Charging the house batteries

[LeishaShannon]

Originally we had lead start batteries and used a simple bluesea 500A relay to connect/disconnect the lithium house battery from the truck when charging from alternator. We then replace the start battery with a lithium battery which made charging much easier as both batteries were the same chemistry. Recently we ditched the start battery all together as it was just dead weight - the house bank has no problem starting the truck and our electric bike batteries could be used if something went horribly wrong with the house bank.


Off Topic:

An often missed advantage of Lithium is the low peurket coefficient which makes a big difference in RV use where you have quite high loads at times. Another is the relatively stable voltage as the SoC decreases.



Heres a chart of the last 24 hours on our system showing how we've dropped from 70% to 30% SoC but the voltage has only dropped from 26.71v to 26.43v. The lifeline would have dropped a full 2 volts from so you get more usable power (W) than the equivalent lead battery.

Also neat is the low voltage sag under load - when the HWS cycled on at 22:15 the battery was supplying ~1800W @ 49% SoC yet it dropped less than a volt

Lithium is much easier than AGM to charge too. A simple single stage charger is all thats needed to CV charge to x volts (depends on manufacturer) then stop. There is no need for a long drawn out absorption charge to get the last 20% into the batteries so for RV charging from solar/alternator they're ideal as you're able to dump as much energy as you have available into them. On a sunny day with the engine running and plugged into the grid they happily gobble up 5kw+ which equates to a full charge from 0% SoC in ~1.5hours.

All that said they cost an arm and a leg upfront with no guarantee of longevity, no warranty, limited charging device support and anecdotal evidence from early adopters of ~30% capacity drop in the first 2-3 years (which may have been caused by overcharging) . But would we go back to using lead? no way

 

[Mock Tender]

pugslyyy- The more I read- the more I am liking the idea of your set-up. I am no where near my FG right now- do you have one belt or is there a way to hang a pulley to run a separate belt to the new alternator? I can't tell from your picture. The cold temp areas that we will be traveling in seem to preclude LFP's. We had great success with US Battery 12 volt multi-purpose/sweeper on our boat- but always liked the idea of AGM's.

LeishaShannon-I like your idea of eliminating the starting batteries- having two just for starting and nothing else seems like just added weight.

Mark

 

[pugslyyy]

I need to take some photos for you.

For me, the key thing is to install a multi-stage battery regulator. You can then use any externally regulated alternator that you can make fit.

This is a good article - http://www.practical-sailor.com/iss...ttery-Regulators_5616-1.html?zkPrintable=true

 

[DiploStrat]

Some Thoughts

There is no magic in having two battery banks. Two reasons for having two, separate banks might include:

-- Your camper battery is too small and you will be routinely discharging it to the point that it could not be used as a starter battery or, if connected in parallel to the starter battery, would draw down the starter battery. (In my case, for example, my camper battery bank of 600Ah, drawn down to 300Ah, would still be twice the size of my two starter batteries. Do I really need two battery banks?)

-- You are mixing two different types of batteries, specifically a starter battery (high amps/short duration) and a deep cycle battery (lower amps/longer duration). This is a very good reason to separate your two batteries. A subtext of this is to avoid interference with your vehicle's charging system.

Similarly, there is no magic in having two different alternators. The goal is not to have two physical alternators, but rather to have two different charging profiles. A charging system doesn't care whether it gets amps from one alternator, a larger alternator, or two of more alternators. So before you go to the expense of installing a second alternator and, as Pugslyyy noted, a second regulator, do some homework:

-- What is the total output of your stock alternator? Is it enough? If not, might it be less expensive to install a plug and play replacement?

-- What is the charging profile of your stock system? Does it go high enough for the batteries in your camper bank? If not, then a separate alternator/regulator or some form of secondary regulation may well be required.

-- Finally, how long are you going to run the engine? For most of us, this number is about six hours a day, barely enough to get through bulk charge. If this is your case, you might be much better advised to upgrade your solar or shore power as these are the charge sources that keep going hour after hour.

And now you can see why we are all so interested in Lithium cells.

As you can probably guess, I spent the better part of a year studying this problem. Bottom line, don't make this more complicated than it has too be. For most of us, an intelligent charge relay is all you need. And, of course, properly sized wiring.

Best wishes.

