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Sealed Lead Acid Batteries


#1

Ever wondered what capacity battery you actually need?

Are you carrying too much weight?

Try out my calculator at http://www.g3cwi.org.uk

Comments welcome!

73

Richard


#2

Hi Richard

This is great… I still haven’t homebrewed a trail radio (not brave enough yet though I fancy a Blue Cool Radio) or purchased an 817 so I was wondering this week what SLAB I would need with my 706… it’s a bit of a power hungry beast, even on receive.

Thanks… Marc G0AZS


#3

In reply to G0AZS:

Marc

I have the following measurements for an IC706 (thanks to John G4YSS)

RX = 1.1A
TX (100W) = 16.3A
TX (55W) = 13A
TX (26W) = 10.3A

73

Richard


#4

Hi Richard…

That’s really useful too… I note that the “spec” for my 706IIG says it’s 2A on RX and I always assumed it would be high as it gets pretty warm even just sitting in RX mode… but maybe your data is more realistic in “real world”.

I thought I would run it at about 20W so using your XL sheet tells me that a 7ah SLAB should easily give me and hour of operating at that power. Which should be enough on a single activation… even on a popular summit… shouldn’t it?

Thanks again… Marc G0AZS


#5

In reply to G3CWI:

Those figures look reasonable Richard. My 2.8AHr SLAB / FT817 combo seems to have more than enough capacity for my operations which are typically SSB only not lasting more that 40mins. Doing 3 FM only operations didn’t seem to make a dent in its capacity.

You might want to add weight to that spread sheet so people can decide whether it’s worth changing to a smaller or bigger battery based on their expected endurance requirements.

Andy
MM0FMF


#6

In reply to MM0FMF:

You might want to add weight to that spread sheet so people can decide
whether it’s worth changing to a smaller or bigger battery based on
their expected endurance requirements.

Fair point. The datasheet is here:

http://www.yuasa-battery.co.uk/industrial/downloads/NP_Series-pdf.zip

73

Richard


#7

In reply to MM0FMF:

You might want to add weight to that spread sheet so people can decide
whether it’s worth changing to a smaller or bigger battery based on
their expected endurance requirements.

Hey presto! As if by magic the spreadsheet now suggests what standard capacity cell will meet your needs and tells you its weight!

73

Richard


#8

I am writing an article on Sealed Lead Acd Batteries for Radcom at the moment. It would be interesting to know why people like them when compared to other battery types?

73

Richard


#9

In reply to G3CWI:

I like mine because it was free! I acquired a brand new 2.8AHr cell which the alarm fitters decided not use in the new alarm system at work. So for the time being I’m prepared to carry 1.2kg of SLAB because it was free. When it comes to time to replace it then I’ll invest in a LiIon system. If I was starting now, then I’d plump for a LiIon pack and charger where I would get nearly twice the capacity for only a quarter of the current weight. At a cost of course.

SLABs have the advantage that they can be charged with a simple regulated PSU whereas lithium cells need “special” chargers and smart discharge regulators to stop you killing the cells. And, of course, SLABs are cheap!

Don’t forget to mention in your article that if you want long life you should not slope charge and your charger should be temperature compensated, i.e. the charge voltage needs to drop as the ambient temperature rises. More batteries have their life cut short by charging too hard when hot that any other way.

Andy,
MM0FMF


#10

In reply to G3CWI:

Hi Richard,

I use SLABs as they are cheap and easy to obtain. I have 4 3.3AH SLABs - they weigh 1.3kg each and cost £8 apiece. On a 4 summit day, that’s ideal. If I’m doing more, I could take a couple used ones up the later summits as I usually choose easier summits as the day progresses… not sure why! I started with a 12AH pack which at 4.2kg is heavy, but I can operate 25 watts of FM on 2m for 4 hours using this and it is mandatory for the big linear.

Weight is not an issue for me especially as I carry far heavier things with me. It does add up, but up to around 18kg (incl antennas) is okay. I have been known to carry nearly 30kg on occasion. John YSS says I’ve got used to carrying weight, but maybe that’s too much on a regular basis.

73, Gerald G4OIG


#11

In reply to G4OIG:

Just ran across this which may be of interest to SLAB users. Great bedtime reading.

http://www.yuasa-battery.co.uk/industrial/downloads/NPManual-pdf.zip

73

Richard


#12

In reply to G3CWI:

Yes Richard, it confirms 14.4V charge voltage for cyclic use. My batteries now hold more charge as a result.

The defaulter on my last outing has been brought into line by a 12 hour thrashing on a standard car battery charger - 0.5A / 17V of relatively dirty DC. A bit like having the cane at school.

73, Gerald


#13

In reply to G3CWI: I also use a SLAB, 4.5AH from Maplin. The capacity is fine for a 2-summit activation (2M fm and ssb - usually an hour or so on each summit. Agreed they are not weight-efficient, but as others have said they are cheap. I don’t know whether the specs agree, but my feeling is that they are less temperature sensitive than some other 2ary bateries. However, I did wreck one by charging with a car battery charger - it got hot and bulged. Got to remember that they are sealed so no charging to the gassing point.

Regards, Dave, M0DFA


#14

In reply to M0DFA:

Hi Dave,

My batteries appear to have two small vents, but I am still careful charging them. The errant battery had a session on the main SLAB charger last week and then was “topped up” at the weekend with the car battery charger in three four-hour sessions. The car charger is only 2A max anyway and the near fully charged battery only pulled 0.5A anyway. It seems to have kicked the battery into life - you can imagine my surprise to be awarded with 10.8v when I coupled it up on Ysgyrd Fawr. Fortunately I had only been on SSB and CW on battery number 2 on the previous summit, so there was ample capacity for a second summit. I also have the 817 internal battery for back up as well, but that does not allow use of the 25w linear.

73, Gerald