ks1g

I'm looking at the 12.8V 6.6 AH LiFePO4 battery in a water bottle. Anyone have experience with it? How well-made are the connections, cables? Is there a better charger than the one they sell? How quickly does the peak voltage drop off? (15.6V sounds high - at 3.8V max/cell = 15.2 for a 4S2P battery, and the cell spec sheet says 3.65V/cell = 14.6V max.

My application is a little different - powering a 30W VHF RF amplifier for a bike-mobile ham radio station. The water bottle packaging is ideal for my road bike (water-protected, no rack, seat post rack, or panniers) and the weight is a big improvement vs. SLA. I am concerned about the peak voltage - >15V is above the amplifier's ratings.

Also considering their much cheaper 12V NiMH battery also in a bike water bottle No over-voltage issues, and I have a charger, but not as much capacity and the max current (polyfuse) is close to what the amp will draw if I forget and drive it at full power.

Comments on experience with batteryspace, their LiFePO4 pack and charger in particular are appreciated. I've also considered building my own pack; after buying the cells, heat shrink, and charge control board and stuffing it into my own bottle (or other packaging), I think I'm better off buying it assembled from them.

Looigi

A bit OT, but I wonder why you want/need 30W VHF?

ks1g

To improve communications support for an upcoming century ride. I've done this for several years with a local ham radio club using a 5W handheld radio (mounted to handlebars - RAM Mounts rule!) and a large external antenna (flagpole "j-pole" and starting last year, a Larsen HW-1 that doesn't need a big metal ground plane to work well). Sections of the route are marginal to out of comms range at this low power and the antennas I can put on my bike. The SAG vehicle radios usually run 25-50W with much larger antennas working off the vehicle's ground plane = MUCH better performance. Our group added APRS a few years ago and I'd like that to be reliable for me as well.

I ride the full century route and with 5,500+ ft of climbing, I can't lug around a larger mobile radio and SLA battery, and I won't mount on my road bike a rack & case/pannier to hold it all (my commuter is a different story). I need to go as small and lightweight as I reasonably can go. I acquired a small 30W amplifier I can mount on the bike for this event; the LiFePO4 battery solves the problem of how to power it without a huge weight penalty. Tweaking the set up on my daily commute got as much as I am likely to get without more power, and tests on my commuter bike with a 7AH SLA battery show I can have comms almost as reliable as the vehicle stations. I don't even need the full 30W - I can run less than that and save battery power to get more operating time.

I know this is not absolutely necessary - we've done workarounds in prior years and the drop-outs are more an annoyance than a problem. If I was simply patrolling a portion of the route and didn't have to contend with the full distance and climbs, I'd use the commuter and SLA battery and be done with it. But given the opportunity to come up with a workable solution.....

Looigi

Hmmm. IMO, a ground plane doesn't offer much advantage when you can use a vertical 1/2 wave antenna, like a j-pole, which will have gain over a 1/4 wave ground plane antenna, especially if elevated a bit...1/4 wave or more from the bike and and rider Think vertical dipole. If UHF, a collinear would be even better (too long @ 2m). Better would be a directional antenna but setting that up on a bike and rotating it would be an "interesting" challenge, especially if done while riding. :-)

Anyway, good luck with that aux power and battery setup.

ks1g

Thanks. All the experience says that - the 1/2-wave designs should outperform a 1/4 wave (tried it and they do) and should be independent of whatever ground 20-25# of steel and aluminum provides. I've tested the HW-1 on both my carbon fibre road bike (with and without counterpoise wires on the seat stays) and on my steel frame commuter (+ an aluminum rack and a separate aluminum plate "stinger" behind the rack for the antenna mount) and surprisingly, the "doesn't need a ground plane" antenna performed noticably better on the commuter. The flagpole j-pole & their relatives seem less sensitive to which bike they're on. Getting more height is tough - the fiberglass flagpoles get really whippy beyond 5-6', and I don't like it all being supported by the clamping force between the rear QR skewer and dropout.

If I was riding a tandem, I could put the stoker in charge of "beam steering" - they aren't using their hands for much anyway.

