Aux battery

Submitted: Wednesday, May 05, 2021 at 10:54
ThreadID: 141682 Views:935 Replies:5 FollowUps:22
hi all,

time has come for a new aux battery under the bonnet of my 80 series

the current one (century marine pro) refuses to show a green indicator in the window however does charge but as soon as the fridge powers on only lasts a couple of hours. All I run off the 2nd batt is a 40l waeco & LED camp light + UHF. I am using a Pirahna DBE180SX controller

I keep the battery charged using a CTek charger and have tried the regen option but it doesnt seem to make any difference. Ive also had it tested for CCA's and its down well below 50% so new battery time

My question is, do I go for another dual purpose type or dedicated deep cycle (N70T)?

AGM i understand is no good for under bonnet use however have seen these advertised as 'dual purpose' and ok for under bonnet, has anyone got any experience with these?

https://www.autoelec.com.au/135ah-agm-sla-12v-deep-cycle-dual-purpose?gclid=Cj0KCQjw4cOEBhDMARIsAA3XDRiVJ6FHaoq8QU8tG4iOKR3h7zd8MLZvT0trW8vcuLWrZu-Nx7TkTN0aAjLvEALw_wcB

thanks
rob



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Reply By: Member - McLaren3030 - Wednesday, May 05, 2021 at 11:20

Wednesday, May 05, 2021 at 11:20
Hi Rob,

Firstly. let me state that I am not an Auto Elec. or a 12 volt expert, just someone who has been camping on and off road for over 50 years.

A dual purpose battery is a compromise battery, it will not deliver all the benefits of either a cranking battery, or a deep cycle battery. IMHO, you would be better with a dedicated cranking battery for what the vehicle needs, and a seperate deep cycle battery for ancillary items such as fridges etc. There are plenty of people who like you have used a dual purpose battery quite successfully.

The next issue you raised is where to put the auxiliary battery. It is better off inside the cabin, but you can put them under the bonnet if you can protect them from any heat sources, not always easy.

If you intend keeping the 80 series for some time to come, have you considered a LiFePo4 battery and appropriate DC/DC charger for an auxiliary battery? If you can afford it, this would be the way to go.

Macca.
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Follow Up By: Robnicko - Wednesday, May 05, 2021 at 12:12

Wednesday, May 05, 2021 at 12:12
thanks for your reply and advice Macca

Ive had the 80 since new (1995) and intend on keeping it a long time so is a stayer

In regards to battery location, for now I will keep it in the engine bay as all the wiring & tray is there

I guess I will look towards a 'pure' deep cycle this time as opposed to dual purpose

Rob




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Reply By: Allan B (Sunshine Coast) - Wednesday, May 05, 2021 at 12:29

Wednesday, May 05, 2021 at 12:29
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Hi Rob,

The "Century Marine Pro" is a "good" battery. How long did your present one last?
Cheers
Allan

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Follow Up By: Robnicko - Wednesday, May 05, 2021 at 13:09

Wednesday, May 05, 2021 at 13:09
hi Alan

it lasted just over 2 years and now out of warranty

regards
rob
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Follow Up By: Allan B (Sunshine Coast) - Wednesday, May 05, 2021 at 13:27

Wednesday, May 05, 2021 at 13:27
Rob,

"2 years" battery life is very poor performance but does not surprise me for an AGM under the bonnet.
That was the sort of AGM life I was getting in a Troopy until I installed a heat shield.
You should get at least 4 years life from a well looked after AGM. Some claim as much as 8 years!!!

If you wish to keep the AGM in the engine compartment you could consider installing a heat shield arranged to shield the battery both from the engine and from the hot air from the radiator. Obtain cooling air coming in at the front but not through the radiator and passing out at the back below the firewall.

