# How to power electronic piano keyboard using SLA?

Greetings- Newbie here. I have a piano keyboard powered currently via ac to dc transformer regulated to 12vDC @ 700 milliamps. The AC power adapter connects to the keyboard via coax plug. I'd like to take the keyboard camping and have it powered by an SLA. How do I determine the size battery I need? Does a rating of 12V 7 amp hours indicate that the battery would supply, hypothetically, the 12 volts @ 1 amp (700 milliamps is the rated current draw of the piano) for 7 hrs?

Or is my understanding flawed?

Also, is there a practical way to recharge such an SLA via PV panel? Or would the panel be so expensive and cumbersome that it just wouldn't be worth it?

Thanks for any and all advice

Jeff

• Solar Expert Posts: 5,433 ✭✭✭✭
Re: How to power electronic piano keyboard using SLA?

The 700 ma is .7 amps, at 12vdc ~ 8.4 watts.

So a 7 amp hour battery would provide (theoretically) about 10 hours. That would assume that the battery was killed to dead!~ (no redundancy intended!) This is never a good idea, most suggest a max discharge of ~50%, some (including me) recommend on 20% discharge.

The short answer is there is no reason that you can't get the proper plug, and wire directly to a battery with clips, making sure you keep Plus to Plus, Neg to Neg. A 1 or 2 amp fuse should be installed. You could also make up a cigarrette lighter plug to prevent reverse polarity.

As for powering it from Pv, calculate the daily expected draw, lets say in this case, .7 amps*4 hours- 2.8 ah. In rough numbers you would like to get a Pv that would give you about 150% of that a day, or 4.2 ah.

So a 20 watt panel might give you ~1 amp amp* 4 would give you 4 ah day,, pretty close. Play with the numbers and see what happens.

Tony
Re: How to power electronic piano keyboard using SLA?

So it l as though if I wanted the keyboard to be active for a 3-4hr period between recharging the batt, a slightly larger ah rating would be called for in keeping with the 20% discharge figure.

re: PV.. I was inquiring about recharging the battery via PV..different than powering the keyboard directly from PV.

AM not familiar with the method of recharging SLA'a. Ideally, would like to charge the SLA during the day (will be in the desert sun), then use the battery at nite to power the keyboard.

What is the most efficient way to recharge a small 10ah SLA? What components are required? A regulator that would shunt the power when the battery reaches it's fully charged state I'd imagine.

Thanks for info.

Jeff
• Solar Expert Posts: 9,362 ✭✭✭✭✭
Re: How to power electronic piano keyboard using SLA?

For the cost, and everything, I'd look into a 20 or 30 AH AGM battery. Much more useful, and if you hung a 20-30W PV & charge controller on it, you would be all set to go all night, sleep all day, live forever. (whoops - wrong movie line)
Attached are some examples with small panels, large battery in a milkcrate, charge controller in a tool box....
You can also get a 'store bought' gizmo - a "Jump Start power pack" that has
a cig lighter outlet, DC charging cord, and small battery inside.
http://www.xantrex.com/web/id/245/p/1/pt/32/product.asp 10AH battery, 5W PV
http://www.xantrex.com/web/id/265/p/1/pt/7/product.asp 28AH battery, 12V I/O
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,

• Solar Expert Posts: 9,362 ✭✭✭✭✭
Re: How to power electronic piano keyboard using SLA?

Just a couple more ideas here:

(notice under the tool box latch, is a 12V cig outlet)
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,