navitron
 
Renewable Energy and Sustainability Forum
Welcome, Guest. Please login or register.

Login with username, password and session length
News: Anyone wishing to register as a new member on the forum is strongly recommended to use a "proper" email address. Following continuous spam/hack attempts on the forum, "disposable" email addresses like Gmail, Yahoo and Hotmail tend to be viewed with suspicion, and the application rejected if there is any doubt whatsoever
 
Recent Articles: Navitron Partners With Solax to Help Create A More Sustainable Future | Navitron Calls for Increased Carbon Footprint Reduction In Light of Earth Overshoot Day | A plea from The David School - Issue 18
   Home   Help Search Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: 12V trickle charger from 80V PV Panel??  (Read 726 times)
marshman
Hero Member
*****
Offline Offline

Posts: 1022


WWW
« on: July 13, 2020, 10:32:18 AM »

Not sure if this is the right area to post but it is sort of PV/Battery/off grid related.

I have aquired a "shattered" Schuko PV panel - It is old big and heavy  2.0m x 1.2m  and rated at 330W.  max o/c V is 80V  The glass covering has shattered but the panel still gives a useful output. I checked it late yesterday afternoon and at 60V I get 3.5A, so a little over 200W.

Now I have a "collection" of old "classic" cars and other vehicles and I have the perennial problem of battery maintenance - i.e. going around and remembering to charge them every so often, disconnect them from the car when I don't use them for a while etc. A typical solution would be to get trickle charger for each one - something ideally like a Ctek - and just leave it plugged in all the time. But these units are expensive and with around 6 of them that's quite a few watts 24/7.  So I want to utilise this panel, but its o/p is 80V and I need a regulated 13.7V or what ever.  I have a box full of L200 regulators so I can knock up half a dozen low voltage regulators (with current limit) to control that actual battery charge/voltage but I need an efficient way of getting a stable 15V supply for the L200 regulators. Obviously I need some sort of DC-DC converter but none seem to go beyond 60V input which is too low. Anyone any ideas of a cheap and efficient way of achieving this - cheap being the operative word!  I  want to end up with 6 regulated outputs to maintain the charge on 6 separate 12V lead acid batteries.

Thanks in advance

Roger

Logged

3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
chasfromnorfolk
Hero Member
*****
Offline Offline

Posts: 687


« Reply #1 on: July 13, 2020, 10:55:49 AM »

As my post history would show, I love a bodge including wrestling with full size panels - so am reluctant to suggest alternatives except I do have a collection of old car batteries kept alive by 5 and 10w battery charging panels.
Navitron still have some in their sale for 2.40  - though they may not include leads and clips.

As an owner of stuff kept in case it comes in handy, and never does, I hesitate to trample.

Cheers,
Chas
Logged
kdmnx
Sr. Member
****
Offline Offline

Posts: 305


« Reply #2 on: July 13, 2020, 11:07:47 AM »

You need an MPPT.

The "Gold Standard" is Victron SmartSolar, their MPPTs are labeled by max power voltage/output current, the 100/30 model should work fine for your application (it runs about 180). Loads of cheapo units available on eBay or wherever, but it is usually worth "over-specifying" these.
Logged

12x JA Solar 340Wp panels (total 4080Wp)
Lux Power inverter charger
5x PylonTech 2000 2.4kWh batteries (total 12kWh (11kWh usable))
Countrypaul
Hero Member
*****
Offline Offline

Posts: 1740


« Reply #3 on: July 13, 2020, 11:10:34 AM »

Do you mean something like this only at a suitable price? https://uk.farnell.com/recom-power/rpa200h-11015sruw-p/dc-dc-converter-15v-13-5a/dp/2889091
Logged
Robl
Jr. Member
**
Offline Offline

Posts: 78


« Reply #4 on: July 13, 2020, 11:42:52 AM »

