Sunday, June 18, 2017

Lithium (LiFePO4) Battery Charger Review and Comparison: OptiMate vs CTEK vs NOCO Genius



A while back I did a review of a lead acid battery chargers that has been one of my most popular posts, so when I needed a new lithium battery charger I decided to do another review and test. Here it is!

Some background on lithium battery chargers

I've been using lithium-ion batteries in my motorcycles lately.  Technically, these are lithium iron phosphate (LiFePO4) batteries  These are also sometimes called LFP batteries (and sometimes incorrectly called LiPo; this a slightly different technology). For ease, I am going to call them "lithium batteries" in this article.

I have both Shorai and Antigravity brand batteries in my bikes. And as it happens, I had two bikes with lithium batteries in storage for more than a year. Neither bike is in "running condition" so I thought it was time to charge their batteries.

Now most people may never need a special charger for these lithium batteries. If there is no drain on them, they can go a LONG time without charging (probably more than a year). So don't run out and buy one of these special chargers unnecessarily. If you need to leave your vehicle for more than a week or so, just disconnect the battery and don't worry about it, even for months.

Shorai publishes a nice chart of showing how you can use your battery voltage to estimate much charge your battery has left:

And if your battery charge does get low, Shorai explains how you might be able to charge the battery with some "regular" chargers here: http://shoraipower.com/charging. Note that you can NOT hook a lithium battery to a just any lead acid battery charger and forget about it! You need the right kind of charger and it is a careful procedure, read and follow the directions.
More detail on the problem using a regular lead acid charger with a lithium battery: Many or most electronic type lead acid battery chargers have a "desulfation mode" which cannot be turned off.  That mode will damage a lithium battery! Also, the final voltage for a lithium battery is different (higher), and a regular battery charger will not handle that.

Now, probably the THE BEST way to charge a lithium battery is to get a special charger with a Balance Management System that can charge the battery through the "Balance Connector", if the battery has one. This allows each individual cell in the battery to be "fully topped off". The Shorai does have a balance connector and Shorai sells a special charger for that port. If you want to buy a specialized charger like that, it's probably the best way to go!

On the other hand, many brands of lithium batteries do not have the special balance connector. Some of the manufacturers claim to have have a built in cell balancing circuit (EarthX is one). Others claim (like Antigravity) that it isn't necessary, and some just don't say anything.

Another feature of some lithium batteries is an "over-discharge protection circuit". If the battery is in danger of being drained too low, it disconnects the actual internal battery from the terminals on the battery's case. If the battery has triggered the protection, it cannot be charged until that protection is reset, this is often called "BMS reset". If the battery is not reset, the charger does not recognize that it can be charged. The manufacturer EarthX describes this well on their website.

What do I want in a lithium battery charger?

Because some of my batteries do not have balance connectors, I wanted a a charger specialized for charging lithium batteries without a Battery Management System that requires the special connector. A lithium battery charger should work using somewhat different charging steps and voltages and should definitely not have a desulfation mode. The charger should also be able to reset any over-discharge protection circuit inside a lithium battery.


The Contenders

A little research showed 4 chargers that interested me in the US$50 to US$100 price range on Amazon. Here is a list with the manufacturer's web page for each and also a link to the manual for each:

Noco genius G3500 3.5 Amp UltraSafe Battery Charger and Maintainer

User Guide
(about $60 on Amazon as of this writing)

Frankly, I wasn't thrilled with the regular lead acid Noco charger I checked out back in 2012. But I thought I should check them out again.The G3500 is a fairly hefty 3.5A charger, so that was good. And it is a multipurpose charger that works for lead acid 12V and 6V batteries as well as 12V lithium batteries. They claim "8 modes" in the manualbut I think this is a bit of over-marketing. For instance, one of the 8 is "Standby" which is essentially "Off".  Regardless, it will work with multiple battery types, and if that is useful to you, that is a good thing.
But I was evaluating how this charger would work for Lithium batteries and I found some things I didn't like. The manual claims an 8 step charging sequence... but it doesn't say anything about how it works differently, if at all, for a lithium battery. Perhaps the charger's lithium mode just skips the desulfation step and ends in a voltage appropriate for lithium batteries? There is no way to know. The manual also doesn't describe any way to reset the BMS on batteries that have that built in.
So... I rejected the NOCO and I did not buy one to try it.

tecMate OptiMate Lithium 4s 0.8A TM-471

User Guide
(about $60 on Amazon as of this writing)

The OptiMate Lithium comes with lots of great recommendations. At least 3 of the battery manufacturers recommend or resell OptiMate chargers: Antigravity, EarthX and Ballistic.
So I ordered one of these up and checked it out.

