Gentle Friends,
All this talk about Solo's and PAs and older models and no batteries and so on got the best of me. I decided to crack open my Solo again and do some poking around. I have a couple of VV PAs here (older prototypes) and the 'right' connector for the battery pack (be careful here, guys, Arizer reversed the polarity normally used for some reason). This let me do some interesting stuff (to me anyway) that I think lends some insights to the Solo and also puts some bad information to rest.
First off, the fully charge battery pack (I pulled it the instant I noticed the charge light go solid) was 8.31 Volts by the time I got it out and measured it. I took this to be top of the range and set the power supply feeding the battery connector to this value at turned it one. First to calibrate the 'battery meter'. I did a 'run down' series, dropping the input by .1 Volts a time, stopping and starting the Solo to see what the battery indicator said. Here's the very interesting results. The meter on the PS only had one tenth Volt resolution but the results kind of speak for themselves, even if adding more questions:
8.3 to 8.0 shows step 7
7.9 step 6
7.8 step 5
7.7 step 4
7.6 step 3
7.5 step 2
7.4 step 1
7.2 and below no lights.
Then, on a whim, I backed it down still more, unrealistically low to see if it would 'drop out', it didn't. Once running at 7.2 I was able to lower it to 5.0 Volts, the LEDs dimmed a lot but it would still set temperature and try to heat! This confirms something I thought I saw 'from outside', the Solo processor only samples some things (like real battery voltage) at the start in some cases. Anyway, from this we can see why we seem to get extra battery life from step 7....Solo has compressed the top step. It also shows why the 'one LED per session' thing is so common and also points out that the scale is definitely rigged. 7.2 Volts total is 3.6 per cell in the battery, what's typically considered 'half charged'! So the theory that Arizer 'bent the curve' some to get us to not discharge too deeply seems supported. Batteries of this class should still give excellent service down to 3.3 Volts per cell or so, 5 or 6 steps below 'no lights left'. How wise that is is another matter. This also confirms some anecdotal evidence put forward by some Members?
There are 'many sessions left'. Use them at your own risk (or should that be risk of your Solo's battery?).
Then to reconfirm what I saw before in terms of battery current draw. There's a very minor load idling and setting heat levels but when you fire up the heater the current rockets over 2.5 Amps (with a 8.3 Volt 'battery') and quickly drops to 2 or a bit less (maybe five seconds?). When the heater shuts down, current immediately drops to about .01 Amp.
Finally, to the main event. What gives with PA power?
So this one is hard to measure in a repeatable way. Things shift around a lot, especially as more or less current comes from the battery (and therefore not from the PA). After some playing around I adopted a procedure where I'd set the 'battery' voltage, lower the PA voltage until the 'battery' was supplying several tenths of an Amp then slowly increase the PA voltage until that current passes back through .1 Amps again. Not perhaps the most accurate way to measure, but repeatable and it gave useful data I think. Again, this is the chart of what PA voltage is when it uses less than .1 Amp of battery power when the heater is on:
7.4 Volt battery needed 7.3 from the PA
7.7 needed 7.7 Volts
7.9 needed 7.9
8.1 needed 8.2
8.2 needed 8.3
8.3 needed 8.4
So as the battery goes down, so does the 'changeover', they track which makes some sense. It also means a 'power hog' PA (one that discharges the Solo battery quickly in PA mode) can 'fix itself' at some point as the battery in the Solo discharges. Take, for instance, the case where the PA is putting out 8.0 Volts. When the battery is fully charged, this will mean high discharge rates for the battery, until it gets down to about 8.0 Volts as well. Then it will start to taper off on it's demand for battery power. By the time the battery gets down to one or no lights left it should be basically not using any battery power, running exclusively from the PA. That is, of course, very subject to the battery voltage as well. Not a simple answer for sure. It looks to me like for maximum battery life you want a PA near the top of the acceptable PA range (7 to 9 Volts). The danger is, of course, go a little too high and it will tilt out on you. Lower voltage just means it shifts to 'PA power only' later on the battery discharge curve, perhaps even in the 'no lights lit range'.
I guess I'm even less concerned now that before since most any PA will carry the full load (or nearly so) as the battery level drops low enough. This needs to be tested again I think, but that's my take on it at this point. Doing the real test, PA session after PA session until it fails could not only take a very long time as the percentage of power from the battery drops to near zero but that could be hard on the battery by deep discharge.
One final fun thing. Once it was heating normally I turned the 'battery' voltage down and
it kept going! I unplugged the supply, leaving only the PA power, and
it ran fine. So you know what comes next......yes, you can plug in (at least this)
Solo with no battery inside to a PA,
turn it on and run it. This too needs retesting a time or two but it seems that 'conventional wisdom' is wrong, Samsquanch's
claim about
102 working with no battery not only confirmed but it
applies to other models? The 'why did they go backwards?' concern I had was based on bad information it seems, my guess is they all do it.
I'm going to need some time to digest this good stuff, and will probably redo much of it (including trying to start up with low 'battery' voltages). But now you know as much as me.
Thanks for your kind attention.
OF