DC electrical issues.

[Phuht]

Hello everyone,

I have been putting a lot if work (and money) into a 2000 coachmen Clipper 1260. I've made quite a few upgrades (water heater, DC outlets, new floor, battery monitor, etc.). I am trying to get it ready for some boondocking and have run into an electrical issue. I have a 75Ah 12 volt deep cycle flooded battery (Which will be upgraded to 2 6v 230Ah golf cart batteries in series). The battery reads about 12.8 volts on a full charge but my battery meter reads at 12.2 volts and the 12 volt cigarette outlets read 11.6 volts. I want to run a 400 watt inverter at a modest 60 watts to power a small TV and I want to plug it into one of my DC outlets. When I try to run the inverter, it immediately says I'm at low voltage, even though my battery is not running low voltage. The only other DC devices used are the overhead lights. I'd like to figure out what us causing my low voltage problems. Any ideas?

Note: I did not move the battery to climate control for the winter and the battery is about a year old. It HAS been exposed to several nights below 30 degrees.

[Persistent]

Lead/Acid battery voltage changes with the amount of load. All those different voltages mean nothing unless they are all done when the battery is loaded the same.
Next, loose connections, connection corrosion, and long runs of thin gauge wire can cause low voltage.
If you are going to wire in a 400 watt inverter, why not use 10 gage wires to the battery with a 30 amp fuse. That way you can get 400 watts when you need it.
Static battery voltage at 12.8 is a good start. Static means no load and no charging for a few hours.
Next connect the 12 volt house system. Measure voltage again at the battery terminals. Measure the load end of a circuit. Do not change the load between measurements.
If voltage at the battery is significantly down after the load is connected, the battery is not capable of supporting the system. It could be a bad battery. It could be too much current being drawn from the battery. 5 amps from a 75 amp hour deep draw battery is a substantial load. 30 amps is extremely heavy, possibly too much. Voltage at the battery terminals will drop quickly as the load current increases. Measuring the current draw is the best way to load test a battery.
Voltage at the load end of a circuit being lower than the voltage at the battery terminals means the wire and connections between the battery and the load may be insufficient.
Use these two scenarios to isolate your issues.
Getting the battery load tested is also a good way to determine if the battery is bad. However, many automotive battery shops are set up to test engine start batteries. Deep draw batteries are often tested using a 20 hour discharge rate for standard purposes. (75 amp hr / 20 = 3.4 amps for 20 hours).
Lead acid batteries can be safely stored in freezing conditions. All lead acid batteries should be stored fully charged. Full charge takes 14 to 18 hours regardless of starting state of charge. A fully charged battery is unlikely to freeze anywhere you would choose to store it. Not storing fully charged can lead to freezing and sulfation. (Sulfation is when plates accumulate large crystals of lead sulfate.)
I wish you good luck and happy trails ahead!

[Collyn]

Originally Posted by Phuht

Hello everyone,

I have been putting a lot if work (and money) into a 2000 coachmen Clipper 1260. I've made quite a few upgrades (water heater, DC outlets, new floor, battery monitor, etc.). I am trying to get it ready for some boondocking and have run into an electrical issue. I have a 75Ah 12 volt deep cycle flooded battery (Which will be upgraded to 2 6v 230Ah golf cart batteries in series). The battery reads about 12.8 volts on a full charge but my battery meter reads at 12.2 volts and the 12 volt cigarette outlets read 11.6 volts. I want to run a 400 watt inverter at a modest 60 watts to power a small TV and I want to plug it into one of my DC outlets. When I try to run the inverter, it immediately says I'm at low voltage, even though my battery is not running low voltage. The only other DC devices used are the overhead lights. I'd like to figure out what us causing my low voltage problems. Any ideas?

Note: I did not move the battery to climate control for the winter and the battery is about a year old. It HAS been exposed to several nights below 30 degrees.

Re 'The battery reads about 12.8 volts on a full charge but my battery meter reads at 12.2 volts and the 12 volt cigarette outlets read 11.6 volts.'

It is not clear what you mean by 'The battery reads about 12.8 volts on a full charge but my battery meter reads at 12.2 volts' Are you measuring with two different meters - or what?


The cigarette outlet in many vehicles has a dedicated system that attempts to maintain a constant 12.8 volts - this may not be so with your system.

Collyn (in Australia)

[twinboat]

Try the inverter close to the battery and use an extension cord for the 120 volts.

To thin, to light, and to long, a 12 volt run all add up to to much voltage drop.