Lifeline AGM Charging Conundrum

[MsNomer]

Well, that's a bummer. It's the absorption stage I'm missing.

Thanks for saving me the hassle of finding out the hard way.

[markopolo]

I was still curious about finding a solution for the problem so searched & read a bit more. It looks like there's a chance you can solve it with the equipment you already have.

NOCO Genius26000 + SC-2030 + TM-2030

The SC-2030 can function as a DC-DC charge controller. It is limited to 30A input.

The Noco 12V AGM+ mode is 15.5V 26A and would be used only to supply the SC-2030. the Noco would no longer have a direct connection to your batteries as 15.5V is too high for them. PWM controllers pull down voltage. If the PWM SC-2030 pulls the voltage down enough to keep the Noco in bulk or absorption stage then the problem would seem to be solved.

You would need an A/B selector switch to chose either solar input or Noco input. Remember 30A max input.

Booster would be able to advise if there would be any concerns about switching the solar panel like that. Bogart's diagram indicates that's how they do it.

When used with our SC-2030 Solar Charger, the Trimetric is in control of the charging process. It drives the SC-2030 until the two criteria are met so that the state of charger indicator may be reset to 100%.

Link: How to Ensure Proper charging with converter-chargers - Bogart Engineering

[avanti]

Originally Posted by markopolo

PWM controllers pull down voltage. If the PWM SC-2030 pulls the voltage down enough to keep the Noco in bulk or absorption stage then the problem would seem to be solved.

So, this is just a random thought, and I hope I am not just being pedantic, but:

PWM doesn't literally pull down voltages, but only the average voltage over time--it controls the duty cycle of a full-voltage square wave. I.e., at any given time, the voltage is either zero or the full input voltage. So, for example, a PWM LED dimmer doesn't literally dim the LED--when it is on, it is fully-on. It is your eye that averages the brightness over time.

I have no idea whether this affects your argument or not. It depends on how the voltage is being measured at the next stage. dunno.

[markopolo]

Precise information is always best so your clarification is welcomed.

Hopefully, it has no affect at all on the proposed solution. The Noco would need to see the SC-2030 as a battery needing recharge. That's what matters.

Bogart indicates that a 15V or 16V power supply is what is needed if using their PWM solar controller as a DC-DC charge controller. If the Noco errors out then a relatively inexpensive power supply could be used instead.

[booster]

I don't see any problem with the solar panels as the charger appears to be connected to the battery and on at all times. What you don't want is for the panels to be connected when the controller does not have a battery on it.


This seems like a lot of work to get 30 amps of charging. A PD would handle the shore power easily if manually guided, alternator would be close to correct so disconnect when near full and let solar finish. Getting the solar to bulk may be an issue, but before I blew it off I would check with Bogart. I think if the right timer is set long enough it may run a full cycle to return/tail amp setting. The information is all there for that to be achieved so they may have a way if you ask. Bogart is great to deal with.

[MsNomer]

We have decided that the Sure Power relay has died. Super bad timing. MrNomer is planning to bypass it with a manual switch until we can do better.

[markopolo]

The relay drive current is 1.5A on the Sure Power 1314-200 & 1315-200 models. For comparison, Blue Sea's 120A ACR is only 0.175A. That's a substantial difference particularly when supplied by solar panels. Blue Sea also has higher cost bi-stable units.

[MsNomer]

Marko, could you put that in plain English? Are you saying the parasite draw of the Blue Sea is less?

We have decided not to buy another Sure Power. This is is our second. Also, we want to consider the possibility of switching to lithium at some point.

HOWEVER, even with a hard-wired direct connection across the Sure Power's terminals, we get no alternator charging.

[markopolo]

The power usage to hold the relay closed is much less for the Blue Sea unit compared to the Sure Power. It's kind of like a parasitic load but not quite. The parasitic loss (IMO) for the Blue Sea would be 15mA used when the relay is open. It's 13mA for the Sure Power. 0.015A vs 0.013A, basically the same.

The 0.175A Blue sea vs 1.5A Sure Power large difference occurs when the chassis & house batteries are joined.

Originally Posted by MsNomer

............... HOWEVER, even with a hard-wired direct connection across the Sure Power's terminals, we get no alternator charging.

That could be a fuse/breaker problem on the wire run from chassis battery to house battery.

[MsNomer]

14+V is flowing from van battery to one Sure Power terminal. Other terminal shows lesser house battery voltage. Why doesn’t connecting those two terminals directly allow van battery voltage to flow to house batteries?

[markopolo]

How are you determining that current flow is not what is expected? What was the SOC of house battery then?

Sufficient voltage along with supporting current (amps) availability is required to raise voltage.

A poor house battery to Promaster van body ground could be the cause of lower than expected voltage at the house battery. Check house battery to shunt and shunt to van body connections. A high resistance poor connection will waste current. Sometimes you can feel the heat radiating off a poor connection without even touching it.

[MsNomer]

He is using a volt meter, which is reading consistently with the Trimetric.

We lost the SOC reading from the TM a few days ago when he disconnected the battery and won’t get it back until we somehow make it to 100%. We estimate we are fluctuating between mid-80’s to mid-90’s. Voltage at the meter early morning before sun (no concurrent loads, no solar input) is usually 12.6. If this were OCV, it would correlate to about 85% SOC. When we once tested OCV, it was very close to this condition.

There is 0.8 Ohm resistance from shunt to van body. He has checked every connection.

[booster]

Originally Posted by MsNomer

He is using a volt meter, which is reading consistently with the Trimetric.

We lost the SOC reading from the TM a few days ago when he disconnected the battery and won’t get it back until we somehow make it to 100%. We estimate we are fluctuating between mid-80’s to mid-90’s. Voltage at the meter early morning before sun (no concurrent loads, no solar input) is usually 12.6. If this were OCV, it would correlate to about 85% SOC. When we once tested OCV, it was very close to this condition.

There is 0.8 Ohm resistance from shunt to van body. He has checked every connection.

You really will need to find that resistance from the shunt to the body as that is quite high, although what really counts is the shunt to negative terminal of the alternator and that involves, usually, a less than stellar braided ground strap from the engine to the body. Same is true for the the other charge sources on the ground side, resistance from shunt to negative charge source connections (solar and shore power.


There is probably a decent chance you have a bad ground between the shunt and the negative on the alternator. This is more common than many folks realize, I think.

[MsNomer]

Well, if we didn’t have bad luck, we wouldn’t have any at all. We decided to try to find an electric site in a NM state park for Thursday night, since we knew the weekend would be impossible. That part worked. We decided to bleed the batteries down to 12.6V so the NOCO would start. That part worked. We went to bed happy campers with the NOCO charging away.

Woke up at 3am with no AC power and the batteries bleeding out because I had turned the freezer to its lowest setting. At least it wasn’t our fault—the whole campground was blacked out. The camp host was running his generator, which told us this is a common event. So of course the NOCO is sitting fat and happy with its @#$& green light blinking and we have no idea what our state of charge is.

MrNomer got rid of that 0.8 Ohm resistance yesterday afternoon. This morning, he will check the van's ground. EDIT: Van ground is good.

[MsNomer]

We now have alternator charging through a wire directly from van battery to house battery with switch and 30A fuse.

Thank you guys for hanging with us on this. We appreciate your input, and, just as important, the feeling that we were not alone.