DC electrical help needed!

R

RM

Member
Joined
Jan 1, 2000
RO Number
468
Messages
325
Purchased a 1998 37' Tiara last year and working out the kinks. When on the house battery bank (3 x 4D Lifelines only couple years old) I am getting low voltage indications from the KVH, 12 volt TV and chartplotter. They will all go off or not function properly, and per the KVH manual shows low voltage light comes under when under 10 volts.

So I checked the battery voltage at the batteries and getting 12.5+ volts and then 13.5+ with the charger on so not sure why the low voltage and where to look next. There is a 3 position voltage gauge on the electric panel and always shows 12+ volts.

Also the port voltage gauge at helm shows less than 12 volts until run for a significant period of time and then alternator seems to charge, but pretty sure this just goes to the starting bank for this motor, so even more confused as this bank shows good at batteries (2 x optima agms) as well.

Checked charger and seems to be putting good power to all 3 banks.

Anyone point me in the right direction??? I understand basic electrical so keep it relatively simple if you can. Trying not to call the electrician at $100+ per hour...yet.

Let me know what additional info I can provide also.

Thanks

Ryan
 
If you have good voltage at the batteries thn you need to look between the batteries and the panel. Open the panel and check voltage on the wire which brings power to the panel. Then check voltage at the breaker output for the kvh, tv, etc.

If the voltage is good at the panel, then the problem had to be in the wiring between the panel and the devices. Corrosion, loose wire, etc... Don't forget to check th negative side too.

If the voltage is low at the panel, then you need to check between the batteries and the panel, incl any fuse and the battery switches,
 
Check your main ground connections first. Then look at all your connections for those units. But otherwise you're going to have to start from the batteries and work your way up the line till you find the source of the voltage drop with a voltage meter.
 
Try the above suggestions 1st.
These are usually add on accessories the wire feeding these voltage sensitive systems could have too much voltage drop/ sag. It might be time to increase the + & - wire size from source to the devices or the DC sub panel feeds if there are any.
It sounds like you inherited these electrical issues?
Bill
 
Re port
Assuming that battery reads 12+ volts before startup some alternators require a bit of time to start charging if not run frequently. Increasing rpm usually starts them.
 
Take the wires off the batteries, and clean them with sand paper. Do the same with the leads to each of the distribution points.
 
Thanks all. Yes inherited the problem. I am thinking could be a ground issue behind the main panel. There are breakers that control all of the helm in the main panel as well so makes sense. The t. And kvh were piggy backed on existing breakers instead of having there own dedicated ones added which there is room for. Will try to take a closer look this week.
 
quote:
Originally posted by RM

Thanks all. Yes inherited the problem. I am thinking could be a ground issue behind the main panel. There are breakers that control all of the helm in the main panel as well so makes sense. The t. And kvh were piggy backed on existing breakers instead of having there own dedicated ones added which there is room for. Will try to take a closer look this week.

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What is the estimated round trip (+ & -) distances to each device from the main panel breaker and ground buss bar? I'm betting you have too small a gauge wire for the distance to these sensitive electronics. A 12.6VDC resting battery voltage is a fully charged wet cell battery. These devices should have less than a 3% voltage drop measured at the device from the source (the batteries).
I noticed you have AGM batteries the float voltage should generally be higher so it's possible you have weak house batteries. On the other hand with the charger on do you still have the same problem? If so then more than likely the DC device(s) wire gauge is too small for the load(s).
Bill
 
quote:
Originally posted by RM

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Just a thought.....does your problem occur when the boat is both on and off shore power ? Maybe somewhere along the line someone tied the AC and DC neutrals together .
 
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