The trouble you'll find with virtually all "normal" dcdc converters that you may buy to do this sort of task (Farnell / ebay), is that they will have built in feedback - normally a good thing, but....  whether the PV input is 30V or 60V, they will attempt to stabilise the output at 15V say, ready for your L200s.  This will actually cause a problem with PV panels as a source when charging batteries:  as the load current increases from the dcdc converter, it will draw more current from the PV panel - ok to a point, but then the PV panel voltage will drop and the feedback will then cause even more current to be drawn, so the PV panel voltage will plummet.  You may even find the system would not start up due to this effect until you temporarily disconnect the load.
I don't know if you can get simpler open loop dcdc converters in this sort of range, but these would be significantly better - say dividing the 60V down by a factor of 4 to 15V irrespective of input, avoiding the positive feedback effect that you get with the primary dcdc converter.
Or as others say, MPPT or 12V ready PV panels.
Logged
Tinbum
Hero Member
*****
Offline Offline

Posts: 1236


« Reply #5 on: July 13, 2020, 11:53:12 AM »

You need an MPPT.

The "Gold Standard" is Victron SmartSolar, their MPPTs are labeled by max power voltage/output current, the 100/30 model should work fine for your application (it runs about 180). Loads of cheapo units available on eBay or wherever, but it is usually worth "over-specifying" these.

I'd go Morningstar over Victron.
Logged

85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
daveluck_uk
Full Member
***
Offline Offline

Posts: 223


« Reply #6 on: July 13, 2020, 12:11:39 PM »

You need an MPPT.

The "Gold Standard" is Victron SmartSolar, their MPPTs are labeled by max power voltage/output current, the 100/30 model should work fine for your application (it runs about 180). Loads of cheapo units available on eBay or wherever, but it is usually worth "over-specifying" these.

I'd go Morningstar over Victron.

Absolutely!

Scruff ( gawd bless him ) proved several times that victron were not that great given their price.

Morningstar sunsaver are the way to go for something like this.

Whether you PWM or mppt is debatable. I thought mppt really only benefits if the voltage is above 120v?Huh I could well be making that up! But I'm sure that's what I read on Pwm vs mppt debate somewhere. I'll try and find it.

I should point out that I am a massive Morningstar fan boi!! Big stylee!


Edit: sorry I was wrong. The thing I read was about a very specific application. Let the mppt Vs Pwm debate begin!!

« Last Edit: July 13, 2020, 12:32:16 PM by daveluck_uk » Logged
nowty
Hero Member
*****
Offline Offline

Posts: 1060



« Reply #7 on: July 13, 2020, 02:43:12 PM »

The problem with trying to use a DC to DC converter is that they are not max power point tracking so probably wont work unless you are only taking a fraction of the available power - I think Robl was trying to explain this.

A charge controller is the best bet, but the problem is Marshman's high voltage panel, if it was a lower voltage one, you can get charge controllers for as little as under 10 which would do the job. But, the cheapest charge controller I can find which can cope with up to 100v input is 60.

Is it possible to take the back off the box on the back of the panel and see if it can be re-wired to a lower voltage ?, the panel should have 3 or 4 sections which are in series with the shading diodes across each section in parallel. So it might be possible to re-wire those sections in parallel to get a lower voltage. That way you could use an ultra cheap charge controller.

Logged

12kW+ of PV installed and 60+ MWh's generated.
Home battery storage of 40+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage of 15+ kWh's.
6kW Ground source heatpump.
EV BMW i3 (another 30+ kWh's of storage).
300,000+ litres of water harvested from underground river.
biff
Global Moderator
Hero Member
*****
Offline Offline

Posts: 12269


An unpaid Navitron volunteer who lives off-grid.


« Reply #8 on: July 13, 2020, 03:42:36 PM »

Good idea Nowty,
        There should be st least 2 diodes . Am thinking 60v 2
  Would be likely  but a quick peep in the junction box will reveal all.
   Biff
Logged

An unpaid Navitron volunteer,who has been living off-grid,powered by wind and solar,each year better than the last one.
marshman
Hero Member
*****
Offline Offline

Posts: 1022


WWW
« Reply #9 on: July 13, 2020, 08:02:45 PM »

Thanks for the suggestions. No way does this justify Victron or Morningstar scale of investment I really want a virtually no cost solution.

