Battery Issue - Suspect Bad Amp? Er, no. Battery.

[tdonoughue]

So.

I thought I had this issue traced down to a short, but I fixed the potential short and I still have the issue. The main symptom is a huge drop in battery voltage when I turn on the stereo system. Like, while on the charger (a Minn Kota Precision MK212), the voltage will go from 15.0 to 12.0 in a matter of 5 or 10 minutes. When I turn off the stereo, the battery pops back up to 15.0 in a matter of 20 or 30 seconds. Measurements are from the helm (both my fishfinder and my usb ports have voltmeters).

Today when I pulled the power from the pre-amp, the voltage stayed low. I don't think the Fusion head unit would be the issue... It is pretty new. That leaves the amp (which I bought used and several years ago). The crossover functions of the amp have gone bad, so now I am suspecting that there is an internal short in the amp.

Questions, then: a) Does that sound likely? Do amps go bad and draw like way too much power like that? Or is there something else I should be considering?

b) If I am new amp shopping... and don't want to spend $600+ on an amp, now that I have the pre-amp, do you think I can get away with a cheaper/lesser amp. I guess this would be an opportunity to amp up the tower speakers now, huh?

 

[FSH 210 Sport]

Hey TD,

Sorry you are having drama’s with the stereo system.. so not to sound like captain obvious here, can you eliminate the amp in question and just use the pre amp to power the stereo to see if that cures the voltage drop? Just try eliminating one device at a time and see if that cures your problem. I’m not exactly how amps work, but if there is a shunt / voltage reg in there it could have gone bad and is just shunting voltage to ground?

In my mind, the low grade short (not enough to blow fuses) you suspect in your amp can certainly be there... the thing to do would be to measure the current draw on the amp. I was actually shopping around for ammeters the other day for a boat project and found these inductive pick up ammeters. They refer to them as Hall effect...

Amazon.com: bayite DC 5-120V 100A Mini Digital Current Voltage Amp Meter Ammeter Gauge with Hall Effect Sensor Transformer : Automotive

Buy bayite DC 5-120V 100A Mini Digital Current Voltage Amp Meter Ammeter Gauge with Hall Effect Sensor Transformer: Ammeters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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What‘s nice about these ammeters is that you can simply disconnect the wired and slip this current transformer over the wire and get a reading. You could in theory just use a 9 volt battery to supply the power to the display since the display runs on 5-120 volts DC.

 

[tdonoughue]

Thanks, @FSH 210 Sport . Hadn't thought to connect the speakers directly to the pre-amp... That would take some rewiring (the preamp has RCA outs and the speakers are just the wires). But I may go pull the power cable from the amp, I guess and see what that does.

And the clamp meter is a good idea. I don't have one of those yet. I could stand to have a real one.... Lord knows I would use it. The little ammeter looks cool! I may get one of those just to put on the boat permanently for fun. With that, you could see your actual draw while floating and you could compute how long you can stay out...

 

[212s]

I concur, isolate each possible source one at a time and you'll find the problem. Amps can go bad and cause a current drain.

You won't be able to drive the speakers from the pre-amp, they're low voltage level and not designed for that. Just disconnect one device at a time to find the issue, and then deal with that.

 

[FSH 210 Sport]

Thanks, @FSH 210 Sport . Hadn't thought to connect the speakers directly to the pre-amp... That would take some rewiring (the preamp has RCA outs and the speakers are just the wires). But I may go pull the power cable from the amp, I guess and see what that does.

And the clamp meter is a good idea. I don't have one of those yet. I could stand to have a real one.... Lord knows I would use it. The little ammeter looks cool! I may get one of those just to put on the boat permanently for fun. With that, you could see your actual draw while floating and you could compute how long you can stay out...

Right on... I hope you find them useful.. they are pretty cheap so not a lot lost if it doesn’t work. However, in the reviews there are a few people with boats and one reviewer in particular had some great feed back from when he put them on his boat. I cannot understand in this day and age why all cars, boats, etc... don‘t have a volt meter and an ammeter. Having an ammeter is a great way to tell if you have problem. In fact, I think that one of the reviews was from a guy who found that he had a bad battery on his boat with this little meter, so that sounds like it paid for itself with that person.

My intent with these ammeters is to hook them to the cables coming from the engine alternators / stators and see how much power they are putting out at a given time since I can only find one reference as to how much these engines put out as far as charging current. My plan was to just mount them to a box with a couple of 9 volt batteries for the displays for a temp measuring device that doesn’t require installing a shunt type of ammeter. Then I can add 12 V load on the batteries until I see that there is no more output coming at a given load.