I will try to locate the photo of how I arranged it.
Cheers
Allan

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Follow Up By: Allan B (Sunshine Coast) - Wednesday, May 05, 2021 at 13:55

Wednesday, May 05, 2021 at 13:55
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Ahh, found the photo.
The shield is composed of doubled-over foil covered foam sheet from Clark Rubber.
Cheers
Allan

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Follow Up By: Dennis Ellery - Wednesday, May 05, 2021 at 15:25

Wednesday, May 05, 2021 at 15:25
Hi Allan, Robs Marine Pro is a flooded battery not an AGM.
I’ve had Marine Pro’s last 5 years.
For a 2 year life, the battery didn’t die – it was killed!
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Follow Up By: Allan B (Sunshine Coast) - Wednesday, May 05, 2021 at 16:27

Wednesday, May 05, 2021 at 16:27
.
Yes, of course it is flooded. I wasn't thinking!
But if it is flooded, and described by Century as "Engine starting and semi-cycling", then maybe Rob has been overdoing the cycling?
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Follow Up By: Dennis Ellery - Wednesday, May 05, 2021 at 16:33

Wednesday, May 05, 2021 at 16:33
Hi Allan, I should have explained to Rob why I use AGMs.
I have high battery usage with 2 Fridges in my 4WD and AGM is a better option for me over flooded cells.
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Reply By: RMD - Wednesday, May 05, 2021 at 12:51

Wednesday, May 05, 2021 at 12:51
It reads as though the Pirahna DBE180SX, is a high capacity VSR and ONLY accepts 8 amps of REGULATED solar, ie, no internal regulator of it's own. Looked at the Fish site to see. That is small input of solar to a fridge battery and may not keep up while stopped. Therefore, depending on the previous success of the Century, as Alan asked about, and the desire to use an AGM, the battery is still affected by the alt max voltage, AGM's like around 14.4 v up to 14.7 to attain full charge and the alternator may not be ever charging it fully so always behind the 8 ball. If alt reg is down in max reg voltage you are pushing for any battery use ebven though it supplies the star battery reasonably well.
You can use an AGM under bonnet, some claim that ability to sell them. However, serious insulation of reflective foam board under and at sides would heat insulate the AGM battery fairly well. Most people never do that at all. If near front of engine bay, and with sufficient radiated heat insulation, the battery can be duct fed cool air nearly all the time while trying to be heated by engine. Duct cooling to specific engine bay areas does work. I have used it preciously also on petrol engine ignition modules which fail from heat. After a couple of failures of distributor modules the added ducting and subsequent cooling cured the problem. Batteries love it too.
If duct supplies air to the air gap between battery and insulation panels it remains and operates cooler. Owners can do many things to improve component reliability if the issue is seriously considered.
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Follow Up By: Robnicko - Wednesday, May 05, 2021 at 13:16

Wednesday, May 05, 2021 at 13:16
hi RMD,

ive confirmed the alternator is fine and supplies sufficient power to the main batt plus the one being fed by the piranha controller.

on cold start usually starts around 14.7v and settles to 14.1-14.4 variable dependent on load after a short while and also whether lights on etc to both batteries.

I have an in cab dual display so can see both batteries whilst driving and theyre always getting sufficient voltage

starter battery is fine, its been in for over 4 years now
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Reply By: Dennis Ellery - Wednesday, May 05, 2021 at 13:40

Wednesday, May 05, 2021 at 13:40
Hi Rob
In my 2008 V8 Diesel 70 series Troopy, my previous two Century Marine Pros lasted 5 years.

I now have two Century Dual Force AGMs with a 2 year warranty. They are made for 4WD under bonnet use. I emailed Century about their recommend voltage for my vehicle and they recommended 13.8 to 14Volts. I then installed a HKB Adjustable Voltage Booster to set this voltage.

AGMs charge at a quicker rate than flooded batteries, but how long will they last – only time will tell.
AnswerID: 636254

Reply By: Dennis Ellery - Wednesday, May 05, 2021 at 16:36

Wednesday, May 05, 2021 at 16:36
Hi Rob - I have high battery usage with 2 Fridges in my 4WD and AGM is a better option for me over flooded cells.

The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded is specified at 50 percent DoD to attain the same cycle life.

