Charging system help

Submitted: Tuesday, Jan 17, 2012 at 20:19
ThreadID: 91275 Views:3012 Replies:7 FollowUps:10
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Hi all,
I've been reading along on this forum for a while now but this is my first post.
I currently have a 100w folding panel, a 120ah full river agm and a cheapo 3 stage regulator.
I suspect that the regulator is not performing correctly as it only occasionally enters float mode even when there is no load connected to the battery. It just sits on absorption mode which is obviously harmful to the battery. I've had this setup for around 4 years now and as solar has been my only source of charge the battery has very rarely been left fully charged, especially through winter when it has been left in the shed. Rested voltage has never dipped below 12.2 (usually between 12.4-12.6) though so the SOC has always been relatively high, just rarely 100%.
I recently purchased a projecta 25amp charger and am extremely happy with it. I set it to 6amps, selected AGM and it charged the battery and had sat in float mode ever since.
I'd like to build on my rudimentary system and end up with something more sophisticated and useful. I'd like to replace the solar regulator and I'd like to add a dc-dc charger as we often drive for 5 hours after work on Friday to camp for the weekend. As I've only been able to charge the battery by solar when I get time on weekends this means the battery is going l week with no charge and then loaded with the fridge Friday arvo and getting no charge till sunrise Saturday morning. At least now I can use the ac charger to keep it topped off until we leave.

As for the regulator. I guess I'm tossing up between the morning star mppt 15amp and the steca PWM 15amp. The 15amp leaves some room for growth and I like hte display on the steca. I'd have to fork out more for the MPPT and then more again for the remote display so that I cancer what's going on but it might be worth it as we camp a lot in winter. Any advice here would be good. I don't want to start an argument though.

I'm looking at the Projecta DC20 for my dcdc charger as I'm super happy wih my acdc charger and my inverter. It appears to do everything I want it to, will be mounted in the cabin an has a wiring option to charge only after the ignition is on.

Lastly I'm after some advice on linking it all together. I figured I could stick an anderson plug on the battery and each charger and plug it into whichever charger I want to use at the time. I also thought there might be a way to have three Anderson inputs on the battery and be able to wire up some sort of voltage sensitive circuit that will only use one charger and pick the best option at any time giving preference to 240v. Or maybe that is too difficult/expensive to bother with.

Thanks so much for any help.

Benen
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Reply By: Sand Man (SA) - Tuesday, Jan 17, 2012 at 20:55

Tuesday, Jan 17, 2012 at 20:55
Hi Benen,

I think you are unnecessarily complicating your setup.

You would find it hard to ignore the benefits of the CTEK D250s Dual dc-dc charger.

You can have both alternator input and solar panel input operating at the same time and the CTEK will determine which is the best for optimum battery charging.
The D250s Dual has a built-in MPPT solar controller for otimum operation and a current input of up to 20 Amps.

Ctek D250S DUAL

A recommended supplier

No affiliation with any manufacturer or distributor, just a satisfied customer.



Bill


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Reply By: Benen H - Tuesday, Jan 17, 2012 at 21:26

Tuesday, Jan 17, 2012 at 21:26
The reason I am leant towards the Projecta is that I read that the ctek spends to long in absorption mode and that you need a 120w panel to get the regulator to work properly. is this false info?
AnswerID: 475236

Follow Up By: ModSquad - Tuesday, Jan 17, 2012 at 21:41

Tuesday, Jan 17, 2012 at 21:41
Ben,

you can use the "post follow-up" button at the end of a response to type a reply directly into that response. That way, the respondant will get a copy.

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Follow Up By: Sand Man (SA) - Tuesday, Jan 17, 2012 at 22:42

Tuesday, Jan 17, 2012 at 22:42
Sounds false to me.

I have a bi-fold 80 watt panel. Nowhere in the User Manual does it mention any restriction of panel capacity (size).

I have some experience with the Projecta brand, having a Projecta Charger.
I wouldn't rate the Projecta in the same league as the Ctek or Redarc products.

Bill


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Follow Up By: Benen H - Tuesday, Jan 17, 2012 at 23:38

Tuesday, Jan 17, 2012 at 23:38
Mods quad, cheers for the tip.
Sand man, thanks. I'll check out the ctek more.
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Follow Up By: Member - Captain (WA) - Tuesday, Jan 17, 2012 at 23:42

Tuesday, Jan 17, 2012 at 23:42
I was looking at the Ctek 250S dual but after reading many reports on the net, it does appear they have problems running panels less than 120W (and as high as 160w), particulalry in shady conditions. The smaller the panel and the lower the light level, the output would drop off to zero in what one would otherwise think should give t least a few amps charge, well that was my summary on the many web reports I saw.

So I decided to go the Redarc BCDC 1240, it is a mppt solar charger and a dc-dc charger. Has worked very well on my 160W panels even in very low light conditions. the dcdc charger side is also great, gets a whopping 40A into my AGM bateries when charging from the vehicle alternator.

Cheers

Captain
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Reply By: Mick O - Tuesday, Jan 17, 2012 at 21:46

Tuesday, Jan 17, 2012 at 21:46
Have a look at the Redarc BC-DC 12-40. It is a multistage DC-DC charger, battery isolator and a MPPT solar controller in the one unit.


