A couple of very basic questions (1 Viewer)

[GeriatricWanderer]

Before I start spending money on the bits and bobs necessary to put a small panel on my pop-top camper, I want to understand the basic circuitry....... and I'm starting with a zero knowledge so you'll have to excuse the terminology.
So, my first question is: The LB is charged from the alternator when the engine is running or from EHU when hooked up. If a solar panel is added is it the mptt controller that detects any other charging source and prevents or controls the solar charge reaching the battery? If so, where does that charge go?

I told you I was coming from a zero knowledge base.

 

[funflair]

Yes the solar controller MPPT or not (MPPT is best though) controls the charge from the solar panel to the LB's as long as the controller is set to the correct battery type it will all work itself out, the solar controller goes between the solar pane/panels and the LB's with suitable fuses.

Martin

 

[KeithMak]

If so, where does that charge go?

It goes nowhere because it is not produced.

Batteries control charging, not chargers, alternators or solar controllers.

If the battery does not want anything, the above do not produce it.

You possibly have an alternator that can produce 100 amps, a charger that supply 20 amps but they will not produce that amount unless the batteries require it so adding solar will not change that just give another alternative.

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[tonyidle]

Before I start spending money on the bits and bobs necessary to put a small panel on my pop-top camper, I want to understand the basic circuitry....... and I'm starting with a zero knowledge so you'll have to excuse the terminology.
So, my first question is: The LB is charged from the alternator when the engine is running or from EHU when hooked up. If a solar panel is added is it the mptt controller that detects any other charging source and prevents or controls the solar charge reaching the battery? If so, where does that charge go?

I told you I was coming from a zero knowledge base.

Your panel should connect directly to a decent regulator which should itself connect directly to the battery. Having three possible sources (EHU, alternator, solar) available to the battery causes many owners to worry unnecessarily about interference between them. They will sort out between themselves which should be charging at any given time - all you need to consider is wiring your panel as above.

Charge regulators whether solar, EHU, or built into the alternator, can "dispose" of the excess in a few different ways none of which require it to go anywhere . And, again, none of which should concern the user.

(and KM above is absolutely correct)

 

[Sidney]

Your panel should connect directly to a decent regulator which should itself connect directly to the battery. Having three possible sources (EHU, alternator, solar) available to the battery causes many owners to worry unnecessarily about interference between them. They will sort out between themselves which should be charging at any given time - all you need to consider is wiring your panel as above.

Charge regulators whether solar, EHU, or built into the alternator, can "dispose" of the excess in a few different ways none of which require it to go anywhere . And, again, none of which should concern the user.

(and KM above is absolutely correct)

But do they really sort themselves out?

Its high summer, you've stopped in an aire overnight and in the morning the leisure batteries are low.

You drive off, but the solar panel is already putting 5 amps into your battery at 14.4v(?) the alternator can see 14.4 volts at the battery (with the charge coming from the solar regulator) and assumes nothing is required. Two hours later you reach your destination and the leisure batteries have only received a 5 amp charge for two hours rather than getting 25+ amps from the alternator.

Or am I wrong?

 

[aandncaravan]

If a battery decides what power is taken from a charging source, how come it is possible to overcharge them?

And if the battery decides how much it takes why do chargers have different charge modes to prevent 'overcharge'?

The batteries do have a big say in what they 'require' but a Charger (for this post it means all types Alternator, Solar or Mains) will still put out up to 14.7v (dependent on the battery) and a small amount of current when a battery is 'Full'.
It is, generally, the amount of current that will vary dependent on what the battery decides it will draw, but the voltage is decided solely by the charger.

Modern chargers, again this applies to all chargers Solar, Mains, etc. use different technology to work out what state the battery is in to select the appropriate charge mode. So for instance some chargers will monitor the current being drawn and when it drops below a certain level it will reduce the voltage to 'Trickle/Float/Maintenance' mode of between 13.0 and 14.2v.
Even in this mode current will be 'forced' into the battery, albeit a small amount. That is why the Float voltage is so important in not 'overcharging a battery to the point it will slowly Gas and lose fluid.
For some batteries, like Lead Antimony Acid, to not be overcharged, the Float needs to be as low as 13.0v - 13.2v.

