Charging house batteries from the tug....

Baz421 · Guru

RE: Charging house batteries from the tug....

aussie_paul · Guru

Baz421 wrote:
Yes tried it Paul,,, problem is that it doesn't deliver 8A as that is theoretical output only.
I tried our Honda 2.0 with single 12V battery and amp meter years ago. Battery voltage rises but very little current charged/flowed.
Also years ago I used a Yammy on a boat into 3 batteries in parallel for hours and was also useless ,,, just gave a "surface charge" I think they call it.
Chargers aren't that expensive.

Ok, and thanks again Barry. I did not get anything much done the last couple of days due to being a bit off colour and extremely cold. Hopefully tomorrow after I take the Pajero for its timing change recall and the auto oil flushed I might set the diesel heating going and lay some wiring down.. Well, that's the plan...

Aussie Paul. smile

aussie_paul · Guru

Had a better run today, took the Pajero for the recall on the timing chain and had the auto transmission and rear diff oil changed. They even washed it. I succeeded in routing 6 B&S cables from the batteries to the Setec alongside the cables already in place.

Tomorrow taking the Pajero to auto elec to have 6 B&S from the alternator and isolation relay to an Anderson plug at the tow bar to supply the DC to DC charger. I will, as energy allows, continue with the rewiring of the van. I have shifted the solar regulators to a position I can see them with a casual glance. Now leads of appropriate size for laptop charger, CPAP machine, inverter, diesel heater etc.

Aussie Paul. smile

PeterD · Guru

aussie_paul wrote:
Has anyone used the 12volt 8 amp DC output from a genset through a DC to DC charger to the house batteries?

This paper will answer your question.

aussie_paul · Guru

PeterD wrote:
aussie_paul wrote:
Has anyone used the 12volt 8 amp DC output from a genset through a DC to DC charger to the house batteries?
This paper will answer your question.

Thanks Peter great reading.

Aussie Paul. smile

greyhoundtom · Senior Member

Yes Peter thank you a lot of worthwhile information.

Unfortunately for me it certainly has raised a huge doubt in my mind about the ability of the Setec charger fitted to my Jayco to be able to charge the house battery via an EBay purchased 3000/3500 watt Gentrax supposedly pure sine wave generator.

I was really counting on this being possible whenever 240 volt was not available as financially solar panels, additional batteries, and an inverter are just not possible at this time.

Can anyone shed light on this situation, or have I stuffed up again going in that direction in trying to partially solve our power requirements?

aussie_paul · Guru

Picked up my Supercheap $149 DC to DC charger this morning. Attached specs.

Aussie Paul. smile

-- Edited by aussie_paul on Saturday 1st of August 2015 03:27:02 PM

Cruising Cruze · Guru

Hi Paul

The Ctec MXS15 is not a bad one to use

they are around $239 on Evil Bay

Cheers John

Jaahn · Guru

Hi biggrin

If you are thinking of using a genny to charge the batteries when necessary due to low solar or whatever, then you need a decent sized charger. Having a 15a or 20a charger would mean that you have to run the genny all day hmm

Example one person said they had 2x 120AH batteries. If they were down to 50% charge then they require 120 Amp Hours to get back to fully charged.

At 20 amps input this means they will need 6 hours of the genny running in theory. In practice MORE actually to get them fully charged with a multi step charger.

At 8 amps it would be, well all day from sunup to sunset really furious and then some !

So you can see that you need a much bigger 240v charger to reduce the time for running the genny, so take that into consideration.

More solar may be cheaper ! It does work from sunup to sundown and is cheap to run and quiet ETC biggrin

Jaahn

greyhoundtom · Senior Member

Thanks Jaahn that makes perfect sense, and going by that it means that the Setec charger fitted to my Jayco van to run the whole system is not going to do the job of maintaining a full charge to the two C/van batteries with intermittent generator use.

Time to rethink my options. :(

Cheers,
Tom

aussie_paul · Guru

The last couple of weeks progress.

