split charge system

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Hello,

I am looking for some advice on a split charge system. I want to charge two 125ah AGM batteries that run my inverter. I want to be able to charge from the vehicles own supply, solar and a battery charger. Does anyone know of a product that can do this that does not cost a months wages?

Thanks
 
Yes I know of such a product and have been using it for years now :)
 
Hi hippy i would also like to know this information.PM me on my e-mail address you have if you dont want to reply to phils post.
Thanks in advance.
 
I've got exactly the same set up with two 110Ah (minus the solar), but I will be adding the solar soon.

I simply use a 45 A trip switch in a 100A cable between the main battery and the leisure batteries. When I get on the road I just flick the switch to connect. When I go on site I flick the switch to isolate. If you want it automatic just use a relay instead of the switch. My system has the advantage the leisure batteries could be used to help start the van in an emergency (they are supposed to be rated for starting, but I wouldn't make a habit of it). I can also manually disconnect alternator charging to prevent gassing after a couple of hours on the road if I want.

The 240v charger is run off the hook up via the RCB consumer unit and is simply an electronic smart charger from Halfords. It can be permanently connected and stops charging going to monitor mode when the battery is fully charged.

With the solar panels you should be able to buy a small electronic control box of tricks which again monitors the battery state and only adds charge when it is below fully charged voltage.

So, you don't need anything special for it all to work, just a decent current rated switch in the simplest design ;)
 
coolasluck said:
Hi hippy i would also like to know this information.PM me on my e-mail address you have if you dont want to reply to phils post.
Thanks in advance.
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As a humble free member I don't think there is any way for me to contact you on this web site other than on the open forum.
 
coolasluck said:
Damn I was going to charge Phil 15 big ones for the answer:D
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It's OK, there are probably better answers than mine, it's just one possible answer :D

No doubt you could build or buy an even bigger box of tricks that monitors combined the leisure battery charge as well as all the possible charging inputs and selects the best ones like an automatic three way fridge. And not only that, it gives the best charging profile rather like those Stirling thingies.

But, you don't actually need that in a practical set up.
 
Firefox said:
It's OK, there are probably better answers than mine, it's just one possible answer :D

No doubt you could build or buy an even bigger box of tricks that monitors combined the leisure battery charge as well as all the possible charging inputs and selects the best ones like an automatic three way fridge. And not only that, it gives the best charging profile rather like those Stirling thingies.

But, you don't actually need that in a practical set up.
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Sounds like i need to get myself to the library and do some more reading.
I rewired my house lighting circuits after the last read from the library,today electrics,tommorow brain surgery and the day after .......well the world:)
 
hi. i use a system very similasr but i make and break it with a suzy connector to the trailer.
trouble with mixing alt power and solar is one can confuse the other that the batteries are full .i find it best if travelling to switch off the incoming solar and just rely on the alternater power.(mine is actually from a 24cto 12v charger as my truck is 24v. )
in the past i used one of those big red key isolation switches .they are what i use on the solar.(handy if playing with alterations.)
 
Yes, I could have used the red key type isolator as my switch. You can get them in Halfords. I was going to until I found the 45 A trips in Wickes. They are AC circuit breakers designed to go in a fuse box but you can use AC switches for DC too. The problem with AC switches used for DC is you can get more arcing across the contacts, but if the voltage isn't too big (eg 12V) they work just fine.

Whatever switch you use make sure it is a high current one. Those 10-15A switches for accessory circuits will burn out under charging currents.
 
vwalan said:
trouble with mixing alt power and solar is one can confuse the other that the batteries are full .
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I have to battle with this on the RE systems I work with at least weekly. On all but the most exotic there is only one piece of data that is shared between the various charge controllers - that is the battery terminal voltage. This is measured digitally with high impedance circuits so is utterly meaningless. What's more you get a surface charge effect.

Imagine the system where you have solar panels and a generator. Solar panels are charging well, then the cloud comes in. Unless you are drawing a load the batteries have a high plate surface charge which will make the generator charge controller "think" that the batteries are fully charged and so it doesn't need to put in any more power - even if there's another 25% or so necessary for full charge.

there's a world of difference between what the sales people say and the engineers when eventually you get through to them and you can start working with them to create working bespoke systems for the client.

