Portable Power Pack

Thanks Bigfish.
The two options I am considering are both Lithium and rated around 100ah. The work required to install a permanent battery vs the plug in alternative is my dilemma. Either way I’ll include a dcdc charger and both are solar supported. Mainly curious as to whether the packs live up to the advertising hype. In theory they should be the same as a fixed battery.

Kewell, The reviews I have watched on YouTube on these powerpacks are virtually plug-in play but come at a big price tag but very flexible. The reviewers are certainly talking up some of the more newer models .

With the price of ,So called, power packs, you usually can buy an additional lithium 100ah battery instead. Then you have two and much longer charge life for about the same total footprint. A power pack is not my choice.

Thanks Macca.

My research suggests it is indeed a lithium battery (LiFePo4 ) and as you say with attachments. The charging requirements in that regard are little different to a fixed battery except it can be recharged by AC in about an hour. I will install a dedicated dcdc charger which I will Anderson plug to the pack if I go that way. Either option I choose will have the dcdc although it isn't essential for the pack. Your point on this is well made.

Whilst not important to me, having an 1800w pure sine wave inverter included would come in handy and would save the cost of installing one in the van.

The main swaying point at present is the work and cost of installation of a non portable battery. The vehicle is an Isuzu DMax with a canopy over the tub. There is no space under the bonnet for an AGM or similar. The usual method seems to be to install a lithium behind the back seat. That doesn't appeal to me as we sometimes carry grandchildren in child seats that will be fitted over that seat with associated belts etc. I could fit it to the side of the tub where it would need to have some sort of protection around it etc etc.

The pack I am considering is not much bigger than a shoe box and would strap down behind the fridge. When we aren't travelling it could come out. Cost wise they aren't massively more than the comparable batteries.

I have always had fixed dual systems but I guess I wanted to see if people are now considering power packs / stations as alternatives as technology and cars develop. I certainly haven't met many with them.

Thanks again for your interest and feedback.

Kenell

Macca
All the DC DC chargers I have, multiples, all begin when start battery supplying it/them is above a threshold value of voltage and cuts OFF power to the DCDC when the supply battery voltage drops to around 12.7V so no need for a VSR, because the DC DC is effectively doing that anyway.

Peter the only problem with this is that all these late model vehicles with hybrid drivetrains and smart alternators and all the rest of the crap quite often keep the rate of charge to the fitted battery at a bare minimum and putting additional battey capacity in parallel means that neither gets charged properly.
The only way to really get most of them to charge a second battery effectively is a DC to DC charger to charge the second battery.
The Dc to DC can handle the lack of volts from the existing vehicle system when the alternator isn't charging at full whack and from my experiments on families new vehicles the DC to DC actually nearly stops the "smart" alternator playing silly buggers when the auxilary battery needs a good top up.
Just make sure that BOTH positive and negative are run directly from the main battery to the DC to DC charger, don't use chassis for the negative and do the same with anything connected to the auxilary battery.
The hardest part is often getting the required cabling from the engine bay into the cab as most vehicles have dual layer firewalls these days so making another hole is very difficult if not impossible.

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Peter…..

……."Fit your second battery in series with the crank battery"

In "series"????? Do you want to rethink that expression?

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Peter,

I don't like that idea of coupling your auxiliary battery directly to the cranking battery at all.

Reasons being that I consider the cranking battery to be sacrosanct for the benefit of vehicle starting. The convenience of using it to supplement auxiliary loads is not sufficient to risk jeopardising the reliability of starter function. I know that people have done it without problem but there are also people who have become stranded and regretted it. A basic isolator relay is no more expensive than your proposed low-voltage cutoff but significantly more effective.

Secondly, connected in that direct manner will cause the auxiliary battery to contribute current to the cranking activity. Depending on factors such as battery specs and internal resistance this current may be in the order of 100's of Amperes and overburden the typically sized interconnecting battery cables. It is simply "not good engineering practice". Again, an isolator rely will prevent this peril.

There are established and well engineered arrangements for vehicle auxiliary circuits which are not necessarily "complicated, or expensive". Novel systems may seem very clever but are in fact usually quite dodgy and liable to incur problems at most inconvenient times. To declare that you have done it and that "it works well" may only be that Mr Murphy has not yet visited.

"Parallel" :)
I do not share your pessimism Allan.
The cable resistance determines the instantaneous load sharing.
My son used this system, with solar, and ran an Engel in the back of his FJ40 24/7 for a decade.
I am also aware of it being used successfully with the auxiliary battery being a LiFePO4.
Cheers,
Peter
OKA196 motorhome

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Then clearly Peter, it can work. But in essence it is essentially a single power source of two paralleled batteries. I would prefer a simple isolator between them.