1. Ran 6B&S cable from batteries to Setec.

2. Shifted solar controller to where I can monitor it, and upgraded wiring to batteries.

3. Parallelled the original Setec input wire and fridge wire to fridge, fed from the original 8 B&S cable from Tug alternator through Isolation relay.

4. New 6 B&S cable from tug alternator to Anderson plug.

5. DC to DC charger fitted and run from the Anderson plug.

6. 8 B&S cable routed to solar controller ready for new 200 watt panel to be fitted when sons can assist.

Finally the time for testing my DCDC charger installation. Worked perfectly. Now need to tidy up with cable ties etc, and make quite a few labels, AND draw a diagram to help with future memory lapses!!!!!!!!! biggrin

Aussie Paul. smile

Radar · Guru

Hi Paul

Been following your working progress, must say from other peoples replies have cleared up a few things I didn't understand and now know what direction to go without major expence.

Thank you all much appreciated, learnt some more.

We have in the caravan a 120 amp battery, 140 watt solar panel, a cetex 20 amp charger for when we are on 240. Anderson plug feeding the 3 way frig direct from tug with Redarc Switch which also has a cable running to a second battery in the tug when on the go.

We are using good size wiring in our work.

I have now lost the gen set, in 8 months of travel, was not used, back on the shelf with it.

We will be purchasing a dc to dc charger and that will give me my safe guard if the solar not doing it's job or we over do things with our usage of battery power by hooking the car up and running it for a while and all at a reasonable price.

Thank you. Ralph.

ps. Now for an inverter, can't get my head around that one.

-- Edited by Radar on Thursday 6th of August 2015 03:51:25 PM

aussie_paul · Guru

Thanks Ralph, I feel if I need help and ask for it, all members can learn. I knew a heck of a lot about flying building gyroplanes over an almost 50 year period. By joining a world wide gyroplane forum based in the US I was helped immensely by the gyroplane community because I was not too afraid to ask for help, and reported every test I did as proof of concept when I did not think it was the right way to go. No blind faith, I just have to know the "how and why" by asking, testing, and making errors.

Now I am in a new ball game, and it takes some getting one's head around this self contained RV stuff, BUT same thing is happening here, asking question and receiving help. biggrin

I still need the genset for the aircon as my burns/skin grafting have not left me enough sweat glands. Maybe a split system if/when this one karks it!!!!

Aussie Paul. smile

-- Edited by aussie_paul on Thursday 6th of August 2015 04:04:53 PM

Radar · Guru

Hi Paul a very good reason to be carrying a gen set and you will be welcome in my space at camp site, hopefully in the near future.

You will recognise me I be in the knife draw just pick the blunt one.

Cheers. Ralph.

-- Edited by Radar on Thursday 6th of August 2015 10:24:36 PM

aussie_paul · Guru

Question, now with my DC to DC charger from the tug, all I would have to do is run the tug while camped if needed. Would that be as efficient as running the genset and a designated 240V charger?

Aussie Paul. smile

PeterD · Guru

aussie_paul wrote:
Anyone actually tried the 12volt 8 amp DC output from a genset through a DC to DC charger to the house batteries?
Aussie Paul.

I would not even try if I had one. The EU20i Portable Honda Generator12 V output is only rated at 8 A. You would need a much larger OP generator to run an 8 A DC-DC charger. The 12 V output from these generators is just the exciter that supplies the field of the generator that supplies the 240 V in a lot of these units.

PeterD · Guru

aussie_paul wrote:
Question, now with my DC to DC charger from the tug, all I would have to do is run the tug while camped if needed. Would that be as efficient as running the genset and a designated 240V charger?
Aussie Paul.

I thought the answer was obvious. No. Just think, why would you run a truck motor at idle for several hours just to charge a battery? What would the consequences for the motor doing that? I don't like idling motors for too long, I switch them off when caught at road works to save the motor.

aussie_paul · Guru

PeterD wrote:

I thought the answer was obvious. No. Just think, why would you run a truck motor at idle for several hours just to charge a battery? What would the consequences for the motor doing that? I don't like idling motors for too long, I switch them off when caught at road works to save the motor.

