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Battery and charging Q's


Pete and Tracey

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Hi Alan,

yes, the Xantrex unit is the solar regulator in your case. It also seems that the only problem that you may have had before was shade on the panels. We get very strange looks when we pull up at campsites and park right out in the full Sun. People think that we're nuts, but we are completely self-sufficient when it comes to power. So much so, that we are going to sell our generator because we just don't use it.

Cheers

Russ

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Pleased this topic (in general) is alive again.

Our 240V/12V Power Supply ('transformer') died. Incidentally, in contradistinction to an earlier post regarding the purpose of this bit of electronic wizardry, I think all it does is supplies 12V DC from an external 240V AC input so that all (not the fridge) the 12V supply to the van is NOT from the batteries. I may be wrong but I deducted this from the fact that when plugged in to an external 240V supply, and with the switch in the 240V position, I had no 12V supply in the van at all (but had 240V) and when I flipped the switch to the centre position or in the off position, I still had 240V supply, and 12V but directly from the batteries (well, not directly, but you know what I mean).

So, having removed this unit from the van - with the help of mirrors, strangely shaped screwdrivers and various anatomical contortions, Bainbridge Electronics is prepared to repair/replace the unit under warranty but I'm not sure I should refit it. If I don't because the van is still perfectly operational without it, what do I do with the dangling 12V wires? Simply wrap a bit of insulation tape around them and leave them? Do I have to do anything with them at all? And finally, it seems this bit of electronics is redundant anyway - should I bother replacing it at all?

Cheers

Brian

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Pleased this topic (in general) is alive again.

Our 240V/12V Power Supply ('transformer') died. Incidentally, in contradistinction to an earlier post regarding the purpose of this bit of electronic wizardry, I think all it does is supplies 12V DC from an external 240V AC input so that all (not the fridge) the 12V supply to the van is NOT from the batteries. I may be wrong but I deducted this from the fact that when plugged in to an external 240V supply, and with the switch in the 240V position, I had no 12V supply in the van at all (but had 240V) and when I flipped the switch to the centre position or in the off position, I still had 240V supply, and 12V but directly from the batteries (well, not directly, but you know what I mean).

So, having removed this unit from the van - with the help of mirrors, strangely shaped screwdrivers and various anatomical contortions, Bainbridge Electronics is prepared to repair/replace the unit under warranty but I'm not sure I should refit it. If I don't because the van is still perfectly operational without it, what do I do with the dangling 12V wires? Simply wrap a bit of insulation tape around them and leave them? Do I have to do anything with them at all? And finally, it seems this bit of electronics is redundant anyway - should I bother replacing it at all?

Cheers

Brian

G'day Brian

I removed my 240VAC to 12VDC unit years ago. It's still in my shed if you really want one, but why bother? The main thing you need to consider is that if your batteries are low (say after an extended cloudy period) and you turn on your 240 Volt charger, will it have the capacity to charge the batteries at a decent rate AND provide enough current to supply the van load at the same time? I have a 60 Amp charger and I'm satisfied that this is enough capacity for such an eventuality. Having said that, in all the time that we've had our van we have never been in a situation where we've not had enough sunlight to keep us going.

Your call, but for my money the failed unit is an unnecessary piece of redundancy that is not required.

Cheers

Russ

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Hi Brian,

I agree with Russ. Ours is turned off and has "never" been on since leaving the factory, I asked asked for it not to be installed, but, it was anyway citing the redundancy it provided as the reasoning, our inverter/charger has an 80A charge capacity so have plenty of headroom.

John

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Thanks Russ & John,

I have been in a situation when we ran out of sunlight. Three days in the rainforest at Washpool NP camped in the bush with dense overhead cloud for the duration. Used the generator with permission from other distant campers who reported not hearing it at all. But the gennie ran out of fuel and the spluttering that followed can, so I'm led to believe, (and perhaps, did) create mischief in the form of voltage spikes, which fried an element or two in the charger and it failed when next connected to an external 240VAC supply and needed to be replaced.

