12V Solar panel load sharing to 2 x DCDC chargers (One for the 12v/Solar gurus)

[Hodge]

Hey fellas. This one is for the Solar and 12V wizards here.
I recently upgraded my Aux battery setup. I now have a Intervolt DCC Pro Version 2 charger, feeding a 120AH Itechworld lithium battery. It charges super quick and can keep volts and run till Covids over...
I've been mislead though. I got told the Intervolt charges the "main" battery, in certain scenarios under solar. For instance when the Aux battery is full, it will trickle charge the main. I like this feature very much.
Problem is, I have the V.2 of the Intervolt charger. Which has been upgraded from V.1 to cope with Lithiums and other features. But it seems they have taken away the feature to charge the main OUT of the V.2. I didn't know this and it's not stated anywhere...
But it's All good, regardless of that I like the unit and will keep it.

This brings me to my question. I still have my Ctek unit. And is still more or less fitted at the back of the car. And would like to utilize this to charge the MAIN from solar.
But I have one solar panel. So the two chargers will have to share the watts coming out of the panel.
Is there anything wrong with 2 DCDC charges sharing one unregulated panel?

My theory is, the Lithium will charge through the Intervolt super fast, and it will stop sucking juice out of the panel, therefore the charge available out of the panels will now be used by the Ctek to charge the Main.

Am I wasting my time here ?

http://www.nissanpatrol.com.au/forums/attachment.php?attachmentid=82179&stc=1

[Hodge]

I should mention the Ctek D250sa is busted. The internal Alternator charge 30A fuse is stuffed. Solar works flawlessly. So instead of throwing it away, I figured I'd utilize it to charge the main.

[Cuppa]

No idea, never seen it done before, but I guess that doesn't mean it wont work. Not sure if it poses a risk, although I'd guess the worst that can happen is that the two chargers suck a bit of solar & confuse each other, resulting one or both not charging .... but it could work.

Or you could try a a manual 2 way switch to direct solar charge to one or the other as you wish.

Don't forget though that charging the wet crank battery with a smart charger will likely get it bubbling & gassing (smells like rotten eggs) when it reaches 100%. Wet batteries charged this way usually need a regular top up of fluid as a result. If your wet battery isn't capable of being topped up (no filler caps) it may vent, but you may also kill it prematurely if you don't monitor it to switch it off when it starts to gas, or preferably just before.

[Jonesy_sa]

Firstly, if you do throw the ctek out let me know when your bin day is and I'll come get it. ;-)

Secondly; I looked into this a while ago for a similar exercise. I had a large panel and wanted to attach a few chargers to trickle chatge my batteries when not in use.
I had to Google the solar charger type, the most common being PWM and MPPT. Googling your question with the above terms might be more useful. I haven't looked up what either of you're chargers are.

In short I was advised, and also read, that it wasn't possible as one of my chargers was a MPPT type. In layman's terms they track the output from the panel and adjust to provide optimum charging output. When two are connected they fight for the panel causing it to pull too low to be useable or create fluctuations in the panel output leading to inefficient charging.

Some people however were claiming they were doing it and it worked fine.

I'm definitely no expert but maybe that helps you on your search. Keep us updated!

I've bought some gear of solar4rvs.com.au. I know they sell a dedicated dual battery moot solar charger. They might be able to give some insight?

[Hodge]

Don't forget though that charging the wet crank battery with a smart charger will likely get it bubbling & gassing (smells like rotten eggs) when it reaches 100%. Wet batteries charged this way usually need a regular top up of fluid as a result. If your wet battery isn't capable of being topped up (no filler caps) it may vent, but you may also kill it prematurely if you don't monitor it to switch it off when it starts to gas, or preferably just before.

Thanks Cuppa. I wasn't aware of this.
I've been hooking up a Ctek 5.0 Amp wall charger which has the 8 stage charging thing on it, to my main battery once every 2 months for a proper charge. Have been doing this for just over 3 years now with the current main battery, and have never smelt or noticed anything unusual. Battery still very healthy.
I believe the Ctek DCDC charger in question has a very similar charging algorithm / profile.




