Add DC charger or power supply to 12v system

[TonyVov]

Running out of power and don't have the $$ to add storage. Is there a way to incorporate a DC charger/power supply safely?
For example can the charger be added on the PV panel side??

Project is a composting toilet block at a school in Indonesia. Solar PV system to be used as example and education for students.
System includes 3 low watt fans and 5w DC lights, 3x200W solar panel, EPSolar TRACER3210A charge controller and an 80aH 12v Deepcycle Gel battery.
The EP Tracer controller has separate connection for loads and for battery

In normal use only fans are used with about 2-3 hours of lighting. But when the sun doesn't shine or lights are turned on in daytime power consumption goes through the roof and the system dies.
I want to save the battery from Extinction.

We tried putting a 10A charger directly to battery and burnt it up. I suspect the combined load of discharged battery and building loads (7a max) exceeded the charger capacity.

If I get a bigger charger I believe the battery will get too much charge rate with 2 controllers on the battery.

Is it feasible/crazy to add the DC supply on the PV panel input? I was planning to use a simple timer switch to control the amount of extra DC power.

This way the Tracer would manage the battery directly.
The Tracer is an MPPT charge controller, we are using 3xGE200W solar panel In parallel to the system, we might take one off depending on testing results.

I would have thought this was a common scenario for an RV at a trailer park, when loads are running, sun is shining and the battery needs to get more charge.

Key question:
Is there a 'good' or safe way to add extra DC power to this system without breaking the budget.
Our charge controller was 300$, the battery 300$ and the rest free from another project.
I believe adding 2-3 more batteries would fix the issue but we don't have the budget.

As example a 24v DC supply 5a has almost the same voltage output as my panels, it would give close to enough power to drive the system could it be hooked up in series to the PV panel input of the Tracer controller ??

[Mike90250]

If your system burnt up a battery charger, a smallish DC supply will not last as long. What do you power the charger / DC supply from ?

[TonyVov]

Mike, thanks for replying, we have plenty of 220v 50hz power at the site. This off-grid building was assembled to demonstrate and educate school students on renewable energy components and planning. I'm going to bore you with some details....
========== Skip to bottom for my question=====
We recognized that there was not enough energy from the battery for an 'autonomous' system for 24hrs so added the 10 amp DC charger on battery side as backup, this should have been enough to power the loads (7amp max) if needed and still feed the battery. Plan was turned use timer at night at least.
During installation before the Solar controller was even installed the charger burnt.I suspect the battery was drained by loads and then connected to charger with loads still turned on.
I can easily buy a bigger charger but think when the system is finally working this will cook the battery.

Our loads - max 7 amp ; 'average' 2 amp on 24hr basis
- 3x small circulation fans 1amp on 24hr for compost system
- main wash room lights 3 amp on for 2-3 hr at night
- Cubicle lights on proximity switch 3 amp on demand at night
Estimate 475 wh per day

Our Solar MPPT charge controller EPEver XTRA3210N is 30amp with full PV, this is already a bit much for our battery.
We actually have 4 panels available but will use either 2 or 3, 200w 54cell GE Poly panel. The controller was selected as it allows 'excess' PV power and limits charge power to Max output.
Estimated Solar 1200wh/day from 2 panels (plenty of power for charging but we have nowhere to put it).

Our Battery is ICAL LIP1280G VRLA Gel Deep cycle 12v 80ah
Constant Voltage Charge. 13.5min 14.4-14.7 Recommended
≠===≠============= question below========

My thought was to avoid multiple charge controllers on a single battery why not connect a DC power supply on the same input as the Solar panels to our Solar Controller ???
Our GE solar panel have 26v @rated power.
If I connected for example a 5amp 18v DC supply through a blocking diode it would only supply power to the solar controller when the sun went away.
It's a bit of a crazy idea but with this setup there would be only one charge controller connected to the battery and the DC supply is simulating a low performing 'panel' to keep the battery alive during the night and on cloudy days through the Solar Charge Controller.

If there is some better way to incorporate a medium to low (5-10a) battery charger into the system I would be interested in suggestions.
If we keep things running with battery abuse as now the battery life will be very low and the education opportunities to balance power in/out and storage calculations reduced.

[Sunking]

Mike, thanks for replying, we have plenty of 220v 50hz power at the site. This off-grid building was assembled to demonstrate and educate school students on renewable energy components and planning.

How is that working out trying to brainwash kids?

[Mike90250]

You need a beefy charger designed for real loads. Iota makes them - here's what I suggest:
https://www.iotaengineering.com/dls15.htm use the 13.6V setting, 14.2 will cook your battery

Don't bother with toys, unless you like replacing burnt up ones. No diode needed. I'm gonna smack the person passing out diode information, with a 2x4, since the mid 90's diodes are all integral with solar. Only speak of diodes if you burned one out and are replacing it.

