What size charger can I use?

Stevejaz · Member

What size charger can I use?

Tony Bev · Guru

Hi Stevejaz

I am not a techie, and hope that if what I say is wrong, then someone will come along and correct it

I have a 2006 Jayco Conquest

I can confirm that its Jayco built in 240 volt battery charger, only appears to be a trickle charger, and not suited to actually charge batteries
My bookwork says something like.
"Before a long trip, put the charger on, for a number of days, to ensure the battery is fully charged."
Or words to that effect

I have read, but have no way of knowing if it is correct, that normal lead acid batteries, like to be charged at 10% of their capacity
Therefore you should be able to charge your batteries at 24 amps

I have read that even if you have a larger battery charger, say a 40 Amp, the battery will only accept, what it wants

I have read that some 240 volt battery chargers, will not work when run by a genset

I have 300 watts of solar on the roof, plus 160 watt portable panel for overcast days

I use a 20 amp CTEK DC/DC charger, which charges the 2 X 120 AH house batteries, from solar and/or engine

I can not advise on a 240 volt battery charger, but I can say that on my last road trip, I had an expensive (to me) PROJECTA 15 amp battery charger, with power supply mode
I was using it on power supply mode, and it failed. It was well out of warranty at nearly five years old.

Hope that this info is useful to you

Peter_n_Margaret · Guru

The maximum amps of a charger needs to be dependent on the voltage that the charger offers as well.
For instance, your alternator might offer 100A to your start battery and that is no problem because the alternator is only 14.3V. In this case, the battery's internal resistance will determine and control the charge rate to safe levels.
If the voltage is larger, the charge rate will also be larger, from the same alternator (charger).

So, in general terms, provided the charger is an appropriate voltage for the battery type, the bigger it is the better. Most decent ones will be like this.
Cheers,
Peter

DeBe · Guru

His 2.6KVA Kipor gen is a pure sine wave inverter generator, as I have one so pretty mutch any battery charger will be happy with that.

Whenarewethere · Guru

I have a Victron 10 amp charger with Bluetooth data on the phone. Mainly use it to top up the car's 85ah or auxiliary batteries 4 x 26ah while sitting in the garage. It reduces the current as required.

I have Victron MPPT & DC-DC, so far so good.

Bagmaker · Senior Member

check your batteries for the "C" rating, that will tell you the maximum charge rate
Also, consider if you want to upgrade your battery, will your new charger suit?
Most quality chargers have adjustable settings for the voltage and output, if you are going to get more amp hours or lithium, be sure to buy a charger that will do both.
Projector IC series is very good, IMHO

kgarnett · Senior Member

If for instance the max recommended charge rate was 20A for your battery, then you could charge at 40A for the 2 batteries in parallel assuming roughly equal charge current to each battery.

Ken

Jaahn · Guru

Stevejaz wrote:
Hi Folks
----
Solar panels, 2x 80 watt roof mounted along with a 200 watt fold out mobile one.
Batteries, 2x 120amp hour
Built in charger ( as far as I can figure) maybe 5 amps at best.
I had thought the Max charge rate I could use would be 20 amps but see there a 40 amp and faster (50, 60 etc) I want to be able to run a generator for a few hours to give the batteries a large boost when needed. Rainy days etc. It IS winter in the south after all.
-------- Don't want to kill the batteries.
T-------

Hi Steve smile

To put some figures on the charging lets do some sums ! If you want to be able to recharge 50% of your battery capacity(max discharge) that would be 120AHrs required . How long do you want to run the genny, 4 hrs then you need 30Amps, 3 hrs running then you need 40Amps, 2 hrs then 60 Amps. These are round figures and not to full charge either. blankstare

SOOOO you need to ask your battery manufacturer if these charging rates are OK for a parallel pair of their batteries and check the connections give equal sharing. Personally I would say 50-60 Amps is OK for 2x AGM probably not for Gel. But ask the people who should know !! hmm

I do not have a 240V charger in my rig so cannot comment on which one to get. I suggest you only have a 5A float unit anyway which I also have for caravan park use. Not really a charger at all.

Jaahn

PS I guess this will p*ss off the genny brigade but spend the money on more solar panels on the roof, at least double what you have or more.

-- Edited by Jaahn on Wednesday 20th of May 2020 07:43:38 PM

swamp · Senior Member

Hi
Ideally 200watts of solar per 100-120ah battery min.
400watts solar replaces approx. 96ah [solar at 100%]
plus bonus solar rays at less than 100% PLUS mppt ,both of these are hard to measure
400watts controller equals 30amp controller
Enerdrive make a 30-40amp unit ,,this incorporates dc2dc charging to ensure arrival at site always charged .

Regards AC240v charge ,some poor quality chargers require a huge generator
1000w gene =25amp charger
2000w gene = 35 amp charger

Some chargers are very very inefficient ,, some are not but cost a lot . This determines gene size .

