I would like to be able to manually switch between the house battery and the AC200MAX to power the existing power center on my travel trailer. I was going to run the output from the AC200MAX 12V 30amp to an A/B/neither switch. The house battery would also be connected to the switch. So I could select AC200MAX, house battery, or neither as DC input for the power switch. The power center charges the house battery when on shore power, so I would put a diode in place on the AC200MAX side to prevent reverse power flow.
The A/B switch only switches the positive line. What do I do with the negative lead? Currently, both the positive and negative lead of the house battery are directly wired to the power center. I can switch the positive lead with the A/B switch. What do I do with negative lead from the AC200Max? Bond it with the negative lead from the house battery? Bond it to the chassis? Or do I need to switch both positive and negative leads simultaneously? I don’t see an A/B switch that does that.
All of this is in pursuit of more efficient use of AC200Max when dry camping. Currently I use the 30AMP AC outlet on the AC200MAX to simulate shore power, but I think I am losing lots of energy by having the AC200MAX up-convert to 110V, only to have my trailer’s power center down-convert it to power 12V appliances.
@spinner , David, it would assist if you define your house battery i.e. size and chemistry - how many Ah and is it LFP or AGM etc.
I have an RV (Caravan here in AU), it has 200Ah of LFP = approx 2,600Wh of capacity. Of this I generally use between 50-60Ah per day or around 25%. On a good day of solar, what I use is replaced by early afternoon. I carry an AC180, primarily to run the microwave or other small appliances from the AC inverter output of it. In other words, although I can recharge the Bluetti from the RV solar on a daily basis, I keep the electrically isolated.
Where the 200MAX shines is in an RV that has no other power source.
To answer your Q - If you have a change over switch to isolate one of your power sources, with a centre off position, (much like a generator transfer switch,) a diode is not necessary as the 2 circuits are never in conflict.
With DC power, switching the positive line only is ok. When one source positive is isolated, there is no circuit.
The more important part of a supply circuit, is to use a midi (or maxi depending on load) fuse rated to your needs and near to the source of each i.e. house batteries and 200Max.
As an aside, my RV use of Bluetti is in lieu of installing a large inverter to the house batteries. In other words, the house batteries take care of DC needs, the Bluetti the AC power needs and I keep them electrically apart. In that way if one goes wrong, I have the other to fall back on.
This is all about DC supply. No AC supply involved. We’re dry camping, it’s all DC, no shore power. But the trailer isn’t allowed to burst into flames if I plug into shore power at some point.
On the tongue of the trailer I have a 12V lead acid battery. It is currently connected to the travel trailer’s power center. When connected to shore power, the power center will charge the tongue battery. The tongue battery needs to be there to power the brakes in case of emergency disconnect, and also to power the tongue jack. And it doesn’t hurt for it to power the rest of the trailer for a bit if the AC200 MAX is dead.
I want to provide DC power to the travel trailer via the AC200 MAX. I want to switch between the tongue battery and the AC200 MAX for DC power. If I have the AC200 MAX selected, and I hook to shore power, the power center will try to charge the AC200 MAX via the DC output from the AC200 MAX, which would probably fry it, so I need the diode. If I always remember to switch from the AC200 MAX to the tongue battery before hooking up shore power, I wouldn’t have a problem, but it only takes once.
I was going to install an A/B/off switch to switch between AC200 MAX and tongue battery, but it only switches the positive lead. Where would I hook up the negative lead from the AC200 MAX? I don’t know.
Be very careful with the linked switch. It is rated to 125VAC @ 20A and is an AC switch. DC switching is specifically manufactured for DC current. An AC switch will likely Arc. The same goes for circuit breakers, you should not use them for the type of current they’re not designed for.
I use DC circuit breakers from battery power or solar as they are “cushioned” to prevent arcing, which leads to failure. The same goes for your 3 way isolator switch, it should be a DC battery switch. They are also double pole to switch both neg & pos lines.
Without a full circuit diagram, it’s difficult to advise, as there are too many variables. In particular, there are 2 ways to power a system that is switchable, one is at your power centre input, the other is at the output to device supply. I would not hazard a guess as to which, without that info…
PS make sure if a diode is used, it is rated to the load and the correct type.