inverter - charger performance

[Endeavour]

Hi
I have an off-grid trailer with 4 deep cycle 12v batteries wired in parallel. I am powering nothing more really than an energystar fridge, water heater and lights & a kettle. I am running through a 1500w inverter. I also have an auto switch for when I plug in my generator via the shore power cable (which in time will be replaced by solar)

So during the day, the genny powers everything perfectly and in the evening I want the batteries to take over. The problem is, I dont think I am being efficient at all. I am losing a lot of power from my batteries overnight. My wired up battery monitor drops like a stone when I flip to battery power - I should have about 440a/h I think
I have run a kill-a-watt on my fridge and, I cant remember the figures off-hand, but it is pretty cheap to power - especially as it was pre-chilled from the generator during the day.

One thing I think is an issue, is my inverter not being very efficient. I could probably upgrade that, so could do with some suggestions that arent going to cost thousands of $ if possible

However, something I am struggling with is the 12v internal lighting. That seems to be powered via a charge/converter (original with the 80's trailer) and is making me think this is sapping my power.
I also have a seperate single battery up front which can power the internal lighting if I want - and that seems to go on for ever when I use it. And I wonder if when that is connected and I flip to the main battery bank - the charger is trying to charge up this extra battery.

Secondly, it seems that a lot of conversion is going on here: Battery bank's DC is being converted into AC via the inverter which powers the outlets. The charger/converter is plugged into and outlet and is converting back to DC to power the lights & charge the single battery - that seems a bit long winded and not very efficient

Any suggestions on what approach I should take to increasing my battery efficiencies? I'd be very grateful to hear them

[PNW_Steve]

Hey Endeavour,

I see a number of problems.

I'll start with the "buzzbox" converter. Loose it and run your 12 volt loads directly from your inadequate battery bank.

Loose any big loads that use electricity to produce heat. Water heater, kettle, coffee maker etc. Go propane or only run them when you have generator capacity to support them.

Lets pause there and ask, what kind of generator and charger are you using?

[littleharbor]

The converter is a real "no no" You are basically trying to charge your battery bank with.....Your battery bank. Next set of batteries you buy really shouldn't be 12 volt deep cycle, for two reasons. One, they aren't real deep cycle batteries, and two, wiring all the batteries in parallel will cause uneven charging and discharging which will kill your batteries prematurely. Buy at minimum, 6 volt golf cart batteries which are designed to be cycled, not for starting motors with.

Are your batteries healthy. Do you check electrolyte levels and check specific gravity on a regular basis? Important, if you want to get any reasonable life out of your batteries.

What are you using for an inverter. A name brand pure sine wave inverter is a good investment. Stop heating water with electricity and figure out what you can get away with as to inverter sizing. Large cheap inverters will consume more power in a day, doing nothing, than your fridge consumes.

[NCmountainsOffgrid]

your Converter is only there to provide 12v power to your 12v devices while on external 120v power, rather than from your batteries, but you really dont need it

run heating devices only when on the Generator

[Endeavour]

thanks all

The generator is a Honda eu3000is

It makes sense that the charger is trying to charge the battery, I guess I can remove that side of things completely, but then will need to rewire the lights to run off the bank, But then I'll also have no lights under generator power

Come to think of it, I don't think water heater would be running off the batteries as thats only running occasionally during the day under generator power.

[littleharbor]

Your lighting shouldn't be affected by disabling the converter. If you can get into it and locate the circuit that charges the batteries it should still function normally otherwise when shore power is connected.

[Endeavour]

I did try disconnecting the charger/converter and that turned off the lights.
Of course I could try and re-wire them to the battery bank and rip out the converter - but that means I am still running lights from the batteries even if I have generator power.

[littleharbor]

As mentioned above. just disable the charging circuit. This should be a single wire from the converter, to the battery. Try adding a DC rated switch inline on that wire.This shouldn't affect the lighting circuit as they should work while not running on shore power, right? Also, unless you are replacing the converter, you want it working while on shore power.

[Endeavour]

thanks
I think the part I may be missing - is finding the 12v dc panel as I dont recall seeing one - I only know about the AC breaker box)

Right now, my charge converter is plugged into an AC outlet, and has a bunch of wires which I know not where.

So lets assume I manage to isolate the charging wire. That will mean I get AC to DC powered lights via the charge controller when plugged into the generator.
And then when on battery power, I get DC to AC (via inverter) and then back to DC again via the controller - is that correct?

The converter is a B-W 3230 (if that makes any difference)

[ewarnerusa]

Editing because I misread the OP and responses.
The 12V lights are meant to be run off the battery, the converter is there to provide this 12V power when plugged into shore power and to charge the batteries. What people are suggesting is not disconnecting the converter from 12V, but rather disconnecting it from AC power when you're running off inverter.

In my camper, the converter gets its power from a direct wiring to the AC breaker panel. It takes 120V AC and converts it to 12V DC. What I did is was open up the AC breaker panel and identify the line powering the converter. I then moved this to a new breaker so it is all on its own. This breaker works as an on/off switch for the converter so that it can be shut off when running the camper off inverter power.

[littleharbor]

You're looking for the wire that goes to the positive battery terminal. If you can add a switch to it and leave everything as it was otherwise, then everything should work as intended. The thing you would need to do is simply switch it on ONLY when connected to shore power.
There are probably more elegant ways to achieve this. Basically you just don't want your converter trying to charge your batteries using your batteries as a charging source. This is what happens when an inverter is connected to the batteries and then shore power is plugged into to that inverter.

[NCmountainsOffgrid]

there's no real need for any Converter, as any 12v items will ALWAYS work directly thru the fuse box from the batteries, if you bypass the Converter, and just leave the Charger to charge the batteries when on the Generator - and the Solar will obviously ALSO charge the battery bank when the gen is not running, if the sun is available.

most RVs who have a Converter do so so because the 12v lights, fans, and thermostats can then run from directly from a 120v power conversion, rather than continuing to use the House batteries. This also allows the typical 'built-in' Charger to more easily and quickly charge the batteries.
The reality is that Converters are not really necessary, though, as the 12v items can certainly ALWAYS run off the batteries, since the batteries will either be charged from Solar, or thru the Charger during the generator runs, in your situation.
The only drawback might be in the event that you lost all battery power, due to dead batteries, or you removed them for maintenance or replacement, you would not have power to your 12v items during that time.

You can simply bypass the 'Converter' part of the box, and leave the Charger intact.

[Endeavour]

just to add, i do not want the charger to charge my batteries, I have a seperate (modern) charger for that, which I connect up via the generator manually.

[PNW_Steve]

just to add, i do not want the charger to charge my batteries, I have a seperate (modern) charger for that, which I connect up via the generator manually.

Your "converter" serves two purposes. Charge the house battery and support 12v loads when you have shore or generator power.

If you have a more modern charger then you do not need the converter. I would remove it and connect the 12v connections to your batteries.

BUT.... There are a number of ways that you could be a danger to yourself and others if it is not done properly. I strongly recommend that you get some qualified local help to at least check your work.

We can't all do everything well. I try to recognize my own talents and discern when it is time to call a pro. Perhaps you may be at that juncture?

[ewarnerusa]

just to add, i do not want the charger to charge my batteries, I have a seperate (modern) charger for that, which I connect up via the generator manually.

If you use a different standalone battery charger, then as NCmountains described you don't have any need for the converter. I would leave it installed as backup and do the AC panel isolation like I described in my post, then leave it permanently off so it never gets energized. Then it's available as a backup charger at the flip of a switch.