Design Advice: Van Electrical System

[WanderingCanuck]

Pro Tip to get more / better responses:

Best to ask a small number of questions on just one topic at a time, as specific as possible, relevant background details all in one post, don't assume we remember stuff from past (huge) posts (take too long).

TL;DR make things as easy as possible for helpers to help

Thanks, John. Though I'm new to this forum, I'm "old hat" on many others. Before signing up it seemed like there were lots of helpful and patient people here, and I hope that remains the case.

As much as I try to stay on topic, there are so many things that interrelate while trying to consider the big picture.

That said, aside from being told that what I'm trying to do is difficult (my interpretation so far), no one has given me anything really concrete - which is what I'm really looking for. If it wasn't difficult, I wouldn't be asking for advice and assistance from those of you who clearly have more knowledge and experience than I do.

 

[jonyjoe303]

lifepo4 is the way to go, the more amp hours the better. They will charge quickly with your alternator, unlike agm they accept maximum amps until the bms decides to cutoff the current (usually somewhere around 90 percent/higher if the battery is in perfect balance). I think most 100 ah lifepo4 can charge/discharge at up to 100 amps, so your minimal driving will at least keep them charged. No need to fully charge them every time. Maybe your oem alternator will be plenty to charge it and you won't need a higher output unit.

Even though most lifepo4 have built in bms, as long as you monitor the voltage you should be ok (fully charge 14.6,discharge 11.2), you can always add an over-voltage relay that can cutoff charging when the battery reaches a certain voltage like I have on my lifepo4. Make sure you get a coulomb meter, that's the only way you can keep track on a lifepo4 status, lifepo4 always reads 13.1 volts whether its 20 percent or 80 percent full. The coulomb meter counts the amps going in/out of the battery and gives you a realtime status of its present capacity.

Also you get more usable amps at a lower weight, my 110ah  lifepo4 weighs in at a little over 30 pounds, a 100 ah agm (50 ah usable) would be in the 70 pound range. I have a small 28 ah agm (14 ah usable amps) that weighs (25 pounds) almost as much as my lifepo4. Weight savings are really impressive.

 

[John61CT]

> no one has given me anything really concrete - which is what I'm really looking for.

Well go back to "the novels" and extract concisely, then post as I said, one at a time.

No need to start new threads for each topic, but may well garner more responses, many readers skip by old ones if it made their eyes glaze over the first time.

Think short attention spans, hot takes on keyword snippets way to go these days.

 

[tx2sturgis]

You really think solar would do much of anything where I am?  Certainly more in the summer, but in the winter?

If you have tiltable or portable panels that can gather sunlight at the lower sun angle during the winter, and assuming clear skies for at least a few hours a day, then yes, you will be able to harvest enough power to recharge a laptop, and run some small items like LED lights. 

Then you can attack the heat and cooking problems with good old fashioned fossil fuels. 

BTW....even the Propex, Wesbasto, Espar units NEED a good reliable source of DC from a battery when running, as in all night, or they WILL shut down. 

Another good reason to have some DC input to the batteries via solar. 

(closed circuit to pnolans) Yep!  

 

[WanderingCanuck]

Well go back to "the novels" and extract concisely, then post as I said, one at a time.

True, there was a lot in the first post. I'll distill it down without trying to prove that I've already done some research.

--

I'll need between 75Ah and 145Ah daily. What system can be made to work with vehicle alternator charging only?

...but you already need to know some other things to answer that question:
- 1-2 hours driving at highway speed per day
- Additional HO alternator possible
- Battery compartment temperature will be controlled

 

[John61CT]

> I'll need between 75Ah and 145Ah daily. What system can be made to work with vehicle alternator charging only?

If lead, the bank will be murdered early from PSOC abuse, no dino juice source is practical to get to 100%, takes at least 4 hours and last 2/3rds timewise is very low amps. Higher amps doesn't matter as much as a good external VR like Balmar MC-614.

LFP at 5-7x the price per AH is the real solution.

Or Firefly Oasis, at $500 per 100AH, severely constrained supplies ATM, maybe 3-6 months backordered.

You will need to overnight on shore power at least monthly to maintain them properly.

 

[John61CT]

Add just a bit of solar, do your driving in the morning, then you can keep a less expensive bank alive much longer.

 

[tx2sturgis]

I'll need between 75Ah and 145Ah daily.  What system can be made to work with vehicle alternator charging only?

...but you already need to know some other things to answer that question:
- 1-2 hours driving at highway speed per day
- Additional HO alternator possible
- Battery compartment temperature will be controlled

For the money you'd spend on a high output alternator or second alternator, I would apply that money on a hitch rack and an electric/remote start genset and let that thing run while your driving down the highway, and stopped in transit at meal stops, whatever. This is a solution that many expeditors and pilot cars use. I have also done it (with pull-start generators).

The full available continuous power of the genset can be applied to a high capacity automatic battery charger. Many of these are inverter style, and very quiet. Notice I did NOT say cheap.

 

[WanderingCanuck]

For the money you'd spend on a high output alternator or second alternator, I would apply that money on a hitch rack and an electric/remote start genset and let that thing run while your driving down the highway, and stopped in transit at meal stops, whatever. This is a solution that many expeditors and pilot cars use. I have also done it (with pull-start generators).

The full available continuous power of the genset can be applied to a high capacity automatic battery charger. Many of these are inverter style, and very quiet. Notice I did NOT say cheap.

