Community Forums

FranzUgan · 04-17-2021, 02:36 PM

Hi guys, been reading a lot and can't seem to find the info I'm looking for.
I have a started battery and an aux battery. Both are in the engine bay. The 2 battery positives are connected together through a solenoid to isolate the 2 batteries when vehicle is off. Both batteries negatives are going to chassis and engine block.
I wired the shunt on the aux battery between the battery negative post and the chassis ground. No other connection on the battery negative post. All other connections are done on the shunt terminal thar goes to the chassis.
I cannot seem to get a proper reading from the monitor. Aux battery is charged at 100% and after various hours with the fridge running and the engine on the monitor will show a gradual decrease and eventually read 0% but battery has plenty of charge in it and reading 12.6v from same monitor.
Have I wired something wrong or I just got a defective unit?
Thanks
h

Winterbagoal · 04-17-2021, 02:57 PM

Quote:

Originally Posted by FranzUgan

Hi guys, been reading a lot and can't seem to find the info I'm looking for.
I have a started battery and an aux battery. Both are in the engine bay. The 2 battery positives are connected together through a solenoid to isolate the 2 batteries when vehicle is off. Both batteries negatives are going to chassis and engine block.
I wired the shunt on the aux battery between the battery negative post and the chassis ground. No other connection on the battery negative post. All other connections are done on the shunt terminal thar goes to the chassis.
I cannot seem to get a proper reading from the monitor. Aux battery is charged at 100% and after various hours with the fridge running and the engine on the monitor will show a gradual decrease and eventually read 0% but battery has plenty of charge in it and reading 12.6v from same monitor.
Have I wired something wrong or I just got a defective unit?
Thanks
h

Maybe the monitor isn't zeroed (or 100%) correctly?

twinboat · 04-17-2021, 03:14 PM

With the engine running, and charging, the monitor shouldn't go down at all.

Are you reading the AH numbers or watching a level indicator of some sort.

Some cheap monitors read AH but don't don't say if they are in or out. Once it gets down to 0, does it start up again ?

FranzUgan · 04-17-2021, 03:29 PM

I zero the monitor manually to 100% when I've fully charged the battery with a wall charger.

It shows the actual amps in and out. With both the engine and the engel running it almost always shows negative amps.
Once it goes down to zero it stays there.

Below is the shunt and monitor I'm using

TandW · 04-17-2021, 03:33 PM

Perhaps you miswired the monitor wire and charging diode wires. Did you take pictures before you started in on your project?

FranzUgan · 04-17-2021, 03:50 PM

Quote:

Originally Posted by TandW

Perhaps you miswired the monitor wire and charging diode wires. Did you take pictures before you started in on your project?

Don't really understand what I might have miswired. The monitor is already wired from the box and plugs in the only socket on the shunt.

Persistent · 04-18-2021, 08:36 AM

The wiring diagram is simple. It would be hard to miss-wire it.

Usually this type of monitor has parameters that need to be set to make it read accurately. It needs the battery bank size most of all. It may adjust itself after a while, but there is most likely a procedure to set at least the battery bank size.

Otherwise it sounds like it is working properly.

It also sounds like your engine alternator is not charging your house battery enough to replace what is lost to the 12 volt appliances.

I don't know what a wall charger is. Do you connect it directly to the battery posts?

If so, the shunt will not see the "wall charger" charging current. That is going to confuse it. All current in and out must flow through the shunt for the monitor to work.

Persistent · 04-18-2021, 09:04 AM

Quote:

Originally Posted by FranzUgan

H ...
Both batteries negatives are going to chassis and engine block.
I wired the shunt on the aux battery between the battery negative post and the chassis ground. No other connection on the battery negative post. All other connections are done on the shunt terminal thar goes to the chassis.
I cannot seem to get a proper reading from the monitor. Aux battery is charged at 100% and after various hours with the fridge running and the engine on the monitor will show a gradual decrease and eventually read 0% but battery has plenty of charge in it and reading 12.6v from same monitor.
Have I wired something wrong or I just got a defective unit?
Thanks
h

The chassis battery negative must be connected to the frame side of the shunt. No negative cables may be connected to the house battery side of the shunt or the house battery terminals. All current to or from the house battery must flow through the shunt.

jporietis · 04-18-2021, 09:10 AM

When you use the way charger are you hooking it up to the battery post. You should be hooking it up to positive terminal of battery and neg to frame so shunt can see charging current

mfire1339 · 04-18-2021, 09:12 AM

Proper setup is important. I needed a magnifier to read instructions. Once set it has worked perfect.

Mike

FranzUgan · 04-18-2021, 09:53 AM

Quote:

Originally Posted by Persistent

The wiring diagram is simple. It would be hard to miss-wire it.

Usually this type of monitor has parameters that need to be set to make it read accurately. It needs the battery bank size most of all. It may adjust itself after a while, but there is most likely a procedure to set at least the battery bank size.

Otherwise it sounds like it is working properly.

It also sounds like your engine alternator is not charging your house battery enough to replace what is lost to the 12 volt appliances.

I don't know what a wall charger is. Do you connect it directly to the battery posts?

If so, the shunt will not see the "wall charger" charging current. That is going to confuse it. All current in and out must flow through the shunt for the monitor to work.

The battery bank size has been set.
All the negatives are connected to the "negative load" side of the shunt and the other side goes directly to the battery post. No other connections are done on the battery post.

Alternator works fine. If it was not I would have to recharge the house battery every couple of weeks, and I just top it up with an ac charger (wall charger). It has a "dedicated cable" on the shunt that I use for charging the battery.
The fridge draws about 3 to 5 amps and the alternator is 100 amps.

I just did a 6 hours trip with fridge on. According to the display I lost 40% of battery capacity. It shows that the battery is at 27% capacity yet the battery has 12.8v.
Wirh the engine running I'm getting 14v to the house battery and if the fridge is on it displays around -2amps. If I turn the fridge off I get +0.2 amps.
Eventually the display will read 0% but battery voltage will be at 12.7 or 12.8 and fridge will happily run for hours with the engine off.

Dutch Star Don · 04-18-2021, 05:11 PM

Yours is a different brand, but I added the Magnum BMK shunt to my coach. You're suppose to wait several hours for it to determine the battery status. It was doing the same thing. It was dropping percentage of charge when I knew the batteries were full. Finally, I operated my full wall slide and saw that the percentage of charge was going up.

I called Magnum and they said their product was most likely not the issue. I had to give them my credit card to get them to send a new replacement for their brand new BMK I just installed. I got the new one, it worked perfectly and it learned the battery status in under an hour. I called Magnum....sure enough, their unit tested bad (backwards operation).

FranzUgan · 04-18-2021, 10:54 PM

Quick thought, since both the start and house battery share the same ground (chassis and engine block) could that affect its operation?

Persistent · 04-20-2021, 08:12 AM

Quote:

Originally Posted by FranzUgan

Quick thought, since both the start and house battery share the same ground (chassis and engine block) could that affect its operation?

As posted before:

The chassis battery negative must be connected to the frame side of the shunt. No negative cables may be connected to the house battery side of the shunt or the house battery terminals. All current to or from the house battery must flow through the shunt.

You said this was wired correctly.