Firstly, if you do throw the ctek out let me know when your bin day is and I'll come get it. ;-)

Secondly; I looked into this a while ago for a similar exercise. I had a large panel and wanted to attach a few chargers to trickle charge my batteries when not in use.
I had to Google the solar charger type, the most common being PWM and MPPT. Googling your question with the above terms might be more useful. I haven't looked up what either of you're chargers are.

In short I was advised, and also read, that it wasn't possible as one of my chargers was a MPPT type. In layman's terms they track the output from the panel and adjust to provide optimum charging output. When two are connected they fight for the panel causing it to pull too low to be useable or create fluctuations in the panel output leading to inefficient charging.

Some people however were claiming they were doing it and it worked fine.

I'm definitely no expert but maybe that helps you on your search. Keep us updated!

I've bought some gear of solar4rvs.com.au. I know they sell a dedicated dual battery moot solar charger. They might be able to give some insight?

Both of these chargers use MPPT on the solar side and are DCDC smart chargers. They regulate input and output, depending on certain settings, battery type etc... Each one of them worked like a charm on their own.
I just don't know how and if they will behave oddly if hooked up to the same panel.

PS. I'll let you know about the CTEK.
I shorted it out accidentally and it blew the internal "A" fuse. These units have 3 x 30amp blade type fuses inside. One for A (alternator / main battery), Solar and one for Output. They're soldered onto the circuitboard.

[the evil twin]

The panels will put out a fixed max current but whichever Controller "appears" as the lower input apparent resistance will get the most juice IE if the Ctek is lowest it will mean that the Intervolt won't charge up the Lithium first.

In basic terms you have dual loads in parallel to a single voltage source so whichever load is lower gets the higher current flow

Only way you will have any idea what will happen is to monitor the charging current from each reg.

[0-TJ-0]

Thanks Cuppa. I wasn't aware of this.
I've been hooking up a Ctek 5.0 Amp wall charger which has the 8 stage charging thing on it, to my main battery once every 2 months for a proper charge. Have been doing this for just over 3 years now with the current main battery, and have never smelt or noticed anything unusual. Battery still very healthy.
I believe the Ctek DCDC charger in question has a very similar charging algorithm / profile.





Both of these chargers use MPPT on the solar side and are DCDC smart chargers. They regulate input and output, depending on certain settings, battery type etc... Each one of them worked like a charm on their own.
I just don't know how and if they will behave oddly if hooked up to the same panel.

PS. I'll let you know about the CTEK.
I shorted it out accidentally and it blew the internal "A" fuse. These units have 3 x 30amp blade type fuses inside. One for A (alternator / main battery), Solar and one for Output. They're soldered onto the circuitboard.

No idea on the answer to your question, but have you looked at replacing the fuse in the ctek? Even the soldered ones usually aren't that difficult. Replaced the odd one over the years in different things.

[Hodge]

No idea on the answer to your question, but have you looked at replacing the fuse in the ctek? Even the soldered ones usually aren't that difficult. Replaced the odd one over the years in different things.

Yes mate.
Easy done mate, especially if you're good with soldering. Which I am not lol. But, a work-around is easier. The blades are soldered on/permanently mounted onto the circuit board. With a fuse-link between them. And then a blank "green" 30A cover slides over them. Without soldering, it's easy to use a in-line fuse with female crimps on each end. Job done. Photos show what I mean.

I only found this out AFTER my self and the place of purchase deemed to unit a write-off, and buying another unit and battery. But now the unit is un-usable to me as it doesn't support lithiums. Which is why I am toying around the idea with utilizing it's solar side for my main battery.
Supposedly, CTEK are really good with warranty side of things, even if it is opened up and slightly out of warranty period. But the turn-around time at the moment with covid is many many months.



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[Cuppa]

Thanks Cuppa. I wasn't aware of this.
I've been hooking up a Ctek 5.0 Amp wall charger which has the 8 stage charging thing on it, to my main battery once every 2 months for a proper charge. Have been doing this for just over 3 years now with the current main battery, and have never smelt or noticed anything unusual. Battery still very healthy.
I believe the Ctek DCDC charger in question has a very similar charging algorithm / profile.



