Above is a picture I captured of the simple voltage gage I buy to install in friends 12V circuits.
Having a degree in Electronic Engineering, I’ve gotten into answering questions and helping people with their 12V and other DC systems on my Travels.
One of the most common problems I run into with Vandwellers is people running their house battery down low enough or enough times to damage it, and they need to spend the money to buy a new one prematurely.
This is not only a costly expense for vandwellers, but also requires time to find the cost effective replacement.
In actuality, it adds to their day to day frustration that they are not in control of their destiny, because they forget and drain their lead-acid battery too low.
I have two examples of vandwellers that needed assistance this year thinking they were over draining their battery and thought they were hurting their house battery.
In preparation for my travels this year I designed some circuits called Low Voltage Disconnect (LVD) circuits to being on my travels to since their problems.
Note: See my related post on LVD design.
1. First friend has a lead acid battery charged from solar. They would plug their laptop and phone in to charge and run in the evening and were not aware of how much relative power their battery had.
In this case, my friend didn’t need some fancy device to show and track watts and amps but just a simple volt meter that they could see the voltage of their battery and when the voltage was low enough they shut things down from charging for the night until solar charging the next day.
So friend #1 just needed a simple volt meter, like the one above, to know the relative state of the battery. Ie. The lead-acid battery about 12.7V without charging and noting drawing on it is full. The same battery at 12.1 not charging and no draw on it is where to stop.
Lead-acid batteries are happiest charged the next day when used overnight.
So my friend now can monitor her usage real-time with this simple volt meter. When it gets down to 12.1V on the battery running the laptop all they have to do is disconnect the charging of the laptop. The voltage will probably go up a bit and that means they can run a bit longer. Soon they will know when running the computer at what voltage on the volt meter they will see to 12.1 when the laptop is unplugged.
The vandweller is now in charge of their own destiny, and this is a good feeling.
2. Friend and I met on the road too. After discussing her house battery setup, I learned her battery is a Battleborn 100 Ah LiFePo4 battery.
I advised her that her battery comes with BMS (Battery Mangement System) that protects the battery in many ways. Charge and usage current are just two examples, but the battery also has an auto voltage shutoff on low voltage so they can’t damage the battery by forgetting and going too low.
Yes the Lifepo4 battery doesn’t want to run on the auto shutoff as this is a battery protection circuit. It is best to charge before it auto shuts off. A battery voltage of 12.0V would be good for recharging. When charging lithium with the proper lifepo4 charger you may see 14.6-14.6 volts when charger shuts off and my often rest at 13.3-13.7V
This friend just needed some education and a volt meter would be helpful, but I had only one with me and I had used it on friend #1’s vehicle.
My last example is my off grid friends house. She bought the house with an older 24V solar system to supply power.
A control monitor was never installed on the first floor living space and the system is in the basement. For her to know the health of her system and to know what she could run off the inverter. She also just needed the same volt meter and follow the same rules for lead acid batteries as I noted above. The only exception is that her resting voltage is 24.2, double the 12.1.
After installation of the volt meter, she too was now in control of her own destiny and was no longer risking draining her battery bank to low and the inverter shutting off leaving her in the dark.
Many people will tell you you need to know watts or amps in and out. No you don’t! A little education and you have a good handle on the health of your battery from just the volt meter.
Above is my volt meter for my FWC camper LiFePo4 house battery that I installed and is all I use to know the health of my battery.
Yes, you can get a lot more technical but the vandwellers I know just want their systems to be simple and this is just that.
Brent
macaloney@hotmail.com
No comments:
Post a Comment