Automatic charge controller switching

[max2474]

Hi. I am looking to do a van conversion with solar. Due to high energy demands, I have separated my electrical equipment into two groups - what I consider important (such as lighting and refrigeration) and less important (such as a television). Because of this, I would like to have a separate bank of batteries for both groups.

All I am wanting is a setup where the charge controller will charge the main bank first, then when it is full, to switch to the second bank (similar to how a home system would automatically switch to sending to the grid). This way, I get the luxuries only when the important equipment is taken care of.

All the research I have done so far offer either
1. Setups (normally with diodes) where the charge is sent to the bank with the lowest capacity and switching back and forth, charging both equally.
or
2. A manual switch where you select bank 1, 2 or both.

I cannot seem to find any setup to achieve what I am wanting. I am sure it is just me missing it, but google doesn't seem to like my searches anymore!

As you can probably tell, I am pretty new to this - I am really hoping the answer is not too complicated. I really appreciate any advise / pointers you can give.

Many thanks,
Mark

[Sunking]

This is super easy to answer. You left out an option

3. Build two systems.

In any event you are going to want to use an Electronic Battery Isolator so you can use your engine alternator to do most of the charging and CYA for cloudy days. They are inexpensive starting @ $30 up to $100. They come in 2, 3, and 4 ports so you can have 1, 2, or even 3 banks of House Batteries. Isolators do not rob Peter to pay Paul. They Isolated each battery from each other so that cannot happen. Batteries get their power from the alternator.

Your engine alternator can generate more energy in 1 hour than a roof full of panels can generate in a day or two. If you drive every two or three days while out in the Van RV, you really do not have a lot of need for panels. Any battery setup in an RV needs to be sized for at least 3 days of power, which give you at least 2 days usable power.

The only other real way was your option 2 using a transfer switch which is a piss poor way to do this. FWIW the idea of using one panel system to charge two isolated batteries is just a really bad idea and will not work like you think. It takes everything the panels can generate to just keep up and replace what is used in one battery bank. Instead of one bank of dead batteries, you will end up with two dead banks, and without an Isolator or Generator to recharge quickly, you are SOL and dark.


Bottom line is you do not want two banks, you want one properly sized bank with an alternate source of power like an Isolator and/or generator. Sounds like you have a Class B RV, or a converted van? The roof is small and you will be lucky just to have enough room for panel power to charge one set of batteries.


Good luck.

[littleharbor]

I can't tell you how many times I wanted to suggest this option, #3. Especially when the op is asking about running 12 volt loads off a 24 or 48 volt system.
My place in Baja has the system in my sig. Originally, before I bought it and installed the new system there was a small 2 panel 12 volt system with a small inverter. This was installed in the garage, approx. 85 feet via underground conduit from the house. The 120 Vac didn't concern me as much as the 12 volt running through 10 gauge wire. The voltage at the house water pump would drop to just over 9 volts when the water was turned on . It wasn't a big deal to set up a small 12 volt system on the house for the water pump, VHS radio and stereo. I did the same for the Garage which has a separate bathroom with water pump and another VHS radio. I realize many folks on a budget might find this cost prohibitive but it's something you might take into consideration when budget allows.

Max2474, My apologies for the hijacking of your thread.

[Sunking]

Littleharbor that is possible on a home where space is not limited like a RV. Splitting panels among two sets of batteries is just asking for two dead sets of batteries.

[littleharbor]

Littleharbor that is possible on a home where space is not limited like a RV. Splitting panels among two sets of batteries is just asking for two dead sets of batteries.

Yep, apples and oranges. I did consider my comment a hijacking. Plus the RV in question is a van so very limited space.

[max2474]

Thank you both for your input - even with the hijacking littleharbor

To be a little more specific, I am looking to purchase the van over the next few months specifically for this conversion I want to plan everything out first (as much as i can anyway) The van I am looking at is a 2006 Iveco Daily XLWB
(http://www.ebay.co.uk/itm/2006-Iveco...o/112408378345 if you are able to view it - I am in the UK lol)

The van is (approx) 2 meters wide with a 4 1/2 meter length flat roof - I am looking to put 4 x 190 watt panels on. Not cheap, I know, but I have estimated my power requirements to be about 300 amp hours per day needing 4+ 180AH batteries.

I will look at having 2 lots of 2 panels though I am disappointed that it isn't as simple as i expected.

[littleharbor]

Are you choosing the 190 watt panels because of their size? I'm going to guess they are 72 cell monocrystalline and approx. 32" x 62". 60 cell, 265ish watt, panels are about 39" x 65" and are typically the least expensive per watt. Not sure how that works in the UK.

[max2474]

This is the data sheet I am using for the panels:

https://www.victronenergy.com/upload/documents/Datasheet-BlueSolar-Monocrystalline-Panels-EN.pdf

I can fit 4 of the 190 watt panels on the van, but only 2 of the 300 watt ones...
the 190s are 1580mm x 808mm (62" x 32")
the 300s are 1956mm x 992mm (77" x 39")

NB: The van roof is ~ 1800mm wide (70").

[littleharbor]

The 300's are 72 cell panels with 6" cells That's why I suggested 60 cell 250 - 285 watt size panels. They are just a little taller and wider than your 190's. They could fit width wise across your van. Are 60 cell grid tie type panels available in your area?

[max2474]

I have not come across the 60 cell grid type yet, but I will keep an eye out for them - I am looking to get the most I can for the space I have

I did come across this today btw :

http://www.sunstore.co.uk/EP-Solar-Duo-Battery-Solar-Charge-Controller-12-24v-20A.html

Seems to offer something similar to what I was after - albeit PWM and not MPPT.. Any thoughts?

[littleharbor]

Morningstar makes a dual battery charge controller as well. You will need to use a "true" MPPT controller unless you use 12v volt panels on a 12 volt system. Don't be fooled by any inexpensive so called MPPT controllers

[Sunking]

The van is (approx) 2 meters wide with a 4 1/2 meter length flat roof - I am looking to put 4 x 190 watt panels on. Not cheap, I know, but I have estimated my power requirements to be about 300 amp hours per day needing 4+ 180AH batteries..

So how do you plan to charge the batteries?

Reason I ask there is no way possible to do that with 760 watts of solar panels. I have to assume you are talking about operating on a 12 volt battery. 12 volts x 300 Amp Hours = 3600 Watt Hours aka 3.6 Kwh. On a van with panels pointing straight up on a UK summer day you will be lucky to generate 1/3 that amount of power.