Battery Charging

Submitted: Sunday, Nov 16, 2008 at 20:58

ThreadID: 63571 Views:6030 Replies:5 FollowUps:15

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TIGER

Hello all genuises.
I have a scenario I will try my best to explain, but if you dont understand please let me know and I will try to clarify.
I drive a 4 litre Petrol Prado towing an Australian Off Road camper. Camper has 2 calcium batteries 120a/h each (240a/h total). Prado has an aux 4X4/Truck calcium battery, I think its 70a/h. I have a TJM IBS dual battery isolator seperating the starting battery from the aux/camper batteries. With this isolator you can manually parrallel all batteries together.
I was camping at a powered site this weekend with my CTEK 25A charging my camper batteries which will power an Evakool 50ltr fridge, lights and Water pump. I also had my car aux battery connected to the camper via an Anderson plug. I was listening to music from the car stereo (powered by starting battery) most of the day and thought that as I am connected to 240V with a 25A CTEK charger, why dont I charge my car batteries (both starting and aux). I could do this electrically by manually closing isolator to connect all 4 batteries together by the TJM IBS Controller.
So CTEK output was 14.5 volts in recondition mode and this volt was checked at camper batteries and Anderson plug from trailer. Car was still electrically connected to camper via Anderson Plug. Now the Voltage checked at both car batteries was 12.17 volts (car engine NOT running). Why I thought.
Anderson Plug wiring is off heavy gauge, I think 6 or 8 gauge. Both Car Batteries have a Projecta Fused Positive terminal post on them. They have a red cover on them and allow you to have 3 fused outputs straight of the positive terminal battery post. (Dont know if you know what Im talking about here, but I dont think its important.)
I electrically disconnected the positive terminal of the Anderson plug straight off the Aux battery post and voltage checked at 14.5V. And then when you connect it too the Aux Battery terminal post, this battery and the starting battery are again reading 12.17V.
With Camper and car electrically disconnected the car batteries are reading 12.17V with the 2 car batteries parralleled.
Why?? Shouldnt all batteries be reading 14.5V in this scenario.
Can anyone explain this. Could both car batteries have an internal resistance (a failed cell)
Would love an explaination, so please if you have a theory or better still, an answer to this problem, please take the time to jot it down. Its GMF'd

Tiger

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Reply By: Member - Phil G (SA) - Sunday, Nov 16, 2008 at 21:28

Sunday, Nov 16, 2008 at 21:28

Assuming all your wiring/fuses/circuit breakers/whatever are intact,

2 Reasons:
#1 Your charger is putting out its maximum current (hardly surprising with all those batteries connected)
#2 There will be voltage drop on the long cables.

The battery voltages will rise as they recharge.

AnswerID: 335593

Follow Up By: TIGER - Monday, Nov 17, 2008 at 12:02

Monday, Nov 17, 2008 at 12:02

Hi Phil,
Wouldnt the battery voltage read 14.5V even after the cable length straight away, and depending on ouput current of charger determine how long the batteries can maintain a charge.
Tiger

FollowupID: 603364

Reply By: oldtrack123 - Sunday, Nov 16, 2008 at 21:54

Sunday, Nov 16, 2008 at 21:54

Hi Tiger
Just to clarify what you are saying
Are you getting the same voltage at all 4bats when all are connected or are yiu getting 14+ v at van & only 12+ at aux?
What do you get @ aux with crank not connected?

AnswerID: 335598

Follow Up By: TIGER - Monday, Nov 17, 2008 at 12:00

Monday, Nov 17, 2008 at 12:00

Hi Oldtrack123.
I am getting 14.5 volts at the camper trailer batteries when CTEK is powered and with the camper and car connected via an anderson plug, I am getting 12.1V at the car aux battery. With my dual battery isolator I can manually parallel the starting battery and Aux battery and the same voltage (12.1V) is also checked at the starting battery in this same scenario.

If I unbolt the positive lug (coming from the Anderson plug) attached to one of the fused outputs on this terminal block attached to my aux battery, the voltage reads 14.5V but when attached reads 12.1V.
I get the voltage loss (12.1V) when this same lead (anderson plug positive lead) is electrically attached to the aux battery or starting battery or both. Its also worth noting that the car battery voltages are the same (12.1V) even when I disconnect the anderson plug from the Camper trailer.
Remember this charging voltage is coming from the camper trailer CTEK charger to the car batteries via the anderson plug.

