Collyn Rivers and charging caravan batteries

Mike

My vehicle is a troopy 1995.

Does that change your thoughts on whether I would get more than 70%

Regards Boo Boo

Not much I don't think. But why not buy a hydrometer (should only be around $5?) and test your battery after a long run in the vehicle?

It still doesn't matter what state of charge your battery is when you connect the fridge _providing_ you don't allow the battery terminal voltage to fall below 10V5 minimum (ideally 11V5) the battery will not suffer it just means it will run your fridge for less time.

Mike Harding

Hi Boo Boo, just following on from Mikes reply, the thing you have to remember is that most people on this site will be driving their vehicles, 4x4 or car, for more that the usual shopping trolly run to the shops that most vehicles do.

As such even with older vehicles, providing your vehicle’s electrics are working correctly and your battery(s) are in good nick, there is no reason why your battery(s) can get to at least 95% charged when you go on a long trip, particularly if this is your everyday vehicle and you do at least 15 minutes driving after each start.

There is no effective way of knowing if your vehicle’s battery(s) are more that 95% charged but for most uses, 95% is sufficiently high enough to allow you to work out how much time you can expect to use your battery(s) before they need charging.

If you want to be sure of the state of your battery(s) go to a reputable auto electrician or battery sales outlet and they should test your battery(s) for free.

Cheers.

Gees Craig,

Hope you are wearing Nomex.

Last time I criticised Collyn's advice his fan club flamed me incessantly.

Still didn't make him right though...

Dave

Crackles

It definitely states in his book on Solar power for caravans that the starter battery and caravan deep cycle will only be charged to about 70%.

If thats not quite correct then I would imagine that Collyn would be happy to correct it in his next addition.

Your reply, and others I have received have helpd me a great deal. In fact the last to posts have helped immmensley. For those that read this post and helped with my water leak you will be happy to know it is FIXED.

Many thanks everyone
Boo Boo

Make that two not to., and immensely not immensley.

SHOOLD HAVE USDE SEPLL CHECK!

Dave, yes I was expecting a little Napalm hence "going out on the limb" but despite Collyn's vast knowledge on all things 12 volt, some of his theory's don't necessarily cover all circumstances when put into practice, like for example "starting off deep cycle batteries will wreck them in under 6 months".....I've been doing just that for almost 4 years & I'd be interested to know when I can expect mine to fail ;-)
Although simple in theory, 12 volt systems with all the variations in environment, product range, quality & design, don't always opperate the same way for everyone & is one reason it always develops plenty of healthy (often heated) discussion on this forum.
Cheers Craig............

Hi japmel, unfortunately it’s not quite that simple.

Some alternators charge at up to 15.7 volts but these charging voltage govern more how quick the battery can be charged but have no real barring on the final voltage of a fully charged battery.

Crudely put, most batteries that are at a fully charged state will have a settled voltage of around 12.7 to 12.9 volts depending on the type battery and any voltage reading above this is only what occurs while the battery is settling, which can take up to 72 hours after the charging voltage is removed, no matter by what means they were charged.

Cheers.

Most modern chargers including the automatic type charge to around 14.2 to 14.4 volts. Vehicle alternators are usually similar. After charging and left to rest the battery terminal voltage quickly drops to about 12.7 or maybe a bit more. Full charge can only be really tested with a hydrometer and the SG fully charged should be about 1275. All cells should be the same or very similar.
I have a couple of these chargers and though they each work slightly differently the end result WHILST ON CHARGE is close to 14.2 volts.
Measuring voltage means very little. An example is a recent Aux battery fail in my Patrol. Tried to winch up the boat and nothing happened at the winch. Checked the battery volts and it read 12.4V, I was on my own so I couldn't check the battery voltage under load. I run jumpers to the winch and wound the boat back on the trailer. I figured it was a problem with the vehicle wiring somewhere.
At home I checked out the anderson plug and found the same 12.4V. I then ckecked the voltage after I again plugged in the winch and switched it on to unload the boat.
The volts at the battery went to virtually zero.
I tried a charge and the battery did not take any current.
Moral of the story is never rely on a voltage check to decide on battery condition.
Incidentally the battery was on of those fully sealed calcium/calcium type about seven years old. Probably a failed cell connection caused the collapse internally.

I worked in the communications industry for some 40 years and when performing a discharge test we always stopped the test when the lowest cell voltage in the battery bank was at 1.85 volts. The capacity was then worked out and recorded.

Lead acid cells (very large ones) lasted about 10 years and Nife cells (80AH) about 40 years. Nife cells had a different cell voltage however the lowest cell reading escapes me at the moment.

Pooley

Try it and see?

It will be less efficient because you'll be converting 12V to 240V and back to 12V but providing the engine is running you probably won't care.

The formula for discovering the amps required for X power (watts) is:

amps = watts / voltage

so 100W / 240V = 0.416 amps
and 100W /12V = 8.3 amps

Mike Harding

" my query is would the battery charger in the camper trailer charge my battery (deep cycle) faster with the inverter (while car is running) than using the alternator"

Mattie,
An alternator is capable of charging at much higher currents than chargers, particularly when the battery is discharged. But it all depends on the quality of the wiring, and the earth etc

Hi Matti, as Mike pointed out, this is not only inefficient and as Phil pointed out, you only need decent size wire and the alternator will do a better job in a shorter time but even if you where to use the inverter / charger set up you would still need decent size wire and in fact you would theoretically need thicker wire because of the inefficiencies of such a set up.

To a far more important point, this type of operation is incredibly dangerous because of the potentially lethal situation that could occur as the result of your vehicles being involved in an accident.

As there is no way to make this kind of set up 100% safe in all situations, the potentially lethal position this set up can put you in is not only dangerous for yourself but it can put rescuers in unnecessary danger as well.

Mike is there not a power factor when working out ac volts

Power(watts) = I(rms) x V(rms) x power factor or is this only for electric motors?

Regards

Richard

Indeed there is Richard but, as you say, power factor only applies for an AC supply and only with loads which have a reactive component (inductive or capacitive) motors are a typical case. Reactive loads create a phase difference between the voltage and current and mean that I = V/R no longer works accurately. Resistive loads (eg heaters) do not create this problem. Power factor normally only need be considered by electrical engineers doing load calculations. Good point though.

Mike Harding

Thanks

I'm no elecy just now some things

Richard

Indeed Jeff, I was sorry to see him go, although sympathetic to his feelings, he has a good knowledge of things 12 volt and is a loss.

Hi Folks,

Collyn was on here only a week or two ago. Rather than risk misquoting the man here are his articles for your reading pleasure:

Site Link

I posted this link several weeks ago and there were several replies describing why he no longer frequents this site and then a week or so after that I read several of his posts here.... Just trying to recall the topic ... ah yes ... it was part of the epic discussion on big tyres and aggressive treads destroying the universe. He commented on the OKA's treads ripping up the grass.

All is not lost ... perhaps there wll be a 3rd coming ??? lol

Cheers ... Taz