24V to 12V split charger?

[Tony LEE]

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

One of those "it depends" situations. Going for compressor fridge without installing a substantial solar system is just not going to work unless you are going to be on the move every day or two - and it is no good just doubling the battery capacity to cope, because you then have to get the batteries charged somehow and that is NOT going to happen on a 2-hour drive..
As for unlevel fridges - modern ones can cope with 6 degrees one way and 4 degrees the other and that is too much of a slope to be camping. Yes, you do have to watch it a bit if you are parked way out of level for a couple of hours but it is pretty easy to just switch it off during that time.

I have vehicles with both systems and agree that in Australia and similar climates where temperatures can be very high, compressor fridges do have an advantage (although most there are normal three way absorption type with T rated being preferred) but in Europe, Morocco in winter, much of the US, southern US in winter, Mexico in winter etc, most are using absorption fridges and coping perfectly well. In those areas, propane is plentiful so usage isn't a factor.

 

[1Engine]

I use one of these Charge Equalizers on my 24V Isuzu NPS300
http://www.redarc.com.au/images/uploads/images/CE_Instruction_Manual.pdf

Also I found it is also worth while talking to your local Caterpillar Dealer for Batteries. Here is Aus they are very competitive & the batteries are made for extreme vibration etc

 

[andylod]

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:

View attachment 156453

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

View attachment 156454



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.

I think that perhaps another consideration for using 12v more standard physical size batteries, is that they could be used in an emergency if a problem occurred with the vehicle batteries.

Andy

 

[dwh]

I think that perhaps another consideration for using 12v more standard physical size batteries, is that they could be used in an emergency if a problem occurred with the vehicle batteries.

Andy

Yea, true. Interchangeability could become very important out in the middle of nowhere.

 

[Anton2k3]

This is true. But then with an inverter installed, you can just use a battery charger to charge the vehicle batteries off the camper batteries....this is something I had to do everytime i needed to start the van after our starter batteries died in europe, until I managed to find some replacements.

 

[Arfur's World]

Battery bang for your buck

Hi All,
I did a little calculation from the Trojan batteries catalogue to see if there were economies in buying bigger batteries, but it seems that 4 x T-105 are the cheapest way of getting over 400Ah. If you want to stick with 12v cells, then there is a hefty premium. Prices from eBay.



Still unsure which way I'll go, the van came with 2 x 629 batteries which I may try to revive and see how they work out ... but they aren't deep cycle so I think that'll not be the long term way forward.

Also, regarding the help with starting in an emergency issue, I was thinking of having the leisure bank connected to the van batteries, with a big switch for use if needed, would that work? Instant jump start ...

 

[Anton2k3]

The leisure batteries to battery bank may not work if one is 12v, and the other is 24v.

 

[mervifwdc]

On our Mog we have 2 alternators, a 24V one and a 12V one, so that we run both systems all the time, and have 2 separate battery banks. Not sure if this might suit you as you will not be always connected to the caravan, but it's worth letting folks know about this option.

Merv.

 

[pier1234]

Hello,

My 1300L Unimog is on 24 volts and so will be my camper battery (2X225volt (12 volts)). There will be 360 watt solar panels and a Victron Multiplus combining 40 Amp charger/1600 watt converter. Leaving next year hopefully for many years

I could use Merv's solution but as I may add a belt and pulley driven compressor for Air Conditioning, space may be missing.

The Sterling Battery to Battery charger is interesting, the BB24-24-30 Amp model.

But since my alternator is 24 volt 55 Amp, Would I be better with the Sterling Alternator to Battery Charger which is up to 80 Amp. What are the pros and cons of each model?

The cost is similar, would the A to B charge significantly faster than the B to B?

Which one woud be more reliable on the long run?

Which one will be more "gentle" on the batteries and the alternator?

Your comments will be very much appreciated.

Pierre

 

[mervifwdc]

If at all possible, I would urge you to look at the two alternator option if you are skipping the aircon. Most cities will have a place that can rebuild an alternator, but when you put in anything different, like the sterling alternator stuff, it's electronics and gets the general mechanics confused. Keep it simple, go with simple and standard alternators.

I have removed the sterling units from my truck, 3 years of hammering around deserts and crossing oceans did not do them any good at all! I'm now using standard alternators, and have gone for ones with internal regulators and bypassed the unimogs own regulator.

KISS.

Merv.

 

[surfer4life]

Hi,

i have a merc vario camper and run a sterling 24v to 24v split charger, my leisures (4 x 113AH) are at 24v and half the bank is then split to 12v through a simple control panel and 24v to 12v converter (alfatronix). i considered using the gubbins from a caravan but decided against it and also bought a sterling 240v to 24v charger (pro charge i think) this also regulates the charging like the B2B system and can act as a 240v hook up, i thought that after spending £400+ on batteries it would be daft to scrimp on the charging of them to keep them in tip top condition.

Also someone commented here about compressor fridges not running off solar in the UK, i have a 140 litre shoreline compressor fridge (pretty much full size) and have 200W of solar running through an MPPT controller, even in winter my batteries are kept charged with the fridge running, in summer, it runs the fridge and puts enough back in the system to run everything else i have, its only when i use the ps3 and 24" hd tv for more than a couple of hours a night that i start to struggle, but would last 3 days without moving.

If some people are running solar and not through an mppt then this would affect how much power they are getting out of their panels and could make them think that its not upto the job of running a fridge, a decent compresor fridge will run at around 0.8 AH/hr so worse case will use 24 AH a day, your battery bank will be over 400AH but usually only 50% available before running down, so lets say 200AH, so if you only used the fridge and nothing else, with no solar and no charging your fridge would last 8 days, before you need to think about charging your leisures. A compressor fridge was one of the best things a bought for my van.

 

[pier1234]

Hello,

Thanks Merv for your explanation. I 'm sure you are right but I don't like it.

If I can't add a second alternator, I need to find the second best solution. Any other comments from Merv or others on this second best solution?

Sterling Alternator to battery charger
Sterling Battery to Battery charger,
Victron Cyrix battery combiner
Victron Argofet battery isolator.

Reliability is my number one priority, then comes complete battery charging and simplicity.

Thanks,

Pierre

 

[Anton2k3]

Hi Pierre,

The alternator to battery chargers are for a single voltage, i.e 24v. Thus if you want to charge a 12v camper system from it, it will not be possible ( i think).

Thus, and i am biased, i'd say the battery to battery charger would be best in a situation where 12v charging is required. I have had no reliability issues with mine thus far (2 years old), and even if I do, sterling are very good at sorting things out.

It is also very simple to install, and does exactly what it says on the tin, mine charges at no less than 30a.

 

[surfer4life]

i dont think sterling do a 24v to 12v alternator to battery charger, if the alternator charger was the one you want, then you could quite easliy run your leisures at 24v, then drop to 12v for the 12v feeds you need. Compressor fridges, propex or diesel heaters, water pumps, led lights - all can come in 24v, then use an alfatronix 24v to 12v converter for your tv, cooker, toilet etc..

the advantage of the alternator to battery charger is the amount of charge they can put in, but the battery to battery are easier to fit and come in a 24v to 12v configuration, but charge less.

 

[pier1234]

Thanks Anton2k3 and Surfer4life,

My situation will be similar to Surfer4life as I will run my leasure batteries and 99% of my equipment on 24v.

I understand from Anton2k3 that the 24V-30A battery to battery charger would really give its rated 30A.

Surfer4life, how many amp are your alternator and charger? Do you feel it charges much faster than the 30A Anton2k3 gets?

My alternator is 55 amp and my charger would be 80 amp.

Pierre