Re: [mowbot] Battery Exchange ?

Dave Everett (Deverett nospam at
Wed, 25 Sep 1996 08:25:44 +1000

robin nospam at wrote:
> Monta Elkins <Monta nospam at> wrote:
> > What's a good 'battery charge' to 'run' ratio?
> > I'd guessed 2:1
> The small 3Ah lead-acid battery I had been thinking was a prime candidate
> needs a charge of 0.5A for 7h. The larger 6Ah version needs 0.5A for 13h.
> Assuming Mowbot runs at about 1A, that is close to 2:1.
> Much larger batteries can be charged faster, so perhaps we had better
> think of using these: for instance, a 24Ah battery recommends a 2.6A
> charge for 9h. Even if Mowbot is scaled up a bit and now needs 2A to run,
> that brings the charge/run ratio to better than 1:1. The down side is
> that this battery is much bigger and heavier and costs 60 pounds ($90).

If we can get 6v motors for all the drive components then we will get
almost double the amp/hour capacity for the same size and weight of 12v

On previous robots I have separated the logic and motor supplies this
[battery exchange]
> I had considered it in connection with the charging nest idea, but unless
> we are forced to deal with it, I would really rather avoid thinking
> about how to make 12V, 1A terminals reliable, detachable and gunk-proof.
> It's going to be hard enough to get the charging contacts reliable.

We don't need contacts, we could use inductive charging. The robot only
needs to be in close proximity to the charger (maybe a plate on the
Dave Everett.