Reading voltages to see how much power is left in the battery bank.
When building any camper set up, or indeed anything which relies on a battery, it's always good practice and very useful to have a way of seeing how much power is the battery. In our full conversion kits we use a simple voltage display. With a little bit of interpretation, this can tell you most of what you will need to know. For those of you with a thirst for more data or who want to keep a keen eye on every last Watt, then a Victron BMV712 is the answer.
 |  |
Below we summarise a few voltages and what they might mean. This does not apply to Lithium battery set ups, but it should help most people gain a bit more understanding of what their battery is doing and how to get the best out of it.
To take accurate readings from a battery. It should not be on charge from the mains, engine or solar and it should have no loads coming off it. So turn everything off. Then leave it for around 30 minutes ideally (5 minutes usually works pretty well too if you're pushed for time).
| Battery voltage | Typical meaning |
|---|---|
| <12.0V | You battery is too low, turn everything you can off and get charge into the battery ASAP. Regular deep discharges below 12.0V will shorten the life of your battery. |
| 12.0V | Your battery is pretty much out of usable power. A few lights are going to be okay, but avoid any heavy loads until you've got some charge back in there |
| 12.4V | This is typically around the 30% power remaining mark. |
| 12.7V | This is typically around the 60-70% power remaining mark. Although this is as high as you're likely to see it in systems that are only split charged. Conventional split chargers don't often "fully charge" leisure batteries. 70-80% is the best you will get. We recommend conditioning the battery every few weeks with a mains charger for best results. |
| 13.2V | This is a theoretical full resting voltage for a perfect condition battery. In practice anything above 12.9V is to be considered "full". |
| 13.5V | Float voltage. This would be when a mains or solar charger has fully charged your leisure battery it will drop to a float voltage of around 13.5V and say there. |
| 13.8V | The point at which a voltage sensing split charge relay will engage. This is an on charge voltage, likely from the mains or the solar midway through a charge. |
| 14.4V (14.7V for AGM batteries) | An on charge voltage from a traditional alternator through a split charge. This is also the point at which most mains and solar chargers will consider the battery full and go into float mode. |
This is a very simplified view of battery state and charge via voltages, but I hope it's helped those who are new to this gain some valuable information on their battery and it's role in enjoying your time away in your camper.
It's also worth adding a note in lower voltages. Please don't panic if you see 11.9V and immediately start your engine in the middle of the night (those around you won't thank you and nor will your stress levels), the occasional slight dip isn't very likely to cause lasting damage to a battery, it's just good practice to keep it above that level as much as you can.
Please note, these are simply guidelines based on our experience and this is not a substitute for following your battery manufacturer's recommendations and only applies in general to batteries and may not apply specifically to your system. If you are experiencing something entirely different. Please consult your auto-electrician.
If you have any questions on batteries, our team would be more than happy to help. Have a great day!