Off the top of my head, I don't know what the Amp rating of my charger is but I also don't know what the downside is if one has a lower Amp rated charger and one has to use an external 240VAC supply to charge the batteries. Aren't these instruments supposed to be 'intelligent' and will use what they can to charge the batteries while still allowing the 12VDC load to be serviced?

Quite possibly/probably a stupid question, I know.

Cheers

Brian

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Hi again Brian

Yes, modern chargers are intelligent but they can't make something from nothing. Most modern chargers are multiple-stage and by this I mean that they will charge the batteries at certain voltages and currents until set criteria are reached. The three stages are boost, absorption and float. In the boost stage, all the charge current available is used to charge the battery. As the battery charges, its voltage rises. When the voltage reaches the boost maximum voltage and remains there for a predetermined time, the controller will automatically advance to the absorption stage. In this state, the charger tries to keep the battery voltage constant while the last part of the battery charging occurs. This prevents excessive gassing which occurs at high cell voltages. The float stage basically sees the input current match the output current.

The important thing here is the boost stage. If your batteries really could use 30 Amps for this stage to be applied correctly and your charger is only a 30 Amp charger, then the charger simply cannot do both (boost the batteries and supply the load in the van) effectively. Something has to give. If, on the other hand, you have a 60 Amp charger, then you have some headroom available to you. The manual for your charger will have its maximum output current listed in the specification section.

If your battery charger is not a high capacity charger, then the 240VAC to 12VDC can be used to run the load while the charger does its job. On the other hand, you could always upgrade the battery charger, rather than get another 240VAC to 12VDC unit and have one less fan running in the boot.

Cheers

Russ

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Hi Brian,

I think Russ has it mostly covered. My two cents worth would be that if you have to use the 240v to 12v power supply to ensure you have enough current to run a good boost stage then you have a poorly chosen charger which you should probably address.

From a practical point of view and in the event you really do need to run a generator to boost your batteries it would be better to have a larger charger than a small one, your generator won't care either way unless it is tiny, but, your neighbours might, as with a higher boost current the time your generator needs to run will be shorter. You should also endeavour to allow the charger to get to float stage before killing off the generator as the absorbtion stage is as important as the boost stage for the long term benefit of your batteries.

Cheers

John

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Thanks again Russ & John,

So clearly explained and it all makes much more sense now! You are both great assets to these forums. Where do you blokes get your knowledge from? Are there any books available that you could recommend?

My charger is the standard one fitted by Kedron and because my van is currently parked off-site I can't check the rating but I'm reasonably sure it's only 40 Amps. Having said this, if one does have a Mickey Mouse charger and the batteries need a decent charge from say, a generator, then the boost phase will require maximum Amps and the van load (all 12V?) will be sacrificed but this, in the main, will mean that the only thing that may not work will be the fridge - until absorption phase is reached. Is this deduction correct? If so, then considering that the battery charging is likely to take place during daylight, not having the fridge working for a while may not be a train smash; inconvenient but not a catastrophe. Is my reasoning reasonable?

Cheers

Brian

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Hi Brian,

The knowledge in my case comes from a life in the electrical industry, as to the book, I suggest you would get much better value out of asking away in a forum such as this as your specific needs are more likely to be addressed, there's a wealth of knowledge out there which captures both the theoretical and practical side of the issue. Buying a book is less engaging and potentially might only serve as a means to an afternoon nap.

You've got the tiger by the tail so to speak. Any sacrifice of DC load would be something you would have to create as all of your DC systems will continue to function as normal including the fridge. The trade off being a longer boost cycle as the batteries will not get the full charger output, it has to be shared around over the whole system.

CheersJohn

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Thanks again Russ & John,

So clearly explained and it all makes much more sense now! You are both great assets to these forums. Where do you blokes get your knowledge from? Are there any books available that you could recommend?

My charger is the standard one fitted by Kedron and because my van is currently parked off-site I can't check the rating but I'm reasonably sure it's only 40 Amps. Having said this, if one does have a Mickey Mouse charger and the batteries need a decent charge from say, a generator, then the boost phase will require maximum Amps and the van load (all 12V?) will be sacrificed but this, in the main, will mean that the only thing that may not work will be the fridge - until absorption phase is reached. Is this deduction correct? If so, then considering that the battery charging is likely to take place during daylight, not having the fridge working for a while may not be a train smash; inconvenient but not a catastrophe. Is my reasoning reasonable?