Chas - yes I did look at "battery charging panels" when Navitron had their recent sale - but that would mean several panels and I would still have to wire them up as the leads wouldn't be long enough. Also not keen on just connecting up a panel with now regulation/charge control.  Besides I already had this panel!

Countrypaul - yes that would do nicely if it was a tenth of the price!

Rob/Nowty  -  Good points about DC-DC converters and feedback - I hadn't thought of the problems that could cause. I was intending to get the L200 to current limit as well as regulate the float voltage, so the current would not be unconstrained. In theory if all batteries are fully charged then the trickle current will be low so hopefully it won't be a problem, but if funny things start happening I know where to look.    

I did look at the panels to see if it could be reconfigured but as you can see from the attached picture of a good panel - all the cells are connected in series - hence the relatively high voltage. I suppose as the glass is already shattered I could attempt to dig in and add a centre tap connection to halve the voltage but the panels seems very fragile and I think that risks total failure. By the way the panels actually measure 7ft x 4ft   (2.13m x 1.22m) - they really are big - and heavy!



I have had another trawl through DC-DC converters and found one based on a XL7015 which has a claimed max input voltage of 80V.  Adjustable output ( 5 - 20V) @ 0.8A max. on fleabay for 3.75 delivered, which is my sort of money Grin so I am going to get a couple of those and see what happens.

Will let you all know when I have bodged it all together!

Roger
« Last Edit: July 13, 2020, 08:04:56 PM by marshman » Logged

3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
Iain
Hero Member
*****
Offline Offline

Posts: 1762


« Reply #10 on: July 13, 2020, 09:20:15 PM »

 Hi

Can't you use something like this ?

https://www.ebay.co.uk/itm/LCD-Solar-Panel-Battery-Regulator-Charge-Controller-Dual-USB-Tool-12V-24V-30A-B0/133460926922?_trkparms=ispr%3D1&hash=item1f12e421ca:g:BdUAAOSwJNxfBvd4&enc=AQAFAAACcBaobrjLl8XobRIiIML1V4Imu%2Fn%2BzU5L90Z278x5ickkBUIiHwYv5YgVss0WaiENzy5rogQny23%2B2bzcqJYtoxXZqVRaoPRH24W82bMwchax%2FSPbLJ6DzrZb9oZBBdlf2Ghy%2B0p6OmtMrp1zhDZxVEGiEZQrzwC1Omwe0UPXGP6%2BdMe3CP0yT2lhFfzn05iNwB%2FeyRKojVzz%2FkhvQMqV7yVFsKTz8F7PyPgdO3%2BBi0SjUEEoYtNya5PLQwhXyzh30DqIpc9VwZq1uUx8KxP6FGn%2BycLg8%2BBsmfK%2FxH%2B4eShA7p%2FJjU9jhFz4SSa%2FSM2xJYOpnMT1SLSIdECM6hLASZy82Iku7ry0a2KLDezC8ScZKcQ8q3rIb06LQU1GLoZ2kD%2F1Wu42D1yMQ%2B1c8qSo3WGmPlnRmxw7dpsO9YMzvyEltZ4xIrOICa0a1t0E0tVY%2Br6Q2JgW9MZ7Isct4pN5SQZap9GQ1Y8fC%2BpqOdWPEcOsgjb8hCZ%2BusgEofe2cAJ%2BpqlEt1Zq3zLaz%2FbWuCyoWCfkNOcUu0MFfqCOzfvjybKoHEesB%2FzzbqEqh3LvWXszVy5G3YGfe7GvEWjihnGKZNNulOQY0xBTa3DHAVdIeh9nrytTifAxes3ndKIRkAHE6QOU15bPZ%2BZ12Jp%2FdNAkNmNOEHqzMj0DsY%2BaK%2BA3qxi05ncF8hG1s5mIx4Fj%2Fux83AIpPTehIJsLyvLIE7gZrb0hV%2BvsqSWtek1GbGFshjEDSKqEPtpVrgpk%2BFqZrKkJiba2GDa52dfMj7mQOHcMVpFprGdwZk2Qo481gogZ4bfq44T7KO3j9%2BPiWoDu5QUQaQ%3D%3D&checksum=1334609269220b33517140f24e55847141fbba5aa30c



Just charge 2 batteries in series 24V and then run all your regulators from the output of the unit.

