Knowing how much juice your battery has

Victron BMV-700 battery monitor

It helps to know how full or empty your battery is. In the same way that you wouldn’t drive without a fuel gauge, you shouldn’t use a battery without some form of monitoring.

Lead batteries last longest if they are always kept above 50% of their capacity. Lithium batteries last longest if they are kept above 30% of their capacity. Abusing batteries by discharging them too far seriously shortens their useful life. The cost of a battery monitor works out to be much less than the cost of a new battery.

There are lots of monitors out there. Several of them are great demonstrations of what happens when you let engineers specify the design. They do their job (some very well) but they look horrible and their interface is terrible to configure. Continue reading “Knowing how much juice your battery has”

Solar panels are alive and charging

The almost 800 Watts of solar panels on the van did a great job charging the battery on our recent trip. The charger took a little bit of custom configuration, but the menus were easy enough to work with and now everything works well.

I started off with the default charge controller settings for a Lithium battery, but once the battery got close to full, the charger made the battery management system upset. The BMS wanted 13.5 volts float charge, the charger was producing 13.8. Not enough to hurt the battery in the short term, but something that I needed to take care of. If nothing else, I wanted to stop the BMS light from coming on!

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Mocking up cabinet locations

Cardboard cabinets - it's all we have for now!

We’ll be putting removable cabinets in the front of the van. We knew pretty much what size they needed to be in order to hold the items we want to carry, but we didn’t know what that meant for maneuverability in the living area of the van.

So, I resorted to a tool I use in my day job – paper prototyping. We’d already done this to work out the best configuration for the electrical components in the garage area of the van. Now, we just needed bigger cardboard boxes and more tape in order to make real-size mock-ups of the cabinets. Continue reading “Mocking up cabinet locations”

Logistic Track – the super-connector

Aluminum l-track makes a reconfigurable tie-down system

Logistic track (also called l-track or airline track) is an extruded aluminum strip that has holes drilled through it at 1″ intervals, and an inverted “T” cross-section cut out through its length. Connectors slide in through the holes and then lock in place with a spring or a bolt. That makes it easy to configure to support any load you want to carry.  Continue reading “Logistic Track – the super-connector”

Making 120 volts from 12 volts

It’s magic! You can take 12 volts DC from a battery and turn it into 120 volts AC ready to power all your devices. In fact, the more you know about how electricity works, the more impressive that magic becomes.

The magic all happens in a device called an inverter. They come in different sizes – from something that might just power a small stereo all the way up to something that can run a whole house worth of devices.

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