Battery/Charger issue

[drb1025]

I just replaced both starter batteries with new 8Ds. At the breaker panel, the battery selector switch can be in 1: Normal, 2: Both, or 3: Emergency House. I assume Normal allows each starter battery to start its respective engine and the Both setting combines the starter batteries in case one is weak. When the switch is at Normal, the voltage gradually declines, the lights dim, and the DC fridge shuts off due to lack of power, even with the battery charger on. I switch it to Both and the voltage jumps up, the lights brighten, and the fridge starts. There are at least two issues: the house is running off the starter, and the starter that runs the house is not charging. I am keeping the battery selector to Both for the time being, but need to identify why the Normal position is not functioning properly. Any ideas? I also have an inverter bank that I thought was running the DC house and a few AC circuits.

 

[Ski in NC]

Check the volts on each channel of the charger. It is possible for one channel to burn out, and the others to continue charging.

 

[Edelweiss]

Before you changed the batteries were you having the same problem? If not you may have a connection problem. Double check that you reconnected the battery charger to the positive terminal on that battery bank.

Very possible could be a defective charger, but also use a Volt Ohm Meter to check for charge voltage at the battery end as well. You want to see around 14 volts.

You may have a bad connection or broken wire between the charger and the battery. If you have a multi bank "smart charger" and there is a broken wire/bad connection, you may not see any charge voltage at the charger on that bank. Without a battery connected to it, some chargers won't supply charge voltage to that bank circuit.

You'll have to play with it a little bit and trouble shoot.

 

[boatpoker]

Please don't "play around with it". From your OP it is clear that you do not understand the system. "Playing" with three battery banks and an inverter can cause everything from severe corrosion to fire and electrocution.

If one battery will not take or hold a charge it could be boiled near dry of electrolyte. To continue to charge it is courting disaster. Are your fire extinguishers charged ?

Bite the bullet and hire a qualified marine electrician then watch over his shoulder, listen and learn.

 

[drb1025]

I checked the voltage and found that the 4D thruster battery was not being charged, both starters and generator batteries had full charges, and the house/inverter bank had full charge. Turns out the house 150 amp fuse was blown, wreaking havoc on the operations in Normal position, as described. Replaced fuse with 225 amp and all is good.

 

[Edelweiss]

Good Job!!

Boat maintenance and repair is not rocket science, but a continual learning experience. That skill and knowledge really comes in handy when you're out there hanging on the hook in the middle of nowhere and everything goes to heck in a hand basket !!

Any idea what popped your 150 master fuse?? I take it you tested all the connected circuits and none was shorted ??

Larry B,

 

[drb1025]

No short circuits. I didn't test the loads, but my guess is the fuse was too small for a thruster, windlass, and hydraulic crane.

 

[Baker]

I would imagine that the 150amp fuse in question has a reason for being 150amps and not 225amps????

 

[cafesport]

No short circuits. I didn't test the loads, but my guess is the fuse was too small for a thruster, windlass, and hydraulic crane.

Fuses should be sized to protect the wires not the equipment attached to them. If you blew a 150 amp fuse running some kind of variable load start with the battery. I=V/R.

Via iPad using Trawler

 

[drb1025]

The battery cables protected by the fuse are 4/0.

 

[dimer2]

4/0 cable is normally rated at 150amp >5 ft in length. Increasing the fuse amperage may not be wise....

 

[mbevins]

4/0 cable is normally rated at 150amp >5 ft in length. Increasing the fuse amperage may not be wise....

You might want to double check your chart. You're out just a bit

Sent from my Nexus 7 using Trawler

 

[dimer2]

You might want to double check your chart. You're out just a bit QUOTE]

Battery Cable Size

 

[psneeld]

You might want to double check your chart. You're out just a bit QUOTE]

Battery Cable Size

Yep that chart shows 4/0 handling WAY more than 150 amps....

yet that's more than it's rated ampacity...which seems really low/ridiculous to me... 4/0 195

Ampacity of Copper & Aluminum Wire

 

[boatpoker]

No short circuits. I didn't test the loads, but my guess is the fuse was too small for a thruster, windlass, and hydraulic crane.

Do you really run them all at the same time ?
I would have checked the current draw for item before going to a bigger fuse on a "guess".

 

[dimer2]

Yep that chart shows 4/0 handling WAY more than 150 amps....

yet that's more than it's rated ampacity...which seems really low/ridiculous to me... 4/0 195

Ampacity of Copper & Aluminum Wire

Ok, am I reading this wrong? I look at line 3 and 4 which shows from 100 to 190 amps max. I just finished running new cables so I guess at least I erred on the safe side?

 

[Edelweiss]

Look at his chart again.

Go down to line 6; 250 - 300 amps; and move across to 15 -20 ft; recommended cable is 4/0

Easily confused:
AWG 4 is around .20" diameter
AWG 0000 or 4/0 is about .46" diameter

Fusing at 225 amp would be fine and he is still well within standard for 4/0 cable.

 

[dimer2]

Aah I see the light said the blind man. Thank you gents.

 

[RickB]

What voltage drop rating are you guys using and what length?

A 2/0 cable is good for 65 feet of <10 percent drop and 20 feet for 3 percent drop at 200A.

Try this little gem: Circuit Wizard - Blue Sea Systems

 

[psneeld]

I have used many of the "wire sizing" tables out there....all of them have 4/0 carrying much more than 195 amps for shorter runs...

However the ampacity charts show less...so I'm not sure and will have to investigate further. Seems like battery cables can be way smaller due to the short nature of the draw...but for inverter draw, which can be for much longer...I'm not sure what's the best answer...maybe someone else know what source to refer to that takes something I don't know into account.

 

[RickB]

Insulation type, location, length, voltage, acceptable voltage drop; are all considerations.

 

[FF]

There is a huge difference in Ampacity between 4/0 and 0/4 wire.

Be sure of what you are looking at.

0/4 (usually good starter wire) wiring can be paralleled if required

The class T fuses come in sized for most 0/4 wiring.

 

[drb1025]

Thanks for the comments and suggestions. Due to the varied opinions on the fuse size, I decided to contact a marine electrician to look at the setup and see what he recommended. He confirmed the fuse size is satisfactory to protect the cabling. So as it is now wired, I have two 8Ds for starting, one also powers the windlass, and they can be combined if necessary. The separate inverter bank powers the house and the hydraulic crane. There are individual batteries for the genset and the thruster. I also installed a battery monitor on the house bank to measure the SOC. The starters, genset, and thruster batteries are charged by the Victron 40amp/alternators, while the house/inverter bank is charged by the Magnum 125amp charger.