Off Grid Ham: Learning From Off Grid Mistakes, 2

This article comes from Chris Warren at Off Grid Ham – Learning From Off Grid Mistakes, Part 2.

I wasn’t planning a “part 2”. learning from off grid mistakes

Last May’s article about off grid mistakes received a surprising amount of attention. Many months later, it’s still a very popular piece. As a follow up, I thought it would be a good idea to revisit the issue and go over a few points that were not discussed last time. I encourage readers to send in questions and comments because most of the articles that appear on Off Grid Ham are derived from reader input. learning from off grid mistakes

Mistake 1: Mismatched batteries.

Batteries are very exclusive. They don’t like other types of batteries. Just because two batteries are of the same voltage, and maybe even the same capacity, doesn’t mean they play well together. If you are using multiple batteries, they should be the same make and model, and roughly the same age. Most batteries will have a date code on the outer casing for determining age. learning from off grid mistakes

When I went shopping to replace my large storage batteries two years ago, I brought my battery analyzer with me to the store. They had a huge pallet of deep cycle batteries, so I had plenty to choose from. I dug through the pile and picked out a few that were manufactured within a month of each other. From that cohort, I tested each until I found a few batteries that had the same or very close to the same internal resistance. That was the matched set I ultimately bought and took home. Yeah, I must have looked a little weird picking through batteries and running tests, but I got what I wanted. learning from off grid mistakes

When you mix dissimilar batteries or batteries of different ages, the weak one will pull down the strong one. Always Install and remove your batteries as a set. If you must mix dissimilar batteries, wire a battery combiner between them.

Mistake 2: Mismatched solar panels.

This mistake needs some clarification. You should not mix/combine solar panels of differing voltages at any time. Solar panels that produce the same voltage but not the same wattage can be used together, but only if they are wired in parallel. Solar panels are often wired in series to increase efficiency and make better use of MPPT solar controllers. This works only if all the panels in the series are the same voltage and wattage.

If you wire solar panels of the same voltage but different wattage together in series, you will not damage anything or create an unsafe condition. What will happen is that the total power output of the system will not exceed the capacity of the smallest panel. For example, you have one 100 watt panel and one 50 watt panel wired in series. It might seem reasonable to think you’ve got a total of 150 watts capacity. Sorry, but you’ll never get more than 74 watts out of this system.

The reason why is fairly simple: Kirchoff’s Law states that current will always be the same at all points (nodes) in a series circuit. A 100 watt panel will produce about 5.75 amps. A 50 watt panel maxes out around 2.85 amps. Our 12 volt example panels below are wired in series for a system total of 24 volts (in reality, it would be closer to 26 volts).

Since Kirchoff says the current is the same at all points in the series, and the 50 watt panel will never exceed 2.85 amps output under any conditions, the system total is limited to 2.85 amps. Doing some basic math, 2.85 amps x 26 volts= 74 watts. These numbers will vary due to differences between loaded and open voltages, what specifications are used for your calculations, etc., but this gets us pretty close. Think of it like a convoy of ships: The entire convoy cannot go any faster than the slowest ship.

learning from off grid mistakes


Mistake 3: Using automotive batteries.

If someone gives you a car battery, or a car battery is all you have (such as in a SHTF situation), then certainly go with it for your off grid ham radio power needs. But no thoughtful ham would purposely choose a car battery.

Car batteries are designed to deliver a large burst of current over a short period of time, which is needed to start a car. Off grid hams need batteries that can deliver smaller, steady amounts of current over a long period of time. Using a car battery will not hurt your equipment and is not a safety hazard, but you will not see the the level of performance that a correct battery would provide, and the car battery will have a shorter service life too.

Mistake 4: Using automotive “jump boxes”.

Those inexpensive portable battery boxes made for jump-starting cars seem like an easy, ready made power system for ham radio. They are not recommended for ham radio use for the same reason as standard car batteries. They are made for a short power burst, not for a lighter, continuous load. Some hams do use them with modest success, especially for QRP, but they’re not a serious way to power your radio.

Mistake 5: Buying the best, most expensive gear available.

Just as buying cheap junk because it’s cheap is a mistake, so too is insisting on only “the best”. More expensive does not necessarily mean a device has better build quality or will last longer than a less expensive device of the same type. In many cases it only means you get more cool switches and pretty lights. If you cannot justify the extra cost with some clear purpose or practical benefit, buying “the best” is a journey of vanity.

In my experience, mid-grade equipment has always given me the most bang for the buck. Early in my off grid career I spent over $500 on an ExcelTech inverter. They are made in USA. They are practically indestructible. The American military and US embassies around the world use them. They’re the Rolls Royce of inverters. I didn’t know it at the time, but it was unnecessary overkill. As nice as my ExcelTech is, my Samlex inverter is just as suitable for my application. It cost half as much as the ExcelTech and gives excellent performance. I still use both inverters, but if I were doing this over I’d get two Samlexes and spend the extra money on other useful upgrades.

