Twenty minutes

Ron-D · Guru

Twenty minutes

Terryt · Veteran Member

Great if it works for him but I would have thought if a battery is topped up in 20 minutes it wasn't down tooo far to start with. Don't be mislead by what a voltmeter may show during or shortly after you have been charging a battery.

Delta18 · Guru

Terryt wrote:
Great if it works for him but I would have thought if a battery is topped up in 20 minutes it wasn't down tooo far to start with. Don't be mislead by what a voltmeter may show during or shortly after you have been charging a battery.

Correct, most of that 20 minutes running would be used up trying to replace the capacity used to start the car confuse

Jaahn · Guru

Delta18 wrote:
Terryt wrote:
Great if it works for him but I would have thought if a battery is topped up in 20 minutes it wasn't down tooo far to start with. Don't be mislead by what a voltmeter may show during or shortly after you have been charging a battery.
Correct, most of that 20 minutes running would be used up trying to replace the capacity used to start the car

Delta, Incorrect ! The starting power will only take a couple of minutes if it starts normally like all modern motors do. aww

I have a 120Amp alternator on my MH so it puts a lot in in a quick time if I need it. Easier that a generator and nothing to do getting it out or staring it etc wink Great idea.

Jaahn

macka17 · Guru

Everybody to their own Jaan.

First time you get a week of wet. Cloudy days. NO mains avail.
then try running car for 20 min's.
Anywhere in the REAL queensland.
North of Gladdy.

Just make sure you boot throttle a coupla times.
excite the Alt into firing too.

That's why us old schoolers have genny's.

Or some.
a BIG back pocket to waste on super battery's and reg's.

Everybody see that thing on Tesla system giveaway.
for 5 on teev tonight. Battery pack PLUS solar system.
Di saw it.

Warren-Pat_01 · Guru

One other point to remember is that if an AGM battery is the Aux or Van battery, it takes longer to charge than a normal Start battery in the car. They have thicker plates to cope with a steady discharge over a long period of time. But when all else fails Ron, it is better than living in the dark.

PeterD · Guru

Delta18 wrote:
Correct, most of that 20 minutes running would be used up trying to replace the capacity used to start the car

Not correct. A diesel in good order will draw 400 A or so when starting. How long does it take to start a motor. Most people I have observed do not run their glow plugs before starting so it will take less than 2 seconds to start the motor. What fraction of an hour is two seconds? What ever it is, divide that into 400 and that is how many amp hours you use to start the motor.

rockylizard · Guru

Gday...

Bear with me, I am likely to be long-winded (once agen hmm ).

Am I right to assume the ability of a vehicle's alternator to charge (re-charge?) its own battery (and maybe an auxiliary battery under the bonnet) and then the house battery in a van would vary considerably from vehicle to vehicle, depending on the age of the vehicle and the 'charging system' it employs.

I believe, from what I have gained from forums such as this one, that modern alternators do not charge beyond the vehicle's main battery ... once that battery gets to 'full' charge, the alternator 'drops back' the voltage it provides. To charge beyond the main requires 'additional' devices - eg DC-DC charger, charge controller etc.

Having said all that, a few years ago, before I had my solar setup, and camped away from 240v regularly, if I did a number of overnight only stops and then only drove about three hours each day, I had difficulty keeping my battery up ... to the extent that often on about the 4th or 5th night, I would run out of battery before getting to bed.

When I had an auto elec check out my 'system' he found all was in good condition and charging as it should. His comment was that what I was experiencing was normal. His advice was that for every hour that the house battery was used it would take about an hour driving to replace that charge when only charging from the vehicle's alternator.

Therefore, if one stopped at 4pm, used lights etc until 10pm, then it would take at least four hours of driving to restore the battery to 'full' charge. Therefore, if driving for less than four hours per day after a number of days, the battery would be lower and lower each night - ultimately to where it was too low to support the lights etc.

I stress I have no way of knowing if this advice was valid. However, I found that I needed to run the generator on the fourth/fifth night if just travelling and doing short driving days.

It is at this point, that those with more knowledge than I, join in and show that I was naive to believe the auto elec as he was talking through his proverbial.

PS - I have not had any problems with battery SOC since installing my solar system some four years ago. The solar keeps it all ticking along great unless I get stuck with more than three days of actual rain ... it seems if overcast only, the panels put charge in - but those back-to-back rainy days don't help. The generator sits in the back of the Landy gathering road dust and cobwebs - but I keep carrying it ... just in case.