Redarc Bc-Dc charger


Cheers Mick

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Follow Up By: Benen H - Tuesday, Jan 17, 2012 at 22:52

Tuesday, Jan 17, 2012 at 22:52
I'll reconsider the ctek then but I think a 40 amp charger wouldn't be the best thing for only a 120ah battery?

Thanks very much for the quick responses.

Benen
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Follow Up By: Member - shane c5 - Tuesday, Jan 17, 2012 at 23:22

Tuesday, Jan 17, 2012 at 23:22
My friend has one of these fitted, but apparently,they don't like water!!!!!
shane c5
ps. he is trying to sell it. As he wants to upgrade. Would suit someone who doesn't do a lot of water crossings.
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Follow Up By: Benen H - Tuesday, Jan 17, 2012 at 23:40

Tuesday, Jan 17, 2012 at 23:40
What electrics do like water haha? Upgrading to what?
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Reply By: Benen H - Tuesday, Jan 17, 2012 at 23:42

Tuesday, Jan 17, 2012 at 23:42
What is the solar regulator like in the ctek? Does it compare with the dedicated solar regulators? Can you get a display?
AnswerID: 475253

Follow Up By: Battery Value Pty Ltd - Wednesday, Jan 18, 2012 at 08:13

Wednesday, Jan 18, 2012 at 08:13
The solar regulator inside the D250S dual isn't a true MPPT one.
E.g. you can't use a 24V panel for charging a 12V battery with it.
A true MPPT solar regulator is designed to track the maximum power voltage over a wide range e.g. 15~100V.
The maximum power point voltage of a panel depends on the amount of cells in the panels and operating temperature (which is also dependent on the amount of insolation).
A true MPPT regulator seeks and holds this voltage in short intervals, typically every 5 to 10 seconds.

For the D250S dual, chances are that it fixes the max power input voltage to around 17V, without actually tracking it.
Actually that makes sense in a way, because if you use a 12V rated panel for 12V battery charging, there isn't much to track in terms of max power, espcecially under hot conditions.
The advantage of true MPPT functionality is lost in the D250S, alone due to its inability to work with higher panel voltages.

Another major shortcoming of the D250S, and probably also the D250S dual is, that the battery can easily get over-charged because the absorption/float switch over is set to 12 hours, or 0.4A.
So whenever you've got a load (fridge) connected to the battery, it basically never switches back to float as long you're driving.
You could say that this manufacturer skimps on processing power of the inbuilt microcontroller, which hasn't got the muscle to run a proper MPPT routine, nor can it do cumulative absorption stage charging, nor a display.

cheers, Peter
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Reply By: Member - John and Val - Wednesday, Jan 18, 2012 at 07:41

Wednesday, Jan 18, 2012 at 07:41
Benen

Suggest for a 120Ah battery, don't go beyond a 20A dc-dc charger. 20A is ample for the sort of use you're talking about, so why push the battery harder than necessary?

Solar - sounds as if you are using a PWM controller, probably not mounted close to the battery. I agree with the advantage of a decent MPPT solar controller, but either will perform much better if mounted close to the battery.

Have you considered the MPPT controller sold by Battery Value, one of our commercial members who frequently responds to electrical matters raised here? Suggest check his profile where I think you'll find a link to details. From the specs it is a good bit of gear and reasonably priced.

I think you may find a voltmeter a useful bit of kit too. It's hard to know just what the solar is doing without one, and cheap multimeters can be had for less that $20.

Suggest if you haven't already been there you may find Electricity for Camping a useful read.

Cheers

John
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Follow Up By: Benen H - Wednesday, Jan 18, 2012 at 07:55

Wednesday, Jan 18, 2012 at 07:55
Hi John. 20amp was what I was thinking too. The regulator is mounted about 15cm from the battery and has a built in volt meter so I'm certain that it is faulty.
I'll check out that mppt controller. Thanks very much.

Benen
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Reply By: Robin Miller - Wednesday, Jan 18, 2012 at 08:07

Wednesday, Jan 18, 2012 at 08:07
Dc DC chargers switched in with ign on are good idea Benen , but you say you drive 5hrs sometimes and no charge goes into the (unconnected) battery - wondering why not do what many do and just connect up to car alternator for the 5 hours , this should see the battery pretty well charged at start of weekend.
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Follow Up By: Benen H - Wednesday, Jan 18, 2012 at 11:07

Wednesday, Jan 18, 2012 at 11:07
You're right Robin. I should probably stick a cig socket in the bak and just run the fridge from that while I'm driving and just replace my regulator. I'm not really sold on any of the dcdc chargers. It looks like the dcdc chargers have a bit of improvement to go?

Thanks for your help everyone.

Benen
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Reply By: Benen H - Wednesday, Jan 18, 2012 at 11:50

Wednesday, Jan 18, 2012 at 11:50
For now I'll just replace My dodgy regulator for now. Are there any other good mppt regulators with a display? I've mainly just been looking at the Morningstar and remote display. I'll check out the local controller mentioned previously too.
AnswerID: 475296

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