Advice on battery charging

[lorrieandjas]

Hi Guys,

OK - I am confused. There seems to be two schools of thought on batteries and charging options. Bit of background - have a 2012 GU Patrol with stock battery. Have a camper-trailer with 2x75Ah AGM batteries in it. Have an Anderson plug on the trailer. In the past I have always just run an Anderson from the alternator via a relay (solenoid) to charge the rear batteries. I know several people with this kind of setup.

Now - in comes DC-DC chargers, battery management systems, etc. The question I have is this really needed? Basically the issues I see - under-charging - ie the alternator not putting out enough charge to charge the house batteries. The other issue is potentially over-charging/over-heating. The third issue (potentially) is not getting the house batteries to full charge?

I've been doing a little bit of looking into all this and the way I am thinking is to run an Anderson on the back of the Patrol with a bi-directional Voltage Sensing Relay inline and fuse. Then on the camper another fuse near the house batteries. I'll use 6 B&S (13.5sq.mm) cabling. I'll also use the portable solar panels (with regulator) when camping.

Thoughts?

[megatexture]

If you put a ctek 250s dual on the trailer or in place of the relay it will boost the amps from the alternator and can double as a solar regulator and will monitor both inputs at the same time.
I couldn't tell you if there will be a loss in performance by mounting the unit to the camper but it would be ideal as they have a temp monitor so it won't cook the batteries.

You can't rely on the alternator to fully charge agm batteries it won't happen.

I've done the voltage sensitive relay before and won't go back as that method was not maintaining my batteries properly redarc make a similar product also that might be worth looking at also but if you consider ctek then you won't get cheaper then on eBay

Also having a multistage charger will maintain the batteries when not in use at home.

[the evil twin]

This subject could easily run to a 100 pages alone but in as short a version as possible...

Alternators are "dumb" chargers IE they just sit there happily spinning away and produce a regulated voltage at up to their max current at whatever RPM they are spinning at and after that the voltage falls away.
Therefore an Alternator source relys totally on the battery/ies charge acceptance rate/s on how much charge goes back in over how much time. The higher the charge in a battery the lower the charge acceptance rate.

That is no biggee on an SLI battery (cranker) as all they do is a momentary large draw on start then sit there happily sucking up whatever small amount they need...
but...
can be a major issue on House batteries esp if there is a longer cable run and therefore voltage drop to the house battery such as in a camper.

I use dual sensing VSR's in my setup (two of them, one in the vehicle and one in the camper) and I have no issues whatsover BUT all four batteries are of roughly equal capacity and same technology. I can plug in any charging source (solar, smart charger, alternator) at any point and it will charge any battery that is "low". The way my useage pattern works out the lowest battery out of my four is usually the vehicle Aux

IMHO the bottom line is this...
If your useage is such that your house batteries consistently need to be charged from the vehicle OR you wish to use differing technolgy esp Calcium, Calcium hybrid OR you only want to run lighter gauge cable to the Caravan/Camper then you should opt for a DC/DC solution.
You can then get away with some voltage drop and also tailor the charge voltage to suit the application
otherwise...
If your house batteries are traditional lead acids and usually well charged from Solar/Mains or whatever then VSR's are absolutely OK IF the cable run is sufficient gauge.

In my case my camper batteries are always either;
on Solar so only needs it's morning top up for a couple of hours after overnight drain (approx 12 AH)
on Mains IE CTEK battery charger
or under tow so charging from the Alt

[lorrieandjas]

Thanks guys - now I am looking at the Redarc BCDC1240 DC-DC chargers but have been told because I have two AGMs hooked up in parallel in the camper I need two of them? Does this sound right to you guys??

Jas

[lorrieandjas]

Actually - disregard that - just called Redarc who confirmed in parallel you only need one! Bloody distributors don't know what they're talking about!

