..not another wiring/battery/fridge question...yes, sorry !

Submitted: Saturday, Aug 07, 2010 at 18:24

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Battery Power

In this article we explain why you might need an additional power source independent of the starting battery installed into your vehicle and we look in detail at types of batteries,

roger ramjet

Hi guys,

It's been so long since I posted here I've had to create a new username !!

Ive searched all the threads and also the www but haven't quite got my answer nor a solution to my problem....

History: ...(just added for colour and background...)
Years ago I purchased an EvaKool ED40L fridge, a 50watt BP solar panel and upgraded my main battery to an Exide N70ZZ. We went around Oz running the fridge with little problems straight off the main battery. On extended stays and way up North in the hotter climates (Arnhem, Broome etc.) I would run the truck on fast idle (2000rpm) both mornings and evenings for 10-15 minutes to ensure we were topped up. The fridge would occasionally stop overnight dependent on the overnight temp, but no major hassles.
I had no tools to measure the charge, I learnt from experience and it just worked. Although once in Innamincka before I had it all sorted out we did run flat..that was pretty funny really..pack up camp..oops, flat battery..put solar panel onto battery..set up camp again..stay another night..ah well !

Later on I extended this system to a second N70ZZ in the rear of the ute and ran a 100amp Redarc isolator to charge. I could then run radio from the main all night, long-life low voltage flouros and the fridge from the aux battery and everything was even hunky-ier dory-ier.
I was running 3mm auto wire to the aux battery, didnt seem to be an issue, aux. battery charged fine and lasted for years and years.

Problem:

Just recently, on an extended trip I replaced my weary batteries and decided to get a fullriver sealed 85amphour for the aux battery. Main battery still another N70ZZ. I upgraded the positive lead to 8GA cable and also beefed up the neg wires - a 'home made' multi strand earth strap to the 'lux rear chassis.

On this trip I had nothing but trouble, the redarc was unable to fully charge the fullriver resulting in a conked out fridge sometime during the night. It got to the point that I gave up and simply ran the fridge, whenever possible, straight out of the cig lighter connection off the main battery.
'
I could only charge to around 12.5 volts (from memory) which just wasn't enough to run the fridge for any length of time. Since Ive been back I've put the solar panel on and chrged up to 13.1V which runs the fridge fine for hours and hours.

Summary: The only thing that has changed in this setup after years of no problems is the change to the fullriver battery and some wiring upgrades (agreed I probably should be using 4GA but its still a vast improvement over what was there).

Summary:

Car: 1999 Hilux, 55amp alternator
Aux. Battery: fullriver sealed lead acid 85amphour
Wiring: 8GA positive and earth - 4mm / 56Amp
Battery Isolater: Redarc CP12V 100amp - Off V:12.5 On V:13.5
Max batt. charge on redarc: 12.5V
Max batt. charge on Solar panel:13.1V

Q's...

1. Multimeter says the aux battery charges to 13.1v at the most. I believe this battery (fullriver DC85-12) should charge to around 13.4 - 13.6v?

2. I'm running a Plasmatronics PR1210 regulator off the 50watt (2.4amps max) panel with a boost max of 14.6v. it would seem this regulator is perfect for the fullriver batt, providing a fast charge. The site I'm looking at (www.energymatters.com.au) suggests the PR120L for sealed lead acid batteries which actually has a lower boost max 14.2v, so I'm not convinced. Do I have the right solar regulator?

3. I had always run a negative strap to an unpainted part of the body in the rear of the ute, seemd to work fine on the N70. Should I be running a cable back to the main batt neg. , just to be sure?

4. What is the minimum cable size I should be running from the battery to the fridge inlet (about 2m)?

5. What is the minimum cable size I should be running from the redarc under the bonnet to the aux batt (about 5m)?

6. How do I measure the voltage input (on panel or redarc) with a multimeter whilst it's charging? The instructions on my cheap Dick Smith multimeter arent real clear.

7. Can I run the solar panel and the redarc AND draw off the battery all at the same time? (e.g driving with the solar panel attached to the roof)

7a. Should I install a reverse blocking diode on the panel side if I do no.7 ? (then I could leave it attached 24/7 without trickle back overnight?)

Thanks again for all your help!

