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Battery charging on the move
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userColin T
Posted: 26 January 2005 2:35 PM
Subject: Battery charging on the move
 


Has anyone got any personal experiance of either the AccuMate or the ctek multi battery chargers.
I have 3X 110amp batteries and want to try and keep them fully charged.
Point 2. I am thinking of running a small inverter from the van battery when on the move to run one of theese battery charges instead of relying on the alternator as at pressent does not seem to fully charge batteries. I do know we should just use less power!!

Thanks Colin T
userWilliam R Dunstone
Posted: 26 January 2005 3:15 PM
Subject: Battery charging on the move
 


Hi Colin,
Sorry I don't know about the chargers you mention. If you are eveluating I would suggest you look at the Sterling Power, battery to battery charger.
It is made for the problem you have!
BillD
userDerek Uzzell
Posted: 26 January 2005 7:13 PM
Subject: Battery charging on the move
 


Colin: I feel there is some universal law of nature you are attempting to circumvent here, as your ideas seem to go against Conservation of Energy and Quart-into-Pint-Pot rules.

I'm very wary of the idea of running an inverter from your motorhome's vehicle-battery, then using that inverter to power a battery-charger, then using that battery-charger to charge your leisure-batteries that (I assume) will still be connected to your motorhome's alternator-based charging system. If that's what you are actually proposing to do, it seems to have the makings of (at best) a lot of power being lost in the process or (at worst) a damn good short circuit.

In fact, you've accurately diagnosed your problem - you are running your 3 leisure-batteries down to such a degree that your vehicle's alternator doesn't have sufficient time while you are driving to recharge them. Essentially, you need to drive for longer periods or replace your 'van's alternator with one with a higher output. (Or use mains hook-ups more often, of course.) You can't just add a brood of supplementary leisure-batteries and expect an alternator intended originally just to charge a single vehicle-battery to keep up with the extra load placed on it.

As there may be something that can be done to optimise the current charging system, I echo BillD's recommendation that you seek advice from Sterling Power (www.sterling-power.com)
userClive
Posted: 26 January 2005 10:18 PM
Subject: Battery charging on the move
 


Only use the Sterling system if your batteries are not powering any equipment during the penultimate phases of the charging cycle.
The voltages that the battery rises to during the phase of charging that puts in the last 20% are excessive. In my opinion these charging techniques are best kept for applications like Fork Lift Truck Batteries which are disconnected from the truck when they are connected to the charger and topping up is automated. If it were that good car manufacturers would use the technique as standard - but they don,t!.
BUT
You would do a lot worse than to beef up all your battery leads so that the volt drop in them was very small. Say as a minimum 10 mm sq or bigger (I use 25mm sq). Thats POS and also NEG wires to chassis. Make sure that your split charge heavy duty relay takes its incomming supply from the alternator B+ terminal (and not the starter battery pos) as this will give the leisure batteries a bigger slice of the charging current.

Do you by chance have a diesel powered heater? These consume a fair number of ampere hours when running and especially when starting.

Fit a BIG solar panel

Get a wind generator (no don,t use it on the move!)

Make sure your van mains charger is of adequate capacity to put the energy into the batteries during your normal stop overs on site with mains hookups. Check its output voltage gets to 14.

Accept that you will get 80% capacity out of your batteries using just the standard alternator but the need for topping up with de-ionised will remain infrequent.

Have you done the "maths" on your consumption?
Have you measured any voltages during charging? Thats from the mains or with the engine running?

