Small RV system problem - bad TriStar?

System · November 2006

In my earlier thread, I mentioned how I boiled out much of the Trojans electrolyte, and questioned how the TriStar should work regarding the LED's.

I tested by draining batteries to 50% SOC, disconnected batteries and PV's to make sure the TriStar was reset, then plugged everything back in. Bulk charging was uneventful (no blinking LED's, just solid transitioning from r/y to y to y/g to g. PWM regulation kicked in (according to the 2 per second green blink, so I let it go. Ran some errands, came home a few hours later to see the batteries again boiling away. Measured voltage to batteries, 15.3. Just then it kicked into 'float' (one flash per second), and voltage to the batteries read 14.3.

Called Morningstar tech support, confirmed each switch setting, reconnected batteries and panels, measured voltage (again, way too high.) Disconnected RTS and battery sense wires, no change.

So, they are sending me a new controller. I lost more electrolyte from the new Trojans, so while I'm waiting a week for the new TriStar, I'll bring them back to the dealer and have them check the specific gravity of each cell to see if more acid will have to be added to make up for the boiling loss I made up for with distilled water.

I hope the next one behaves better...

John F
LV, NV

BB. · November 2006

Re: Small RV system problem - bad TriStar?

When the batteries were at "float" charging state and 14.3 volts... Was the charger still supplying charging current to the batteries or was this a "surface charge" at this point?

http://www.trojan-battery.com/Tech-Support/BatteryMaintenance/Charging.aspx

If the charger is floating, the voltage should be around 13.2 volts (at ~80F)... 14.3 volts of charging would still be "bulk charging" and too high for long term floating of the battery. Charger controller reading the correct voltages and charging programmed correctly (I assume yes)?

Sounds like the charger is either programmed ~1.1 volts too high, or the temperature correction sensor/circuit is not working correctly.

-Bill

crewzer · November 2006

Re: Small RV system problem - bad TriStar?

John,

Let's try this from another perspective: I see the current temperature in LV (McCarran?) is 55 F. What was last night's low temperature in your location?

More later...
Jim / crewzer

System2 · November 2006

Re: Small RV system problem - bad TriStar?

Low temp last night about 41. The Morningstar tech support guy said if the RTS was damaged, the TriStar would compensate by sending more voltage, but not THAT much more. We disconnected the RTS to be sure, and it had no effect. Besides, the difference in 5 degrees and 104 degrees should be only 1.65 v.

The battery voltage, after just a few minutes rest, when this was going on was 13.2v. Hook up the panels, measure battery voltage, and it was 14.3 in float, when it should have been 13.4. I had dip switches 4,5 and 6 set for program 5 (PWM voltage 14.6), but PWM state voltage to batteries was 15.3, enough to boil the batteries.

Any clues? I'm out of ideas, it just seems to deliver more voltage than it should in all charge states. If there was a custom program in it, dips 4,5 and 6 would all have to be 'on', otherwise program selection from these switches will be in effect.

John F
LV, NV

crewzer · November 2006

Re: Small RV system problem - bad TriStar?

John,

I tested by draining batteries to 50% SOC, disconnected batteries and PV's to make sure the TriStar was reset, then plugged everything back in. Bulk charging was uneventful (no blinking LED's, just solid transitioning from r/y to y to y/g to g. PWM regulation kicked in (according to the 2 per second green blink, so I let it go. Ran some errands, came home a few hours later to see the batteries again boiling away. Measured voltage to batteries, 15.3. Just then it kicked into 'float' (one flash per second), and voltage to the batteries read 14.3.

Assuming this morning’s low temp in the LV area was perhaps ~40 F, that the batteries are “outside” in the camper, and that the TriStar’s battery selector is set for type “6” (14.8 V absorb/PWM and 13.4 V float, both ref 77 F / 25 C), you may be witnessing nominal operation. Whether it’s optimal is another issue, and I’ll come back to that.

Typical temperature compensation for a 12 V battery is -0.03 V/degree C. If the battery temp was ~47 F, the TriStar would have increased the absorb/PWM voltage by ~0.5 V above the reference value. So, a measurement of ~15.3 V sounds about right.

The correct temperature compensated float voltage would also have been ~0.5 V above 13.4, so 13.9 V would have been the correct voltage. 14.3 V is obviously higher, but it takes the big batteries a while to drop from 15.3 V to 13.9 V when connected to a charger and there’s no load.

