Solar Panel

Submitted: Tuesday, Apr 20, 2004 at 21:26

ThreadID: 12231 Views:2719 Replies:4 FollowUps:12

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Member Eric

Guys , I was looking at connecting my solar panel to the vehicles baterries , when the vehicle is switched off . Is this ok?, or am i missing something . The way i was going to do it , was to connect the panel to my BP Solar Regulator , and the reg to the batteries , through a relay or switch . My idea was to top up batteries when the vehicle is not running , eg , so the fridge dosnt run batteries down . I know it only will work during the day , but just a thought , since I had the panel .

Thanks in advance

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Reply By: Member - Andrew R (VIC) - Tuesday, Apr 20, 2004 at 21:36

Reply By: Member - Toonfish - Tuesday, Apr 20, 2004 at 23:27

Reply By: joc45 - Wednesday, Apr 21, 2004 at 00:08

Wednesday, Apr 21, 2004 at 00:08

Hi, Eric,
You can leave the solar regulator permanently across the battery without worrying about an isolating switch/relay. If the battery volts are high enough when the engine is running, the solar system will not charge. If the engine is idling with only a small charge, the solar may assist in charging. After dark, the regulator stops any back-flow of current, and _Affordable_Storage_Drawers.aspx a pittance itself, so no risk of the solar system discharging the battery.
The car's electrical system will not be affected if you are running a dual battery system with isolator. Even if you are not using a dual battery system with isolator, the max battery volts from solar charging would be about 14.5-15v on the car's system.
Gerry

AnswerID: 55243

Follow Up By: William - Wednesday, Apr 21, 2004 at 07:58

Wednesday, Apr 21, 2004 at 07:58

Joc45 no no no no no no.

What happens is the alternator regulator senses the high voltage from the solar panel and consequently the alternator shuts down charging.

The best way is to put in a Bosch type mini-relay fitted with a diode and capacitor so it stays latched while cranking to disconnect the solar regulator from the main battery. If you are using an auxiliary battery and Redarc type battery isolator, you will be forced to put a diode in the supply line after the Redarc.

FollowupID: 317017

Follow Up By: Member Eric - Wednesday, Apr 21, 2004 at 08:26

Wednesday, Apr 21, 2004 at 08:26

I think I will agree with William here . I think he is right. Thinking about it now , why would the altinator charge if it's sensing 15 V on the battery side .

William , My email address is wholesalecars@optusnet.com.au. If you can be bothered sending a wiring diagram , it would be appreciated

FollowupID: 317022

Follow Up By: William - Wednesday, Apr 21, 2004 at 08:29

Wednesday, Apr 21, 2004 at 08:29

I can always be bothered sending things to those that ask.
Give me a brief explanation of your system and I will be happy to send you one.

FollowupID: 317026

Follow Up By: Peter - Wednesday, Apr 21, 2004 at 08:48

Wednesday, Apr 21, 2004 at 08:48

I have done this and it is quite easy.
My solar panels are on a long lead so as the truck can be parked in the shade and panel in sun. I have just used hella power plug on end of lead and a mounted socket mounted in back of truck. This is wired and fused to the battery. I am using a plasmtronics pr1210 regulator which fit connection box on back of panel.

At night i generally unplug panel and put near or in truck.

on previous truck had panel on roof and wired in with a relay so when engine was running the relay open circuted the solar and battey was charged by alternator.

All works and worked well in both configerations

Peter

FollowupID: 317028

Follow Up By: Rosscoe - Wednesday, Apr 21, 2004 at 09:52

Wednesday, Apr 21, 2004 at 09:52

Is there any risk of damage to the vehicle's computerised engine management system if you connect the Solar Panels/Solar Regulator to the vehicle's battery without isolating it from the system. ie can the computer handle 15 V DC seeing the normal voltage regulator controls around 14.2V DC.

FollowupID: 317038

Follow Up By: William - Wednesday, Apr 21, 2004 at 12:41

Wednesday, Apr 21, 2004 at 12:41

Rosscoe you could not say yes or no regarding will it do any damage. It would be entirely dependent on the design of the vehicle electronics.
I have seen about 5 vehicles that have had flat batteries when they installed solar panels because they hooked the panels directly up to the vehicle battery. I would not do it, as there should be no need to go down that path. I really do not like doing anything to a modern vehicle that could interfere with the vehicle electronics. Many vehicle computer systems rely on a lot of information from the alternator, so anything other than power load/charging that could interfere with the alternator information, I would avoid.

