Charging a 3rd battery - how?

That's what I do, simple, cheap and effective to charge the other bank of batteries off the aux under the bonnet.

Collyn, without starting an isolator war, after I had some problems with my Redarc battery Isolator I contacted Redarc and was E-mailed back by their CEO and I quote "we advise our customers about that" referring to the premice their battery isolator should only be used with two 'identical batteries' and not two 'different batteries', ie a Starter battery and a Deep Cycle battery as is stated on the installation specification sheet.
However he did state that their battery isolator was used in some mine site vehicles and had no apparent problems - but they did not run a fridge!

The full E-mail was, at the time, posted here on the EO forum, however it was quickly deleted, obviously it's contents were not meant for public viewing, so I will not repaste it here again today.

Mainey
Am most interested in your response (re email). Would you send it to me privately please. I will take the matter up directly with Redarc's CEO.
Collyn

Followup ID: 356991, Email from: Anthony kitel, Redarc CEO.

Mainey
Where posted - cannot locate it
Collyn

Ummm, as I originally posted it was removed very quickly, however fortunately I have retained a copy. (see how long it lasts this time, I will shorten the post)
FollowUp 6 of 6 posted 15 Feb 2005 at 21:18 - (followupID: 356991)
(Quote) In answer to your question:- In our discussions with a large battery manufacturer it was commented that it is IDEAL to use two IDENTICAL batteries in a dual battery system, and therefore we do pass that information on to our customers. We are UPDATING our website and we will REMOVE the confusion. Thanks for letting me know. (end quote)

The Redarc website was duly updated as was declared, with the previously shown Deep Cycle battery & Crank battery picture being eliminated to show two x 'batteries'.
Collyn, I believe Anthony kitel's integrity is beyond reproach.

Mainey
Thank you for the clarification

Like you I too believe that the integrity of Anthony Kittel (Redarc's CEO) is beyond reproach, but I do not think the comment has anything at all to do with the Redarc product - but simply that from a battery maker covering its backside - the comment refers to (what a battery maker sees) as an ideal situation only.

They all do this in case some turkey does something like paralleling a 120-volt Nicad with a 12 volt AGM or something . . . and blows up both plus himself to b- y and what's then left of him then sues the charger maker.

Far-fetched? Consider this: some years back an NT truckie connected the 240-volt mains supply across his 24-volt starter battery - assuming it would charge 10 times faster. Truly.

I have just now discussed this matter with Anthony and he confirms that my interpretation is correct. He is also aware of this response - and confirms his agreement.

In practice, as long as the batteries are of reasonably similar type, each will charge and discharge at a rate relative to their respective capacity. It is perfect OK to parallel for example a 100 AH and a 10 Ah battery.

As an extreme example I have for over six years had a 12 AH 48-volt battery paralleled across my 48-volt 680 Ah home system.
Collyn Rivers

Collyn,
You have said “but I do not think the comment has anything at all to do with the Redarc product – but simply that from a battery maker covering its backside – the comment refers to (what a battery maker sees) as an ideal situation only”

Collyn, may I offer another choice, as I was one of the two people involved in sending/receiving the original relevant E-mail information, I believe I can clarify the E-mail meanings accurately as I still have the original post to refresh memory :-)

As can be ascertained from their Email, Redarc clearly declare they “PASS THAT INFORMATION ON TO OUR CUSTOMERS” the information they declare they pass on is, it’s ‘ideal’ to use two ‘identical’ batteries, with their solenoid battery isolator, therefore conversely it can be stated, it’s obviously NOT ‘ideal’ to use two ‘different’ batteries as I was using!!

To actually understand the contents of Anthony’s E-mail to me as posted above, you would have to have first read my original E-mail to him.
The sole reason I had sent my E-mail to Redarc was because I was having problems charging my Deep Cycle battery and I was questioning Redarc about this, you say Anthony remembers this E-mail and I believe he possibly still has the original E-mail, that’s good, as then he will also be able to confirm what I have typed here!

