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Feb 22, 2013 -

Voltage Matters

A few weeks ago, I asked, “Does voltage matter?” I was not satisfied with the answer that I got.

As a reminder, voltage can be compared to pressure. You can have all the battery capacity (amps) in the universe, if you have no pressure (voltage) to get that capacity to your electrical devices, you won’t have power. The amount of voltage your electrical system has depends on the state of charge of your batteries and the size of your wiring as it relates to your load. Small load through big wires means less resistance and more pressure, big load through small wires means more resistance and less pressure.

Voltage is a very poor indicator of the state of charge of batteries. This is because it fluctuates wildly depending on the load on the system. But because voltage is almost useless to determine the state of charge of batteries does not mean it is a meaningless number. Voltage can tell you some useful things about the state of health of your entire electrical system. I therefore disagree with folks who claim that voltmeters just about useless.

Again, voltage is akin to pressure. You only have so much pressure and that has to feed your entire electrical system. If you put too big of a load through wires that are too small (like a a torrent of water trying to pass through a garden hose), you will get a lot of resistance and reduced pressure. This reduced pressure is called voltage drop.

For most applications, a voltage drop of up to 2% is acceptable. For lower wattage items, like lights, up to 4% may be okay. This is where the voltmeter comes in handy. Turn on a typical load one evening, say the inverter, TV, and a light or two. Check the voltage at the batteries and check it again inside. If you’re reading 12.5 at the batteries and 12.3V inside, you’re doing okay. But if you’re reading 11.8V inside and your lights are flickering, you have a problem.

The causes of big voltage drops can be minor, like loose and/or dirty terminals or low water levels. Such corrections can be made easily. The causes can also be major, like undersized wiring for the load. The temporary solution there is to reduce the load and the permanent solution is to run bigger wiring (with a smaller gauge number) for that application.

Regardless of the reason for the voltage drops, keeping an eye on them is a good way to monitor the state of health of your electrical system. I have hit the road in the morning with 12.5V showing and stopped for lunch at to 10.5V, with my fridge having turned off. Did I leave a load on? Nope, a terminal connection got loose during travel over a bumpy road. If I only relied on my battery monitor, I wouldn’t have known there was a problem until my freezer contents started to soften.

I struggled with low voltage at the start of my boondocking experiment on the beach. Not being satisfied with answers that focused on the health of my batteries and their state of charge, I ignored anyone who told me voltage readings were a red herring and not relevant. I knew voltage was a clue and I was right. I wound up having loose and dirty terminals as well as undersized wiring for my application. I’ve resolved all those matters (although the latter one needs a more permanent solution).

Now, I have the satisfaction of starting my evening with 12.5V on the voltmeter and never seeing that number go below 12.3 even with the fridge and a couple of lights running while my computer is charging. I haven’t seen a light flicker in recent memory and I can turn on my inverter to print or use the vacuum cleaner in the evening. If I had believed that voltage doesn’t matter, I would be a much unhappier boondocker this morning. Heck, I probably wouldn’t even be a boondocker anymore.

Tomorrow, I will have been here a month, a full 31 days, and I don’t anticipate having any trouble making it to the end of the first week of March, another two weeks or so.

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Appliances, Batteries, Battery Monitor, Electricity, Fridge, Technical    3 Comments
Feb 16, 2013 -

2036 Hours and All Is Well

I got home to 12.5V and 0.5 going out. Very normal readings. I may actually be able to sleep tonight. L and I think that I had the great misfortune of checking the monitor when the fridge was cycling on.

Speaking of the fridge, I woke up to it being 3.5 degrees Celsius warmer than I normally keep it (4.5 versus 1), which is on the high side of okay, since it had shut off due to low voltage. I restarted the fridge once the batteries were topped up, but the temperature was veeeeeeery slow to drop. It’s now 2.8 after being at 3.5 when I left an hour ago, so it is steadily going down. But it just goes to show how long it takes for a fridge to cool down and how little time it takes for it to warm up. I’m glad I have my thermometres now.

L and I had a nice time at the saloon reminiscing about our travels in Yukon, Alaska, Manitoba, and Scotland. It’s always nice to meet an American who is so well traveled in Canada (he’s been to every province plus Yukon). We are both annoyed that the saloon allows smokers, so we’re both pretty smelly right now. I’m due for laundry anyway. 🙂

I’m beyond exhausted but willing to concede that it is way too early for bed so I’m going to shut down everything, put on a movie, and let my batteries sit for a couple more hours. Da da da dum.

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Appliances, Batteries, Battery Monitor, Electricity, Fridge, Nice Folks, Social, Technical    2 Comments
Feb 8, 2013 -

Electrical Good News?

I came home this evening to a voltage in the low 11s and a battery monitor that claimed I was at 98% capacity…

I had a theory. I shut off the fridge… and voltage leaped to 12.5. I repeated the exercise after being home for about an hour and running a light that long. Still 12.5.

So the culprit is the fridge. For some reason, it’s drawing a ton of voltage.

If I need power at night to do whatever, I can just shut down the fridge, wait a couple of minutes, and do whatever. I still need to figure out why the fridge is drawing that much voltage, and I’ll start by tracing the lines to and from it. But it seems that I really don’t have the huge problem I seemed to have on Wednesday and I have a good clue on where to start troubleshooting.

Thank you to everyone who has been hanging in there with me and trying to help me resolve this issue. I’m getting close! 😀

 

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Appliances, Batteries, Battery Monitor, Electricity, Fridge, Technical    7 Comments