Ramjet

PR1210
boost max 14.6v
Boost cutin 12.5v
Float max 14v
Float cutin 13.4v

PR1210L
boost max 14.2v
Boost cutin 12.5v
Float max 14v
Float cutin 13.4v

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Reply By: Battery Value Pty Ltd - Saturday, Aug 07, 2010 at 20:09

Saturday, Aug 07, 2010 at 20:09

Hi Ramjet,

I'll give it a shot, pls try to answer the following questions:

What's the open circuit voltage of your auxiliary battery (no solar and no load connected)?

Is the earth in the rear reliable?
You can test this by fast idling the engine and measure the voltage between this earth, and the one on the isolator/starter battery, while the fridge compressor is running off the auxiliary battery.

And, hopefully, you didn't connect the negative of the solar panel to chassis ground?

cheers, Peter

AnswerID: 426535

Follow Up By: roger ramjet - Sunday, Aug 08, 2010 at 08:08

Sunday, Aug 08, 2010 at 08:08

Hi BV

By ocv I assume you mean just sitting charged - 12.5v on the redarc but 13.1v on the solar panel.

The earth is/was good, well it seemed to work on the old battery, I havent changed it except to beef up the wiring marginally......Though you did just give me a thought, perhaps it has come loose?

To run your test I need to have everything installed as normal? That is the aux battery is 4-5m from the main earth, my multimeter probes aren't that long. If I bring the battery around to the engine bay and make a 4m different earth then I am voiding the test yes?
Can I run a thin gauge wire to the main earth from the multimeter probe?
I am also assuming I put the multimeter on 12V and stick either red or black probe on each earth terminal? If all is good I should get a 0V reading yes?

And, no. I actually know a bit more about solar than I do car stuff.

Thanks!
R

FollowupID: 697139

Follow Up By: roger ramjet - Sunday, Aug 08, 2010 at 08:09

Sunday, Aug 08, 2010 at 08:09

Sorry, ....Peter.

cheers
R

FollowupID: 697140

Follow Up By: Battery Value Pty Ltd - Sunday, Aug 08, 2010 at 08:20

Sunday, Aug 08, 2010 at 08:20

ram,

because your battery charges perfectly from solar, there could be an issue with the earth return (or even the positive).

Yes, pls measure the DC voltage differential between the two grounds with one of the voltmeter leads extended using thin wire. You shouldn't get more than a couple of hundred mV with the alternator spinning, and the fridge compressor running off the aux.
Yes, you're voiding the test if you change anything, so don't bring the battery around to the bay etc.

Yes, loose bolt on the ground would definitely cause something like this.

Good luck, Peter

FollowupID: 697141

Follow Up By: Battery Value Pty Ltd - Sunday, Aug 08, 2010 at 08:24

Sunday, Aug 08, 2010 at 08:24

might add, that it's better to stick one voltmeter probe directly on the negative on the auxiliary. That way you also test the integrity of your beefed up ground connection to the aux.

cheers, Peter

FollowupID: 697142

Follow Up By: Battery Value Pty Ltd - Sunday, Aug 08, 2010 at 08:50

Sunday, Aug 08, 2010 at 08:50

and if this test won't bring up anything unusual, do the same on the positive.
Voltmeter goes between the positives of the two batteries, alternator spinning, fridge compressor running.
There must be voltage drop now.
Leave one probe where it is, and the other one goes on either positive side of the isolation solenoid switch.
If there is voltage drop across the isolator, then the device isn't cutting in, maybe the alternator ouput voltage is too low, or the isolator electronics isn't properly grounded.
Check the alternator output voltage, it should be 13.8V.
If alternator voltage ok, the isolator switch is shot.

Needless to say, check all terminal connections on batteries, isolator in/out (including isolator ground connection), and battery grounds for looseness.
Some isolators need a positive signal from the ignition to switch on the solenoid. Check it.

cheers, Peter

FollowupID: 697145

Follow Up By: roger ramjet - Sunday, Aug 08, 2010 at 09:02

Sunday, Aug 08, 2010 at 09:02

Thanks Peter,

Really appreciate this test advice. I think above youve just told me how to measure voltage drop over my positive cable (it really is that easy?, doh) , something Ive always been interested in due to 5m length and marginal cable size.

Will run some tests and post. Not right now...tooo cold in Canberra. This afternoon.

Thanks very much!
Rich

FollowupID: 697147

Follow Up By: trainslux - Sunday, Aug 08, 2010 at 10:26

Sunday, Aug 08, 2010 at 10:26

If it was my setup, I would run a dedicated earth wire back to your main battery/ earth point.
Then you know its either voltage drop on the pos wire, or neg wire, or a connection in between.

Over the years I have found that earthing to chassis can work, but has often been the source of problems.
Even if you run 2x the 8gauge wire to help with voltage drop.

Might be that your agm that may accept a higher charge rate showed up a weakness in the system, either way, your testing of what Peter has posted will sort it out.

Let us know what you find.

T

Ps I run 3 batteries, 2 normal cranker and 1 agm, run dedicated pos and neg wires to all of them to eliminate any chassis earth issues, and also added extra chassis earth to help the rest of the system.

FollowupID: 697155

Follow Up By: roger ramjet - Tuesday, Aug 10, 2010 at 14:16

Tuesday, Aug 10, 2010 at 14:16

Hi Pete,

scuse the delay, too cold, got rear diff seal done yesterday, now its raining.....

Ran those tests..

ocv Aux Batt before test = 12.4V (I've run it down last weekend)

- to - = -.4mV
+ to + = -82.9mV
Solenoid (Aux side outlet) to +Aux = -60.2mV

Are these figures to high? 82.9 loss is getting up to 1V?

I haven't yet tested the alternator output as Im not to sure how/what to stick the probes on, the ol' Gregorys instructions don't make much sense to me :P.

Ive found two ways am Im not sure which is valid.

1 is to simply measure V at the +/- terminals with the engine in fast idle.
2 is to attach + probe direct to 'B+' terminal on alternator and neg probe to ground (batt neg??) with engine fast idle. But that would be big voltage no??!

Bit hesitant, dont want to blow up alternator/diodes/something else.

In any case, I'm going to run a 8GA cable from aux - to main - , just to do it proper like.

thanks again
Rich

FollowupID: 697456

Follow Up By: roger ramjet - Tuesday, Aug 10, 2010 at 14:41

Tuesday, Aug 10, 2010 at 14:41

righto,

just measured across the batt terminals for alt output and got 13.91V (actuallly went to 14.1V for a tick then steadied out). seems ok.

I think I might have two problems:

a) neg problem between aux batt and fridge.
b) voltage drop to aux battery means it doesn't fully charge from solenoid.

sound reasonable?

Im going for a drive later on with the aux battery connected with new 8GA earth and we'll see if the batt charges.

thnks
R

FollowupID: 697460

Follow Up By: Battery Value Pty Ltd - Tuesday, Aug 10, 2010 at 14:44

Tuesday, Aug 10, 2010 at 14:44

Hi Rich,

that's ok, it seems to be raining everywhere.

Your chassis voltage drop is a lot lower than the positive wire drop, hence no need to install additional cable from aux neg to cranker neg.
Your over-all voltage drop is less than 0.1V which is good.

Only thing remaining is the alternator/starter battery voltage.
Or an intermittent fault within the isolation switch electronics.
Is this switch controlled by a +12V signal wire from the ignition, or is it a voltage sensitive type of thing?

Yes, measure the alternator/cranker voltage across the starter battery +/- terminals.
If you have a ciga lighter on the dash, you could plug something like this in..

...to give you an idea what's going on while cruising along.

Good luck!

Peter

FollowupID: 697461

Follow Up By: Battery Value Pty Ltd - Tuesday, Aug 10, 2010 at 15:00

Tuesday, Aug 10, 2010 at 15:00

Rich,

since you measued overall voltage drop less than 0.1V, the battery gets to see 13.8V~14.00V.

That's already higher than the recommended float charging voltage.
Solenoid is good, at least while you did the measurements.
Could be intermittent but.
Aux battery will charge to at least 80% if you drive around for an hour or two and it should show close to 13V, when measured a few minutes after the motor stops, and no load connected.

cheers, Peter

FollowupID: 697463

Follow Up By: roger ramjet - Tuesday, Aug 10, 2010 at 15:05

Tuesday, Aug 10, 2010 at 15:05

thanks again.

MILLI-volt..if course only 0.1V loss. doh. diligo ut latin! (Love that Latin)

The starter battery ocv is 12.8V or thereabouts...its ok.

The solenoid is the good ol' redarc CP12V, all mechanical - goes clunk when cutting out. Which is good, reminds me loudly that it has done so after Ive stopped a while. :)

Thanks again for all your help Pete. Ive learn't a few things in the process, which is never a bad thing!!

cheers
Rich

FollowupID: 697464

Follow Up By: Battery Value Pty Ltd - Tuesday, Aug 10, 2010 at 15:33

Tuesday, Aug 10, 2010 at 15:33

no worries Rich, anytime

Just pulled up the specs of this isolator:
cutout voltage is 12.7V.

This means that your two batteries stay connected until both reach 12.7V.
So if something is draining the cranker down to 12.7V, the aux will also get drained to this level.

So this means that the isolator itself will drain both batteries with the specced current of 0.15A until it finally cuts out at 12.7V.

And because you hear the 'clunk' of the solenoid after stopping for a while, this level is being reached fairly quickly, and the aux hasn't even seen full charge yet otherwise it'd take hours for the voltage to drop this low.
Of course there is the fridge current which could make this drop quickly.

This also explains why you always measure a low voltage on the aux (and cranker), compared to solar.
I recommend to disconnect the fridge for a few days, and/or give the aux a good boost charging for 12 hours or more with a multi stage mains powered charger.
Could be that your aux is on its way out, meaning it's lost quite a bit of its original capacity.

On solar, this low capacity is hidden a bit, because the discharge starts from a higher voltage level.

You should give your aux a proper load test after it's been fully charged.
And give it a fortnightly boost charge with a proper charger.
Don't know if your solar regulator makes the voltage go up to 14.4V for a couple of hours which is important for good (deep cycle) battery health.

cheers, Peter

FollowupID: 697465

Follow Up By: roger ramjet - Monday, Aug 16, 2010 at 10:24

Monday, Aug 16, 2010 at 10:24

Hi Peter,

I've rewired everything and its now all good, my aux batt is charging well. I suspect after all that I had a flaky neg connection to my fridge. The wire was almost torn from the connector, only held on by 3 or 4 strands.

Your theory on the isolator is interesting, and might actually prove useful?? - I am drawing off both batteries until the solenoid closes, which is not necessarily a bad thing? (as long as the car still starts !!)
In any case Ive now got an almost fully charged aux (up to 12.8V) which will peak out just on 13.1V when on solar, which I assume is fully charged.

My only remaining queries are the use of multiple concurrent charging inputs:

7. Can I run the solar panel and the redarc into the aux at the same time? (e.g driving with the solar panel attached to the roof) Im pretty sure Ive done this before but I may be damaging the panel?

7a. Should I install a reverse blocking diode on the panel side if I do no.7 ? (then I could leave it attached 24/7 without trickle back overnight?)
This would also prevent any undue surge from the car charging system potentially damaging the panel.

thanks
Rich

FollowupID: 698022

Follow Up By: Battery Value Pty Ltd - Monday, Aug 16, 2010 at 11:39

Monday, Aug 16, 2010 at 11:39

Hi Rich,

good to read you've got it all sorted now.

The solenoid actually gets de-energised after a while, and the contacts open.

Yes, this has the effect of skimming the first few percent of charge from both the cranker and the aux.

Yes, you can charge the aux/cranker concurrently from the solar panel and the alternator.
But use a solar regulator, otherwise the battery voltage could creep up into the gassing region for too long.
Just DO NOT wire the negative of the panel to chassis ground, or the regulation will fail (if it's a common positive series regulator).

Yes, blocking diode is always recommended although this is for blocking the small back drain current at night, rather than for protecting the panel (from either the battery, or the alternator - there is no danger from these).
And if using a regulator, chances are the blocking diode function is already built in (there is only one domestic product I'm aware of which has no reverse blocking function built in).

Best regards, Peter

FollowupID: 698033

Follow Up By: Maîneÿ . . .- Monday, Aug 16, 2010 at 12:35

Monday, Aug 16, 2010 at 12:35

Rich,
you say "I've rewired everything and its now all good"

Can I ask, what gauge cable have you used ?

Maîneÿ . . .

FollowupID: 698039

Follow Up By: roger ramjet - Monday, Aug 16, 2010 at 14:19

Monday, Aug 16, 2010 at 14:19

Thanks Peter,

My ol' PR1210 unfortunately does not have a reverse blocking diode :-(, I might just unplug it at dusk.

Thanks again Peter. Next time Im in Brisvegas and need assistance or a part I know where to come. appreciated.

Thanks
Rich

Mainey,

Its 8GA between batteries, 2mm? to the aux power load and its all working fine, thanks.

Yes, I should use 4GA, its also twice as expensive and I've had no issues with using 2/3mm to charge my aux battery, with exactly the same solenoid and setup, for over 9 years. (which leaves me nonplussed and completely unconvinced about the 'necessity' to use huge cable), so what Ive done is actually a vast improvement. and I even made it all tidy with cable ties :-)

Thanks
Rich

FollowupID: 698047

Follow Up By: Maîneÿ . . .- Monday, Aug 16, 2010 at 16:46

Monday, Aug 16, 2010 at 16:46

Rich,
do you know the actual voltage loss you have in your system now ??

Maîneÿ . . .

FollowupID: 698064

Follow Up By: roger ramjet - Monday, Aug 16, 2010 at 17:55

Monday, Aug 16, 2010 at 17:55

Hi Mainey,

good question. I should check with real stats that I have indeed made a 'vast improvement'. Though according to the above I probably wont get much better but it will be interesting to find out.

not tonight though, its wet and freezing. I am soo looking forward to getting up the North Coast. Wednesday !

I'll post the data later on.

thanks
Rich

FollowupID: 698070

Reply By: Maîneÿ . . .- Tuesday, Aug 10, 2010 at 17:14

Tuesday, Aug 10, 2010 at 17:14

Ramjet,
why not *invest* in some correctly sized cable, run (+) to (+) and (-) to (-) that will eliminate many problems your system seems to have.

Then you can work out what else can be contributing to the problem.

Maîneÿ . . .

AnswerID: 426852

Reply By: drowned_rat - Wednesday, Aug 25, 2010 at 21:55

Wednesday, Aug 25, 2010 at 21:55

You have asked some good questions, also sounds like you have it all figured out too, just My $0.02 worth for anyone else reading this.
1. Multimeter says the aux battery charges to 13.1v at the most. I believe this battery (fullriver DC85-12) should charge to around 13.4 - 13.6v?
A: A lead acid battery has to get somewhere up over 14 volts to be considered fully charged.

2. I'm running a Plasmatronics PR1210 regulator off the 50watt (2.4amps max) panel with a boost max of 14.6v. it would seem this regulator is perfect for the fullriver batt, providing a fast charge. The site I'm looking at (www.energymatters.com.au) suggests the PR120L for sealed lead acid batteries which actually has a lower boost max 14.2v, so I'm not convinced. Do I have the right solar regulator?
A:If you look at the specs for this battery you need to get it up to around 14.5-14.9 in cycle use.
http://www.energymatters.com.au/fullriver-sealed-lead-acid-agm-battery-12volt-85ah-dc-%C3%82%C2%A0-p-2544.html
This regulator should be fine.

3. I had always run a negative strap to an unpainted part of the body in the rear of the ute, seemd to work fine on the N70. Should I be running a cable back to the main batt neg. , just to be sure?
A:I wouldn't bother, you can check the voltage drop by measuring the voltage between the negative on your fridge battery to the negative on your starting battery with the engine on fast idle. You can extend your multimeter lead with a reasonably thin piece of wire without affecting the reading.

4. What is the minimum cable size I should be running from the battery to the fridge inlet (about 2m)?
A: Whatever the fridge comes with shoudl be fine as the current is relatively low at this point.

5. What is the minimum cable size I should be running from the redarc under the bonnet to the aux batt (about 5m)?
A: As big as you can get, I tried a battery down the back of the vehicle but could only get 5 Amps charge current with the alternator charging, this was going to take 20 hours to charge my 100 Amphour battery up from flat. I have since moved the battery into the engine bay and can get around 30-40 Amps off a 110 Amp alternator. I have the batteries close to each other and starter motor size cable between it an the starting battery. This brings my charging time down to 2-3 hours.

6. How do I measure the voltage input (on panel or redarc) with a multimeter whilst it's charging? The instructions on my cheap Dick Smith multimeter arent real clear.
A: (I think you have this worked out) Set it to the 20V DC setting and put the red lead on the + terminal and the Black lead on the - terminal.

7. Can I run the solar panel and the redarc AND draw off the battery all at the same time? (e.g driving with the solar panel attached to the roof)
A: I did this on my setup once I eventually got a solar panel. The Alternator will be doing most of the work when the engine is running.

7a. Should I install a reverse blocking diode on the panel side if I do no.7 ? (then I could leave it attached 24/7 without trickle back overnight?)
A:The discharge back through the solar panel is in the region of 5-10 mA, this is pretty negligible in the scheme of things. A blocking diode would only be required if you were to park the vehicle in the garage for extended times and not run the engine.

A 50W solar panel will just about keep up with a fridge of that size providing you get mostly sunny weather and it isn't to hot. With that arrangement you will need to rely on the cars alternator to be charging correctly.

AnswerID: 428460