Batteries again ... sorry!

[Mel B]

As I have almost lost the will to live by trying to keep up with some of the existing 'battery' threads (which have assaulted and 'battered' my brain cells!), can some one please advise me on the following.

 

When we get our new van next month, we are having cabling etc for a second leisure battery installed. The idea is to transfer our existing 110 amp battery (one year old and little used) to the new van, however, the new van will have an existing 85 amp battery installed as it's original leisure battery.

 

Question: Can I safely use my existing 110 amp battery alongside the new van's original 85 amp battery or will the mis-match cause problems?

 

Answers in words of one syllable please as my brain is still fried!

 

:D

[jhorsf]

both should be the same capacity and age

[spospe]

For best results both batteries should be of the same make, capacity, age and type of construction (both lead-acid, or both gel).

 

In principle, if they are of different capacities, then power will be drawn from them in the ratio of their capacities, i.e. in the case you have mentioned the ratio will be 85:110 (or if you prefer 1: 1.3)

 

You can mix them, but really it is not advised.

 

It is much easier to arrange good housekeeping by having batteries in series rather than parallel, but you would have to fit 2 x 6 volt items (no problems with uneven power draw, or charging when they are in series).

 

 

[Lord Raindrop]

My true battery knowledge is zero, but a cell is a cell in my book. I would assume different amp/hr batteries would combine in their output to suit the equipment demand.

 

Leisure batteries already send energy to engine batteries which have a different capacity.

 

However I would not attempt a connection unless advised to do so.

 

 

[weldted]

Hi, if you fit two batteries of different ratings the least efficient will bring the other one down to its level, if you have a new 85 amp hour one, and a year old 110 amp one I would not think there will be a lot of difference between the two. they should be connected negitive to negitive and positive to positive with an inline fuse near to the positive terminal of each battery, 20 amp should be ample. the reason I would put a fuse at each end of the connecting wire is that if the wire should get damaged and come into contact with the metal of the van and short to earth it needs a fuse at each end otherwise the current will flow from the non fused wire and could cause a fire. If the battery is of the wet lead acid or has a vent tube provision must be made to vent the gas that may be produced when charging away from the inside of the van usually by a tube through the floor, or if it is the type you can remove the tops to top up the water it needs to be in a battery box and again vented. Hydrogen gas is very explosive, and remember to secure the second battery. In an ideal world both batteries should be of the same capacity and age for the most efficient results, but by using what you all ready own will give you more capacity and when the time comes to renew you can then fit two the same.

[Clive]

Mel,

The simple answer is YES provided they are either both WET or both GEL.

Its not ideal but the compromise will not be that bad to worry about. I would!

 

C.

 

[Derek Uzzell]

Mel B

 

As I've said before, with two batteries connected in parallel Exide advises a small-to-large MAXIMUM capacity difference ratio of 1:3 (eg. 60Ah to 180Ah would be (just) alright, but not 60Ah to 200Ah), and an old-to-new age difference of no more than 1 year. So there should be no foreseeable problems with your two batteries capacity/age-wise.

 

Not sure whar type of leisure-battery Chausson uses, but it seems to be quite common with Continental Ford-based motorhomes to fit a smallish gel-type leisure-battery, often beneath a swivelling cab seat where its inaccessibilty makes the gel battery's no-maintenance requirement valuable. As Clive warns, you should not mix gel and non-gel types.

 

(For what it's worth, Auto-Sleepers has fitted a pair of different capacity leisure batteries as standard to several of its recent-ish models. Can't recall the exact difference ratio (60Ah:85Ah?), but it doesn't seem to have caused any complaints.)

[Guest Tracker]

Seeing as how you already have the battery Mel the very worst that can happen is that you don't get the capacity and duration that you hoped to get.

 

If that happens you may need to get a new battery but, until and unless, and as you may well get all the capacity you need, I would go with what you have.

 

No point in spending what you don't need to!