Battery charging

It's common practice to wire 12V batteries in series. The hardest bit is getting the right cable and gettign the polarity right. Use two identical batteries: same make and model, and as much as possible, same history.

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what complexities?

what's hard about that?

NT

A 12 volt battery is a series connection of 6 cells. Not complex.

For the same reason that you can get 12V batteries cheaper than 24V, you can get cheaper 12V chargers. As long as you have isolated chargers, hook them up individually and the batteries in series.

More college project? For your solar tracker college project?

Two same-mfg, same design specs 12V lead acid batteries in series can be safely treated as a 24V battery. Your price point would seem to be unrealistic.

The thing is that I want to charge the batteries via solar power. Can I use the 24 charger available in the market to do it or do I need to build a charger from scratch to do this?

erica

The thing is that I want to charge the batteries via solar power. Can I use the 24 charger available in the market to do it or do I need to build a charger from scratch to do this?

erica

It's your choice. Buy one or make one. There's heaps on ebay of all types from simple to complex.

What more hints are you going to give later on, or was this it?

Then you need a maximum power point tracking charger to ensure maximum output from your solar array.

joe

If the panels are sized right then you can get by without any fancy charger electronics, just connect panels straight to the battery! Next rung up the complexity ladder is to research "solar shunt charge regulators".

piglet

This "project" is all over the map. The MOST important part of any project is the plan. You either want to charge by solar or you don't want to charge by solar. MAKE A DAMN DECISION AND STICK WITH IT. If you don't, you end up with all of the costs without all of the benefits...assuming you ever finish.

Any solar project has too many variables to manage. You MUST set objectives to nail down the parameters. Define it before you design it.

In general, solar is not the way to go if you have ANY other source of energy...or you get someone else to pay for it...like MY taxes...or use the utility company as "storage", increasing MY electricity rates.

On Mon, 16 Nov 2015 16:55:35 +0800, "Rheilly Phoull" Gave us:

Could always two-stage it too.

Make a battery box that the solar array keeps topped off that remains in place (a UPS as it were), and that battery is what you feed the charging circuit with for the unattached temporal device(s) with. That keeps the output stable regardless of what the solar is doing at the time. Make the storage battery big enough to provide the charging circuit for more than a full day, so whenever it gets placed into demand, there is no fluctuation due to waning of the sunlight available.

First, what is your solar panel rating?

I do not know and do not know how to calculate it. Lets say if I need to charge a 12V , 5AH lead Acid battery then what should be the ratings or specifications of the solar panel. And what would be the charging circuitry?

erica

Second, what is your load rating?

Third, are you working with Jessica on the same (or competing project)?

We have to understand the scope of your project(s). What are you trying to power with the stored energy? How big are the panels? What size of motor /actuator you need? What do you need to drive the motor/actuator with? It 's hard for us to come up with a plan when we are just getting bits and pie ces.

Show us your attempts at working it out and we might help you.

This is basic low power electronics. Homework???

Chances are for a 5Ah lead acid battery you would be better off in all senses of the word buying two plus an off the shelf charger for them and carrying a charged battery with you to the site as and when needed.

You can buy cheap solar panels intended to trickle charge automotive and boat batteries fairly cheaply - why make extra work for yourself?

Only thing to watch is some don't have a decent blocking diode in series and will discharge the battery at night and on cloudy days.

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Regards, 
Martin Brown

At a minimum, the solar panel or charger must output over 12 volts and to charge the battery you must supply 5Ah + charging losses for the battery.

So in theory, if you solar cell/charger can output 13.8 volts you can charge the battery if you can supply enough current long enough to fully charge the battery. If the charger can only supply 500mA at that voltage, you need 10 hours to charge the battery, sort of.

13.8 volts is the magic number as that's what you need to float charge a lead acid battery. Fast charging will require a higher voltage.

That's the real basic jist of what you're trying to do.

I need to charge a 12V , 5AH lead Acid battery then what should be

the ratings or specifications of the solar panel. And what would

be the charging circuitry?

Your problem is NOT electronics, at least not yet. Your problem is the SPECIFICATION of what those electronics are expected to do.

A solar panel is specified for output at high noon on the brightest day of the year at the equator. (much like the gas mileage specification for an automobile. Nobody ever gets that, but that's the only number you can easily determine.) The output is zero before dawn and after sunset. It varies throughout the day. It varies considerably with latitude and season. It will not put ANY charge into your battery if the open circuit voltage is below about 15V. That chops another big chunk of energy lost in morning and evening. That's made worse by the fact that you can't use any of it once the battery is fully charged. Nor can you charge the battery at a high rate when sun is available. Fancy electronics and/or mechanical tracking can mitigate many of these, but you might find that the cost outweighs the benefit. This is acute in a system where you can't really use more than an amp of charge current. Get a bigger panel and ship it.

Just to get into the ballpark, peak insolation is around 1KW/square meter. Assuming 10% efficiency, that square meter of panel can give you 100W at noon on the brightest day of the year at the equator. In Alaska in winter, you can count on very much less than that. Google "insolation". You'll find historical charts of insolation by month at various locations. The angle varies over the day in something like a sine function. Given the length of the day, and the graphs of voltage/current vs insolation for the panel you can integrate to determine how much total energy you might capture.

Then you factor in cloud coverage. Given your deployment location, you're likely to find that you need WAY more solar panel and WAY more battery capacity to cover the winter needs. Then, you have WAY more energy than you can use in summer. Depending on those numbers, you have the basis for designing your charge control system. Based on your limited storage capacity, you may find that you don't need solar tracking or fancy chargers. Over much of the year, you can just dump the excess energy. Improving the worst case a few percent may not be a rational approach if you're throwing most of it away most of the time.

So, why am I ranting about this? Back in the day, I used to interview engineering graduates for hire.

90% of them were clueless. 10% could tell you HOW to design something. Almost none had any clue about WHAT to design. The secret to productive engineering is to define the parameters before you start designing the solution. Think outside the box and look for the UNINTENDED as well as intended consequences of each decision.

Think of the problem as a huge tree. There are several workable solutions out on the tips of branches. Your job is to chop off branches with no viable solutions and compare the tradeoffs for those branches that do. Start climbing to the branch that looks the best, has the lowest risk and has the most viable neighbors in case you run into a snag

50 feet up.

You'll save yourself a lot of backtracking from dead-ends. Sure, you'll likely screw up something and have to rethink, but you'll still be way ahead of the competition.

Hi,

I found the following charger to charge the two 12V, 2AH lead acid batteries in series. So, the battery setup will be 24 volt , 2AH.

Am I going in the right direction? Will this charger be able to charge two batteries in series?

erica