Best way to get to 100AH's ?

[Matlock]

I have a small working mobile solar build about 2 yrs old. 400 watt solar, Kid MPPT into two 6V flooded 215AH battery's in series. I use a PD 9245 120V Charger. No alternator charging. Just sun and the occasional shore power once every week / week and a half at 14.4V with the PD 9245 and the Wizard. I typically consume abt 45 AH or 540 Wh per day (Just rounding off here). My 400 watt panels recharge the 25% battery consumption easily. I do have a Genny that can be used if I can't get to shore power but not needed so far.

I want to increase the available AH's. I've been reading up on LifePo4 and AGM. My other option is to just do an expansion of what I have. Expansion might be the easiest and cheapest.

To that end, I'm thinking of building a system that is capable of providing 100AH's daily, out of (four) 6V 220AH flooded batteries and when I know it will be cloudy/overcast tomorrow I'll reduce usage the night before to around 50AH's.

100 AH X12V is 1200 Wh , and calculating 3 peak solar hours a day in the mid-west to south mid-west.
If I go this route I'll need more panels, another MPPT controller and four new 6V flooded batteries.

I know I can draw down my current system to 50% to get the 100AH's but I'll have problems getting them charged tomorrow without using the Genny for the first couple hours. Not real crazy about that.

Any suggestions are welcome.

Richard

 

[John61CT]

No matter how large your bank

you have to put back more than what you take out each day

Solve that before expanding storage.

Easiest is to run the genny before panels kick in while the bank accepts high amps.

If you use dino juice to get the bank to 80% - or 70% or 85% depending on the season, temps, weather - then the solar is much more likely to get to 100% Full as per endAmps.

And the bank will last much longer.

Best to have one big bank rather than separate ones.

 

[highdesertranger]

oh boy here we go. I would like to remind everybody to answer what you would do in this situation and not to get in a spitting match going back and forth with stuff that has nothing to do with Matlock's question. please stay on topic. carry on. highdesertranger

 

[jimindenver]

You already have the battery capacity in those 6 volts, no reason to waste the advantage they offer. 400 watts of flat panels is going to be hard pressed to cover it in the winter. So the first option is to tilt that 400 watts. The second is to add to the system and you could over panel the Kidd to get more out of the shoulder times or even get closer to the controllers capacity at peak. The winter days are not only shorter but the low sun can cut peak production by 50% on a flat panel. So there is a good deal of buffer before you actually over panel in the winter.

You could add panel and add a second controller or replace the Kidd to cover them all. It might be easiest to just add a portable to give you the added production when you need it. 200 watts tilted and tracking is as good as another 400 watts mounted flat up top.

 

[tx2sturgis]

I want to increase the available AH's.

Is that because your power needs have increased? Or because they are the same but you want more ah during winter/cloudy periods?

If your power needs have increased, you probably need more panels, or tilt the ones you have.

But if you simply want a longer lasting reserve capacity, and are not actually using more power, then adding another set of batteries will get that done...and won't get as close to the rule-of-thumb 50% level. 

Then if you do have lower power input, you can make up for it with the generator.

Of course you can always do both, or all three, budget permitting.

 

[tx2sturgis]

oh boy here we go.  I would like to remind everybody to answer what you would do in this situation and not to get in a spitting match going back and forth with stuff that has nothing to do with Matlock's question.  please stay on topic.  carry on. 

Oh you know us only too well.

Wait, was that off-topic? I think it was.

 

[Weight]

Increasing battery bank is a good thing. As you are familiar with flooded batteries, you will be well served with a 460 amp hour bank of GC2's. Remember, the bank is only as good as its oldest battery. Depending on your battery use, you may always have to run the generator for a bit. If you have room for more panels, or exchange for more efficient panels, that may still not supply enough return to avoid using the generator. my math may not be exact but here it is. It is just to give some understanding of battery charge. AH is not the measurement of use from a battery. It only means the battery was tested for 20 hours at a constant current. Different, more or less, currents cause a different, more or less, length of discharge hours, or minutes. Draw steady 10 amps from a 200 ah bank. Then you have depleted your bank by half in 10 hours. If you draw a steady 100 amps, you will deplete your battery by half in not 1 hour, but maybe in <50 minutes. To return that power, your solar producing 15 amps needs 8 plus hours, estimated. If you get 15 amps for the full 8 hours.

