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Old 02-17-2021, 06:07 PM   #1
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Inverter and Converter on board

I have a 2008 Destination 37G with the 6.7 Cummins. I bought the rig used. On board is a Converter and an Inverter. After a short period, my batteries are drained. Two hours max. I have the inverter off all the time. After sitting for a few hours I have to start the main engine to build up power to start the generator or run lights on battery. I have been told that it is a mistake to have an inverter and a converter. Can someone help me figure out how to get a longer charge on my batteries? Thanks
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Old 02-17-2021, 06:13 PM   #2
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I would guess the first thing is to check if the batteries are still good and actually holding a charge? It is not a mistake to have an inverter and converter, I have both. Inverter to convert DC to AC for those appliances, and converter to use the shore power or generator to charge the batteries
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Old 02-17-2021, 07:04 PM   #3
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WanderingD, I agree with misteracng. It sounds like your house batteries are in bad shape and the inverter is not the problem. There are a lot of things to consider about batteries and there is a lot of information on the internet about how to take care of your batteries so not worth repeating all of it here. However, here are a couple of key points/questions. How old are your batteries? Do the cells have enough distilled water in them? Severely draining your batteries drastically reduces their life. Discharged batteries usually take many hours of charging to reach full charge so running your engine or generator for a little while will not help your batteries very much.
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Old 02-17-2021, 08:39 PM   #4
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After you verify you have water in your battery and do a number of other basic checks, then these things may help you with your decisions to buy new house batteries:

* I assume you tested the voltage output of your converter using a simple multi-meter?

* I assume the converter did not trip a fuse?

* I assume you unplugged your converter to see how that affected your charging system?

* I assume you have checked your BSD and Boost Solenoid out. (See other posts.)

* Once you do everything to rule out a short to ground and your attention returns to thinking your battery bank is old and weak and may need replacing, then maybe these questions will be if help?


What sort of inverter do you have?

Are you sure your inverter has a charger function inside?

I know if my Dimensions Inverter/Charger stopped working when I called on the charger to function, but the inverter side was fine, I would keep the inverter and just add a separate charger.

And if I lost my inverter and it wasn't repairable, then I would buy a PSW Inverter and separate charger. So maybe this is what the previous owner did? Can you attach pictures so we can see what you are working with?

My Inverter and Charger inside my Dimensions Inverter box were both working fine, and last summer I made the decision to add a 17A Victron charger... to not only to get bluetooth monitoring on my cell phone, I also now use this "plug-in" Victron charger as my main house battery charger when I am at an RV park with 3+ days of charging available... and I use the Victron also as a battery maintainer when I store my RV in the winter. (Works great!)

If you have a combo Inverter+Charger you just turn the charger off at the power panel inside your RV.

If your Inverter+Charger...charger works you can always use it a rapid charger when you only have shore power for 1 night and have to hit the road the next morning, but the slower you charge your batteries the better. This is why I rarely use my Dimensions-Charger. I.e., the Victron 17A will take longer, but if I have the time, as in 3+ days of shore power, then I will always use the Victron and it has "smarter" charging algorithms I hope will result on long battery life.

Note: The rule of thumb when it comes to how many amps you can charge your house batteries with safely is this: Don't exceed 25% of your total battery AH ratings. Example: My 4-6V-Golf Cart-GC2 batteries are 420AH of storage so according to this rule I can safely use a 100A charger. ...But that does not mean I should! ...Because the slower your charge your batteries the better.

As for testing the strength of your batteries: The best load test is to start with what you think is 100% SOC. That means you basically see 12.7V after 1 days of rest, if that's not too inconvenient, and then you simply run your microwave (with a glass of water inside) for 1-2 minutes, while you check the DC-voltage on your Power Panel.

==> A strong set of batteries will drop to lower voltages and then recover as soon as you turn the microwave off. ...And if if do this a few times you will see your volt meter read 1/10 of a volt less between each test. ...But a weak set of batteries will drop by 0.5V and stay there. ...And a very week set of batteries will shut the inverter down while you are powering your microwave.

There are other tests you can run on your battery cells using a hydrometer too, but sometimes heavily sulfated batteries will give you a favorable hydrometer test, but fail the microwave test.

When you have heavily sulfated batteries (1.5+ years old in my experience caused by poor re-charging techniques, freezing cool winter battery storage, lots of rapid battery charging without equalizing (which only occurs every 10 battery recharge cycles), then your batteries may test good, but fail the "microwave or hairdryer test" ...and that's the only true test that matters.

Last summer I refused to declare my house batteries dead, and I tested and tested, and over 1 month my recharge cycles became more frequent. This is another sign of battery sulfation and there is nothing you can to to recover a heavily sulfated battery.

...And you will know this to be true when you buy new batteries and everything works as normal.
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Old 02-17-2021, 11:12 PM   #5
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There is no problem with having an inverter and a converter both in your RV. Whomever told you this is simply taking some info and applying it across the board.

Converters convert 110v to 12v to run 12v items. And they take 110v and convert it to charge your batteries.

Inverter’s “invert” 12v into 110v. And SOME inverter’s are also battery chargers. Not all are, some are.

Older RVs almost all have converters and many also have inverter’s of the non-charging type.

In most cases an RV will not have both a converter charging its batteries AND an inverter with a charger to charge its batteries.

But it’s certainly possible, and not a problem, to have both a converter and an inverter on an RV.

I agree with the others your batteries are likely worn out and can’t hold a charge.
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Old 02-18-2021, 07:08 AM   #6
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Thank you, very helpful.
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Old 02-18-2021, 07:09 AM   #7
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Thank you
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Old 02-18-2021, 09:25 AM   #8
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Most common cause of electrical problems on Rv is the batteries and those can even be new batteries if they have been run down several times when stored. Even when we think we have all the small stuff turned off, there are almost always small items like detectors for propane and cO2 which are safety items and left on, The start battery can often be run down during storage due to the radios presets, etc..

so a battery that is six months old may still be a bad battery if folks let them run totally dead while stored, so first figure how to avoid that happening and also look at the condition of the current batteries.

No point in changing batteries if you are going to kill the new ones almost immediately, right?
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Old 02-24-2021, 05:50 PM   #9
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Inverter powering converter?

Something that's a possibility (however unlikely it may be) is that the inverter is powering converter when shore/generator power is not available.

If it was mistakenly wired that way, then it will create a "loop": Batteries > Inverter > Converter > Batteries. Because all of the above are not 100% efficient there will be a significant drain on the batteries -- even with no loads.

We have our MS2000 inverter/charger wired to feed the "whole house", so I made sure to disable the converter (it's no longer needed).
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Old 02-24-2021, 06:33 PM   #10
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Since reading all the replies, no one's asked the OP just WHAT MODEL of INVERTER he does have? If, by chance, he's got an Inverter/Charger on board, then need for a CONVERTER is not necessary. But, if his inverter is NOT an Inverter/Charger, then yep, the converter does the job of charging the batteries. A tad more info is needed before more accurate answers can be stated, at least in my opinion.
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Old 02-25-2021, 09:28 PM   #11
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The only thing to know is that the inverter will use power even when there isn't any load, so turn off when not needed. Disconnect the batteries and see if they hold a charge. DC fridge?
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converter, inverter

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