Multiple chargers?

[Les May]

• Multiple charge sources?
• Description
• Hi, first of all, I'm a complete newbie, so apologies if my question is stupid.
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• In essence, my question is - can I connect several charge sources simultaneously to a battery.
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• On the face of it, its a stupid question but in reality I have a cheap solar charger connected to my tractor battery so that I am never left with a flat battery, but when I start the engine the battery is getting a charge from both the alternator and the solar charger, hence two sources in parallel. With a rudimentary lead acid set up, this probably isn't a problem but when applying the same practice to my motorhome it starts to get expensive and fire is my worst fear.
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• Now the real question.
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• I am considering upgrading the entire power system in my American Motorhome. It has a solar charge system already but it uses Lead acid batteries and is quite basic. My plan is to base a new system around the Renology 12V 300Ah Deep Cycle Lithium Iron Phosphate Battery. SKU: RBT12300LFPSH-UK. Most likely 2 batteries but possibly 3.
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• I plan to use the DCC50S 12V 50A DC-DC On-Board Battery Charger with MPPT(New Version) SKU: RBC50D1S-UK so that I can charge from the vehicle alternator when on the move. I would like to also incorporate the 3000W 12V Pure Sine Wave Inverter Charger w/ LCD SKU: R-INVT-PCL1-30123S-UK into the system as well. Which would provide AC when required and also a handy Lion compatible charge capability when connected to a shore supply.
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• I have 2 queries.
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• A) the DC-DC charger has a max solar charge current of 25A. Where as some the other solar charge controllers have a much higher rating i.e. the Rover 100 Amp MPPT Solar Charge Controller SKU: RNG-CTRL-RVR100-BT-UK1. 100A is possibly overkill but 25A might be too low, thus can I connect two chargers i.e. the DC-DC to charge from the alternator and a separate PV charge controller simultaneously (i.e. in parallel to the same battery). Potentially both chargers could operate at the same time i.e. engine running thus charging from the alternator via the DC-DC and the separate PV could be producing a charge at the same time. Would the two chargers interfere with each other?
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• B) in very much the same way, would connecting the Inverter / charger to a shore supply, thus causing it to also produce a charge cause a problem? In this instance I could potentially have 3 separate charge sources connected to the same battery. i.e. engine running thus charging from the alternator via the DC-DC plus the separate PV producing a charge at the same time and also the inverter / charger producing a charge because it's connected to the shore supply.
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• Assuming the above is possible, could any provide a schematic of the required components to create a system that can charge the batteries in all of the 3 situations above i.e. alternator / PV / ac charger (in-built in Inverter) that would be fabulous

Regards Les

 

[Les May]

Hey guys, I found the solution on this forum by doing some hunting. In short, yes you can connect as many MPPT chargers as you want to the same battery as long as you do not exceed the maximum charge current for your battery.

Watch this video

 

[Dave in AZ]

You are jumping way ahead of yourself, picking the exact equipment you want to install, before you even have a design or plan at all! The LAST thing you do is pick the parts!

None of your pictures posted, so I have no idea what info they contain...

The FIRST thing you do is figure out the loads, how much electricity will you use and need?
NEXT you figure out how long you must power all that without being able to charge, solar or shore power, to figure your battery needs.
NEXT you figure your charging needs--how much solar can you fit on roof, how much WILL you put there? That drives your solar charge controller mppt requirements, not the fact Renogy has a dcdc solar combo unit...like everyone else...
NEXT you figure you AC power needs, how much 120v? That drives your inverter choice, and that MAY drive your 120v charger choice if you get an inverter charger combo.
NEXT you look at what your alternator is and what load you can reasonably put on it and still stay below its 60% max so you don't burn it out, before deciding on what dcdc charger to use.

If you already have all this in a motorhome, and are committed to some parts, that reduces your design options.

 

[RV8R]

Hey guys, I found the solution on this forum by doing some hunting. In short, yes you can connect as many MPPT chargers as you want to the same battery as long as you do not exceed the maximum charge current for your battery.

Watch this video

Thanks @Les May as I had not watched that video & I learned somethings that helped “the penny drop” for me.

Take Aways;

Multiple chargers ( or a single ) interrogate a battery for internal Resistance not Voltage & then drop to “Float” Voltage once that Resistance is reached.

Multiple chargers do not have to communicate with each other & the main function of networking them is for FLA Equalization stage ( once every 28 days ), but a DIY could just have Equalization function from one charger & not have all chargers “talking” to each other.

Multiple ( or single ) chargers will produce power based upon “Load” & when the battery resistance goes up the “load” goes down ,,, thus think about the battery as a load n the system along with other loads.

Until just now, I have struggled with the concept of chargers reading battery voltage & to find out that they detect resistance is a real perspective change ,,, thanks Will !!


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@Les May to get to your questions;

I agree with @Dave in AZ post above, in that if you could draw out your proposed “schematics” & post a picture of them here we could see your design rather than read it. Much easier to understand & you will attract more members looking over your schematics & provide opinions.

Best not to buy anything, until you vet your design. I think anyone who has been in the hobby long enough has equipment they don’t use or never installed , & we all like to save others from our errors.


If you are looking for a dual DC2DC ( alternator & solar ) charger, the Kisae 1250 or 12100 is a decent dual charger.

DMT1250 – Kisae Technology Inc

I installed a 1250 in my van & so far ( 7 months ), I love it. Very user programable & can limit amps to save the alternator / battery if needed.

 

[0truck0]

Can you fill a pool with multiple water hoses?

Also, please read a few forum post using the SEARCH function as all this is discussed already- before you make a new thread.

You can fill a pool with multiple hoses. This answers all of your questions above.

Chargers with an equal voltage when connected in a parallel configuration increase the number of amps without affecting the voltage.

For instance, five 12V 50 Amps chargers bring a total of 12V 250 Amps.

With your 300ah batt you can charge at 300 amps, 150 is usually recommended as the max. Just add up the max outputs of chargers. Your DC-Dc prob never get to 25 depending how is wired, but add anyway. 25 plus 100 = 125 and that is below your 150 half number, and unlikely either charger outputs its max unless one is a plug-in device (not solar panel driven).

The schematic is..... wire them all in as if they were the only charger wired in. This makes 3 sets of wires for 3 chargers. Keep your pos and neg cables from charger to battery the same length for individual chargers, but does not matter from one charger to the next if lengths are different.
For anyone using a shunt, then the shunt becomes the neg battery post, so you wire to the shunt on the neg side (or a battery bar that goes to the shunt).

You can put a on/off switch on any or all of the positive wires from the charger to turn them on or off as needed/desired if you think you need less charge amps.

Lithium batts do not need that float charge when stored, you can stop all charging on them for a month or two, and just put charge on them when needed. this is another topic u can search out.