Jump to content
Pete and Tracey

Battery and charging Q's

Recommended Posts

G'day Russ

Thanks for your answer, as always very helpfull & understandable.

I'm interested in how the wiring & thus charge from the Tow Vehicle is handled. In your wiring diagram it shows the wire from the Tow Vehilce going to the Solar Regulator, but them jumping to the 1st battery. Does this mean the charge bypasses the SR & thus LinkLITE & not used in its calculation of the SOC?

Further, when I get my sparkie to wire in the DC to DC Charger into the Kedron does he have to put this just prior to the battery or should he pick up the cable before the Solar Regulator? The fuse from the Tow Vehicle is just beofre th battery & therefore I suspect its bypassing the Solar Regulator, but I'm not sure.

Thanks & cheers

Alan

Hello Alan

The connection you refer to is best described like this:

There is a connection from the battery -Ve to the Solar Regulator. This is the connection through which the Solar Regulator charges the battery. The current flowing through this connection is measured internally by the Solar Regulator.

The other connection from the battery -Ve goes to the shunt. Everything connected to the other side of the shunt is either supplying current to, or drawing current from, the battery. The shunt measures the net current flow, either in or out of the battery, and relays the information (in my case) to the Solar Regulator. The Solar Regulator then sums the internal and external (shunt) current flows to get an accurate picture of the battery status.

In your case, you would need to take a different approach because you use the LinkLITE to monitor your system. You will need to have every source or demand of current connected to one side of the shunt and the battery connected to the other side. Under these circumstances the LinkLITE will be appraised of the net current flow to or from your battery and should be able to accurately show the SOC. Any readings, other than the voltages and output current, shown on your Solar Regulator will be inaccurate and meaningless.

If you are going to fit a DC to DC charger (I wouldn't*), then its output will also connect to the opposite side of the shunt from the battery connection.

* In my opinion, the best approach to getting sufficient current to the battery in the van, when using the vehicle alternator, is to use very heavy cables that minimise Volt drop. Teamed with some form of low voltage cutout device at the vehicle battery end, this is as simple as it gets. No further electronics to go wrong. I use this method and the batteries are like new after almost four years. The car's cranking battery lasted five years, so there was no detrimental effect to using a straight-through system as far as I can see. Additionally, in this straight-through setup, the van battery bank can be used to run accessories in the vehicle (such as a car fridge) or to even back-charge the car battery, when the car is not running. Batteries are actually more forgiving than they are made out to be and the use of expensive and fault-prone gizmos can be avoided by keeping this in mind.

Cheers

Russ

Share this post


Link to post
Share on other sites

G'day Alan

...

If you were seeing three Amps of charge current, no discharge current and your batteries still went flat, it would seem that the batteries are U/S. This can happen for a variety of reasons including: Discharging too deeply too often; Not charging the batteries at all when the van is in storage (causes sulphation): Individual dropped cells within batteries and so on. Individual cells can fail by going short circuit, or by going open circuit. In the latter case it results in the battery being completely dead and in the former case the battery thinks it is now a 10 Volt battery, not a 12 Volt battery (which is very bad because the regulator still thinks it is 12 Volts and the end result is that the five remaining cells in the battery have their voltages raised well above tolerable levels.)

You scenario doesn't sound good but I can't be of much more help without getting my hands on your van, or some readouts being made available, sorry. Who knows, it might be something as simple as a bit of bird poo?

Cheers

Russ.

G'day Russ

What's the best for the Kedron Batteries when the van is in long term storage (more than 4 months at a time)? Our van is warehoused when not in use, we have 240V power available for it but no sunlight.

The power is basically "free" power, so should we leave the van connected to 240V all the time? If I leave it disconnected & everything turned off, the charge drops to around 90% within 2 weeks, appears there is some drainage going on even though everything is turned off in the boot.

However as we have 240V power there the easiest thing to do is to leave the power connected but still with everything turned off.

Would it be better for the batteries if a got a 7 day timer that kicked the power in for a few hours once a week?

Cheers

Alan

Share this post


Link to post
Share on other sites

Hi Alan

I would leave the van connected to 240 Volts all the time. The charger will settle into Float mode and will keep the batteries where they should be. Otherwise, there is a plethora of 240 V to 12 V maintenance chargers available for vehicle batteries. These usually just clip onto the battery poles and supply a trickle charge to the batteries. If well designed, they will supply just enough current to replace the internal losses that occur within the batteries.