Cheers
Tiger

FollowupID: 603362

Reply By: Geoff (Newcastle, NSW) - Sunday, Nov 16, 2008 at 22:59

Sunday, Nov 16, 2008 at 22:59

Hi,

Is this how you've got it all connected and are these the voltages you are seeing at each point?

If so is the fuse Ok that protects the cable that goes from the auxillliary battery in the car to the Anderson Plug?

When you say,
"I electrically disconnected the positive terminal of the Anderson plug straight off the Aux battery post and voltage checked at 14.5V"

Did you physically unbolt the fused terminal off the battery or did you lift the wire off the fused terminal and leave the terminal on the battery?

The most likely scenario is a dirty connection in the Anderson plug on either the camper or car side.
Or,
Have you run the negative cable for the car auxilliary to the camper batteries as a cable and not a chassis earth somewhere on either side of the Anderson pug? Is it like my drawing or is the negative bolted to the body and relying on that somewhere?

Geoff

Geoff,

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AnswerID: 335613

Follow Up By: RV Powerstream P/L - Monday, Nov 17, 2008 at 07:56

Monday, Nov 17, 2008 at 07:56

Paralleing all batteries allow the strongest cgarge to flow to the weakest charge until they settle all about the same.
Calcium batteries need 15.1V to charge properly and although they work OK in a cranking situation they are suffering undercharging in tne Aux/Camper application.

The Anderson Plugs are tapered connectors and are spring loaded so they a basically self cleaning .

If you cable run if 6M from cranking battery to camper batteries and is 8GGE at 25A your voltage drop would be 0.646V.
If it is 6GGE at 25A your voltage frop would be 0.406V.

An acceptable voltage drop is 0.36V and the calculation is based on both positive and negative cable runs not a chassis earth which can creatse a higher loss.

The calcium can float at 13.6V so you are only getting just above that at 13.95V with 8GGE and although it will eventually charge to the capacity of the CTech be prepared to stay for a lot longer connected to mains power and even then 14.5V is a lot of lost capacity that should be to 15.1V.

Ian

FollowupID: 603328

Follow Up By: TIGER - Monday, Nov 17, 2008 at 11:50

Monday, Nov 17, 2008 at 11:50

Hi Geoff,
Thanks for going to all this effort drawing up this diagram.
Firstly can you have a look at this link to visualise this Battery terminal fused output Im talking about.

http://cgi.ebay.com.au/DUAL-BATTERY-TERMINAL-ACCESSORY-FUSE-ABR-SIDEWINDER_W0QQitemZ310101029940QQcmdZViewItem?hash=item310101029940&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A1%7C39%3A1%7C240%3A1318

Fuse is good.

What I done was unbolt the positive lug (coming from the Anderson plug) attached to one of the fused outputs on this terminal block attached to my aux battery.

When unbolted and moved away from aux battery terminal it reads 14.5V but when attached reads 12.1V. So I thought the Anderson plug connection should be OK as we have 14.5V all the way to the aux Battery terminal when disconnected. I get the voltage loss (12.1V) when this same lead (anderson plug positive lead) is electrically attached to the aux battery or starting battery or both. Its also worth noting that the car battery voltages are the same (12.1V) even when I disconnect the anderson plug from the Camper trailer.
Remember this charging voltage is coming from the camper trailer CTEK charger to the car batteries via the anderson plug.

I have a negative cable running from aux battery to Anderson plug.

I look forward to any other suggestions. At this stage to me it seems to be a battery problem but I find it hard to believe that both car aux/starting batteries have this same internal resistance that causes this same voltage drop.

Tiger

FollowupID: 603359

Follow Up By: Geoff (Newcastle, NSW) - Monday, Nov 17, 2008 at 17:50

Monday, Nov 17, 2008 at 17:50

Mate, I drew it up because that way you and I both know I've grasped exactly what you are telling me.

"Firstly can you have a look at this link to visualise this Battery terminal fused output Im talking about."

That's exactly what I imagined you are using.

"What I done was unbolt the positive lug (coming from the Anderson plug) attached to one of the fused outputs on this terminal block attached to my aux battery."

I was pretty sure this is exactly what you were talking about, thanks for confirming it.