Jas

[the evil twin]

Thanks guys - now I am looking at the Redarc BCDC1240 DC-DC chargers but have been told because I have two AGMs hooked up in parallel in the camper I need two of them? Does this sound right to you guys??

Jas

If they are hard wired in parallel then No, you only need one as they appear as one battery to the device
If they can be selected one or the other then No you only need one just put it upstream of the selector switch
If they can be used independantly then, technically, yes you could use two

EDIT... DOH.... you beat me by one second ROFL

[the evil twin]

... I should add that I use a Cole Hersey switch in my rig and put it to both when towing but only normally run on one battery at Camp so there is one "on line" and the other is fully charged and off line.

[megatexture]

Mine is doing 3 batteries aux under the bonnet and two on the camper I have only ever had one issue and that was that the charger wouldn't charge due to the temps under the bonnet as it was 46 deg in the shade and flipping hot under the hood out at longreach.I disconnected the battery and just charged it via solar when we parked. If a ctek can do my 3 putting out 20amp I'm sure the redarc will cope with 2 Agm batts putting out 40amp

[threedogs]

There is a real danger of batteries exploded with high under bonnet temps,
My AUX is Trojan wet cell 105 AH with water kit.
they would not sell me a sealed one. well they would but would not install it
Worth thinking about, Evil Twin or Yendor may know more on this.

[lorrieandjas]

OK - so the setup I'm thinking now is the 40A DC-DC Redarc - the only thing I don't like about the Redarc is she isn't bi-directional - so the cranker technically can't be topped up if I throw a cell on the house batts - but not a huge issue - can always just connect the panels to the cranker if I need it.....

Now - in terms of fuses - 100A fuse near the cranker and near the house batteries?

Jas

[Cuppa]

Apologies if you've seen it before, but thought the diagram of my Redarc BCDC1240 setup might be of interest.

I removed the aux battery set up I had under the bonnet to save weight, & now charge 3 x 120ah AGM batteries (in parallel) in the pod via the BCDC from the wet crank battery. The set up gives me the ability to connect the 'house' batteries & the crank battery for winching purposes, or if I wish to charge the crank battery & house batteries all together from either solar, or from a mains charger. Although there is some weight in the heavy cables run from the pod to under the bonnet, I have no need to carry jumper leads, as I can jump start from the house batteries at the turn of a switch.
With one fixed panel (125w) on the cab roof, & the rest portable, the setup is designed so that the portables only need to be used if camping for more than a couple of nights, but to be self sufficient in power indefinitely when camped for longer periods. This runs two fridge freezers & the usual lighting etc.




Now - in terms of fuses - 100A fuse near the cranker and near the house batteries?



50amp fuses between the crank batteries & BCDC1240 & between the house batteries & BCDC1240, both as close to the batteries as possible, will be sufficient. re-settable circuit breakers would probably be better. I used something in between - re-settable fuses - essentially circuit breakers in a maxi fuse housing.

[alfonso]

sorry to hijack this thread but I have a question for cuppa .
I have 1 120 amp hour battery in the back of the ute, via a 150 amp projecta relay which does all my lights and fridge when working away . I also have a 20 amp 7 stage charger which I use nightly back at camp as the drive to jobs is very short . I also have a caravan which has 2 120 amp agm batteries with a built in 25 amp projecta 7 stage charger also have 2 b and s cable running from caravan to back of ute with 75 amp Anderson plug this works great when towing as all the batteries are fully charged before set off.
my question to you now is I am looking at solar panels 240 watt with mpps regulator connected to batteries in van. when I am charging from one of the other options ie 25 amp charger or Anderson plug will this damage mpps regulator, or
is this fine connection to solar panels will be via a 50 amp Anderson plug with 8 band s cable. I will also have a mppt regulator connected to the battery in the ute . Does this setup sound ok or have I made a balls up. Solar panel and regulators have not yet been purchased . Advice on this would also be greatly appreciated . Thanks in advance Alf

[Cuppa]

