using a solar charger to regulate battery? - Fiberglass RV


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Old 03-09-2016, 09:51 AM   #1
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using a solar charger to regulate battery?

Another hypothetical question. If one wanted all power sources to run though the same charger, what is the best way to accomplish this?

I was wondering if it is electrically sound to use a 12v regulated power supply to run the trailer off of mains and then to run it though a step-up transformer to emulate a solar panels voltage and feed it through a solar charge controller that manages the battery.

The idea would be that the trailer would have a solar panel and this 12v converter and both would run though one charging system.

To be clear this is a question not a plan... I kinda want to take some electrical engineering classes. I think I am in the realm of just knowing enough to be dangerous (:
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Old 03-09-2016, 10:20 AM   #2
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I wouldn't want to customize the power system to the point that repair parts would be difficult to find while on the road to Timbuktu. Most solar controllers are sized to match the maximum panel output, which is a big variable compared to a constant voltage level from your existing (non-solar) converter plugged into AC.

Sounds like your plan has a single point of risk/failure, and a fair amount of up/down voltage conversion losses.
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Old 03-09-2016, 10:31 AM   #3
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I talked to the guy at Bogart about his system and asked this exact question and He said he couldn't think why not.
Here is a link to his site:
TriMetric Model Descriptions, Present and Past | Bogart Engineering
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Old 03-09-2016, 10:41 AM   #4
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KISS???

Hello,

I would not run the power from AC converter through the
solar controller. You could make it work but the cost of
stepping up the converter voltage to be able to use it
through the solar controller is not worth it. Also, most
AC converters have a much higher current (Amps) output
than the panels you will have. The higher capacity solar
controller would be much more expensive. It seems to
me that the old saying of KISS would apply here.

Larry H
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Old 03-09-2016, 10:45 AM   #5
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It seems like there are quite a few cheap and highly efficient voltage and or current regulators out there, I think often 95%... they are really cheap actually. For some reason I have a suspicion that the advances in voltage and current regulation have lead to the mppt charge controllers I am seeing now
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Old 03-09-2016, 10:49 AM   #6
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What is the simpler way? Thats kinda the issue I am having...
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Old 03-09-2016, 10:54 AM   #7
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If I use a regular camper converter it would not be integrated into the solar set up. Wouldn't they have to be separate?

If I have multiple chargers / charging inputs that are independent I wouldnt know how to isolate them safely without manually switching from mains to solar and back
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Old 03-09-2016, 11:21 AM   #8
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Multiple charging sources are not a problem. Those with full time solar at times will have at least 2 charging sources at the same time, the tow vehicle and the solar. With a converter running and solar two sources. My advice is to just add the solar and not worry about it.
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Old 03-09-2016, 11:41 AM   #9
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Somebody that knows, would a solar controller sense a higher input (backfeed) from another source and just shut down?
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Old 03-09-2016, 11:49 AM   #10
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If you want to, check out the latest edition of Trailer Life.
They have an interesting article on solar panels integrated with lithium batteries.
The main item I saw, was at the end of the section on installation, $12,000.00!!!!

But, an interesting thing that is rarely brought up, when performing a major system modification or DIY installation, is the impact upon your insurance.

The fine print can really lead to a bummer of an experience.

Just saying, ya' know.


In closing=====Always remember, "wheels down and brakes off when landing"!!
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Old 03-09-2016, 12:27 PM   #11
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I invested my money in a solar system that provides power for all of my 12 volt needs and some of my 110 volt needs. I disconnected the converter and the sun provides power for almost everything. (Not the air conditioning or heat) I did go to 2 - 6 volt Trojans to store the necessary amount of amperage to do the job. Bogart provided the charge controller and battery monitor and they work great. We have been on the road since Christmas Day and dry camp whenever possible. The lowest I have seen the monitor was 78% charge and we don't even think about it. Our favorite site in the US is dry and we stayed there 8 days and would have stayed longer if the black tank was bigger. Invest in solar and don't worry about converting.
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Old 03-09-2016, 12:41 PM   #12
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Quote:
Originally Posted by Ironhinge View Post
Another hypothetical question. If one wanted all power sources to run though the same charger, what is the best way to accomplish this?

I was wondering if it is electrically sound to use a 12v regulated power supply to run the trailer off of mains and then to run it though a step-up transformer to emulate a solar panels voltage and feed it through a solar charge controller that manages the battery.

The idea would be that the trailer would have a solar panel and this 12v converter and both would run though one charging system.

