Lipo power for Telescopes

[Sunshine]

Looks like my Lipo project so far may be working good, ran a trial last night with a 3200Mah 3 cell Lipo from my RC airplane, the battery is an 11.1V nominal charge (uncharged) but charges up to 12.6V (4.2V per cell fully charged). All Lipo batteries display nominal charge capacity, which can be misleading because when charged, they jump up in voltage past displayed voltage.

I wanted to see how long that went for before using one of my larger 5000Mah batts, didn’t take much more than $5 for a 2.5mm connector with 6ft cable included and a Deans connector on other end for the battery. I have a small voltage meter we RC guys use to monitor battery levels per cell and combined voltage, meter just keeps displaying levels constantly then emits a buzz when it drops to pre programmed level. The loud buzz I muffled to a pitiful hum by dropping some hot glue over the little speaker holes, last thing I need is an 80 decibel buzz at 2am in my yard.

I set buzz for 3.5V per cell which is lowest you want to drain a Lipo per cell, after slewing around manually more times than I can remember I still had enough juice to slew around for another hour if i wanted, I was mimicking a nights slewing around and I think after I slewed around  on both axis simultaneously on and off for 40 min I pretty much covered a nights worth.

the test will be in the field, if this battery doesn’t cut it I’m sure the 5000Mah will do the trick. I was watching for any shenanigans from the scope as the level dropped but nothing, no glitches or twitching of the controller display, all remained solid.

UPDATE: 

The next morning i turned on the scope (without recharging battery)  and again spent the better part of an hour until i was just bored slewing the scope around, i was afraid to burn out a motor with constant back and forth slewing with a short pause of course.

i am now convinced that this 3200mah battery not much bigger than the average candy bar will last a whole night out and more! fantastic to know that when i drag the scope out for short periods locally (won't need heat strip those times) that this battery will be fine.

i was dreading having to take my 50Lb deep cycle marine battery every time id like to go for a short local 2hr outreach session, on those long drive dark sky all night sessions yes i will need heat and my marine battery but those a few compared to 

short local sessions. I can now fit my power supply into my pocket and that is just GOLD!!

[lux eterna]

Nice idea and implementation. The label says "11.1 V", and 3 x 3.5V = 10.5V... how low can you go with that Meade thing ?

Ragnar

[Mick J]

Nice stuff,  you may be pushing it on a NEQ6 that seems to like over 12V but I am sure that would be easy to overcome. I think if you are Radio Control savvy Lipo & Lifepo should be no problem,  charge properly, don't over discharge or short and all that.  Nice light solution and you can fly in the daylight and power your mount at night,  one hour recharge ?

[Sunshine]

8 hours ago, lux eterna said:

Nice idea and implementation. The label says "11.1 V", and 3 x 3.5V = 10.5V... how low can you go with that Meade thing

Sorry I didn’t reply earlier, the 11.1V is nominal charge, that basically means discharged, when an 11.1V lipo is charged it goes up to 12.6V which is 4.2V per cell, notice the volt meter in the picture is displaying 12.5V. It took over an hour's worth of slewing to drop it from 12.6 down to 11.5V,  I have gone as low as 11.3 and haven’t had any issue from the scope, that took over an hour solid slewing which is a lot more that one would do in a night. One may slew here and there maybe 10-20 times a night, I tested with enough slewing to account for several nights worth.

[Sunshine]

6 hours ago, Mick J said:

Nice stuff,  you may be pushing it on a NEQ6 that seems to like over 12V but I am sure that would be easy to overcome. I think if you are Radio Control savvy Lipo & Lifepo should be no problem,  charge properly, don't over discharge or short and all that.  Nice light solution and you can fly in the daylight and power your mount at night,  one hour recharge ?

 Keep in mind that 11.1 Volts as displayed on battery is nominal charge, uncharged, when charged it goes up to 12.6V, and during an hours worth of slewing it only dropped back down to 11.5V. if an EQ6 required more voltage I would use a 4 cell battery at (16.8V charged) and a small voltage regulator to bring down to desired range. Lately I have even tested my 6600 milli amp battery for heat with success, used a firefly strip, I needed my strip for 1.5 hours one night and the battery held up like a champion. 

I am excited about all this because I powered my scope with heat and fit both batteries into my pockets which is awesome. Even if I find that the 6600 Mah batt is not enough for several hours of heat I can couple 2 in parallel easily and double the Mah’s While maintaining the same voltage.

having flown RC aircraft for years I have many Lipo packs around and treat them well with proper charge and storage procedures, they are volatile but pack a huge punch when needed, my 3200 Mah can drain at 97 amps if needed.

[animal666]

I have a similar setup but I used LiFePo4  RC batteries.

3.2v per cell so 4Cell gets me 13.6v fully charged.

I can go down to 11.6v before they’re Dead, but I have a cutoff set at 12v.

i have 8 x 4200Mah (33.6ah) in a Box with a Voltage Cutoff and lots of power outputs.

 

be carefully using Lipo/LiFePo batteries. If you take them below the design voltage, they release gas, balloon up and then you get rid of them.

[Sunshine]

On 13/04/2018 at 15:18, animal666 said:

be carefully using Lipo/LiFePo batteries. If you take them below the design voltage, they release gas, balloon up and then you get rid of them.

Nice power pack you have there! and yes, as an avid RC flyer i am well aware of the minimum voltage you can take a Lipo down to, i rarely drain my Lipo's in my planes below 3.5V per cell.

[nightfisher]

Great project, i did same thing for my EQ5 that has dual tracking motors, but of course this use`s 6v, so i made up a lead with a 6v Ubec between the lipo and the mount, i use an 1800mah 2s 7.4v lipo since the mount is used mainly for tracking and not slewing