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Double battery 12v or 24v


sundance

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We have a leisure battery on a split charge relay running 2 pumps and 2 electric reels.

Once we reach our destination we hardly travel any distance, towards the end of the day the electric reels struggle so we start the van to help.

The battery is 130ah i have bought another identical battery.

If we link the two battery's and connect to the positive on one and the negative on the other will it be still 12v or 24v

And will the pumps be ok if 24v

I am going to do it myself as the auto electrician has to isolate for two weeks.      

Edited by sundance
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55 minutes ago, sundance said:

We have a leisure battery on a split charge relay running 2 pumps and 2 electric reels.

Once we reach our destination we hardly travel any distance, towards the end of the day the electric reels struggle so we start the van to help.

The battery is 130ah i have bought another identical battery.

If we link the two battery's and connect to the positive on one and the negative on the other will it be still 12v or 24v

And will the pumps be ok if 24v

I am going to do it myself as the auto electrician has to isolate for two weeks.      

Joining 2 batteries together like you describe adds amps not volts. So volts stay the same but amps double.

However, you need 2 batteries as close to identical to do this. If you are having problems with the first battery holding charge then adding another battery will cause the new one to go flat as it will be feeding the incapacity of the original battery.

So if you want to do this then you need to replace the original battery as well with the identical make and capacity of the one you have just purchased.

Your electric reel has a 24v motor. If you put 24 volts in to power it you will double the speed the motor spins at. That wouldn't work for your hose reel.

I very much doubt your 12v pumps will last running on 24v either. What about your controller? Its 12v.

The other issue you have is charging a 24v battery bank. Your vans alternator is 12v so you can't use your split charge relay and you will need to get a 24v charger. Using a battery bank of 260 amps will mean a higher capacity battery charger anyway.

The most important thing here is the type of battery you are using. It could well be that if you are winding in 2 hose reels at once you are asking the battery to work harder than it is designed to work as a leisure battery. Two hose reels could well be drawing 40+ amps.

You should be looking at either a traction battery or a combo leisure and starter battery; a leisure battery with a CCA rating.

My personal advice to you is to seek professional advise from an auto electrician. Judging by your post you appear to have very limited knowledge of things electrical. It could end up costing you if you get it wrong.

Edited by spruce
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1 hour ago, sundance said:

We have a leisure battery on a split charge relay running 2 pumps and 2 electric reels.

Once we reach our destination we hardly travel any distance, towards the end of the day the electric reels struggle so we start the van to help.

The battery is 130ah i have bought another identical battery.

If we link the two battery's and connect to the positive on one and the negative on the other will it be still 12v or 24v

And will the pumps be ok if 24v

I am going to do it myself as the auto electrician has to isolate for two weeks.      

I have two leisure batteries connected to a Durite SCR. They are wired to each other in parallel ie, positive to positive, negative to negative. As per jump starting. This keeps the voltage at 12 but combines the ampage. This will not damage your 12v system. Wiring them in series: positive ~ negative ~positive ~earth will double your voltage to 24v and may well damage your 12v systems. Someone with more knowledge may have a definitive answer. I would secure the batteries in boxes to make sure the poles are protected from shorting if anything metal was touched across them. I'd also make sure that the positive wires are protected by fuses close to the positive poles.

I'm no expert by any means but I do have a fair degree of experience with batteries. My SCR keeps the batteries charged. I have never needed to mains charge them. I reckon they are probably about 70% charged on average. I believe batteries last longer if they are kept in a fairly good state of charge rather than if they are kept fully charged. One of mine is well over 6 years old and the other about half that age. I should add that we use two pumps but we don't use electric reels, so our battery use won't be as heavy as a lot of people.

Spruce's advice about getting professional help is the soundest way to proceed.

Edited by Davy G
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The most important thing here is the type of battery you are using. It could well be that if you are winding in 2 hose reels at once you are asking the battery to work harder than it is designed to work as a leisure battery. Two hose reels could well be drawing 40+ amps.

You should be looking at either a traction battery or a combo leisure and starter battery; a leisure battery with a CCA rating.

Thats the problem 

Thank you again 

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Before jumping to add an extra battery check the voltage when things are struggling and when you arrive at your first job. It could be that the battery is not getting fully charged while driving round. If you take more than 50% of the capacity out of the battery you will start to destroy it. So on a leisure battery that says 100Ah if you take more then 50 Amps out then you will be damaging it!!!

Check out the voltages first, the current battery may be failing due to age or useage.

At a guess your electrician is probably best person to test things.

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9 hours ago, ched999uk said:

Before jumping to add an extra battery check the voltage when things are struggling and when you arrive at your first job. It could be that the battery is not getting fully charged while driving round. If you take more than 50% of the capacity out of the battery you will start to destroy it. So on a leisure battery that says 100Ah if you take more then 50 Amps out then you will be damaging it!!!

Check out the voltages first, the current battery may be failing due to age or useage.

At a guess your electrician is probably best person to test things.

The trouble is that an auto electrician who deals with car electrics may not have the expertise when it comes to leisure batteries. An auto electrician working in the leisure industry (caravans and motorhomes) or wfp fitters (Purefreedom, Grippatank, etc) are probably more experienced in the electrical demands of our industry.

It's easy to test a starter battery's condition by putting a heavy load on it and watch how the tester voltage gauge behaves. Better equipped workshops have a tester which electronically tests a battery and determines its state using a preset algorithm.

Both of these testers don't work on leisure batteries. As you say, the symptoms that the o/p is describing points to either an under charged battery at the start of the day or to a battery that has lost its capacity due to 'overloading'.

Once we start adding stuff that draws heavy current we need the right battery chargers and the right batteries.

One of the cleaners has a YouTube video clip out of Purefreedom  fitting a diesel heater to his system and then a second fitting 2 electric hose reels.

Purefreedom added a second battery and a Sterling battery to battery charger.

When Grippatank fit diesel heaters they also add a second Numax combo starter/leisure battery with their b2b charger they supply.

 

Edited by spruce
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