Surviving with just the leisure battery - how long?

[swpostie]

I was interested to read a thread about using the car or a generator to keep the leisure battery charged during a week ath the Great Dorset Steam Fair.

Now I am also going to the GDSF and we are taking the caravan this year, having previously used a tent.

We were hoping, really, that the leisure battery would last a week, without charging, and would like to har other's views.

The battery is 110AH. I have tried, without success, to find out how power hungry the various things in the 'van are.

Most things will be run on gas - in fact the only things I can think of that will use the battery will be the lights, the water pump and the toilet flush.

lights - lets assume we use 2 spotlights for an hour each night. How much power does a spotlight use? About 15W? If that is the case they will draw 17.5A over the course of a week.

Water pump - If someone knows the wattage of the water pump (standard submersible type), or how many amps it draws, together with the rate of flow, perhaps you could let me know - I reckon it will pump around 200L over the week and with the power consumption figures and flow I can get an idea how much of our battery will be going towards pumping water.

Flush - I reckon this must use less power than the water pump as the water is a lower pressure. If anyone has the power and flow figures for this I would be grateful (ordinary Thetford swivel toilet). I don't know the capacity of the flush tank - for some reason I think it is about 15-20L, so let's assume it will pump 50L of pink in a week!

Now I know my battery will allow a discharge rate of 110 amps for an hour or 1 amp for 110 hours. I also know that, fully charged, it should read 12.6 volts and at 12.0 volts it is considered flat but how do the volts and amps connect?

If I have drawn, say, 11 amps for 10 hours my battery, presumably, will be disharged. Does that mean it will read 0 volts? 12 Volts? Or something else?

In other words, if I discharge it to that extent will it be dead - never to be revived? Or have I got it all wrong?

If I'm on the right lines then it looks, to me, that my battery has a pretty good chance of lasting the week.

Please let me hear your views.

Thanks

 

[RogerL]

If it's a basic 110Ah, ie with cell plugs that allow topping-up, it's designed for 100 cycles of 50% discharge.

The actual capacity of a battery reduces as a function of time and useage. An old, overworked 110Ah may have an actual capacity of as little as 10 Ah.

Water pump and electric flush will only draw current intermittently so the main draw will be lighting, in your case.

Spot lights are inefficient, they generate more heat than light but that all consumes power. Stick to flourescents or leds.

 

[Moth_5041363]

We have done 13 days on a 85 amp battery, useing only one light at a time. the shower, ect, and only a very small tv

 

[Surfer]

The question about long a battery will last gets asked nearly every week and I am surprised that PC have not done an in depth study and posted up some usage facts using a 110 amp battery only and in another table adding in if you also use a solar panels etc.

Have there been any worthwhile articles on fuel cells in caravans as this will obviously be the way future. Then CLs will not need to be concerned with installing EHU.

 

[ChrisUK]

New van / battery (118AHr). Over a 5 week hol in Mull recently, I found the battery would not last more than about 4 days before the volts were down to about 12.3. Long daylight hours but modern vans seem to use alot more AHr than my old van. Thetford fridge was taking a fair few milliAmps 24/7. No TV - not available in practice on the island) The inbord pump realy made the volts droop. We tried to be carful with the lighting. I have a second 85 AHr battery (bit old) which I change about to a charging facility in the boot to top up when driving around. I do need to improve this as I get a 1 volt drop at the rear which reduces the charging capability.

 

[Transporter]

I just bought a solar panel "12V battery maintainer" for a tenner.

It claims to be able to keep a battery topped up even when it isn't sunny, and a multimeter tells me that it produces a fluctuating 8 to 11V even just sitting on a dimly lit kitchen table. Haven't tried it outside yet.

It comes with a cigar-lighter connector (is that likely to work?) and crocodile clips. It isn't weather proof.

Instructions say up to 1.8W / 125mA output. I guess that's enough to keep a battery going. Must be worth a try for

 

[emmerson2]

Three weeks comfortably with a 110amp, two with an 85amp. I now carry a 400amp starter/booster but have never had to use it yet, but we only use flourecent lights, and don't have a tv.

 

[Transporter]

> "we only use flourecent lights"

Interesting. My caravan has only Quartz-Halogen bulbs, as far as I know. Would it be easy to install fluorescent tubes instead? It certainly doesn't look it.

 

[emmerson2]

Transporter, it should be just a case of replacing your halogens with flourecents, available form any caravan shop. If you don't feel confident in doing it yourself, get an auto electrian to do it. You will save on power, as the strip light doesn't waste so much power in heat.

 

[Transporter]

> it should be just a case of replacing your halogens with flourecents

Well, yes, but are you saying that there are fluorescents available that will plug straight into a Q-H socket? (I meant the ones that are just two small holes a few mm apart.)

 

[swpostie]

Many thanks for all replies - I'll let you know how we get on!

 

[emmerson2]

Transporter, sorry, I missed your post.No, there probably isn't anything that will just plug in. Yo might have to lengthen the wires, but a strip light should hide any non-standard work.

 

[AlanJ]

Hi All

I also wanted a "reliable" means of being free of EHU's but did not want to return to those "minimalist days" of yester year.

I fitted the latest Smart Fuel Cell EFOY which gives me the following:-

EFOY 1200

Rating 50 W

Charge capacity 1200 Wh/Day 100 Ah/Day)

Charging current @ 12 V 4.2

In trials to date I can run everything electrical in my Bailey Pageant Bordeaux which includes 18 hologen lights, 19" LCD TV at 4.5 Amps, Satellite system, Roof extractor fan setting 2 at 2.2 Amps, water pump and 150w inverter for laptop.

Obviously this was testing at the extreme as we would not normally run in this mode.

Full shake down trials next week at Normans Bay - will let you know how I get on.

Only down side, at present, is the price of Fuel Cell Technology - but that will come down as it becomes mainstream