Anyone that has been following us for any time knows that we installed a 340 watt solar kit from Go Power around three months ago. It completely changed the way we camp. With few exceptions, we have been boondocking on BLM or Forest Service lands for free ever since. It has saved us so much money that we have pretty much already recouped our investment in the solar. Going forward it will be savings which will help prolong our journey.
Prior to the solar install, we had upgraded our single 12v deep cycle marine/RV battery for two 6v deep cycle batteries. With the single 12v we had roughly 40 amp hours available for use (which isn’t much). With the dual 6v setup we had 116 amp hours. If you aren’t familiar amp hours (which we weren’t), it is a measure of charge which indicates how long a battery will last under a certain load. So, as an example, if you have 100 amp hours available on a battery and you were only drawing 5 amps the battery would last roughly 20 hours. A 116 amp load would maybe last 30 minutes if you are lucky. Why not the full hour? It’s Peukert’s Law at work which states that as the load increases the charge decreases but it is not linear.
Most batteries in cars and RVs are lead acid. Lead acid batteries should only be discharged down to 50% of their overall capacity otherwise you risk damaging the battery. So when I say we have 116 amp hours available via our dual 6v setup, that means the batteries are actually 232 amp hours total but I’ve already halved it. For the most part that amount of capacity has worked OK for us but with limits. It is not enough charge to recharge laptops, watch TV (for any length of time anyway) when the sun is down (meaning no extra power coming in from our panels). Why is that? Well, it has to do with the conversion of power when using an inverter. When running electronics on AC but via the inverter you must do some math to calculate the actual power draw. For example, my MacBook Pro, when plugged into 120v AC power, draws 1.7 amps. When said laptop is plugged into AC but being powered via DC through an inverter, that 1.7 amps becomes 17 amps. The reason is the 12v voltage of the batteries. Basically if you are running on an inverter the amperage must be multiplied by 10. It’s simple 120v vs. 12v. Less available voltage so the amps must be increased. So, still using my Mac as an example, I could potentially run it for six hours. Now, that’s not taking into account the overall draw on the batteries though. The inverter itself uses power, our refrigerator uses power, our lights use power, I think you get the idea. So when you add all that into the hourly draw we may be at more like 22 or 25 amps. So that six hours is more like four. So as you can see, it’s not a good idea to use electronics with large draws if we don’t have to. We’ve got to make sure there is enough power to run the furnace at night (still chilly here in Idaho this time of year) and things like that. So we really just use our laptops unplugged until they die with a light or two on that’s about it at night.
We finally decided that enough was enough and we’d like to be able to use whatever we want in the evenings as well. We’d love to be able to watch some movies for a few hours on the TV instead of my laptop. Misty often wants to work but she can’t run her 32″ monitor for more than an hour or two in the evenings with our current batteries. So we finally took the plunge and ordered some lithium batteries. We ordered four of them at 100 amp hours each. Lithium has some HUGE advantages over lead acid batteries.
First is weight. Four of our lithium batteries will still weigh less than our two 6v lead acid batteries. Second, as mentioned above, lead acid batteries can only be discharged down to 50%. Lithium can go to zero but 20% is recommended. So our new batteries will give us 400 amp hours but 320 amp hours available. HUGE increase in available charge. Third, they charge 5x faster. So we’ll get more out of our solar setup. Fourth, they can handle much larger draws. We’ll be able to use our microwave now. Fifth, they are safer and have no maintenance. Sixth, they last much longer. 10+ years minimum and most say as much as 20 years if taken care of.
Now, with all that said, lithium has one major down side, price. Our four battery setup was expensive. No way to sugar coat it. We won’t get the savings like we did with the initial solar kit so it’s really more about comfort and usability. Three months was enough for us to realize it was worth the cost to us. Well, we’ll confirm once we get them and I get them installed.
We are pretty excited and I’ll write up our experience with them once we’ve had some time to use them. Stay tuned!