Tech help needed.

[Wildman]

I am looking for a relay that includes one pair of normally open contacts and one pair of normally closed contacts. i.e two independant switches. To take the max charge current from the alternator (which will be the greater of the two feeds). The idea being to switch off the solar feed to the regulator when the engine is running so that neither feed confuses the other.not sure what the max charge amps could be from the alternator, with or without a B2B charger fitted.
Anyone any suggestions as to part numbers/location etc.

 

[pappajohn]

Something like this Roger.

Used on 12v recovery winches.......2 n/o + 2 n/c for wind and unwind operation.

Rated at 100a continuous...300a peak.

Broken Link Removed

 

[tonyidle]

Neither feed will confuse the other. Whichever is providing the highest voltage at any given moment is the one doing the work: the other will be doing nothing. You don't need added complication in the form of a relay.

 

[Wildman]

if the solar is charging at over 13v then the alternator regulation kicks in and thinks the battery is almost fully charged and reduces output accordingly or they both reduce output. as the respective regulators see the other voltage and confuse the charge for battery level and even after an 8 hour run batteries are not recharged.
Your hypothesis would apply if both voltage sources passed through a single regulator however there are separate regulators in the solar and the alternator.
However am ready to be convinced I am wrong.

 

[mjltigger]

if the solar is charging at over 13v then the alternator regulation kicks in and thinks the battery is almost fully charged and reduces output accordingly or they both reduce output. as the respective regulators see the other voltage and confuse the charge for battery level and even after an 8 hour run batteries are not recharged.

I've proved often that I'm useless at this sort of thing but I was told all I needed to separate multiple charging inputs was a diode

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[pappajohn]

I've proved often that I'm useless at this sort of thing but I was told all I needed to separate multiple charging inputs was a diode

Actually, thats a very good point......but.....

You cant put a blocking diode in a charging circuit.....the charger, or in the case of solar...the regulator, needs to monitor the battery voltage state or it will continue to charge after the battery has reached capacity.
a diode would stop the charger mnitoring the battery.
.

 

[Wildman]

so what is the general consensus of opinion am I correct or mistaken, come on Eddie banned bits you are the hexpert.

 

[movan]

Crumbs, not being sarcastic, honest. You lot arn't half clever... I havn't got a clue what you are talking about... Anyway, hoping this post bumps it up a bitz.

 

[Techno]

The alternator works at 14.4 volts this will put any solar regulator into float mode 13.2/13.4volts
Usually the alternators target voltage is a minimum of 13.8 and thus it will keep up output (current) to achieve that.

 

[Wildman]

solar has an input voltage of approx 17v and regulator maintains 13.8v on the battery as well. How does the alternator decide if the voltage is sees is the solar or battery level. I seem to remember you have a posh Ctec system that sorts it for you.

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[eddie]

I wouldn't bother to be perfectly honest unless, I was designing a bespoke system from scratch. What sort of wattage are we talking about?

Eddie

 

[Techno]

Get a better regulator that that has 3 stage charging instead of pouring money into relays.

13.8 is too high for a float charge and could overcharge a full battery

 

[Wildman]

I wouldn't bother to be perfectly honest unless, I was designing a bespoke system from scratch. What sort of wattage are we talking about?

Eddie

160W solar into 2 x 120 amp/hr batteries, I had problems charging when both were connected so disconnected the alt as we spend more time static. Rather than put 2 switches in a relay would do the job cheaply enough
We do have a second identical bank without any Alt connection that also has 160W solar, just for the TV.

 

[Wildman]

Get a better regulator that that has 3 stage charging instead of pouring money into relays.

13.8 is too high for a float charge and could overcharge a full battery

a 3 stage regulator is silly money compared to a relay at £13.95. The batteries in one bank are 6 years old and still doing the business. 13.7v today after heavy use the past 4 days. So perhaps it does not float charge rathe it switches off the solar once the battery is fully charged. Besides only need alt charging in the winter when sun is low in the sky. So still need both

 

[Techno]

What regulator is it you have? even cheap ones should have a float charge certainly not just 13.8 full time

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[Don Quixote]

a 3 stage regulator is silly money compared to a relay at £13.95. The batteries in one bank are 6 years old and still doing the business. 13.7v today after heavy use the past 4 days. So perhaps it does not float charge rathe it switches off the solar once the battery is fully charged. Besides only need alt charging in the winter when sun is low in the sky. So still need both

Perhaps something like this:

 

[Wildman]

I never said it was 13.8 full time the charge depends on the state of the battery and load at any given time plus of course sun available. The regulator was an expencive one and not the problem. A £200 regulator will not increase the charge when there is no sun. The solar setup is fine, problems only arise when the alternator is charging at the same time.

 

[Techno]

There you go then
As I said , when your regulator sees 14.4 volts from the alternator it will go into float mode and thus not interfere

 

[Techno]

solar has an input voltage of approx 17v and regulator maintains 13.8v on the battery as well. How does the alternator decide if the voltage is sees is the solar or battery level. I seem to remember you have a posh Ctec system that sorts it for you.

As I said in post above

and as I said in my first reply
The alternator works at 14.4 volts this will put any solar regulator into float mode 13.2/13.4volts
Usually the alternators target voltage is a minimum of 13.8 and thus it will keep up output (current) to achieve that.

 

[Techno]

The float mode voltage (solar regulator) as I stated is well below an alternators target battery voltage so the alternator will continue to ouput whatever current is needed at 14.4 volts to achieve the target voltage.

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[Wildman]

in theory yes, in practice that did not happen. I disconnected the alt 2 years ago because I was having problems and its too far back to remember exactly what happened. But I seem to remember driving from Scotland to Devon and arriving with a low charge in the leisure battery, no radio on, fridge on gas it should have charged in that time. 8-10 hour drive and the batteries were new, have been good since I disconnected the Alt in summer anyway. It is winter I need the extra charge and don't use sites or EHU.

 

[Techno]

Carry on then but how do you know it is not happening? The charge to the liesure batteries is only modest without the intervention of a B2B if two batteries were very low it is unlikely they would be well charged in that time.
Chances are you would have got more charge from the alternator if you'd put the fridge on 12 volts

 

[Wildman]

Just going in circles Andy but thanks for the input.With solar disconnected the alt charges normally (when connected), connect the solar and the charge to the leisure batteries is reduced as shown on the built in amp/volt meter. hence my simple reasoning to disconnect the solar when the engine is running.