#147004  by skood
 Fri Dec 07, 2018 7:33 am
Hi All

Firstly, thanks for all the fantastic information posted here - it's a fabulous resource (if a little tricky to search). Although this is my first post I've been an avid reader and absorber of your collective knowledge.

A friend an I are rebuilding two 1970s caravans (Anglo Imps - 10 feet 6 inchs), and have had a lot of fun doing so over the past 3 months. I'm getting into the areas where my knowledge is .... almost nil.

We have 150Ah 12V AGM batteries and 150W solar panels. The max load in the caravan 13.75A if everything is switched on at once.
I was planning on using the Smartsolar 75/15 controller
http://www.aeppacific.co.nz/marine-part ... 015-10020/

and I have 3 questions that I hope someone knowledgeable out there might help with so I can sleep again:

1. If I wanted to install a VSR in the tow vehicle to charge the caravan house battery, how would I wire it? I seems both the VSR and the solar controller would confuse each other as to the state of charge in the house battery.

2. Does it make any difference if the controller is adjacent to the battery ( under a seat) or closer to the fuse/switch panel (in an overhead cupboard)?

3. I asked these same questions of AEP Pacific about their product but have had no response. Zero. Nothing. Are they a company that's worth dealing with or should I buy elsewhere?

Thank you for any advice and help.

Stephen ( Queenstown)
 #147007  by scubadoo
 Fri Dec 07, 2018 8:49 am
Welcome to the Forum.

"2. Does it make any difference if the controller is adjacent to the battery ( under a seat) or closer to the fuse/swith panel (in an overhead cupboard)?"
Yes. The aim is to reduce power losses for maximum efficiencies. Mount the controller as close as practicable to the battery pack and do not skimp on wiring sizes.

"3. I asked these same questions of AEP Pacific about thier product but have had no response. Zero. Nothing. Are they a company that's worth dealing with or should I buy elsewhere?"

I have purchased more than a few :TU products from them with absolutely zero issues.
5 year Victron guarantees are worthwhile.
Just call them and speak to their resident technical expert (and I mean expert) about any of the products they sell. I was even connected to Holland for an extra tricky query.
Don't expect help for the myriad of methods for wiring up a caravan. I would not see that as their role.
 #147008  by mattn
 Fri Dec 07, 2018 9:39 am
When it comes to batteries and charging systems too many people over think it, over complicate it and make life difficult for those who just want to get the job done. Ultimately the difference between good enough and perfect is the time it takes to get the very last 2-5% of charge into the battery.

Installing a VSR, wire the car charging directly to the battery. It won't make any practical difference to the solar controller. I suggest you look at a Dc-Dc charger - Supercheap have one that regularly comes on special $120 for 20AMPs that cheap and cheerful (I use one of these) , Redac just released a 40AMPmodel which would be better, but is a lot more expensive at $670. If you use a DC-DC charger, you will not need a VSR.

As far as solar controller position - as per the above answer - closer to the batteries the better.
 #147015  by Neddy
 Fri Dec 07, 2018 3:43 pm
Stephen, you can mount your solar controller anywhere you like. The further away it is from the battery, the heavier the connection cable required, that's all.
For example, if they are 1 meter apart, #14 gauge cable will give a very acceptable transmission loss of 1.3%.
With the same controller and the same battery placed 4 meters apart, #8 gauge cable is indicated, giving a transmission loss of......... 1.3%

Once you position your controller, all you need to do is measure the cable run needed and use this utility to calculate the wire gauge necessary to give an acceptably low loss. 1% is excellent, 2% is good and 3% is OK.
https://www.omnicalculator.com/physics/voltage-drop

Matts suggestion of a DC/DC controller would give better results than the VSR you are proposing, for very little extra expense.

The cheapest option would be to fit a manual switch connecting the Start and House batteries in parallel. You would turn this on if :-
(1) You wanted to charge your House battery when motoring.
(2) You wanted to Solar charge your Starter battery.
(3) Your Starter battery ever needed assistance cranking the engine.

