Charging for Dummies

Paul and Pam on Tour · Veteran Member

Charging for Dummies

Gundog · Guru

The easiest and cheapest solution is to have the smart alternator, smart feature thus enabling the alternator to send plenty of charge to the caravan battery

Otherwise a good DC DC charger is the other option.

thomas01 · Senior Member

Hi Paul and Pam,

I think what Gundog meant to say was to have the "smart alternator" function of your car turned off by the dealer, if possible. That will enable the alternator to provide higher charging voltage to your van when driving.
Gundog, please correct me if I got that wrong.

The other reasonably priced option is to install a DC-DC charger as Gundog has already mentioned. They are not that expensive if you stay clear of the overpriced "Name Brands". Read some on-line reviews of the cheaper options and choose one with a reasonable rating. Just make sure it is Lithium compatible.

The other option is to upgrade the capacity of your battery if possible, but that would probably mean you would need to increase your solar as well.

Welcome back.

Big Mal · Senior Member

Plenty of watts on roof and storage is the best way and with a lithium and a tug with a smart alternator best to use a DC/DC charger in tug or van saves a lot of problems ..

For over 10 years I have just relied on solar as no charge system from tug, never got around to it then didn't bother as not needed but plenty of watts on roof and storage along with a 120w portable to get the early and late rays................... Genny for emergency but again not needed, yet.............. lots of cloudy days I watch the power draw and make sure the TV and Foxtel box are off when not used, they can burn a lot of juice.

I would add a DC/DC charger to van then can plug in any vehicle that has an anderson or a genny on 12v to top up battery............. especially if it has solar input you can hang a portable panel off it as well......................... its been on my list for a few years now, one day............ I run 420w on roof, 120w portable and an Epever reg which does a brilliant job even in the rain, its a proper MPPT unit not a fake like many..

Radar · Guru

Hi Paul

Congratulations on enjoying your Jaco caravan over that period of time,

We run 320 watts of roof tops solar for charging our 200 amps deep cycle batteries for last 7 years but now 4 months ago we fitted a 120 amp lithium battery from a electrical parts store.

The expensive 12 volt charger lives in the garage, I can via a Anderson plug connect to the car but have no need to as yet with the battery performing well.

If I had known I would have purchased a solar controller with a built in dctodc charger suitable for when I need to charge the lithium, unfortunately the store that sold the battery and the solar controller did not offer that option.

240 volt 25 amp Lithium battery chargers cost about $170 and I have seen lower then this on special.

Plug into the car is a pretty good option.

Paul and Pam on Tour · Veteran Member

Thanks guys for the quick replies, gives me stuff to think about.
Gundog and Thomas 01, your answers intrigue me...do I take it that I can connect directly from my alternator to my caravan battery via the Redarc isolator, with no need for a DC to DC. But before doing this it needs a setting change by the dealer?.

As said my aim is to be able to stick some quick charge into the van battery when stationary to enable 'lights on' not so much to charge it when driving, if needs be we can always pop into a showground or so and use shore power to recahange. .....we do have a B & S 1.2 KVA genny but they are about as popular in many camps as a Greenie Convention would be.

Thanks again.

-- Edited by Paul and Pam on Tour on Thursday 22nd of August 2024 08:25:32 PM

-- Edited by Paul and Pam on Tour on Thursday 22nd of August 2024 08:26:43 PM

-- Edited by Paul and Pam on Tour on Thursday 22nd of August 2024 08:27:04 PM

Big Mal · Senior Member

A direct connection between the tug battery and your van battery is a No, No, the charging regimes of the tug and a lithium are not compatible at all and will not fully charge the lithium and possibly destroy it.... ................ power must go via a charging unit for lithiums...... Calcium, AGM and GEL charging units are not any good..

What BMS unit is fitted in the van to charge your lithium from solar some have a AUX input to charge from tug or other 12v input ....

Do you have power feeding your fridge as you drive ??? if so this supply is then by-passing your smart alternator and would be ideal to use for charging.

Peter_n_Margaret · Senior Member

Big Mal, do you actually have any experience with the stuff you are giving advice on or are you just repeating the rubbish from other forums?
For many years I have charged my AGM house batteries directly from the (non smart) alternator.
I have recently changed the house batteries to 320Ah of CALB prismatic LiFeO4 with 250A Daly BMS and am doing exactly the same with them.
A typical (non smart) alternator outputs about 14.2V which is an ideal Li charge voltage. Mine is actually closer to 14.4V which is fine too.
Cheers,
Peter

Radar · Guru

It is interesting reading about lithium batteries and the way to use them successfully.

I do not have any technical qualifications.

We charge our lithium battery via solar only but if the unthinkable happens and the world iced over, our battery was getting low and we needed more battery amps, I would hook up to that loose Anderson plug start my car motor and charge the battery. Half hour of charging would get us the night.

I would guess it might shorten the overall performance of the battery by hour each time I exercise this over a period of 5 years. At around 160 nights a year in the caravan for last 7 years never needing to charge the battery.

What did we do before smart this and smart that?

Peter_n_Margaret · Senior Member

Radar wrote:
I would guess it might shorten the overall performance of the battery by hour each time I exercise this over a period of 5 years.

Can you explain to me why it would do that?

Cheers,

Peter

Whenarewethere · Guru

Make sure the DC-DC charger is near batteries.

Also calculate wire resistance for the total length or both + & - No point throwing way valuable resources in heat lost in wire resistance.

You do actually need the DC-DC charger near the batteries for "more" correct charging voltage on this subject alone.

