Recently a shopper in Winchester walked diagonally straight through the area which some other Christians had marked out for prayer in order to reach a bank quicker. An unbeliever, she couldn't work out why the pain she'd had for a while suddenly disappeared as she passed through.
Earlier this year , while in Cornwall, I was struck by this bunch busking. What a great sound!
Then, in Havant, the Portsmouth Family Church took over the park for a Saturday and had a couple of really really talented singers doing up to the minute covers, plus related Christian stuff.
Here is a post from an extremely useful blog by a busker who describes the ins and outs of what you need, and what it's like busking. I thought this all served as useful inspiration and material for street sharing purposes.
Battery Guide
There
are many different types of battery you can use to power your
equipment, ranging from small 6v hand held rechargeables for small
busking amps to huge deep cycle RV and forklift batteries capable of
powering full out door gigs and lighting systems. They all have
different uses and characteristics which you should be aware of before
you design your power system.
We’ll start with the smallest.
Smaller equipment such as busking amps,
battery powered fx pedals, stereo’s and mixer units etc. can often be
adequately powered using UK sized AA, C, or D sized batteries. If you’re
out playing a lot you’ll be getting through shed loads of them so
buying a decent set of rechargeable’s will save you a good deal of money
in the long term. You generally have the choice of buying two types,
Ni-Cd or Ni-MH.
Nickel Cadmium (Ni-Cd) or Nickel Metal Hydride (Ni-MH) ?
Nickel Metal Hydride (Ni-MH) batteries
generally deliver more power for longer periods of time and can be
recharged more often than Nickel Cadmium (Ni-Cd) batteries. Ni-Mh
batteries are more suited to high drain applications and do not suffer
from the so called ‘memory effect’.
To achieve optimum performance and
sustain battery life, Ni-Cd batteries should be fully discharged before
any subsequent recharge. Failure to do so, can result in the battery
creating a sort of fake ‘memory ‘ barrier at the point in the cycle from
which it was recharged. During future use, the battery remembers that
level and only discharges to that same point.
It is also claimed that overcharging
Ni-Cd batteries causes them to become somewhat ‘lazy’, affecting their
ability to hold and dissipate charge evenly. Lazy batteries are prone to
discharging very quickly even immediately after a full recharge. This
claim is disputed by fans of nickel cadmium cells as it is said a few
deep cycle recharges can often return the batteries to good working
condition.
Ni-Mh on the other hand do not suffer
from memory problems or issues with laziness, and can be topped up and
charged at any point in their usage cycle without affecting their
capacity.
I personally go for the Ni-MH.
Types of Car, Marine and Heavy Duty Batteries
There are 3 main types of battery. Starting batteries, marine batteries and deep cycle batteries.
Starting Batteries
Designed for starting and running
engines, powering car lights and radios etc. These type of batteries are
required to produce very high starting currents for a very short space
of time and not for supplying heavy and continued loads.
Starting batteries are not designed to be
repeatedly charged and discharged during normal use and should never be
discharged by more than 5% of their capacity. In their usual automotive
applications, any drain placed on a starter battery is immediately
replenished by the vehicles’ alternator when in motion, keeping it
constantly topped up and in good condition.
Deep Cycle Batteries
Deep cycle batteries are designed to
deliver a larger output for longer periods of time and to withstand
countless charge/discharge cycles before their performance drops to
unusable levels.
A deep discharge is generally regarded as discharging a battery by 40% or more.
Deep Cycle Battery
Deep cycle batteries are designed to be
discharged by up to 80% of their initial capacity, but in reality, no
battery should ever be discharged by more than 50% of it’s rating on a
regular basis, even if it is a deep cycle.
Once you drain a deep cycle battery to
below 20% of it’s capacity, it’s inner structure is compromised and life
span is considerably shortened. See the notes on depth of discharge
(DOD) below to see how a battery’s lifecycle greatly depends on the
depth at which it is regularly discharged.
Marine Batteries
Marine batteries – Fall some where between the two above.
As you can imagine the demands of a boat
battery would be somewhat greater than that of a car and a combination
of both high starting and deep cycle qualities are needed. You may often
see batteries sold as ‘Deep Cycle Marine’ batteries but there is no
real way of telling their exact make up or how good they are in relation
to a true deep cycle battery. The term deep cycle is often overused by
companies selling marine batteries.