For charging an LFP battery at 2C, a 100Ah battery would take about 200A for 30 minutes (or 100A for 1 hour if you suppose 2C is too much), if I have the math and assumptions right. There are certainly alternators available in this output range. So I'm stuck on why the vehicle alternator isn't a good choice here. I understand there are other components to the system, but are there no voltage regulators that work in this range? Why not run an inverter right off the alternator (with maybe a lead acid battery buffer) and the A/C high capacity charger you suggest?

 

[tx2sturgis]

Why not run an inverter right off the alternator (with maybe a lead acid battery buffer) and the A/C high capacity charger you suggest?

I can't say that the above won't work, but my solution means you could run the quiet generator at almost any time...parked, camping, boondocking, whatever. 

Batteries get low at 3 am? Start the generator.

Idling a vehicle engine means accelerated wear, fuel waste, possible issues with oil use and condensation in the oil, and most high output alternators require high rpm idle to put out high amperage.

 

[WanderingCanuck]

Idling a vehicle engine means accelerated wear, fuel waste, possible issues with oil use and condensation in the oil, and most high output alternators require high rpm idle to put out high amperage.

At this point, I'm not talking about idling. It would be in the course of regular travel mostly at highway speed, not just running the engine to charge a battery bank.

 

[John61CT]

> For charging an LFP battery at 2C, a 100Ah battery would take about 200A for 30 minutes (or 100A for 1 hour if you suppose 2C is too much), if I have the math and assumptions right. There are certainly alternators available in this output range. So I'm stuck on why the vehicle alternator isn't a good choice here.

Yes, LFP changes everything if you're willing to spend thousands.


> I understand there are other components to the system, but are there no voltage regulators that work in this range?

MC-614, fully adjustable setpoints.

> Why not run an inverter right off the alternator (with maybe a lead acid battery buffer) and the A/C high capacity charger you suggest?

Very expensive wasteful IMO ridiculous.

Alt output, or **any** charge source can be moderated by B2B much more reliably.

 

[WanderingCanuck]

Yes, LFP changes everything if you're willing to spend thousands.

I'll have to see just how many thousands need to be spent, but if it improves the big picture I'm willing to go that route.

MC-614, fully adjustable setpoints.

Thanks, I'll be checking that one out for sure.

 

[John61CT]

See if Bruce Schwab @ Ocean Planet might be willing to sell you a small system, lots less risky with an integrated BMS, and save DIY reinventing the wheel.

Otherwise look for CALB or Winston bare cells, each 4s string = 12V, no more than two strings in parallel, so 2s4p.

Sometimes complete 12V kits on eBay, but usually shipped direct from overseas, bit risky that.

Or look at the "12V drop-ins" like BattleBorn, but I suspect their longevity not as good, and can't be the only target batt on the charge buss in case their internal BMS suddenly isoltates.

 

[WanderingCanuck]

Any suggestions for Canadian LiFePO4 distrubutors?

I've been searching online and these things aren't that easy to find.  I must be looking in the wrong places because even eBay doesn't seem to be a great source.

 

[John61CT]

No, it's very common for people to import directly from China, or via Russia.

The DIY EV forums may be worth posting to, sometimes people do group buys.

I assume you've checked these guys:

https://www.google.com/search?q=calb+180AH

 

[Surly Biker]

Any suggestions for Canadian LiFePO4 distrubutors?

I've been searching online and these things aren't that easy to find.  I must be looking in the wrong places because even eBay doesn't seem to be a great source.

Victron is a Dutch company with worldwide distribution. I put together a system with their LFP batteries, BMS, solar charger, and inverters.  Pieces all work together pretty seamlessly. Check their website.

 

[Trebor English]

Trebor, what brand and size battery in AH do you use as your one battery? There was a guy on the old yahoo group that did that and even stored the battery inside the van (not in engine compartment).

Go to www.samsclub.com and search for "DCC 24 battery" for the details.  I determined that a group size 24 would fit so I got the one with the most pounds, the most amp hours, and the least cold cranking amps.  The batteries might be all the same with the only difference being the sticker.  The one I got is 75 amp hours.   Since it uses 20 to 30 ml of water per cell per month it seems not to have calcium in the plates alloy so it might really be deep cycle.   It is not maintenance free.

 

[DLTooley]

Lithium for solar is just not ready for prime time. There is a lot of demand for LiFePo4 batteries and they aren't getting to us at a decent price. Yet.

A well designed system will have some redundancy in it, a small solar panel for that last little bit of charge does make sense. It would also provide some learning curve experience as well, something you may wish to consider as you design your overall system. They extra money spent for a professional with a large system might well be worth it.

 

[WanderingCanuck]

Lithium for solar is just not ready for prime time. There is a lot of demand for LiFePo4 batteries and they aren't getting to us at a decent price. Yet.

Is the price the main reason you say they aren't ready yet, or is there another reason? I've never been known as an early adopter for technology. The biggest (only?) reason why I'm favouring these in my design is for the ability to accept a charge very quickly. The way I see using them, as I've mentioned above, is by high current vehicle alternator charging for a short period of time (1-2 hours, maybe) each day. This can't be done with current lead-acid battery technology and thus I'd never reach full charge - a sure way to kill a lead-acid battery quickly. So far my research is showing that only LiFePo4 batteries withstand this sort of charging regime.

As for solar, I'm not against it. I'm just skeptical there will be much benefit at my latitude, especially in the winter. I might produce more current with a stationary-bike powered generator If I leave it out initially, I'll certainly leave a place for it in future design evolution.