Using an AC battery maintainer along with PV array?

[smily03]

Is it possible to have a battery array hooked up to both an AC battery maintainer as well as a solar charge controller? The thought being that the maintainer would do a constant float, while the solar array would handle the actual charging from usage?

If you can do this, would you need to put diodes on the maintainer so as to not back-feed a higher voltage to the maintainer, etc.?

[Logan005]

I have done this with a wall plug timer, depending on your load times and conditions, you could use both to maintain a non cyclical battery charge state, therefore extending battery life. I have not had a problem with feedback with two smart chargers connected. You will however need to be hands on with this system, learning how to program the wall plug timer in association with your usage and size of your solar array. You will want a wall plug with multiable on/off options and or override the timer on cloudy days, to keep from cycling your batteries.

[Sunking]

No the higher order source is always the primary source. Any Charger already has diodes.

Your logic is flawed assuming your are using power. Say you have a 5 gallon bucket of water. You have a hole in the bottom of it, that leaks 1 gallon per hour. You Maintainer supplies 1 teaspoon of water per hour. How long does it take to empty the bucket?

Did you come up with 5 hours and few seconds?

[inetdog]

There is also the question of why you are using batteries if you have grid power.....

[organic farmer]

There is also the question of why you are using batteries if you have grid power.....

Maybe his grid goes down a lot. Mine does.

[Sunking]

Maybe his grid goes down a lot. Mine does.

Then you would not use Solar or especially a maintainer. Neither is capable of generating enough power in any meaning full time frame at any price. If you understood that you would not be using solar with commercial power available.

Industry certainly knows this why they use a UPS with generators. Because it has to work and be the most economical. Solar cannot compete in price or availability. You cannot fill a lake with a 6-pack of beer and peeing in the lake.

[SunEagle]

I like that 6 pack filling the lake analogy. I might use it myself but will give you the credit.

[organic farmer]

If the OP does not have reliable grid power available, perhaps the OP is seeking alternatives.

There is no need to be insulting.

I opted to be off-grid with the option of using the grid as a backup for those days when the grid happens to be up. It makes sense in rural America.

If you have the money to throw at a more expensive net-metering system, go for it. Waste your money.

As for the OP's situation, be nice to these people. They come here seeking help.

[Sunking]

As for the OP's situation, be nice to these people. They come here seeking help.

I am. I told him exactly where the Flaw was in his logic. You cannot charge a battery with a Maintainer any more than you can put out a forest fire by pissing on it.

[organic farmer]

Assuming you have a solar array to run things during the day and to charge your battery.

Then at night, if the POS power grid manages to be up on a particular night, it can trickle charge the battery. No harm, no foul.

How often does anyone expect the grid to be up anyway? [unless you are urban]

[smily03]

Totally understand about not being able to actually charge a battery using a maintainer Sorry, I guess my initial post was a bit less clear than it was in my head.

I was basically thinking about using a maintainer to float, so that when the sun went down, the batteries had a continual source of float voltage, rather than doing a microcycle from self-discharge overnight. But, then use the PV to do the actual charging of the batteries. So they'd basically layer one on top of the other.

To that end, regarding Sunking's first post - would the PV be the higher order when it's online during the day, since its voltage would be higher? Or would the TriStar get confused by that and not try to run?

Not planning a huge battery plant at all, basically just want to be able to keep my server (odroid u3,) router, environmental control stuff, etc. online during the power blips we have pretty regularly. (We have multi-hour outages fairly often too; have a genset to power the fridge, furnace, etc., but don't want to have to run a genset continually to power a 20-watt DC load during a power outage...) Right now have two small 7AH SLA batteries and a PicoUPS-100 to cover the brief blips, but that only lasts for a few minutes at this point because the batteries are getting pretty old.

More than anything, my whole PV project is a way to get me out of my IT box and thinking about other things that I enjoy - electronics, etc. Basically, giving me the opportunity to learn a lot about other things that I don't encounter in my day-to-day life unless I do it intentionally.

[Sunking]

I was basically thinking about using a maintainer to float, so that when the sun went down, the batteries had a continual source of float voltage, rather than doing a microcycle from self-discharge overnight. But, then use the PV to do the actual charging of the batteries. So they'd basically layer one on top of the other.

No harm in that so long as you understand what a Maintainer does. Unfortunately terms used with Battery Chargers are very confusing brought on by Marketing. Basically there are are only two modes of charging any battery of Constant Current and Constant Voltage. In the frame work of your question we have Maintainer, Float, and Trickle which are Constant Voltage modes.

To that end, regarding Sunking's first post - would the PV be the higher order when it's online during the day, since its voltage would be higher? Or would the TriStar get confused by that and not try to run?

The PV system assuming it can supply more CURRENT

Not planning a huge battery plant at all, basically just want to be able to keep my server (odroid u3,) router, environmental control stuff, etc. online during the power blips we have pretty regularly. (We have multi-hour outages fairly often too; have a genset to power the fridge, furnace, etc., but don't want to have to run a genset continually to power a 20-watt DC load during a power outage...) Right now have two small 7AH SLA batteries and a PicoUPS-100 to cover the brief blips, but that only lasts for a few minutes at this point because the batteries are getting pretty old.

OK that is helpful and there is a better way to do this. A simple UPS. It can be a commercial solution or a homemade solution. In fact the homemade solution is not only less expensive, but more effective and tailored to your needs. You do exactly what the prods would do. You select a rectifier that is sized to supply the load and recharge batteries quickly. You size the batteries and type of battery to meet your requirements. All that is missing is the Inverter you select to run your mission critical loads. From what you are talking about would be very inexpensive, and extremely effective. You would be making what is called a Dual Conversion UPS, AC>DC>AC.

OK I used one of those confusing words, RECTIFIERS. A rectifier is just a FLOAT Battery Charger. So let's make a model system. Let's say you have a 20 watt load, you want to run say 5 hours per day on battery keeping cost low as possible. We start with the battery and such a small system only requires 12 volts. You only want 100 watt hours per day from it, so we only need a 400 to 500 watt hour capacity battery which works out to a 400 wh / 12 volts = 33 AH up to 500 wh / 12 volts = 42 AH. So go shopping for a 12 volt 40 AH battery and budget $75 to $100 for the battery.

For the charger or Rectifier we want to be able to run the load and charge the battery at the same time. We want it to be able to recharge the battery in 8 hours plus run a 20 watt or 1.8 amp load. The minimum size is [40 AH + 1.8 AH] / 8 hours = 5..225 amps. You are looking for a very inexpensive 5 amp 12 volt battery charger. Budget $50. Guess what a 12 volt 5 amp Battery Tender would work great.

Last piece is a Inverter to power your 20 watt load. You are looking for a 50 watt Pure Sine Wave Inverter. Budget another $30 to $50.

Total is less than $200.

What can it do? Well daily 5 hours standing on its head with one arm tied behind its back. In a pinch can run roughly 20 hours before you have to plug it into the generator you already have. No solar system can even come close to competing with it both performance or economically. That is what a pro would do and does do.

What is not to like?