Replace Converter/Chg with Inverter/Chg

[Frederick_L]

Hello - I have an RV travel trailer that does not have solar or an inverter. I'm planning to add both. It does have a converter/charger as a part of the load center. I've watched a couple of videos on the benefits of replacing the converter/charger with an inverter/charger. These videos also recommend disabling the converter/charger, and in some cases removing it. Makes sense to not have two battery chargers. However, the converter provides 12volts to the RV (to the fuse block), even with the battery removed. Does the inverter/charger also provide 12volts to the RV? And will it provide 12volts to the RV with the battery taken out? I ask because I often take the battery out during the winter and leave it on a trickle charger in my garage. Does it make sense to leave the converter/charger and just throw the breaker. That way I can have 12volts with the battery out. Just confused about what happens to the 12volt feed to the fuse block with an inverter/charger considering the cables go straight from the battery to the inverter. I guess there still is a feed from the batteries to the fuse block. So I guess there's no problem as long as the inverter cables stay attached to the feed back to the fuse block with the battery out. Does that make sense? Thanks much.

 

[FilterGuy]

Could you provide some kind of rough diagram of what you have. It would help me understand the question better.

 

[Steve_S]

Quite a few RV'ers switch to Samlex Inverter / chargers which lend themselves to Marine & RV very well. They have provisions for "shore power" and many have dual AC input (shore & genset) with built in ATS (auto transfer) for when grid power is available. Inverters do not have 12VDC outputs. Your DC comes from your battery bank, if the bank is not 12V but higher, then a step down converter is used to supply 12V circuits tapped off the batteries.

Have a look at the Samlex Link in my signature. There is also schematics showing varied installations There are several other Inverter/Chargers that can fit the bill for an RV but not all. Also be aware that many require additional external hardware for switching & sensing power sources which can add to the overall costs.

With regards to your battery storage, If they are well charged prior to storage and parasitic draw is eliminated (no power being drawn at all) they can sit for quite some time. Lead won't freeze if it is fully charged and still workable to -40C. If your dealing with different chemistries than their rules apply. With regards to a "Trickle Charger" you can install a Solar Charger / Maintainer and that would do the job quite nicely and it does not have to be huge either.

 

[Frederick_L]

I've attached a picture of a typical converter/charger. Mine is simiiar to this one. It has a panel with breakers for 120v appliances. It also has a panel with 12v fuses for 12v appliances. The converter/charger unit is actually a separate unit that sits below the 120v and 12v panels. Typically there is a 120v breaker that feeds power to the converter/charger. Then there are two 12v leads from the converter/charger that feed to the 12v fuse block. And then as shown in the picture, there are two 12v leads that feed back to the battery from the 12v panel. Here's what I find confusing. The converter/charger is charging the battery but at different voltages: bulk - 14.6v; normal - 13.6v; and float 13.2. So, do the 12v appliances connected to the 12v panel also experience these shifting voltages? Maybe 12v appliances are designed to accept a range of input voltages near 12 volts so it would not make a difference if the voltage to the 12v fuse panel was 12.6, 13.2, 13.6, or 14.6. Just curious how the 12v appliances handle these voltage variations.

So, now on to replacing the converter/charger unit with an inverter/charger. As I mentioned, it is recommended to replace a bad converter/charger unit with an inverter/charger. It is recommended to simply remove the converter/charger unit by removing the 120v feed to the converter/charger from the 120v breaker, and then removing the 12v feed from the converter/charger to the 12v fuse panel. Simple enough. Then you replace the 15amp breaker for the old converter/charger with a 20amp (or possibly larger) breaker that will then provide AC power to the inverter/charger. Then appropriate thick cables are run from the inverter/charger to the battery (with appropriate fuse). These cables will allow the inverter/charger to invert 12v to 120v, and also charge the batteries when the inverter/charger is connected to 120v. So my question centers on, after the swap, how does 12v power get back to the 12v fuse panel? Do you just use the original wires that run from the 12v fuse panel back to the battery for this purpose? Is the gauge large enough for this purpose? (I ask because the charging amps of the old converter/charger may be less than the charging amps of the new inverter/charger.) And if yes, then will the inverter/charger provide 12v power if the battery is removed. Hope this makes sense. I guess what I'm asking is an inverter/charger actually an inverter/charger/converter? I may be overthinking this. Seems like a converter/charger should have a set of leads to charge batteries, and another set to provide 12v power to the 12v fuse block. Obviously that is not the case. So, it seems simple enough to replace a converter/charger with an inverter/charger, but I'm not sure about the integrity of the result. And one of the videos I watched was from Xantrex.

 

[Steve_S]

RV Converters are not typical INVERTERS.
Inverter / Charger will invert 12VDC to 120VAC.
It will charge the 12VDC battery bank as appropriate for the battery type.
It will NOT provide a 12VDC output to power 12V devices. That has to come from the 12V battery. In an RV Setup, (same for marine etc) a "Conditioner / Regulator" will have to be installed between the battery & 12V Fuse / breaker block. This is to ensure that ONLY 12VDC goes out at enough Amps to supply the 12V side (based on the total amperage that the fuse/breaker panel needs to support). When charging Lead or other batteries, the voltages will exceed 12VDC to 14.9 for bulk and 15.8V for equalize / desulphated which could cook the 12VDC devices, depends on device.

It is not that difficult to work out. Space on the other hand has to be figured in too. You need enough space to house the Inverter/Charger and allow for airflow as they need to be able to cool off while running, they cam make a LOT of heat & quickly, during charge & discharge.

 

[Frederick_L]

So, here's the video by Xantrex that I watched on replacing a converter/charger with a Xantrex inverter/charger. I basically get what's being presented, however the video does not cover what I consider to be a basic question: how does 12volts get back to the 12v fuse panel that is no longer being fed by the converter/charger, which was disconnected? Could be automagically ;-) The other basic question is, how does a battery charger that puts out variable voltage (from 13.2 volts to 14.4 volts) power a 12v fuse block? I think people who do this all the time get the answers intuitively. But it's not intuitive to me. Thanks.