It gets even more interesting with solar/generator/wind three way systems - we end up staggering charging thresholds so that one doesn't inhibit the next.

Some of the boat people even have four different charging sources - have yet to work on one of those :)

Mild Red
 
i keep trying to explain this to friends when away in winter .they think i make it up .but experiance as proven it to me. a mate put a big second alternator on his truck to charge the 12v system but it never seems to work. he dont belive me it might be better to switch his panels off when travelling. but never mind its his battery thats flat not mine.
 
vwalan said:
i keep trying to explain this to friends when away in winter .they think i make it up .but experiance as proven it to me. a mate put a big second alternator on his truck to charge the 12v system but it never seems to work. he dont belive me it might be better to switch his panels off when travelling. but never mind its his battery thats flat not mine.
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Never really thought about it like that, but never had flat batteries, but it all makes sense. So from now on I will be turning my solar control panel off whilst travelling.
 
my mates truck is 24 volt .he wont buy a 24v to 12v charger so thought put a 12v alt on .maybe he will listen. it took me a while to work it out . its one of those things usually nobody tells you. i also think the cold air going over the panel can stop it working but cant give definate proof yet. maybe mildred can let us know. or tony lee . i dont mind learning something ever day.
 
Here is an idea that a few of the T4 owners are using.

Use a relatively cheap (about £12.00) 30a smartcombi split charge relay but not to charge the battery, instead use it to trigger a big 100amp relay (again not expensive) to do the actual charging. You need heavy cables on the charging side and it may shorten battery life. Also a good idea to make sure the battery box is well vented.

I do have a pic of the wiring diagram if it is any help.

That is a very cheap option that is easy to fit and will work but you might be far better off and far safer spending some proper cash on a decent system.

I am using 2 of the 30a smart combi,s side by side but only use one 110 amp battery.


No idea how you would work solar into that though.
 
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to be honest that seemsliken expensive way of joining the batteries a big manual switch is very cheap and at least you have control.
start on engine battery then switch the leisure side on. simple .i find relays always go wrong just when you need them. big cable big switch. perfect.
 
So from now on I will be turning my solar control panel off whilst travelling.
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I wouldn't bother. Probably better to let the alternator do what it can and then switch it off and let the solar finish the job.

Problem as I see it is it's not the solar causing the problems for the alternator as much as the alternator split charge system stopping the solar.

unless you have a special alternator and large cables, the charging system is going to decrease the output voltage/current according to the requirements of the starting battery. This doesn't need 100% charge to do its job so the system is more designed to prevent overcharging the start battery. The rest of the car electrical system is really designed to work on around 13.5V so no point in overstressing all that gear just to fully-charge the battery which doesn't need it anyway.

Plenty of contention about whether an alternator can fully charge a leisure battery except during very long drives. Same goes for using a 'converter" (240Vac to 13.7vDC) to "charge a battery" when on shore power. May keep a full battery full, but takes forever to fully charge a flat battery.

Anyway, back to the subject. While ever a relay-type split charging system is working, the solar output is also going to be connected to both batteries and the car's electrical circuit, so is not going to be able to correctly charge the leisure battery.

Would take a lot of calculations involving source and load impedances and output voltages and currents which are all dynamic in nature to work out exactly what is the best configuration and best timing for switching one source on or off - so it may not be worth doing anything.

It is true that one charging source can interfere with another and this usually shows up by the solar or mains charger indicator lights cycling between the different stages. Again, unlikely to cause any problems, but may be a bit upsetting to the owner.

I've had all three sources charging my batteries at the same time (40A mains charger, 280A alternator and 600W of solar) and seen no signs of instability. Your system might differ.

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to be honest that seemsliken expensive way of joining the batteries a big manual switch is very cheap and at least you have control.
start on engine battery then switch the leisure side on. simple .i find relays always go wrong just when you need them. big cable big switch. perfect.
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Yes, but only until you forget and end up with either a flat starter battery or a flat leisure battery. At the very least us the oil pressure switch or ignition circuit to switch a relay on and off as the engine runs. Still not perfect but about the cheapest way to overcome forgetfulness.
 
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