Hi Gerry,
The idea that certain devices have to be used with nic salt or freebase is really just marketing. Either can be used in any device you like. The real difference is the throat hit - that catch in the back of your throat when you inhale nicotine. Salt nic was developed to have reduced throat hit so higher concentrations of nicotine would be inhalable.
About recommended devices: There are three main styles of vaping at the moment. The first decision you have to make is whether you want a pod mod, an MTL device or a DL device. Each type of device can deliver a similar amount of nicotine per puff, but the vaporize a different amount of juice so the concentration of nicotine you want to use with them is different.
- Pod mod - tend to be small devices. Pod mods vaporize a tiny amount of juice per puff, so they tend to be used with really high concentrations of nicotine - often 20 - 50 mg/ml.
- MTL (mouth-to-lung) - middle of the road option. Vaporize a moderate amount of juice per puff, so they're used with moderate nicotine concentrations. 6 - 20 mg/ml is common.
- DL (direct lung) - heavy hitter. They vaporize the most juice per puff, so they're used with lower concentrations, often 3 - 6 mg/ml.
I'll just note that you should watch out for how the nicotine concentration is measured. It's usually in mg/ml (often incorrectly written as just 'mg'), but sometimes it's in percent, especially with higher concentrations. Mg/ml is ten times the percent, so your 50 mg/ml could also be written as 5%.
Both nicotine salts and freebase nicotine can be and are used in any type of device - pod mods, MTL, and DL, but the nicotine levels tend to be quite different. For example, 50 mg/ml should only be used with a pod mod (and it's the high end even for that).
I'm not quite sure where your Kanger Evod fits. I'm familiar with that as a (rather outdated - unfortunately, salespeople aren't always the best resources) battery, but I'm not sure what tank you're using with it. Can you name the tank or give us the resistance of the coils? It could be used with MTL or some DL tanks, but I don't think it would be a pod mod suitable for use with 50 mg/ml juice.
About battery life, capacity, and devices:
- Pod mods are generally small AIO devices that are low in both battery life and capacity, although since they use minimal power and little juice, some can last longer than you'd expect.
- MTL and DL: Device has two main parts, a mod (the part with the battery, which can generally be used for either MTL or DL) and a tank (usually specifically designed for either MTL or DL). Since MTL uses less power and juice than DL, it needs less frequent charging and tank fills. Battery life also depends on the specific mod, where there's a trade-off between battery life and size / weight.