Just another solar setup inquiry sorry about this but brain has frozen

Submitted: Saturday, Aug 09, 2014 at 17:11
ThreadID: 109084 Views:2000 Replies:3 FollowUps:4
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over so here goes I have put 120 watt folding panel {regulator removed} plus a 110watt panel on the roof of the towtug and ran the wiring from each setup separately to the regulator joined them in parallel and connected them to the regulator MPPT30 {CHEAP CHINESE UNKNOWN BRAND}.This charges a 105 amphour full river battery which in turn runs the 60 litre Trailblaza no real problems battery is fully charged and in float mode by early afternoon each sunny day.The system runs independently of towtug unless I close onto it.The inquiry is that I have never seen the charging rate over 8 amps mostly 6-7amps and I expected to see 11-12 amps.Am I missing something in the world of 12 volt DC. the facts that I can give are as follows in the morning before sunup the battery volts are around 11.8 - 12.2 volts open circuit on110watt panel {middadish}20.1 volts on 120watt 19.3volts and combined20.0 volts. On 110 watt panel under load[4.8amps] charge rate 4.2amps at 12.7volts. On 120watt panel under load[4.7amps] charge rate 3.2 amps at 12.3 volts battery charge. Could the low charging rate be because the battery still has plenty of chage in it at sunup? Thanking you all for any help forthcoming Mickb
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Reply By: HKB Electronics - Saturday, Aug 09, 2014 at 17:20

Saturday, Aug 09, 2014 at 17:20
I'm a little confused by the [4.8A] and the charge rate 4.2A@12.7V can you elaborate?

What is the voltage being applied to the battery, if the charge rate amps is less than the panels can supply I would expect to see around 14.4V at the battery terminals?

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Follow Up By: M&N's - Saturday, Aug 09, 2014 at 18:03

Saturday, Aug 09, 2014 at 18:03
Yes HKB thanks for your reply the regulator has a settable float charging voltage and I have set it at 13.8 volts as per details on side of battery.It would appear that this is the highest voltage the regulator will allow in any stage???So I have raised this setting to 14.4volts and the battery voltage went to this almost immediately[battery is fully charged at this point]In answer to your question the voltages were the battery voltage when I connectd each panel up separately.Perhaps I should deep six the regulator and purchase a quality one from you any recommendations Mickb
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Follow Up By: HKB Electronics - Saturday, Aug 09, 2014 at 18:26

Saturday, Aug 09, 2014 at 18:26
Generally, 13.8V would be considered a float charge rate ie when charging 24/7, the cyclic rate is usually around 14.4V?

If the battery immediately goes to 14.4V when you change the setting and the current only increase marginally then the battery must be fully charged.

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Follow Up By: M&N's - Thursday, Aug 14, 2014 at 16:25

Thursday, Aug 14, 2014 at 16:25
HKB sorry for the late mail but I am wandering around Pilbara coast and thjs is the first time I have opened up the computer.Upping the float voltage seems to have done the trick, amps are up and battery is charged up early each afternoon so thank you for your helpMickb
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Reply By: The Bantam - Saturday, Aug 09, 2014 at 18:21

Saturday, Aug 09, 2014 at 18:21
You have a couple of issues.

#1..solar pannels do not produce their rated output unless they are in direct sunlight, correcty aligned, in the middle of the day, at the height of summer and in a high radiation location.

In a low radiation location like tasmania or soutyhern victoria in winter you may find pannels maxing out at 20% rated and then only for a couple of hours in the middle of the day.

#2..you have two mismatched solar pannels on unmentioned length of cables.....the pannels will not be doing an equal share.

Because the pannels are mismatched, the regulator may have difficulty tracking a maximum power point......the whole point of maximum power point tracking is presenting the optimum load to the pannel and delivering the optimum charge to the battery...I direct relationship with a single pannel or a matched array and a dorect relationship with a single battery or matched bank....is required for optimum tracking of the maximum power point.

#3 it has been proven that cable that is too light or too long can drasticly reduce performance.

#4 just because a charging system..any charging system is capable of delivering current, it does not mean that a battery will accept it.....particularly if the battery has some age or has developed charge resistance.

I would not go lashing out on a new regulator just yet...it may make no difference.

There are a number of issues for you to work thru.

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Reply By: Ross M - Saturday, Aug 09, 2014 at 18:47

Saturday, Aug 09, 2014 at 18:47
The vehicle panel will not be square ON tot he rays of the sun so it's voltage may rise but the intensity oof the energy delivery just won't be there. It's output will be vastly reduced if angled to the sun as it will be most of it's life unless around lunch time.
The folder panel will be more suitably aligned though.

The Tug system is shorter wiring and the folder longer wiring.

While both are working around midday, and aimed as well as possible, have you measured the voltage drop at the panel end to the reg end of each conductor in the twin core wire cable? ie, The voltage drop from one end of the POS cable to the other end of that wire, should be the same voltage drop as the negative line returning the current flow to the panel.

Same for the tug panel and it's wiring.
Expect the folder to have a more voltage drop if the same voltages are measured at both panel junction boxes if same sized cable is used. ie longer cable run.

With both panel systems to the reg, if the cable size is causing significant voltage drop it will reduce the charge rate possible with just a small VD happening.

The panels are merely charge pumps and anything not at the optimum will reduce the pump "Speed"/"Intensity".
So, all connections and wiring has to be assessed to find the issue.

If you have a larger battery bank, the afternoon float time could be used to continue charging that battery AH capacity as well and in the morning the battery system will be at a higher voltage level with the same night time usage.
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Follow Up By: M&N's - Thursday, Aug 14, 2014 at 16:38

Thursday, Aug 14, 2014 at 16:38
Bantam & Ross M also thanks for input.All the panels are fixed on roof of canopy longest panel cable approx. 1.5metre all other cables less than 1.2 metres all cables auto 8mm[I think around 7.32mm2 if memory serves]Mickb
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