Tuesday, Jan 17, 2017 at 12:43
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Hi Tim,
There is some good information above, but I will try to put the complete issue to you.
Solar modules are typically rated as say "12 volts" which indicates the system voltage that they are to be used on. However they actually output higher voltages in operation and the connected controllers regulate the voltage to suit the battery needs.
CONNECTING PANELS IN PARALLEL:
Differing brands and models of solar panels produce differing output voltages so it is necessary to match panels of similar voltage characteristics if they are to be connected in parallel. Modules of significant higher voltage will overcome those of lower voltage such that they will not contribute.
In your case, you would need to determine the specifications of your panels in order to consider this proposition. However, if the panels are properly matched, this is a good method of increasing the harvest. Just ensure that the controller can handle the current.
CONNECTING PANELS IN SERIES:
This is essentially a "chain" and its strength is in the "weakest link". So the maximum power that can be delivered from panels in series is limited to the rating of the lowest module. In your case, the van panels of 300W would be limited by the vehicle-mounted panels of 160W. The voltage has been doubled but the current has been limited so there is no effective gain. The controller would need to be able to accept the increased voltage.
Furthermore, the vehicle battery is then left without a charging source.
CONNECTING THE CONTROLLER OUTPUTS IN PARALLEL:
If the output of the vehicle solar controller were to be isolated from the vehicle battery and then connected in parallel with the van controller there is a likely hood of undesirable interaction between the controllers upsetting the charging process.
The vehicle battery is then left without a charging source.
Not a recommended option.
CONNECTING THE BATTERY BANKS IN PARALLEL:
If the vehicle and van battery banks were simply connected in parallel, each with their own controllers in place then this would possibly be OK as the impedance of the cabling between the two banks would probably overcome any controller interaction issues. But little would be gained overall.
My recommendation is to leave the system as it is. Your proposition would be to complicate the system without benefit. You do say that it currently "seems to work well". If you wish to add more solar collection you would do
well to add more panels to the van, either in series or parallel but with careful panel selection and consideration of the controller current capacity.
Incidentally, the "electro battery controller" you refer to is a device to protect the battery from over-discharge and plays no part in the solar charging.
AnswerID:
607662
Follow Up By: RMD - Tuesday, Jan 17, 2017 at 12:57
Tuesday, Jan 17, 2017 at 12:57
Allan. Do you think panels of closely but differing voltages can be used in a parallel circuit because when the regulator is operating it is dragging the panels down to just above battery voltage and therefore allowing the current flow because the panels are trying to rise in voltage but the PD means they all deliver current at that locked down voltage. Perhaps not ideal flow or max from som epanels but reasonable use of them just the same.
Interested in your reply.
Regards.
Ross
FollowupID:
877349
Follow Up By: Allan B (Member, SunCoast) - Tuesday, Jan 17, 2017 at 13:32
Tuesday, Jan 17, 2017 at 13:32
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Yes certainly they can
Ross. The solar modules have impedance and as you say, in operation the output voltage will drop so that the contribution from parallel panels is somewhat equalised. The degree of equalisation depends on the relative impedances and voltages so the closer the panel specs are then the better equalisation. As a guess I'd suggest that voltages of within 10% would be reasonable, but then it also depends on the panel impedances (read wattage ratings).
FollowupID:
877351
Follow Up By: RMD - Tuesday, Jan 17, 2017 at 14:57
Tuesday, Jan 17, 2017 at 14:57
Thanks Allan (EDIT) Sorry, forgot Roz
Regards
Ross
FollowupID:
877358
Follow Up By: Tim F3 - Tuesday, Jan 17, 2017 at 15:24
Tuesday, Jan 17, 2017 at 15:24
Thanks to both
ross and allen for your replies.
FollowupID:
877361
Follow Up By: Tim F3 - Tuesday, Jan 17, 2017 at 15:33
Tuesday, Jan 17, 2017 at 15:33
Allen
if i simply connect the 2 charged batteries in the vehicle (after disconnecting the 160 watt panels ) in parallel to the vans batteries would i not get a longer run time of the fridge as it could draw on 4 batteries ?
FollowupID:
877362
Follow Up By: Allan B (Member, SunCoast) - Tuesday, Jan 17, 2017 at 17:19
Tuesday, Jan 17, 2017 at 17:19
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Yes Tim, you could parallel the batteries to provide longer run time.