I want to add a Trollbridge charger to harvest any left over electrons to put a little charge on the trolling motor battery bank for extended periods of time off grid. I talked with Yamaha and the only answer they would give was that there was not much left over after running the boat and charging the house battery. When I talked with MinnKota about their alternator charger they said if I didn’t have at least a 35 amp alternator it wouldn’t work.. its their product and they are the ones in the know, but I somehow doubt that info is correct. I suspect what they really mean is you need 35 amps to make their alternator charger work at full output.

So the net net is, I’ll do a temp hook up and see how well I like them. There is a finite amount of dash space and I’d rather not have to drill holes that I don’t need. I did not look in depth, but I would think a single meter with a selectable display of two inputs or even a single meter that is small with two inputs would be great. I could probably rig up a little box that would ride on the dash for test purposes..


By the way, you never ever switch the “neutral“ ground. I know why the guy did it, to avoid any current flow through the current transformer aka Hall effect transducer.. but never switch a neutral / ground.

 

[Dumbassbass]

Isolating each device individually and checking with an clamp style amp meter would certainly be the easiest and fastest way - keep in mind MOST clamp style meters are for measuring AC only. Not a cheap tool but one you'll be glad to add to the arsenal is this:

$90
Klein Tools 400 Amp AC/DC Digital Clamp Meter, Auto-Ranging-CL390 - The Home Depot

Klein Tools 400 Amp AC/DC Digital Clamp Meter, TRMS Auto-Ranging CL390 - The Home Depot

Get an ideal and upgraded accessory to measure current accurately and quickly with the help of this Klein Tools AC or DC Digital Clamp Meter, Auto-Ranging.

www.homedepot.com

I would only power the devices for a brief second or so just long enough to get your reading with the meter clamped around the positive 12volt wire. Your amp and all other components should have a label stating the amp draw. My experience also is that just because a particular device is new or newer never means it shouldn't be suspect.

 

[tdonoughue]

Oddly, the JL manual does not have the amp draw as one of the specs. As it is a 600W amp, can I assume its max draw is supposed to be 50A? Fits with the 60A fuse they spec.. Fusion manual also doesn't have the draw... But it is 200W, so it should be 16.67A (though it has a 15A fuse). I'll check for a plate. Boat is up at the lake, so can't do that until tomorrow.

I ordered a very similar but cheaper meter off Amazon a bit ago. Should be here tomorrow and I will go up and do some more diagnosis.

 

[Dumbassbass]

Im curious of your battery(s) configuration and type? What all is running on each battery? What is/are the ages of the batteries ?

 

[AZMark]

I don’t know how the electrical system on your specific boat works, but is this all while plugged into a charger?
I’m not sure I’d definitely assume there was a problem based on that. Is there major drop when just running on the batteries or the engine?

 

[tdonoughue]

Standard 2-battery ACR setup. Start has both of the engines on it; house has the amp, pre-amp, head unit, fishfinder, VHF, and all of the other accessories (lights, etc.).

Batteries are flooded Costco specials (deep cycle starting), bought 10/2019. Just had them both out and load tested and they passed with flying colors.

And, yes, all of this was while it is plugged into the charger. Same thing happens with no charger, only faster drop (though I didn't try turning off the stereo last time I was out to see if it came back at all). But that is part of what concerns me. On a charger, I would think that I should be showing charging voltage the whole time (like 15v or so). But I am guessing something is pulling so much current the charger and the battery cannot keep up. Though then why something is not blowing a fuse is also beyond me...

Or I have some other issue that I have not yet found or thought of...

 

[Dumbassbass]

Just for ghits and shiggles, parallel another battery ie: 12vdc 100ah x 2 (positive to positive - negative to negative) = 12vdc 200ah see if you get the same result.

I'm not sure of the battery switch on your boat but many can accomplish this with the battery switches in a "jump" or "both" scenario so that house and starting are both utilized together.

 

[tdonoughue]

Yes, I have an emergency position on the battery switch that does that. I will try that, too. Thanks, good idea.

 

[tdonoughue]

Found this on the Fusion website (while looking for something else): True-Marine™ Stereo

One FAQ topic, and it is how much current does it draw. Nice. Normal listening for mine is 3A, muted 0.75A, and max 15A.

 

[FSH 210 Sport]

Isolating each device individually and checking with an clamp style amp meter would certainly be the easiest and fastest way - keep in mind MOST clamp style meters are for measuring AC only. Not a cheap tool but one you'll be glad to add to the arsenal is this:

$90
Klein Tools 400 Amp AC/DC Digital Clamp Meter, Auto-Ranging-CL390 - The Home Depot

Klein Tools 400 Amp AC/DC Digital Clamp Meter, TRMS Auto-Ranging CL390 - The Home Depot

Get an ideal and upgraded accessory to measure current accurately and quickly with the help of this Klein Tools AC or DC Digital Clamp Meter, Auto-Ranging.

www.homedepot.com

I would only power the devices for a brief second or so just long enough to get your reading with the meter clamped around the positive 12volt wire. Your amp and all other components should have a label stating the amp draw. My experience also is that just because a particular device is new or newer never means it shouldn't be suspect.