Cheers - John

mr glassies · Guru

I have a 2012 Colorado in the van I have a 30 amp doc/doc charger . When I do a hookup I usually leave the motor running and sometimes check the victron . And sometimes it showes 38 amps . Ok so some of that is from the solar but most from the car alternator . Just saying .
Dibs

Ron-D · Guru

When you start the car it draws power from the car battery not the van battery ,there's no second battery in our Tug,but I do have a 12 volt to 12 Volt charger in the van,when the last agm battery died ,we had no power at all,the car alternator fed every thing nicely at the time,so hense to me it makes sense that it could replenish some load too the van battery,how much twenty minutes running would put back into the battery I have no idea ,but I want to find out,maybe it is the answer as our load over night comes down to the 12 volt Tv as our biggest current draw so we're not big power users ,that has to be factored in as well......

rockylizard · Guru

Gday...

AHA SEE ... I knew those wot knew more'n me would sort me out. That is the answer I guess.

I don't have a DC-DC charger between the alternator, aux battery, and van/house battery ... so it is just the alternator doing all the hard yakka via the main thru aux then anderson plug direct to my house/van battery. hmm

I did pose the question that to charge direct from the alternator - ie idling the vehicle for "20 minutes" ... would need "To charge beyond the main requires 'additional' devices - eg DC-DC charger, charge controller etc"

Thanks for confirming my system is quite probably outdated ... hasn't altered in nine years.

Cheers - John

macka17 · Guru

WHoops just looked at keyboard strokes...

With a decent size engine. fit second H\D alternator direct to battery. switchable on dash.
We used ""them and shaft alternators"" on yachts to do same thing.

BUT. NO sun. NO travel.
Genny it is. or LED strip lights off small (wing) battery, and watch movies on Tablet.

I often do, out fishing in ute. roll out and mattress.
Small single gas stove. Shovel for?. and water bottle.
Tarp over boat if wet..

-- Edited by macka17 on Friday 13th of October 2017 08:32:10 AM

Peter_n_Margaret · Guru

The alternator on the OKA is our back up charge system if the solar can not keep up (which is rare). It is an "old" style alternator with an output of 85A at 14.3V.
It is a direct connection to the house batteries and will put 70A into the house batteries if they are low. That tapers off as the house batteries come up. This is effective at the same time as the solar and I have seen 70A from the alternator and 30A from the solar going in at the same time. There is no need for a second alternator. It takes more than 20 minutes to get any worthwhile input, but while mobile it is a useful technique.
We don't carry a generator, EVER, and have no 240V input capability. We almost always camp in the bush.

Cheers,
Peter

Tony Bev · Guru

I suppose that there are many different types of charging systems available, and many different sizes, and types of batteries

I am not an Auto Electrician so only have experience of my own system, and will assume that the OP's brother in law, has a much better system

I have a DC/DC charger of 20 amps, which can charge the leisure/house batteries using both solar or engine alternator, as the incoming power
My batteries are 2 x 120 AH AGM

My assumption, so I could be wrong, is...

If there is no sun for a few days, I can start the engine and charge the leisure/house batteries at a maximum of 20 amps per hour
If I have run down my leisure/house batteries by 50%, then it would take me (without calculating any taper off, of the charge), approximately 6 hours to top up my batteries (20 amps x 6 hours = 120 AH)
As the leisure/house batteries starts charging up, the amps going into it would start tapering off, so it would take much longer than 6 hours to fully charge my batteries
If my leisure/house batteries were 50% down, and I ran my engine for twenty minutes, I would put in (theoretically), between 6 and 7 amp hours, which is less than 3% of my total battery power
On a good day this 6.6 amp hours, will give me enough power for about another 5 hours, but the boss could use up that amount of power in less than ninety minutes

Jaahn · Guru

Tony Bev wrote:
I suppose that there are many different types of charging systems available, and many different sizes, and types of batteries

I am not an Auto Electrician so only have experience of my own system, and will assume that the OP's brother in law, has a much better system

I have a DC/DC charger of 20 amps, which can charge the leisure/house batteries using both solar or engine alternator, as the incoming power
My batteries are 2 x 120 AH AGM

My assumption, so I could be wrong, is...
If there is no sun for a few days, I can start the engine and charge the leisure/house batteries at a maximum of 20 amps per hour
If I have run down my leisure/house batteries by 50%, then it would take me (without calculating any taper off, of the charge), approximately 6 hours to top up my batteries (20 amps x 6 hours = 120 AH)
As the leisure/house batteries starts charging up, the amps going into it would start tapering off, so it would take much longer than 6 hours to fully charge my batteries
If my leisure/house batteries were 50% down, and I ran my engine for twenty minutes, I would put in (theoretically), between 6 and 7 amp hours, which is less than 3% of my total battery power
On a good day this 6.6 amp hours, will give me enough power for about another 5 hours, but the boss could use up that amount of power in less than ninety minutes

Hi Tony smile

By your avatar you have a Sprinter, and I too have a Sprinter 312D. I doubt yours' has a dumb "smart alternator".