[J.P.M.]

How is that working out trying to brainwash kids?

I'd not necessarily call it brainwashing. These efforts, while I'm sure well/best intentioned, may attain some unintended outcomes in terms of what is learned.

Look at what's going on. Seems like there's a lot of 1st world tech being used for a 3d world toilet. There might be something to be said along the lines of this being a lesson in not using more than what was once called appropriate technology. Students may well learn a fair amount about electronics from the current attempt, and that's good. But someday, maybe sooner than later (but
I hope much later) they may also learn KISS as it may apply to serviceability and cost of maintaining something that's more complicated than necessary to accomplish a task.

I've used outhouses - a fair amount. An appropriately sized, placed and screened vent at the top eliminates the need for a fan, at least for non-snowflakes. A flashlight or even a lamp works just fine in the dark.

Throwing what's reads to me like relatively high tech and maybe inappropriate tech. at what I'd guess is a thought to be appropriate and perhaps laudable tech. application like a composting toilet has me shaking my head. Seems inappropriate to me, but that's just my ignorant and uninformed opinion I suppose. Just looks like overkill to do so.

But, the (perhaps) unseen advantage: The fancy bells/whistles can't or won't be maintained or replaced for any number of reasons can be a valuable lesson on using more appropriate technology for the situation. That might not have been one of the goals of the project.

Just my $0.02.

[Mike90250]

When the existing battery fails, replace it with a pair of 6V golf cart batteries, cheap and rugged.

[Sunking]

I'd not necessarily call it brainwashing. These efforts, while I'm sure well/best intentioned, may attain some unintended outcomes in terms of what is learned.

You are right JPM, my bad and I apologize to the OP. I have an issue or two with our education system that I witnessed back in 2003/2004. Actually taught Trig and AC circuitry at a local college and seen first hand Social Engineering. I broke the rules, I failed students. Turns out you cannot do that as it might hurt the little snowflakes feelings. Wished I knew that when I went to school. Hated getting up some mornings to take classes or test.

[J.P.M.]

You are right JPM, my bad and I apologize to the OP. I have an issue or two with our education system that I witnessed back in 2003/2004. Actually taught Trig and AC circuitry at a local college and seen first hand Social Engineering. I broke the rules, I failed students. Turns out you cannot do that as it might hurt the little snowflakes feelings. Wished I knew that when I went to school. Hated getting up some mornings to take classes or test.

Understood.

Well, probably not as right as much as it's just one opinion. My poorly stated point was that lots of tech, whiz-bang stuff that's more complicated than need be for a task will be shown not appropriate when it all breaks down sooner than simpler and more appropriate systems, and also because it's more complicated than can be maintained in a 3d world infrastructure. Make things no more complicated than necessary to accomplish the goals or can be maintained. to do otherwise is a waste that feeds only con men and egos.

I have a good friend who knows a lot about R.O. systems - lives & breathes them like I used to be w/power boilers. Anyway, we had to almost throw a rope around him about 25 yrs. ago to unconvince him that while clean drinking water is a laudable goal in, say, parts of Africa, it would be an inappropriate application where the infrastructure didn't (yet) exist to support the technology.

His ego was in the way of his common sense.

[TonyVov]

You need a beefy charger designed for real loads. Iota makes them - here's what I suggest:
https://www.iotaengineering.com/dls15.htm use the 13.6V setting, 14.2 will cook your battery

Don't bother with toys, unless you like replacing burnt up ones. No diode needed. I'm gonna smack the person passing out diode information, with a 2x4, since the mid 90's diodes are all integral with solar. Only speak of diodes if you burned one out and are replacing it.

Mike - many thanks for advice - this was the size of charger I was considering too based on my realization that with a flat battery one needs to consider that a "load" on the battery charger in addition to the building power loads. As we are in 220V world I'll need a slightly different model.
I'm a little concerned to fry the battery with 2 controllers if they both kick in at the same time, I guess the operational thing is to limit the options to get a discharged battery. Our EPEver Solar controller will boost to 14.2V then goto float on it's GEL battery setting, there is a "user" mode which is accessible with some kind of cable setup - would you suggest to lower max boost charge voltage to the same setting as the charger??

[TonyVov]

I'd not necessarily call it brainwashing. These efforts, while I'm sure well/best intentioned, may attain some unintended outcomes in terms of what is learned.