FollowupID: 317066

Follow Up By: Peter - Wednesday, Apr 21, 2004 at 15:12

Wednesday, Apr 21, 2004 at 15:12

I suppose I forgot to say my setup is only for the Aux Battery. This is behind an Isolator (Rotronics).
You need to watch out that isolator is capable of having solar connected. Any of the smart Solenoids, Solenoids and manual switches will work ok as well.

This means that this is isolated from main battey system.

Peter

FollowupID: 317102

Follow Up By: Rosscoe - Wednesday, Apr 21, 2004 at 16:11

Wednesday, Apr 21, 2004 at 16:11

Hi Peter,

I have a dual battery system in my car as well. I use a Sure Products separator.
Does this device prevent the auxilliary battery being connected to the main battery at all times or only when starting or when the cranking battery is below a specified voltage level.

It would simplify things a lot for me if I could plug a solar system into my Anderson plug at the rear of the vehicle leaving all things connected. I suppose I could install a manual isolator for the times I want to connect solar.

I have an Engel fridge directly wired via its own Engel socket, fuse, circuit breaker and heavy cable to the auxilliary battery. Will it handle the 15 Volts or so delivered by the solar regulator when the battery is approaching 100% charge?

FollowupID: 317119

Follow Up By: joc45 - Wednesday, Apr 21, 2004 at 19:44

Wednesday, Apr 21, 2004 at 19:44

William, yes, yes, yes, etc
I was half-expecting to get howled down on this one.
If the solar system has the battery already charged at (say) 14.2v, then the electronics of the alternator stops the alternator charging. So what? It stops charging coz the battery is already high enough in voltage, just what it's supposed to do. When the volts drop below the alternator threhshold, the alternator just starts charging again. Easy as that.
Re the risk battery volts going to 15v, I could not believe that an automotive electronics designer would create a system, including the ECU, which could not take 0.5v above its normal max of 14.5v. I quote 15v, since some intelligent solar chargers do take the battery briefly up to 15.0v before dropping back to about 14.2v, otherwise the simpler regulators run at 14.0-14.5v. Some automotive alternators (esp on diesels) run at 15v anyway. It's just not a problem.
Do not be put off by the fact that the solar panels put out about 22v open-circuit. This voltage drops right back to the battery voltage due to the low internal resistance of the battery and the high internal resistance fo the solar panels. If the battery has a high internal resistance, such as when it's flat, then the solar regulator immediately cuts off the panel the moment the volts reach 15v max. Having said that, I would never connect a solar panel directly to a vehicle battery without a solar regulator.
Re running batteries flat, the regulator _Affordable_Storage_Drawers.aspx minimal power from the battery, like a few milliamps. This just could not run a battery down even if left with total darkness for weeks. I mean, these things are fitted to battery banks on unmanned radio sites for years on end without a problem.
Gerry

FollowupID: 317177

Follow Up By: Rosscoe - Thursday, Apr 22, 2004 at 09:00

Thursday, Apr 22, 2004 at 09:00

Guys,
I was of the understanding that "good" solar regulators included diodes to prevent current reversal at night.
Re design of the ECU. I am a sceptic re automotive electrical design. Every cent is taken into account. You just have to look at the wire size to accessory sockets and lack of tail light fittings in cars like the NM and NP Pajero.
I am not sure I want to risk a $7000.00 computer on the belief that some engineer got his sums right or that the spec was not conservative.
Perhaps the cost of a manual isolator to separate the auxuliary battery from the vehicle's electrical signal is worth considering. Pretty cheap insurance methinks.
What about 15V to the Engel compressor. Do you think tha'd be OK

FollowupID: 317288

Follow Up By: joc45 - Thursday, Apr 22, 2004 at 23:07

Thursday, Apr 22, 2004 at 23:07

Hi Rosscoe,
The diodes are usually on the input to the regulator; ie on the solar panel side, since the reg output is its source of volt sensing from the battery. The diodes are to block volts across the panels when there is no light.
Early Engels were rated to 15v (tho that was the limit), later Engels run 12-24v, so should not be a prob. Danfoss compressors no probs either at 15v. But I found that if the solar regulator was in "boost" mode; ie running up to 15v, and the fridge was running, the fridge load caused the volts to drop back to about 14v or less anyway, so it was impossible for the fridge to run at the full boost voltage of 15v.
Gerry

FollowupID: 317464