Another Battery Question

[grumpyengraver]

Hi, thanks to everone on my last post.
I have another question that perhaps you can help with! My VW T4 has both batterys under the bonnet side by side. 110amp for the Main and 65amp for the Leisure.
Do you think that 65amp would be big enough for the Main Battery and then I could use the 110amp as the leisure battery.
I intend to replace both batterys in the spring so I could get a 110amp Leisure Battery and a new 65amp Normal Battery for the Main Battery, I would have to get longer leads for the Main one as the ones fitted are not quite long enough.
The van engine is the 2.4D so neads quite a lot to turn it over but it is a very good starter.

Regards

Tony

 

[oldish hippy]

some t 4 have lesuire battery under drivers seat or passenger seat

 

[grumpyengraver]

some t 4 have lesuire battery under drivers seat or passenger seat

Hi, no room I'm afraid, all space taken up with the wife bits and bobs :lol-049:

Tony

 

[Firefox]

There are some control panels you can get which you can switch between engine and aux batteries to use as your power source. You have to be a little careful and keep an eye on the voltages as you are using them but it does give you useful extra capacity espec when you have a big engine battery going spare.

With some original campers like the HA Dormobile there was only the one small engine battery for everything and no voltmeter :scared: But we used to do several days camping on one site and use the battery for interior lights/radio etc. There weren't any big power draws. Never got stuck starting up again either. Sometimes it was a bit sluggish turning over after a dew days, but that was only a 1159 cc petrol engine.

 

[landyrubbertramp]

There are some control panels you can get which you can switch between engine and aux batteries to use as your power source. You have to be a little careful and keep an eye on the voltages as you are using them but it does give you useful extra capacity espec when you have a big engine battery going spare.

With some original campers like the HA Dormobile there was only the one small engine battery for everything and no voltmeter :scared: But we used to do several days camping on one site and use the battery for interior lights/radio etc. There weren't any big power draws. Never got stuck starting up again either. Sometimes it was a bit sluggish turning over after a dew days, but that was only a 1159 cc petrol engine.

To Firefox
Hi Firefox can i pick your brains once again. With regard to my 2 110amp batteries if they were at say 10.0v and the inverter cut out and i then connect the batteries to my car battery and turned the car over or went for a drive say to another location given that the alternator i thinks put about 13 v to your main battery, does it put 12v back to your lesiure battieres and how long would it take to get my two 110batteries up to say 12.40v. Also given the alternator i assume would be doing more wor does this have a knock on effect to the vehicles fuel consumption?

 

[Deleted member 5816]

Hi, thanks to everone on my last post.
I have another question that perhaps you can help with! My VW T4 has both batterys under the bonnet side by side. 110amp for the Main and 65amp for the Leisure.
Do you think that 65amp would be big enough for the Main Battery and then I could use the 110amp as the leisure battery.
I intend to replace both batterys in the spring so I could get a 110amp Leisure Battery and a new 65amp Normal Battery for the Main Battery, I would have to get longer leads for the Main one as the ones fitted are not quite long enough.
The van engine is the 2.4D so neads quite a lot to turn it over but it is a very good starter.

Regards

Tony

Tony .....A problem with 12 volt battery's is by running the battery down below 12.4 volts shortens battery life and capacity tremendously each time this is done capacity and battery life reduces significantly.You really need your leisure battery testing and one of the only ways to do this if not the only way of testing an open cell battery is to use a Hydrometer if you have not open cells contact a Auto Electrician and have the battery tested by them if you replace the battery get the biggest one that will fit in the space allowed and try not to run the battery flat.

Alf

 

[grumpyengraver]

There are some control panels you can get which you can switch between engine and aux batteries to use as your power source. You have to be a little careful and keep an eye on the voltages as you are using them but it does give you useful extra capacity espec when you have a big engine battery going spare.

With some original campers like the HA Dormobile there was only the one small engine battery for everything and no voltmeter :scared: But we used to do several days camping on one site and use the battery for interior lights/radio etc. There weren't any big power draws. Never got stuck starting up again either. Sometimes it was a bit sluggish turning over after a dew days, but that was only a 1159 cc petrol engine.

Hi Firefox,
My camper does have the control panel but I was a bit fightened to switch to the Main Battery for the reason you say. I think I will be OK and I've always got the genny or RAC if I cant start. I will try the TV out and see how long it last, I will let you know how long the 65amp battery last before the controller starts beeping at me.
Dormobile that was a time ago, you must be my age!

Tony

 

[Deleted member 5816]

To Firefox
Hi Firefox can i pick your brains once again. With regard to my 2 110amp batteries if they were at say 10.0v and the inverter cut out and i then connect the batteries to my car battery and turned the car over or went for a drive say to another location given that the alternator i thinks put about 13 v to your main battery, does it put 12v back to your lesiure battieres and how long would it take to get my two 110batteries up to say 12.40v. Also given the alternator i assume would be doing more wor does this have a knock on effect to the vehicles fuel consumption?

Each time you run the batteries below 12.4 volts you are damaging them and to drop the voltage from 12.4 to 10.0 volts you must have a very heavy load the alternator would need many miles to recharge from such a serious voltage drop

Alf

 

[Firefox]

The alternator will put 14.5 V across both your engine batteries and leisure batteries. (They need the extra voltage to drive the electrons back on the plates)

Given that 10V is 0% charge (they should never get to this stage), lets say your batteries are 50% discharged which is more normal.