To be clear this is a question not a plan... I kinda want to take some electrical engineering classes. I think I am in the realm of just knowing enough to be dangerous (:
I am assuming that by a "12V regulated power supply" you mean a supply designed to power radio or similar equipment with a regulated output of around 13.8V at 20 or more amps. If so then you could simplify your planned system considerably by eliminating the step up "transformer" from your design.

I am using a system similar to what you describe to provide DC power in my EggCamper. The main AC/DC converter is a Samlex SEC1223BBM power supply with a regulated output of 13.8V +/- 0.2V at up to 23A and terminals for connecting an external battery. This is a power supply commonly used to power ham radio equipment configured for emergency battery backup and is available from stores such as Ham Radio Outlet or Radio Dan.

With 120V AC supplied the Samlex supplies the coach DC buss with 13.8V DC and, when AC power is lost, the output buss is automatically switched to the battery. When AC power is restored the Samlex again automatically switches the coach DC buss and the external battery is charged at up to 4A. The external battery connections go to a 100AH flooded lead-acid battery, paralleled with the output of a solar panel regulator.

This system has been in use for several years now with no problems.

If you have further questions or my system description is lacking in detail send me a PM.

BTW - a transformer is an AC device that would not be happy with a DC input.

73 Orlen
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Old 03-09-2016, 01:11 PM   #13
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Orlen, that sounds almost exactly what I was hoping to do! I liked the idea of a well regulated output because it would theoretically drive leds better and switching would make use simpler.

I’ve been leaning on the side of solar chargers because i think the system could be stepped up to chargers with more intelligent battery management (like thermometers) and if you were putting power in though the solar charger on sunny days the battery would be charged partially from the panels

I looked it up but cant quite be sure, is the Samlex what you might call a smart charger? I didn’t see anything about its battery management. I feel like I have become obsessed with intelligent charging.
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Old 03-09-2016, 01:35 PM   #14
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Larry, I like the Idea of your solution...

I think I have headed down this charge controller direction because I really want to invest in solar. I have been trying to figure out a way that it can be the primary system but can be supplemented with shore power. Maybe the trick would be to build it so it won't need to be supplemented
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Old 03-09-2016, 01:42 PM   #15
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Have you looked at the "theory of operation" section of the manual? It has a good description of the charging circuit operation.

The charging circuit of the Samlex is not designed for rapid charge or equalizing charge but seems to do well at charging my battery. I have a 31 series 100AH flooded lead-acid battery that is now 6 years old and has been used extensively over that time. It still tests at about 85% capacity.

In my opinion most of the "smart chargers" are not as smart as they let on to be. It's mostly advertising hype. As long as you maintain the battery - clean, test and add water when necessary it will give you good service.

I do use an intelligent battery charger/maintainer on batteries in storage at work but these are high capacity AGM (as in high $$$) batteries in long term storage while the project is being moved. And at $700 for the multi-battery maintainer it would be out of the price range for "normal" use.

I think the Samlex supply or something very similar is the best bang for the buck for an RV electrical system, at least if you are building up your own system. And if you hardwire the solar charge system in you will always have a float charge going to the battery, at least as long as the sun keeps shining.
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Old 03-09-2016, 01:43 PM   #16
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Orlen, If you have a chance could you describe in more detail "The external battery connections go to a 100AH flooded lead-acid battery, paralleled with the output of a solar panel regulator. " I would P.M. but I think your answer will shed light on other responses I have already received
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Old 03-09-2016, 02:02 PM   #17
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I think you have a good point on the "smart chargers". The more I have looked into them the more there seems to be a lot of branding and hype... I liked the idea of the solar direction because it is, in a way, the cheapest route into high quality battery bank management like as you describe with the AGM's at work. It is also a good point that regardless, your battery receives a float charge from the solar controller.

Although it sounds like it is unnecessary from your experience, if someone with a setup like yours wished, they could protect the battery from overcharge during long-term storage by disconnecting the 4a from the simplex.
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Old 03-09-2016, 02:14 PM   #18
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oh and upon closer inspection as you say...

cHARGinGAnD BAcKUPoPeRA (how it copy and pasted)

n
Charging current will be proportional to the discharged state of the battery and is limited to maximum of 4A when the battery is completely discharged (Standing Voltage of 11.4V). The current will taper down from 4A as the battery gets charged and its voltage rises. When the battery is fully charged, the current will drop down to 0.1% of the Ah capacity of the battery to compensate for self-discharge. When fully charged, the voltage at the Battery Terminals (5, 6) will be the float Voltage of 13.8V 0.2V"
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Old 03-09-2016, 02:15 PM   #19
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sounds just as smart if not more so than the others
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Old 03-09-2016, 03:07 PM   #20
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You can only transform AC . You cannot transform DC
IE: There is no such animal as a DC transformer !!
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