 

[Mock Tender]

Well this has all become very interesting. With an assist and pictures from Pugslyy, I thought I had my charging scenario worked out- but alas. Fuso's really are different from year to year, and what I have found is that there is absolutely no room for a second alternator or or even additional pulleys to run a belt to in my 2015, unlike the older models that appear to have vast amounts of room. Talked to three Fuso service centers and they have no clue what to do other than add a compressor for a reefer via Bracketry in Ft. Worth, TX (Fuso approved). They were no help. So I went back to Balmar, even though they said originally that the only solution to my problem would be two alternators. Well, this time around one of the techs suggested that I rebuild the stock Fuso alternator to be a P-Type Field with external regulation to the starter and via the MC-614 with harness regulator to the AGM house batteries. The MC-614 allows for complete control the alternator output and charging of the AGM house batteries. From there I would use their Digital duo that would allow up to 30 amps and the 14.4volts to go from the house batteries to the 12 volt wet cell. Balmar claiming no problems with changing battery types.

So now I just need to find a Auto-electronic or Alternator rebuild shop that doesn't say "What"? when I ask if they do P-type mods and maybe I am in the clear.

I am a little more than afraid to ask why this won't work- but why won't this work?

On a good note, my new SRW with Cooper ST/ Maxx's look great!

Mark

 

[SkiFreak]

I was looking at going down the P-Type alternator and MC-614 regulator route too, but for slightly different reasons.
I have LiFePO4 house batteries and only want to charge them at 14v, not the 14.6v that can come out of the OEM alternator.

If my recollection is correct, back in the day before they had all of these smart systems, my old mechanical voltage regulator for the alternator used to charge at approximately 13.8v. These relay based regulators were not as accurate as the electronic ones available nowadays, but there never seemed to be a problem charging the lead acid start batteries using that voltage. My understanding is that the lead acid batteries can handle a slightly higher input voltage and that this will make them charge faster, hence the reason for most current alternators/regulators charging at about 14.6v.

Over the past six months or so I have been talking with an alternator company regarding getting the parts to modify my OEM alternator. Initially they said it was all possible, but they kept putting me off for various reasons. When I last spoke with them (last month) I was told that they were too busy and were not interested in helping me at all any longer. So... now I am stuck looking for another alternator manufacturer or a different solution.

Would be very interested in hearing from anyone that might have a solution to my particular charging issue.

 

[dwh]

http://sterling-power.com/collectio...attery-to-battery-chargers-60-120a-waterproof

60a or 120a - boosts or cuts voltage to charge lead-acid or lithium.


Now this page:

http://sterling-power.com/collectio...ttery-chargers-non-waterproof-drip-proof-ip21

has a VERY interesting statement on it...

"3) Much larger model up to 3000W coming soon."

 

[pugslyyy]

I was looking at going down the P-Type alternator and MC-614 regulator route too, but for slightly different reasons.
I have LiFePO4 house batteries and only want to charge them at 14v, not the 14.6v that can come out of the OEM alternator.

If my recollection is correct, back in the day before they had all of these smart systems, my old mechanical voltage regulator for the alternator used to charge at approximately 13.8v. These relay based regulators were not as accurate as the electronic ones available nowadays, but there never seemed to be a problem charging the lead acid start batteries using that voltage. My understanding is that the lead acid batteries can handle a slightly higher input voltage and that this will make them charge faster, hence the reason for most current alternators/regulators charging at about 14.6v.

Over the past six months or so I have been talking with an alternator company regarding getting the parts to modify my OEM alternator. Initially they said it was all possible, but they kept putting me off for various reasons. When I last spoke with them (last month) I was told that they were too busy and were not interested in helping me at all any longer. So... now I am stuck looking for another alternator manufacturer or a different solution.

Would be very interested in hearing from anyone that might have a solution to my particular charging issue.

Maybe reach out to Balmar and Charles Industries and see what experience they have with charge profiles for the LiFePO4 batteries?

 

[DiploStrat]

One last Time ...

Hate to sound like a broken record, but what is the problem that you are trying to solve?

-- Alternator voltage too low?

-- Alternator output too low?

If the former, then a secondary regulator may help, if the latter, then nothing will help except replacement with a larger alternator or the addition of second alternator.

In any case, the wiring requirements are the same. If the wiring between your starter battery and your camper battery is of adequate size, then the the camper battery will take all of the charge that it can accept. Really.

OK, I will quit now.

 

[SkiFreak]

I contacted Balmar some time back. Their programmable regulator is very flexible, but the challenge is modifying the OEM alternator to be externally regulated. It either that or you need to replace the OEM alternator with a P-Type one.
To be honest... my preference is to modify as little as possible of the Fuso OEM equipment, as this can potentially lead to unforeseen issues. The systems in these newer vehicles are so tied to each other that changing one thing can have adverse issues with something else. There's a lot to be said for the old, dumb technology, especially when it comes to fault finding.

