Solar battery charger questions.

[El_Freddo]

G'day all.

I'm looking into a trickle charger for a battery or two, I could possibly be after two separate units for different jobs.

Here's what I need:

Currently the primary battery is going flat enough not to turn the engine over after about 7 weeks of not really been used at all (other than the odd move around the yard - no charge time).

I've also got the second battery used for the dual battery system that I think would benefit long term from having a trickle charge. This battery gets some serious use for a week or two at the most then it sits idle, not the best situation I don't think.

I don't know a lot about batteries other than if you drop the voltage below 10.5V you kill them.

I've been looking at these units:

Keep your batteries charged, or recharge them after powering lights and appliances the night before. It is an amorphous type panel, capable of supplying current up to 1 amp, suited to a wide range of charging applications, and even powering small 12V appliances. The 3.5 metre lead has a plug on the end, to which you can connect the supplied leads.

These are 300mm leads to alligator clips, a cigarette lighter plug, and eye terminals. A bright blue LED indicates the panel is working, and the strong ABS frame can be bolted down for mounting.

And this one:

Convenient brief case sized solar chargers for keeping a car battery topped up while on holidays or in storage. Three sizes for small, medium and large cars or 4WDs. Each terminates in a cigarette lighter plug or alligator clips.

Specifications
Pmax 7W
Voltage (max) 18V
Current (max) 388mA
Dimensions (closed) 340(L) x 320(W) x 36(H)mm
Dimensions (open) 630(L) x 340(W) x 18(H)mm

^ Max voltage is the issue here, but I reckon a regulator could sort that out. The last one is this:

Ideal for charging sealed lead acid batteries, this 12 volt 4.5 watt solar panel is tough enough to be walked on and can be mounted on a flat surface or on its brackets so it can be moved to follow the sun. Great for use on a yacht or boat or in a car.

Voltage (max): 18V
Current (max): Up to 250mA-
Panel Size: 187 x 255 x 17mmThese

I've got an AC delco sealed battery as the secondary battery in the dual battery system, something like one of these:



12V (obviously), 82 amp hours. It was the amp hours for the size and price that I went with. There was a "better" battery available but with what I would say was a significantly less amp hour rating.

If you know electronics with the above stuff I'm all ears if it's in laymen's terms! I would also like to know what the best way is to look after the battery when it's not in use.

Cheers

Bennie

[tambox]

Solar panels are good, in the right enviroment.
I have played with some solar setups, mainly trickle chargers for vehicle batteries.
Be aware of the different types mono, poly or amporphous as it varies their life/performance.
In summer a small solar panel, ie $19.99, will keep the battery good, provided you have nothing else drawing current, ie alarm etc. (siuts my brumby)
In winter, due to lack of sunlight and cold weather you need at least a 2 amp panel.
I eventually deicided it was easier and more beneficial to run a 240v "fully regulated charger" on the bigger batteries with other accessories drawing current. These are great, they cycle the battery (to increase battery life), then charge, then trickle once the battery has fully charged.
The cheapest way to do a good controlled charge system, is to buy the good old Arlec4/6 from kmart for about $25, then a kit from Jaycar for $19.95.
I have been using these for years on cars, tractors and trucks.
Batteries last much longer and work when the key is turned.
Saves getting out the "chainsaw alternator" for a quick charge.

These work for me.

[El_Freddo]

What's the kit from Jaycar you're talking about - details are a bit hazy there

So basically any of those units would do the job, I've just got to pic one and make sure it's got the correct voltage regulation to keep things happy?

What size wattage is your 240v panel? And which material is the best one to get/use/best value for money in your opinion?

Cheers

Bennie

[tambox]

All the solar trickle chargers I was using were 12v.
In summer, any of the ones you listed will work, provided they are connected to battery only. ie not running your car alarm etc.

But in winter, they will have trouble keeping the battery charged.
The charger systems I was talking about run off mains.
If you want reliable pure solar you will need at least a 20W panel, with regulator, but that will depend on reliable sunlight all through winter.
In winter you will get limited hours on sunlight, shorter days, clouds, rain etc.
Cold weather slows the battery, ie why people get flat batteries in winter, that were ok in summer.
Unless you compensate buy using a bigger panel, it hard to make it reliable.
You have to work out if there is any current drawn by stuff connected in your loom.
Then add that to the battery charging requirements.