That looks like a damn fine meter! To me it seems like a bargain at that price, I have a fluke 77 that I got quite a few years ago that was way more expensive, had less features, and has been a great tool.

 

[Dumbassbass]

I needed a DC ammeter a year or so ago and saw a cheap one at Harbor for a c-note, wasn't impressed then saw the Klein a week or so later, best little meter I've owned. I prefer it over my spendy Fluke.

 

[tdonoughue]

Here is the one that is presently running its way to my door: https://smile.amazon.com/gp/product/B01N014USE/

Have other equipment from this manufacturer, which seems to work fine (basic cable tester stuff). So we will see. Do wish I had seen the Klein first, as it is no doubt a quality instrument. But this one should serve the present purposes...

 

[Dumbassbass]

I followed at that link, looks like it will do all you need and it has over 1000 great reviews! I'm in the telecommunication industry and tend to go with Klein or Fluke but that's based on 30+ years of habit too. Great Find!

 

[tdonoughue]

Meter got here, so when I finished smoking the salmon, went up to the boat and conducted extensive tests...

The amp was drawing 3-5A (depending on the music)(right on spec). Head unit was drawing .75A (right on spec). Pre-amp, .2A (didn't look up the spec, but that has to be in it...). Total draw from the house battery was in line with that... 4-7A.

So I turned everything off (other than the main boat switch). Charger plugged in. Voltage went up to 15.5V, then down to 13.7V (charger going to maintenance?) So I unplugged the charger and let the lights on the charger go out (drain the capacitors). 13.6V.

Turned on just the VHF. 13.5V. Just the fish finder. 13.4V. Head unit only. 13.2V. Added the pre-amp. 13.1V...then 13.0V. All off and it stayed there. Turned on the blower; voltage dropped to 12.2V, but when I turned off the blower it came right back up to 12.9V.

But then I noticed! The ACR led was on. That means it was combining the batteries. But the charger was not plugged in. I plugged in the charger. No change. Unplugged it (waited). No change. Finally I pulled the negative wire on it (and found the crimps were weak, so redid those--no change). Even when I turned off the boat completely and unplugged the charger, the ACR stayed lit. So I left the negative wire off the ACR, plugged in the charger again and turned the stereo on.

That started me at 13.1V, which dropped to 12.8V after one REM song. Recovered after the song to 12.9V. Turned on everything. Voltage dropped during the next song, but was back up to 12.7V at the end. Alan Parsons played, and at the end was at 12.9V (amp drawing 3.5A max). Dynamite: 6A amp draw, 12.7V at the end of the song. Yes played; up to 12.8V by mid song.

So I unplugged the charger. By the end of Yes, it was at 12.1V. Alabama played. 12.0V at the end. Smooth... 12.0V with periodic drops to 11.9V... Turned the stereo off and the battery recovered to 12.2V (VHF and fishfinder still on).

Mind you, not the ideal drop there, but given that I don't really know the battery's starting state (it may be that the ACR has been messing with the charger), the drop was much less and must less rapid than I have seen. I am now thinking that the ACR may have a short or something. I left the negative off and let the charger go to work.

I think my next step is to contact Blue Sea and see what they say... Maybe Minn Kota, too (charger mfgr).

Thoughts?

Edited to add: checked out the Blue Sea website. Their diag chart shows that in order to disconnect both sides of the ACR must be below 12.75V for 30 seconds. So maybe it is operating as designed?

 

[Dumbassbass]

It doesn't sound like you have an issue with the sound system. That ACR led would be lit if it sees voltage from the charger but not if the charger is off, you may have an issue there. Did you try with the emergency switch on (charger off) or jumped and did you try to bypass the ACR? I know you said you load tested the batteries but have you checked specific gravity with a hydrometer in each cell? Or do you get the same result if you swapped batteries?

 

[tdonoughue]

That is what I am thinking. Sound system looks clean from this.

I did combine the batteries. Same result... Basically nothing noticeable. Didn't swap them. Didn't do the specific gravity. Should do that.

I did figure out as well that the charger I have is a 6A charger (per bank). So not surprising that it can't keep up--but it is surprising it can't keep up a lot more than it is. But now I am suspecting the ACR. Even pulled the parallel switch just to make sure something wasn't shorting there (it wasn't).