Solar Regulators and Distance from Battery issues

I recently purchased a 100w EvaKool folding solar panel set, that has a solar regulator/controller (20 A - brand is EPHC ) mounted on the rear of the panel. From the regulator, there is pretty heavy gauge twin wire of about 3 metres with an anderson plug termination. In my camper trailer rig, I was hoping to mount an anderson plug on both sides as a connection point for the panels however I am not sure if that distance of wiring (4 or so metres) is placing the regulator/controller too far from the battery. I think I read somewhere a while back that you need to mount the regulator as close as possible, and in any case under 1 metre, from the battery so it can accurately measure the voltage for its cut in/out (as the voltage drop over the distance of wire would make it measure incorrectly). Can anyone tell me if this is an issue? or am I just making a simple job complicated.

Thanks, Matt.
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Reply By: Robin Miller - Wednesday, May 26, 2010 at 22:55

Wednesday, May 26, 2010 at 22:55
Hi Matt

The general rule is closer is better but its not an issue if you use thick wire , in your case 8mm sq copper for the + and - leads will mean that 3 meters is no problem.

As you seem to guess 1 meter of wire of 4mm sq has same drop as 2 meters of wire 8mm sq.
Robin Miller

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AnswerID: 418324

Reply By: Maîneÿ . . .- Wednesday, May 26, 2010 at 23:43

Wednesday, May 26, 2010 at 23:43
Forget about the voltage loss just for a while and think about what happens when dust is blown into the regulator, or is the reg *water proof* because sometimes it will even get wet too...

Now go put it beside the battery - where it belongs and will work more efficiently anyway and will be out of the dust and rain too

Maîneÿ . . .
AnswerID: 418334

Reply By: ChipPunk - Wednesday, May 26, 2010 at 23:55

Wednesday, May 26, 2010 at 23:55

Regulation is for the battery. Voltages elsewhere are irrelevant.

IE - If you regulator is set to 14.4V and there is a 1V drop from it to the battery, then the battery is undercharging by 1V. (Maybe the panels are putting out 17.4V so the regulator "removes 3V".)

If the regulator is nearer the battery - or rather - if there is zero voltage drop between regulator and battery - the the battery gets its full 14.4V. (Maybe the panels still put out 17.4V but instead they have a 1V or 2V drop to the regulator - but that doesn't matter since the panel's 17.4V needs to drop to 14.4V anyhow.

And in situations where there is not excessive panel voltage, you still want maximum voltage to the battery.

So yes - regulator close to the battery &/or thick wires.
The regulator needs to sense the battery voltage, not the upstream cable voltage.
AnswerID: 418340

Reply By: Member - Rod N (QLD) - Thursday, May 27, 2010 at 07:46

Thursday, May 27, 2010 at 07:46
If you put the regulator near the battery you will need separate wiring from the panel to it. That also means a separate connector. You can't use the wiring and connector from the tug to camper trailer, if you have such a setup.

I asked a similar question in this this discussion.Solar Regulator Placement

"If you use a portable/foldup panel and want to connect it to the lead that would normally be connected to the vehicle, where should the regulator be connected :?: If it was close to the battery can the vehicle power be fed through it? ie one lead to be used for 2 purposes."

"No - the tugs alternator does not provide sufficient voltage to drive a solar regulator/controller."

AnswerID: 418358

Follow Up By: ChipPunk - Thursday, May 27, 2010 at 09:49

Thursday, May 27, 2010 at 09:49
Ambiguous and non sensicle. (An alternator "driving" a solar regulator??!! Do they mean "common connection" or is there something I am not understanding?)

Collyn Rivers and similar seem to restate normal practice - the regulator (like an alternator) must sense the battery voltage - not some point in between....

Nevertheless, as I wrote above, any voltage drop between the regulator and the battery means the battery is being undercharged (whether relative to available power/voltage, its nominal 14.4V charge voltage, or nominal 13.8V float voltage).

I'm not sure where they get their "less float voltage" for AGM batteries - they are still lead-acid so the normal 14.4V & 13.8V targets/limits apply.
Whilst AGMs may do ok with a lower float voltage (less risk of sulfation), why reduce it from the norm? (Temperature compensation is a different issue, but since our solar regulators rarely have a specific Sense input, they are unlikely to provide remote temperature sensing. Or has that changed?)

FollowupID: 688423

Reply By: Ozhumvee - Thursday, May 27, 2010 at 08:21

Thursday, May 27, 2010 at 08:21
If you are using a portable panel that is being connected of a morning and stowed away at night then leave the regulator out all together. There is no way a portable panel will overcharge a battery that is in use running a fridge etc.
AnswerID: 418364

Follow Up By: Thomo1970 - Wednesday, Jun 09, 2010 at 12:06

Wednesday, Jun 09, 2010 at 12:06
Hi Peter,

I would suggest that you would need to be very careful in doing this.

For example, if you had a battery that was near full and a small fridge that was already down to temp', so the power usage would be quite low (eg 1.5 amps / hour or less).
The solar panel in this post is a 100 watt, or around 6.5 amps, so I will use that in this example.

If there was good sunlight for 7.5 hours (Australian average) then there would be an extra 37.5 amps put into your battery after the fridge has used what it needed.

For a 100 amp/hour battery, that could potentially put an extra 30% into your battery that it isn't designed for.

I understand what you are saying, I'm trying to make sure that people are careful running solar panels without a regulator.

Thanks, Brodie
Warranty Manager
FollowupID: 690318

Reply By: Thomo1970 - Wednesday, Jun 09, 2010 at 11:51

Wednesday, Jun 09, 2010 at 11:51
Hi Matt,

The thickness of the cable included with the Evakool 100 watt folding Solar Panel is such that the voltage drop over it's length should be less than 0.5 volts.
Therefore, if the voltage it was aiming for was 14.4 volts at the battery, then it would stop at 13.9 volts which is very close to full for most batteries.

I do believe the drop will be less than that due to the amount amps, but I haven't yet done any exact measurement.

Thanks, Brodie
Warranty Manager
AnswerID: 420145

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