Simple isn't it??

To get a reliable system, you have to carefully work it out first.

[60766244]

G'day all.

Currently the primary battery is going flat enough not to turn the engine over after about 7 weeks of not really been used at all (other than the odd move around the yard - no charge time).

...

I don't know a lot about batteries other than if you drop the voltage below 10.5V you kill them.

...

If you know electronics with the above stuff I'm all ears if it's in laymen's terms! I would also like to know what the best way is to look after the battery when it's not in use.

Cheers

Bennie

Could you install an under-bonnet isolator switch? I have one on my vehicles for when I FIFO'd to stop the battery drain from the immobilisers little red light and anything else that might be doing it. Maximum time I ever left the vehicles was 9 weeks without a glance but the isolator seemed to do the trick... I think the switch was $40 from SCA and the battery wires I pirated of other dead vehicles. I just attached it to the positive. They make them for 1 and 2 battery systems so you can option the switch between 'OFF', 'B1', 'B2' and 'B1+b2'.

I'm not much more than a layman about this stuff so what I'm saying is anecdotal.

[rubisubi]

I use a C-Tek Trickle battery charger 5Amp, best $100 bucks i ever spent. Use it for the boat, fourbie & falcon. has several settings as well ie car, bike, snow, re-condition (yet to know if that works). Obviously you need 240V power but its easy enough to run a lead to each battery. The units are IP 65 rated as well. They work super quick as well and you dont have to worry about removing the battery or cooking it.

[El_Freddo]

Thanks for the ideas fellas.

The isolator switch, I'm hoping not to go down this route - I really detest reprogramming the radio and having to wait around for the ECU to sort out it's idle properly etc. If I was to do this I wouldn't bother with a switch, just disconnect the negative terminal from the battery instead.

I also want to use the solar charger when we're off road to get the most value for money

Cheers

Bennie

[pitrack_1]

Bennie,

two things you need with a solar panel for battery charging maintenance:

1) A forward-bias diode to prevent reverse discharge (happens at night or in low light). The panel may already have this built in, check with the manufacturer. If it hasn't, one can be simply soldered in- your local Jaycar can recommend an appropriate one.

2) Charging regulation (as you mentioned) to control voltage and charge level. A good regulator will have short circuit, reverse discharge control, voltage regulation and charge level control all built in.

A simple all-in-one unit is the Kemo charging regulator M083. This is a simple small plastic "brick" with three wires: An input +ve, and common ground (-ve) and an output +ve. It has the charging control, reverse discharge and short circuit protection built in and will ahndle up to 1.5A. You can also use it to regulate and unregulated power supply/charger, I've used this unit at a gliding to maintain seldom-used batteries off a 15V power supply and it works well. You can look online for it if you wish to. Housed in plastic with all components sealed off from access, it's just about weatherproof as-is. Jaycar used to sell it, they now have a 5A version Kemo M149 for $29.95, Cat no AA0348 (haven't used this one but on specs arguably better) $29.95.

You also need reliable light.

With the panels, you get what you pay for, more $$$= more efficiency, longer life, performance in more marginal conditions.

Hope this helps!

[subaruby]

Something to consider,

An 82 amp hour battery (using the first solar panel) will take 82 hours to charge at 1 amp.
This is 82 hours of good sunlight. This realistically will be about 6 hours a day.
Therefore about 13 days to charge.

If you were using a solar panel that only produce .5 amp it would take twice as long.

This will give you and idea of the efficiency of solar panels. You need to spend a decent amount of money to get a decent solar panel.
The litle solar panels you are looking at probably wont need a regulator.

A multi-stage charger like the c-tek is better value for money. Get at least a 3 stage charger.

To work out how long your battery will last while camping add up all the amps of the devices you are running and then devide your battery (82 amps) by that amount.

eg fridge draws 1amp therefore run time is 82 hours (82 divide 1)

However yopu do not want to run the battery totally flat and obiviously when you drive it charges up again.

Lots of things to consider rearding usage

[El_Freddo]

Patrick and Subaruby - thanks for that! Looks like I'll have to carefully choose the setup I go for.

Subaruby, what you say makes total sense about the charge rate! I'll definitely be using this info when looking at a solar panel!

