Dual Battery Options and Fitting

[Transporter]

Hi Mark, you only need to run positive wire from the main battery to power up the DC charger, then the ignition +12V sourced from the connector under the seat. Remove the plate behind the battery you will see the grommet there, through which you can run the wire into the cabin and under the carpet, under the seat. For battery up to 110CCA use up to 25A DCDC charger, otherwise you will cook your battery. Install the charger as close to second battery as possible.

[drivesafe]

Hi again folks and I am now a sponsor.

I have posted up some basic details of my business here

http://www.vwwatercooled.com/forums/f247/same-basic-info-about-our-products-122229.html#post1257627

I will be posting up more detailed info about my isolators in the near future, but if you have any questions, please ask away.

[heyasam]

First wanted to say I'm a long way off setting up dual batteries on my multivan. That aside the idea of using an isolator that adds some of the starter battery capacity to the house battery uses I think is interesting. Does that beg the question though what would be a good dual purpose battery for starting, and what battery could fit under a multivan seat that had an aftermarket swivel installed? Could a matching dual purpose battery fit under multivan seat? I would probably like to stay away from agm if feasible. I'll also at some point have to look into under seat mounting options, i read somewhere the standard tray can be modified to fit? Have a spare one of those now! Also saw the little kit that travel volts uk sells. Though like an earlier post suggested be good to have space to run wires through the floor, not sure if some mounting options prevent that?

[drivesafe]

Hi Heyasam, I am flat out at the moment but will go into more details shortly.


First off though, you do not need to replace your existing cranking battery with a multi purpose type battery. All cranking batteries can be safely and continuously cycled down to 40% without having any long term effects on the battery’s longevity.


Up until 15 or so years ago, when deep cycle batteries became more available and cost effective for RV use, cranking batteries were used as both auxiliary and house batteries and and worked quite well.


The only requirement when using a cranking battery as an auxiliary or house battery, is that you avoid cycling them below 40% SoC or 11.9v. Any lower and you may reduce the life span of a cranking battery.


BTW, CCA requirements are based on a cranking battery being able to supply the marked current rate with the battery discharged down to 40% SoC, at 0 degrees.


So your existing cranking battery is fine.


Not sure why you prefer not to use an AGM as your auxiliary battery?


Both AGMs and Lead Crystal batteries are idea for this type of setup.


Again, I will post up more info shortly, particularly about the VW “smart” alternator operation and how my isolators improve this system.

[heyasam]

Thanks look forward to more info. Just been unlucky with agm in the past, was able to return the battery in question fortunately. Seems that wet cell or others maybe more tolerant of different charging parameters, cheaper, can be topped up etc, though yes don't want to vent inside the van, ideally something with vent line you can run outside.

[Transporter]

Whatever battery you use, just remember that cranking battery voltage will fall too quick when used instead of the AGM deep cycle battery. The AGM batteries tolerate being cycled much better than your starting battery. I'm not talking about running an inverter of your starting battery for 10-15 minutes every day, and if that's the case then you'll be ok.

[drivesafe]

Hi Transporter and not sure what you are trying to state.


If I understand your post, you actually have it back to front.


There is no issue with using a cranking battery for an auxiliary or house battery, just don’t over discharge it.


On the other hand, unless an Deep Cycle AGM battery is specifically designed to also be able to be used as a cranking battery, there can be major issues if you use an AGM as a cranking battery. You can shorten their life span very quickly.


As for a cranking battery voltage “falling” quicker than an AGM. I have no idea where that comes from.


Most European vehicles come with a cranking battery that is marked in different terms for it’s cranking ability plus the Ah rating is also marked on them.


Point being, if a cranking battery is marked with an Ah, that Ah is exactly the same as the Ah marked on AGMs or any other type of lead acid battery.


For instance, if you have a cranking battery marked as a 69Ah battery, then it has the same capacity as a 69Ah AGM. The difference is that the cranking battery should not be discharged below 40% SoC, while the AGM can be discharged down to 20% SoC.