Cheers

Brian

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Hi John,

Yes, of course!

And you're absolutely correct about the 'specific needs' and the 'theoretical and practical' points you make. There's a considerable leap from the theoretical to practical knowledge side of things. Hope you guys are around when I next run into trouble.

Cheers and many thanks,

Brian

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  • 1 month later...

G'day Russ

Earlier in this topic you posted a SOC percentage table. Also it’s mentioned not to let your SOC fall below 75%. Is your chart for AGM batteries or do they have a different chart?

Our TopEnder has 3 x 120 A/Hr AGM batteries.

We’ve been free camped for 5 days at Cape Range NP and then 5 days at Ningaloo Station, and I’ve been watching our SOC every day. This has me a little confused and I hope you are again able to clarify some points for me.

Early in our stay I was getting readings where the SOC was at 75.1% when the voltage = 12.7V, this reading was always noted early morning before sunrise. At night I was getting SOC = 91.6% when it was displaying 13.0V, again this reading was taken without daylight.

However 10 days later our SOC before sunrise was 65% with 12.5V. According to your chart 12.5V = 90%. It seems to lose a little of the SOC every day, but it was worse after we moved from Cape Range to Ningaloo.

The Xantrex solar regulator later that day was going into Float mode (solid light) with 13.6V but the SOC = 83.9%. Before going into Float mode the voltage gets up to 14.1V but mostly around 13.9V. According to the Xantrex manual this is expected.

I therefore reset the LinkLITE when it was at the Float stage. Was this the right thing to do?

When we’re on 240V for a few days the charge rests at 14.1V. Our Xantrex LinkLITE battery monitor inside the van has the Chargers float voltage set at 13.6V, I don’t know what our solar regulator float level is set at, I’ve never opened the Xantrex C35 to check.

Do you see any concerns about the above? I would appreciate your input and clarification.

Cheers

Alan

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G'day Alan

All Lead-Acid batteries deteriorate when discharged. Some less so than others. The depth of discharge of 25% (State of Charge 75%) is an arbitrary figure I choose to aim for to get the maximum life from my AGM batteries. AGM, Gell Cell and other "deep cycle" batteries can tolerate deeper discharges but their life does shorten more the deeper the discharge is - it's just that they will outlast wet cell batteries discharged the same amount. So, the more effective your battery management, the longer any kind of battery will last.

The table of Volts Vs State of Charge that I published earlier is just a guide. If (and it is a big if) your regulator is correctly wired amd ALL ingoing and outgoing current flows are measured, then the state of charge as displayed should be spot on. The problem arises when charge current from the 240 Volt charger or the car's alternator is not calculated by the LinkLITE. An erroneous reading will result.

From the figures you have supplied, the Xantrex is doing the job. It is allowing the battery voltage to rise above the Float voltage for a while during charging, before dropping back to 13.6 V on Float. This is exactly what it should be doing. Reseting the LinkLITE at the exact moment that the batteries go from the Absorption stage to the Float Stage will give you a State of Charge that is as near as dammit correct.

The long and short of it is: If you have 12.5 Volts in the morning, just before solar charging starts, then you are in pretty good shape - especially given that it is almost winter and the number of hours of effective charging that you can expect in a day is around 2 hours less than in summer time. About what time of the day are your batteries going into Float mode? It may be that the angle of the Sun is such that the panels can't quite provide you with enough energy, later in the day, to completely finish the Absorption stage and the regulator is forced to drop back to Float mode because of this. This isn't anything to worry about unless you start getting "morning" voltages a fair bit lower than you are presently.

Cheers

Russ

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G'day Russ

Again a really great response which is much appreciated.

I am pleased to know when to exactly reset the LinkLITE, that's good.