Yes it can be looked at as a single power source except that the connecting cables can make them "un-equal" in the short term during both charging and discharging and the low voltage cut-out protects the start capability, so it has clear benefits that a single, large battery do not have when running accessories.
Cheers,
Peter
OKA196 motorhome

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Peter, I believe you said….. "Run all of the accessories from the second battery via a low voltage cut-off".
That arrangement isolates the accessories but not the batteries from each other when cranking.
Seems aberrant to me. Using 'undersized' cables to limit current delivery is not exactly good practice.
Why not simply use a traditional isolator between the batteries and be done with it?

Use whatever cables you are happy with Allan.
Cheers,
Peter
OKA196 motorhome

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Good idea.

ps.....
"Depending on factors such as battery specs and internal resistance this current may be in the order of 100's of Amperes and overburden the typically sized interconnecting battery cables"
I suggest that this is not so.
Current flow is driven by voltage difference (amongst the other things you mention) and if the 2 batteries are always connected, that difference will be always be quite low (under 3V?), even when actually cranking.
Cheers,
Peter
OKA196 motorhome

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Pete, I really am not driven to extend (win?) this exchange but I do feel a need to inculcate your electrical discernment. You may reasonably expect that I would be aware that "Current flow is driven by voltage difference", it's really not news to me, but that is not the issue that I expounded.

You said….. " if the 2 batteries are always connected, that difference will be always be quite low (under 3V?), even when actually cranking." and I totally agree with you, and in fact it is at the hub of my concern.

With the auxiliary battery voltage close to that of the cranking battery it will endeavour to deliver approximately the same current to the starter motor. Unless the interconnecting cable is of adequate capacity it may be overloaded. It just is not good engineering practice to rely on cable size to limit prospective current flow.

You seem reluctant to explain your dismissal of the conventional isolator relay? Just why is it that you reject this proven device?

The "conventional isolator" is an alternative, not the only option, but it does create greater differences between the SOCs (and voltages) of the 2 batteries and that requires heavier cable - no choice.
The alternative that I suggest for consideration keeps the 2 battery (banks ?) very close together at all times and that has benefits, IMO.
I contest that the interconnecting cableS will be at risk of overloading, at least that is my experience.
Cheers,
Peter
OKA196 motorhome

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Thanks Peter, I now see your logic in its operation. But I'm uncomfortable with it. I really prefer to keep my cranking battery inviolate. In a rare need I can always jumper from my aux battery.

Thanks everyone for your valued responses.

If I wasn't convinced to go with a power station before reading the posts from Allan and Peter I am now. If you two can't agree I have no hope. The aberrant discernment was totally inviolate of my understanding.

Although I haven't finally decided - the link below is a strong contender. No (initial) wiring required, portable and relatively small. I can get it quite a bit cheaper than the link suggests. I plan to run with it for a few weeks of travelling before deciding on whether to fit a dcdc. The fridge is new so I want to monitor its consumption needs and if a solar mat will be enough to keep the battery topped up.

https://www.bluettipower.com.au/products/ac180p-portable-power-station?_pos=10&_sid=c1979c26f&_ss=r&variant=44315225850104

If I were to get kidnapped by some obscure tribe overseas and they told me that they would honour me one final wish before they killed me, cooked and ate my svelt 100 kilo delectable body, my wish would be ................

" I would like to get a definitive answer from the 12 volt electrical guru's on ExploreOz on what would be the best way to supply power from my cars alternator and solar panels to run my fridges and other accessories while both stationery and travelling and what is the best battery for this purpose ? "

That should keep me alive for at least another six years :)


Cheers
Gazz

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LOL Gazz, ....... "6 years"?.... I think you would live forever!

Kennell:.....In point of fact, Peter and I generally agree on the fundamentals but we differ on how to achieve an outcome. I tend to stick to established engineering whilst Peter seems to like more unconventional ways. Just look at the vehicles he has owned and where he has driven them.
But most importantly, I think we both respect each other.

:) And this post comes to you from Desert Queen Baths.


Cheers,
Peter
OKA196 motorhome

A point that has been overlooked in the direct parralel sinario is the chemical imbalance. The charging requirements of the two chemistries may be near enough but the resting voltages sure aren't.
As soon as the charging potential is removed the LA battery will happily discharge the lithium down to a reasonably low SOC over time with no external loads.

