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General Asylum General audio topics that don't fit into specific categories. |
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In Reply to: Thoughts on battery power for amplifiers posted by Dave Kingsland on February 14, 2007 at 10:22:45:
Dave:Don't put lead-acid batteries in your home, unless you build a battery closet out of bricks and have a vent fan to the outdoors! A lead acid battery bank is not a good idea for home - batteries can gas under certain conditions and even explode. Lead acid batteries stll have the best service life, but they require technical maintenance and know how.
Lead-acid batteries are "supposedly" good for 2000-3000 cycles, but anyone who has owned a car knows if you DEEP cycle lead acid batteries too much (or just too deep one time) and then recharge too quickly, the plates don't reform properly and the thing does not hold a charge nearly as good if at all. Quality sealed gel cell batteries are only supposed to be good for 800 or so charging cycles, but are much safer to use. The only trick with with gels is that you need a PROPER CHARGING SYSTEM - NOT an AUTOMOTIVE charger. The charge rate on a lead-acid auto charger is way too high for gel cells and will wreck them (they will gas TOO if recharged too quickly, and being a sealed design, the excess gassing that happens as a result of charging to fast wrecks them.)
The way to get the convenience and safety of sealed gell cells is to purchase more amp-hours than you need for your listening levels and listening session duration. You're correct - this is easily calculated. The biggest factor is how much low frequency information is in your music. The more low frequency information, the more amps your going to draw, the sooner your battery will discharge, and cause the terminal voltage to drop off. The way to ENSURE you don't deep cycle your batteries is to put a voltage sensing relay on the DC bus so that you get a pilot light come on when the voltage drops below a certain level. If the red light is bugging you and coming on too soon, no problem. Don't lower the voltage setting on the relay, get a few more batteries!
There is no need to deep cycle the cells if you get enough of them. There is also no need to charge quickly. If you're like me, you shut off the stereo for bedtime and don't listen again for... almost 20 hours! (Due to that work thing...)
WARNING DIY GUYS!
Do not be fooled thinking "Ah, 12 Volts can't hurt me..." There is massive stored energy in batteries, and people are hurt, burned and killed every year for thinking this way. This is not one battery anymore - this is a battery bank, and there are very specific and mission critical guidelines (and code rules for commercial / industrial intallations) that need to be followed. I recommend building any battery bank to ALL code rules for battery banks even if these code rules are not specifically required in a domestic environment.
WARNING: NEVER connect one string of batteries to another string of batteries. The voltage difference between two series strings is very high, and can create an arc that can ignite batteries if they are gassing. This can cause a CATASTROPHIC chain reaction of exploding batteries. Always connect a battery string by adding "one cell at a time". [Connect cells 1+1+1+1+1+1+1+1 not (1+1+1+1) PLUS (1+1+1+1)]
Also with batteries:
-Use insulated tools
-Use heavy gauge insulated jumpers with crimp-on lugs
-Use fuse protection IMMEDIATELY after the DC bus
-Use the proper charging voltage / time
-Use an undervoltage relay to prolong battery life
-Use more batteries than you need to prolong battery life
-DO NOT use car batteries in your home***Use all information provided in this post at your own risk. Poster not liable for any damage resulting from the use of this information. Information provided 'as is' for discussion purposes only. Check with your local code authority or inspection branch before installing battery sytstems in your home. Have a qualified electrician or storage battery company install your system if you aren't sure. Sell your AC cables and use the money to do the job safely. Have an engineer or battery supply expert review your design and check:
-cell type, size, voltage of batteries
-connection method for desired voltage
-voltage range (Vcharged to Vdischarged or relay setting) is okay for load
-correct fuse type and size
-correct amapacity wiring, and wire type
-correct battery rack and storage area
-correct charging voltage and charging circuit
-correct undervoltage relay contact configuration
-optimal undervoltage relay settings for maximum cell life
-design optimized for human safety and long lifeCheers,
Presto
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Follow Ups
- Re: Thoughts on battery power for amplifiers - Presto 12:18:29 02/14/07 (0)
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