You can differentiate a true deep cycle
battery normally used in forklift trucks, RV’s (recreational vehicles)
and golf carts etc. from a marine battery as any battery rated in CCA’s
(cold cranking amps) or MCA’s (marine cranking amps) may not be a true
deep cycle battery.
Deep Cycle Batteries Used In RV’s
Depth of Discharge (DOD) Rating
When buying a battery, be sure to look at the figures given by the manufacturer for depth of discharge (DOD).
DOD rates are important as they define the way a battery’s power capacity has been tested by it’s manufacturers.
A battery that is discharged by only 10%
each time it’s used, will have a life span of up to 5 times as long as a
battery that’s been discharged to a depth of 50% each cycle.
Although deep cycle batteries are
designed to withstand regular discharge cycles of up to 80%, the same
battery discharged by only 50% will have nearly double the life span of
one exposed to a DOD of 80%.
Be aware of this when studying the
manufacturer’s lifecycle figures for your battery. The lifecycle
expectancy quoted for the battery you buy may have been rated at a
different discharge level than that which you intend to use it. This
could result in you buying a battery that in reality has a much shorter
life span than expected.
Amp Hour Rating Time and the Peukert Effect
You must also look at the amp hour rating
time that the manufacturers give. This is the amount of amp hours the
battery kicks out when it is discharged down to a certain voltage.
Due to the nature of battery physics, the
rate at which a battery is discharged directly affects the amount of
amp hours it can supply. If a battery is discharged quickly, say over a
period of 8 hours, it’s capacity will be considerably less than that of
the same battery discharged over a 20 hour period and even more so as
one discharged over 100 hours.
This theory is known as the Peukert
effect. To save going into a load of technical blurb and to keep things
simple, I’ve given a few examples below.
If you were to completely discharge a
battery over 20 hours, it’s amp hour capacity can be anywhere from 10 –
20 % lower than the same one discharged over a 100 hour period.
A battery discharged over 8 hours can
have a capacity anywhere between 20 to 35 % lower than if it were
discharged over 100 hours.
A battery discharged over 8 hours can
have a capacity anywhere between 15 to 20 % lower than if it were
discharged over 20 hours.
It is also considered that if you
discharge a battery at full whack ie. at it’s maximum amp hour rating,
it will only be capable of supplying half of it’s actual (Ah) capacity.
So a 20 amp hour battery discharging by
the full 20 amps in one hour, would only actually supply a mere 10 amp
hours of energy before being fully depleted.
Battery manufacturers will often quote
the ‘hour rate’ of the battery over the 100 hour test period in order to
beef up it’s supposed capacity rating. You may also be given the 20
hour test rate along with other shorter rates like 6 or 8 hours.
Make sure you are aware of these
differences before you buy your battery so you know exactly what to
expect from your purchase. A combination of misleading DOD information,
amp hour rating times and the Peukert effect could result in your
battery having much less potential than you bargained for.
Batteries also have a tendency to become less efficient as they age.
Should I Buy a Conventional Flooded ‘Wet’, Gel or AGM Battery ?
Flooded or wet batteries are generally
the most commonly used and the cheapest. Filled with sulphuric acid and
distilled water they come in two types, serviceable and maintenance
free.
Serviceable
wet batteries generally require a small level of maintenance and need
to be ‘topped up’ periodically in order to replenish fluid losses from
the venting of gasses from the electrolyte (battery acid) surrounding
the cells. Care has to be taken when handling flooded batteries due to
the corrosive nature of their contents and the fact that they are not
sealed for maintenance purposes. They also require a cool down period of
an hour or so after they have been recharged.
You can accurately check the state of
charge of a serviceable wet battery by checking the specific ‘gravity’
of the electrolyte using a hydrometer.
Using a Hydrometer
Maintenance free wet batteries are
totally sealed and are not user maintainable. Once the electrolyte
solution drops below a certain level or becomes contaminated with eroded
sediment from the battery’s lead plates, the battery has to be
replaced.
Gel and AGM batteries are both types of
valve regulated lead acid batteries (VRLA’s). These are sealed and
pressurised but regulated through means of pressure safety valve incase
of excess gas build up. Most of the oxygen and hydrogen created during
the battery’s charging process is recombined into water preventing
evaporation and water loss.
Gel Battery
The recombination process is extremely
efficient meaning VRLA’s never need to be topped up and gaseous
emissions are kept to an absolute minimum.