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I don't think Peter was proposing wiring a lithium "Power Pack" in parallel with a lead-acid cranking battery. He did say "a completely different alternative" and I assumed he proposed a second lead-acid battery.
But I agree with you about avoiding differing chemistries.

Oh, silly me, I thought this was in some way related to the original post.

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There wasn't much that was related to the original post. LOL

No personal experience, but I am aware of someone who claims that this is practical.
I don't see why not, especially over relatively short terms (weeks+) within the normal self discharge timing of the lead acid.
Energy can not be destroyed. Where does it go?
I would like to see some actual testing before rejecting the proposal.
There is an awful lot of BS surrounding what you can not do with Lithiums that is just that. My Lithium crank battery in the OKA is coming up 2 years/25,000km. It sits at 14.3V constantly & drops to 13.5V when the engine it turned off.
Cheers,
Peter
OKA196 motorhome

Not sure what your post actually relates to Peter.
If it is the discharging of a lithium battery into a parraleled LA battery the energy simply gets turned into heat just as the small amount of current flowing through a LA battery whilst in float charge.
There is a difference in resting voltage between the different chemistries and as you are aware if there is a difference in voltage then there will be current flow.

As I said, I would like to see some proper tests. Opinions, including mine, are likely to be misleading.
Different voltages at the top end of LA and Li do not represent a significant amount of energy and the loss of energy is what needs to be measured.
In the mean time I will keep an open mind.
Cheers,
Peter
OKA196 motorhome

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I agree with you Peter.
The mis-information that surrounds batteries obscures technical specs published by the battery manufacturers.
In point of fact, I think lithiums are more accepting of charging variations than lead-acid batteries. Their only precaution is to not maintain overcharging. Constant undercharging does no harm other than reducing the amount of your stored energy. However undercharging of lead-acid cells is bad practice for battery life.
In the case of my Enerdrive lithium the manufacturer's specs are to charge at 14.2 - 14.6v and float at 13.5 - 13.8v. This would probably work acceptably from a standard alternator but may suffer if using a "smart" alternator that may run at a reduced voltage.
And I have a mantra of "Whatever works…. works".

However, in designing my house electrics for my Sprinter I chose to use an Enerdrive DC-DC charger as I had no knowledge or experience of the Sprinter's alternator behaviour. In addition, it provided me with isolation and solar input conveniently and was within my budget. This left me feeling assured of caring for a rather expensive lithium battery and has proved to be a good decision (for me).

The one thing that differs for lithium and lead-acid is the conditions for extended storage. Whilst the lead-acid is recommended to be stored in a fully charged condition a lithium is recommended to be stored at 50 - 80% of full capacity. So I bring my lithium down to 80% and isolate it but the Sprinter's OEM lead-acid battery suffers from constant parasitic discharge so is maintained on float with a tiny 1.5A mains-supplied charger which keeps all the Mercedes Magic happy.

I am restful with a system that I do not need to supervise. Automatic control was my calling and although all the data is available at the tap of a screen I am satisfied to have it constantly display the SOC only….. preset alarms will notify me if anything needs attention.

Peter,
It is an easy enough test.
I have a calcium starting battery here and also a 60ah lithium.
I will do the test if you want but please tell me your required parameters.
I would suggest fully charging them both then simply linking them together and measuring the current if any.
Would you prefer charging them individually so they are both as close to 100% SOC or as they would be in a real world situation charge them linked together to 14.6v then simply disconnecting the charger.
Please set out your preferred parameters for the test as I have all of the necessary equipment sitting right here in my home workshop.
The lithium is a relativly new 60ah and the starting battery is a 630 CCA 3 year old battery taken out of my Hilux 2 weeks ago still servicable just up to my own reasonable service life but very typical of real world conditions.

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I am not suggesting to not perform this test but I cannot consider what information it will reveal.
I am confidant that the two batteries will just sit there at the common terminal voltage and perhaps very slowly discharge due to internal current, most likely in the lead-acid battery.

What is really at stake is the long term effect on the batteries life spans and o determine that could require years of repeated charging and discharging.

However, if you feel that something may become evident then I will be educated to see the result.

My theory Allan is that the lithium chemistry having a higher nominal voltage will discharge into the LA battery till its voltage equals that of the LAs nominal voltage which theoretically will leave the lithium in a very low SOC, Which sort of defeats the purpose of having a second battery if perminantly paralleled to a LA start battery.

