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

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

    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 ?

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    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.
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    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.

    2006 4.2TDi ex-Telstra Remote area Camper. 425w roof mounted solar, 360Ah Aux batts, BCDC1240, Onboard hot & cold pressurised & filtered water, (25 litre hot water calorifier), ARB fridge, ARB freezer, Built in kitchen, heaps of easy access storage, 240v, 3 Genie exhaust + dynotune, 2 lift, Lovells GVM upgrade, second glovebox, ROH Blaktrak steel wheels, Bridgestone D697's (now Toyo RT's), Redarc gauges/pillarpod, Hema HX-1, Icom 450 CB, dual rear view cameras, Onboard 30amp Victron mains charger, second glovebox, dual seat conversion, Tyredog TPMS, Boss PX7 onboard air with 9 litre tank, 350w inverter, Steel bullbar, Harrop Eaton diff lock (front), Warn winch, Snorkel, Dual spares , 160 litre water tank, 180 litre fuel in two tanks (approx 1200km range) 2010 Tvan Tanami. (incl another 70 litre water tank) with matching wheels/tyres (& 3rd spare)
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    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?
    Last edited by Jonesy_sa; 4th October 2020 at 07:46 PM.

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    Quote Originally Posted by Cuppa View Post

    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.



    Quote Originally Posted by Jonesy_sa View Post
    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.
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    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.
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    Quote Originally Posted by Hodge View Post
    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.
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    Quote Originally Posted by 0-TJ-0 View Post
    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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    Quote Originally Posted by Hodge View Post
    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.

    2006 4.2TDi ex-Telstra Remote area Camper. 425w roof mounted solar, 360Ah Aux batts, BCDC1240, Onboard hot & cold pressurised & filtered water, (25 litre hot water calorifier), ARB fridge, ARB freezer, Built in kitchen, heaps of easy access storage, 240v, 3 Genie exhaust + dynotune, 2 lift, Lovells GVM upgrade, second glovebox, ROH Blaktrak steel wheels, Bridgestone D697's (now Toyo RT's), Redarc gauges/pillarpod, Hema HX-1, Icom 450 CB, dual rear view cameras, Onboard 30amp Victron mains charger, second glovebox, dual seat conversion, Tyredog TPMS, Boss PX7 onboard air with 9 litre tank, 350w inverter, Steel bullbar, Harrop Eaton diff lock (front), Warn winch, Snorkel, Dual spares , 160 litre water tank, 180 litre fuel in two tanks (approx 1200km range) 2010 Tvan Tanami. (incl another 70 litre water tank) with matching wheels/tyres (& 3rd spare)
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    Quote Originally Posted by Cuppa View Post
    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.
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