Hi Alf,
I am assuming you would connect the solar panels to either the van batteries or the ute aux battery as required to allow for usage of the ute without the van? This assumption is based on the fact that you plan to have two separate solar regs, so presumably you plan to be able to disconnect the panels, rather than having them permanently connected? There is no problem running a mains charger/alternator whilst the solar panels are connected to your battery(ies). The regulators will only be connected between the batteries & panels. Other charging sources will go direct tothe batteris (not through the regulators). Using solar panels to top up the batteries (above what the alternator will take them too) can be a reasonable alternative to a dc to dc charger if you have sufficient solar to bring the batteries up to full charge during daylight hours.
If you post a wiring diagram I would feel more confident advising you, but it sounds like you have it sussed to meet your needs.

Cuppa

[alfonso]

thanks cuppa you are spot on will be using van and camper independently I will draw a wiring diagram soon thanks for the quick reply . Ps any idea where to buy solar stuff

[threedogs]

How weird my cranker failed and I brought a new one from my battery place this time they sold me a seal battery, How bizarre, how bizarre
How have you found the Redarc system ???

[Cuppa]

. Ps any idea where to buy solar stuff

EBay is your friend for panels. For portables don't go above 120w folding panels, they get too cumbersome to move around.

Choose panels based on their dimensions (what fit's your storage space the best), plus the quality of their frames. A full frame that they 'lean on' is more secure than a single strut & can be pegged down if windy. Most likely they will be supplied with a regulator stuck on the back of the panel...... These can usually be carefully removed & thrown in the bin, together with the thin cabling supplied. Plastic corner pieces on the panel frames are good, otherwise corners can be sharp.

Back to regulators - you do tend to get what you pay for, all will work, but some work much better than others. Most cheap mppt types are unlikely to have their charging based on effective charging algorithms, & in such instances a PWM type of the same price is probably a better option. In my experience Morningstar regulators are good quality, but there are others. How much you pay for one will depend upon how many bells & whistles you want. I prefer regulators with a screen which tells you, at a minimum, the battery voltage and amps in. Many folk are happy with a couple of Led indicators, but I like to know a bit more about what is going on. One thing which is really worthwhile (much more than budget mppt) is temperature compensation, the type which has a sensor mounted on the battery, rather than just internally. Mppt is good, but expect to pay for one which lives up to it's promise. There is a reason for a difference in price between a $25 mppt reg &, for example, a a Blue Sky mppt reg costing hundreds of dollars. Many, if not all, of those cheapies supplied with the panels are a con. The only mppt thing about them is the printing on the case! (I know folk who have tested this).

Cuppa

[alfonso]

hey cuppa can you join two 120 watt portable systems together to create a 240 watt system Thanks Alf

[megatexture]

You can providing your regulator can take the 240watts and the max amp output of the panels.

[Cuppa]

You can providing your regulator can take the 240watts and the max amp output of the panels.

Hi Alf, yep, as MT says. You connect them together in parallel as you would with batteries. If you connect them together in series it'd give you a 120w 24v system (assuming you are using 12v panels). You would probably be ok with 15 amp regulators if of good quality (capable of running a bit above their nominal capacity), but certainly with 20 amp ones. If there is any possibility you will want to add further panels down the track, get regs with the capacity to suit now rather than ayer.

[alfonso]

Thanks for that fellas

[alfonso]

ok hopefully this will be my last question . Now as said I have a 150 amp regulator in car going to battery in back of ute ,Then I have cable running to rear of vehicle to Anderson plug from house battery pos only neg to chassis . As stated before I will be putting mppt regulator in vehicle for solar charging min 20 amp perminantly fixed . Now my question is can I put a dc to dc regulator with mppt in caravan to boost charge or will this not work with existing regulator in vehicle as they will be in line with each other my reason for all this is that I use different vehicles for towing and also use ute on its own mostly. As I only recently installed the regulator in vehicle I am loath to change it if possible. And if I use another vehicle for towing caravan Mercedes sprinter with just Anderson plug to cranking battery , i need to have a regulator in caravan with mppt for solar also This is my conundrum. So in effect when towing with ute i will be charging cranking battery then to regulator after which house battery in ute then to Anderson connections followed by dc dc charger next to 2 house batteries in caravan. All house batteries are 120 amp hour agm . Sorry for all the babble but this is how it sits in my muddled mind Thanks again Alf Ps have just worked out how to put map of installation on here so will draw one up tomorrow