Sadly, I found the LEDs hard to understand. Even with this key from the manual it isn't perfectly clear:

Here is what the manual says about LED #5 and #6:
VOLTAGE RETENTION TEST: LED #5 flashing Delivery of current to the battery is interrupted for 12 hours* to allow the program to determine the battery's ability to retain charge. For batteries with a good state of health LED #5 (green) should continue to flash for the full 12 hours* period. Read the section NOTES ON TEST RESULTS on reasons for poor test results or how to test a battery that returns a good result but cannot deliver sufficient power once it is returned to service. 
MAINTENANCE CHARGE: LED #5 / 6 steady on For 30 minutes the circuit offers current to the battery within a safe 13,6V voltage limit whilst the result of the voltage retention test is displayed. If LED #6 (red) indicated the VOLTAGE RETENTION TEST will be repeated. A steady LED #5 (green) indicate the 30 minute float charge maintenance periods follow and alternate wih the 30 minute REST (no charging) periods until the battery is disconnected. The battery can draw current as required to support small loads and counter self-discharge.
Is that clear? It means that LED #6 will go solid green when the charging is completely done.
But note what the manual says about the "Voltage Retention Test", LED #5. It says this test lasts for 12 hours! And guess what... it wasn't true; when I charged my Antigravity battery (which wasn't badly discharged at 80%) the "Voltage Retention Test" alone went on for MORE THAN 24 HOURS (this is in addition to the time required to charge the battery before this). And note, this is a relatively low powered charger, at 0.8A, so it isn't particularly fast anyway.
Now, I really like the idea of this test. And obviously, you could just disconnect the charger before this test is completed and use it. But I was annoyed by the strange LEDs. This charger should have the LEDs all in a row like the other brand chargers, and a clear indication when the charging is DONE and then a clear indication the 24 hour charge retention test is happening. 

Also, while some Optimate chargers can reset the "over discharge protection circuit" on some batteries, it is not clear that this charger has that feature. It isn't mentioned in the manual but the website does say it has this feature. It would be nice to mention the feature in the manual if it is included in the device. I think it is probably in there...?

In summary, I wasn't thrilled with the OptiMate charger.

CTEK (56-926) LITHIUM

Manual
(about $80 on Amazon as of this writing)

Here is what came in the box:


The CTEK is a lithium battery charger only and charging steps are clearly described in the manual. There is also a linear array of LEDs on the charger that clearly show the progress of the charging.
Check out these two pages from the manual:



Perfectly clear and concise! So refreshing after the OptiMate manual. Note how it clearly shows how to reset the "over discharge  protection circuit" in a battery that needs that.

The unit itself is handsome enough. I do wish it was rubberized on the corners to protect it from drops and some rubber feet would be nice too. It does look like it will become scratched and worn over time. But note the nice and simple LEDs, the clear reset button, and the voltage and current rating right on the front.


Here is a closeup of the LEDs:


The manual page above clearly indicates which steps/LEDs indicate the battery is "READY TO USE" (step/LED 3) and "FULLY CHARGED" (step/LED 7). Tip to CTEK: This really should be printed right on the label, there is plenty of room! I may add a sticker to mine as a reminder.

So I tried the CTEK on my Shorai battery, and it worked fine. The battery was at about 85% charge when I started it, and when I went back a later it was fully charged. No problems and easy to understand.

Conclusion

My choice: The CTEK Lithium charger. It has the most clear manual and good LEDs. It clearly states that it can reset an "over-discharge protect circuit" and has a button for that feature. The manual clearly describes how it's steps work on the lithium battery, including the voltages used and how long the steps should take.

Friday, May 19, 2017

New Top Jaws for the Black & Decker Workmate 79-001 Type 2 (WM625)


So who's the guy in the Lotus Elan next to the Workmate? That is Ron Hickman, the designer of both the Lotus and the Workmate! You can read more about the history of the workmate here if you are curious.

The Black & Decker Workmate is a portable workbench/vice that has been sold in the millions around the world. If you are interested in these and do a bit of research, you find out the early ones are considered by many to be the best, as they have a pair of cast aluminum H frames that could be folded under the top to allow the workmate to be stored flat. Later models went to steel parts that were somewhat less sturdy, and certainly less cosmetically appealing.