That’s the reason I use AGM over flooded batteries. They can be close to 100% charged in two/three hours by a conventional vehicle alternator/regulator. Normal vehicle charging systems take flooded batteries up to about 70% charge, often less. If Discharging to 40 or 50% - this limits effective usage to 20 or 30%.

AGM batteries can be quickly charged to well over 90%. They can also be safely discharged to 40% or so without damage, and to 30% without seriously shortening their life.
This gives me an effective usage of 50 to 60% - about twice that of similar-sized flooded batteries.
AnswerID: 636258

Follow Up By: Robnicko - Wednesday, May 05, 2021 at 17:35

Wednesday, May 05, 2021 at 17:35
thanks for the update Dennis

my situation is I need to mount the battery in the existing tray which is in the engine bay

the one in the link above at start of my post is described as suitable for under bonnet applications and I really want to try it or the Century dual force for the reasons you describe above. the one in the link has a longer warranty

decisions decisions........
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Follow Up By: Dennis Ellery - Wednesday, May 05, 2021 at 17:43

Wednesday, May 05, 2021 at 17:43
Hi Rob, That battery in the link looks good - I haven't heard of the manufacturer.
I know of Century, having used their various batteries in my time.
That battery would be too long to fit my battery tray.
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Follow Up By: Zippo - Wednesday, May 05, 2021 at 18:39

Wednesday, May 05, 2021 at 18:39
Dennis, while AGM batteries will absorb charge at the rate you indicated, MANY AGM manufacturers specify max charge rates of 20A or so (C/5). Exceeding that spec is not in the interests of battery longevity.
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Follow Up By: RMD - Wednesday, May 05, 2021 at 19:30

Wednesday, May 05, 2021 at 19:30
Dennis
They may accept more BUT.
Isn't the reason AGM batteries require no more charge rate than 20amps approx, IS because they cannot withstand high current input BECAUSE they are semi fluid and heat gasses the gel paste and buckles the electrodes surface, where washed /flooded in acid batteries can withstand more because they are in instant molecular contact and therefore greater heat tolerance/transference.

Charging an AGM fully in a short time is what Allan said, charge rate can't be controlled by Alternator charging.
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Follow Up By: Dennis Ellery - Wednesday, May 05, 2021 at 19:37

Wednesday, May 05, 2021 at 19:37
Hi Zippo,
All AGMs aren’t the same, you are quoting standard AGMs.
I know of two high quality AGMs such as Lifeline and Optima which accept very high charge rates.
For charging a Lifeline 100ah battery in my previous caravan - I used to connect three cheap 40amp chargers to it and pump 100 amps into it.
The following quotes are from Optima and Lifeline – you can look them up on the internet.
Lifeline “Due to the low impedance design, Lifeline@ batteries can tolerate in-rush current levels as high as 5C - (500A for a IOOAh battery).”
Optima “Alternator 13.65 – 15.0V, no amperage limit”

As for Century Dual force, they are designed to run off the alternator output of a 4WD.
At startup my 4WD is 14.4v and settles to 14.1v when hot - it charges faster than my previous flooded cells.
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Follow Up By: Zippo - Wednesday, May 05, 2021 at 21:21

Wednesday, May 05, 2021 at 21:21
Dennis, I did say MANY, not all.

Pick your product, pick your manufacturer/specs, pick your charge method, pick your outcome. Choose any three.

At the end of the day, as I mentioned in another thread recently, it's YOUR $$$ and outcome, not mine.
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Follow Up By: Member - McLaren3030 - Thursday, May 06, 2021 at 08:03

Thursday, May 06, 2021 at 08:03
Hi Dennis,

I question the 80% Depth of Discharge for an AGM battery. I was under the impression that AGM batteries do not like going below 50% SOC/DOD. If the AGM battery that you are quoting from has an 80% DOD, then they would be a much cheaper option for the same benefit as LiFePo4.