"When unbolted and moved away from aux battery terminal it reads 14.5V but when attached reads 12.1V"

This indicates to me a high resistance joint somewhere between the camper and the point you took this measurement. Without a load and the crimp lug in your hand you got 14.5V. With a load, the crimp lug connected to the auxilliary battery you get 12.1V yet in the camper you still get 14.5V. Youve got significantly different voltages at each end of the same wire!

The first place I'd look is at the crimped and/or soldered joints where these two cables are terminated, the positive and negative that go from the auxilliary battery under the bonnet to the camper batteries including the 4 crimped or soldered joints in the Anderson plug. You are looking for in electrical parlance a hot or dry joint, a joint that has high electrical resistance through bad soldering or crimping.

Or maybe even a negative cable that has been partially crushed or cut can give the same outcome without blowing a fuse!

As Ian has said the Anderson plug is self cleaning and spring loaded so I doubt if the hot joint will be at the contact tips but check them anyway.

I suspect there isn't anything wrong with any of your batteries, all you are seeing under the bonnet is the effects of two well connected and slightly discharged batteries that are receiving nothing from the charger in the camper.

Let me know how you go with the crimp lug checks, it's all a process of elimination. The drawing always helps to visualise what is going on.

Geoff

Geoff,

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FollowupID: 603408

Follow Up By: TIGER - Monday, Nov 17, 2008 at 21:54

Monday, Nov 17, 2008 at 21:54

Good on ya Geoff.
I think your on the money there.
I will check it out this week or next and let you all know.
Its absolutely fantastic to know that when you face a problem you cant find a solution for, you know an answer is not too far away after putting it out there on sites like this.
I love this site and all the other forums out there, that are made up of people like you who are not too busy to offer there help.
Thanks again to all.

Tiger

FollowupID: 603460

Follow Up By: Member - Mike DID - Wednesday, Nov 19, 2008 at 10:50

Wednesday, Nov 19, 2008 at 10:50

"Paralleing all batteries allow the strongest cgarge to flow to the weakest charge until they settle all about the same. "

No, cross-charging of batteries is a myth.

Batteries put out 12.8 volt max under load - have you ever heard of a battery charger that puts out 12.8 volt ???

Yes, I have tested it - you may get 10 amphours of transfer from a fully charged AGM to a discharged wetcell - that's definitely not charge equalisation.

FollowupID: 603687

Follow Up By: RV Powerstream P/L - Thursday, Nov 20, 2008 at 20:54

Thursday, Nov 20, 2008 at 20:54

If the post had been read properly the reference to paralleling the batteries was by using a splitter which means that the batteries were isolated in discharge.

In this application a migration of charge can happen when the batteries are paralleled and to the point that it can cause a dangerous situation if the splitter is of the relay variety.
Ian

FollowupID: 603961

Follow Up By: RV Powerstream P/L - Thursday, Nov 20, 2008 at 21:09

Thursday, Nov 20, 2008 at 21:09

An Example to explain my position re Relay Splitters.
This system is both dated and extremely dangerous and more than likely will make your boat fall short on CE requirements, especially if an inverter is used or a bow thruster. The good side is that it is easy to fit and requires no alterations to the standard engine system, but merely connects the domestic battery bank to the engine battery via a relay, which is energised when the engine starts.
The bad side (and the very dangerous side) is that a relay is prone to vibration faults and over loading. Say, for example, you have a 70 amp relay on your system and a 55 amp alternator, all seams great, but if you fit a 1500 watt inverter which can draw150 amps and one morning the domestic battery is flat. So, you start the engine to charge the domestic batteries, the 70 amp split charger relay will come on line to enable the alternator to charger the domestic battery bank. Then you load your inverter to 150 amps, the 150 amps will not be drawn from the domestic battery because it is flat but be drawn from the engine battery (which is full). That means you will draw 150 amps up the split charge cable and through the 70 amp relay. If you are lucky you will destroy the relay, if you are not so lucky then you will set fire to the cross over cables, hence the dangerous aspect. The system must be suitable for the purpose for which it is installed this is clearly not. Be warned about split charger systems using relays.
Ian

