds the full charge 48 hours later. A fully charged battery of reasonable good condition should read 12.6 to 12.7 volts at rest depending on the age. If that declines by much, say .5 volt after a couple of days, then I would replace it. Normal self-discharge is no more than several percent per month.
Second, ACR/VSRs have functional limitations in the context of big stereos. A fully depleted battery (considered empty at 10.5 volts) could represent an initial current draw of 15 to 30 amps depending on the battery(s)' amp/hour capacity. An endless number of batteries presents no load but discharged batteries are a real liability to your charging system. A large stereo system at full tilt (for example, a Class AB true 2000 watt system could draw 100 amps) has a considerable draw. The boat operations can be 20 amps draw or more depending on other DC accessories, lights, etc. Collectively you have exceeding the alternator output capacity. The alternator rating is not for continuous duty and is dependent on high rpm. So the ACR/VSR requires that it senses 13 volts or above for a specific duration or it will bounce open again. And that is exactly what will occur. Under certain conditions your stereo bank is completely off-line from the alternator. And, this results in deeper cycles which substantially shortens the longevity of even a deep cycle battery which has far greater capacity for higher quantities of shallower cycles.
As the audio system becomes more and more powerful the dominoes fall in different places requiring a different scheme. But, to start with you need batteries in good condition as overused batteries are unhealthy for your alternator. Don't keep them past their time. You need greater battery reserves to limit the depth of cycles. You will be more dependent on AC shore charging. You need a real big multibank, multiphase marine onboard charger...and not a tender/maintainer/trickle charger. Sometimes you have to kill the stereo for a while after a long play time at rest so that the ACR/VSR will combine and the charging system gets a chance to recharge the depleted bank. And, as the audio system increases in size you will need a more complex cascading scheme, more accurate voltage measurement abilities and
more disciplined management by the boat owner.
That's the basics.

Earmark Marine

05-22-2011, 03:06 PM
David thank you very much that was a great explanation. So judging on what I said happened in earlier posts do u think there is possibly any damage to the switch or the vsr that could be limiting me. I will replace the battery if needed and try test the voltage under a load as well. What's the best way to do that? Just test the voltage at the amp while music is turned up?

The thing that gets me is that even when I removed the new amp out of the system and left the stereo off and ran the boat for a good 3 more hours the stereo never charged up. Whereas before I would have the stereo bat die completely at the party cove and turn the boat opn and it would play just fine immediately.

05-22-2011, 06:20 PM
I figured out what the problem was I jiggled the wires that goes into the vsr from the accessory batteries post on the blue seas switch and I heard a change in the pitch of the engine like it was working harder and sure enough, I checked the voltage at the accessory battery and it was now at 13.9 whereas before it was 12.low. Thanks for all your help!

05-23-2011, 06:54 AM
Bingo! glad it worked out for you.

06-08-2011, 03:35 PM
I have similer problem as i've posted in other threads. So how about by passing vsr and not using it. Just parrellel batteries instead ? Maybe Vsr is bad ?