Some chargers monitor the battery voltage, not the current and if they 'see' 14.4v at the battery terminals they will drop into Float mode.
Some Solar regs do neither. They will always wake up each day in 'full charge' mode, regardless of the fact they might have been in 'float' at Sunset the night before, and only drop down to Float once a 'timer' (typically an hour) once the battery shows it's full.
When a van is in storage this 'one hour overcharge' every day can have quite an adverse impact, especially on Antimony Lead batteries.

Others Solar Regs will check out the battery voltage before they start up and decide what charge mode to take, but these are less common.

Obviously some older chargers had a fixed 13.5v, which changes things again, but we won't cover that here.

So to answer the question above :
If you have 3 modern charging systems all charging the same FULL battery and they all go into Float mode they will ALL put in a smal Float charge. It will be the minimum possible, but enough to Gas and corrode most batteries.

If you have 3 modern charging systems all charging the same 'EMPTY' battery they may act in completly different ways dependent on the Technology and the voltage outputs of each. Two may drop straight to Float, leaving the third to supply all the charge or they may contribute a third each.

Some Alternators are Voltage driven, if they 'see' a full battery (13+v) they will back off the current. Some will even drop to a lower voltage charge rate, like 13.0v.

If there is a B2B supplying the power into the batteries all sorts of variables are possible as these can 'massage' the voltages to a higher than normal Alternator level. They don't all do it the same way.

Of course the batteries themselves will also affect what happens. Gel, for instance take a much lower current charge and why they take twice as long to charge.

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[pyro]

(don't forget to let your insurers know if you do decide to install SPs - see recent threads)

 

[funflair]

But do they really sort themselves out?

Its high summer, you've stopped in an aire overnight and in the morning the leisure batteries are low.

You drive off, but the solar panel is already putting 5 amps into your battery at 14.4v(?) the alternator can see 14.4 volts at the battery (with the charge coming from the solar regulator) and assumes nothing is required. Two hours later you reach your destination and the leisure batteries have only received a 5 amp charge for two hours rather than getting 25+ amps from the alternator.

Or am I wrong?

If your batteries are low putting 5amps into them won't raise the terminal voltage to 14.4v so the alternator will still do its job.

That's the way I see it anyway, we have two MPPT controllers and if the demand is there from the batteries they will both work flat out but when one sees a raised terminal voltage it will cut back to next to no charge and let the other one sort it out on its own.

Martin

 

[GeriatricWanderer]

Thanks guys
Good to have a better understanding how everyday things work.
Also some very helpful people at www.motorhomesolarsolutions.co.uk

Now, can anyone help me to programme my TV video cassette recorder as I don't have any grandkids to show me?

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[Abacist]

Thanks guys
Now, can anyone help me to programme my TV video cassette recorder as I don't have any grandkids to show me?

Kids are amazing learners aren't they. Our latest Grandson who has just turned 1 and started to walk 2 weeks before his birthday hunts for the TV remote as soon as he arrives if the TV is on and then walks around pointing the remote at the TV pressing the buttons. He can change channels and got into something the other day and it took me 5 minutes to get the TV back as it should be.

Sorry can't help with the VCR - isn't that as antique as you?

 

[GeriatricWanderer]

OK - the story so far:
The panel is temporarily fitted to the roof. As it's a pop top sunrise roof I decided to bolt the brackets rather than just "stick". I found a good route for the cables to pass through into the interior but.......... the cables, both SP to controller and battery to controller, are as I expected, quite a heavy gauge and seem to be a very tight/impossible fit into the ports on the controller. I'm in those process of locating some pin terminals but I do get the feeling that either the cables are too heavy or the controller ports too small. It was all bought as a kit from a motorhome solar specialist who tells me it should be a tight but not impossible fit.

Is this a problem anyone else has encountered?

 

[Stealaway]

My 2 x 125W solar panels are wired with 4mm cables, any bigger would probably be unnecessary - and a problem to fit into the terminals.

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[mitzimad]

mine are 6mm and fit in the terminals ok

 

[GeriatricWanderer]

Thanks guys - I'v just looked closely at what I ordered versus what they sent me and it's definitely the wrong controller so back it goes.