Macca.
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Follow Up By: Dennis Ellery - Thursday, May 06, 2021 at 10:50

Thursday, May 06, 2021 at 10:50
Hi Macca
80% DOD is the limit but I wouldn’t go there regularly.
I use a cheap voltage cutoff relay set at a 60% DOD

I previously used Lifeline AGMs in the caravan and I quote the following figures from their manual.
You will get less cycles out of the cheaper quality brands but they wouldn’t be much chop if they couldn’t recover from an 80% discharge.

You can Google - Lifeline Batteries Technical Manual - and look at their AGM DOD life cycles on page forty - 90% 450cyc - 80% 550cyc - 70% 700cyc - 60% 800cyc - 50% 1000cyc.

I no longer use AGMs in the rear of the van, my LiFePO4 100Ah has 2000 cycles at 100% DOD - 60% 5000cyc - 70% 4000cyc.

I would use a LiFePO4 under the bonnet if they could handle the heat and recently, I found one but it was worth $1600. I don’t mind paying for quality but I will be selling the Troopy soon and I couldn’t justify the price.
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Follow Up By: Member - McLaren3030 - Thursday, May 06, 2021 at 11:40

Thursday, May 06, 2021 at 11:40
I looked up Lifeline batteries on line, and read their statements. That DOD for that particular brand of AGM battery may be fine owing to the construction of their batteries, but a blanket statement that AGM batteries can safely be discharged to 80% DOD, is misleading. Also, looking at the specs for these batteries they appear to be very heavy, 70+ kgs for the ones I looked at. Was I looking at the correct battery?

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Follow Up By: Allan B (Sunshine Coast) - Thursday, May 06, 2021 at 12:00

Thursday, May 06, 2021 at 12:00
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I am with Macca on this.

Many years of experience has benefitted my perception that no battery enjoys heat. Also that typical deep-cycle batteries sold retail are harmed by regular discharge below 50% of their capacity. Some batteries are a bit better than others but what does vary greatly is the manufacturer's rhetoric.

Lifeline are better (and more expensive) batteries than some, but if quoting their publications it may be worth also to note their DISCLAIMER: ...........

"....... Concorde Battery Corporation makes no warranty of merchantability, fitness for any particular purpose, or any other warranty, expressed or implied, with respect to such information, and we assume no liability resulting from its use." ...........

No liability eh?

As to putting batteries in the engine bay, I would not even have the cranking battery there if I could avoid it.
The heat barrier in my Troopy was certainly helpful to both the cranking and AGM batteries but eventually I moved the AGM to the cabin but retained the heat barrier for the benefit of the cranking battery. This arrangement was worthwhile for battery life.

Cheers
Allan

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Follow Up By: Dennis Ellery - Thursday, May 06, 2021 at 12:03

Thursday, May 06, 2021 at 12:03
Macca do yourself a favour and do some research.
Google AGM DOD Chart and you will find many with similar figures to Lifeline.
AGM are lead acid batteries and are heavy.
If you are uncomfortable using an AGM to its capacity, buy yourself a LiFePO4 – you can’t go wrong
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Follow Up By: Member - McLaren3030 - Friday, May 07, 2021 at 08:07

Friday, May 07, 2021 at 08:07
I already have a 100 AmpHr LiFePo4 auxiliary battery in the back of my wagon thanks Dennis.

As for AGM’s being heavy, the average 100 AmpHr AGM will weigh around 35 kgs. The Lifeline AGM I looked at weighed in at 70+ kgs.

Macca.
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Follow Up By: Dennis Ellery - Friday, May 07, 2021 at 11:34

Friday, May 07, 2021 at 11:34
Oh my God, Macca.
70kg! they must be putting rocks in them these days.
My last 100ah Lifeline deep-cycle only weighed 28kg.
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Follow Up By: Member - McLaren3030 - Saturday, May 08, 2021 at 07:33

Saturday, May 08, 2021 at 07:33
Hi Dennis,

Just checked the website again, and the one I was looking at was a 200 AmpHr battery.

Macca.
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