[Cuppa]

1. i think you mean 150 amp relay (VSR -Voltage sensitive relay)?
2. Sounds like you want to 'daisy chain' alternator- crank battery-VSR-ute aux battery- DC to Dc charger- van battery?
3. A diagram would help.

Have not seen 2 done. Not sure how well it would work. It would certainly complicate any fault finding if a problem arose. For similar setups I've seen Redarc recommend alt -crank battery - VSR - Ute aux battery AND SEPARATELY crank battery - dc to dc charger -van battery. I reckon for the sake of a bit more wire keeping them separate would be worthwhile. when I bought my vehicle it had a dual battery system in it, utilising a VSR which I nitially intended to retain, plus adding more 'house' batteries. Redarc advised me as I have advised you.
In this instance the dc to dc charger would be mounted in the van as close to the van batteries as possible. it would make sense to use a combined dc to dc charger & solar regulator like Redarc's BCDC1225.

I would suggest NOT using the chassis for earth, but instead run dual cable. Again simplifies future fault finding. Remember that cable sizing should match the total length of positive & negative cables. http://hobohome.com/news/?p=581


Cuppa

[alfonso]

Thanks cuppa now that makes complete sense it is perfect for my needs you are a legend . hope my stones in sill theory works as well for you Alf

[FNQGU]

Cuppa, thanks for the diagrams. I particularly like your idea of a manual 3-way switch to allow charging of the starter battery from your panels / AC source. I am currently considering installing either a BMS or simply a BCDC to manage the house battery, and have been contemplating the whole management of the starter battery at the same time. For me it has been a problem as I am away with work for a month at a time, and have in the past found the start battery nearly flat when I come home. To combat this, I have been leaving a small C-tek 7Amp charger connected, which has worked well and has kept both batteries in good condition via a VSR, and I would like to continue this practice.

My house battery has until recently been a 66Ahr Optima Blue Top, which was not really a good choice. Great battery, but not for this purpose. It is now a 105Ahr Full River AGM. I changed it after I had a bit of a scare on a recent trip when using the stereo for a moderate (I thought short) period of time, causing the starter battery (Optima Red top) to run down very quickly. This was compounded by a problem with the 240v plug from a generator to the Engel not working (faulty connection found later), and the fridge nearly flattening my house battery after two days camping. Suddenly I had almost no power to start the truck and was two and a half hours drive from the nearest help with a flat house battery that I would have relied on to jump start the starter battery (yes, I had the generator as my last contingency, but not the point really...). Luckily the Optima Batteries have pretty good cranking power and it still managed to start the engine, much to my relief.

I am now also looking to move the UHF and car stereo power sources from the starter across to the House battery for further peace of mind when camping remotely.

As my house battery is under the vehicle (passengers side), I am looking at mounting the BCDC inside the vehicle as mentioned in a previous thread, on the back side of the drawers (ie. behind the back seats), with a cable gland keeping water out where I drill a hole through the floor. Of interest, my local battery supplier highly recommended the Full River batteries, but said the BCDC40 would be too much for it, and rather the BCDC25 would be perfect.

I will probably also run a cable to the rear of the vehicle at this same time to use in the future for charging batteries in a camper from the alternator.

Where do you have this manual 3-way switch installed? I am guessing it is in the cab if you have it co-located with your winch connecting switch? Any chance of a pic?