Then you have (110 Ah + 110 Ah) x50% to make up = 110Ah.

It depends on your alternator but most basic alternators can supply 30-40 A or so. You can see it will take a good 2-3 hours drive to get them back up to full charge. If you wanted to take them from 12v to 12.4v (50% to 75% approx) that would be 55Ah so 1 to 1.5 hours drive should do it. (If you used a piece of kit like a Stirling charger, this could cut these times in half because it senses battery voltage and delivers exactly what the battery needs to top it up more efficiently. I haven't got one of these... they are expensive but I have seen good reports)

Yes it does have a knock on effect on fuel consumption. The more current you draw from the alternator the more drag on the drive belt. It's not huge for a big diesel engine just like more wind resistance but you could see 1-3 mpg less especially early on when the current will be higher. This is where the HHO generator people delude themselves because they argue that they get the power for free as the alternator is spinning anyway, but usually it spins under little load and there is no drag. So although they make plenty of hydrogen to feed back into the engine they have already paid for it dearly in drag and decreased mpg.

 

[Firefox]

Hi Firefox,
My camper does have the control panel but I was a bit fightened to switch to the Main Battery for the reason you say. I think I will be OK and I've always got the genny or RAC if I cant start. I will try the TV out and see how long it last, I will let you know how long the 65amp battery last before the controller starts beeping at me.
Dormobile that was a time ago, you must be my age!

Tony

I wouldn't take too much out of the engine battery, but you could probably take 15-20% say down from 12.8 volts to 12.6 or 12.5volts. That would give you an extra 20 Ah or so, which is useful. You could try taking 20% at home and see how easily it starts. It should be no problem. If it is, then you know to take less. Use the engine battery last, only if you need to as a reserve. Then it will be less time to when you start and charge it again. The shorter the time, the better for the battery, and as it is nominally a starter only battery, that will take more care of it.

As for age I'm just turned 48, born Dec 1963 ;-) So we had the Dormobile in the family from about 1970 to 1995 (working) and from 1995 to 2011 (stored).

 

[Deleted member 5816]

[As for age I'm just turned 48, born Dec 1963 ;-) So we had the Dormobile in the family from about 1970 to 1995 (working) and from 1995 to 2011 (stored).[/QUOTE]

given those dates do you mean the CA Bedford Dormobile with the sliding doors the Ha did not come out untill later I think

Alf

 

[teemac]

can i hijack this a little please?... (or please move it to the right - its own thread :bow

firstly...please forgive my naievity.....but i have 2 batteries just for the electrics (lights, flush) use inside the ...erm?....non drivable mobile home...lol. :drive:

one is a bog std 75ah battery of a van and onother i beleive is a 85 ah leisure one.

my question is what is the best way to use them...ie individualy or i have heard the words in parallel in inline...i understand what those terms mean but no idea in techie terms if it is worth doing?

be gentle guys please...:lol-053:

 

[Firefox]

Don't connect in line (ie in series positive to negative etc or you will get 24v and blow your 12v appliances)

The best way to use them is in parallel.

Ie Connect negative to negative to earth (vehicle body) And positive to positive to your fuses then appliances. Then earth your appliances through the body locally. ( I actually have a separate earth wire going back to the batteries negative (more like boat wiring) on my van - it all comes to the same thing but my system is a bit more reliable)

BUT If you have two batteries of different sizes and makes and ages, wiring them in parallel is not such a good idea as one will be weaker and other will discharge into it. Ie one will pull the other down. In your case I would just use the best battery out of the two ie probably the 85A leisure one. Then when that wears out buy two new batteries of the same size and make and age and connect them in parallel as above.

 

[Firefox]

[As for age I'm just turned 48, born Dec 1963 ;-) So we had the Dormobile in the family from about 1970 to 1995 (working) and from 1995 to 2011 (stored).

given those dates do you mean the CA Bedford Dormobile with the sliding doors the Ha did not come out untill later I think

Alf[/QUOTE]

No I mean the HA which was the smaller one on the Viva van, which was made from 1967 to about 1974 I think. Ours was an F Reg 1968.

 

[teemac]

i understand......thanks firefox x.:cheers:

 

[Bernard Jones]

Battery size

Don't connect in line (ie in series positive to negative etc or you will get 24v and blow your 12v appliances)

The best way to use them is in parallel.

Ie Connect negative to negative to earth (vehicle body) And positive to positive to your fuses then appliances. Then earth your appliances through the body locally. ( I actually have a separate earth wire going back to the batteries negative (more like boat wiring) on my van - it all comes to the same thing but my system is a bit more reliable)

BUT If you have two batteries of different sizes and makes and ages, wiring them in parallel is not such a good idea as one will be weaker and other will discharge into it. Ie one will pull the other down. In your case I would just use the best battery out of the two ie probably the 85A leisure one. Then when that wears out buy two new batteries of the same size and make and age and connect them in parallel as above.

Sorry to disagree, but it isn't really the size that is the problem. There is no reason why you can't have a 50 amp hour and a 100 amp hour of the same voltage joined in parallel. The problem is that batteries gradually discharge themselves, the older and worse condition they get, the faster they discharge themselves. So you can get to the stage where one is discharging the other, you don't notice it until it becomes really bad. This is why they suggest having two as evenly matched, in terms of age and type, as possible. But a small battery will not discharge a big battery, or vice versa, if they are in similar condition. Because they will be the same voltage. The power going in, and out, to each battery will automatically adjust to its capacity, through its resistance.