Currently here at Cape Keraudren the batteries are going into Float at around 1.00pm, our vans facing ENE & this seems to be almost ideal as it keeps the Float stage going for most of the afternoon as all 3 panels are in full sun (no shade from the aircon on the roof). When we were at Cape Range we were more south facing & even though it was going into Float around noon, a panel was wiped out due to (aircon) shade in the afternoon.

Once the Xantrex C35 goes into Float mode, the manual says it stays in Float for an hour, so if we drop sun during this hour, it stays in Float mode & restricts power. Is this a good thing?

Thanks again Russ.

Cheers

Alan

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G'day Alan

In Float mode the charger should be supplying the same current to the batteries as is being used by your appliances. This is exactly what "Floating" is. As long as you have Sun, you can keep the batteries on Float without affecting the State of Charge. If you lose Sun for any reason, the voltage of your batteries will start to drop. The Xantrex allows for this by checking after one hour and if the battery voltage is below the nominal Float voltage it will switch to either Boost or Absorption mode in readiness for when you next get enough Sun to charge again.

Without looking into the manual for the unit, I can't say for sure whether any other triggers apply to change the mode from Float to one of the charging modes. By this I mean that there may be a hysteresis curve that the unit uses that will override the one hour timer and change mode at a set voltage. Either way, I wouldn't stress about it. If you lose Sun, you lose Sun....and you can't do anything about it. So long as you are aware that your batteries are discharging and keep a casual eye on them, you won't have any issues. If that means turning the telly off an hour earlier, then it's no biggy.

Just an aside: I am in the process of ordering some new batteries for my van. I am going to remove the AGM batteries and them with Lithium batteries, specifically LiFePO4 (Lithium-Iron-Polymer). These batteries weigh about a third of the weight of Lead batteries, for batteries of matching usable capacity. Where they differ is that they can be discharged a lot deeper without any significant shortening of their life. Typically these batteries can be discharged 80% (20% capacity remaining) which means that as long as you have the capability of recharging them again, you can have smaller, lighter batteries and still get the same amount of usable power from them.

This change is not driven by the need to change the AGM batteries because they are at the end of their lifetime....they aren't. It is driven by the revelation that my towball weight is 650 Kg! Not only will I be swapping the batteries but I will also be mounting the new ones under the seats of the café lounge, behind the axles. Being able to discharge them deeper will just be an added bonus. The downside is that it is going to cost $2000.00 to correct a weight distribution issue with the van that shouldn't be there in the first place.

Cheers

Russ

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Russ,

I'm interested in your trip down the LiFePO4 route...

From my research, you need a special charging system. What is your proposed solution? Are your replacing your chargers? Solar regulator?

What size batteries did you settle for and at what cost?

I was under the understanding they were still quite expensive and your $2000 price tag appears quite conservative.

A little info: http://www.energymatters.com.au/index.php?main_page=news_article&article_id=3045

Edit:

And this link from RedArc
/>http://redarc.com.au/user-forums/product-related-please-post-here./lifepo4-battery

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OK, maybe not so expensive:
/>http://ev-power.com.au/webstore/index.php/se100aha.html

These are 3.2V cells... 3.2 x 4 = 12.8V (max 3.9V per cell x 4 = 15.6V)

4 x $137 = $548 + GST per 100Ah

This is the first price I came up with and I assume there are better prices around.

And I like the discharge curve - the voltage is fairly constant all the way to 100% discharge
/>http://ev-power.com.au/webstore/index.php/catalog/product/gallery/id/5/image/270/

40A Battery charger:
/>http://ev-power.com.au/webstore/index.php/charging/12v-4-cell-24v-8-cell-chargers/12v-40a-battery-charger.html

Not sure about solar regulator...

Russ, what configuration are you planning?

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G'day David

You are asking the very same questions that I asked of the LiFePO4 suppliers. In essence, they sell a pre-packed 90 AH battery in a single package (made up of four cells, obviously.) They do not have battery monitoring or charge regulating control boards. The stipulation is that the charging device must be programmable so that at no time does it charge at a voltage higher than 14.4 Volts. On the discharge side of the equation I will be buying an off-the-shelf battery cut-off device that can be set to 12.4 Volts. All of the suppliers I have contacted agree that keeping the battery voltages within those limits will result in long cell life.