I was checking prices a bit more on batteryspace and noticed a curiosity. I can buy the battery+bottle for less than what I think the same pack is sold by itself (with cig. lighter connector); I can buy the battery+bottle, a charger, a charger cable to aligator clamps adaptor, and the other half of their trail tech connector cable for less than their package deal (battery, bottle, charger, trail tech cable). May just pull the trigger and do it - I can use the battery for other portable ops and maybe even for powering winter commuting lights.

Thyce

I have that very battery pack. I bought it when they first came out to replace a very heavy SLA battery. Mine discharges at 12.8V. It goes higher during charging. I use the 1.5 Amp charger that they sell with the battery to charge at home. When I am on a bike trip I charge the battery with a solar panel on my BOB trailer and I am very careful what else I plug in while it is charging. Only one of my devices is rated for voltages as high as 15.2 Volts. I like using solar charging because it can charge while I am riding, just like a hub generator but without the extra drag, but most importantly it also charges while I am stopped. I use it to power my head light, tent light and tail light. I also use it to recharge my cell phone, GPS and XM radio. It is a great light weight battery with lots of power. You can toss it in a pack or place it in a water bottle cage. It is much safer and way more ecological than Li-Ion batteries. The price has come down since I purchased mine and I have not had any problems with mine. I have thought many times about getting my license, then I could use the battery to power a bike-mobile ham radio also. Please let us know what battery you settle on.

dougmc

I wonder if you can find a nice DC-to-DC converter that will take in 12-15 volts and emit somewhere between 12.0 to 13.8 volts without being too noisy that can handle 4 amps or so?

You could also contact the manufacturer of your amp and see if it really can't handle 15 volts. Many things can handle higher voltages with no problem -- but many cannot, so don't risk it.

UberGeek

Stupid question for the OP: Why do you need a VHF amp? Just use a mobile rig. Handy + Interconnects + Amp would weigh about the same as a mobile radio would (Like a Yaesu FT-2500, or 2600; or a Kenwood Tm-241).

You can back down the power as needed, and stretch the life of the battery. Then, plunk a solar panel on the bike as well, to trickle the battery (It's what I did).

Richard Cranium

And then again haven't cheap cell phones knocked a little luster off of radio-telephones?

Not that I know anything - but just wondering do "portable repeaters" exist for ARS? Could a club create their own 2-meter "cell" area by installing moveable repeaters? Just wondering.........

UberGeek

Sometimes. Sometimes, having everyone on a radio frequency makes more sense. Like in security situations, or when providing a group service like this.

They do make them. Might even be what he's trying to hit. But, most base repeaters have the range to service large areas.

Plus, coordinating a repeater pair can be a trial at times.

dougmc

2 meter repeaters generally have a channel separation of only 600 KHz -- pretty small. This generally requires a duplexer that's pretty good sized and tuned to the specific frequencies used to keep the repeater's transmitter from swamping (desensing) its receiver. This generally means that a good two meter repeater isn't small or cheap. (Though if it recorded the signal and then replayed it when it was done -- that would work fine. It's less convenient, however.)

In the 70 cm band, the usual separation is 5 MHz if I recall correctly -- that's easier to deal with. Not trivial, but easier.

Many portable radios (both hand-held and mobile (for car use)) that do both the 70 cm and 2 m bands can repeat between the two -- listen on 2 m and repeat on 70 cm or vice versa -- all this in a small, inexpensive package. But in order to use this, everybody would have to have 2m/70cm radios, which are more rare than just 2 m radios.

Of course, I'm not sure what the benefit is to having so much more power than everybody else unless you want to be "the hub" that everybody goes through. People could hear you, but you couldn't hear them.

Since this ride is a century ... 100 miles of range is a long ways. More than you're going to reliably get with any VHF gear. A good repeater with an antenna at the top of a mountain in the middle would make it work, barely -- and such repeaters are rare. More power isn't going to fix this -- line of site is the issue. I imagine you're already aware of this, of course.

Thyce

If you want to use a 12 volt mobile radio that is meant for use in car you would be OK with a LiFePO4 battery because a typical automobile charging voltage should range anywhere from 13.6 to 14.4 with some cars known to charge as high as 15.6 volts. A typical car battery is not 12.0 volts but actually 12.6 volts because it has six cells, each producing about 2.1 volts with a total output voltage of about 12.6 volts when it is fully charged and has been at rest for at least 2 hours at 70 deg F.