Many many Jayco fitted chargers are low performance .

-- Edited by swamp on Thursday 21st of May 2020 05:18:44 PM

Stevejaz · Member

Thanks for al the help. I have gone ahead and ordered a (alleged) 60amp charger. Just a cheapie so I would not expect too much from it. Currently trying to understand wire sizes. Gauge vs Diameter etc. As I said the generater is 2.6 KVA so plenty big enough. Given both the A-Van and Motorhome have Andesan plugs, which connect via a DC-DC charger in the A-Van, my plan is to fit a couple of short leads to the two battery outlets on the charger then connect with as short as possible Andersan extension chords. Run it as a stand alone external combo for starters. The whole point is to give a rapid boost rather than a full charge. Figure 1-2 hours is enough for a gennie. I have a total of 520 amp hours storage. 2x140ah in the motorhome and 2x120ah in the A-van. Extra solar panels are really not the solution atm. Have a total of about 600watts. They don't do a lot with extended rain days in winter however. Will probably be back in Adelaide late this week when the charger arrives, giving me time to sort cabling before leaving for Ceduna the end of the following week. I will post my experience with the results then. Could be of interest to others in the same boat. Those of us stuck in a southern winter rather than the Queensland sun.

Whenarewethere · Guru

I have an old downloaded Safari browser calculator which is easy.

How many amps & metres ( + & - ) in other words total length there & back & I can post some options for how much you are prepared to sacrifice.

You may want to swap the cheap Anderson plug copies for originals, there is plenty of rubbish on the market.

swamp · Senior Member

Hi
volt drop is the enemy of battery charging
13mmsq= 6b&s 18amps over 9mtrs gives .4 volt drop
25mmsq = 2b&s 36 amps over 9 mtrs .4 volt drop

If the distance halves the amps double and v/ drop stays the same

Stevejaz · Member

Picked up a metre of heavy wire and a couple of anderson plugs at Jaycar yesterday. Have the charger attempting to revive an old marine battery atm and today will wire up a short patch chord(x2) to try it between the motorhome and Avan. I'm contemplating a hard wired option inside the motorhome as close to the battery box as possible (if not inside) This would enable internal mains connection with the generator plugged in, in the usual way, the Avan connected via the pre-existing cable with anderson plug connection. The hope here is that the DC-DC converter in the Avan battery box will compensate for voltage drop. Also assuming the 2 battery banks, wired in parallel will present the total amp hours to the charger. (520ah). Interested in expert advice on that one. All I know is that the portable, external folding solar panel boosts the voltage in either battery bank when connected to the appropriate anderson plug, where the Avan plugs into the back of the motor home. The charge controllers in both (both PWM) show the voltage but not the current. Initial assumption is that when I plug the 2 outlets of the charger into both, the output current of the charger should be halved with up to 30 amps going to each. I'll try that today.
Yes I have seen charts online which show wire gauge/amperage/length of wire. One thing I want to do is put another anderson plug straight off the battery box in the Avan as the current one, running through the DC-DC charger, does not allow me to use it as a power source. One way only. May do the same on the motorhome, all using the same 6 gauge wire, and then make a couple of stand alone anderson extension leads. All one step at a time atm.
Just one thought on the DC-DC charger in the line between the Battery charger and the Avan batteries. Will that stop the charger from being able to read the voltage in the Avan battery bank?

Stevejaz · Member

Update:
Well after all that it turned out the charger was faulty so it's been sent back. Picked up a Victron 30amp charger at 'Home of 12 Volt' and going back today for a second one. Will just instal one in each vehicle and connect mains power cables via a 15 amp power box to the generator. Twice the price but 5 times the warranty (5 years) plus the phone app so probably the better long term investment.. Also less concern over voltage drop due to cable length. Also a lot more comfortable with charger(s) housed inside.

Whenarewethere · Guru

Alway good having redundancy. Victron gear is a bit more expensive but I would rather do the job once, not worth my time & stress trying to find faults in cheap equipment.

I can use my jumper leads as an option.

Stevejaz · Member

After the first week away with the new chargers I'm more than happy with them. I can run the generator for an hour or less in the morning when camped in a rest area and have batteries back off boost charge, which I think means they are up to about 80%. Solar and/or driving generally deals with the rest. Yet to put it to the test but I figure a couple of hours of generator a day should give us all the power we need on rainy/overcast days if not moving.

Aus-Kiwi · Guru

I have 40 amp charger , with 7 stage smart regulator . Dont use the old style chargers . They WILL overcharge , over heat your batteries . Yes it works off the generator or mains .

-- Edited by Aus-Kiwi on Saturday 18th of July 2020 11:08:46 PM

Hylife · Guru

200ah batts should have 4-500w of solar