There is an RC car company that produces 7.4 volt, 4800 mah lithium polymer batteries, I am interested in the increased run time and power offered by these battery batteries, would the increased volatage and run time fry my SSC-32? The basic Stamp-2 that is plugged into it?
Thaks.
Nope.
I use a battery that gets up to about 8V when overcharged.
Volts are what you have to worry about.
However, I wouldn’t set VS (servo power) = VL (logic power), because the logic power is regulated.
Let’s just say that I’ve fried my share of voltage regulators.
Anyhow, moral of the story is…
Plug a 9V into VL.
Make sure that the VS=VL jumper is off.
And plug your LiPo into VS.
By the way…
You are aware that LiPo’s must not be drained past a certain point, and that they must be charged with a special charger, right?
Just wanted to make sure…
Lack of knowledge there would put you out of a lot of money.
Nick R, lack of knowledge about proper handling of LiPo packs can put you out a lot more then some money. Do a web search for LiPo fire and take a look at some of the pics. It doesn’t happen a lot but when it does happen it aint usually pretty.
I do not know the answer to the SSC-32 question (I suspect Nick has answered it) but I am going to throw out a LiPo caution comment and some thoughts I have had about applying LiPos to hobby robotics. This speel is from R/C aircraft experience which, in my opinion, is much more specific in terms of load and power requirements than hobby robotics.
You need to understand up front that LiPo cells and packs need to be handled with care. If you manage to catch one on fire, which can happen in a couple of abuse situations, you can not extinguish it because it provides both its own fuel and oxidizer. The typical solution is getting into a bucket of sand and letting it burn itself out for a week or two. You need to know what your sustained max current draw can be in your robot and be certain your pack is rated for that draw. Usually this is specified by the pack as so many “C” where “C” is the pack capacity. A 10C rated 2400 mAHr (2.4 ampere-hour) pack is rated to provide a peak of 24 amperes, usually in short bursts. “C” rating is a marketing sell point so take any number they give you with a grain of salt and research the pack to find out what the real number probably is. If you overdraw LiPo cells (or to Nick’s point over discharge as well) you can damage them, which reduces their capacity. This plays into the next detail which is you need to charge LiPo packs with a charger specificly design to charge LiPo packs, which implies it allows you to set the charging current to the pack rating. If you charge a LiPo pack at significantly greater than its rated current or allow the charge voltage to exceed 4.2 volts / cell it will get very hot and you risk self ignition. Here you see the problem with cell damage, either due to over discharge or physical impact, as it reduces the capacity of the cell to some unknown value and when you go to charge it you can potentially cause it to ignite. Most R/C plane guys go out of their way to charge packs in fire proof bunkers or locations where nothing else is around to burn, and like the number one rule (that was pounded into my head) is never charge the packs unattended. An ignited pack burns really hot and can do a lot of damage.
So much for the doom and gloom soap box. Here is some engineering thought about applying LiPo packs to hobby robotics. The biggest drawback I see in using LiPo packs for robotics is the wildly varying current loads represented by a dozen or more servos generally running in a “hold” or load mode rather than sitting in idle position. In R/C planes most LiPo friendly ESC have both current limit and low voltage cutoff. Neither of these precautions exist in many simple robot controls, leaving the “problem” to be solved by the user if they are even aware of it. If the servo equipment will handle the slightly higher voltage of a 7.4V (2S) pack, you size the pack using something like you worst case servo stall current X the number of load bearing servos in your robot, you make the effort to make sure the pack never discharges below the cell cutoff voltage by adding a voltage monitor and checking it in software, and you are careful about how you handle and charge them then you will find they offer exceptional energy capacity at a fraction of the weight of NiMH or NiCd packs.
If you are NOT ready to do the work to make your application safe to use LiPo packs then you might want to pass on LiPo and stick with the tried and true solutions. 
A fully charged 2 cell LiPo that’s labelled 7.4V will come off the charger at 9.2V. That will probably destroy your servos without some sort of regulation. If you try to regulate down to with something like the HD regulator Lynx sells, you’ll lose the lower end of the discharge curve because of the dropout voltage of the regulator (shut them down at 3V/cell=6V is below your 6V+DropOut).
In my bot I use a 3cell 11.1V LiPo pack with switching regulators. The setup is great if you can get it working, but it’s not easy or cheap to do so.
The other guys have given great advice about using lithiums.
I would summarize the main recommendations as follows:
- Only use a charger that is correct for the particular lithium battery you are using. Don’t guess.
- Avoid ‘fast charging’ if possible.
- Include a fuse that is permanently connected directly to the battery pack, to protect you from accidental high currents during charge or discharge. Use the right size fuse, and if it blows, find out why.
- Use a HW circuit and/or SW to monitor the battery voltage. Never let the V go below 3.05V per cell.
- If cells will be connected in parallel, make them permanently connected that way. Do NOT charge individual cells, then plug them in parallel with other cells.
- Do not try to solder directly to a cell. Use a cell that has wires or tabs connected at the factory.
- Do not wire your circuit so that an external power source (such as an AC supply or wall-wart) can inadvertently ‘charge’ your battery.
Pete
Btw, Pete, did you ever get the LiPo circuit board that you were once planning going?
I tried to find the thread, but you know how good this forum’s search is.
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No, I ended up going NiMH for now, since the batteries and chargers are dirt cheap. For $25 at Wal-Mart, I got the equivalent of 6.25 V, 2500 mA/h, and a charger.
Pete
Hehe, true enough.
I’m thinking that LiPo’s aren’t worth their hassle and expense, unless you know what you’re doing.
And I definitely don’t.
So since I am kindof a noob to the whole hexaod business I should just stick with the Nimh packs everyone knows and loves? Thanx guys for all the help. 
I’d suggest doing so.
NiMh are pretty reliable, and take a beating well.
You’ll find that most of the initial problems that you run into with servo robotics deal with power issues.
So, it’s a good idea to get something reliable to start off with.
Besides, the only real advantage to Lithium is weight.
With a hexapod, you have a lot more weight-bearing capacity than… say… a biped.
In essence, the amount of money that you’d spend on a LiPo would be better spent on stronger servos, more sensors, etc…
Well that is not exactly correct, or maybe I should say it does not completely paint the full picture. While it is true you can get the same amount of power at a lower weight, the reason is that the energy density for Lithium-Ion based cells (LiPo being Lithium Ion Polymer) is nearly 2x that of NiMH based cells. For the same capacity pack what is actually lower is your pack volume. So not only do you see a reduction in weight you also take up less space. I think though in reality that some of that volume savings is lost due to the protective packaging and terminations required for LiPo pack construction. The best bet to minimize that impact is if you can get cells with the required current capability so you don’t have to build parallel strings of them. 