Campervan Batteries
Submitted: Thursday, Sep 29, 2011 at 20:57
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garrycol
I have a small Campervan that has its small battery (about 50Ah) mounted on the drawbar. The battery is a UPS battery and holds charge
well over time but is just a bit small. I also have a larger spare 120a/h UPS battery and intended to replace the smaller battery but UPS batteries are slightly taller than auto deep cycle batteries so will not fit in standard battery boxes. Also the camper has a fairly large ball weight for its size so I would prefer not to put more weight on the draw bar.
I have located a spot inside the camper next to the wheel arch that has an external vent where I could mount the larger battery. As all the current wiring in the camper originates from the small battery on the draw bar I am not keen on rewiring so would like to simply run some heavy wiring from the small battery on the draw bar to the big battery inside - effectively having the batteries in parallel.
So my question is - given the two batteries are of the same type, can I expect any issues having 40a/h and a 120a/h batteries connected in series being charged from a standard Anderson plug type connector from the car (or later solar panels) and the combined system powering the house electrics in the camper.
Thanks in advance
Cheers
Garry
Reply By: garrycol - Thursday, Sep 29, 2011 at 21:06
Thursday, Sep 29, 2011 at 21:06
"So my question is - given the two batteries are of the same type, can I expect any issues having 40a/h and a 120a/h batteries connected in series being charged from a standard Anderson plug type connector from the car (or later solar panels) and the combined system powering the house electrics in the camper."
Meant to say parallel not series.
AnswerID:
466346
Reply By: Sand Man (SA) - Friday, Sep 30, 2011 at 07:31
Friday, Sep 30, 2011 at 07:31
Hi Garry,
I see no problem with your logic.
The only problem in connecting batteries in parallel, is the possibility of a fault in one battery dragging the healthy one down.
Having said that, my camper has two batteries (of 80Ah each) connected in parallel in the same way as you are planning.
The only difference is that both of
mine are inside the camper (on opposite sides) and are maybe better protected from the weather, but if the one on the drawbar is inside a good quality battery box, you will have as sound a solution to increase Amp Hour capacity as is practical.
AnswerID:
466362
Reply By: Member - John and Val - Friday, Sep 30, 2011 at 08:26
Friday, Sep 30, 2011 at 08:26
Garry
Sounds fine, provided the batteries are similar, ie same construction, chemistry and similar age and usage. Gel and AGM batteries are commonly used in UPS applications - I wouldn't parallel Gel with AGM as the charging requirements differ, but paralleling gel with gel, or agm with agm should be fine. I wouldn't instal a wet battery inside the camper.
The usual precautions apply - as the batteries are
well seperated I'd instal a fuse in the positive line close to each battery, and as you suggest, use heavy cable to interconnect them. The usual constraints on charging will apply too - the voltage from the alternator is a bit low for the job (especially if a 3 way fridge is running through the same line from the vehicle), so either a dc-dc charger or solar to provide the higher voltage would be good.
Cheers
John | J and V
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AnswerID:
466371
Reply By: garrycol - Friday, Sep 30, 2011 at 15:54
Friday, Sep 30, 2011 at 15:54
Thanks for those replies - I will proceed as I have proposed and incorporate the points raised. The small original fit battery was probably large enough as it would have only been providing power to LED lighting and a small water pump - I will however also be using a 55l compressor fridge as a freezer and using the inbuilt 3 way for drinks and ice so the small battery is unlikey to be able to provide power for ore than a day with supplementary charging so an additional 120a/h will coe in handy.
Cheers and thanks
Garry
AnswerID:
466407
Follow Up By: Sand Man (SA) - Friday, Sep 30, 2011 at 18:11
Friday, Sep 30, 2011 at 18:11
Garry,
Just a word of caution with the 3 way fridge mate.
Don't attempt to run it on 12 volt for long while stationary. These fridges consume a considerable amount of electricity.
The 12 volt mode should only be used while travelling and swapped over to gas or 240 volt mains supply where available as soon as possible when setting up
camp.
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740511
Follow Up By: garrycol - Friday, Sep 30, 2011 at 19:20
Friday, Sep 30, 2011 at 19:20
Thanks Bill - on top of that -
mine uses 100watts so draws 8 amps.
Cheers
Garry
FollowupID:
740520
Reply By: garrycol - Saturday, Oct 01, 2011 at 10:08
Saturday, Oct 01, 2011 at 10:08
Hijacking my own thread a little - on the spur of the moment and without and research :-( I bought 120w of solar panels and a controller to charge these two batteries.
Now I understand there are two types - poly and mono with mono being more efficient. I have no idea what
mine are :-( as I bought
mine online and this was not covered in description - can I tell what I have by looking at them. The cells are have large round junctions so they look like they have large dots over them. Some cheaper ones which I assume are poly do not have these 'dots'just the internal wiring running vertical and horizontally.
The description does indicate efficiency to be >15%.
Thanks
Garry
AnswerID:
466480