24v vehicle 12v aux batt, solar and battery isolation help (1 Viewer)

[p0875]

Hi all,
I've searched all over the forums so hopefully I didn't miss something that has already been answered. If so please point me to it.

I'm trying to setup an second battery for auxiliary power in my Troopy. I get all the basic ideas of isolating vehicle and aux battery, solar panels and charge controllers, etc. I've done lots of research and IF the vehicle was running 12v I'd be totally sold on the CTEK D250S DUAL taking care of everything. However, its a 24v truck and its really twisting my brain the best way to set it up.
Could someone create or point me toward a sketch or wiring diagram of how this should work including battery isolation and solar charge control, etc. that takes into account BOTH charging the aux battery when the vehicle is running and takes care of keeping the vehicle battery juiced via solar when its sitting for a long time.

Here's what I have:
The vehicle can't be changed - its 24v, so (2) 12v auto batteries in series, 24v alternator, etc.
I have (2) 12v solar panels that could be in series or parallel so either 12v or 24v
Aux battery is 12v
I also have a Perfect Power DCDC20 24v --> 12v that could be part of the system but doesn't have to be.

Much appreciation!!

 

[george_tlc]

24V vehicle electrics suck. I converted my 24V patrol to 12V (was lucky I had a donor 12V version) and it was the BEST thing I ever did to the patrol after years of dealing with 2 stupid batteries that have to be replaced in pairs, can't be drained down in a mismatch configuration, can't help you jump start yourself, etc etc...

Anyhow, you are stuck with what you have so:

It would be best to only ever run the 2 series batteries as a 'single' 24V battery. Only ever charged via the alternator or only ever charged with a 24V output solar setup. Otherwise you risk a battery mismatch (state of charge) and then you are in trouble.

Treat the aux 12V battery as a totally separate unit. It charges via 12V solar only or via a 24V-12V charger (via the alternator system) while moving.

Do NOT be tempted to put the aux in parallel with one of the 24V series batteries to charge etc. This will cause a mismatch of your 24V pack.

24V vehicle electrics suck

cheers,
george.

 

[p0875]

Thanks George! I totally agree, 24v vehicle sucks for all the reasons you stated. Don't even get me started on finding light bulbs for instrument panel...

I get treating the starter as 1 - 24v battery.

I think 24v solar or 24v alternator to charge vehicle battery is way to go. Where I'm stuck is how to share the same inputs with the aux battery via dc-dc 12v charger. Any circuit diagrams out there like this I can riff off of?

 

[YvesNL]

Here is a simple schematic:

There are two ways to charge the battery in this setup. Through solar, and through the DC-DC converter (from vehicle battery).

The solar power never shuts off (only when the battery is full the charge controller switches the solar power off).
But what I mean to say is that solar will always be charging your auxiliary battery if you have sunlight, an incredibly bright streetlight, a lot of flashlights, I think you'll get the idea.

When you switch your ignition on and go for a drive the alternator will charge the 24v vehicle battery (the two 12v vehicle batteries in series).
Also, the relay to your DC-DC converter will be closed. This means that while driving you will also be charging the auxiliary battery through the alternator and DC-DC converter.

When you turn your ignition off the relay opens and you can't drain your vehicle (starting) battery by powering your fridge or other auxiliaries.

Make sure you get a beefy 24v relay, a solar charge controller and some chunky wires.

 

[77cruiser77]

This is something I've been workin on for many years. Started with my HJ61, also 24v. Began collecting pieces as I had other projects, lost the 61 and got a 77, also 24v. If I did it all right now in a quick swoop I'd use different components but these are the ones I have now and will put them to use.

24v-12v converter
VCS-2AL (30A) charge controller
CTEK D250S Dual (not purchased yet)

My main requirements are this is so simple and automatic anyone can drive it without ruining the system and that my starting batteries are left alone and completely isolated. After my vehicle is started and my voltage gets to a certain amount it will switch to charging the house battery. Once house battery is charged power to it is switched off. For extended days without the engine on I will rely on solar to keep my house battery up and hopefully my main starting batteries too.

 

[77cruiser77]

Current wiring diagram I've come up with

 

[77cruiser77]

VCS-2AL 10-60V, 1A Voltage Controlled Switch, Active Low, Enclosed

This is the controller I am using. Converters and whatnot are more or less the same. This controller on the other hand to a certain degree dictates my schematic. Hope it helps.

 

[george_tlc]

Had a quick look at the controller link you provided. It's a 1A output (small signal relay), i.e. the C/NC/etc is only a tiny relay. To switch 30A you need to add a high power relay - I don't see that in your drawing above.

I also don't see where the GND connection is on your solar side wiring, it only goes from the panel to the CTEK and you don't show where it then connects to your battery side wiring.

The Gauge? needs to only be 18, it is only sensing voltage. In fact all wiring connections to the controller can be 18g, it's only 1A max (for it's relay) and the rest even less.

cheers,
george.

 

[77cruiser77]

Thanks George,

VCS-2AL, Voltage Controlled Switch, Enclosure, 10-60V, 30A, Active Low,

Mine is a 30A model so good catch.

As for the solar controller I found this odd but only followed the manual I got from the internet

I've put the electrical on hold since last year so my memory is a tad foggy. Trying to remember the reason for the diode. I remember it was a clever idea. Let me know if there's anymore holes you see and I'll have to re read the CTEK manual

 

[george_tlc]

Looked quickly at the CTEK. The GND/IN- terminal is COMMON to both the solar panel, the alternator (or in your case the 24/12V converter) AND the Aux battery. So add a black line on your drawing from the CTEK- to the Aux battery-. i.e. ALL black lines in your drawing above are COMMON (connected).

Not sure on your diode...

cheers,
george.

 

[77cruiser77]

Excellent! So aside from adding another ground should be good.

The diode was an idea (hence light pencil) to try and figure out how to charge the starting batteries from the solar panel. Still trying to figure that part out

 

[77cruiser77]

Also, should I have a ground to the body or frame from the neg battery terminal?

 

[george_tlc]

Yep, GOOD ground connections between batteries, dtek and 24/12V is essential. Remember that the same current that flows through the positive leads also has to flow through the negative leads...

To charge the main batteries from solar you would need a separate charge controller from the panel to the 24V (28.8V max) series battery stack. Just as draining one of the 12V batteries (of the 24V series pack) is a bad idea, so is charging only one of the 12V batteries. Mismatched charge/discharge of 12V batteries in a 24V stack is bad...

cheers,
george.

 

[77cruiser77]

Piss. I figured. I'll leave topping up the main starting for later then.

For ground I planned on having a plate on the body for various grounds to attach and have that plate further grounded to the frame.

Thanks for the load of confidence George! I was concerned installing but I feel I can get it going within the next month

 

[The Dude]

I love my 24V systems. We have them on lots of our machinery and in my Cruisers. I also have a third aux battery on the HJ61

I only have a few things to add:

1) get your starter and alternator wire in GREAT shape. I added a wire directly from the 24V alt to the batteries
2) the only thing attached to your batteries - terminal should be a wire to the frame and the body using the he shortest possible wire.
3) bond your engine to the frame
4) if you are going to use an equalizer (on the 24V system) wire it so that it only runs when the ignition is on
5) voltage drop is a HUGE concern on a complex system. It's all about wire size AND length of run. Pay attention to both.