If keen you could add a temperature sensor on the batteries to adjust charging voltage.

If you need to solder heavy wire into a Anderson plug, a heat gun works a treat for easily 350 amp plugs. Drill a hole in a block of wood & stand up Anderson lug.

6awg lug with 4awg cable for longer runs:

https://thegreynomads.activeboard.com/t65662065/50amp-anderson-plug-expand-for-4-awg-cable/

P.S. 175 amp Anderson plugs are much smoother to plug/unplug than 50 amp plugs.

P.P.S. 50 amp plugs are 120 amps cold plugging. 175 amp plugs are 280 amps cold plugging (open circuit).

Radar · Guru

Peter_n_Margaret wrote:
Radar wrote:
I would guess it might shorten the overall performance of the battery by hour each time I exercise this over a period of 5 years.
Can you explain to me why it would do that?
Cheers,
Peter

Just things you read perhaps.

Really I don't have any idea but I have copied a bit of serving by a couple of train auto elects saying you need this and that in my battery system, you will need to charge the battery once a month, don't you have a shunt, things like that.

Scubadoo · Veteran Member

We sure are often led astray by Google, sales folk and the occasional forum poster into believing how complex and fragile LiFePO4 battery setups are when in practice it is all quite simple and straightforward.
Add as much complexity as you like but most of it is unnecessary.
Batteries with inbuilt quality BMS devices will protect the cells from most potential abuse.
C r a p batteries or components and you are on your own. No one else will care.

Add a DC-DC charger by all means if you actually need one or have money to burn.

As Peter mentioned a "non smart" alternator with an output of 14.0 - 14.50V will fully charge a LiFePO4 battery safely with ease given appropriate cable sizing and time.

The only qualifier being that any inbuilt BMS circuitry can handle the resulting charge rate.

As I have mentioned on this forum more than once that our Mitsubishi Canter truck 100A rated alternator has direct charged the 4 cell 300Ah LiFePO4 battery at 70-80A while driving for the last 10 years of full-time travel without releasing too much of its smoke reserves - yet.

The same battery has also started the Canter 3.9l turbo diesel engine perhaps a thousand or two times over the years.
No DC-DC charger, usual BMS or regular cell balancing involved nor has it ever proved necessary.

-- Edited by Scubadoo on Friday 23rd of August 2024 03:10:34 PM

Peter_n_Margaret · Senior Member

Some of the so called "experts" are the worst offenders when it comes to misinformation.
One of the differences between AGMs and LiFePO4 is that lithiums do not require to be regularly brought up to full charge which is the best treatment for AGMs.

The shunt thing is because it is difficult to know what the accurate state of charge of a lithium battery is unless you constantly count the energy in and the energy out. Unlike lead acid batteries, the voltage of lithiums does not change a lot between nearly full and nearly empty.
Cheers,
Peter

Peter_n_Margaret · Senior Member

Scubadoo wrote:

The same battery has also started the Canter 3.9l turbo diesel engine perhaps a thousand or two times over the years.
No DC-DC charger, usual BMS or regular cell balancing involved nor has it ever proved necessary.
______________________________________________________________________________________________________________________________________

As a ps....

I am building a new "light weight" OKA motorhome currently.

For many years I have been using AGMs as crank batteries in the current OKA because they are resistant to being wrecked by corrugations that quickly kill wet cell batteries by shaking them apart on the inside.

As a trial for the new vehicle, I fitted a prismatic cell lithium crank battery just before Christmas. The AGM that I took out was 125Ah and weighed 36kgs. The Lithium crank is 30Ah, 880CCA and weighs 4.5kg. It turns the OKA over better than the AGM, particularly when it is very cold.

We have recently completed the southern end of the Canning Stock Route without incident, so the "trial" is going well :)

Cheers,

Peter

Dick0 · Guru

I would lean towards caution charging in this manner after watching this video.

This "expert" actually performed relevant tests to substantiate caution.

Lithium to Alternator Direct Charge Test : Why current limiting is vital - YouTube

Peter_n_Margaret · Senior Member

No problem with "caution".
Charles Stirling manufactures and sells DC-DC chargers.
What he says to me is don't buy a cheap Chinese or Indian alternator.
Cheers,
Peter

Paul and Pam on Tour · Veteran Member

To everyone responding to my posting...thanks, be advised that I now have sufficient information and the subject is now closed.

Regards
Paul

Big Mal · Senior Member

Peter_n_Margaret wrote:
Big Mal, do you actually have any experience with the stuff you are giving advice on or are you just repeating the rubbish from other forums?

Peter

Yes I have and I still wouldn't advise for anyone to direct charge their lithiums from a tugs alternator, the variations in alternators and their operating conditions requires careful consideration in each case along with the specs of the battery and to say to people go ahead without such consideration can be misleading .................... I do agree there is a lot of rubbish on forums , this one included.

Dick0 · Guru

Big Mal wrote:
Peter_n_Margaret wrote:
Big Mal, do you actually have any experience with the stuff you are giving advice on or are you just repeating the rubbish from other forums?

Peter
Yes I have and I still wouldn't advise for anyone to direct charge their lithiums from a tugs alternator, the variations in alternators and their operating conditions requires careful consideration in each case along with the specs of the battery and to say to people go ahead without such consideration can be misleading .................... I do agree there is a lot of rubbish on forums , this one included.

Yes agreed Ian, I would lean towards caution charging LiFePO4 batteries in this manner and would seek research about this elsewhere.