What you say is correct about charging your batteries with the alternator and the max is 20 amps as set by the DC/DC charger. That is a major limitation IMHO as you have shown and un-necessary if you do not have the dumb "smart alternator".

In my MH I use an automatic relay VCR which automatically switches the charging to the house batteries as well as the car battery after a few minutes of recharging the car battery to a minimum voltage after starting. Then soon the whole output from the from the 120A alternator can go to the house batteries. Actually not that much does but without an exact figure it will mostly charge up my 150AH battery in an hour or so from around 50%. confuse

The solar has it's own regulator so usually that does the charging and/or the alternator which automatically switches on if driving. Been doing that for a few years and thousands of ks and works OK. Better than the straight relay on my last MH, switched by the ignition directly after starting. If there is poor sun or rain I have occasionally used the motor to top-up a bit if we are not going anywhere. I watch the voltages and do what ever is needed. Switch things on when the sun is out, chargers etc, use less power if things are low. Now there's a thought biggrin

Jaahn

Tony Bev · Guru

Jaahn wrote:
Tony Bev wrote:
I suppose that there are many different types of charging systems available, and many different sizes, and types of batteries

I am not an Auto Electrician so only have experience of my own system, and will assume that the OP's brother in law, has a much better system

I have a DC/DC charger of 20 amps, which can charge the leisure/house batteries using both solar or engine alternator, as the incoming power
My batteries are 2 x 120 AH AGM

My assumption, so I could be wrong, is...
If there is no sun for a few days, I can start the engine and charge the leisure/house batteries at a maximum of 20 amps per hour
If I have run down my leisure/house batteries by 50%, then it would take me (without calculating any taper off, of the charge), approximately 6 hours to top up my batteries (20 amps x 6 hours = 120 AH)
As the leisure/house batteries starts charging up, the amps going into it would start tapering off, so it would take much longer than 6 hours to fully charge my batteries
If my leisure/house batteries were 50% down, and I ran my engine for twenty minutes, I would put in (theoretically), between 6 and 7 amp hours, which is less than 3% of my total battery power
On a good day this 6.6 amp hours, will give me enough power for about another 5 hours, but the boss could use up that amount of power in less than ninety minutes
Hi Tony
By your avatar you have a Sprinter, and I too have a Sprinter 312D. I doubt yours' has a dumb "smart alternator".
What you say is correct about charging your batteries with the alternator and the max is 20 amps as set by the DC/DC charger. That is a major limitation IMHO as you have shown and un-necessary if you do not have the dumb "smart alternator".
In my MH I use an automatic relay VCR which automatically switches the charging to the house batteries as well as the car battery after a few minutes of recharging the car battery to a minimum voltage after starting. Then soon the whole output from the from the 120A alternator can go to the house batteries. Actually not that much does but without an exact figure it will mostly charge up my 150AH battery in an hour or so from around 50%.
The solar has it's own regulator so usually that does the charging and/or the alternator which automatically switches on if driving. Been doing that for a few years and thousands of ks and works OK. Better than the straight relay on my last MH, switched by the ignition directly after starting. If there is poor sun or rain I have occasionally used the motor to top-up a bit if we are not going anywhere. I watch the voltages and do what ever is needed. Switch things on when the sun is out, chargers etc, use less power if things are low. Now there's a thought
Jaahn

Hope that I am not hijacking your thread RonD

Thanks for that information Jahhn, it is appreciated, and something I shall have to look into, if my present system ever fails

My vehicle is a 2006 Fiat Ducato, (they changed the model in 2007)
To the best of my knowledge it is not a smart type alternator

The original charging of the leisure battery, went through a SETEC ST 11 charger, a standard fitting by Jayco
I found it to be hopeless, and lost the original leisure battery, due to always taking out, more than went in
I suppose that I had believed the salesman type talk, that my leisure battery would be charges on 240 volt, and when the engine was running

