How to "Solar Charge" your Starter Battery

wildebus

wildebus

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Seems to be lots of interest about how to get some charge into your Starter Battery from your Solar Panels.

The following is a way to replicate a setup that is very common amongst Self-Builds with basic Split-Charge setups, but this one is focused on the Solar Side rather than the Alternator.

Use a TEC 3M Relay (often used for Towbar setups for Caravans)
s-l1600.jpg

Connect the Leisure Battery (via a 30A Fuse) to Terminal 12
Connect the Starter Battery (via a 30A Fuse) to Terminal 6 or 2
Connect Ground to Terminal 0V

When the Leisure Battery reaches a certain voltage (around 13.3V), the relay will enable and the Starter Battery will be connected to the Leisure Battery and will get charged as well.
Once the Leisure Battery drops below a certain voltage (around 12.8V), the relay will turn off and the Starter Battery will disconnect from the Leisure side of the camper.

So in practical terms, when the solar panels start to provide a charge into the Leisure Battery, the relay enables; and once dark and the charging voltage goes, the Leisure Battery voltage will start to drop and the relay disables, ensuring that any power demands in the evening don't come from the Starter Battery and that is safe from over-discharge.

Also, the same effect will happen if you use a mains battery charger on the Leisure Battery, so you can charge both batteries with a single charger.
It might be worth fitting a switch to stop the relay coming on for times you don't want to have the Starter Battery connected during a Leisure side charge - in which case, fit a switch between the 0V and the Ground as that is the lowest power signal line so 'nicest' for a switch.
Good source for relay is https://www.pfjones.co.uk/towbar-electrics-charge-relay-tec3m.html
Cost of the above setup is under £15 including Relay, switch, fuse holders and cable.

The above info should be applied depending on what setup you have in your van. Like all wiring, it may or may not be appropriate to your requirement or configuration.

Enjoy :)
 
You know far more than me about electricity, and I took the simplton's approach of installing a BatteryMaster.

My solar panel keeps an eye on both batteries, and I no longer have to think about either.

I'm a worrier by nature, so it's one less thing for me to thing to worry about.
 
Despite all the posts (which I believe) and the possible need for extra kit/wiring..

BTW the solution posted looks VG if you need it

We are OK...
We have a Ctek power unit .
We have a solar panel (120W) and MPPT controller..
Provided I leave the master switch for the Ctek switched on
I have consistently (even always) observed (by checking voltages on both batteries using the Ctek panel indicator) that the Engine battery gets charged .
Probably only when the LB is "full".
Thus over the winter the master switch on the panel is left on ..other switches off.
So the LB gets no use...The EB powers the alarm.
Both batteries are fully maintained by the solar panel over the winter !
Again direct observation/checking
 
You could add a voltage booster on the output? Set it at ~27.6V to give a constant maintenance charge when solar active and would match what the alternator would output.
Something like this for example - https://www.amazon.co.uk/Boost-Converter-Yeeco-Voltage-Regulator/dp/B014IVDIXM/ref=sr_1_14?
I use a similar unit to make sure the voltage to the diesel heater doesn't drop below ~12.5V under load (saves having to start the engine to boost the voltage when starting it sometimes)
 
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Reading this thread with interest as I only have my solar charging the leisure batteries.
To be honest after using my pvc year round for 2 1/2 years I have never had an issue with a low engine battery. I can leave it stood for 3 weeks on my drive without ehu and there is always sufficient charge to start the engine. When on my travels it obviously gets charged when on the move.
I suppose if I had my vehicle stood in a storage facility over the winter period as many do I would need a means of keeping the engine battery charged, but as I use it at least every other week year round I will leave things as is.
 
Obanboy666 said:
Reading this thread with interest as I only have my solar charging the leisure batteries.
To be honest after using my pvc year round for 2 1/2 years I have never had an issue with a low engine battery. I can leave it stood for 3 weeks on my drive without ehu and there is always sufficient charge to start the engine. When on my travels it obviously gets charged when on the move.
I suppose if I had my vehicle stood in a storage facility over the winter period as many do I would need a means of keeping the engine battery charged, but as I use it at least every other week year round I will leave things as is.
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The main benefit I see is the ability to have the Starter Battery getting charged 'for free' when laid up unused for a few weeks.
Many expensive motorhomes come with fancy PDU (Power Distribution Units) that have built-in power transference to a greater or lesser degree, but I come from a self-conversion background where this is not the case at all and you have to add in these features - either by buying ready-made (but expensive) systems, or adding components for specific functions :)
 
