Batteries

[Amicus]

One for John `Squeers.’

John, I’ve been lurking around alleys like this and uk.rec.waterways trying to get a handle on things narrow-boat, I still have trouble with batteries, like cutting thru the copy-writers bull-shit and the “lax terminology”.

It seems that the going rate for the domestic bank is X no @110A, now 110A don’t mean much to me without some sort of time component, is 110A a 10 hour rate, 20 hour rate, 3 day?

Kindly look at this page

http://www.dcbattery.com/rolls.html

Scroll down the table of 6 volt batteries and have a shuffty at the one labelled 6CS-21P, I picked this one at random, I don’t really have much clue, say 2 no of those in series (12V), how would that shape up against the 110A that seems popular? I can guess that the Rolls/Surrette batteries are pretty fierce dollar, but how do the capacities compare.

TIA I appreciate your indulgence.

[Amicus]

I’ve just noticed the battery above has 20 quarts of acid, so perhaps that one is over the top, can we talk about the smallest 6V jobby, the HT-1

[Alastair]

depends what you are using the batteries for.

 

If low-current draw, then the capacity is usually reckoned to be about 30% of the stated capacity. So for a 100Ah battery, that would be 30Ah.

 

If the battery is 12V, then that is equiv to a 30W bulb being on for 1 hour. Not much.

 

Ah is often quoted, but you have to be a bit careful, as it isn't a measure of energy. So a 12V 100Ah battery contains half the energy of a 100Ah 24V battery.

 

People blithley talk in Ah because most people are running 12V systems. (or a 12V system connnected to an inverter)

[John Orentas]

Amicus.

 

Firstly there are a few people on this site who have a lot of experience with batteries.

 

You are quite right there is more commercial hype written about these products than almost any other.

 

Batteries are rated in several ways.

 

Voltage, obvious enough but you must remember a battery circuit when it is being charge can be significantly higher that the 'rated' figure, nominal 12 volt. can be as high as 14 volts.

 

Amp. hours, the standard measure of capacity, the idea is that a 100 a/h battery can be discharged at say 1 amp for 100 hours or 100 amps for 1 hour. This area is very iffy and should not be taken too literally, there are all kinds of variables. It is of more use when talking about charging which has similar arithmetic.

 

10 hour rate, this is regarded as a reasonable maximum charge rate for the average battery, you risk doing some damage if you exceed it. Your 100 a/h battery charged at a 10 hour rate = 100 Divided by 10 = 10 amps. you must then multiply by the efficiency factor, 70% or 1.4.

 

So your 100 a/h battery may be charged for 10 hours at 14 amps. In practice the charging system will look after all this.

 

The 6CS-21P battery, it looks far too big to me, 271 lbs weight not very practical and no doubt very expensive and you will need 2 of them.

 

This is where opinion comes in, your can buy from good caravan shops 110 a/h leisure batteries for not much more than £40. I know from experience these will last for at least 5 years. Or you can pay 2 or 3 times as much and get some which will last up to 10 years, take your choice. Paying a lot of money does not equate to quality or after sales service as a recent thread will testify.

 

The acid capacity is not significant and very rarely specified.

Edited January 19, 2005 by John Orentas

[Amicus]

Nay nay, thrice nay, a 110AH is a 110AH battery no matter what use it is put to.

As I was typing this reply the fog cleared a bit, I think I can see that I had hold of the duff end of the stick. So editing this prose I came up with 110A for 1 hour, or, to look at it another way, 1 amp for 110 hrs. Or 55 amp for 5 hours

Have I just answered my first question? (correctly?)

I can understand that one wouldn’t get this capacity in service and it would knacker the battery to attempt to do this. Or would it, assuming genuine Deep Cycle batteries? It would shorten the service life, as in

http://www.dcbattery.com/rolls_cs_cell_cycle_life.html

but 110AH ought to mean to a sensible end point??

 

If the above is something resembling the truth, can I ask how this compares to the battery mentioned, the HT-1 which is quoted as 105 Amp Hr 20 Hr Rate.

What capacity would one get with two in series, compared to the famous 110AH

[Amicus]

Sorry John, my post crossed with yours, I was reping to Alistair

[John Orentas]

Amicus.

 

55 amps for 2 hours.

 

I have always been a bit sceptical about duty cycles. As long as you don't over charge or discharge them to zero to often I believe you can just think in terms of battery life. What batts. don't seem to like is being left alone, a unit fitted in your car and in daily use will last much longer than one just stored away.

 

I'm not sure I understood your last bit, the 6CS-21P is a 683 a/h at 6 volts, with two in series you would have 683 a/h at 12 volts. What is an H3-1.

[Alastair]

Amicus, the use matters a lot.

 

If the battery is used for starting, then the total Ah capacity is pretty meaningless, it is the ability of the battery to sustain a high current draw for a short period that matters.

 

If you run a very big inverter from a battery, that will have a high current draw. Some batteries won't like this, and the voltage will drop off fast - then disconnect the load and they'll *recover*.

 

I agree with John about the leisure batteries. Auto shops also sell them at reasonable costs.

 

Manufacturers quote a total charge capacity - this is your 110Ah. However, you can only discharge to a percentage of this - that's the 30% I was talking about.

[Amicus]

John, Alastair, thank you for your perseverance, I know this subject keeps coming up and must be pretty tedious for yous guys.

About the FAO thing, I regret that and I apologise to the members of this forum.

I am a newbie to this board but am not a newbie to the internet. Being the miserable old git that I am entitled to be I do get irritated with the poor signal/noise ratio on the internet, for which I’m sorry.

 

It was silly of me to pick the 6CS-21P as an example and I mentioned the 20 quarts to indicate just how big and silly this was for an example.

The HT-1 is a much smaller and sensible choice from the same list.

I am not suggesting that I or anybody should buy or specify this type of battery. I used them here because I believe them to be genuine and unambiguously Deep-Cycle types and the data is available on the internet.

I don’t think they are available this side of the pond, although I have seen them on yachts.

These extreme examples were used to get away from the “Duff Guff” syndrome.

 

I see now the in series truth, the Volt double, the Amp/Hrs stay the same and I guess the Watt/Hrs double, clear as a bell

 

I believe I am up to speed with starter batteries and alternators and my interest lies purely with the domestic bank side of fings.

 

A little background as to my interest in the quest for “The Truth”. In about 4 years I, Imshalla, retire. One of two things will then happen. (1) I sell the house and buy a 57ft shell and fit-out myself, I was a boat-builder for 25 year and a carpenter for nearly as long. (2) I sell the house and ship to Crete. I have spent some time on Crete and have learnt that the power supply is not very reliable, especially in the remoter parts that I prefer so I will invest in a solar/wind powered back-up system. Hence my interest in deep-cycle batteries.

Time for a brew, I’ll be back

With part two