A link to your automatic relay VCR, would be appreciated

I did read somewhere that the Europeans were going away from carrying generators, and just starting their vehicle engine to charge their leisure batteries
I always wondered exactly how they did it

Jaahn · Guru

Tony Wrote,
Hope that I am not hijacking your thread RonD

Thanks for that information Jahhn, it is appreciated, and something I shall have to look into, if my present system ever fails

My vehicle is a 2006 Fiat Ducato, (they changed the model in 2007)
To the best of my knowledge it is not a smart type alternator

The original charging of the leisure battery, went through a SETEC ST 11 charger, a standard fitting by Jayco
I found it to be hopeless, and lost the original leisure battery, due to always taking out, more than went in
I suppose that I had believed the salesman type talk, that my leisure battery would be charges on 240 volt, and when the engine was running
A link to your automatic relay VCR, would be appreciated
I did read somewhere that the Europeans were going away from carrying generators, and just starting their vehicle engine to charge their leisure batteries
I always wondered exactly how they did it

Tony smile

I bought one of these and have recommended them to some others. However I actually use another simpler one way VSR that I purchased earlier before I saw this better one. I am 'gunna' swap it over one day as I like the manual switch to connect the batteries together in case the vehicle battery dies for some reason hmm But it has never happened yet.

http://www.ebay.com.au/itm/12V-140-Amp-VSR-Dual-Battery-Isolator-Voltage-Sensitive-Relay-4x4-Camper-Camping-/252477455461?hash=item3ac8d43c65:g:LSYAAOSwgwxZbu7e

You can check if your Fiat has a dumb alternator by looking at the voltage after it starts and for some time. If the voltage gets up to 14.2+ and stays there for ever then it will be OK. If it drops down to some much lower voltage after a while and stays down there it will not. Do not use it for gel cells as they usually need a bit lower voltage than normal LA or AGM batteries. If the voltage is very much higher then check it out.

Jaahn

PS I see it is actually referred to as a VSR ! Sorry i will self flagellate !

-- Edited by Jaahn on Sunday 15th of October 2017 04:37:24 PM

Dick0 · Guru

A generator can be handy. Firstly, to keep the good lady happy, and a happy lady makes a happy camper.

Secondly, if you enjoy an espresso/latte, or heating/reheating quickly by microwave oven and not sweltering in the summer heat, the genie is the go.

And like Dougwe says...running the genie at 2.00am is the best time as everyone is asleep.

smile biggrin confuse

Tony Bev · Guru

Thanks for the link, Jaahn

I shall keep it for future reference

swamp · Senior Member

hi Ron -D

Out of an AGM u can only use 50% of the AH

Best advice is for every 100-120ah battery ---usable 50% =50-60ah
160watt solar borderline harvests 38ah approx. in 24hr
200watts solar is the best at absolute min harvests 48ah approx. in 24hr

Good amounts of solar will reduce reliance on charging via car/gene etc

rockylizard · Guru

Ron-D wrote:
speaking to the brother inlaw yesterday about power use while free camping, when there's not enough sun to top up the batteries.
we dont carry generators it's not the way we like to camp,if his batteries are running low and there's not a lot of sun,he hooks the car up and runs it for twenty minutes that usually brings the battery right up,it's needed only rarely,it's not overly noisey,you don't have to carry smelly fuel cans,find a space for a heavy generator,our power usage is only Leds ,Tv,fridge on gas,cooker on gas,twenty minutes with a car on idle on rare occasions makes sense to me anyway...

Gday...

Given the comments and advice on this thread, it seems this is quite possible if one has a DC DC charger in the circuit between the vehicle's alternator and the van battery to recharge the battery.

OK - so I am now throwing myself to the mercy of the wolves hmm ... if that is the case - if the van battery is "running low" on days of "not a lot of sun" then the running of a vehicle's alternator for 20 minutes will "bring the battery right up".

Perhaps someone could quantify just what "running low" and "right up" might mean.

If that means a battery that is even only down to 85% SOC and there is "not a lot of sun" then 20 minutes of idling the vehicle will bring the battery to (at least?) 95%.??