Go to bed when the sun sets!

userDavid Powell
Posted: 26 January 2005 10:32 PM
Subject: Battery charging on the move
 


Hello Collin...Derek sounds worried about this one so I would be as well..remember the good old schooldays...physics I think...goes something like "work done by a machine cannot exceed work done on a machine"?. in other words,You can't get more out than you put in, and you will loose a lot of power through resistance, remember the old V=ir stuff? And what if he inverter running a charger off your vehicle battery runs that flat, how are going to restart your engine?..I do a bit of canal cruising in a narrow boat occasionally, not unlike a motorhome really, diesel engine to propell it, alternater to keep the vehicle battery and three 110 leisure batteries charged which then supply the habitation electricity with 240 Volts through an inverter, as everything in the boat is 240v AC, except the cooker, and we never have any problems. The answer of course is an alternater with a higher output, without the introduction of any other chargers. It is a timeshare boat profesionally maintained so I don't know the out put of the alternater, but it keeps the batteries topped up on around 4 to 6 hours running per day. So you could work out your consumption and calculate the alternater output required, or if you live near a canal, pop along to your nearest marina and have a chat, they are very friendly..just like us.
userClive
Posted: 27 January 2005 9:32 PM
Subject: Battery charging on the move
 


Lets look at some basic maths.

A typical alternator on a modern motorhome will be rated at 100 amperes. (If yours is different then scale the figures accordingly)

You have three 110 ampere hour batteries. =330 Ah
Your alternator has the ability to put enough energy into these batteries to re-charge them is 3 hours and 20 minutes of engine running.
In reality you will probably get about 70% charge in that time and this will go up to 80% after a few hours longer. The alternator will automatically reduce the charge current to stop the voltage going above 14 volts. That,s about as much charge as you will get into a lead acid battery without taking the voltage well above 14.
This backs up the figures quoted for the Narrow boat. (I love them as well)
Clive
userDerek Uzzell
Posted: 28 January 2005 7:54 AM
Subject: Battery charging on the move
 


Clive: Yes, but that assumes a motorhome's alternator has nothing better to do than re-charge leisure-batteries. In practice, if the vehicle has been sitting idle for some time with the alarm on, or the occupants have been running the CD-player a lot, etc. the first duty of the alternator will be towards the vehicle-battery. And, if you are driving at night, in the rain, with all the gubbins (wipers, lights, heater-fan, music) on, that's a heavy constant load in itself. So, although the maths are basic, the times taken to fully re-charge Colin's batteries are essentially unpredictable.

This is a potential downside of adding batteries to a vehicle not designed to take them and it doesn't stop at the alternator being given a hard time. I notice from the Eura Mobil brochure that, as the number of batteries increases, so does the on-board charger's output. For 2 x 105Ah batteries there's a 16A charger, but for 3 x 105Ah batteries there's a 35A charger.
userColin T
Posted: 28 January 2005 10:58 AM
Subject: Battery charging on the move
 


First thank you all very much for your inut.
As it is the set up, origonal Kon-tiki, alternator and charging system all work ok. as per spec. Voltage at battery on charge is ok but point taken about current flow through small gauge wires so perhaps to start with should "beef them up" I am obviously being greedy trying to get more from batteries, we tend to do more off site than on and use 12v-240v via invertor to heat water and sometimes run frigde. Seems to work well until wife gets the hairdryer out!! Have 75w solar pannel bit weighty to put another on. I like doing things myself and it looks a right pig of a job to do the alternator so looking for easy option first. Theese chagers are supposed to "fully" charge batteries and I would only use when van was running.
Still no info on theese chargers, does no one use them. Sorry such a long post!
All the best
Colin T
userDavid Powell
Posted: 28 January 2005 11:26 AM
Subject: Battery charging on the move
 


How about putting an alternater on the wife's exercise bike, and getting a whip.
userWilliam R Dunstone
Posted: 28 January 2005 3:13 PM
Subject: Battery charging on the move
 


Hi Colin,
At least 2 of us have recommended that you talk to Sterling Power, have a look at their website first.
I believe their battary to battery charger is what you need. What it does is it fools your vehicle alternator into thinking that your engine battery is not fully charged and it keeps whacking out the amps at about 5 times the normal level once your engine battery is charged.
It is a very simple DIY job to install.
BillD
userColin T
Posted: 28 January 2005 11:15 PM
Subject: Battery charging on the move
 


Yes thanks Bill, I'll have a look at sterlings site for charegers, Also see if they sell whips!!

