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campfire57 avatar image
campfire57 asked

Solar controller directly connected to batteries.

I just bought the mppt 100/30 with Bluetooth. I currently have 5 lithium batteries in parallel 12v. Also I have four 90 watt solar panels, looking at adding one more 90 watt panel giving me 450 watts total.

My question is can I connect the solar controller directly to the batteries. Positive post to solar controller and negative post to solar controller. I do have a 40 amp inline fuse attached on the positive wire right before the battery positive post. Then connect solar wires straight to solar PV connection on solar controller. Will the Bluetooth work using the app connected this way.

MPPT Controllers
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6 Answers
ingo21 avatar image
ingo21 answered ·

i would recommend for you to download and read the manual for your charger.

how do you plan to connect your solar panels? in series or parallel?

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southsideph avatar image
southsideph answered ·

Adding a another panel would put you just over the max input wattage of 440W at 12v. As for your fuse question, the fuse is to protect the wiring - what size batteries and the maximum discharge current of the batteries? Can your cabling sustain that discharge current at 12v in a short circuit scenario? so it is advisable to put a protection device between the MPPT and the battery to protect the wiring. So many lorry fires are caused by overloading the cabling.


I use SmartSolar MPPT 100/30 in camper van and a 40A 12-48v MCB (Minatare Circuit Breaker) available online for a reasonable price.

Hope this helps

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kevgermany avatar image kevgermany ♦♦ commented ·
Not sure why you say this is over the max input wattage. It's normal to put more panels on to provide good charging at low light levels. What matters is input voltage and short circuit current. We don't have this information. It appears the panels are wired in parallel and that a fifth would also be in parallel, but...

At some point extra panels won't be worthwhile due to controller capacity, but no damage occurs, it simply limits output.


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mindaugas avatar image
mindaugas answered ·

Yes you can. Solar panels will have aprox. 80-90 Voc. No fuse needed as quite low current with such power


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campfire57 answered ·

There’s something wrong with the original wires going through the airstream wall’s. So I’m just going to run new wire’s. Thanks for everyone help.

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campfire57 answered ·

I have 4 solar panels going to a box on top the camper with 3 solar connections. I connected two panels with a Y connection. So one of the box connections has two panels going in and the other panels have there own connections.

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campfire57 answered ·

Thanks, I just went on top the camper and ran a separate wire from each solar panel to the solar controller and it works. (one solar panel at a time). Do you think I may have a problem in the junction box on top the camper?

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