LiPo battery protector - "LiPo Guard"

[KevinMc]

Like many I've started taking advantage of the longer runs and small size offerd by LiPo batteries in my subs. Their only downfall is they can be permanently damaged if discharged too far, so last summer I came up with a circuit that would let me easily monitor the voltage in my LiPos and give me an unmistakable warning when it was time end the patrol and return for a recharge. The idea was so well received I decided to turn it into a follow-on product to my ADF. So here it is - the LiPo Guard.



Features:
-Intuitive four LED “gas gauge” gives an instant indication of battery type (cell count) and charge level.
-When used in conjunction with a “missing pulse detector” failsafe device (ADF recommended) the LiPo Guard helps protect your batteries from damage due to over-discharge. Low battery warning is indicated by a forced surfacing after which you will not be able to dive. If you’re stuck on the surface, it’s time to come back for a recharge!
-No setup required. LiPo Guard automatically configures for two cell (2S) and three cell (3S) Lithium Polymer and Lithium Ion batteries. Low voltage warning is indicated by triggering your ballast failsafe.
-LiPo Guard maintains galvanic isolation between the battery connection and the servo connections so noise-causing ground loops are not introduced.
-LiPo Guard can also be used with dynamic diving “pool” subs- Insert the LiPo Guard between the receiver and the ESC and your throttle will be disabled when it’s time for a recharge. (Not recommend for running beyond the reach of a retrieval net.)

The LiPo Guard will be available very soon through Caswell.

[Slats]

Kevin,

that is a very nice device.

Hope this doesn't sound dumb, but if you run fairly large scale subs like I do, does LIPOs make sense? I am pretty old school on electronics and use either SLAs wet on big boats and NiMH packs dry on medium size ones. I know you get longer run times and lower weight / size, but I am concerned about LIPO charging etc.

Best

John

[KevinMc]

Hi John,

It most certainly is not a dumb question! And I would maintain that for some situation LiPo's on larger subs are quite a sensible solution. Last summer I not only built up a 1/144 KILO (for which LiPo's are practially the only solution) but I also converted over my 1.6m 1/96 OSCAR II from SLA to LiPo. I've gone through several SLA configurations with the OSCAR, none of which I've really been happy with. The first config used two 4Ah 6V SLAs, one front and one aft of the WTC. The problem with this was that the aft battery really pulled the back end down, so I swapped out the two cells for a single 12V SLA up front of the WTC. While better for balance, it had only a fraction of the capacity of the original configuration (4Ah down to 1Ah) but this was all I could fit in the available battery volume. (Long story, but for such a big hull I actually don't have much waste-space for batteries.) Enter the LiPo- I now have two 1.9Ah 3S LiPo's paralleled in a 2.5" battery cylinder mounted to the front cap of my WTC 3.5-2. This gives me all the capacity of my original setup (if you count efficiency gains) at a fraction of the original volume and weight. While you won't get LiPo's as cheaply as an SLA, and you do have to treat them with respect, there are benefits to be had in larger subs as well as small subs. By eliminating the weight and volume of the SLA, you have a greater number of options on where to locate the batteries. Of course the weight that was you battery now needs to be replaced by lead, but you can do so by placing that in the most sensible place, and potentially use less total weight resulting in the need for less foam to compensate... I could go on, but I think you'll get the idea.

As for the "difficulities" in charging, it's all in the charging system. You need to have a charger that's designed for LiPos, and preferably also a balancing circuit. (Some chargers integrate these two features. Mine doesn't, it's a plug-in affair that I picked up for about $30.) Make sure you use the correct charger and don't over dis-charge them and LiPos can serve you well.

KMc

[He Who Shall Not Be Named]

I want to endorse and expand on what Kevin's said about the flexibility offered by the high power density Lithium-polymer batteries:

The new line of very small SubDriver's I'm currently working up would be impossible without them -- there is just not any room for compensating foam for batteries with a low capacity/weight ratio; as the power density of the new batteries is so much higher I can now cram in a Lithium-polymer battery into a space that will displace just about its own weight of water; high-capacity batteries possessing a specific gravity a bit over 1. That's incredible!

The one killer characteristic of the Li-Po battery is the need to provided it a monitoring-disabling circuit to shut down (or limit) current draw once the batteries critical voltage is reached -- something that's built into the mass marketed ESC's for aircraft and cars, but not, until Kevin's introduction of his battery protection circuit, available to we submarine Driver's. Now, with Kevin's device in hand to protect these batteries, there's no reason not to use Li-Po batteries in our r/c model submarines.

Lithium-Polymer (and the kissing cousin, Lithium-ion) batteries are the way to go, be it a large r/c submarine or small. And with Detroit on the march to improve the performance and lower the cost of these type batteries, we will see this technology on the street for many years to come; and the product --driven by the needs of the worlds car buyers -- will continue to improve in performance even as the cost of the battery drops; something made in the millions becomes cheaper as efficiency in production techniques are applied, i.e. the unit price goes down.

Can you imagine the deals to be had as Li-Po battery producers, currently making these things for Detroit, start selling 'seconds' to the hobby industry? I can. I'll settle for a reduced capacity factory reject Li-Po battery bought at a significant discount. You listening, Mike?