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Ah, I see.
Well the recommended float voltage Is the same for both lead-acid and lithium at 13.5 - 13.8 so I think they will sit there holding hands an be very happy. Then due to the typical self-discharge of a lead-acid battery the common terminal voltage will very slowly fall and little else will happen.
But I will be interested to see if your proposed test reveals otherwise.

I think that much of the BS related to Li batteries is in fact not the battery, but the BMS chosen by the seller.
Cheers,
Peter
OKA196 motorhome

Peter i agree 100%, it is up to the assembler of the battery to specify the parameters of the operating conditions as only they know the details of the individual components but that has always been the case, many porkies have been boasted about LA batteries over the years too. Look at all the sales promotions around AGMs when they were relatively unknown. And I've seen inside a few LA batteries, not always by choice, and the quality was shocking for a pretty well respected brand.
Running a pretty basic test on these to find out.

Anyone else want to put forward their expectations?
Please do it now and not after I put up the results tomorrow.

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Will there be a prize for correct prediction?
I could donate a car battery…... (dead). lol

Yes Allan, the winner will be eligible for a free burger, just have to find out where Garry L gets kidnapped and stand in line.

It is still very dear at HALF the $1400 au . A high price for a portable box, when you can have a Lithium 100 AH and a GOOD regulator for solar and a DCDC unit to charge it, when required, from the vehicle for $700 or less.
Individually the components can be positioned in any available space, whereas the Buetti BOX is not small and is half a fridge or larger.

Thanks for your input RMD.

The unit I linked to is actually 340x247x317 which is not much bigger than a shoebox. It incorporates an 1800w inverter that would cost $700. The equivalent slimline battery plus DCDC and cabling plus labour to install would end up about double the price of the Bluetti. Then there are the issues of where to put it all. Even a slimline battery and charger take up space and in a tub ute they need to be protected ie boxed.

I do a lot of semi rural volunteer work and use the ute for tools, fencing wire, horse feed etc and therefore space is important. Being portable, the Bluetti or Itechworld power packs tick boxes for me as I can remove when I don't need the fridge or charging of tool batteries etc.

I have to pay someone to do the installation as I am no sparkie and insurers take a dim view of car fires caused by amateur installations.

Before I started this thread I researched previous threads both here and elsewhere to see what experience people had with the units. It seems it is mainly younger ones who are leaning toward them and many of us who have been around a while are anti. My take is that like most things electric / electronic technology is creating alternatives that many of us have traditionally shunned.

Anyway I do appreciate the responses I have received and I watch with interest to see the outcome of the experiment detailed in the posts above. I just wish I had the faintest idea of what they are talking about !!

Kenell

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Kenell,
The experiment you refer to is only some "electrical enthusiasts" daydreaming and is not likely to provide anything of value to your considerations. I think you have evaluated the project well.

Well how to read these results.
As i predicted there is definatly a discharge into the LA battery, although not as much as I expected.
As Allan predicted it did settle down as the lithium settled to its stable voltage of 13.29 which it has not budged from since an hour and a half after comming off charge.
Initial draw was 0.85a down to 0.4a after that hour and a half then got to its lowest of 0.06a 18 hours later at 0730 thismorning, some of that drop can be attributed to the temperature drop over night down to 7 degrees, as it started to gain momentum as it started to warm up again. Now at the 24hr mark I is back up to 0.1a and voltage still 13.29. I imagine these figures would be completely different in the summer months.

So Allan you were half right, it did settle but has not stopped.
I on the other hand was expecting higher numbers.

So a rough estimation looking at the curve of the rate I estimate about 2ah give or take, has been lost in the 24 hours after comming off charge.

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Interesting experiment QC.
Actually, I did not say it would stop transferring energy. I said…."Then due to the typical self-discharge of a lead-acid battery the common terminal voltage will very slowly fall"……..
The fall, which is yet to reveal due to the short time and flat discharge of lithium, would be almost entirely due to cell internal discharge in the lead-acid battery. Give it time……
The magnitude of such discharge will of course vary with the age/condition of the battery but even a brand new lead-acid battery will exhibit some decay when just standing isolated. But you would know that. Lithium on the other hand have very low self-discharge.
Voltage variations due to temperature changes make it somewhat difficult to interpret the outcome of tests such as this but your current transfer readings tell the story. Thanks for the effort and observations.
So what does that reveal? What is the conclusion to the discussion?

I would expect it would remain as is at around 2ish ah a day until the voltage starts to drop but theoretically the lithium battery will be pretty much exhausted by then, on the up side the start battery will still be fully charged and only then will drop back to drawing only its self discharge.

