inexpensive batt charger with equalization

[john61ct]

Specifically Sterling's ProCharge Ultra has the necessary adjustability.

The sister ProMariner Pronautic P line may be cheaper where you are, not sure if support is as good as with Charles.

[GrowleyMonster]

I bought a spare charger on fleabay for my 48v bank and watched in amazement as it ramped up to almost 64v first time I hooked it up to test it. After a couple of hours of carefully monitoring battery case temp, etc, it started to ease back down. Hmmmm not many smart chargers actually do a proper equalization and this was nearly 2v above the normally qouted equalization voltage for a 48v bank of FLA batts. I have been staying at GFs house lately but I will go to the boat tomorrow and check the brand and model. It was cheap, though. They probably make a 12v or 6v charger as well as this beefy looking 48 volter.

My old dependable go to charger for equalizing is a 2kw Variac and the rectifier from an old arc welder, with the necessary ammeter, voltmeter, etc. I run it from shore power and also sometimes from my little Ryobi lunchbox generator, both underway and shut down at the dock or at anchor/drifting. This is of course totally fully manual with no protection or idiot proofing other than a 20a fuse on the primary side and a 50a fuse in the output circuit, so you have to pay attention and know what you are doing to use this thing. Also there is no galvanic isolation, something to think about, if you have no isolation transformer. Just sayin. A 2kw Variac can usually be found for around $100 and a good rectifier maybe even free if you are a good scrounger. Need volt and ammeter in the output of the rectifier to monitor charging, and it is handy to have an ammeter in the primary circuit so you know when you are close to the max on the portable generator or mains breaker.

Another great thing about the Variac is the total flexibility. I can charge a 12v or a 6v or an 8v or 2v or whatever battery. If one of my GC2 batts goes north on me, and I am left with a 42v bank, no problem. I can still charge just fine, and the motor and controller don't mind, I just have to do a bit of configuration to allow a lower minimum voltage.

If you have no interest in learning about charging algorithms or basic electricity, or are really paranoid about safety, give the variac method a miss. You can really screw things up bad with lack of knowledge or judgement. If you are a pretty good shade tree engineer and love to tinker, it is an option to consider.

I still haven't figured out how to MAKE the smart charger equalize. Seems like it just decides for itself. I don't really like that, now that I think of it. I really don't.

[john61ct]

Yes that out of control eBay is dangerous.

I never allow automated equalizing, only do manually.

I'm interested in the Variac setup, but without "scrounging" except online, can you post some links to specific models, maybe some basic howto's for complete noobs?

For my LFP per-cell balancing (3.45-3.65V), I've been looking at 4010 Duo iCharger, but that's $300+ for only 40A, might only need it once a year or so.

[GrowleyMonster]

Originally Posted by john61ct

Yes that out of control eBay is dangerous.

I never allow automated equalizing, only do manually.

I'm interested in the Variac setup, but without "scrounging" except online, can you post some links to specific models, maybe some basic howto's for complete noobs?

For my LFP per-cell balancing (3.45-3.65V), I've been looking at 4010 Duo iCharger, but that's $300+ for only 40A, might only need it once a year or so.

I am totally ignorant of Lithium battery charging algorithms including equalization. I actually didn't know that was a thing. I am much more familiar with good ol flooded lead acid batts.

For complete noobs? Depends on how complete. Like I said, some basic understanding of transformers, diodes, AC/DC current, and batteries is necessary for reasonably safe operation. I hope I am not giving you just enough details to put you or your boat or crew/passengers or divers in the water etc in danger...

But for the sake of knowledge, here goes. A Variac is actually the brand name for a particular maker of variable autotransformers. In most transformers, the primary and secondary windings are insulated from one another. Current in the secondary is induced by the current in the primary via electromagnetic force. Same is true in an autotransformer, except that the secondary winding is part of the primary winding. Or vice versa. There is no electrical isolation between them. A Variac is an autotransformer with a movable secondary tap, which gives the operator control over the voltage ratio. So 110VAC in, 0 to about 130VAC out. The ratio of currents is inverse to the voltage ratio, of course, because you can't create nor destroy energy. Some is transformed into heat of course, and so it is lost to the system. Anyway a Variac looks like this: <googling for variac pic>

https://www.ebay.com/i/162759421774?chn=ps&dispItem=1

It is NOT a regulator so pay no attention to that. The regulation is manual.

A full wave bridge rectifier is an array of four diodes, in its single phase form. A diode is a semiconductor that permits current to flow in only one direction. In AC, the current switches directions twice per cycle. So the diodes are arranged so that they form a diamond shaped circuit with each AC input connected to anode of one diode and cathode of another. Both remaining anodes connect to the positive DC output, both available cathodes connect to the negative DC output. So no matter which polarity state exists, current still can only flow in one direction at the output. The diodes essentially switch the current in time with the AC polarity switch, keeping output polarity the same. There is considerable ripple but it doesn't hurt batteries, no matter what anyone says.

So, the AC input into the Variac is converted to a different voltage, as desired by the operator. The resulting (usually) reduced voltage output feeds into the rectifier module and is converted to ripply DC. DC voltage and current are adjusted by the variac control. The DC output voltage and current are monitored carefully. The AC input current is monitored and multiplied by volts to get watts, so that the system can be adjusted for a specific output or a specific supply load limitation.

Here is a rectifier module. Two terminals are the AC input, two terminals are the DC output.

https://www.google.com/search?q=2kw+...XAoc_C_7M04cM:

The rectifier can also be constructed out of four discrete diodes by wiring them together as previously described.

Adjusting the voltage upward will of course increase charging current into the battery. And vice versa. Open circuit voltage and loaded circuit voltage are of course quite different. A knowledge of the laws governing electricity and electromagnetism are essential for anyone manually charging batteries with a variac. I will repeat: this is not sailor proof. There are no safeguards against reckless, careless, or ignorant operation, whatsoever. If you are comfortable with that and have the necessary knowledge and skill, then this system is beautiful in its simplicity, flexibility, and economy.

[kmacdonald]

IOTA are great chargers for little money.
https://www.iotaengineering.com/dlsx12.htm

[john61ct]

Originally Posted by GrowleyMonster

I am totally ignorant of Lithium battery charging algorithms including equalization.

The equalization comment was about your unexpected high voltage, nothing to do with LFP, can wreck lead though hence my warning.

Thanks for the science lesson, bookmarked for further study.

[RaymondR]

If you already have solar with a smart regulator with equalization the cheapest way to implement smart battery charging is to build a DC source using a transformer and a diode bridge and wire the DC output in parallel with the solar panels on the solar panel input to the regulator.

[john61ct]

Lots of SCs will fry doing that.