Like all flooded-cell batteries, the Trojan SC225’s will “boil” when they’re being correctly charged. They should boil “gently”, but still audibly, when they’re in absorb/PWM mode, and they should boil vigorously when they’re in true EQ mode. Both conditions are clearly audible.

The challenge is to find the optimal balance between gentle boiling while in absorption mode and minimizing water consumption. Note that just the water is “boiled” off (electrolysis breaks the water molecules into oxygen and hydrogen atoms, and the two gasses escape). The lost water needs to be replaced before the internal plates are uncovered. The acid itself does not suffer any substantial loss, and should not need to be replaced.

You may decide that Trojan’s charging voltage recommendations are too high for your comfort level. Note that the standard recommendation for flooded-cell batteries is ~14.4 V for absorb, and ~13.4 V for float, both ref 77 F / 25 C. However, US Battery recommends something over 15 V absorb for their batteries!

Accordingly, you may wish to try a different setting on your TriStar. The battery type “5” (14.6 V, 13.4 V) may be a fair compromise between Trojan’s recommendation and the “standard” suggestion. Nonetheless, you should still hear the batteries boiling when in absorb/PWM mode. And, if the batteries are cold, the TriStar will boost the charge voltages, and when they’re hot (hot? In LV?), it will reduce the charging voltage.

How you proceed is of course up to you. However, unless I’ve missed something here, I’d expect the new TriStar to operate in much the same way under essentially identical conditions.

I hope this helps, and Good Luck!
Jim / crewzer

P.S. I was writing this while you posted your response, so my assumptions and numbers are off a bit. But, they're close enough. Nonetheless, the TriStar and/or the RTS may be faulty... it's just tough to diagnose from so far away.

crewzer · November 2006

Re: Small RV system problem - bad TriStar?

John,

Low temp last night about 41… dip switches 4,5 and 6 set for program 5 (PWM voltage 14.6)

OK… the numbers make even more sense now. If the battery temperature dropped to 41 F (5 C), the temperature compensation would be 0.6 V. For battery setting “5” (14.6 V absorb/PWM, 13.4 V float), you should have seen readings of ~15.2 V (absorb/PWM) and ~14.0 V (float) measured at the batteries. These numbers are close to what you measured, and the difference could have been caused by a bad RTS and/or mis-calibrated meter, or perhaps if you measured them at the Tristar's battery cable connections.

I think the system is operating close to nominal. It’ll be interesting to see what happens with the new TriStar and/or new RTS installed. Since your system is occasional use (no daily discharge/charge cycles), one other consideration may be to reduce the battery setting to 14.4 V / 13.4 V.

HTH,
Jim / crewzer

System2 · November 2006

Re: Small RV system problem - bad TriStar?

<<I think the system is operating close to nominal.>>

I guess I'd feel more comfortable if it were 'more' nominal <g>. Even with temp compensation considered, it does not seem to be regulating properly. The meter is a Fluke which gets (almost) daily use as part of my job, and I don't think it can be too far off.

We'll see if the new TriStar behaves differently in a week or so - the next camping trip is still 2 weeks away, so plenty of time.

I certainly heard the batteries bubbling away, I can see that as being normal in late bulk stage or anytime in regulation, but (without knowing any better) just imagine they should not do that in 'float'.

I received the Blue Sea switch, it is a cute thing. I'll wire it so as 'common' is connected to the battery bank pos, 1 is the output pos from the TriStar, and 2 is the out/in to the Magnetek converter. This way, I'll be able to select '1' for solar charging only (no loads in the trailer will be active, since the Magnetek will have no voltage, so none of the circuits will have power), select '2' for normal operation of load devices (as well as 'gentle' charging from the Magetek if plugged into 110 AC at home or rarely at campsites with power), and 1+2 should allow me to solar charge while using load in the trailer , and 'off' will isolate the batteries for long term storage.

Do you see any problems with this arrangement, or have any better suggestion? Thanks for your help,

John F
LV, NV

ps - where are you located, and what do you do for a living?

Patman3 · November 2006

Re: Small RV system problem - bad TriStar?

