MPPT Charge Controller Solar and Auto Alternator hook up.

Psychowolff

Hi Everyone!

I'm rather new to the solar world and have a 'simple' question that I'm hoping some of you might be able to answer!

OK, I'm looking at using something like the MorningStar TS-60 MPPT controller in my RV to charge my coach batteries from 2 - 300W panels. (~600 Total) I currently have a pair of 170AHr 12V batteries that i would like to use in series and I might be getting another pair to make a 170AHr 48V system. I know the Controller will feed a 12/24/48V Battery bank but I would also like to use the RV's Alternator (~65A@14V) to charge the batteries while driving.

Is it possible (and is it normal?) to hook both the Solar AND the Alternator output to the Controller to charge a 24V battery bank (or 48V) and then also have the bank Discharge through the controller into a 12V distribution panel in the RV? Would I need the TS-60 controller or would the TS-30 be enough due to the higher voltage/Lower Amps?

Thanks!
Mike

bill von novak

Psychowolff said:

Is it possible (and is it normal?) to hook both the Solar AND the Alternator output to the Controller to charge a 24V battery bank (or 48V) and then also have the bank Discharge through the controller into a 12V distribution panel in the RV? Would I need the TS-60 controller or would the TS-30 be enough due to the higher voltage/Lower Amps?

Thanks!
Mike

Connect both to battery bank - yes, no problem
Discharge through controller - no, your battery bank will generally go right to the 12V distribution panel.  If you want a separate LVD (low voltage disconnect) then that's OK but the TS-60 won't do that for you.  The old Trace/Xantrex C40 does a good job there.  Generally that gets attached to everything EXCEPT the inverter, which always goes as directly as possible to the battery.

mike95490

So, using 600w of pv, to charge a 24v battery bank, you need only a 25A charge controller.   Small controllers may have low input voltage limits, but the TS-MPPT-60 is a bit of overkill (but it is a nice controller).  The vehicle alternator is 12V only for the vehicle starting battery, don't try to mod it to get 24V charging out of it.

bill von novak

bill von novak said:

Connect both to battery bank - yes, no problem
Discharge through controller - no, your battery bank will generally go right to the 12V distribution panel.  If you want a separate LVD (low voltage disconnect) then that's OK but the TS-60 won't do that for you.  The old Trace/Xantrex C40 does a good job there.  Generally that gets attached to everything EXCEPT the inverter, which always goes as directly as possible to the battery.

Note that the above only works for a 12V system, not a 24V.

Psychowolff

Mike - I am not modifying the RV charging system, it is designed to charge the Starting batteries and the Coach batteries. (through an isolator) I'd leave that stock but add Solar - feeding 12-15V in and the controller would up it to 24V. I was Hoping I could make a 24V bank to decrease the amps (and use a Smaller/Cheaper TS30 like you said) and also to put the batteries in series to be able to keep better control over their health; as in parallel one battery can suck the life out of the other before you really know it.

Bill - Darn, I thought the 'Load Control' was for feeding the Battery to the Dist Panel through the Controller. If I rewire the bank to 12V, would I have to go with the larger TS-60 MPPT Controller? The Panels will put out about 45-50A and the Alternator is about the same. (Not used together!) 

I appreciate your time and help guys. I'm familiar with Electronics, just haven't gotten into the Solar side of things too much yet...

littleharbor2

"I'd leave that stock but add Solar - feeding 12-15V in and the controller would up it to 24V."


MPPT controllers won't "UP" the voltage. They will take Higher voltage and step it down to the battery bank voltage.

vtmaps

Psychowolff said:

but add Solar - feeding 12-15V in and the controller would up it to 24V. I was Hoping I could make a 24V bank to decrease the amps (and use a Smaller/Cheaper TS30 like you said) and also to put the batteries in series

littleharbor2 said:

MPPT controllers won't "UP" the voltage. They will take Higher voltage and step it down to the battery bank voltage.

Most, but certainly not all, controllers work as littleharbor2 wrote.  What you (Psychowolff) want is a buck-boost controller.  Genasun makes several.  They are often used in golf carts where a 24 or 30 volt panel is used to charge a 36 volt battery.

--vtMaps

zoneblue

12V alternators are a bit of a unfortunately reality in many RVs. I do prefer 24V house systems, and heres a few ideas for getting around this, most of which ive written about recently in similar threads.

1. replace the vehicle with one with 24V start electrics, duh.
2. add a second 24v alternator
3. leave the house and start systems separate and do a 100% solar / shore power house system
4. adopt creative house charging, for instance, use a custom current limiting boost converter to feed power into a charge controller (tricky), or use a small inverter and AC charger (inefficient).

However if  it was me, and none of the first three options were workable, and the solar system was never going to be bigger then 1kW, then frankly sticking to 12V house bank is the least of all evils.

bill von novak

Psychowolff said:

Bill - Darn, I thought the 'Load Control' was for feeding the Battery to the Dist Panel through the Controller. If I rewire the bank to 12V, would I have to go with the larger TS-60 MPPT Controller? The Panels will put out about 45-50A and the Alternator is about the same. (Not used together!)

No.  In fact you could probably use a TS-30.  With 600 watts and a charge output of 14 volts you would see 42 amps in a perfect world; in the real world you will rarely see over 35.  (And the controller will prevent too much current from flowing in that case.)

For RV-sized loads, 12 volt systems aren't the end of the world.  There are a lot of benefits (no alternator changes, wide availability of loads.)  The one big negatives are the larger conductors and fuses needed, but that's not a huge hit for most installations, since RV's are (usually) physically small compared to houses.

Psychowolff

Thanks for all the Info guys, not everything I 'wanted' to hear but what is needed. I think I'll stick with the 12V system/Battery Bank. As Bill said, the RV isn't all that big and the Bank is actually only about 2' from the Dist Panel and Inverter so it should be just fine.

The Isolator on the Alternator is about 12 feet but I changed out the 10Ga wire for a 6Ga, Thats about the best I can do there. I Do appreciate the Help and I'm sure I'll be back with other questions! LOL