I wouldn't bother with a timer. Either method should be perfectly OK to leave running all the time. I would, however, visit the van periodically and make sure that the charging device (whichever type you choose) has not tripped off for any reason. By the way, the internal losses of AGM batteries should not be as much as you are experiencing, so look for something that is still drawing current. Make sure that the TV antenna booster for your Winegard TV antennas is turned off. If you want to be absolutely certain that the batteries are isolated, disconnect everything from the positive battery Terminal except for your charger. (This includes the solar regulator.)

Cheers

Russ

Share this post


Link to post
Share on other sites

Hi Alan

I would leave the van connected to 240 Volts all the time. The charger will settle into Float mode and will keep the batteries where they should be. Otherwise, there is a plethora of 240 V to 12 V maintenance chargers available for vehicle batteries. These usually just clip onto the battery poles and supply a trickle charge to the batteries. If well designed, they will supply just enough current to replace the internal losses that occur within the batteries.

I wouldn't bother with a timer. Either method should be perfectly OK to leave running all the time. I would, however, visit the van periodically and make sure that the charging device (whichever type you choose) has not tripped off for any reason. By the way, the internal losses of AGM batteries should not be as much as you are experiencing, so look for something that is still drawing current. Make sure that the TV antenna booster for your Winegard TV antennas is turned off. If you want to be absolutely certain that the batteries are isolated, disconnect everything from the positive battery Terminal except for your charger. (This includes the solar regulator.)

Cheers

Russ

G'day Russ

Thanks again for your most helpful hints. I'll keep it on all the time as you suggest & make sure it's OK periodically.

We get about a 0.2Amp drain showing on our meter in the van with everything off (including the TV booster which we always turn off). Even with the Brake Safe charger off & every other possible thing I know of in the van. I know this is high & I've been chasing this since day 1. But I just can't get it below this. Sometimes its drops to 0.1A but then it soon jumps up. I'll try the Solar Regulator, as I haven't tried that one before. I guess to turn it off I will have to pull the 50A fuse. I would like to know where this power is going, so I'll work continue to work on this.

Cheers

Alan

Share this post


Link to post
Share on other sites

Pete and Tracey

From the point of view of a retired Electrical Engineer who has designed and run solar power systems for 20 years or more - a couple of points.

The difference between the open circuit solar panel voltage and the MAX voltage or system voltage you are reading at the end of the day is the potential difference available to drive current into your battery bank. Don’t bother about it, leave that to the regulator.

As the operator of the system on your Kedron watch two things.

State of Charge (SOC) and MIN system voltage.

Today’s small solar regulators are really Programmable Logic Controllers, called PLCs. In essence they consist of a bunch of counters fed by voltage sensors. To get to the SOC reading the PLC counts the Amp Hrs IN and the Amp Hrs OUT and adds em up. The SOC even though it has some inaccuracies is a fairly useful figure if you watch it over time, say a week or two. Interestingly if you read SOC one can at times see a figure above 100%, the Plasmatronic regulators can read up to 127%. How I hear you ask can a battery bank be measured at 127% of its rated capacity. The answer is that there are daily inaccuracies in the adding of the IN and OUT values that allow the figure to creep up. With the Plasmatronic regulators, hold the button for five seconds while reading SOC and the SOC figure will reset to 100%. Other brand regulators have resets as well.

Probably the most important thing about batteries is that to operate them in a deep cycle mode i.e. use a large portion of their rated capacity will unfailingly lead to a short battery life. This comment applies to all batteries, deep cycle included. I have 3 X 120A/Hr batteries in our Kedron so my overall capacity is 3X120=360 A/Hr. However when the SOC reads 75% I start the generator. So in other words even though I am towing around 360A/Hrs of capacity I only am prepared to use 25% of that or 90A/Hrs. When the van is parked up I use a trickle charge. Operating this way should give me good battery life.

As a backup measure of how the batteries are holding up watch MIN volts on your controller. On a typical Kedron setup it should almost never drop below 12V. An almost dead flat battery will quite happily read 12V with a multimeter across the terminals. One has to ask the same battery to deliver a substantial current and then read the resultant terminal voltage to detect a discharged or sulphated battery. It is called load testing. If you are seeing 11.6 or 11.8V at night after the evening load save up for buying new batteries.

Your panels at 4 X 130W have the theoretically capacity to deliver 43 Amps to the regulator, but they won’t do that. The efficiency of solar panels is highly dependent on their temperature. By the time the sun is well overhead they are quite warm and their efficiency will have dropped considerably. As a last point I will mention Peukert’s Law which has the effect of reducing the energy available from a battery. The conversion of an electric current form of energy to a chemical form of potential energy and then back to an electric current has a cost. The cost is described by Peukert’s Law. As a rule of thumb work on 90 to 93% of available solar output being available back at a load such as your DC light in the caravan.