Colin T
userDavid Powell
Posted: 28 January 2005 11:29 PM
Subject: Battery charging on the move
 


Hi William...What you are saying about the Stirling charger is very interesting....in fact fascinating. You obviously have studied this at great lengths..You say it fools the alternator into thinking the vehicle battery is not fully charged, so keeps pumping out the power. But surely if the vehicle battery is charging a leisure battery via the Stirling then the 'fact' is the vehicle battery will not be fully charged until the liesure battery is full, so it is not really fooling the alternator,is it. The next question is:- When you stop the engine, does this also stop the vehicle battery from charging the leisure battery?? Presumably the circuit from the vehicle battery to the leisure battery is interupted at the same time or the vehcle battery will loose a lot of power, even go flat?? Also is the leisure battery being charged from he vehicle battery only or is it also connected to the alternator via the normal circuit?? I would not think so. I must ask Stirling Power more about it. It is on a different track to the usual well tried systems, but on the face of it, it looks a logical alternative, but I would think the vehicle battery might suffer from being very hard worked, ie:- getting rather heated and shortened working life. Fascinating!!!
userClive
Posted: 29 January 2005 12:07 PM
Subject: Battery charging on the move
 


Hi all,
Derek is correct you also have to include charging the starter battery. If the maximum output of the alternator is 100 amperes for example then this has to be divided between all the batteries that require charging. Adjust the maths accordingly.
My principal problem with the Stirling aproach is that in order to keep the charging amps at maximum until the battery is almost fully charged requires that the voltage be allowed to rise well above 15 volts, to levels that can damage equipment or significantly shorten the life of very bright bulbs should they be turned ON.
As I said before, if the load circuits are all disconnected when Sterling charging is taking place and you don, minde much more frequent top ups with de ionised water then do it.
But just remember, if the vehicle manufacturers wanted to adopt the sterling principle as standard they could at zero cost. It would mean a different regulator chip in the alternator.
Ask yourself why these techniques are normally only used for charging Fork Lift Truck and Milk Float batteries??
Sorry Derek, I am not convinced!


On the 80% charged arguement just think on this, which is easier and quicker to carry from tap to motorhome, one 2 gallon bucket filled to the brim with water OR 2 buckets both half full? Which method spills less water?

It'l soon be summer!


userWilliam R Dunstone
Posted: 30 January 2005 6:00 PM
Subject: Battery charging on the move
 


I have tried to put over what the Sterling battery to battery charger does in very simple terms. It is £250 worth of very, high tech gizmo and with due repect Clive is very different to anything I have come up against before.
I am actually using one and it isn't doing any of the things you suggest, except it will use more water in battery - that is inevitable with anything that actually fully charges a battery. I am running my laptop, Gps, lights, etc and no problems so far!
BillD
usernick dean
Posted: 2 February 2005 2:53 PM
Subject: Battery charging on the move
 


i have read alll the various messages and think i might have a solution!!! buy a s/hand large 12volt starter motor ( aprox 200-600 amp rating) motor in reverse will = dynamo attach to wheel via pulley on old pair m cycle rear forks adapted. make tow bar and tie behind camper on tow ball.2-3 hours journey should give all charging current required . system may have a few teething probs like geting hot but airflow should suffice to cool generator. if burning plastic. is smelt your probably not using thicker enough cables .lights will be very bright and batteries will smell of rotten eggs also when fully charged . in either case disconect charge . immediately. a rope attached over roof of camper to generator so as it can be raised or lowered onto road to regulate charge . will also save having to stop and go round to back of camper now and then . ie you now have semi automatic charging/ regulation. boy what a selling and conversation point.!!!!! if it works well sugest try a tenner for a tip . and patent it quick.as everybody willl want one.!! if not too succesfull try a proprietory company as suggested by other readers but unfortunately willl probably cost you considerably more . but give you piece of mind. good luck.
userColin T
Posted: 2 February 2005 7:14 PM
Subject: Battery charging on the move
 


Dear Nick!
I have been using this solution for the past few years now and the batteries do not over-charge as any surpless power generated has been fed into the natioal grid. What I now find is that this limits our journey distance due to the restriction of long cable runs, but thanks for the thought anyway

Colin
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