But if you were to place the same current load on each battery and allow them to discharge down to 40% SoC or 11.56v, the two batteries would discharge at exactly the same rate and take exactly the same time to get down to 11.56v.


The Ah rate means the same thing on all lead acid batteries used in the Automotive and RV industry.

[Transporter]

Hi Transporter and not sure what you are trying to state.


If I understand your post, you actually have it back to front.


There is no issue with using a cranking battery for an auxiliary or house battery, just don’t over discharge it.


On the other hand, unless an Deep Cycle AGM battery is specifically designed to also be able to be used as a cranking battery, there can be major issues if you use an AGM as a cranking battery. You can shorten their life span very quickly.


As for a cranking battery voltage “falling” quicker than an AGM. I have no idea where that comes from.


Most European vehicles come with a cranking battery that is marked in different terms for it’s cranking ability plus the Ah rating is also marked on them.


Point being, if a cranking battery is marked with an Ah, that Ah is exactly the same as the Ah marked on AGMs or any other type of lead acid battery.


For instance, if you have a cranking battery marked as a 69Ah battery, then it has the same capacity as a 69Ah AGM. The difference is that the cranking battery should not be discharged below 40% SoC, while the AGM can be discharged down to 20% SoC.


But if you were to place the same current load on each battery and allow them to discharge down to 40% SoC or 11.56v, the two batteries would discharge at exactly the same rate and take exactly the same time to get down to 11.56v.


The Ah rate means the same thing on all lead acid batteries used in the Automotive and RV industry.

How could it be back to front! You’re not trying to make full of me, are you?
The AGM battery will stay at 12.2V for longer and will drop voltage much slower when connected to appliances, than starting battery, will also recharge faster and tolerates deep discharges, hence the name deep cycle battery.
The AGM battery will have much longer life in place of second battery than the starting battery. The starting batteries aren’t usually used in second (dual) batteries setups, unless it’s a hard core 4x4 with the winch.

Only situation where the starting battery would be ok to use in the dual battery setups, would be if you don’t connect any appliances to it and even then the starting battery needs to be cycled properly by drawing starting current otherwise its life will be shorten anyway.
So, yes when installing second battery for actual use, the one will be always better of using the AGM battery. There are also AGM batteries that are deep cycle/starting type, if you intend to use it for occasional starting.

[drivesafe]

How could it be back to front! You’re not trying to make full of me, are you?

Hi again Transporter, and NO I am not trying to make a “full” of you.


You continuously post up erroneous statements and I have simply corrected them.


The info in my last post can be easily verified on any decent battery MANUFACTURER’S web site, and note, I highlighted MANUFACTURER’S because many people use the B/S found on many battery SELLER’S web sites.


Here is a battery State of Charge voltage table. This table is used to get a fairly accurate indication of a battery’s SoC while it is in use, with a moderate load.


As long as the current load is no more than 5% of the battery’s Ah then the table is quite useful.


This table applies to Wet Cell ( or FLOODED ) batteries, Maintenance Free batteries, Gel Cell batteries, AGMs and Lead Crystal batteries.


ALSO NOTE, this is NOT an OPEN CIRCUIT voltage chart. They are a totally different form of voltage to capacity reference system.

[Transporter]

So, is it a bs to select the AGM Deepcycle battery as a second battery for the van that runs ARB 60L fridge, inverter to run multiple appliances?

Do you consider Yuassa/Century Batteries decent battery manufacturer?

Why would the battery manufacturers bother to make all different type of batteries, if they all perform equally under all conditions as I understand from what you’re saying?
The battery manufacturers must have a lot of errorneous statements on their websites.

https://www.centurybatteries.com.au/content/documents/deep-cycle/dc-agm-c12-105da.pdf

[drivesafe]

Transporter, I have no idea what your agenda is, but it sure it’s one intended to help people on this thread.

