How long to charge?

Re: How long to charge?

Jim / crewzer,

Thanks.  The custom program also allows a different length of time before float if battery was 'low' (I set 'low' to be 12.00v, or about 43% SOC), and I added an extra hour before float if they reach this level.

It also can cancel float altogether if the batteries reach a certain very low voltage, which I set at 11.81v, or 30% SOC.

BTW, the default setting for time before float after reaching 30% PWM was 3 hrs., I changed that to 2 hours after reaching 20% PWM.

In reality, I've found that if the batteries reach 60% SOC, it takes pretty much all day of sun to get to 20% PWM, so I'll probably not reach the float stage anyway in one day.  I guess I'm slightly undersized PV-wise.

I've also programmed the LED's to change states so I can monitor approx. SOC during use rather than charging state.  Even though I've got the remote LED, I can tell at a glance the approx. juice left instead of having them show charge voltage (we are usually gone during the day hiking when the batteries are charging anyway.)  So, I custom set it to change from green to green/yellow at 80% SOC, solid yellow at 65% SOC, yellow/red at 50% SOC, and solid red (warning) at 35 SOC.  The custom programming is really a cool feature of this unit.

I wish there was a way to have it shut batteries down completely when the batteries reach a certain SOC (30%?), but this would require either (1) buying another TriStar (2) or some fancy rewiring and flipping a dipswitch to go from 'charge' mode to 'load control' mode.

I've found the AH figures for the Trojans to be wildly exagerated after monitoring actual usage, but I guess that is to be expected since I don't want the batteries to reach the 10.5 v that the ratings are based on...  That said, I can still get 2 solid days / nights, and push 3 out of them without recharging (if no sun) and not get below 50% SOC, which was my original 'low' goal.

John F

Re: How long to charge?

Jim / crewzer

<<Looks like you’re having a lot of fun with the TriStar and that it’s generally serving you well. As you noted, your PV array (160 W STC) is a bit small for your battery bank (~450 Ah). However, since your system sees but occasional use, you may be able to squeak by.>>

No doubt, I'm undersized PV-wise for my battery capacity. It takes 1.5 days of full sun to reach 'float' if batteries are at 60% SOC or lower. What I don't understand, is when PWM reaches 19% (my setpoint to start the counter of 2 hr. to float) I'm only sending 1.1A to the batteries. Would more PV send more current at all PWM levels, thus proprotionately reducing my charge time? Or would it just send more current in bulk and early PWM mode to reduce the battery charge time?

<<One would be to connect a Morningtar SunSaver controller between your batteries and your loads. This controller would cut off the loads when the battery voltage drops to 11.5 V and then reconnect when the battery voltage rises to 12.6 V. The 10 A LVD model costs ~$60, and the 20 A LVD model costs about $80. One of these might make for a very clean and simple solution, and could also serve as a basic backup controller in case of future TriStar difficulty.>>

11.5 v disconnect sounds quite low, ~ 10% SOC. Wouldn't the Trojans be 'toast' by at that state of discharge? Oh, they would recover after rest to 12v or so I suppose.

<<Finally, and I suppose there’s some possibility that your wife may not be happy with me and this suggestion , yet another option is the Morningstar Relay Driver.>>

Yes, this looks quite cool for a techno-weenie like me, but all bits would have to be hidden from the wife like you say. The main 'bits' I would need would be extra wiring and a solid-state relay or two from the looks of it. Definately overkill, but cool nontheless.

The last option I've thought of is 'modifying' the TriStar (cutting a slot in the cover to be able to access dip switch 1 to change it to load control mode, but this would probably require an extra BlueSeas high-current switch as well, so that would complicate operation beyond my wifes' capabilities (and maybe mine as well.)

We camped over New Years (3 days/nights in Death Valley), and only got down to 75% SOC after that, so I think I may call it good. Furnace usage was minimal, though. A friend (with a larger camper and a more 'high maintenance' wife ran down his dual series T-105's after 2 nights, so had to move them to my setup and use jumper cables from the TriStar to get his charged enough to get him through the 3rd night. I'm feeling better about my choice of the dual SCS225's (plenty of AH for my needs.)

Thinking that one more PV panel, permanantly mounted this time, might be in order if it will allow me to do a full charge in one day... Maybe another Kyocera (65W this time), which would put me from 160W PV to 225 W. I'd like to use the UniSolar for the permanant mount because of its durability, but afraid the operating voltage is too much lower than my Siemans and Kyocera, and will drag them down.

Thanks for the suggestions,

John F
LV, NV

Re: How long to charge?

We've made a tradition of camping at Death Valley Texas Springs campground (up the hill from Furnace Creek) for the last 12 years over the New Years holiday. No generators allowed up there, and of course no power hookups, so perfect for us.

There was a large RV there, I had to go over to talk to the guy - he had 5 Kyocera 130W panels on top (complete with tilts for the winter sun angle), 8 Optima AGM's, a TriStar 60, and a Xantrex 3k inverter for microwave, satellite, TV, blow-driers, etc., all the comforts of home. Retired, he & wife live 6 months in the RV and 6 months in a sailboat (generator on the sailboat.)

Could you recommend a charger I could use to keep the batteries maintained in the summer months when we don't use the pop-up much and I've got the batteries stored in the garage? I've though about getting a Xantrex 20+ for semi-permenant mounting in the trailer (and getting rid of the crap RV converter), and then using it in the garage for summer battery maintenance. OK?

Thanks for your help.

John F
LV, NV