confused? can i or can't i run different types together

Submitted: Sunday, May 07, 2006 at 07:50
ThreadID: 33630 Views:2175 Replies:7 FollowUps:3
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so much conflicting info regarding what you can and can;t do with batteries
want to know if i can parrell my aux batts ,agm (under bonnet)and standard acid dc (camper) asimple yes or no would great .
p.s similar size and age

cheers tony
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Reply By: Peter 2 - Sunday, May 07, 2006 at 08:08

Sunday, May 07, 2006 at 08:08
Like anything you want to do you probabaly can but you may not like the results.
Personally I wouldn't due to at least two factors.
They are a long way apart, one in the camper and one in the engine bay, you would need full size battery cables to connect them which would cost more than the battery.
Different types, sizes and age batteries are best not connected in parallel as one ends up doing most of the 'work' and the other carks it eventually.
AnswerID: 171243

Follow Up By: Marc - Sunday, May 07, 2006 at 19:59

Sunday, May 07, 2006 at 19:59
save the hassles and buy a $70 switching device. With mine it won't charge the camper till the main is 13.4v and disconnects when it gets to below 12.8
No worries with this and its less than 2 cases
FollowupID: 426813

Reply By: Mad Dog (Australia) - Sunday, May 07, 2006 at 08:21

Sunday, May 07, 2006 at 08:21
If the batteries will be part time paralled ie..disconnected when not under charge, then yes you can hook up different types of lead acid batteries in parallel sucessfully.
AnswerID: 171244

Reply By: MartyB - Sunday, May 07, 2006 at 08:38

Sunday, May 07, 2006 at 08:38
Yes you can.
Is that the simple answer you wanted.
I have an AGM & a Calcium under the bonnet of my car, been there over 2 years with no problems. I connect the AGM in my camper to these 2. AGM in camper is 3 times the size of the AGM under the bonnet.
There seems to be a lot of people who carry on that current might flow into or out of a battery, simple fact is that is what batteries are made to do.

from Marty.
AnswerID: 171245

Reply By: Mainey (WA) - Sunday, May 07, 2006 at 12:20

Sunday, May 07, 2006 at 12:20

You want to know if you can parallel your two AUX batteries?
an AGM under bonnet and standard lead/acid Deep Cycle in the camper ??

You ask for a simple yes or no reply!!

Yes, you can parallel them :-(

However, I would NEVER even consider that scenario !!!

But that's getting away from your simple yes/no answer you wanted.
I can't say no, because you can actually connect the two batteries together, they may not work correctly but that was not the question - was it?

You say they are similar size and age, yes maybe they are!
I bet they are both black in colour and an oblong shape with terminals at the top, sure they are both the same appearance, however they both have totally different internal construction !!

my suggestion - don't do it !!!
Ask another question - who has that same battery combination presently connected in PARALLEL and is happy enough with it to actually recommend it to you!!
AnswerID: 171276

Follow Up By: Member - Mike DID - Sunday, May 07, 2006 at 14:54

Sunday, May 07, 2006 at 14:54
If you can't explain why it won't work then I don't think anyone will believe you.

FollowupID: 426767

Follow Up By: Mainey (WA) - Monday, May 08, 2006 at 09:34

Monday, May 08, 2006 at 09:34
Tony’s post asked specifically for either a simple " yes " or a " no " reply :-)
and not a detailed explanation of basic battery functioning methodology

0ther posts mentioned some of the reasons why it should not be done!!!
FollowupID: 426885

Reply By: Alloy c/t - Sunday, May 07, 2006 at 13:13

Sunday, May 07, 2006 at 13:13
Yes you can ,dont get all pedantic like some others about batteries ,there are more so called experts on batteries on this forum than there are battery manufacturers world wide ,,did exactly what you are proposing several years ago and had all the doom and gloom sayers tell me then its bad ect ect ,, cr-p , I still have the original AGM now 6yrs old , gave my original deep cycle away when bought new camper ,that batt is still going strong in mates c/t [our old c/t] ,,,doom and gloom ,,
AnswerID: 171284

Reply By: Member - Jeff M (WA) - Sunday, May 07, 2006 at 13:51

Sunday, May 07, 2006 at 13:51
Yes you can.

It won't work as well as two of the exact same type and age, but hey it will still work.

The only thing I would suggest is to ensure that when you connect them together (ie, plug the trailer in). Try to ensure that they are both charged.

ie. Don't have the camper dead flat and the AGM fully charged as the flat battery will try and equalise with the charged one.

Two problems will come of this:
1. The batteries will potentially be damaged from the extreme amps being taken out of the full one and being charged into the flat one.

2. The cabling between the two batteries is probally not sufficuant/rated to handle those kinds of amps/current.

If you did have one discharged battery and one full battery you could always start the car and have the alternator charging the AGM, then plug in the DC. That way the DC will be drawing it's charge from the alternator, not trying to equalise with the other battery.

You will of course then need to leave the car running sufficiant time to charge both batteries to the same kind of level so that when you turn the car off they don't have to do a huge equalisation. If they are in a similar charged state, they will still equalize, but it won't be as bigger strain on the gear.

Hope that makes sense.

The other way around it (but may not be ideal if you are trying to get more run time by having the two batteries together) is to install a simple solinoid or high amp relay (like an arrid or redarc) so that even if you plug the trailer into the car with the engine off, it won't connect the two batteries together until the engine is running and the alternator is charging.

(yes I'm one of these try hard battery experts on here). Just done my bit of experimenting and research with my own setups.
AnswerID: 171289

Reply By: Member - Tony W (VIC) - Monday, May 08, 2006 at 20:24

Monday, May 08, 2006 at 20:24
thanks to all responded , sounds if i just have them parrelled while driving and dont let the c/t dc cycle get to low it might work.
thanks tony
AnswerID: 171591

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