Instead of sulphuric acid and distilled
water, gel batteries are filled with a gelled electrolyte consisting of
sulphuric acid and fumed silica. This immobilises the contents and means
the battery is safe to mount in almost any position. The gel also
provides the battery with greater durability, shock resistance and makes
them immune to leaks and cracks. They also have a much higher power to
weight ratio that wet batteries.
AGM absorbed glass mat batteries are
comprised of an electrolyte absorbed in a sponge like mat of glass
fibres. Their construction makes them even better performers than gel
batteries. AGM technology is the the newest and most effective form of
battery construction and as expected is the most expensive.
Gel and AGM VRLA batteries also self
discharge at a much lower rate when in storage and have a higher
charging efficiency than flooded batteries. This means they need less
power to charge, and they stay charged for much longer when not in use.
Chargers
If you want a battery to last as long as
possible, you need to buy a quality multi stage or ‘intelligent’ charger
capable of dealing with your battery’s requirements. Over charging a
battery, or charging it too fast, to slow, or at the wrong current will
seriously affect it’s future capacity to store and deliver charge. Cheap
chargers are not a good investment.
You should choose a charger according to
the job it is required for. Wet batteries and VRLA’s charge at different
rates so ensure the charger you buy is capable of supplying your
batteries needs.
Charger Rating
To buy the correct rated charger you should think about the time constraints at which you operate.
If you need a charger capable of
recharging your batteries over short periods of time and on a daily
basis, you will need one with a high current rating. If you are only
using them every once in a while then you could get away with a cheaper,
smaller rated charger which would do the job over longer time period.
e.g If a 100 Ah battery needs a power
input of around 110 Ah to fully charge it, then a 10 Ah charger will
take approximately 11 hours to do the job. A 25 Ah charger should only
take around 4.5 hours.
You must also consider the physical
conditions your charger will be working under. If your set up is
subjected to wet or damp environments or exposed to the elements then a
waterproof charger may be necessary.
Ensure your charger has at least 3 charging stages.
1. Bulk stage – For the bulk of the main charging capacity.
2. Absorption stage – Tapering current for the last 10-20% of charge.
3. Float stage – Maintains a very low charge in periods of storage to prevent battery discharge.
Battery Care and Storage
Even an expensive marine or deep cycle
battery won’t last long if you don’t look after it properly. This
includes charging it correctly and with the right equipment, keeping up
the maintenance and correct storage at times when it is not in use.
Marine and deep cycle batteries should be
charged with a lower current and over a longer period of time than a
regular starter battery.
Always use a multi stage charger. This
will extend the life of your batteries. Using an average car starter
battery charger to charge your deep cycle batteries will shorten their
life span. If you only have a 1 or 2 stage charger, ensure the battery
is disconnected once it is fully charged. Overcharging a battery will
also seriously affect its long term capacity.
A deep cycle battery should never be
discharged to below 20% of its initial capacity and it’s voltage should
not be allowed to drop below it’s rated voltage.
In storage, a battery will slowly
discharge by itself and over a prolonged period of time if not
maintained, will completely exhaust it’s charge. This can cause
irreparable damage to the cells.
It is important to check the charge
levels of your battery every month or two. Recharge your battery on a
slow trickle charge if it needs a top up.
Batteries should never be stored in very
cold or freezing conditions as this can cause irreparable damage to
cells and casing. Always store your battery in cool dry conditions away
from the elements, especially in winter and over long periods of
inactivity.
A battery should always be stored in a
fully charged state. Doing this will also help prevent it from freezing
if it does encounter cold conditions.
Do not store in hot environments as this
increases the rate at which they self discharge. They should never be
exposed to direct heat from heaters and radiators etc.
All batteries should be stored in well
ventilated areas. Wet, sealed and gel batteries contain sulphuric acid
and lead. These substances are toxic and can give off poisonous fumes.
Charge your wet batteries in well ventilated areas. A charging battery gives off hydrogen gas which is flammable and explosive.
Now you know a bit more about batteries, take a look at my other guides on how to use them to power your equipment outdoors.
…
For time and legal reasons I don’t answer
reader’s questions on calculations or individual set up’s, but if you
need to know anything about creating your own power set up or need
advice on calculations, make sure you fully read through my battery guide and posts on inverters, battery calculations and battery connections.
There you should find all you need to know to help you get started.
…
Other Posts of Interest
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