Random questions/musings - new batteries, genny, charger...

[seraphim]

The TC came with one 75AH battery. The twin alternators on the truck charge it well, although there is no isolator: if I leave cable connected between the truck and TC, then disconnect the house battery, the battery meter still shows full as it draws power from the truck batteries (diesel has two batters and one 145 amp and one 165 amp alternator). The. House battery is good for overnight; generally we just run the fridge on propane. We borrowed an i2000eu generator, and it appears to take 3+ hours to recharge the house battery from 50%. (120 volts/13.3 amps from the genny) . The meter on the TC appears to suck in terms of accuracy - just uses idiot lights.

What I want do:

Replace the house battery with two or three AGMs, totaling about 300ah to 400ah approximately. Add a decent meter to indicate battery level, and perhaps charging progress. Add a cutoff switch for the house batteries. Not too twigged about the lack of isolator - I just unplug the capable between the truck and camper when I dry camp. I also wonder if the TCs charging system would need to be upgraded or changed for the switch to AGMs and/or the higher capacity; or will the existing setup be sufficient for the batteries to be charged from shore power or genny.


BIL also has a lightly used i2000 to sell me for $600. He had just bought it new, then his new rig came with a built in genny. For another $1k I can buy a companion genny for a total of 4000 (theoretical) watts. Easier to carry the two smaller units, and the flexibility of only carrying one if necessary.

Any knowledgeable folk out there have thoughts or concerns? Seems it should not be a difficult modification, but I'm not sure of the wiring setup for a new meter, nor how good the OEM battery chargers are - are they quality 3 stage, or POS units.

Considering adding about 400 watts of solar panels later.

Any opinions/education would be appreciated. I have basic theory down, but that's far from practical application experience lol.

[seraphim]

Thanks. I'll check into the Rogue

[pianotuna]

Hi Seraphim,

Yes, Mppt is a dc to dc converter but also seeks the optimum "power point" of the panel.

Yes, I'd consider the Rogue controller as it is "state of the art" and just released. It has battery voltage sense wires. It is a similar price. If you do decided on Tristar instead get the 60 amp version as it is more efficient than the 45 amp version.

seraphim wrote:


Read a good description of what the mppt controller does - basically a dc to dc converter - and I think that's the way I'll go. The Tristar seems more than adequate, and it has a heat probe. It also permits custom setting of the various levels etween charging modes, so it can be set to the battery manufacturers specs. Do you have any other suggestions for controllers?

[seraphim]

BTW - I liked the *grin* lol. You ever get over to Cincinnati I'll buy a you beer.

[seraphim]

Thanks Don

That's the main reason I was counting amps: I'm willing to spend a few more dollars for a system which will charge faster. If a 24v panel will charge faster than a 12v - after the mppt controller converts it to 12v at a higher amperage, I was willing to spend the money.

Thanks for helping me understand things lol. Sometimes I read too much into explanations and I'm not sure if it's accurate.

Read a good description of what the mppt controller does - basically a dc to dc converter - and I think that's the way I'll go. The Tristar seems more than adequate, and it has a heat probe. It also permits custom setting of the various levels etween charging modes, so it can be set to the battery manufacturers specs. Do you have any other suggestions for controllers?

[pianotuna]

Hi,

A qualified yes to both.

As the battery reaches 85% state of charge it will taper the acceptance rate to about 12.5 amps per hour (per 100 amp-hours of bank). Increasing voltage will merely take the battery above the "gassing" voltage (which is temperature dependent), so "smashing" the battery with higher and higher voltage doesn't do a heck of a lot for charging.

The other reason MPPT is good is as temperatures rise panel voltage falls. But it takes a LOT more heat for a 24 volt panel to drop below 14.8 than it does a 17 volt panel.

No matter whether you go PWM or MPPT insist on a temperature probe for the battery bank. That will idealize the charging voltage.

[seraphim]

I have one more question, and it will help me decide which equipment to buy. It's a question I can't find a direct answer to, and I don't want assume:

All other things being equal, When a battery is being charged, will an increase in amperage charge the battery faster? I have been assuming 'yes', which is why I have been looking at the voltages of various solar panels.


It has been my assumption that an MPPT controller will convert the extra voltage of a 24v panel into a higher amperage while charging a 12v battery - thus decreasing charge time.

Is my assumption accurate?

[mena661]

JiminDenver wrote:
I'm a craigslist addict and checked a few Ohio areas. I found a 230w for $230, a 200w for $200 and a 275w for $200.

This is the listing for the 275w

275w in Ohio

Not sure what area you are in but craigslist is always fun to check.

I never find what I want on CL. Or if I do, it's always cheaper somewhere else.

[JiminDenver]

The closest I can find to there is Indy for 200w and 235w panels at a $1 a watt.

click

I'd be snagging that 275w panel if I lived closer.

[seraphim]

Thanks Jim. We're in the Cincinnaati area. I didn't even think of Craigslist *duh*

[JiminDenver]

I'm a craigslist addict and checked a few Ohio areas. I found a 230w for $230, a 200w for $200 and a 275w for $200.

This is the listing for the 275w

275w in Ohio

Not sure what area you are in but craigslist is always fun to check.

[seraphim]

The Grape 280 at Home Depot is starting to look better. Same price as the Kyocera, but I don't kno wif I can find the Kyocera locally.

Added - just checked the prices at Lowes: they sell the Grape 280 panel for over $700!

[seraphim]

Ouch! The comparison site listed the 390 at $585....

Pianotuna - yea, after the initial usage data and some early monitoring, the monitor may become unnecessary. For my first experience with a solar system, though, it ought to be useful.

[mena661]

All I would like is one big panel to be honest. Eek! That Grape Solar panel is $1000. LOL! No thanks. The Kyocera 315W is $400 on Wind & Sun.

[pianotuna]

Hi Seraphim,

That's ok. I don't believe in amp-hour counters. *grin*