FollowupID: 603962

Reply By: RV Powerstream P/L - Monday, Nov 17, 2008 at 07:58

Monday, Nov 17, 2008 at 07:58

Please excuse the spelling I was in a hurry.
Ian

AnswerID: 335635

Follow Up By: TIGER - Monday, Nov 17, 2008 at 11:35

Monday, Nov 17, 2008 at 11:35

Thanks Ian,
So how does a CTEK charger charge Calcium Batteries efficiently, overnight?
The cable length would be about 6m to charge car batteries off the CTEK, but this would not be a normal scenario. I was only trying to top up the car starting battery as I was playing car stereo all day. But to charge the Calciums in the Camper with CTEK only 1m away can you increase output of CTEK to 15.1V?
I dont think you can, so that means my camper batteries are not being 100% charged?
Look forward to any suggestions
Tiger

FollowupID: 603358

Follow Up By: RV Powerstream P/L - Monday, Nov 17, 2008 at 13:14

Monday, Nov 17, 2008 at 13:14

Tiger
It doesnot it can only charge to its stated capacity and you can never 100% charge calciums no matter how long you leave them connected.
Charging Technology is just catching up to Calcium batteries now and some new equipment has a Calcium charging regime.

The new range of Sterling Combi Inverters have a calcium charge so too the dry mount Pro Tech and Pro Nautic from Sterling UK
and Pro Mariner of USA.
I currently have a sample 120A 12V pro Nautic Combo charger with 6 outlets that has calcium charging.

You do not indicate that you have a negative cable from the Anderson plug to the cranking battery and if you are using a chassis earth every joint represents a resistance and 1 ohm of resistance means little to lights etc but in a charging circuit it may mean no charge that is why in a charging circuit it is better to run both negative and positive cables.
Ian

FollowupID: 603368

Follow Up By: TIGER - Monday, Nov 17, 2008 at 22:04

Monday, Nov 17, 2008 at 22:04

Thanks FYI.
Yes the negative cable of the Anderson Plug is directly wired to negative post of Aux Battery in car.
Ill look these systems up that you have suggested.
Thanks
Tiger

FollowupID: 603468

Reply By: Maîneÿ (wa) - Monday, Nov 17, 2008 at 11:44

Monday, Nov 17, 2008 at 11:44

From what I understand you have 4 batteries, a known total of 310ah, PLUS one battery capacity not nominated, so assume 90ah giving 'maybe' 400ah total capacity for the 4 batteries.
The generally accepted charge rate is ~10% of DC capacity (40A)
yes, you can use 6 Amp charger, I didn't suggest impossible :))

Tiger,
can you advise:

* A few hours after charging has stopped, and been disconnected, what is each of the four battery “individual-DISconnected” Voltages ??

* What are EACH of the individual (battery) Voltages, when checked at the battery terminals, when the Ctek charger 'IS STILL' charging the Camper battery system for at least a few hours ??

Mainey . . .

AnswerID: 335666

Follow Up By: TIGER - Monday, Nov 17, 2008 at 22:01

Monday, Nov 17, 2008 at 22:01

Hi Mainey,

The 4th Battery is a starting battery only. Not that it matters Im guessing.

The info you have asked for I dont have at this stage. I only measured the battery voltage when CTEK was charging only after about an hour and they were 14.5V at camper trailer and 12.1V at car battery. The car batterys were 12.1V before I connected CTEK, but the CTEK was always connected to the cars Aux battery and there was no increase of this voltage after 2 days.

Ill get back to you with some more info when I get it out and have more of a play.

Cheers
Tiger

FollowupID: 603466

Follow Up By: RV Powerstream P/L - Friday, Nov 21, 2008 at 19:19

Friday, Nov 21, 2008 at 19:19

Miainey
What would be good in this situation is a splitter that gives zero volt drop and gives seperate charging to basically three battery banks and isolates three battery banks ,safeguards against over voltage and reverse flow and is suitable for distribution of alternator output and regulated solar input .
Dont you think that would be good as you dont have to guess which one is not doing its job and you do not have to disconnect anything to work it out.
Ian

FollowupID: 604042

Follow Up By: Maîneÿ (wa) - Friday, Nov 21, 2008 at 19:39

Friday, Nov 21, 2008 at 19:39

Ian,
Yes, a splitter that will give zero Voltage drop, separate charging to the three battery banks, isolates the battery banks, will safeguard against over voltage and reverse flow, suitable for both distribution of alternator and also regulated solar power currents would be a dead set bonus to a system of this configuration.

Please place a Link to the specs :-))

Mainey . . .

FollowupID: 604043