charge controller vs battery charger on the converter

[wallnut1234]

Ok so I'm taking the plunge and decided to go down the solar rabbit hole. I own a 1989 17 foot bigfoot that already has a converter with battery charger (model 6332). I ordered two 170 watt bougerv panels along with a 40A renogy mppt charge controller. Since my converter currently charges the battery, I'm wondering how I should set things up when I'll be hooking up the charge controller, I presume I will need to disable the battery charging function of the converter and only use the charge controller to do the battery charging? If so, can I connect the converter to the charge controller in order to charge the batteries while connected to shore power? What are the most common setup for this?



Thanks

[patrick crawford]

wallnut,

on my casita i have both solar and the trailer's converter charging option. my solar panels are routed thru morningstar controllers. the built in converter also charges. both go to the battery. i have 3 options, charging via solar, letting the trailer's converter send electrons to the battery and both at the same time. the only issue you might have is if your converter doesn't know when to throttle back by sensing the input of the panels (at the battery). maybe all converters need to have that feature? i would suggest that you wire the panels so they can be easily disconnected and have a battery disconnect switch somewhere between the battery and the trailer's converter. not totally necessary but it does make life simpler when you need to work on things electrical.

p@

[ZachO]

I very, very rarely plug in, so my panels go to the controller, then battery. They’re basically on their own circuit, independent of the charge controller and power center, and so they have their own fuse. There’s nothing wrong with this.

The problem Patrick brings up is that with old model trailers like yours, the converter/charger is pretty rudimentary, and pretty old. They’ve been known to fry batteries by not recognizing its full and continuing to charge.

If you regularly plug in and you feel your charger doesn’t over-charge your battery, you’ll be fine. Both the solar charge controller and the converter/charger are doing the same thing - sensing the battery level and applying the correct amount of charge.

I think personally I’d use a switch to turn off the solar while I was plugged in. Well personally I just avoid plugging in But having both going at the same time is redundant.

Some people have bypassed the converter all together. This means when they’re plugged in they’re running the AC outlets from shore power but DC appliances off the battery. Pretty simple.

[Raspy]

Zach is on the right track here.

There would be no problem with both charging systems connected to the battery, if the old converter was a smart charger.

The solar charger is a smart charger and, as long as it can keep up with the load, would be better for the batteries. Maybe, as suggested, a switch on the DC output of the converter would be a good idea. This would allow smart solar charging, AC operation in the trailer, and a 12 volt power supply if needed. Or get a cheap smart battery charger and connect it to the battery alongside the solar controller connections. Then just disconnect the converter 12 volt output completely. The battery charger and the solar charger should play well together while hooked up in parallel at the battery.

[redbarron55]

Many if not most controllers do not want to have the battery load disconnected or damage to the unit may result.
If you disconnect the solar perhaps disconnecting the panels is the proper thing to do.
This still leaves the question of interference between systems to be investigated.
I have my solar system with a Epever 40 amp MPPT connected directly to the battery and I have the charger from the Progressive dynamics also is paralleled across the battery. The output from the Epever MPPT 40 is routed to the PD distribution buss for individual circuit protection.
The way I see it is the charger with the highest voltage out is the winner and carries the load (if any) and the question would be in the 4 stage charging who is deciding the voltage and current at any given time?
So far I have had no problems, but like any lead acid battery system you have to regularly check the acid level in the battery.

[ehoepner]

On me casita 17ft SD I run the solar charge controller in parrilla of the converter.
No problems.

[chrisblessing]

In addition to the above concerns, I wonder what sort of battery you will be charging. If you have, or will, switched to lithium (most likely lithium iron phosphate) your converter likely won't have the appropriate charging profile. I solar-charge a LiFePo4 battery and cannot use my older converter for charging. My simple and inexpensive work-around in this case is to use a modern AC > DC lithium charger connected to the shore-power AC.

[wallnut1234]

Yeah I think that so far I'm leaning towards only using the solar panels to charge the battery and disabling the battery charging part of my old converter, that along with a regular charger to charge when I have shore power but no sun.


What do you guys think of replacing that old converter with something that would have a converter, inverter and charger (if anyone has a recommended make and model that would be great). I figure it must not be that hard to swap.

[John in Santa Cruz]

converter/charger, sure. never seen one with an integrated inverter.

kinda hard to disconnect the converter from the battery part, since both the battery and converter output have to be hooked up to the 12V DC stuff. I guess you could use a battery disconnect switch

[wallnut1234]

Originally Posted by John in Santa Cruz

converter/charger, sure. never seen one with an integrated inverter.

kinda hard to disconnect the converter from the battery part, since both the battery and converter output have to be hooked up to the 12V DC stuff. I guess you could use a battery disconnect switch

Yeah I don't really know what I'm doing here, I though that recent ones would have everything I needed (converter, inverter, charger). I'm starting to regret not buying a bluetti that does have everything I need.


So I think for now I will have to disconnect the battery when plugged in to avoid having the old charger fry the battery (lithium), when I'm not plugged in, I will only have DC. (I dont have an inverter).

[chrisblessing]

Originally Posted by wallnut1234

Yeah I don't really know what I'm doing here, I though that recent ones would have everything I needed (converter, inverter, charger). I'm starting to regret not buying a bluetti that does have everything I need.


So I think for now I will have to disconnect the battery when plugged in to avoid having the old charger fry the battery (lithium), when I'm not plugged in, I will only have DC. (I dont have an inverter).

Upgrading the charger to one that features charging profiles for all types of batteries would be ideal, but expensive. That said, keeping the old charger will give you continued access to shore power and current for your 12v lights and accessories. I'm my case I purchased a $40 lifepo4 charger for those occasions when I lack sunshine.

