ANOTHER battery charging question

I will try to keep my query as short as possible.
Yes I have done a thread search and yes there are heaps of battery questions but!!!
When charging AGM (or any other battery) from multiple sources e.g. car alternator, solar panels and 240v supplied "smartcharger" do you have to isolate each supply when using another or can you use say solar and car alternator together or does the higher voltage tell each supply that the battery has a higher charge than it does in reality????
I have recently got hold of an 85 w solar panel and would like to buy an MPPT controller to fit to the vehicle. The car has 2x N70 cranking and 1x 100ah AGM.
I tow a van with 2x 100ah AGM's and when in a CP I leave the Anderson plug connected to the car so that I can keep the 40l Engle running in the car without drawing too much from the AGM in the car. The AGM in the car has a VSR, Matson brand to isolate the crankers when stopped.
I hope my ramblings make some sense.
Thanks in advance.

Cheers
Pop
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Reply By: Member - Joe n Mel n kids (FNQ - Tuesday, Sep 18, 2012 at 12:34

Tuesday, Sep 18, 2012 at 12:34
glad you have asked the question as i have had a crack at looking it up but just so much info out there i got a headach and gave up .....
So come on all you wise ones ..
Cheers
Joe
AnswerID: 495150

Follow Up By: pop2jocem - Tuesday, Sep 18, 2012 at 15:30

Tuesday, Sep 18, 2012 at 15:30
Know what you mean Joe. I gave up when my vastly depleted brain cell collection started to implode and decided to be the dummy and ask (;-))
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FollowupID: 770827

Reply By: Peter_n_Margaret - Tuesday, Sep 18, 2012 at 12:40

Tuesday, Sep 18, 2012 at 12:40
I have heard about some chargers which get "confused" with multiple charge sources, but mine and most seem quite OK to accept solar plus alternator direct at the same time. In fact I get both charge potentials added together although the alternator charge rate drops off as the battery voltage comes up.

Cheers,
Peter
OKA196 Motorhome
AnswerID: 495151

Follow Up By: Bigfish - Tuesday, Sep 18, 2012 at 13:18

Tuesday, Sep 18, 2012 at 13:18
I have been running alternator and solar panels on car roof for about 10 years. Absolutely no problems at all.
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FollowupID: 770813

Follow Up By: Ross M - Tuesday, Sep 18, 2012 at 14:46

Tuesday, Sep 18, 2012 at 14:46
Same here Bigfish. The solar is connected to the aux batteries and if and when required, usually travelling and on cloudy days Is switch the car/alt system to it too. Never a problem, never had a flat battery with this use.
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FollowupID: 770819

Follow Up By: pop2jocem - Tuesday, Sep 18, 2012 at 15:25

Tuesday, Sep 18, 2012 at 15:25
Bigfish and Ross,

So if I interpret what you have written correctly you guys just leave the solar on permanently and when the car is running it supplements the charge into the batteries without disconnecting the solar??? Or have I got that all wrong (:-))
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FollowupID: 770825

Follow Up By: pop2jocem - Tuesday, Sep 18, 2012 at 15:27

Tuesday, Sep 18, 2012 at 15:27
Sorry Peter, meant to include you in the question
Oh for an edit function(;-((
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FollowupID: 770826

Follow Up By: Bigfish - Tuesday, Sep 18, 2012 at 17:37

Tuesday, Sep 18, 2012 at 17:37
Mate I have 3 x 80 watt panels on my troopies roof. I have a 20 amp STC regulator from the panels that feeds the auxillary battery. The auxillary battery has 2 leads that then feed 3 X 100 amp/hour i-river batteries. I use a redarc battery isolater between the main and auxillary battery. As stated this has worked for many years, is simple and why alter something that works well?
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FollowupID: 770842

Reply By: Dennis Ellery - Tuesday, Sep 18, 2012 at 15:00

Tuesday, Sep 18, 2012 at 15:00
Some will work in parallel whilst others will get confused.
I have three 40 amp dumb chargers that work well together and will produce 120 amps when connected in parallel.
On my caravan I have a 15 amp smart charger connected in parallel with a 20 amp smart solar panel regulator. One is a 3 stage and the other a 5 stage with different algorithms – no damage done but one tends to take over as they sense each other’s voltage and get confused about the batteries state of charge.
AnswerID: 495164

Follow Up By: pop2jocem - Tuesday, Sep 18, 2012 at 15:20

Tuesday, Sep 18, 2012 at 15:20
Dennis,

That's the sort of situation I was concerned about, one or both getting "confused"and one of them, or worse both spitting the dummy. I wasn't sure if you had to isolate either when the other one was in use. I was concerned that as battery voltage started to rise the chargers may interpret that as a completed charge cycle and stop or at very least go prematurely into float. Even though there are 3 potential charge sources in practice only 2 would in what ever combination would be active.