Hey, condescending Peter, if it was obvious I would not have asked!!! disbelief

Aussie Paul. smile

greyhoundtom · Senior Member

While the discussion is on in regard to charging the van batteries with the tow vehicle alternator via a DC to DC charger, could someone enlighten me how much of a handicap it would be to charging the batteries in the van if the DC to DC charger was fitted in the far rear of the tug and the battery location in the van was within 2 metres of the towball.

I do have a valid reason for wanting to locate everything this way,which is too long winded to explain, and I do intent to use heavy wiring and Anderson plugs to connect everything together in an effort to minimize voltage drop.

Cheers,
Tom

greyhoundtom · Senior Member

aussie_paul wrote:
PeterD wrote:

I thought the answer was obvious. No. Just think, why would you run a truck motor at idle for several hours just to charge a battery? What would the consequences for the motor doing that? I don't like idling motors for too long, I switch them off when caught at road works to save the motor.
And yet I see people do this time and time again to top up the batteries when the sun has gone down instead of starting their generator. To be quite honest I would have contemplated doing the same thing myself until this discussion.

-- Edited by greyhoundtom on Saturday 15th of August 2015 07:23:57 PM

Radar · Guru

Hang about, I recall when a guy asked about a portable generator for recharging his caravan battery was told it would be far quicker and cheaper to use the tug to bring the batteries back up then to go out and buy a generator and run it for that odd time it may be needed.

So techs amongst us are changing there mines again or am I miss reading again.

Jaahn · Guru

Radar wrote:
Hang about, I recall when a guy asked about a portable generator for recharging his caravan battery was told it would be far quicker and cheaper to use the tug to bring the batteries back up then to go out and buy a generator and run it for that odd time it may be needed.
So techs amongst us are changing there mines again or am I miss reading again.

Hi Radar and others,

I think the problem here is getting a handle on the scale of the charging needed. People have trouble getting their head around the electrical terms and the quantity of them. confuse

Here is a suggestion to help. You have the water tanks to fill. You have several ways to do this; a bucket, a kitchen pot; a hose. Now it is obvious that the hose is best to use as it has a great flow and can be just left on till it fills. BUT you do not have a tap when free camping so the other ways have to do then. So would you use the pot or the bucket.

You would use the biggest bucket you can so the number of trips from the water is the least. So get the biggest bucket and see how many bucket loads you need. The pot would take forever to fill the tank. disbelief

This is what happens with the charging. You must look at the ways you have available and see how long it will take to fill that battery(tank). Using a 20amp charger or a 20amp DC-DC charger is like using the pot, it will take all day. The solar panels are OK doing this all day because this is their normal function to work all day. Or the DC-DC charger is OK when driving as you are doing nothing else, but any other time 20Amp is too slow.

The same is true for a genny. If you only have a 20amp 240v charger then the genny will run all day. Back to the pot idea of filling the tank. You need to get a decent charging method or even two that put a reasonably large number of amps into the battery so the time is short to do it. Look at the amps as the size of the bucket and the battery amp-hours as the liters in the tank. Then see how many you need. confuse

I hope this may help.

Jaahn

The alternator will put out around 70-100 amps in the tug so if you can use that full output it may be a good idea for an occasional use. But it is not recommended for normal use to leave it running on no load for hours as has already been pointed out.

-- Edited by Jaahn on Sunday 16th of August 2015 12:25:45 PM

Radar · Guru

In my case it would be for that occasionally use to run the car and recharge the batterys for the lights that night and I figure that would do me by everything I have read as we use the battery at minumal.

Now Paul would be extreme but worthy case, Paul runs a high usage medical apparatus, he has spent the money, gone to fair amount of trouble. I believe he trying very hard not to rely on a generator as his back up.

I think the remainder are interested in alternative ways of recharging on a dull day when the there is no sun.