When Anthony’s E-mail reply is read in context with my original E-mail sent to him, his comment “it is IDEAL to use two IDENTICAL batteries in a dual battery system, AND THEREFORE WE DO PASS THAT INFORMATION ON TO OUR CUSTOMERS” can be more easily understood, as he is referring to using two ‘different’ types of batteries, being a Deep Cycle and a Cranker battery.

When reading Anthony’s next comment; “We are UP-DATING our website and we will REMOVE the confusion.” It can be confirmed Redarc removed, with-in days, the Deep Cycle battery reference from their web site just as they declared they would in their E-mail to me, hence Anthony’s response to me “Thanks for letting me know” as is shown in his E-mail to me show’s there is/was no animosity between us in any way.

Collyn, you state above "In practice, as long as the batteries are of REASONABLY SIMILAR type, each will charge and discharge at a rate relative to their respective capacity.
It is perfect OK to parallel for example a 100 AH and a 10 Ah battery"

May I suggest a conventional Cranker wet cell battery is not a REASONABLY SIMILAR type to an AGM Deep Cycle battery and therefore will charge and also will discharge at very different rates when wired in parallel.

Mainey

I can only really say that I spoke to Anthony this morning. He believes that his comments only make sense if quoted fully in context. He is aware of my response, and that it was to be published here - and gave it his OK. (I'm sure you will appreciate I cannot really get deeply involved in discussing a full previous posting that was apparantly withdrawn and that I have only seen in part).

I don't fully agree with you that an starter battery and an AGM deep cycle battery are that different from each's charge/discharge point of view, except that one will fully charge at 14.2 or so volts - and the other one wont.

Both have high charge acceptance and ditto discharge capability. The AGM may grab more of the initial available charge but as long as the starter battery is protected by a voltage sensitive relay that switches only once above the safe battery starting voltage (about 13.6 volts) there is no real problem. The starter battery is normally up to that charge level in a minute or so anyway - and from thereon the AGM can take whatever the alternator/regulator permits. It is possible the starter
battery may discharge slightly through the relay - but as that cuts out long before there is any non-starting risk, this solves that one.

The AGM will charge at close to 100% charge, whilst the starter battery will be limited to not much over 70%. But the starter battery would have reached and remained at that same state of charge (as it is intended to do) and in the same length of time even had the AGM not been there. The AGM gets nicely charged without affecting the starter battery in any way - what's the problem?

It'swould be a different matter were the two batteries to be a conventional deep cycle battery and any AGM battery - but that's rare - and I'd normally advise against it unless that deep cycle battery too were voltage relay protected.

I believe this issue gets clouded because unless on does the actual sum, it is hard to realise just what a tiny amount of energy is drawn by a starter motor even when starting a big diesel. It's only about 500 amps for 2 seconds. Electrical pea-nuts! It's less than that needed to run a side light for a few minutes!

Replacing the energy used is a breeze.
Collyn Rivers

Mainey,

As per our private email I did some research and found the post has not been removed - it is located in thread 19729.

Thanks David, now Collyn will be able to read the thread in full, hopefully now he may also be able to understand how the comments do make sense when they are ‘quoted fully and in context’ as the relevant E-mail messages can now be read simultaneously, also it can be seen an almost exact same E-mail was also sent to two other respondents, therefore I would suggest it is not a once off E-mail at all, but a reply that’s very carefully and precisely worded, that shifts the responsibly of the statement onto an un-named third person!!

Collyn, Anthony was also very aware of the fact that his reply to me would be placed on a 4wd forum also, it’s actually mentioned in my E-mail to him, and I’m sure his response was designed with that in mind.

As to your comment, ““I don't FULLY agree with you that an starter battery and an AGM deep cycle battery are that different from each's charge/discharge point of view, except that one will fully charge at 14.2 or so volts - and the other one wont””

Ummm, Collyn, that is the point - they charge & also discharge differently!!!