[John in Santa Cruz]

re: inverters, for light use, like charging my wife's laptop, and some bluetooth speakers we have that use a 120V to 19VDC charger, I have a portable '300W' inverter (really only useful for < 200 watts), that I put a 'powerpole' connector on, and I've installed a couple powerpole jacks near the dinette, wired into their own 30A fuse.

[Tony D]

I’m curious about this idea of simultaneous shore power and solar. How many people do it this way? Seems that a relay to disable solar if hooked up to shore power would be an approach. Or a simple switch to throw before plugging in. I thought solar was mainly used to keep the battery charged when camping without hook up.

[chrisblessing]

Originally Posted by Tony D

I’m curious about this idea of simultaneous shore power and solar. How many people do it this way? Seems that a relay to disable solar if hooked up to shore power would be an approach. Or a simple switch to throw before plugging in. I thought solar was mainly used to keep the battery charged when camping without hook up.

I believe this would only be an issue if your solar charging apparatus were incompatible with your shore power charging. Typically your battery can accept a charge from both the converter and solar charge controller. When fully charged the battery will no longer accept power from the solar charge controller. The complication arises when the shore power converter cannot properly charge a certain battery chemistry which may result in an insufficiently charged battery.

I separated my solar from the converter as my older converter cannot charge LiFePo4 batteries. So when I am on shore power the converter can do everything except charge the battery. For those instances where I need to supplement the solar to charge the battery, and when I am connected to shore power, I use an appropriate battery charger plugged in the camper's AC to charge the battery. It works very well and is simpler and more cost-effective than changing the converter.

[Jon Vermilye]

There are quite a few inverter/chargers, however you would still need to install a 120V & 12V distribution panel.

[John in Santa Cruz]

Originally Posted by Tony D

I’m curious about this idea of simultaneous shore power and solar. How many people do it this way? Seems that a relay to disable solar if hooked up to shore power would be an approach. Or a simple switch to throw before plugging in. I thought solar was mainly used to keep the battery charged when camping without hook up.

That's the way most all RVs with permanent solar are wired, if the solar putting out slightly higher voltage than the power converter, the solar will do the charging. If the power converters voltage is slightly higher than the solar voltage, then the power converter will do the charging. the batteries are perfectly happy with that setup and both power converters and solar power controllers are perfectly happy wired that way.

[South Coast Stu]

I use a Perko switch like this to isolate the batteries:



When I'm boon docking and on solar (just 100W) I set to either "1", "2" or "All". Bank "1" is a G27 lead-acid, Bank "2" consists of 3 lead-acids (2 G27 & a G24).

If I'm on either generator or shore power I set to "Off" so the batteries are isolated from the factory "dumb" charger. I have a NOCO Gen4 (4 bank) smart charger that either plugs into the generator or shore power. In this mode the factory converter is only supplying 12V to the appliances and the shore power (or generator) is supplying 120V to the other appliances.

Used the set-up on a few week long excursions and really like the results so far

[Tony D]

Thanks all. Very interesting solutions. I guess it boils down to knowing what you got on hand. I understand that the latest converters allow the solar panels to be wired in parallel. Older technology or more complex arrangements would necessitate some protections or operator involvement. I totally get cost and/or ease as important factors in the chosen solution.

Sorry if I highjacked the thread, I think that I was on topic though.

[Raspy]

My Black Series came with an inverter/charger as it's electrical system. When plugged in, it passes power straight through to the wall plugs, and it also charges the battery with a three stage charger. When unplugged, it provides 120 volts to the wall outlets from its internal inverter, powered by the batteries. It is the best way to do these functions that I know of, and I set my boat up the same way. The switchover is invisible. And it can be switched on or off from a remote panel, or switched to only charge and not invert.

I just upgraded that inverter/charger to a Victron inverter/charger. It does the same thing but is better quality and more efficient than the Aims that came with the trailer.

The solar is also connected to the batteries and is always left connected. My batteries are four 100 AH AGMs. The solar controller is an MPPT Epever controller. Either system or both can be charging the batteries at the same time. They are independent, but both always connected and on.

Remember, each controller is simply looking at the battery's state of charge, and adjusting its charging scheme accordingly. If one charger is charging, the other will see the battery as at a certain level of charge, and adjust accordingly. The controllers are simply looking at the voltage at the battery terminals and adjusting their programming accordingly. The net result is the battery comes up to full charge from some combination of the two chargers that they work out between themselves.

The inverter/charger is so much simpler and so much better than the old fashioned converter and transfer switch system. And light years ahead of the old constant voltage output converters. It is seamless and all in one box. It is programmable for different types of batteries, is pure sine wave, and switches so fast that appliances and computers don't notice the switch from shore to batteries.

I don't understand all the fuss about connecting solar and the charger at the same time, unless the converter is sending so much constant current that it is damaging the batteries. More modern three stage converters, like the Progressive Dynamics, play well with solar too. I recently installed three Battle Born batteries in my friend's Oliver. We also installed a Victron MPPT solar controller. They are both continuously connected to the batteries. Shore power or not. The only small issue was that the PD charger did not exactly match the Battle Born ideal charging regimen, in that it's peak voltage was not quite the ideal. But the solar controller was right, so we left it alone and it works fine. In other words, the solar made up for the small difference.

I don't understand how having two smart charging systems, connected to a single battery bank, can cause overcharging. Each one of those chargers decides what to do based on the battery voltage and current absorption rate. That information includes what the other charger is doing at the time. So, it seems likely that one will take over at some point, but that is not a bad thing either.

[Markz]

You want a CTek ds250