Both my solar regulator and my battery charger can be set-up to comply with the upper voltage limit. That said, because I can place the individual cells in pretty much any physical shape that I want in the space that I have, I might still go the whole hog and use cell monitors for each cell and run a series and parallel configuration to achieve 12 Volts and about 360 AH capacity. Either way, the cost will be much the same.

If I go down the pre-packed route, I will be using 4 x 90 AH batteries which will give me a usable capacity of about 280 AH. I currently have 4 x 120 AH AGMs that I don't like to discharge more than 25% - 30%, so I effectively get only 120 AH - 160 AH of usable capacity from those.

There are better prices around but over all there would only 5% in it.

Cheers

Russ

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G'day Russ,

On a practical note, if you're worried about the three AGM batteries you have in your front boot contributing to your extraordinary ball weight, why not just move those batteries to behind the axles as you are planning to do with the lithium, iron phosphate ones? Is it because you really love the technology and have the practical wherewithal to fiddle with all these electron generating devices?

Cheers

Brian

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G'day Brian

If I could have just moved the four AGMs, I would have. Unfortunately, the weight issues I have don't stop at the 650 Kg on the ball. Overall the van is 330 Kg overweight when packed to travel. So I have to shed the 330 Kg as well as move weight aft. Trust me, I wouldn't spend the money if I didn't have to, but I just can't trim enough weight without changing out the batteries. I'm also pretty convinced that if other Top Ender owners take the trouble to weigh their vans they might also be in for a bit of a shock.

Cheers

Russ

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Russ,

Interested in what you are doing with the batteries, like you suggest most TE's are above the 3500 when fitted out for travelling and that is when it counts. We only have a 19'6" van, I don't have the ball weight issues but still have to be careful and can pull ours under 3500 by lowering water levels when travelling not the best option but the one we have decided to live with at present.

cheers

Laurie

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G'day Laurie

We are getting a little off topic here but never mind. I also thought about carrying less water but in the end decided that to use the Kedron for what we bought it for, that is, going on the roads less travelled to the places less stayed, would require us to carry all the water we can. So far I have opted to do away with our bicycles, leave the generator behind (along with the jerry can of fuel that we also carry for it), change the batteries for lighter ones, no longer carry spare oil and coolant for the car (we have lugged ten kilos of each in the front boot of the van for five years and never used a drop), carry fewer tools, leave the Cobb Cooker behind (our BBQ can do anything the Cobb can do), carry fewer paper books and use the iPad instead and lastly, carry less tinned food and long-life milk (we always carry way more than we would ever need, even in an emergency).

Doing all of that will get us to within a few Kilos of where we need to be. Worst case, if we get pulled over by the Mermaids, we can then drop some water or blow off a gas cylinder. If I need to, I will also move one of the two water tanks that are forward of the axles and relocate it behind the axles. I should have weighed the Kedron when we took delivery. At least then I would have been aware of these issues and done something about them sooner. It scares me to think that we have been so over weight for so long (even the car is overweight by virtue of the excessive ball weight.) In the early days we used to carry even more stuff than we do now, so it is not beyond the realms of possibility that we were half a tonne over. It has given me an even greater respect for our beloved Disco 3 and its tiny 2.7 Litre engine.

To get this thread back on track, I intend to publish the whole process of changing over the batteries, along with a critique of how they perform, so that other Kedron owners can use the information to decide what they will do once their AGM batteries reach the end of their life-cycle. It will be a "warts and all" exposé so that others can learn from any problems that I may encounter.

Cheers

Russ

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G'day Alan

The table of Volts Vs State of Charge that I published earlier is just a guide. If (and it is a big if) your regulator is correctly wired amd ALL ingoing and outgoing current flows are measured, then the state of charge as displayed should be spot on. The problem arises when charge current from the 240 Volt charger or the car's alternator is not calculated by the LinkLITE. An erroneous reading will result.

Cheers

Russ

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

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