If, they were 'identical' and did accept charge and discharge at the exact same rate then you would use the ‘cheaper’ battery, but fortunately AGM’s are an easier/better battery to use as a Deep Cycle battery simply because their construction and electrochemical characteristics enable them to charge much faster than a conventional Wet Cell battery, but you already know that, it’s in ‘the book’ :-)

* * * * *
(FollowUp ID: 353703) From NudeNUT
The answer to my question says:
in discussions with a large battery manufacturer it was commented that it is best to use identical batteries but Redarc do not request or require it.

(FollowUp ID: 355201) From Uncle
>In our discussions with a large battery manufacturer it was commented
>that it is best to use two identical batteries in a dual battery system.
>In practice however many of our customers are using two differing
>batteries (cranking battery and a deep cycle battery) and (like you)
>their systems have successfully operated over many years.

(followUp ID: 356991) From Mainey
(Quote) In answer to your question:-
In our discussions with a large battery manufacturer it was commented that it is ideal to use two identical batteries in a dual battery system and therefore we pass that information on to our customers. In practice however, the large majority of our customers are using two differing batteries (cranking battery and a deep cycle battery) and their systems have and continue to successfully operate over many years.
We are UPDATING our website and we will REMOVE the confusion.
Thanks for letting me know.(end quote)

I’m not sure why the “battery manufacturer” has to be quoted as to the working or possibly not working of a Redarc solenoid when Redarc is asked a direct question about their own product, as in each E-mail received (above) it can be clearly be seen the “battery manufacturer” is quoted as the responsible entity making the technical decision in each and every reply sent to those who took the time and also made the effort to ask the same question of Redarc.

The only difference is;
in my reply, Redarc actually declare they “would remove the confusion” shown on their website, and they actually deleted the ‘Deep Cycle battery’ from the diagram shown there, replacing it with an ‘auxiliary battery’
I did not ask them to do this, I asked them only to clarify the situation as to if a Deep Cycle battery could be used with a Start battery with their Solenoid isolator, nothing else, this change to their website was obviously their way of “removing the confusion” as they put it.

I believe by taking this deliberate action Redarc have actually shown their battery isolator as it is recommended to be used - by them, after all it’s their advice and their website, not a ‘battery manufacturers’ and not your’s or mine either, L0L.

As I said in my original post, I was not looking for an argument.

I have presented the available “written facts”, as can be read in the various E-mails which were produced by the other respondents, myself and Redarc on the same subject as is shown in the link to the relevant thread recently found by David.

Therefore, I believe this readily clears up any misunderstandings!

Think carefully about the size of wire to use from Engine compartment to Trailer Battery.

It needs to be a MINIMUM of 8Ga - i.e. the diameter of the copper at least 4mm - if you want the Trailer battery to charge in minimum time.

Mike

I go along with all of that.
Collyn

Norm,

Thanks.

Looks like AGms are the go for the trailer.
Didn't think about running a cable back to the car for the fridge, good idea.
We get about 3 to 4 days out of the N70ZZ.

I do have a solar panel. 80w, but am trying to cut down on what we carry! Where to mount it so it is safe and doesn't get too dusty.
Usually start the car every few days anyway for touring.

Need to get the alternator checked too if I do this. 260,000 since new and untouched. May be expecting too much from an old alternator.

No worries OP. I did heaps of reading before I did mine, including a lot written by Collyn. He knows his stuff and I'm happy I was able to absorb some of it.

If you do the cable yourself, go to an electrical wholesaler. Much cheaper. The cable I used is about 25mm squared (each cable is about 10mm diameter) but has thousands of tiny copper strands so it still very easy to work with and bend through the chassis. Probably a bit bigger than necessary, but not much more expensive. Lots of people have trouble from cable too thin. Never heard of a problem from cable too thick.

I used the plastic tongue from floor sheets (pick it up off building sites where they are doing plywood or chipboard floors) to put through the chassis and taped the cable to it to pull through.

If you are not familiar with AGMs, this web site is a great place to start:
http://www.fridge-and-solar.net/batteries.htm

I bought my Fullriver AGMs from them. About $300 each for 120AH, so not cheap. But worth it I reckon. Val (male) who runs the business is very helpful. Even if you don't buy from him he will give good advice.

Collyn,
are you now suggesting the E-mail sent to me from Redarc is not authentic ?