Solar charging controller for truck battery: PWM vs MPPT?

[Strata]

Looking for some playa wisdom on our current conundrum:

Our 2004 Nissan Titan was kept in storage with a small solar battery charging setup for about a year and 4 months. All was well, it would start right up when we visited it. At some point the panel failed, and our battery went flat-- we know the panel failed because we have measured its output with a voltmeter at high noon and it sucks.

My husband wants to replace the system with something bigger and better. We want to use a bigger panel and mount it in the cargo basket on top of the truck. With a bigger panel we need a bigger charge controller, and here's where the confusion sets in. There are a couple of different types of controllers you can get, pulse wave modulation type and MPPT type. There's a wide range in price differences, and we're not sure which is better for what kinds of applications.

Any lore appreciated. The interwebz are not being majorly helpful here, at least not to someone like myself. There are lots of MPPT vs PWM links that talk about pulling extra amperage and balancing charge vs load on a fixed installation house-type system, but is that *useful* for just charging one little truck battery? It's a $50 - $100 price difference, so is it worth it?

thanks!
Strata

[ygmir]

Looking for some playa wisdom on our current conundrum:

Our 2004 Nissan Titan was kept in storage with a small solar battery charging setup for about a year and 4 months. All was well, it would start right up when we visited it. At some point the panel failed, and our battery went flat-- we know the panel failed because we have measured its output with a voltmeter at high noon and it sucks.

My husband wants to replace the system with something bigger and better. We want to use a bigger panel and mount it in the cargo basket on top of the truck. With a bigger panel we need a bigger charge controller, and here's where the confusion sets in. There are a couple of different types of controllers you can get, pulse wave modulation type and MPPT type. There's a wide range in price differences, and we're not sure which is better for what kinds of applications.

Any lore appreciated. The interwebz are not being majorly helpful here, at least not to someone like myself. There are lots of MPPT vs PWM links that talk about pulling extra amperage and balancing charge vs load on a fixed installation house-type system, but is that *useful* for just charging one little truck battery? It's a $50 - $100 price difference, so is it worth it?

thanks!
Strata

I've ended up using MPPT controllers on my last two RV long term and camp use systems. They seem to take the best advantage of changing sun angles for more efficient use of panels. PWM are good, and fine for what you are doing though, too, and I'm told PWM are slightly easier on the battery, in terms of lifespan. I don't know this for fact though, just anecdotal. I like MPPT, in the end.
Depending on the size of your panel, and power needs, MPPT are around 100 dollars, some far less, and PWM under 50, for what has, so far, worked just fine for me.
My last one is a Renogy 20 amp mppt. I liked the features, so am trying it.

[Captain Goddammit]

The most economical, reliable and sure-fire method, if the truck sits that long, is to simply bring a charged battery and drop it in.
That way you know the battery IS going to turn the truck over. No worrying whether your system failed a year later.
I own several vehicles that sit for long periods and I take the batteries home and keep them up with a trickle charger in the garage.

[XPTom]

I'm ready to click on ordering the Renogy MPPT myself.... anybody tell me why I shouldn't?

My 100 watt panel(folding Renogy) via a PWM controller to a 75AH battery could keep up with my 60+ watt Whytner fridge in the BRC temps during the day, but not bank enough in the battery to make it thru the night.

First upgrade planned is MPPT ..... PWM simply takes the 17.9V 5.6 panel amps and cuts it down to 13.9/.5.6..... 20+ watts gone......

Second.... move the charge controller down next to the battery. I unwittingly bought a panel with integral PWM controller and the 13.9V leaving the roof was low 13's after the long trips thru the wires... more loss on top of PWM loss and the charging curve slowed to a crawl as battery voltage rose to upper 12's .

Third.... I will add more panel.... but I figure "less" more if I use the MPPT. Daisy chaining another 50W to my existing 100W is in the cost vs output neighborhood of adding 100W to my existing controller.

Last will be a bigger battery. A fully charged 75AH works well for me on first day. Wet cells can take 75% charge in 6-7 hours, but much longer to top off.... solar day limits apply.... It is quicker to get a 100 Amp Hour battery up to 75% charge than a 75AH battery up to 100% charge.

[Token]

I’ll give a +1 on Renogy as a brand in general.

Have used them for ~ 5 years on the ranch for odds-and-ends spot power ... electric gates, electric fences, lighting, power to a remote shed etc.

Zero failures, decent price point.

I’ve been lucky to know a few folks that do cellular tower service so I got some real nice 155ah batteries from them on the cheap. Heavy as an anvil tho.

They have to swap them out after a year regardless of battery state, so good batteries.

For TTITD, I like multiples of smaller batteries over the big badass battery. Easier to handle, has redundancy, can add over time incrementally.

Any controller you get, make sure it can grow with your needs. 12, 24, 48V as operating modes and enough juice to go 200, 400, 800W in panels.

Flexibility helps.

[Popeye]

Second.... move the charge controller down next to the battery. I unwittingly bought a panel with integral PWM controller and the 13.9V leaving the roof was low 13's after the long trips thru the wires... more loss on top of PWM loss and the charging curve slowed to a crawl as battery voltage rose to upper 12's .

Or you could increase the wire size between the controller and the battery.

[XPTom]

[quote="Popeye
Or you could increase the wire size between the controller and the battery.[/quote]

True, but replacing the "solar ready" factory wiring is easier said than done. I just bypassed it last year and went from panel to the battery with jumpers.