mppt vs pwm

[pianotuna]

Hi,

A nice little video comparing mppt vs pwm with the batteries in bulk mode.

mppt vs pwm

[jrnymn7]

$155 + $40 shipping = $195 - $175 = $20 extra for a completely user adjustable unit.

[Bedlam]

Shipping is a little steep on that one above. This one is $175 with shipping:

http://www.ebay.com/itm/231019238595?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

* I just found one of the above 30A controllers Amazon for an even better price. These are some interesting options...

[jrnymn7]

http://www.ebay.ca/itm/New-Tracer10A-20A-30A-40A-MPPT-solar-charge-controller-regulator-solar-charge...

[CA_Traveler]

Sounds like a plan. Keep on top of Craigs List and you might find a bargin.

[Bedlam]

Can you point me to some cheaper model controller that would allow these 24V panels while keeping a 12V battery bank? A 60A Tristar just sold on eBay for under $500 but I'm not ready for that kind of financial commitment. I'll be able to draw off half a bank with the inverter for testing till I find something. I know this not ideal, but I can bank switch until I get this right.

[mena661]

You can get inexpensive DC to DC converters. I think 2oldman is running a 24V battery bank with a Victron DC DC converter for the 12V stuff.

[BFL13]

You can't use the fake MPPT to go from 24 to 12v, it has no buck converter. The ones that say 12/24 can run a 24 panel but only to a 24 battery.

You can run 24v batteries on the trailer with a 24v inverter to get 120v from the inverter to the camper via a 120v cord. Now you need some 12v for the camper. Use the 12v batteries there and a charger powered by the 120v from the trailer.

Some of us tested the 12v inverter draw on a 12v battery bank to run the 120v converter in the trailer with no batteries hooked up. About 6 DC amps. Same as a television.

Experiment was for a "remote power supply" concept to run an RV with no batteries in the RV. Like those MHs that tow a cargo trailer done up with batteries, solar panels, controller and inverter, and a Honda gen, and whatever else. 🙂

[Bedlam]

12 of the batteries will actually be going in to side boxes of my truck (Ram 5500) and be charged primarily by the dual alternators. The other 12 will be in an enclosed trailer with four 136W 24VDC panels keeping them charged. There will be an interconnect between the camper on the truck to the trailer, but I have not decided on an AC or DC connection. The batteries in the truck will be a parallel 12VDC connection to the camper.

Going to a higher voltage battery bank in the trailer will raise equipment cost for inversion to AC or stepping down voltage to 12VDC for use within the camper. I understand there is greater loss at lower voltage with higher amperage plus the requirement to larger cables, but am looking for an economic solution. If I can parallel two 24VDC panels into the cheap 30A MPPT controller I referenced to feed a parallel 12VDC battery bank, I think this will be a good start. I have a 2KW continuous use MSW inverter on hand for load testing. Once this system is up, I can continue scouring the web for upgrades without having too much invested in the initial install. Naturally as I find deals on more capable units, I may reconfigure the battery pack (for example a true sine wave inverter that accepts a higher input voltage). The idea of multiple charging sources being able to be used for all the batteries may limit my ability to go with higher voltage bank and not increase my cost beyond my budget.

The goal is to be able to run high wattage AC items for a minimum of a half hour and to have AC available to low wattage items (TV, chargers, mobile hotspot) for a minimum of six hours.

[CA_Traveler]

Bedlam,

What is your power requirements and how/when do you plan to get there? 24 batteries is a long way from the cheap controllers you've posted as well as your panel postings. Aside from being free do you really have a plan/need to use all that power and weight? Or did I miss something?

[CA_Traveler]

Bedlam wrote:

pianotuna wrote:
I agree 24 or 48 volts would be the route to follow for the battery bank.

Method 3 on the smart gauge site for the wiring. I.E. equal length cables from all jars to a buss. correctly interconnecting multiple twelve volt batteries

With 24 batteries that works out to six "strings" of four jars, assuming each jar is 12 volts. Voltage at the buss is 48.

I'm still trying to find a good price on better controller, but am trying out cheap ones while I wait for a deal.

http://www.ebay.com/itm/10A-20A-30A-12V-24V-Auto-Switch-MPPT-Solar-Panel-Regulator-Charge-Controller...

For now he's looking at 24V controllers. But 24 or 48 I'd go vertical with that many batteries. For 24V then 2x4 battery array 3 high.

[BFL13]

Those "RJ Specials" are of course not MPPT as claimed. No buck converter. But they do a decent job as regular Series PWM.

[Bedlam]

pianotuna wrote:
I agree 24 or 48 volts would be the route to follow for the battery bank.

Method 3 on the smart gauge site for the wiring. I.E. equal length cables from all jars to a buss. correctly interconnecting multiple twelve volt batteries

With 24 batteries that works out to six "strings" of four jars, assuming each jar is 12 volts. Voltage at the buss is 48.

I'm still trying to find a good price on better controller, but am trying out cheap ones while I wait for a deal.

http://www.ebay.com/itm/10A-20A-30A-12V-24V-Auto-Switch-MPPT-Solar-Panel-Regulator-Charge-Controller...

[Salvo]

You shouldn't have any more questions after reading that thesis.

That thesis is way more interesting than mine was on analog multipliers.

jrnymn7 wrote:


Cloud Effect

[BFL13]

Ductape wrote:

JiminDenver wrote:
That is because you are only applying a dollar symbol and not looking for the best tool for the job. The only time dollars should be a consideration is if you look at it and either would fill the need. That's when you look at the advantages and cost of each.

Exactly. If you are looking for maximum performance from a limited roof space for instance!

That can lead to having a number of smaller 12v panels instead of a few bigger 24v panels. But it does not tell you whether to put the 12s as 24 and use MPPT or leave them as 12 and use either PWM or MPPT.