Cheers
Pop
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FollowupID: 770824

Follow Up By: Dennis Ellery - Tuesday, Sep 18, 2012 at 15:50

Tuesday, Sep 18, 2012 at 15:50
Hi pop2jocem’
I have had 2 situations in the past
1) A smart solar panel regulator connected to a dumb alternator in my 2008 model Troopy.
2) And I have the other connection, I mentioned in the post above, on my caravan.
In both situations no damage is done and in each case the batteries get charged but the caravan charger senses activity on the battery before it goes into the 4 and 5th stages – no big drama, but it won’t float at the time or voltage set by its algorithm when the solar panel is competeing with it.
On an unrelated matter - In another situation I fed a solar panel bank into 2 separate and identical smart regulators, one on the 4WD batteries and one on the caravans batteries and they shared the load without bother – feeding more into which every battery had the greatest need.
I don't think that you can damage your chargers by parralleling them up - but don't hold me to that as its not possible to know them all.
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FollowupID: 770829

Follow Up By: Dennis Ellery - Tuesday, Sep 18, 2012 at 15:54

Tuesday, Sep 18, 2012 at 15:54
opps “which every” battery should read “whichever”
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FollowupID: 770830

Reply By: Sand Man (SA) - Tuesday, Sep 18, 2012 at 18:33

Tuesday, Sep 18, 2012 at 18:33
Pop,

Here's the method I use.
I have a Ctek D250S dual charger in the camper.
It has two input ports.
1. Alternator input
2. Solar input

If you are using a fixed solar panel on the roof of the camper and plugged into the solar inport port and also have the alterator input circuit connected, the D250S will determine the best source and use the one it considers best. In other words you can have both alternator and solar inputs to the dc-dc charger at the same time while driving, or with engine running.

A 240v charger is connected directly to the terminals of the battery bank and doesn't go through the dc-dc charger. When using the 240v charger simply disconnect the feeds to the other two circuits by removing the connection plugs.

I don't actually use the solar panels when driving. They are a bi-fold arrangement and I employ them when stationary at camp. However, should I leave the alternator circuit connected and happen to start the engine, again the D250S will determine the best source and use that.

Bill


I'm diagonally parked in a parallel Universe!

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AnswerID: 495177

Reply By: pop2jocem - Tuesday, Sep 18, 2012 at 19:58

Tuesday, Sep 18, 2012 at 19:58
OK thanks for your help guys. It sounds like most of you do not have a problem with leaving 2 charging sources connected at the same time. I will try that over the coming months and see how I go.

Cheers
Pop
AnswerID: 495183

Follow Up By: Member - Joe n Mel n kids (FNQ - Wednesday, Sep 19, 2012 at 00:05

Wednesday, Sep 19, 2012 at 00:05
and thanks also ....... i am gunna connect it all up and see what happens, as long as my sat phone is charged and i can call "help" i will be fine .....
...... KISS ...... keep it simple stupid ........ always wins in the end ..
Cheers
Joe
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FollowupID: 770878

Follow Up By: pop2jocem - Wednesday, Sep 19, 2012 at 11:22

Wednesday, Sep 19, 2012 at 11:22
I might just let you do it first Joe. If I see a big cloud of smoke I wont...lol

Cheers
Pop
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FollowupID: 770907

Reply By: Bellyup - Thursday, Sep 20, 2012 at 12:11

Thursday, Sep 20, 2012 at 12:11
Hi Pop,
The Ctek dc-dc charger is a great device.
You need to know that a car alternator will not charge an AGM battery to 100%.
An AGM battery really needs around 14.5v during their charging cycles to get to their full charge.
Most modern "smart" car alternators will only put out 13 -13.6 v so by the time it get through the Anderson plug then to the batteries you are probably only charging to 70-80%capacity - the end result will be a permanently damaged battery.
The Ctek type chargers will put out 14.5v (when required) regardless of of the input voltage ie it will take the alternators' 13.6v and boost it to 14.5v for the initial charge then drop back to 13.8v for maintenance.
Likewise with your solar panels - it will take the 17+v input and output between 13.8 to 14.5v depending on what the battery requires. Ive seen my solar voltage output drop to 4v at dusk but the voltage coming out of the Ctek is still 13+v albeit with bugger all amps but it is still putting in something.
Money well spent IMHO.
Bruce.
AnswerID: 495300

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