No problem doing as you have, ie.once in a while & then disconnecting once battery is charged. Leaving it connected is a different matter. Although multi stage chargers drop into float mode when they determine a battery is full, they also drop back into boost/absorption mode as soon as any use of the battery drops the voltage. Eg. when starting the car. Many then repeat the full boost/absorption cycle which can run for several hours when all that is needed is a slight top up. This is less of an issue for batteries which have a gas recombination mechanism like AGM's, but it can see wet batteries dry out over time.

FWIW as I understand it the dropping back into full charge mode when only a tiny top up is needed is also the reason that chargers without a specific lithium charging profile are not recommended for lithium batteries. In that instance folk using 'drop in' replacement lithiums with their own built in BMS rely on the BMS to prevent the lithium from being overcharged. Problem though is that the only way the BMS can shed the excess current is by converting it to heat & with this heat enclosed inside the battery casing with nowhere to go, it can't be good. We all know electronics don't like excessive heat - so likely the BMS will kark it before the battery itself does, & a 'karked' BMS in one of those batteries essentially means a 'karked' battery. This is the reason that Redarc contradict the claim of many 'cheap lithium' sellers who gain sales by saying 'use our battery with your existing charger'. I suspect that when many of these cheap 'drop ins' begin failing prematurely we may see a move to drop in lithium batteries with built in heat extraction fans, and or/a move away from built in BMS to external BMS.

I include the Itech lithiums in this, so hope that your Intervolt charger has a lithium specific charging profile , preferably with settable voltage thresholds. I imagine it does as Intervolt stuff is pretty good. Have never yet owned a lithium (LifePo4) battery, but I believe most folk set up the charging to cut off at a set voltage which is a bit less than 100% full, & don't have the charge re-start until the read voltage is relatively low compared to that threshold for AGM's.

[Hodge]

I include the Itech lithiums in this, so hope that your Intervolt charger has a lithium specific charging profile , preferably with settable voltage thresholds. I imagine it does as Intervolt stuff is pretty good. Have never yet owned a lithium (LifePo4) battery, but I believe most folk set up the charging to cut off at a set voltage which is a bit less than 100% full, & don't have the charge re-start until the read voltage is relatively low compared to that threshold for AGM's.

Thanks for the info Cuppa.
Yes the intervolt unit version 2 has a Lithium profile. And like you mentioned, that profile according to the manual doesn't let the charge kick in (once fully charged), until the battery drops below... 2.4 or 2.6, i can't remember. But keeps the float volts up though.

[Cremulator]

Could you use a voltage sensing relay to detect when the AUX battery is at full charge and, instead of connecting the two batteries you use it to trigger a switching relay that then sends the solar to the main battery?

[Hodge]

The panels will put out a fixed max current but whichever Controller "appears" as the lower input apparent resistance will get the most juice IE if the Ctek is lowest it will mean that the Intervolt won't charge up the Lithium first.

In basic terms you have dual loads in parallel to a single voltage source so whichever load is lower gets the higher current flow

Only way you will have any idea what will happen is to monitor the charging current from each reg.

Thanks for this ET. It makes a heck of a lot of sense...Have everything wired up, and will test it out next bit of Melbourne sunshine.

[Hodge]

Could you use a voltage sensing relay to detect when the AUX battery is at full charge and, instead of connecting the two batteries you use it to trigger a switching relay that then sends the solar to the main battery?

Quiet possible mate. Haven't looked or thought about VSR's. I'll do some reading, but it would be challenging I reckon, since the Charger to the lithium will vary the volts depending on charge Stage / load, etc...

[Cremulator]

Yeh I'm not sure this would work, just a thought I had.
It's more about measuring the voltage of the AUX battery, rather than the charger voltage, and when the battery was at a certain voltage switch the solar input wire over to the other battery.

[Jonesy_sa]

An additional solar panel, even a small one, is probably the best bet if both chargers can't/shouldn't run of a single panel? I'm not sure what the minimum is you could get away with.

Out of curiosity what is the likelihood of a flat main battery? Reducing complexity and not adding another module has it merits in that it's one less thing to fail.

A friend has a supercheap dcdc charger fail and somehow cook the van battery and drained the auxiliary. He's glad he had the main battery connected via a VSR only as it meant he could still start the vehicle.