In short monitor your SOC fairly closely, and more often during poor solar weather and use MIN voltage as a important backup indicator.

I hope this ramble is helpful.

Grahame

Share this post


Link to post
Share on other sites

Hello all' I may be new to kedron but am certainly familiar with PL20 Plasmatronics and have been using this unit for a long time and it is excellent. My comment however, refers to batteries and in particular discovering successful ways to desulphate batteries that are getting tired, and there is circuitry about that enables this that actually works and I have made six of these units now and when used in conjunction with a genuine old style 2 amp trickle charger work very well in my experience. These units work off battery voltage directly and have an led that lights up and use about 300-700 milliamps/hour during operation. If anyone is interested in doing this I will cheerfully direct those handy with a soldering iron where to buy the kits from and the mods that can be made for more muscle if required. If used regularly as a preventative measure [not connected all the time-not necessary] battery life can be extended significantly and if used in conjunction with 1. an accurate specific gravity reader and 2. a battery tester [100 amps shorting load for 10 seconds] you can find out how well the desulphator is working over a period of days or longer by testing the battery directly. I am at present making a variant that has a built in idiot proof on/off switch [it does matter which lead is put on first but correct switch wiring removes this possibility] and a low amp trickle charger that should be switched on after the unit is started and the red led lights up [which means its working and there is also a humming sound as well. I am happy to email this info if asked to do so. Cheers. Mark Email me

Share this post


Link to post
Share on other sites

G'day Russ

In your previous posts you've stated not to go below 75% of SOC = around 12.35V.

With the batteries around 12.5V our new inverter pulls the voltage down to around 12.1 to 12.2V when it's making a cappuccino (< 1 minute). But immediately it's stopped (no sun as I tested this with the van in our factory) it bounces back to the previous voltage reading. Only after about 4 cups does it start to drop the voltage & then only by 0.1V at a time. So I hope it's quite economical.

However should I be concerned about the voltage dropping to 12.1V for the < 1 minute the cappuccino machine is running?

Thanks.

Cheers

Alan

Share this post


Link to post
Share on other sites

The "bounce" that you describe is characteristic of lead-acid batteries. It is all to do with the chemical reaction taking place inside the cells. For the battery voltage to drop so much initially I would make the following assumptions:

*The current drawn by the coffee maker is quite high.

*For this kind of appliance a battery bank capacity that is somewhat larger than you have now would work better.

The second point is born out by the fact that after four operations, the battery voltage begins to drop by 0.1V each time to coffee maker is used. Given the starting voltage of 12.5 V, and it takes approx one minute per cycle for the coffe machine to do its thing, it means that after just 8 serves your batteries are going to be technically flat.

Put simply, the more battery capacity you have, the longer they can deliver a given current. Since we all have weight and space constraints in our vans, increasing battery capacity is usually not possible. So the short answer is, to preserve your batteries, limit your coffee consumption and give the batteries a chance to recharge between cups.

Running 240V appliances on 12 V systems soon exposes the weaknesses.

Cheers

Russ

Share this post


Link to post
Share on other sites

The "bounce" that you describe is characteristic of lead-acid batteries. It is all to do with the chemical reaction taking place inside the cells. For the battery voltage to drop so much initially I would make the following assumptions:

*The current drawn by the coffee maker is quite high.

*For this kind of appliance a battery bank capacity that is somewhat larger than you have now would work better.

The second point is born out by the fact that after four operations, the battery voltage begins to drop by 0.1V each time to coffee maker is used. Given the starting voltage of 12.5 V, and it takes approx one minute per cycle for the coffe machine to do its thing, it means that after just 8 serves your batteries are going to be technically flat.

Put simply, the more battery capacity you have, the longer they can deliver a given current. Since we all have weight and space constraints in our vans, increasing battery capacity is usually not possible. So the short answer is, to preserve your batteries, limit your coffee consumption and give the batteries a chance to recharge between cups.

Running 240V appliances on 12 V systems soon exposes the weaknesses.

Cheers

Russ

G'day Russ

Thanks for your answer, as always very informative.

The use of the inverter is for only 2 cuos before the sun hits the panels or before we put the generator on, so it should be OK providing they aren't too flat.

Have a great Christmas.

Cheers

Alan

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...