I guess the conclusion is it is personal choice of weather that percentage of loss is acceptable, with regular use it would not be noticed but if parked up for a couple of weeks in a garage?

It all contributes to the overall inefficiencies of the system being designed, if your relying on minimal solar to keep your fridge going then yes you could better use the 2ah a day, if you drive every 2nd or 3rd day you won't notice it until the lithium battery only lasts 10 years and not 15 but the life of the start battery would suffer if subjected to any form of cyclic use.

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Yes QC, I appreciate your conclusions. 2Ah per day is not a lot unless the system is running at full demand.

I needed to address this sort of situation with my Sprinter. Due to social reasons it has been idle in the garage for lengthy times and I found that the OEM cranking battery was significantly discharging. All the OEM technology has a significant idle consumption. The demand starts at about 1.0A at engine shutdown and progressively decays from there. Hard to determine its final resting consumption because as soon as you open a door to inspect it all leaps to life back to the 1.0A but I figured it was about 10Ah per week when asleep.
So I made up a 'sustainer' from a Schottky diode and 1.0 Ohm resistor that provided trickle from the house lithium to the cranking battery. That worked OK at maintaining the cranker but needed to have the lithium mains-charger on all the time to avoid draining the lithium. This meant that the lithium was now being constantly maintained at 100% instead of 50-80% as recommended for long term standing. Oh dear!!!
The solution to that was to instal a small (1.5A) mains charger to keep the cranker on float yet allow the lithium to be disconnected at 80% SOC. The diode maintainer remained to ensure the cranker was kept at full SOC when camped away from the mains and the lithium was being charged by solar. Now it all worked fine.
These are the tribulations of constructing a system that accommodates my target of no supervision. I am a Design Freak, not a Control Freak.

Thanks QC.
Clearly there has been a flow from the Li to the LA, but I don't believe we can (yet) conclude that it was a loss of 2AH. It, or some % of it, may still be there.
More time may give some additional enlightenment.
Lots of other things that could now be done which would be interesting too.
Cheers,
Peter
OKA196 motorhome
(now at Tjingkulatjatjarra Pool, with full batteries including a Li crank battery that I have not seen below 13.3V ever, since it was installed.)

It's the headache of integrating hardware that was never considered by the manufacturers.
Back in my early days any constant drain of less than 0.1a was acceptable, anything over that meant something wasn't right. Usually just the clock, nothing else drew power. One amp is crazy as standard, one of the reasons they have such large batteries.
No supervision systems work well if you keep an eye on them.

Peter, both batteries were fully charged so where was the la battery going to store it, in a jerry can?

I would suggest that "fully charged" is somewhat of a rubbery concept and depends on many variable factors, including temperature that you mentioned.
Cheers,
Peter
OKA196 motorhome

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Maybe store it in a Leydon Jar? Being somewhat younger than me, you may need to look that one up.

Peter,

I think the biggest variable is your inability to accept any facts that may prove your thoughts incorrect. I guess it isn't a variable cause you have probably been like it all your life. Sorry I wasted the time trying to teach you something, it won't happen again.

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Now, having a 'real' life, I have things I need attend to, so good afternoon gentlemen.

Quite correct Allan, I'll look it up.

And so another end to" Days with our Electricians"

Stay Tuned for next episode. LOL LOL.

Cheers Axle

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Sounds good Kenell. How is the Bluetti being charged?

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It seems to be performing particularly well. Cool days are probably helping.
Reading the Bluetti specs and instructions it accepts power direct from the car's 12v systems via a "cigarette socket" at a rated 10A maximum. There seems no requirement or reason to use a Dc-DC charger unless it were to be for overcoming significant voltage drop from your battery to the Bluetti. Mind you, I have reservations of drawing a constant 10A from a cigarette socket and would recommend replacing the cigarette plug on the Bluetti with an Anderson for reliability.
The only thing you could consider is an ignition-controlled relay to suspend charging when the engine is off to prevent the Bluetti from draining your cranking battery. Solar charging could continue.

In looking at the Bluetti's specs I can determine that the battery capacity is "1152Wh" which translates to 96Ah at nominal 12 volts output. That is a reasonable battery size for your proposed loading. I expect that you are going to be satisfied.

Hi Allan,
Mine is the 180p which is 1440 wh which I understand equates to just over 100ah.
The Anderson has a relay to prevent draining.
You’re right about the cig plug. When I asked why the still instal them they told me Andersons are an Aussie thing . The cig plug has a bayonet type twist upon insertion and since the power pack and the fridge are both strapped to the same slide it SHOULD be ok. I take your point though.
Kenell