Look at what's going on. Seems like there's a lot of 1st world tech being used for a 3d world toilet. There might be something to be said along the lines of this being a lesson in not using more than what was once called appropriate technology. Students may well learn a fair amount about electronics from the current attempt, and that's good. But someday, maybe sooner than later (but
I hope much later) they may also learn KISS as it may apply to serviceability and cost of maintaining something that's more complicated than necessary to accomplish a task.

I've used outhouses - a fair amount. An appropriately sized, placed and screened vent at the top eliminates the need for a fan, at least for non-snowflakes. A flashlight or even a lamp works just fine in the dark.

Throwing what's reads to me like relatively high tech and maybe inappropriate tech. at what I'd guess is a thought to be appropriate and perhaps laudable tech. application like a composting toilet has me shaking my head. Seems inappropriate to me, but that's just my ignorant and uninformed opinion I suppose. Just looks like overkill to do so.

But, the (perhaps) unseen advantage: The fancy bells/whistles can't or won't be maintained or replaced for any number of reasons can be a valuable lesson on using more appropriate technology for the situation. That might not have been one of the goals of the project.

Just my $0.02.

The system is much less fancy than it sounds except maybe for the use of proximity switch which are available on local market for $1.50c;
With upward of 400 users on a typical day this is not a "normal" outhouse, it is a showpiece, the clivus moltrum composting technique uses aerobic concept to encourage composting about 10 times faster than can be done anaerobically - hence the 12v fans (3x5w loads). The kids get to do a real time power balance calculation, do the solar installation themselves, then validate the calculations with real time measurements including sunny and cloudy days.
The next stage will be to take this tech to a nearby island that relies on genset power to demonstrate that low power (50-100w) solar can deliver value without the need for large scale 25 year capital investment.
I like one of the tips to look at golf cart buggy batteries as storage, our tourist market probably makes these a much more $$ competitive option than the deepcycle solar options in the local market.

[monogram]

Hi Tony,

I thing I had a similar setup as yours with bigger battery:
- 30A EPEver charge controller
- 2x315W in parallel
- 4 x 6V/215A goft cart battery
- load ranging from 90 Wh up-to 260 Wh (with 90Wh @ 24x7)
- Daily usage at about 2.9kWh while solar generated at about 3.4kWh

When the battery voltage get down to 24.1V then the CC will shutdown the load and an AC voltage will kick on (using an add-on relay) to continue supply the voltage for my load.
When the battery reach 24.6V then the CC will turn ON the load while add-on relay will turn off the AC voltage.

I think you can do the same setup for your system with 12V setup.

Your battery is so small compared with the solar output, to harvest all the power that generated by your solar, I would recommended adding another battery otherwise any excessive power from solar will generate the heat on your CC. (keep your CC cool with a computer fan)

Side note, you can do a custom setting on your CC under "user" setting with MPT50 or a computer+USB/RS232 adapter.

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[Mike90250]

Don't worry too much about 2 chargers over charging the battery. Stick with the Iota brand, in the model/voltage you need

[TonyVov]

Hi Tony,

I thing I had a similar setup as yours with bigger battery:
- 30A EPEver charge controller
- 2x315W in parallel
- 4 x 6V/215A goft cart battery
- load ranging from 90 Wh up-to 260 Wh (with 90Wh @ 24x7)
- Daily usage at about 2.9kWh while solar generated at about 3.4kWh

When the battery voltage get down to 24.1V then the CC will shutdown the load and an AC voltage will kick on (using an add-on relay) to continue supply the voltage for my load.
When the battery reach 24.6V then the CC will turn ON the load while add-on relay will turn off the AC voltage.

I think you can do the same setup for your system with 12V setup.

Your battery is so small compared with the solar output, to harvest all the power that generated by your solar, I would recommended adding another battery otherwise any excessive power from solar will generate the heat on your CC. (keep your CC cool with a computer fan)

Side note, you can do a custom setting on your CC under "user" setting with MPT50 or a computer+USB/RS232 adapter.

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Dear Monogram, your solution was exactly what I was thinking about when I was reading the manual. Using the EPEver disconnect/dropout of loads to make/break the charger connection.
I'll follow Mike suggestion for charger selection and size but would be much happier if I could locate an addon relay as you use.
Unfortunately this might kill my other plan which was to use the EPEver internal time switches available on the load side of circuit to only have my lights see power at "night".

So far I don't know how this controller determines sunset and sunrise, it does not seem to be a setting. I guess it somehow learns it over time.
Thanks for the feedback

[flipperman]

I don't play golf but would a golf cart buggy batteries be flood batteries? and omit gases and acid? your sealed Gel is way safer around kids. What your planning sounds like you only need a battery box with a larger AGM around 125AH and a smart charger just for backup in overcast weather. If it's a teaching thing why not learn how without mains at all. Cheers Phil