The output is protected and can switch off when no solar and/or voltage drops.

Iain
Logged

1.98kWp PV (11 x Sharp 180 and SB 2.5)
20 x 65mm Thermal and 180ltr unvented
Powervault 4Kw - G200 Lithium-Ion (LiFePO4)
9000ltr rainwater storage   Plymouth
marshman
Hero Member
*****
Offline Offline

Posts: 1022


WWW
« Reply #11 on: July 13, 2020, 10:34:09 PM »

Iain, I have looked at those but they won't tolerate high input voltages. Also I want to leave the batteries in the cars, just connecting the charging leads. The batteries are all different capacities and makes so even if I did remove them from the cars they are not suitable to charge in series.

Roger
Logged

3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
jonesy
Hero Member
*****
Offline Offline

Posts: 847



« Reply #12 on: July 15, 2020, 11:02:11 PM »

With an input of 80V in 15V out, the maximum current is 0.3A, figure 7 of the datasheet.  It improves to a maximum of 0.4A with lower inputs.
I also think you'll need around 16V into the L200, as in needs about 1.5V head room.
Figure 26 of the L200 datasheet shows a high voltage circuit using a simple pre-regulator. Good for 92V if I read it right. You'll dissipate a fair amount of heat even at low current so check Pdiss carefully and fit a large heatsink.
You might get a useful output from a normal 110V switch mode power supply. They normally work down to 80, and probably lower at light load. An old pc psu can deliver 12V at 10A and often has a 110V switch. You can usually up the voltage to say 16V by changing the reference. I'll try one tomorrow if I get chance.
Logged

1.1kWp PV & SB1700. 7kW log burner.
marshman
Hero Member
*****
Offline Offline

Posts: 1022


WWW
« Reply #13 on: July 16, 2020, 09:56:47 AM »

With an input of 80V in 15V out, the maximum current is 0.3A, figure 7 of the datasheet.  It improves to a maximum of 0.4A with lower inputs.
I also think you'll need around 16V into the L200, as in needs about 1.5V head room.
Figure 26 of the L200 datasheet shows a high voltage circuit using a simple pre-regulator. Good for 92V if I read it right. You'll dissipate a fair amount of heat even at low current so check Pdiss carefully and fit a large heatsink.
You might get a useful output from a normal 110V switch mode power supply. They normally work down to 80, and probably lower at light load. An old pc psu can deliver 12V at 10A and often has a 110V switch. You can usually up the voltage to say 16V by changing the reference. I'll try one tomorrow if I get chance.

Thanks for that, must admit I didn't read all the way to the end of the datasheet. To be honest not too worried about the 3 - 400mA output limit, it is only for battery maintenance - i.e. trickle charging rather than bulk charging.

Not really interested in messing with SMPS - nice idea about an old laptop power supply as you say many will function down to just over 80V, but the PV will potentially drop to well under 50V in low light (winter!) so I suspect they wouldn't work for a lot of the time.

The dropout voltage on the L200 is 2.0V (nom) and 2.5V (max)  for battery charging/maintenance it really does need at least a 16V input - I have used it before.  The PV Panel I have is 80V O/C and around 60V in full sun supplying a couple of amps. So I need to drop around 45V @ up to 2A (enough for 6 batteries at 300mA each).  I was aware of the design notes on using the L200 with higher input voltages, but this means more complexity and also dissipating more power than I will be using! , potentially up to 90 Watts.

I have the fleabay modules on their way so will have a play. Thanks agian for your comments.

Roger
Logged

3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines
SMFAds for Free Forums
Simple Audio Video Embedder
Valid XHTML 1.0! Valid CSS!