Cheers

Bennie

[pitrack_1]

An 82 amp hour battery (using the first solar panel) will take 82 hours to charge at 1 amp.

It's a little bit more complicated than that...

Lead Acid Battery Charging
Nothing's 100% efficient (except theories ). If you take a standard 7Ah SLA (Sealed Lead Acid) battery, it takes 14hrs to fully charge at 700mA (0.7A). This is a good rule-of-thumb for a normal lead-acid battery you can extrapolate, being:

Divide the Ah rating by 10 for the current and charge for 14 hrs (at ~20-25 deg C).

So your 82Ah battery can be fully charged in 14 hrs at a constant 8.2A- that's a big charger or large solar panel for more than 1 day.

Charging faster becomes less efficient, generates more heat, boils of water and generally reduces battery life unless the battery is designed for it.

Lead Acid Battery Maintenance
To maintain (trickle charge) a battery, hold the 12V battery at ~13.2-13.8VDC. You can roughly estimate the charging current by dividing the charging current by 10 again (or capacity by 100). So for a 7Ah ~70mA, for an 82Ah ~820mA (0.82A). Less current/voltage may not maintain the battery and higher voltage/current will boil off water (and reduce life).

Capacities

To work out how long your battery will last while camping add up all the amps of the devices you are running and then devide your battery (82 amps) by that amount.

eg fridge draws 1amp therefore run time is 82 hours (82 divide 1)

Again, nothing's 100% efficient and you don't want to fully discharge your lead-acid battery anyway as it will damage it. Furthermore the ratings (eg 82Ah) are performed under controlled conditions at a set rate for a given period. Generally speaking this is for 20 hours. So your fully charged 82Ah battery could supply a constant 82 / 20 = 4.1Amps for 20 hours (at a given temp, usually 20-25deg C). In trying to optimise the numbers the manufacturers can 'specify' their own tests/hours/ratings so these should always be taken with a pinch of salt, unless they quote against some standard.

If you wish to discharge faster, the effective capacity will decrease due to the internal resistance of the battery wasting proportionally more energy as heat. At lower currents you need to take into account the self-discharge rate wasting energy.

You get what you pay for...

This will give you and idea of the efficiency of solar panels. You need to spend a decent amount of money to get a decent solar panel.

There's a reason BP solar panels can offer a 25 year output warranty.

A multi-stage charger like the c-tek is better value for money. Get at least a 3 stage charger.

Absolutely, if you can afford/need one. Generally a good charger/maintainer will pay for itself in extended battery life.

...But what are you going to do?
Basically, spend money in proportion to what you're going to do.

If you simply trickle charge to maintain, with a seldom used standard battery semi-permanently connected to a small panel perhaps my solution will suffice (it did in our case, maintaining car/tractor batteries for up to 3 years- the tractor battery was drawing almost the full 1.5A of the little Kemo unit I had just to maintain the large battery).

If you are going to deep-cycle regularly and require to recharge and maintain, spend up on a good unit (eg CTek) and panel. In fact, get a good mains charger unit if possible.

Some References...
See Peukert's law
For an explanation here.
Comprehensive resource covering battery types, behaviour, failure, charging, maintenance, recovery, etc can be found on Bill Darden's Carr Battery FAQ site, in particular, charging.

Cheers,
Patrick.

[NachaLuva]

Getting a bit too technical for me lol

Found this, 3 stage with some bells & whistles:
http://www.jaycar.com.au/productView.as ... ID=1004#12

"uses pulse width modulation for optimal 3-stage charging. Over current, over voltage, short circuit, over temperature and reverse polarity protections also featured", $49

Can anyone suggest which type of panel he should get: amorphous, etc...
Jaycar says: "Note. The output from amorphous solar panels gradually decreases over years, unlike polycrystalline which do not."

Would this be any good? Amorphous, $40:
http://www.jaycar.com.au/productView.as ... ID=1004#12

Or monocrystaline, 5W, 25yr warranty, $23:
http://www.jaycar.com.au/productView.as ... ID=1004#12

[tambox]

Or monocrystaline, 5W, 25yr warranty, $23:
http://www.jaycar.com.au/productView...BCATID=1004#12
I have tried this one, it will not keep a small tractor battery,110Ah, that has no current being drawn by accessories, charged all the time. In summer just. In winter, no.