In fact you could probably do so without disconnecting the 160W panels as I have suggested above. It can certainly do no harm to try that. Simply connect the vehicle batteries to the van batteries with 6 B&S (13mm2) cable via 50A Anderson plugs. Be sure to fit fuses (30A) to the cable at each battery. Doing it this way will allow the 160W panels to continue to charge the vehicle batteries.
What load(s) are the vehicle auxiliary batteries currently supplying?
FollowupID:
877368
Follow Up By: Allan B (Member, SunCoast) - Tuesday, Jan 17, 2017 at 17:27
Tuesday, Jan 17, 2017 at 17:27
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Further to my Followup 351 above, the majority of the solar panels on the market have reasonably similar electrical characteristics so can be paralleled with existing (same class) panels without problems and many users would have done so.
However mismatching may not obtain near-full performance. It is best to endeavour to obtain the best possible match to perform as you might wish.
FollowupID:
877369
Follow Up By: Tim F3 - Tuesday, Jan 17, 2017 at 19:10
Tuesday, Jan 17, 2017 at 19:10
Allan , the aux batteries in the vehicle mainly run a 60 litre everkool fridge/freezer constantly (freezer set to around minus 10 c ,fridge section has nice cold beer etc ) and other odds and ends occaisonally eg
hf radio , 600watt inverter , led
camp lights , charge phone and computer .
Thankyou for sharing your knowledge with the
forum.
FollowupID:
877375
Follow Up By: Allan B (Member, SunCoast) - Tuesday, Jan 17, 2017 at 19:19
Tuesday, Jan 17, 2017 at 19:19
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Tim, with that load your 160 Watts of solar input on the vehicle may not always have a lot of excess capacity to export to the van, but if the two battery banks are simply connected together it should sort itself out for the optimum result.
FollowupID:
877377
Follow Up By: Tim F3 - Tuesday, Jan 17, 2017 at 19:35
Tuesday, Jan 17, 2017 at 19:35
Yes , thankyou
FollowupID:
877378
Follow Up By: Tim F3 - Tuesday, Jan 17, 2017 at 22:21
Tuesday, Jan 17, 2017 at 22:21
Allan as a sugestion how i may increase run time of the 240 litre fridge in the van and also run my 60 litte fridge how about the following.....
Have the 160 watt panels on the vehicle charge the auxillary 2 x 100 amp batteries in the vehicle connect this in parrallel to the van 2 x 120 amp batteries to run the 240 litre fridge.
Then have the 60 litre fridge /freezer connected to the 2 batteries running the ignition for the vehicle with a low voltage cut out set above a critical level that starts the vehicle.
Then when the vehicle is started it preferentially charges both start batteries before sending excess charge to the 2 x 100 amp deep cycle batteries in the rear of the vechle and then to the caravan as required..
Your thoughts please...
FollowupID:
877387
Follow Up By: Allan B (Member, SunCoast) - Tuesday, Jan 17, 2017 at 23:08
Tuesday, Jan 17, 2017 at 23:08
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Tim, certainly that would work electrically. But it is not what I would like.
I am apprehensive about drawing fridge load from the cranking batteries when standing, even if they are 'protected' by a low-voltage cutout. I travel very remote and alone so
well maintained crank batteries are precious to me.
Furthermore, crank batteries are not designed to be discharged very far at all. They are intended to supply very high current for a very brief period. Discharging them to depth shortens their life.
However, it could be useful to introduce your vehicle alternator into the auxiliary battery arena. You could connect the vehicle and van auxiliary batteries in parallel and feed your alternator to the vehicle aux battery via a smart isolator. The alternator will contribute charge to the entire aux battery bank although just how much reaches the van will depend on voltage drop along the way. It also depends on the output voltage of the alternator. If you have two cranking batteries it sounds like you maybe drive a 200 series and its alternator output voltage may not be high enough without taking special complex solutions.
By the way, the concept that the alternator will "preferentially charge both start batteries before "sending excess on" is popular but erroneous. What actually happens is that upon engine start, the alternator applies charge to the start batteries and within a few seconds their terminal voltage rises to the point of activating the 'smart' isolator. The alternator is now supplying charge to all connected batteries simultaneously and they each draw current according to their state of discharge.
FollowupID:
877391