Thank you for all your help. I know I have changed some of my ways for the better from the hints and tips from this forum. Ralph.

-- Edited by Radar on Sunday 16th of August 2015 10:48:23 AM

greyhoundtom · Senior Member

In most instances with modern cars and their tweaked alternators there will be a DC to DC charger fitted or else the voltage from the tug will not charge a AGM battery, and the most commonly used of these still only charges at 20 amps at best.

Therefore I can see virtually no difference in using the gennie and the in house charger, as compared to running the vehicle motor.
Both are going to charge the batteries at a nominal 20 amps, which in my case having fitted two house batteries, and if these were at 50% discharged would most likely take more than 5 hours to reach 80%, and if I understand it correctly will take an additional 5 hours to reach full charge.

Cheers,
Tom

aussie_paul · Guru

My master 12 volt DC switch now.

Aussie Paul. smile

-- Edited by aussie_paul on Wednesday 19th of August 2015 08:58:32 PM

Baz421 · Guru

aussie_paul wrote:
My master 12 volt DC switch now.
Aussie Paul.

-- Edited by aussie_paul on Wednesday 19th of August 2015 08:58:32 PM

We use one of these on 1000w inverter in van I can turn on/off from my bed very convenient. Used before on boats very reliable IMHO.

aussie_paul · Guru

Would plugging my 120 watt portable solar without regulator into the DC to DC charger be worthwhile??

Aussie Paul. smile

greyhoundtom · Senior Member

Hi Paul,

I will be very interested in that answer myself as I have just one 8mm cable going from an Anderson plug on the drawbar to the battery and wanted to use that one cable for both plugging in my relocatable solar panel as well as the current coming from the tug while driving.

I have not yet fitted a DC to DC charger in that 8mm cable as yet as I'm unsure if I did that would I still be able to plug the solar panel into it with the existing controller on the panel still functional.
Basically as I understand it the controller on the panel will vary its output depending on the state of charge of the battery it's plugged into, and by plugging it into a DC to DC charger instead of directly into the battery should by rights cause problems to the solar controller.

Like you I think I would be better off disabling the controller on the panel and plugging the raw output from the panel into the DC to DC charger directly, and just let it sort out what charge to deliver to the battery.

Cheers, Tom

greyhoundtom · Senior Member

Further to the above;

The other problem that I perceive to exist with having the solar controller as it is at the moment glued to the rear of the portable panel, is the 5 meters of cable that runs from the panel controller to the plug on the drawbar and the additional 2 meters from there to the battery is the voltage drop in that cable between the output of the controller and the battery.

As it is in my mind the current cable is far too thin and I will replace it with a 6mm as soon as my health allows me to get stuck into a few things again.

There again being so damn ignorant on how these controllers work it would be nice to think that if the output of the solar controller governs its output based on perceived battery voltage, and there is a voltage drop in the cable that measures that battery voltage, that the controller would automatically increase its output voltage to account for that voltage drop.

Because if that was the case, and a DC to DC charger operated under the same principle, it would not really matter if that charger was further away from the battery because it would also boost its output to take that voltage drop into consideration. However looking at all that if a solar controller worked on a different principle than a DC to DC charger, and if that DC to DC charger worked on a fixed charging voltage and therefore needed to be fitted as close as possible to the battery, just maybe I should be fitting a solar charger to charge the van batteries from the tug instead of the accepted method of a dedicated DC to DC charger.

But then I doubt that any solar controller would be able to handle the high current that an alternator is capable of producing.

Yes I know it's still very early in the morning and I'm away with the fairies again. Lol

Cheer, Tom

-- Edited by greyhoundtom on Saturday 5th of September 2015 05:36:31 AM

PeterD · Guru

Paul, that depends upon what DC-DC charger you have. If it is the Ctek D250S there will be a dedicated solar input on it. If it is one Redarc ones that is built to be both alternator and solar input that will be OK. However you will probably have to forget the rest.