 

[jonyjoe303]

You mention lifepo4 and agm. Lifepo4 will be a lighter alternative. I googled 6 volt 220 lead acid batteries, and they weigh about 70 pounds and the lowest cost was like 130. 4 of them will be almost 280 pounds of batteries for 220 ah of usable AH's.  
The 12 volt 102 ah agm I had was only 70 pounds, 4 of those would be 280 pounds for 204 ah of usable ah's. I also have 2 x 110 ah lifepo4's, total weight of both is 60 pounds and usable ah is almost the full 220 ah's. 

Lifepo4 if your willing to build your own, you can build a 60 ah (comparable) to a 120 ah lead acid for about 150 dollars. It does requires a tab welder ( about 100 dollars) and some soldering, and hotglue gun. I built 2 x 110 ah lifepo4 and I built them inside my van so its not something that requires a workshop or a large inverter (my 200 watt inverter was adequate). The price of lifepo4 if you build your own is comparable if not cheaper than lead acid, I can build a 220 ah lifepo4 battery pack for about 400 dollars. To charge with a generator you would need a higher price BMS (40 dollars and up) that can handle the higher charge rate, I use a 6 dollar 30 amp bms on mine for my 240 watt solar panel.

The reason I bring up the weight of batteries is recently I couldnt smog my van because it was too heavy for the dyno, since then I have been removing all the excess weight that I can, all the lead acids I had, had to go. I'm 100 percent converted to the lighter lifepo4. If I needed extra ah's, I just build another lifepo4, after you build one, buildng another one is childs play. Thats why I mention to build a smaller 60 ah lifepo4 before you move to the larger ah's, you learn the skills required without spending too much money and see if its something you can do. 

To me the only difference between lead acid and lifepo4 is weight, they both will run my equipment and charge with the equipment I currently have. If the only way I could get lifepo4 was to spend 1000 dollars, I would stick with lead acid.

 

[John61CT]

I would **not** mess with DIY LFP pack assembly, secondhand EV stuff, welding pouches or cylinders etc.

Lots of advantages besides weight, doing it right with bare cell 3.2V prismatics, can even be cheaper over decades, but up-front investment is risky, 5-7 times more expensive than lead.

Plus the specialized charging and protective gear, can cost more than the cells.

 

[Matlock]

jimindenver
You could add panel and add a second controller or replace the Kidd to cover them all. It might be easiest to just add a portable to give you the added production when you need it. 200 watts tilted and tracking is as good as another 400 watts mounted flat up top.

As is, my Kidd is good up to 500 panel watts, full sun. So, by adding another 200 watts --tracking, to my existing 400w Renogy flat panels I'd still be OK with existing Kidd. I agree, maybe a problem in the summer sun or unplug a panel....

If I went with a new controller.... for all panels and... *What if I wanted to go to say a pair of Fullriver (or equivalent)  6V 250Ah AGM's in a year or maybe two and scrap my flooded Batts. What controller change could I make now that would work equally well with today's flooded and tomorrows AGM's?
(Future... with AGM's I'm thinking about a possible microwave 1000w/ 20 min/day from battery/inverter with an on/off switch).

tx2sturgis
If your power needs have increased, you probably need more panels, or tilt the ones you have.

I have 50% roof space available and a couple bucks burning a hole. And I have too often observed the Trimetric at 12.4 by 9:00 PM. Still have to run the TF 51 and my fan overnight. I need more panels for sure so battery/controller/inverter for future, it may be worth buying some stuff today and the balance later. If I don't have to buy too many redundant pcs that have to be replaced later.

Weight
Depending on your battery use, you may always have to run the generator for a bit.

