Can you use 3 12v batteries with 2 12v motors?

[Tufty]

Hi Gavin,

Your partly right, putting 2 batteries in parallel does give the same effect as a single battery with a higher a/hr capacity.
However having 2 batteries of different a/hr capacities in seris (which is basically what your doing) isn't good practice for a number of reasons.
They will discharge at different rates, the lower a/hr (single) battery will discharge quicker and it's voltage will drop quicker. This will cause imbalance in the batteries.
Also charging, in the same way as the single battery will discharge faster it will charge at a different rate to the pair of batteries, again causing imbalance. I believe it will cause the batteries life span to decrease.
However if room permits 4 batteries (paired in parallel and then in series) of the same a/hr capacity will be fine (you may need a trailer)    
Or a pair of larger capacity batteries!

[gavinbailey]

That's useful to know - thanks!  Not as simple as I thought.  There's not room under the 'bonnet' for another 2 batteries of the same type - measuring up I could only just squeeze one in.  There may be space in the motor compartment under the seat.  Alternatively I might have to wait until the existing set expire and replace them with a matched set of higher am/hr capacity.........

[bill shuter]

other point of note is if you have one battery weaker than the other it will take power from the good one. Again causing possible imbalance.

[multisync]

Hi
All good valid points there, putting any two batteries in parallel is always bad practice, one will always be slightly different voltage to the other and they will discharge into each other when motor is idle, so reducing the capacity. Secondly when using what is basically two batteries of differing capacities, the current will drop to and unusable level when the smaller battery is exhausted, so the extra capacity will never come into use. The best options are either a pair of higher capacity batteries, which will give a longer run time of course, or a second pair which could be of much smaller capacity and used as "reserve" for a get you home solution. However the smaller batteries are less efficient at high currents.
Hope this doesn't confuse the issue
Best wishes
Walter

[gavinbailey]

[Richard]

Hi Gavin,
Battery space: you should be able to fit a second set under the seat but you will need to make well to sit them in. If you carry this out you will be the first person with a standard set up that I know of you must be really giving the Toylander some good exercise. If you wish to go for larger batteries please ask me first and I'll see what I can get for you from my supplier. Please keep me informed about your usage and please check that the charger is getting a full go at charging before the Toylander is on the road again.
BW's Richard

[gavinbailey]

Richard - thanks for the tips.  The Toylander is always on charge when we're not using it so the batteries will be fully charged up.  We do tend to take it on fairly long trips so it would be good to have the extra capacity to increase the range.  I think I'd prefer higher capacity batteries under the bonnet and having looked at a few websites the standard batteries are avaliable in a slightly larger capacity and I think the larger ones would still fit in under the bonnet.

I think I'll wait a little while until the ones I have need changing before upgrading unless anyone fancies taking my existing batteries off my hands