question

sorry forgot to add ill be using a color gx

Hi VK. Nice system for a caravan.

1. He's 'sorta' right. Not absolutely essential.. but..

2. I *suspect* you wouldn't be happy with less than the best, so go for it. And sometimes just checking your exotic batts, a second opinion? It'll need tuning though.

3. Useful for measuring dc loads, which your other kit doesn't know about. Even just for dc lights, it's a no-brainer.

With your CCGX, and hooked to VRM, your van can stand proud. A BMV is the icing on the cake, your guardian angel..

Hi

Does your batteries have their own bms system that can calculate its state of charge?

@vkdirector, I absolutely concur with @JohnC... I'd add one more thing, however, which is that there is a significant degree of functionality of the MultiPlus that is added when you have a BMV as well. The best example of this that I can think of is if you'd like your Multi to ignore AC input depending on battery SOC (ie, stay off-grid as much as possible even when connected to shore power). With the BMV, you can connect the relay out of the BMV to one of the Aux Ins of the Multi and then use a combination of three Assistants to tell the Multi to ignore AC power until (for instance) your battery bank reaches 40% SOC, then switch to AC power and charge the batteries to, say, 60% SOC, then go back to ignoring AC input.

The application of this is, for instance, if you're parked and hooked up to shore power but the electricity rates where you're parked are high, so you want to run on solar as much as possible, but you also want to make sure that you don't run your batteries down overnight; at the same time, however, you don't want to charge your batteries fully off shore power when you know you'll have 3kW of solar available in a few hours when the sun comes up. By using the BMV/Multi combination like this, you only switch to shore power when your batteries run down, then AC kicks in, charges them up just enough to make it until morning, and then switches back off (back to inverting). It's a very useful feature (one of several) that the Multi alone doesn't offer.

Really, I think that's the biggest consideration here: yes, the BMV is more accurate than the Multi's internal battery monitor, but more importantly than that, the BMV is capable of determining SOC of your bank (and, thus, an approximation of time remaining in your bank as well), which the MultiPlus alone is not capable of.

TBH and IMHO, your wholesaler is a bit of an idjit for not being aware of this, because it's really a significant degree of additional functionality that having the BMV opens up for you.