I wish you had posted this earlier, I have just bought and fitted a VSR to allow the vehicle battery to receive solar charge and the leisure battery to receive alternator charge. I am also about to remove a towbar as I don't want or need it and of course it has a TEC3M relay exactly as your picture.
Thanks for the info anyway, really helpful stuff like this in plain English is so rare.
Better timing for me next time I hope ;-)

K
 
Vanterrier said:
I wish you had posted this earlier, I have just bought and fitted a VSR to allow the vehicle battery to receive solar charge and the leisure battery to receive alternator charge. I am also about to remove a towbar as I don't want or need it and of course it has a TEC3M relay exactly as your picture.
Thanks for the info anyway, really helpful stuff like this in plain English is so rare.
Better timing for me next time I hope ;-)

K
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The TEC 3M is a fairly low-power relay at just 30A and is uni-directional sensing.
For your requirement, you would need a bi-directional sensing Relay (so Leisure Charge from Alternator PLUS Starter Charge from Solar) and also probably a higher power unit for todays bigger batteries, so I would say you have actually fitted just the right VSR in fact (y)
 
Vanterrier said:
I wish you had posted this earlier, I have just bought and fitted a VSR to allow the vehicle battery to receive solar charge and the leisure battery to receive alternator charge. I am also about to remove a towbar as I don't want or need it and of course it has a TEC3M relay exactly as your picture.
Thanks for the info anyway, really helpful stuff like this in plain English is so rare.
Better timing for me next time I hope ;-)

K
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If you ever require pulled out somewhere the t/bar will be handy,also stops rear end damage from high verges and tail gaters.
 
chas142 said:
Just to check, is your vehicle 24 volt full time, or is it 12 volt running 24 volt starting, a system used by Mercedes on some of their vehicles?
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The base is a daf truck, everything is 24v. All of the habitation stuff is 12v.
 
I have a meter fitted with mine and I can change what percentage of the solar power goes to which battery. I therefore have it set so that in the winter when the van does not get much usage it give ninety percent to the starter battery to keep the alarm running fully. In the summer or when we are touring I have it sixty leisure forty starter.

Bernie
 
I'm interested in that Yeeco voltage step up unit to help our Eberspacher startup without cutting out. Will it pass enough current though ? I'm sure I've seen the heater draw 12amps for a short while and that Yeeco seems to be limited to 8amps output. Any advice appreciated.
 
motoroamer said:
I'm interested in that Yeeco voltage step up unit to help our Eberspacher startup without cutting out. Will it pass enough current though ? I'm sure I've seen the heater draw 12amps for a short while and that Yeeco seems to be limited to 8amps output. Any advice appreciated.
Click to expand...

Bigger ones are available. The two ebers on the truck are actually 24v, but running from a 12v supply. 10A I found in the UK and that seems to be ok, but reading the eber specs that is right on the limit.

https://m.ebay.co.uk/orderDetails?itemId=202277934013&txnId=1737266046010

That's the 15A I bought from China, it arrived in good time and works fine so far. Doesn't even begin to get warm.

Edit to add, you might be talking something else lol.
 
St3v3 said:
Bigger ones are available. The two ebers on the truck are actually 24v, but running from a 12v supply. 10A I found in the UK and that seems to be ok, but reading the eber specs that is right on the limit.

https://m.ebay.co.uk/orderDetails?itemId=202277934013&txnId=1737266046010

That's the 15A I bought from China, it arrived in good time and works fine so far. Doesn't even begin to get warm.

Edit to add, you might be talking something else lol.
Click to expand...
Your link takes me to my recently viewed items.o_O
 
wildebus said:
The last bit of the conversation seems to be two different topics mixed together :)
If a good reliable "full time" 12V to 24V converter is needed, then this is a quality, if expensive, option - http://onboardenergydirect.co.uk/shop/victron-orion-dc-dc-converter-12-24-20a.html#SID=27

If the requirement is to boost 12V in order to run a 12V heater without the volt drop, then this unit is powerful enough for a Eber D2 Airtronic or Chinese Heater - https://amzn.to/2CoZiWs
Click to expand...
Check out the Discounts section, code for 15% off on the Victron, if you go for that, from onboardenergydirect.co.uk.
 
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