In the USA, one of the more desirable models is the "79-001 Type 2". This model seems to be nearly the same as the WM625 version sold in the UK. (I've been told that the UK WM625 had an additional hole in each top jaw piece and that some of them lacked the "batten" on the bottom of each jaw that doubled the depth of the clamping surfaces.)

The "Bay Area Galoots" have done a type study of the various versions available in the USA.

And here is an early review from Popular Mechanics (Aug 1975):

Here is a picture of the one I purchased recently:

A common thing is to make a plywood top with a 2x4 screwed to the bottom. The 2x4 can be clamped in the Workmate jaws to be particularly sturdy. 

The top isn't in horrible condition for being 40 years old, but I'm considering making a new one.

So I took some time and sketched out the dimensions of the top. I thought these might save others some time, so here they are. Both halves of the top are the same.

Dimensions of the top and hole placements:

Detail of the edge bevels:


Tuesday, February 14, 2017

Stopping the Liftmaster 888LM MyQ Control Panel's Warning Beep

So I have this cool garage door opener, a Liftmaster 8500 with a MyQ 828LM Internet gateway, that can be controlled remotely over the Internet.
But it the 888LM MyQ Control Panel makes a horrendous warning beep when you close the door via Internet app:

video

It is just like a fire alarm! Really loud. I guess the idea is that if you are not home and you close the door remotely, they want to warn anyone nearby the door is going to close. So it blasts this warning beep for a full 10 seconds before closing and then continues to beep until the door is closed. I did it once at night and I was concerned I would wake the neighbors! (Note the beep doesn't happen if you use the regular garage door remote or the wall botton.)
Personally, I figure the other safeties that are built into the garage door (like the photo eyes) are enough protection. So I decided to find a way to disable the beeping. A bit of googling and I found many people complaining about the problem and I must thank Philbin Adamsworthy for the inspiration for this project.

On my door the warning beep comes from the wall mounted button, the 888LM, that operates the door from inside the garage:

There is a screw under the flip up button, I removed that and then you have to slide up the unit to remove it from a second screw that is hidden underneath:

There are wires attached to the back that need to be removed to to take the LM888 off of the wall:

There is a thin black cardboard insulating back on the unit, that is held in place by two posts on the back of the unit.

I lifted the cardboard from the bottom and then carefully pried the cardboard free from those posts with a small screwdriver:


Even after you remove the two screws for the wires, the circuit board is held in place at four points along the side of the plastic housing. I used a large screwdriver to lever the housing away from the circuit board at each of the four points and popped it free:


Next I lifted the top of the circuit board and carefully wiggled it free and slid it toward the top and up to remove it:


Flipping the circuit board over you can see the buttons that fit carefully into the cover. Note there are rubber buttons and a guide that can fall out of the housing. I was careful to note their original positions.


Here is the delicate part. I used a small screwdriver to carefully lever the top off of the speaker housing. If you put the screwdriver too far under the housing you will damage the speaker's internal board; the screwdriver needs to just barely go under the edge.

Underneath are two fine wires to the speaker. I snipped those.

And then I removed the speaker and discarded it!

When installing the board back into the housing I was careful the sensor fit into the plastic guide properly. This guide does come out of the housing, so you do want it positioned correctly:

The circuit board slides back into the housing and snaps back in. I was careful the LEDs and buttons lined up.

And then I replaced the cardboard, pushing it down over the two posts to attach it. And I replaced the screws, leaving them loose enough to reinstall the wires on the wall. Note the screws are marked for the wires, Red and White.

And that was that. I put it back up on the wall and the annoying warning beep was gone!

Sunday, November 13, 2016

The Garage Attic Retracting Stairway



We just finished building our garage. Probably the most interesting feature is the attic stairway.
Most people with attics have used those weak and narrow pull down folding or telescoping stairways. They are narrow and steep and not very strong. I wanted to be able to easily use the attic storage area so I wanted a really good stairway.

It is important to understand that attics need to be designed properly to support the weight. From the beginning of the garage design this stairway has been planned for. I discussed it with the truss engineer and we made sure to design for the truss spacing, the weight and the point loads. Additionally, the whole system has been designed to account for the various loads and weights on all of the components.

I did lots of drawing to design and build the stairway and components but this one sketch illustrates the basic function:


And here is a video of the stairway in action!


Details
The counterweight:
 



The pivot:


The cane bolt:
 




The pulley system:


The stair to cable attachment:


My thanks to Jorge Tafoya of Tafoya Construction in San Diego for his help with this project. I couldn't have done it without him: