sorry fellas.....battery question

Submitted: Sunday, May 25, 2014 at 14:53
ThreadID: 107942 Views:2601 Replies:6 FollowUps:10
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I have at present under the bonnet a normal lead acid battery and a "deep cycle" battery which are both just over 2 years old and in decent condition for now. I do wish I'd've put in 2x Marine Pro batts but they will have to do for the time being until I feel reckless enough to ditch them or they fail me. What I really need answering is: what should I put in the van? The previous owner put in an average Chinese deep cycler (now cactus) which is the same as my aux in the car but......I am thinking AGM or Optima might be best or should I put in a Marine Pro with a view to my eventual change in the car?

Extra info that might be relevant: It's a Prado 120 D4D and has a Redarc isolator and also a diode booster which is working well since previously, there wasn't enough charge getting through to my aux batt. I would rather not have to go DC to DC if I can avoid it as it seems to work pretty well otherwise.

Thanks in advance.

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Reply By: Dennis Ellery - Sunday, May 25, 2014 at 15:44

Sunday, May 25, 2014 at 15:44
I’ve got 2 Century Marine Pro 730's under the bonnet and a Lifeline AGM in the caravan.
I wouldn’t put an expensive AGM under my bonnet as the heat would shorten its life and I don’t believe I would get value for my dollar.
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Follow Up By: HKB Electronics - Sunday, May 25, 2014 at 16:06

Sunday, May 25, 2014 at 16:06
Either the marine pro or the Optima would be ok in the van.

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Reply By: Steve - Sunday, May 25, 2014 at 16:36

Sunday, May 25, 2014 at 16:36
I never had any intention of putting an AGM under the bonnet but really wanted to know if an AGM or Gel would be best in the van or whether to go with a Marine Pro, bearing in mind that I'll be putting two of those in the car eventually. ???
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Reply By: Member - Frank P (NSW) - Sunday, May 25, 2014 at 17:05

Sunday, May 25, 2014 at 17:05
Steve,

What sort of voltage are you getting back at the van battery with everything plugged in and the engine running (fast idle)? Do this measurement with a half discharged van battery, resting voltage about 12.0V. Compare it with the voltage up the front.

Without a dc-dc charger, the success of your system depends on good cabling and connections.

How long is the cable run from your engine compartment to the van battery? Whatever it is, it will be long. If the cable sizing is inadequate for the length of the run then you will get excessive voltage drop, even given the higher starting point from your diode booster, your charging voltage AT THE VAN may be insufficient and your van battery may suffer in the long term as a result. (Could this be why the present battery is dying/dead?) If that is the case you could re-cable - I would suggest minimum 6 gauge including negative runs to chassis earth points. Or it might just be simpler to go the DC-DC charger route.

Another thing to consider is that, assuming you're going to put a deep cycle battery in the van, many (but not all) deep cycle batteries don't like the high charge currents that an alternator can deliver. Typically they like a max charging current of 10 to 15% of their C20 amp-hour capacity. ie, max current for such a 100Ah battery would be 10 -15 amps. So if you have the voltage at the van, choose a battery that will take the alternator output, and if you go the dc-dc charger route, match the charger to your battery.

Cheers


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Follow Up By: Member - Frank P (NSW) - Sunday, May 25, 2014 at 17:12

Sunday, May 25, 2014 at 17:12
I'll just tweak that last sentence:

So if you have suitable alternator voltage at the van, choose a battery that will take the alternator output (could be about 40-50 amps from your Prado, depending on cabling), and if you go the dc-dc charger route, match the charger to your battery.

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Reply By: pop2jocem - Sunday, May 25, 2014 at 17:48

Sunday, May 25, 2014 at 17:48
This is not questioning anyone's methodology, just a question.

It sounds like Steve has a similar setup to what I run. A cranking battery being the first in line for charging from the vehicle alternator. Then an AGM connected through VSR. Finally an Anderson plug with appropriate size (can't remember exactly) wiring to feed 2 AGM 105 AH batteries in the van. To me the vehicle alternator should sense the batteries being charged up and as the battery internal resistance (state of charge) rises the charging voltage increases and the amps taper off.
Not sure this is the ultimate way to go but seems to be working so far. All the AGM batteries are about 4 years old and seem to do their jobs OK. I replaced the cranking batteries about a year ago even though the old ones worked ok, just to be on the safe side.
When a 240v source is available, CP or similar I leave the van and vehicle connected so that both the van's and the vehicle batteries are charged by the van's Smartcharger.
With the vehicle running I get 14.4v at the vehicle batteries and about 13.8v at the van's batteries, so a volt drop of around .6v through the wiring. This after a good run of say 4 hours or more.
The vehicle is a pretty old low tech no smart alternator or computr involved jobby.
Cheers
Pop
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Reply By: Steve - Sunday, May 25, 2014 at 17:55

Sunday, May 25, 2014 at 17:55
Thanks Frank. I think the cabling is 6 gauge but need to check this as it was installed by previous owner. I thought it was working ok beforehand but if the cabling is lacking, I thought it would be an easy and relatively inexpensive job to run a thicker cable through and could only improve it? I was quoted $1000 locally to install a DC/DC so thought the current setup would be ok and certainly cost less. Would I still need to improve cabling with if I install a DC/DC if it is less than 6 gauge?

Arrived back at 1 pm today after a 3 hour drive and I have just (at 5.30) taken a reading with the multimeter @ 12.50. I then put a light on for a minute or so and it is still reading 12.50 so I'll check again tomorrow. Then probably give it a proper charge. Might be life in it yet? Maybe just left something on and ran it down?
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Follow Up By: Steve - Sunday, May 25, 2014 at 18:00

Sunday, May 25, 2014 at 18:00
edit: just ignore the word "with" in last line of 1st para.
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Follow Up By: Member - Frank P (NSW) - Sunday, May 25, 2014 at 20:23

Sunday, May 25, 2014 at 20:23
Steve,

"Would I still need to improve cabling with if I install a DC/DC if it is less than 6 gauge?"
Depends on how much less than 6 gauge it is. (BTW, by 6 gauge I mean 6B&S, or 6AWG which equals about 13sq mm of conductor, NOT 6mm auto cable which is less than 5 sq mm of conductor).

A 25 amp dc-dc charger will pull about 30 amps at full output. An on-line cable calculator I use suggests that if the cable run is up to 10m with chassis return (except for the short neg-to-chassis links) then 5mm auto cable would just suffice to power such a charger. If you have cabled return to the vehicle's battery negative then the absolute minimum would be 8 gauge. Either would be marginal and certainly NOT be good enough to get alternator output down there.

I think if I were to upgrade the cabling I would consider not ripping it out, but perhaps running the 6 gauge as an addition and connect the cables in parallel as close to the terminations as possible. That would give you effectively more conductor than just the 6 gauge, which can only be beneficial in any circumstance. (I have done that in my van to good effect.)

Also, the 6 gauge (or better) needs to be in the car as well, not just the van.

Running new or extra cable would be cheaper than installing a dc-dc charger, but you have to work out cost vs convenience.

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Reply By: The Bantam - Sunday, May 25, 2014 at 18:27

Sunday, May 25, 2014 at 18:27
The first question I ask is.

Where is the battery in the van located...and how well is it ventilated.

If it is in a poorly ventilated location I believe there is a case for an AGM or other high status battery.

But if the ventilation is good and the battery box is properly designed to contain and resist acid spillage or fumes.....I do not believe there is any advantage at all in AGM....appart from status and draining your wallet..

If you are not averse to activly maintaining a battery Trojan, wet cell, deep cycle, screw top, batteries are worth a look...they are a "propper" deep cycle battery....but ya ventilation better be good.....and they will need regular topping up.

a half way option is some sort of sealed, wet cell battery......in the top of the market they have all the advantages of AGM and pretty well non of the drawbacks and they will be cheaper.

A you may know....I and a few others are fond of the modern sealed marine batteries.......when a good marine battery that does have better deep cycle performance than standard batteries and at half the price of AGM.....they realy are worth considering.




as for the dc to dc charger........it may or may not provide an advantage.

If you go for an AGM with a low maximum initial charge rate you need a dc to dc charger purely on the bassis of current limiting.

as for a $groilla to install a dc to dc charger into a perfectly servicable existing system...HELL.

You can buy one of the top brands DC to DC chargers for between $300 and $500, depending on the model and how well you shop ( lesser brands can be had for as little as $200)........so what takes 5 hours...( one assumes $100 an hour).

Seriouly it aint rovcket science......mount the dc to dc charger unit....reterminate the incommong battery cables and fit to the dc to dc unit and make up a pair of cables between the dc to dc unit and the battery.......maybe insist on checking or reterminating the other connections... 2 or 3 hours should pull it up tops.


cheers
AnswerID: 533157

Follow Up By: Steve - Sunday, May 25, 2014 at 19:02

Sunday, May 25, 2014 at 19:02
in the boot of the van and not really well ventilated apart from two or three holes in the floor of it (maybe for gas? but my bottles are on the drawbar) which I could add to, but probably not. How are those marine batts for ventilation requirements ? Would a marine battery be ok in the boot or should I go AGM? Place in Sydney selling Marine Pro 730 for $189. As for maintenance, I'd have all the good intentions but just know I'd take my eye off the ball when work commitments press.

Perhaps should go the dc/dc - bloke on here recommended somebody in my area and he probably saw another electronics dunce coming thru the door. $$$$$$$$$$$$$$$$






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Follow Up By: Member - Frank P (NSW) - Sunday, May 25, 2014 at 19:40

Sunday, May 25, 2014 at 19:40
Steve,

I agree with Bantam re the cost and labour. If you want a battery management system then yes, $1000 is in the ball park, maybe on the low side. But just a simple dc-dc charger, including installation with cabling already there (providing it's adequate), well, I'm thinking $200-$300 for a basic 20 to 25 amp unit plus a couple of hours to hook it up. Maybe $500.00

If you want the ability to add solar to the same unit in the future, then add a bit more.

You'll have to choose re your battery and ventilation as Bantam says - work that out with him, I'm not the expert in that area though I agree with the principles he states. And then, as I posted in my earlier reply, match your battery and charging source.

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Follow Up By: Steve - Sunday, May 25, 2014 at 20:06

Sunday, May 25, 2014 at 20:06
just taking your last comment, Frank, "match your battery and charging source".... as well as cabling etc etc , all I need to do is find somebody that I can trust they know what they're doing/will do what I (make that a bold "I") need.

Probably need cabling upgrade (can't be that hard to tie on the end and pull) install dc/dc and then the battery replacement if needed is probably the easiest part.

btw, Just driven down the new Hunter Expressway today... saves half an hour of stop-start thru Cessnock and surrounds. Great to see a nice bit of road for our tax dollars.
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Follow Up By: Member - Frank P (NSW) - Sunday, May 25, 2014 at 20:44

Sunday, May 25, 2014 at 20:44
" btw, Just driven down the new Hunter Expressway today... saves half an hour of stop-start thru Cessnock and surrounds. Great to see a nice bit of road for our tax dollars."
Yes, I'm often up that way myself and look forward to the convenience.

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Follow Up By: The Bantam - Sunday, May 25, 2014 at 21:16

Sunday, May 25, 2014 at 21:16
All batteries require ventilation including AGM.
All batteries when over heated or over charged will vent explosive gasses and acid mist.

I am constantly astonished that caravan manufacturers install gass bottles and batteries in unventilated or poorly compartments.

Back to how much ventilation.

Use Bantam's fart test...if you farted in the enclosed space how long with it take to disipate?

If there are only holes in the bottom the addition of some sort of vents toward the top of the compartrment may be sufficient for a sealed battery.

any of the sealed batteries will contain most of the gasses.....though they may emit small amounts of gass in "normal" operation.


The amount of gass emitted by a screw top battery is much greater...they emit gass all the time they are charging and for some time after.

BY far the best option is a properly constructed battery box on the drawbar or a seperate compartment specifcally for the battery with plenty of air flow.

cheers
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Follow Up By: Steve - Sunday, May 25, 2014 at 21:56

Sunday, May 25, 2014 at 21:56
I'll keep em away from beans, sprouts, peas, mints, beer....that might keep the gasses down
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