If that is the case, then why on earth do we all waste our money on so many watts of solar panels. cry confuse

I again stress, I quite probably have insufficient nouse/knowledge of any thing electrical ... but can someone enlighten me. (gently )

Cheers - John

-- Edited by rockylizard on Thursday 19th of October 2017 06:54:40 PM

markf · Senior Member

swamp wrote:
hi Ron -D

Out of an AGM u can only use 50% of the AH

Best advice is for every 100-120ah battery ---usable 50% =50-60ah
160watt solar borderline harvests 38ah approx. in 24hr
200watts solar is the best at absolute min harvests 48ah approx. in 24hr

Good amounts of solar will reduce reliance on charging via car/gene etc

I have a trio of 100Ah AGM's. Two in the camper and one in the car. They are all over five years old and still exhibit good capacity. I've NEVER been afraid to discharge them to below 12.0V and sometimes below 11.5V. They NEVER get left in that state for more than a couple of hours before charging starts and they don't get discharged to that level every time - usually only down to about 12.2V or so.

They key is to not discharge to below 50 or 60% regularly and if you do charge them promptly.

Jaahn · Guru

rockylizard wrote:
Ron-D wrote:
speaking to the brother inlaw yesterday about power use while free camping, when there's not enough sun to top up the batteries.
we dont carry generators it's not the way we like to camp,if his batteries are running low and there's not a lot of sun,he hooks the car up and runs it for twenty minutes that usually brings the battery right up,it's needed only rarely,it's not overly noisey,you don't have to carry smelly fuel cans,find a space for a heavy generator,our power usage is only Leds ,Tv,fridge on gas,cooker on gas,twenty minutes with a car on idle on rare occasions makes sense to me anyway...
Gday...
Given the comments and advice on this thread, it seems this is quite possible if one has a DC DC charger in the circuit between the vehicle's alternator and the van battery to recharge the battery.
OK - so I am now throwing myself to the mercy of the wolves ... if that is the case - if the van battery is "running low" on days of "not a lot of sun" then the running of a vehicle's alternator for 20 minutes will "bring the battery right up".
Perhaps someone could quantify just what "running low" and "right up" might mean.
If that means a battery that is even only down to 85% SOC and there is "not a lot of sun" then 20 minutes of idling the vehicle will bring the battery to (at least?) 95%.??
If that is the case, then why on earth do we all waste our money on so many watts of solar panels.
I again stress, I quite probably have insufficient nouse/knowledge of any thing electrical ... but can someone enlighten me. (gently )
Cheers - John
__________________________________________________________________________________________________________________________

Hi John smile

Short answer NO ! You cannot recharge a low battery to fullish in 20 minutes using a dc-dc charger of normal size. hmm Nothing close to that really !

I thought the discussion above said clearly that using an old type dumb alternator will be the best way and will take longer than 20 minutes also, even though it can charge at 3 to 5 times the rate of a normal dc-dc charger. A somewhat faster speed than idle is usually needed too.

If you have a new "smart alternator" then you need another strategy. There was good information in this article that was pasted up yesterday in another thread on the subject. https://outbackjoe.com/macho-divertissement/macho-articles/design-guide-for-12v-systems-dual-batteries-solar-panels-and-inverters/

To discuss what is considered "running low" and "bringing it right up" is a bit too general, as is the variation of the battery sizes, to make any more discussion useful IMHO. Reread the previous discussion and that article is my suggestion. aww

Jaahn

PS it is worth saying that if you want to charge at 80+ amps you need heavy wiring and for both + & - connections. Not just a couple of light wires that will dissipate all the power in heat and melt the insulation and cause a fire. furious A long way to the back then even heavier wires and a bigger anderson plug than a 50A.

-- Edited by Jaahn on Thursday 19th of October 2017 08:21:02 PM

swamp · Senior Member

an hi
markf
Missed the point
yea people do discharge lower than 50% on occasion
BUT MOST DONOT have enough solar to recover them in a 1/2 day which is just as important . Benefits are as u described recharging in a timely fashion which inturn preserves battery life .

I highly recommend a LVD low volt disconnect that's programmable with an alarm and a by pass switch .

-- Edited by swamp on Saturday 21st of October 2017 02:30:00 AM

macka17 · Guru

hi Swamp.
If you living with it.

just check amp and Voltage of battery bank at dawn for a coupla days .
the readings then will tell you if you have enough battery power to run your system
WITHOUT draining it too low. I prefer Analog gauges.

Count figures and make sure you have enough panels to recharge (on average)
by around 11.am ish. Then add another panel. To cover cloud cover mainly.

Plus. Most sensibles also carry a genny with decent AC charger too. (Air Cond.Tools.drills etc, etc)

I ran 345w panels with 1 x 100\1 x 110AGM's. Plus another 85w panel on top of ute
to add more if necessary 400w would be betterer.