Neville.

https://www.omnicalculator.com/physics/voltage-drop
 #147018  by Andrew and Debbie
 Fri Dec 07, 2018 4:54 pm
Neville, Some of your suggestions such as using the house battery to assist the cranking battery to start the engine would need some seriously big cable given the length needed to run from the tow vehicle battery back to the caravan house battery, as well as a high capacity Andersen plug or similar on the drawbar.

Cheers,
Andrew
 #147038  by skood
 Sat Dec 08, 2018 8:44 am
Wow! Great Forum! It is so reassuring to be able to connect with a community of people who actually understand this subject and are prepared to help out the inexperienced like me... thanks guys.

scubadoo: Great to know AEP Pacific are good to deal with... I like to support NZ busniess where it makes sense to. Good news!

mattn: I wasnt sure what a DC-DC charger was before, but I think I am now. For anyone else trying to get their head around this , I found this artilce helpful: https://www.caravanworld.com.au/feature ... -explained
When Looking at these things, I looked up the Supercheap Auto site and saw they sell a Matson brand 20A DC-DC charger with a solar input. It states elsewhere it is MPPT. If it used this then I don't need a separate solar controller, but I have next to no info onthe state of my battery. Is there a simple (you might like to insert 'inexpensive' here) way to monitor the battery and panel performance. One thing I like about the Smartsolar controller is that it uses built in Bluetooth to link to my phone so I can see what is going on in any moment and get a month's worth of data without filling the wall of our little space with distracting lcd screens. I guess I can use a DCDC charger without built in solar input, and use the Smartsolar between the panel and battery too, right? Anyone have experience?

Neville: thanks for the link to cable sizing calculator... I've used it from other posts you have made in the past here too. Your input to this forum is clearly invaluable. I've learnt a lot from your posts to others already. I really like your suggestion of linking the system, giving the posibility of aiding the start battery if required. Andrew (Thanks Andrew for your input too) Mentioned the large cable size required to set up as you suggested. I'm not sure how to work out the cable size here as I don't know how many amps the car would pull when starting. Waaaaaaa! There's so much I don't know!

Thanks in advance
Stephen
 #147042  by mattn
 Sat Dec 08, 2018 12:56 pm
Hard to know how much detail to go into when answering questions. I really do appreciate that you are taking the time to follow up on the bits you do not understand, but please do ask questions if you need. I try to have my answers give key information to lead you down another voyage of discovery, I find when people do some homework they learn, and get to where they want to be much quicker than when they have everything handed to them on a plate.

A better way than using the solar controller to see whats going on is a Battery Monitor. Have a look at This thread. It measures the current going into and out of the batteries - regardless of the source - and keeps a running total. Most solar controllers only measure instantaneous current so are far less useful. You can get Bluetooth battery monitors.

The amps for starting are in the multiple hundreds, its not something you can realistically do from a caravan. If I had a flat car battery, I would connect the house up to it for a while and let the car starter battery get some charge, or I would remove the house battery and use short jumper cables.

That Matson looks like a good unit, although CTek are a well known reputable brand name product for a similar price.
 #147046  by Neddy
 Sat Dec 08, 2018 6:57 pm
Stephen, if you install a DVSR, the House battery will at times be assisting the Starter battery whether you want it to or not. With our Mercedes Sprinter RV, the DVSR has the House and Starter batteries connected in parallel pretty much all day. When starting the engine, the House battery shows a discharge of 60 amps. This is roughly half the total starter load with the rest coming from the Starter battery. You do not need fat cables, but the thinner they are, the less current the House battery will contribute on startup. A fairly trivial issue for you.

Without a battery monitor, you will have precious little idea of what is going on, so I suggest that you fit one first off, before most anything else.

If you are trying to keep to a budget, I would suggest that initially you just fit a simple Starter/House battery parallel switch. When the engine is running, you will be able to see exactly what charge voltage and current your car is supplying. Depending on the vehicle electrics, this can be surprisingly effective. Our RV motor supplies in excess of 40 amps to the House battery on occasion. If this simple setup proves to be adequate, you will not really need a VSR at all, unless you want the switching to be fully automatic. If the switch idea does not give you sufficient additional charging power, you may want to go to a DC/DC charger but often there is no need for this (as in my case).

Victron gear is very good, but if you are on a tight budget, there are many cheaper solar controller alternatives available.

Neville.
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