First wanted to say I'm a long way off setting up dual batteries on my multivan. That aside the idea of using an isolator that adds some of the starter battery capacity to the house battery uses I think is interesting. Does that beg the question though what would be a good dual purpose battery for starting, and what battery could fit under a multivan seat that had an aftermarket swivel installed? Could a matching dual purpose battery fit under multivan seat? I would probably like to stay away from agm if feasible. I'll also at some point have to look into under seat mounting options, i read somewhere the standard tray can be modified to fit? Have a spare one of those now! Also saw the little kit that travel volts uk sells. Though like an earlier post suggested be good to have space to run wires through the floor, not sure if some mounting options prevent that?

Heysaman posted up a reply, where he was considering using a Dual Purpose battery because “he would like to stay away from AGM if feasible”


I simply replied that Heyasam did not need to change his existing cranking battery, because any cranking battery can be used for cycling purposes.


Transporter, you then posted up a load of crap about why YOU THINK cranking batteries can’t be used as for cycling purposes and now you are FALSELY claiming I reckon it is BS to use a deep cycle battery as an auxiliary battery.

So, is it a bs to select the AGM Deepcycle battery as a second battery for the van that runs ARB 60L fridge, inverter to run multiple appliances?

At no time have I made any such statement and as I sell Lead Crystal Batteries, a DEEP CYCLE battery, why would I make such a FALSE statement?

Transporter, you then ranted on about cranking batteries being used for winching, so could you tell us all just how many people in this thread will ever fit a winch to their Transporter, Multivan, Caravelle or Kombi.

It would be way less than 1% and while the other 99% would be after a setup to power their fridge, charge up some camera, phone or computer batteries, and possibly run some camp lights, and as such, a cranking battery would give them the same Ah operation as any deep cycle battery would, with the one caution being, not to over discharge the cranking battery.

It is the 99% of people on this thread that I have been addressing, who are you talking about?

[Transporter]

I haven’t ranted, check my post #81.
After which you said “I have it back to front” and that I continually post erroneous statements.

I only try to help those that come here asking questions about what’s the right battery to use as a second battery, and as far as I know the AGM deepcycle batteries last longer and tolerate deep cycling better, and I have noticed over the years that waste majority of people in this section of the forum are prepared to spend a bit more and get reliable setup.

Please read again my post where I used the winch as an example and it shouldn’t be taken out of the context.

[drivesafe]

Hi again Transporter and try reading your own posts, you are the one making false claims and I have already replied to them.

I'm not wasting my time and everybody else's by going round in circles with you.

Have a nice day.

[Bob Bob]

I have a 220AH Lithium (LiFePO4), 40A Redarc and 160/280W solar combo in my T5. Just some real world notes on compressor fridge vs thermoelectric cooler power usage. (A small compressor fridge can be 3x or more the price of a thermoelectric.)

For those that wish to do the maths and sizing... I use to have a Waeco 21L cooler/heater box that really only did a good job in cooler months. Generally speaking it would use 45W 24/7 continuously except for (slightly less) about 2-3 months of the year at night. This governed my solar and battery requirements, needing roughly 200W of solar panels on sunny days to break even (ie whilst not driving).

I replaced it with an Engel 14L compressor thing that uses 35W on and 6W off. At the moment with the thermostat at 2C and the ambient at 32C it is cycling 90 seconds on 120 seconds off, or roughly 15-17W if thought of in average terms. This is maybe 1/3 the Waeco's usage and really reflects in solar/battery needs. I use to "have" to drive at least 100km per day and park in the sun to keep the capacity up. Now I only need to drive about 30km per day and park in shade a lot more.


In engineering terms a compressor fridge is about 4x the efficiency of a thermoelectic/peltier.


Hope someone finds this helpful.

[TheKiwi]

In engineering terms a compressor fridge is about 4x the efficiency of a thermoelectic/peltier.


Hope someone finds this helpful.

That's really helpful as I'm currently looking at the different options available. Thank you Bob Bob.