I bring this post forward as most of the questions I get from fellow vandwellers are associated to how to charge, what can you run on them, and why I keep killing my battery. This is not a design and build tutorial.
(Above is a screen capture of a google search)
(Above is a screen capture of a google search)
One of my friends has the following AGM battery from Walmart as seen below.
(Above is a screen capture of a google search)
The above 55Ah battery is a special lead acid battery design that doesn’t off-gas like wet cell lead acid batteries. Like all lead acid batteries the rule of thumb is that the actual available Ah is half the rating, or in this case 27.5Ah.
This is a modest size battery for Vandwelling. A 100 watt solar panel and lead acid solar charge controller is what you need, unless you run into days of little to no sun in the winter when sun is at the lowest angle. In the case of my friend 100 watts of solar wasn’t enough with her usage and sometimes cloudy weather.
This brings up the need to charge another way. There are 2 ways to charge off your engine.
1. Using a isolator or combiner.
a. The isolator allows the engine to charge the house battery when you run the engine and your car battery is fully charged.
b. The combiner does the same as the isolator for charging from the engine, but will also share solar charging to the engine battery when house battery is fully charged.
2. Using an inverter off the vehicle engine and plug in a 120 v battery charger to charge the house battery when engine is running and you set up this charging items. This method also allows you to run a shore cord to a friend’s house to charge your house battery without solar or using the engine.
Lastly, the combiner can be set up to combine both the engine battery and house battery when switched on. This would help start your vehicle from your house battery. I don’t recommend this in most cases as you should always make sure your engine battery is properly maintained, and wires typically used with a combiner is #10 wire and it isn’t able to send enough current to start the engine.
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In addition to lead acid batteries there are LiFePo4 batteries, like the one below that I used for my house battery when I was traveling in my Prius.
(Above is a screen capture of a google search)
The LiFePo4 battery can be charged the same three ways, as I mentioned above for lead acid batteries, but not necessarily with the same parts as the lead acid since the chemistry of the LiFePo4 battery is different.
It is different because it’s rating of 30 Ah is the truest available current. Yes this means the lithium battery at 30 Ah has more available power than the 55 Ah lead acid battery above.
The LiFePo4 battery is also less weight and size. Many LiFePo4 batteries like this Bioenno battery, above come with internal battery management systems (BMS). It’s internal BMS controls current in and out and shuts off automatically if it gets too warm and shuts off when it runs out of power and won’t damage the battery. these are only some of the things that BMS does.
These are all good things, but one caution with this and other LiFePo4 is that they have low temperature conditions where you can’t charge or use at some point below freezing conditions. Here you need to get the exact information from the manufacturer.
My recommendations
1. Look up and find a copy of the specifications for your particular battery and follow them
2. No matter what battery you use you must get the proper solar charge controller for that chemistry. Some solar charge controllers can be programmed or set up for different battery chemistries.
3. The solar panel you select has no impact on the battery, only the charge controller. check that the solar panel and charge controller are compatible.
4. The charge controller must be equal to the solar panel amps that come from the panel/s or higher. If running 100 watts I would recommend putting in a 20 amp charge controller so you can add to the solar later without replacing the charge controller.
5. Put a volt meter on your battery so you know if it’s charging or not. This is especially important for lead acid batteries as you should stop using and charge at about 12.1 volts without drawing any current.
6. If you are in an area with prolonged cloudiness is often possible consider charging off your engine. For LiFePo4 batteries check that you can charge from engine and what voltage is acceptable. Remember to run a red and black power corded from engine battery to house battery - the size of wire affects the rate of charge.
9. Study everything or find someone with the skills to do the work. One of my Vandwelling friends has a 100 Ah LiFePo4 battery and has an inverter that was installed without a fuse. You need all power from engine or from battery fused to match the components.
If you don’t know what you are doing STOP!!!
Go get help or find someone to do the work.
My recommendations are just that, recommendations. There are times when alternate ways can address needs. You must possess the skills and knowledge to address any of these recommendations correctly. This includes having the correct tools and knowledge in what parts are designed for the work you wish to perform.
Note: I have no affiliation with any battery supplier except as a consumer.
Brent
macaloney@hotmail.com.
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