What pitrack_1 said is correct. You have to exceed your theoretical charge to allow for losses, then add any extra current required by accessories.
240v controlled charge is the easiest/best for battery and cheapest.
Solar is great, like wind turbines, in the right conditions.

[NachaLuva]

Or monocrystaline, 5W, 25yr warranty, $23:
http://www.jaycar.com.au/productView...BCATID=1004#12
I have tried this one, it will not keep a small tractor battery,110Ah, that has no current being drawn by accessories, charged all the time. In summer just. In winter, no.

Thx for the heads up.

What pitrack_1 said is correct. You have to exceed your theoretical charge to allow for losses, then add any extra current required by accessories.
240v controlled charge is the easiest/best for battery and cheapest.
Solar is great, like wind turbines, in the right conditions.

Repco has a special on the CTek 4 stage 3.6A batt charger in their catalog, $109 save $27.

[pitrack_1]

Or monocrystaline, 5W, 25yr warranty, $23:
http://www.jaycar.com.au/productView...BCATID=1004#12
I have tried this one, it will not keep a small tractor battery,110Ah, that has no current being drawn by accessories, charged all the time. In summer just. In winter, no.

Tambox, is the battery fully disconnected? The alternator regulator can give a constant low load.

From the estimates, 110Ah/100 = 1.1A maintenance current. This is probably an overestimate for good/new/long-life batteries but it is a 24/7 event.

From a 5W panel, Current = Power / Voltage = 5W/13.5 =~0.37A at perhaps 8hrs/5days per week in summer. Note the charging voltage (~13.5V) is used, and losses in the charging electronics are not accounted for.

So no, this panel probably won't maintain a tractor battery.

A plug-in charger will constantly maintain the battery, whereas a solar panel will not. You are constantly (small) cycling your battery on a solar charger as the self-discharge is constant but charging is daylight only. So you get a small discharge overnight to be recharged during the day.

[tambox]

This tractor is a good old fergie.
Alternator ?? It has generator and the good old relay regulator.
These draw no current from the battery, but use the generator output to drive the relays, very basic, very inaccurate, but better than nothing.

Summer, due to the air temp being high and there is a lot of sun, it was good enough for that solar panel.
The panel was angled for winter sunlight, but still did not get enough, plus being in the hills it gets cold and limited daylight hours.

I gave up on solar for this type of work. I now have all the big batteries on the Jaycar kitted Arlec 4/6 chargers. On a timer switch over summer, 6 hrs every second day. In winter, they are on all the time.

The ride on mower and motorbike are on solar, that works ok.

Since I started doing this charging setup on the batteries, they last heaps longer before they need replacing.

Its worth it.

[pitrack_1]

Repco has a special on the CTek 4 stage 3.6A batt charger in their catalog, $109 save $27.

I have the Jaycar CAT. NO. MB3604 5-stage ($80). Specs flyer here- pretty good for a flyer as it actually tells you what it does...

It works well, although the mode selection button has become difficult to use over the years (probably needs a clean). It fits under the bonnet near the battery so it's weather protected and I just run the extension lead out to a nearby power point (extension lead socket/charger plug connection is also under the bonnet).

Note it's only 3.8A max so it won't charge super-fast and a 110Ah tractor battery is probably at the charger's limits.

[pitrack_1]

This tractor is a good old fergie.
...
Since I started doing this charging setup on the batteries, they last heaps longer before they need replacing.

We had a large(ish?) Ferguson (I think), a smaller Deutz and a dune buggy. Plus an old V8 Statesman which I'd connect up when I was there. Cost of the 240V charging system was repaid within one year simply through one saved battery.

Its worth it.

Absolutely.

[El_Freddo]

Ok, I've been thinking about this - and at home I reckon the mains powered charger is the way to go.

So, now the question is what would be best? And can you charge different batteries in parallel/series or not? I'm guessing not for either.

Cheers

Bennie

[NachaLuva]

can you charge different batteries in parallel/series or not? I'm guessing not for either.

You couldnt in series..thats them connected in line. Trucks can use 2x 12V batteries connected in series to give 24V.

To connect them in parallel (each with its own independant connection) may mean one battery will get overcharged. Unless there is a charger with multiple outlets for exactly this purpose...ie, reads each batteries voltage independantly.

There's a few people who use the CTek & rave about it. Thats prob the way I would go....