24V to 12V split charger?

[Arfur's World]

Thanks all, seems like the Sterling is the way to go, which seems fitting as my donor caravan is a Sterling Elite Amber ... it'll look like original fit

So the next query is, will that charge parallel batteries ok as well? So that I can have a longer supply?

 

[docka]

The Sterling Battery to Battery Charger/Dropper 24-12-30 connects your 24v starter batts to your 12v leisure batts and while driving or engine running will charge both battery banks.
Ideally this would be complemented by a solar setup (panels and charge controller) for periods when the van is parked up ie engine not running.
http://www.sterling-power.com/products-battbatt.htm

 

[ianc]

So the next query is, will that charge parallel batteries ok as well? So that I can have a longer supply?

If you're wondering if it will charge more than one 12v battery wired in parallel - Then yes albeit at a slower rate.

Ian

 

[Arfur's World]

Having got a bit more into the thought processes, and realising I've got 6 days following the Tour de France when I will be off-grid, my brain is ticking over the battery config that I should go for. Thinking something like 2 x 260Ah, or should I go for more? Any thoughts? At this point in time, it is unlikely that I'll be adding solar for this summer, so it will be purely charged from the engine and when on-site.

 

[andylod]

Arfur
It does depend on what you are running. I run a 12 volt compressor fridge, Led lighting, 12volt TV and radio, overnight phone charging and occasional heating (gas hot air) no 240v appliances that require the inverter..... we have 2 x 110 ah and easily last 3 or 4 days without any engine starting .... we have done 6 days but then flattened the batteries which is not a good thing.... We have just done 3 weeks "off grid" with stops of 2 or 3 days then 4 or 5 hrs of travelling between and no solar....
I think its probably a balance of costs. If you have enough physical room and weight allowance to allow for bigger batteries in the future if you feel you need them, then 200-300 ah is probably enough for now, then add another battery in the future if you need one.
Off grid with no engine starting for 6 days would probably need your 500 ah so as not to drain too much.

Hope this helps

Andy

 

[Anton2k3]

I recommend checking out the trojan T-105 or T-605, 6v batteries, 220ah. 4 of those would be more than adequate for most situations. We currently have the T-605's, but will go for the T-105's when ours need replacing. We run an inverter, 27" TV, compressor fridge etc. and can last 3 days or so before i get twitchy. Solar is next for us.
Highly recommend the 24-12v charger from sterling.

 

[Arfur's World]

Why 6V batteries Anton? Does half the voltage give twice the Ah or something? How would you wire 4 together to end up with large Ah but still at 12V? Not trying to catch anyone out here, I genuinely have no idea

My fridge is gas, so that will reduce the electricity need, but probably made up for by the microwave... And as I'm robbing all of the electrics from the caravan, I haven't yet worked out how I'll blend it all with the charger, as I have a charger already with the caravan, it's just if that is suitable for use from the 24V or not.

I need to get the walls in this weekend, to some reasonable degree, then I can lay out the wiring loom and start working it all out :friday:

 

[andylod]

I guess your caravan charger will be 240v-12v .... this doesn't affect your vehicle 24volt circuits in any way. The sterling 24v-12v charger takes power from the vehicles 24v circuit to charge the 12v habitation battery, but this link only goes one way. So you will have a 12v habitation circuit with a 240v-12v charger for when you are on hook up and a 24v-12v charger connected to the vehicle battery for when the vehicle engine is running.
Andy

 

[Arfur's World]

That makes sense so I'd need the Sterling as well as the existing unit. One minor fly in that is that I think the caravan can charge from the 12V vehicle whilst being towed, so I guess I need to work out which bit does that, and replace it with the Sterling ... my brain hurts!

Also, I've looked up the wiring stuff I asked about earlier, and can see the whole series & parallel thing, but what advantages does having 4 x 6V providing 450Ah @12V give, rather than having 2 x 12V providing (for example) 480Ah? Is it resilience, lower wear and tear or something else?

 

[Anton2k3]

Hi,

You wire two 6v batteries in series which makes that bank 12v 220ah. You do the same with the other two, then wire the two banks in parallel to make the system 12v 440ah. The reason i recommend this method is two fold. 1, i have done this so i'm biased! 2. They are traction batteries which cope very well with large loads and deep discharging. Standard 'leisure' batteries are ok i guess, but a 12v 220ah variant will be quite large, heavy and generally cumbersome, and probably won't last as long. YOu can get 4 T-105's for around 400 quid delivered to your door these days.

 

[Anton2k3]

Just hook the sterling up to the new battery bank, don't worry about existing charger 12v thing, its redundant.

 

[Anton2k3]

One more thing....seriously consider changing the fridge for a compressor 12v type. I know its ideal using the caravan kit, but having a gas fridge will use ALOT of gas if your off grid, and they work terribly if the van is even a bit unlevel. So if you go out for a day trip and have to park in a carpark on a hill/slant, your fridge will be warm by the time you get back! When you get solar, it will also power itself for free rather than using expensive gas...spend to save! haha

 

[dwh]

Also, I've looked up the wiring stuff I asked about earlier, and can see the whole series & parallel thing, but what advantages does having 4 x 6V providing 450Ah @12V give, rather than having 2 x 12V providing (for example) 480Ah? Is it resilience, lower wear and tear or something else?

There's not much difference. All lead-acid batteries are just collections of 2v cells. 3 in series in a box is a 6v battery, 6 in series in a box is a 12v battery.

The main advantage of the lower voltage battery is that is has bigger 2v cells than a 12v battery of the same size and weight, which gives some benefit as regards the Peukert Effect. I.e., you'll end up with a few more usable amp*hours for a given size load.

The main disadvantage is that you'll end up with more wiring and connections.

A secondary advantage of the bigger cells is they are more rugged in terms of being able to handle shock and vibration.



People who want to squeeze every possible watt often end up with 2v L-16 batteries (one big cell), which they rig in series to get whatever voltage they're shooting for:



Or a forklift battery (a pile of big 2v cells, usually rigged as a 48v bank):





When talking about 2 or 4 automotive size batteries, I personally don't think there's all that much difference. It just comes down to preference really.

 

[Anton2k3]

Thanks for the info.

I do think thought that given that a microwave will be run through an inverter, traction batteries would be far better suited and outlast any leisure battery under the same conditions.


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[dwh]

I do think thought that given that a microwave will be run through an inverter, traction batteries would be far better suited and outlast any leisure battery under the same conditions.

I suppose it depends on definitions. If by traction you mean "true deep cycle", and by leisure you mean "RV/marine" batteries - then yes, you are absolutely correct.