[Hodge]

Yeh I'm not sure this would work, just a thought I had.
It's more about measuring the voltage of the AUX battery, rather than the charger voltage, and when the battery was at a certain voltage switch the solar input wire over to the other battery.


This would work come to think of it... The lithium battery keeps solid volts for a long time... Up to 90% drain, and then takes a sudden dive. It usually sits on 13.2 forever. If i was to set a VSR to relay solar to the Lithium charger at, say 12.8V or something... It would be something to experiment and play around with.
But at the same token, it would now just get too messy and complex. Defeats the purpose of a simple setup lol.
The whole idea behind still using the Ctek, was it was still sitting in the back of the car wired up and I while I was wiring up the new intervolt unit, I thought hmmmm how can I possibly utilize it alongside the intervolt to maybe top up the main battery... But even that is getting above the "simple" setup, even without adding VSR's etc...
I'll give it a shot later in the week when we see some sun.

[Bidja]

The two batteries (ie: 2 separate loads/different chg profiles) are isolated from each other via their individual MPPT controller. IMO_Should work fine(no common loads be connected in parallel to both batteries same time).

Not sure if you have an inline fuse from module but would install a switch _dual battery rotary switch type between PV module and MPPT controllers to run controller options (either 1 or 2, 1+2).

https://www.ebay.com.au/itm/NARVA-BATTERY-MASTER-SWITCH-BOAT-MARINE-CARAVAN-DUAL-SYSTEM-ISOLATOR-61084BL/221305592980?epid=244110617&hash=item3386d75c94:g:sAkAAOSwkZhWTRsi

[Hodge]

Without starting a new topic,I'll ask this in my own solar thread ....
Hope some of you Solar gurus can shed some light on this.

I am now in a posession of the following panel.
It is brand new.
From my understanding , this is considered a 24v panel ? Due to having 72 cells and open circuit volts to 40v.

My intervolt dcdc V2 accepts 18-28v into its MPPT according to spec sheet.

I am assuming if solar volts going in are above 28,the intervolt won't accept it or fault ?
Therefore if this panel has good sun , it will always be in the upper range of its volts, and thus the intervolt won't be doing much at all a lot of time.
Just sussing out whether it is feasible utilising this before I comit .
I have not tested it yet.
Teach this solar nuffy sometbing.
http://www.nissanpatrol.com.au/forums/images/imported/2021/08/172.jpg

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[the evil twin]

Hmmm... DC/DC Chargers and Solar Controllers are different

A "true" MPPT buck converter Solar Controller will accept well above 50 Volts but the DC/DC Charger jobbies are different and therefore usually a lower input rating as they are usually running off 12 volt panels.

IMHO, your Intervolt 12V DC/DC Charger won't work of that Panel but a 12V true MPPT Solar Controller like this one will no problems
https://www.victronenergy.com/solar-charge-controllers/mppt7510

[Hodge]

Hmmm... DC/DC Chargers and Solar Controllers are different

A "true" MPPT buck converter Solar Controller will accept well above 50 Volts but the DC/DC Charger jobbies are different and therefore usually a lower input rating as they are usually running off 12 volt panels.

IMHO, your Intervolt 12V DC/DC Charger won't work of that Panel but a 12V true MPPT Solar Controller like this one will no problems
https://www.victronenergy.com/solar-charge-controllers/mppt7510Thanks heaps for the response mate.
I thought as much.
My 120w 12v panels work grouse with the intervolt feeding the itech.
The vehicle this panel came off had a Redarc BCDC unit of some description and the panel worked flawlessly with it...
I'm assuming the Redarc units can maybe handle the higher raw volts. Who knows.

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[the evil twin]

IIRC the Redarc BCDC have a higher input voltage spec of 30 something and will run the higher voltage panels.

The Intervolt might work but they are a good manuf that is known for high quality bits of kit so will depend on the over-voltage protection and sensing.
We aren't in lockdown in Perth so maybe give them a call (08) 9331 8555 or info@intervolt.com and ask them if that panel will drop enough output when in circuit with their kit (the OC voltage is exactly that so "in circuit" it will drop depending on circuit load)

FWIW I used to use Intervolt programmable VSR's a lot before I retired from that mundane thing they call "work".
They were an outstanding piece of gear.