I've switched over to Lithium-polymer and Lithium-ion batteries. So should you!

Welcome to the 21st Century, gentlemen!



David,

[Slats]

Thanks guys fantastic response.

John

[SteveJ]

Kevin

Another dumb question. Will your lipo guard work with the 2 battery setup recommended by DM for the Seaview?

Stephen

[He Who Shall Not Be Named]

Kevin

Another dumb question. Will your lipo guard work with the 2 battery setup recommended by DM for the Seaview?

Stephen

Yup. The circuit reads the two parallel wired batteries as a single, very high capacity 7.4-volt battery.

David,

[SteveJ]

Any idea when they will be available? I have seen similar products but they appear to be for aircraft with a forward throttle only.

Stephen

[He Who Shall Not Be Named]

Any idea when they will be available? I have seen similar products but they appear to be for aircraft with a forward throttle only.

Stephen

Those devices are either now or soon will be in the catalog.

Buy American!

(Whoop's ... Kevin's one of them stink'n Canadian's ... never mind)

David,

[Kazzer]

Those devices are either now or soon will be in the catalog.

Buy American!

(Whoop's ... Kevin's one of them stink'n Canadian's ... never mind)

David,

Just watch it Merriman! I'm one of those Canadian's too! :)

As for buying American Lipo's what a joke guys! My next door neighbor in Newark NY is ULTRALIFE Corp. I phoned them and asked them to supply me with LiPo batteries, and they told me all theirs were made in 'yes - you guessed it! China'. No one it this country makes them. We're all too damned busy getting $6 an hour jobs in Walmart and McDonalds to want to get into anything hi-tech. We import $700 billion a year from China and sell them $60 billionCensoredCensored:mad: Anyhow, -------------

If you let me know what exact sizes we need for the mini Sub-drivers & models, I'll try to get a battery made specifically. I can obtain a LARGE selection of sizes and voltages, so give me some feedback guys. And they will be Chinese!

[He Who Shall Not Be Named]

Just watch it Merriman! I'm one of those Canadian's too! :)

As for buying American Lipo's what a joke guys! My next door neighbor in Newark NY is ULTRALIFE Corp. I phoned them and asked them to supply me with LiPo batteries, and they told me all theirs were made in 'yes - you guessed it! China'. No one it this country makes them. We're all too damned busy getting $6 an hour jobs in Walmart and McDonalds to want to get into anything hi-tech. We import $700 billion a year from China and sell them $60 billionCensoredCensored:mad: Anyhow, -------------

If you let me know what exact sizes we need for the mini Sub-drivers & models, I'll try to get a battery made specifically. I can obtain a LARGE selection of sizes and voltages, so give me some feedback guys. And they will be Chinese!

(that scratching sound you hear is me trying to scurry for cover under the carpet).

Great, Mike. The only 'custom' Li-Po's we need to add to the catalog are batteries for our upcoming line of 1.25 SubDriver's.

Make 'em this size: 2.75" X 1" X .5", 2-cell (7.4-volt), with small gauge, short, power leads terminating in a two-pin Futaba J connector. Pink with polka-dots. And a ribbon ... I want each tied up with a pretty, pretty ribbon!

... And I want them NOW!

At this size the battery would have a nominal capacity of 800 mAh -- plenty for those tiny little subs. If we need more capacity we can put them back-to-back in the cylinder where there's room (like the TYPHOON, KURSK, and the Trumpeter GATO).

You have a fine selection of Li-Po's otherwise.

David,

[toppack]

Pink with polka-dots. And a ribbon ... I want each tied up with a pretty, pretty ribbon!

... And I want them NOW!

David,

Mike,
I think he's puttin' Vodka in his Peanuts, Again! :D LOL :D

[KevinMc]

Hi John,

I dunno if a side-by-side comparison will shed further light on why I chose to make the switch, but I'll have a go at illustrating the difference it made for me. The photo below shows three sets of batteries. The big SLAs in the rear are the original power source I was running the OSCAR II on - 2X 6V 7Ah (wired in series for 12V, 7Ah.) Each weighs in at 1200g. I've since replaced them with the LiPo's off to the right, 2x 11.1V 1.9Ah (wired in parallel for ~12V 3.8Ah.) These weigh 140g each, a little more than 1/10 the weight of the SLAs. Based on these capacity numbers I'm at a little better than half the capacity of the SLAs, but for the difference in final weight I'd argue that I'm far ahead. (I don't think I ever flattened the SLAs, so arguably I had more capacity than necessary.)

The last cell in the photo is just for David. It measures 1/2" x 5/8" x 1.25", and has a short Futaba connector on it. It's too darn small for polka dots, there's no way I'm gonna paint 'em pink, and it only has 210mAh of capacity, but it does have a pretty, pretty bow on it. :eek: :eek: :eek:

[SteveJ]

Hey Mike when are the LiPo Guards going to be listed on the web site??

Steve

[Kazzer]

Hey Mike when are the LiPo Guards going to be listed on the web site??

Steve

They are now online!

LIPOGUARD