Hi, I’ve got an existing Mars rover robot project that’s been designed around the PiBorg ThunderBorg motor controller, but these have sadly become unavailable. I’m considering using the Yukon Host board and six of the Big Motor driver boards. All looks good, but the voltage range on the Yukon is 5V-17V, and I’m using Makita power tool batteries that are listed as 18V but actually run up to ~21V when fully charged.
Any suggestions on how I could continue to use the Makita batteries with the Yukon? Thanks!
In theory you could use a step-down regulator to convert it to ~17V, but the problem then becomes current. At a glance, most of the regulators which would work here have current outputs of =<3A, which might not be enough for your needs. It might not be the best thing for that kind of battery?
Hi Shoe, yeah, most of the hobby buck converters aren’t really big enough to handle the whole project, which includes six motors. I’m sure there must be an industrial DC-DC converter but it’d probably cost more than the whole project. I’ve thought about dropped the battery to a 12 volt (Makita do both 18v and 12v) but then I both lose overall power and maximum Ah rating: the 18v has available a 6Ah battery, the 12v about half that (since they’re considerably smaller batteries).
I’m trying not to lose everything to heat as well so it probably needs to be a switcher of some sort. Pololu sell a D36V50F12 12v rated at 4.5A. I have no idea how one uses several of those (can you just parallel them? I guess that’s a question for the Pololu techs). Either two or three would do the trick I suppose if that’s possible.
That’s a fair point actually, do you know what the safe discharge rate is for the 6A batteries? I don’t know the ins and outs of multiple regulators, you might need to catch ZodiusInfuser here, he has done a lot of robotic stuff.
As for the safe discharge rate, one of the benefits of using commercial power tool batteries rather than raw cells is that they have internal regulator circuits for safety. So if you’re, e.g., using a power drill and lock it up, the battery isn’t going to explode on you. But to answer your question more explicitly, I don’t actually know. One of the downsides of using commercial power tool batteries is that manufacturers don’t generally publish detailed specifications as they I’m sure legally can’t sanction use of their batteries outside of their stated application as part of their power tools lineup.
I just got a reply from someone at Pololu, who said that they don’t recommend using multiple regulators in parallel, but did point me at the D24V150F12, a 12v 15A regulator (US$80) which would do the trick.