Anyway, I digress.
The Sterling DC to DC converter that dwh linked to is peaking my interest. In their blurb they say that this unit can boost voltage, but that it can also reduce voltage, depending on the charging profile that is selected.
To be honest, I would prefer to have the ability to program the bulk, absorption and float voltages myself, but sometimes you don't always get what you want.
I will follow up on these units next week, to see if I can get some more technical information about them.

The sad thing is that what I want to do is not rocket science, in my opinion. However, it would seem that very few companies make anything like what I want. That's pretty sad.

I think that one of the reasons people are slow to transition to lithium batteries is because of these sort of issues. There are some lithium "package systems" but these are significantly more expensive than putting something together yourself. There is still a huge hoodoo about lithium battery systems and everyone I speak with seems to think that they are really complicated and potentially dangerous.

I have done quite a bit of research on this subject in the past year and firmly believe that most of the problems here is people's lack of understanding of lithium batteries. I have committed to a lithium house battery system (400A), and definitely would not change back now.
I am in no way an electronics expert and would never profess to be one, because I'm not. That said, I really don't think that setting up a DIY lithium system is beyond most people's ability. However, getting the right information is the real challenge here.
It's sad, because I strongly believe that lithium batteries offer significant benefits over most other battery technologies. Things like weight, resting voltage, depth of discharge possible and number of charge cycles being just a few. Maybe one day soon the industry as a whole will embrace lithium batteries and then things will become significantly easier for the DIY lithium market. But until then, yes, it is a bit of a pain.

 

[SkiFreak]

Hate to sound like a broken record, but what is the problem that you are trying to solve?

The alternator output voltage is up to 14.6v. I only want to charge the LFP batteries at 14.0v, so I want a voltage reducer.

 

[westyss]

For what its worth, I installed a Sterling battery to battery charger a while ago, maybe three or more years?... and it is simplicity at its best! I cant argue about its efficiency or functionality with different storage mediums ( I have lead acid ) but hook up the few wires and never look at it again!

Now the few issues I have had with mine was that they will shut down at certain temps, high heat limit switch of some kind, so good ventilation as in some airflow is best.

In my application it is not meant to be used to keep the batteries charged while at camp but to be charging while driving, but if a large charger cramming amps into a lithium bank in a short time period is available from Sterling or others it seems feasible to use the engine to charge while at camp.

 

[DiploStrat]

The alternator output voltage is up to 14.6v. I only want to charge the LFP batteries at 14.0v, so I want a voltage reducer.

Was referring to the original poster. As noted by the folks at Technomadia, you may have a real issue. FWIW: A source told me that, advertising to the contrary, the Sterling B2B cannot reduce voltage, only boost it. In most cases, between lower output alternators and cable losses, this is not an issue. With modern, 14v alternators and lithium batteries, it could be a real problem. Make sure that you arrange a loan or have return privileges. Caveat emptor.

 

[pugslyyy]

The alternator output voltage is up to 14.6v. I only want to charge the LFP batteries at 14.0v, so I want a voltage reducer.

I really think the best way to get where you want is an externally regulated alternator with a "smart" regulator that you can program. Not to sound like a broken record or anything.

 

[dwh]

A source told me that, advertising to the contrary, the Sterling B2B cannot reduce voltage, only boost it.

Probably referring to an older unit. This is a new unit that also cooperates with alternator regenerative braking systems. Also programmable and...according to that page I linked:

"Voltage Reduction, SOME MODERN ALTERNATORS COME PRE SET WITH A VERY HIGH STANDARD VOLTAGE IE ABOUT 14.8 - 15 VOLTS, this voltage is fatal to some battery types. Up until now, most Sterling Power products have been all about increasing voltage to boost charge the batteries, however some alternators now come standard with very high output voltages, on the surface this may seem like a good idea but the voltages on some alternators are way above the recommended voltages for the likes of AHM, GEL, and Lithium batteries. Voltages of 14.8-15V are not uncommon, in this case the voltage must actually be reduced not increased, this model has the ability to boost or drop the alternator voltages depending on the battery type selection and the battery charging requirements, ie you can feed 15 volts into this or 13.8V and you will still get 14.4 (IF THAT IS YOUR SELECTED / REQUIRED SETTING) ." [emphasis added - dwh]