Maybe the Tristar thinks the voltage is lower than the batteries really are, ie there is some voltage drop in the wire/fuse/breaker connection from battery to controller? Can you use the Fluke to measure voltages right at the controller unit, including both ground and positive points?
I live just outside of Vegas in Boulder City, it's going to be VERY cold the next couple nights (30's haha).

crewzer · November 2006

Re: Small RV system problem - bad TriStar?

John,

I agree that the goal is to end up with a correctly operating TriStar + RTS. I also agree your Fluke is probably giving you good readings. My real point's above are that temp comp voltage adjustments aren't necessarily trivial, and that "boiling" is normal during charging. However, the batteries should not be bubbling along when in Float mode.

Your switch plan generally looks good. However, you might want to check with Morningstar about disconnecting the battery lines from the TriStar while the battery sense lines remain connected.

My home is in Vienna, Virginia, a suburb ~15 miles west of Washington, D.C, and I'm a technical program manager. I'm on business travel in the St. Louis area today, and I'm planning to return home tonight.

Regards,
Jim/ crewzer

System2 · November 2006

Re: Small RV system problem - bad TriStar?

<<Maybe the Tristar thinks the voltage is lower than the batteries really are, ie there is some voltage drop in the wire/fuse/breaker connection from battery to controller? Can you use the Fluke to measure voltages right at the controller unit, including both ground and positive points?>>

No voltage drop between the battery connections on the TriStar and the battery posts themselvs that I can measure. The run is only 4' to one battery and 8' to the other using twin 10 guage. Why twin? Because when I did the 'diagonal parallel' wiring between batteries, I wound up with an extra #10 going to each battery from the area of the Magnetek / TriStar, so just combined them.

<<However, you might want to check with Morningstar about disconnecting the battery lines from the TriStar while the battery sense lines remain connected.>>

The Morningstar tech had me disconnect batteries a few times when testing (changing programs, measuring voltages, etc) and didn't say anything about disconnecting sense wires, so it either doesn't matter or he overlooked that. I'll email them with that question to be on the safe side.

Jim/crewzer - my wife was born & raised in Silver Spring MD, not too far from your area. We make it back there twice/year to visit her family & friends.

Thanks for your help,
John F
LV, NV

System2 · November 2006

Re: Small RV system problem - bad TriStar?

Disconnecting the battery voltage sense lines hadn't crossed my mind when I open the switches to isolate the PV's and TS-60 for periods of time over the winter when I'm not at the camp. This is the second year I've done that and so far - - no problems. I disconnect, because during winter, there's no load and even when set at a reduced voltage, the batteries still end up being overcharged. About once a month, I close the switches for a sunny day, just to top up the batteries. I don't want to leave any load on, because the PV's could end up blanketed with snow for weeks and I wouldn't be able to get there to clean them off. Since it's only used in Summer (so far) I didn't make arrangements to tilt them up for Winter.
Wayne

System2 · December 2006

Re: Small RV system problem - bad TriStar?

Well, this is all working out for the better. I got the TriStar meter, the only bad thing about it is that the controller is mounted near the floor, so I can't see it without getting on my knees and bending over with my head nearly to the floor of the camper. It is sure better than getting my meter out every time I want to check voltage, though.

Rewired yet again, adding a fuse near the pos battery of the bank, and added a 4 position Blue Sea switch to allow isolation of the solar charging and inverter charging circuits, or allow both, or disconnect the battery bank completely. It works fantastic, thanks Jim / Crewzer for the recommendation. How do you design a high-current switch that has no 'off' state in between switch positions? Another unanticipated benefit of the switch is that if plugged into 'shore' power, I can use all DC circuits with the battery bank disconnected from the 'less than perfect' charging of the Magnetek converter. And, I don't have to worry about the TriStar and Magetek 'not playing well together'.

I also got a hydrometer (not temp compensated), so have to look up a table somewhere that will list various charge states at various temps, or at least get a conversion formula - anyone got a link handy for this info?

Thanks for all of your help on this solar project, it is really coming together.

John F
LV, NV

crewzer · December 2006

Re: Small RV system problem - bad TriStar?

Great news!

Check Trojan's on-line manual for their SG temp comp instructions. Also, Bill Darden has some great info on his site.

http://www.trojanbattery.com/Tech-Support/BatteryMaintenance.aspx
http://www.uuhome.de/william.darden/

Silver Spring. eh? Not too far away...

HTH,
Jim / crewzer

Small RV system problem - bad TriStar?

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