Solar Charger & Appliances with Max Voltage <= 14V

carbon60

Explorer
Hi All,

So I've got a sweet solar setup installed in my trailer with proper controller and a pair of Trojan T105s. Love it.

Problem: neither my Propex furnace nor my Maxxfan like seeing high voltage (over 15V for the furnace and 13.5V for the fan) but the Trojan's want to bulk at 14.82V and 16.2V to equalize. Since equalization is automatic with this controller, both appliances lose their mind.

I found this DC-DC regulator:


Is there a smarter approach to this problem that I have not explored? Comments?

P.S. The Propex needs 1.6A and the fan I do not know, will have to measure.
 

john61ct

Adventurer
Never enable automated equalizing.

Best off shore power, isolated from any loads, and ideally each battery unit separately.

Amps are amps volts volts, so the batts don't care about the actual charge source long as you are hitting the spec'd protocol from the mfg.
 

shade

Well-known member
Is it possible to disable equalizing altogether on the charge controller? If so, you could turn it back on occasionally as needed, and disconnect loads during that period.

You could also disconnect the batteries from the entire system and use a shore power charger for equalization.
 

jonyjoe101

Adventurer
I use those 12 volt voltage stabilizer on my swampcooler which can't handle any voltage surges. They work extremely good, havent lost and fans/pumps since I been using them. I highly recommend them if your equipment can't tolerate any overvoltage surges. They work in realtime so it protects no matter what the input voltage is, I tried using overvoltage protection relays but the short delay for the relay to activate will destroy equipment. They also sell ones that can handle 10 amps.

Its an extra piece of equipment but well worth the price, I lost about 5x 12 volt fans before I finally got a voltage stabilizer. No matter how well you set your controller etc, sometimes you might get a stray voltage surge.
 

luthj

Engineer In Residence
A DC-DC converter is likely the way to go.

In a trailer that moves around a fair bit, a monthly equalize is not needed generally. If the batteries are cycled deeply and often, and you rely on solar, you may need a monthly equalize (recovery) charge. This doesn't need to be 16V (at 75F), often 15-15.3V @ 75F is enough. This helps to recover the sulfation that builds up over multiple partial charge cycles, common to off grid applications.
 

john61ct

Adventurer
Monthly is in fact a **much less** frequent interval than what most setups require to maximize longevity.

It is true that **if** the rig is getting the bank to 100% Full most charge cycles, then

equalizing - if recommended at all by the maker - can be less frequent.

That "if condition" is met by maybe 3% of DC electric setups while off grid, no matter the quantity of power available, just from poor adjustment of charge sources' profile parameters.

And the maker specs for the equalization process should be followed as precisely as possible, ideally at the top of the range given.

For FLA be sure to keep water topped up.
 

DaveInDenver

Expedition Leader
Too many variables to generalize into a single statement but Odyssey in their tech manual touches on what @john61ct is saying. If you charge properly, which in the case of Odyssey means using 14.7V absorption rather than 14.2V and each time return 5% more capacity than you remove, the number of cycles you can expect from their batteries increases quite a bit.

This test was done on a PC545 which is typically listed as a 12 or 13 A-hr battery but they call it 11.5 A-hr. They weren't doing gentle discharges, 2.3 A represents a 0.2C rate taken down to 10.02 V.

They did a 0.05C 24-hour conditioning when the battery appeared to have lost capacity and that appears to only provide a short term recovery. They specifically recommend against ever exceeding 15 V for their batteries.

Screen Shot 2019-10-22 at 10.50.32 AM.png
 

dwh

Tail-End Charlie
Hi All,

So I've got a sweet solar setup installed in my trailer with proper controller and a pair of Trojan T105s. Love it.

Problem: neither my Propex furnace nor my Maxxfan like seeing high voltage (over 15V for the furnace and 13.5V for the fan) but the Trojan's want to bulk at 14.82V and 16.2V to equalize. Since equalization is automatic with this controller, both appliances lose their mind.

I found this DC-DC regulator:


Is there a smarter approach to this problem that I have not explored? Comments?

P.S. The Propex needs 1.6A and the fan I do not know, will have to measure.
As long as the loads total less than 6a that'll work. There are also units with adjustable output voltage, which I would probably use instead. I imagine the fans and propex might be happier at 13v or 14v, instead of 12v. Plus, starting at 12v, voltage drop might be an issue, so starting at a higher voltage might be good.

https://www.amazon.ca/DROK-Voltage-Regulator-Converter-1-2-36V/dp/B00C4QVTNU/ref=mp_s_a_1_8?keywords=dc-dc+voltage+converter&qid=1571765036&sprefix=dc-dc&sr=8-8
 
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john61ct

Adventurer
The only AGM that can tolerate true equalizing is Lifeline, and that only following their protocol precisely.

The other AGM vendors stopped recommending it years ago. But each do still have a "conditioning" protocol for restoring capacity, preventing sulfation from PSOC abuse, which AGM is particularly vulnerable to. Same with overcharging, since lost electrolyte cannot be replaced.

Best of course to just get to 100% Full each cycle, or at least as often as possible.


They weren't doing gentle discharges, 2.3 A represents a 0.2C rate
That in fact is pretty gentle, about normal for House loads, but nowhere near rates used for winching, cranking batteries, powering a microwave via inverter. Ideally such loads are supported by concurrent charging input.

> taken down to 10.02V

That's crazy low, 10.5V should be considered by regular users a "do not approach" zero SoC point,

only rarely touched (and then only briefly) when capacity testing, commissioning protocol etc.

Start recharging immediately after hitting that low, sitting there will lose a lot of lifecycles.
 

john61ct

Adventurer
13.8V is a common standard for DCDC converters and load-carrying power supplies, as opposed to chargers.

If you want to have a "UPS standby" type battery, on say a safety / emergency / nav gear circuit, that voltage is within the Float range for many suitable lead batteries.
 

DaveInDenver

Expedition Leader
> taken down to 10.02V

That's crazy low, 10.5V should be considered by regular users a "do not approach" zero SoC point,

only rarely touched (and then only briefly) when capacity testing, commissioning protocol etc.

Start recharging immediately after hitting that low, sitting there will lose a lot of lifecycles.
That's important to highlight. Odyssey uses 10.02 V as their 100% depth of discharge when rating capacity, so right off the top you have to adjust for real world values. But they are apparently somewhat tolerant as long as you follow good charging practices.
 

john61ct

Adventurer
Very unusual.

I bet if you actually measured using a precisely timed CC load discharge at the standard 0.05C (20-hour rate)

there would be very little usable energy between 10.50 and 10.02V.

I would use 10.5V as zero SoC anyway for my benchmarking SoH%, just to be standard across all lead battery types.

The top 100% still following maker specs though.
 

DaveInDenver

Expedition Leader
Very unusual.

I bet if you actually measured using a precisely timed CC load discharge at the standard 0.05C (20-hour rate)

there would be very little usable energy between 10.50 and 10.02V.

I would use 10.5V as zero SoC anyway for my benchmarking SoH%, just to be standard across all lead battery types.

The top 100% still following maker specs though.
Indeed, there's very little left once you go below 11 V and by 10.5 V it might be possible to count individual electrons. Heck the ones that are flowing at 10.02 V are probably just as likely energized from background radiation as being forced by the battery. I suppose the one thing you can say is there is no doubt you have used the battery completely and any lower certainly risks reversing cells that aren't already weak.
 
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