I will be increasing my battery use but I'm trying to avoid needing the genny on a regular basis. And maybe I can't with flooded batts. The main problem as you know is that first 85% of the charge every day. Since I usually drive for a couple-three hours every day I may revert to battery charging from my 145A alternator rather than the Genny. Don't know but don't really want the truck electric's involved if I can avoid it.

 

[John61CT]

If you're driving that much **in the morning** then it's well worth making use of alt charging.

A high-amp DC-DC charger can let you do that well without modifying your vehicle electric at all.

But expensive, there are cheaper ways, but then you need to watch alt temps.

Slow acceptance FLA actually helps avoid such problems, high-CAR chemistries means faster charging, but more likely mods needed.

 

[Matlock]

To me the only difference between lead acid and lifepo4 is weight, they both will run my equipment and charge with the equipment I currently have. If the only way I could get lifepo4 was to spend 1000 dollars, I would stick with lead acid.

LifePo4 still lacks in history. Price/durability/service are still in question for many applications. I'd love a couple but not ready to pay for them. And yes, battery weight is still a consideration and then there's the biggie...how am I going to replace what I use every day, regardless of the battery I choose.

 

[Matlock]

If you're driving that much **in the morning** then it's well worth making use of alt charging.

A high-amp DC-DC charger can let you do that well without modifying your vehicle electric at all.

Any links to the DC-DC charger?

 

[MrAlvinDude]

Any links to the DC-DC charger?

This one might be worth a look 
https://www.amazon.com/CTEK-56-677-Automatic-Battery-Charger/dp/B005LBCVL4

 

[John61CT]

Sterling Power's BB line "batt to batt" is the best, future-proof if you go to LFP in future with full adjustability user custom setpoint profiles.

I think 120A is currently the biggest, but the owner / engineer wrote in an email a 180A version coming RSN.

Alan at Bay-marine is a good supplier in the US, Maine Sail can probably get them in too if you want to support his work for the community. PKSYS has good pricing, but not as good support as the first two.

 

[John61CT]

CTEK makes great gear, but that DCDC unit is limited to only 20A.

Adding the SmartPass boosts to 80A, but IMO a kludgey workaround.

The included solar controller is really for just maintaining a bank stored outdoors, not cycling a big House bank.

Post a specific new thread for details if you consider going that way.

 

[John61CT]

The only other good DCDC chargers are from Australia, not supported here, expensive, and like the CTEK, not adjustable setpoints.

 

[John61CT]

Nice thing about the Sterling line is with a bank that needs / deserves coddling, that can become the *only* charge source for that bank.

Then any old dumb non-adjustable charge source can feed it, cheap starter batt buffers the current from upstream, B2B gives the big House bank exactly what it needs.

The Sterling can easily move with the bank to another vehicle, trailer, off-grid cabin, whatever.

No need to buy any other expensive charge sources, any 12V output will do.

https://sterling-power.com/collections/all/battery-to-battery-charger

Full data sheets and manual PDFs available for both these and the CTEK+SmartPass.

Echo Charger is so basic no manual needed. Yandina also a good choice in that niche.

 

[John61CT]

If the Sterling's too pricey for you, then here's another way to go.

Put all your charge sources, including Alt/VR, directly to the big House bank, and a very low-amp (cheap) combiner like Xantrex Echo Charger, or that CTEK unit, will have no problem keeping the Starter well charged from House.

But you then need to make sure your House demand isn't overloading what your alternator can handle.

Again, not usually a problem with FLA, only higher CAR chemistries.

 

[John61CT]

If just keeping Alt output to Starter batt, no DCDC charger, then this is the best by far out of all the many vanilla ACR/VSRs on the market.

https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

Very high ampacity, super robust, will last decades, can handle self-jumpstarting from House if needed.

Personally I would avoid automotive / stereo type gear for this category.

But some people are happy with a $50 ignition-switched solenoid, fine long as you don't need both circuits charged from either side, Starter only used for cranking when long-term boondocking.