Following help in previous postings I have finally installed my new 17Ahr
Yuasa battery in parallel to the existing 7Ahr battery in my alarm box.
(£38 including delivery from Maplin!)
All looks fine, but can I check on one thing - When connecting the new
battery there are a increased hmmmm coming from the box. This is just the
transforming starting to charge my new (and presumably not fully charged)
battery, isn't it? Its nothing to worry about is it?
Because I have added the extra battery it is just going to take longer to
charge, but there is no other consideration for the charger is there?
Just checking :-)
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2 /
I don't know the reasons why or what panel the 17Ah battery is connected to,
but I would disconnect it now!!
If you are referring to a domestic intruder alarm panel, most only have the
ability to charge a 7Ah battery, also, you have connected in parallel
batteries of differing capacity which must not be done due to issues of
equalisation of charge etc.
Hehe - I like your thinking.
The 17Ah battery will have a much lower internal resistance than
your 7Ah. It will draw a much higher current when charging
(unless the charger is constant current, which would be strange
for lead acids).
Having them both in parallel almost guarantees that your charger
(the thing that's humming) will die soon.
Remove the 17Ah, and just have the 7Ah as was. If you really
need more capacity, you need to build a suitable charging circuit.
i must agree with the person who said that putting batteries of this type in
parrallel is not a good thing for the stated reasons. however the internal
charger in the alarm panel will be a constant voltage type with current
limiting, designed to float charge the battery, this means that the current
will reduce to a small float level (trickle) when the battery has fully
charged. so i would say disconnect the small battery and the large one will
be ok (just take longer to attain the full, float charge voltage so the
charger will be putting out its max current for longer)
Ok, thanks everybody. My new 17Ahr is now disconnected :-) Hope it was not
So, how should I do this? I want to add more capacity for those long
winter power cuts we get out here in the country and I thought dropping in
a new battery would be just the job.
How should I add my new battery? I don't mind buying a new charger but how
should I connect it in relation to the other battery and charger.
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2 /
OK, You can either do it properly or do it cheaply. The proper way would be
to have a proper rated PSU/charger in a proper steel cabinet with the
battery. Quite expensive.
The cheap way would be to have a large battery like your 17Ah or a car
battery (that way you can go as big as you like!) and have it on a trickle
charger - although the best way is to simply charge it up ready for use as
it'll hold a charge for many months without trickle.
Now then PLEASE don't connect it to you alarm panel cos your alarm panel
will go bang. Instead you can wire in a relay so that if your mains fails
the relay will switch from alarm battery to car battery. The problem is that
during switch over the panel may activate (alarm) due to PIR's etc. dropping
out of circuit. The SAB too may operate causing a tamper fault. The real
proper way would be to have a control circuit which would monitor the panel
O/P voltage and bring in the car battery at a suitable level. All very
If I was in your situation where you are expecting lots of power cuts I
would probably do away with the panel battery and disable the panel charging
circuit (usually a simple matter of cutting a link or resistor - speak to
the manufacturer) and then just connect a fully charged large battery to the
panel making sure a proper fuse arrangement exists in the battery feed. That
way the panel won't need to charge anything but will have a damn good
standby power source in the event of a mains failure. You do need to ensure
that the cutting of any charging links does allow the battery to power the
panel. Older panels had a marked link on the PCB for dry cell batteries but
that was many moons ago.
Remember too that any short circuit of a large battery will melt the wiring
so please fuse well.
Pete, I am fine with doing it properly - it will still be cheaper than the
£228+VAT that the alarm people wanted!
If I do source the properly rated charger (a 3A one should do it) then how
to I connect this? I would still like to keep the existing 7Ahr battery,
and add this in parallel but if I do this then how to I charge it? I want
to do as little as possible in "their" cabinet and to add my own with this
Get hold of a Power Supply Unit / Charger that will comfortably take your 17
A/hr battery, and comes complete with a relay switch that operates on mains
The relay should be wired with the open no voltage contacts connected to
your alarm panel. The voltage side of the relay will be connected from
charger to battery when mains power is present, and then drop from battery
to appliance if a mains failure occurs.
These people should be able to point you in the right direction:
You really do need to read properly (!!). You CANNOT connect the large
battery in parallel with your 7Ah - period.
If you do as some say and use a standby PSU with a relay (I mentioned this
too) then the alarm will probably activate on change over as the PIR's etc
will go into alarm, the SAB will operate and the panel may go into "power
up" in which case it'll activate itself too!!!!
If you do away with your 7Ah and just use the large battery in "dry cell"
mode then all will be well. Reading between the lines... is you alarm on a
maintenance contract? because if it is then you obviously can't cut the
charging link out although you could always cancel the contract and come
here for advice when it fails!
Others have suggested a caravan battery - brilliant idea. A boat battery is
another. These are designed to hold a charge for many months without use and
a gel filled as opposed to liquid acid.
You can buy a simple "battery maintainer" from the likes of halfords for
around £20 and that will keep the battery topped up OR, if you're into
playing, buy a small windmill charger like boat owners use and use that to
keep the battery up to scratch!
In any event you need to discard the 7Ah!
You can actually.
Lots of things like cars and caravans regularly connect the batteries in
parallel. They charge just fine. They even discharge just fine, but its
obviously advantaegous in e,g. a camper to discnnect teh primary engine
battery from teh camper to ensure you can start the engine the next day
if you flatten the lesiure cells.
So what?> The principles - that its fine to slap two lead acid batteries
in parallel to both charge and discharge, holds.
Just examine the voltage current characterists of lead acid
accumulators, under both carge and discharge, do the maths, and work it
out for yourself. If you are capable.
Don't listen to him. He is seriously talking through his arse.
If your charger didn't go bandg withing 5 minutes of hooking
up the bigger battery, I would lay you odds of 50:1 that it
will never go bang in a day or five, or however long it takes.
If you are concerned, charge the bigger battery up elsewhere, and then
comnect it fully charged.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.