Never buy any piece of off grid amateur radio equipment based solely on high or low price point…(continues)

Off Grid Ham: When Your Batteries Are Boiling

Chris at Off Grid Ham has an article up, talking about the danger/effect of heat on your batteries. When Your Batteries Are Boiling

Most of the USA is going through a blazing hot summer! Here in the upper Midwest it’s been over 90F/32C every day for almost two weeks. As I write this it’s 87F/31C in Buffalo, New York. That doesn’t sound too bad until you consider that it’s past sundown there, and the average daily July high for Buffalo is only 80F/27C. Most off grid amateurs fuss about battery temperature when it’s cold. Have you ever thought about what heat does to batteries? If you haven’t you should.

The chemistry of heat. battery temperature

How heat effects batteries varies greatly depending on the type of battery, how it is used, and the current going into/out of the battery. Battery chemistry, which is quite complex, is made even more complex by changes in temperature.

In addition to ambient heat, batteries themselves generate heat when they are charged or discharged. So, we have two factors at play. The radio amateur has only limited control over these two factors. Managing heat, to the extent that you can, will give your batteries better performance and a longer service life. battery temperature

Lithium batteries. battery temperature

Few things have benefitted amateur radio like lithium batteries. They are so much lighter and more powerful than their predecessors that the step forward in technology can plausibly be compared to when the transistor replaced the vacuum tube.

But like their ancestors, extreme temperatures effect lithium batteries. Once a lithium reaches 113F/45C, it should not be charged because excessive gas buildup can cause a cell to bulge. Lithiums can be discharged at up to 140F/60C but will lose capacity as they reach the upper limit of their operating range. There is also evidence that the higher the beginning state of charge, the more capacity will be lost as the battery heats up.

All larger lithium batteries have an on-board battery management system (BMS) that controls charging and cell balancing. Usually these electronics will reduce the current or not let you charge or discharge at all outside of acceptable temperature parameters. The high limits may seem generous, but do not underestimate them. Leaving a battery in a car on a hot summer day can easily push it beyond 113F/60C. If you are operating outdoors on a hot day and connect a solar panel to your lithium battery, the ambient temperature plus heat generated by the charge has the potential to exceed established temperature limits. The bottom line is, if your lithium batteries do not already have temperature-compensating circuitry, then you’ll have to monitor battery heat yourself.

AGM/Sealed batteries.

AGM, sealed lead acid, and gel cell batteries are cousins of each other and share similar characteristics. They’re very popular with amateurs due to their relatively low cost and ease of use. battery temperature

The top operating limit for AGM/SLA/gel batteries is 120F/49C. Like lithiums, AGM batteries will have reduced capacity at high temperatures and can also bulge/expand out. Thermal runaway is rare but possible. Overcharging generates heat and AGM batteries are especially sensitive to overcharging, so radio amateurs should be attentive when charging these batteries. A “smart charger” with a temperature probe would be ideal.

AGM-class batteries should not be discharged to less than 50% full. This presents a problem because they lose capacity at high temperatures. So if you have a battery that already has diminished capacity because it is hot, and then have to observe a 50% floor, that doesn’t leave much useful power for your equipment. At the same time, you will have to reduce charge current to avoid further overheating. The end result of all of this is a battery that will need to be charged more often and for longer periods. In a hot environment your AGM battery will for all practical purposes have less than half of its rated capacity. Lastly, long term exposure to heat will cut the service life of an AGM battery by half for every 15F rise above 77F (source)…

Click here to continue reading at Off Grid Ham.

Organic Prepper: How to Deal with Rolling Blackouts: Notes from South Africa

In this article from the Organic Prepper, a South African writes notes about dealing with rolling blackouts and alternate forms of power like generators and solar power. It has some good information on battery cycles and reducing your loads. While I haven’t seen as much damage to equipment from power outages as the author of the article, it does happen. Some power utilities will help you put in a whole house surge suppressor. Our local utility will put one in at the meter for around $6 per month charge.

Living in South Africa we have had our share of rolling blackouts nationally. The cause: nefarious activities. The result being us forced to find ways to ensure we are not affected as badly.

The problem is better now, but it has highlighted that it is not just a South African problem, but in actual fact a Western world problem. We all are totally reliant on a massive aging infrastructure that can come tumbling down like a house of cards, with or without help.

Another problem is the cost to keep the national system operational. In some areas, it is not a priority to resolve the regular failures.

For getting started with backup power, remember that NEEDs vs WANTs –  a huge price difference.

  • UPSs – with like 2 up to 8 100ah batteries. Good for a number of hours depending on use – most cost-effective solution
  • Generators – works for some, but cheap ones cost more as they damage some electrical appliances over time.
  • Solar inverters and panels – power failures, what is that? And you save a lot of money afterward IF YOU DO IT RIGHT.

What is also good to know, when the power goes off, switch off your distribution board, leaving just the light plugs on. When the power comes back on, lights come on, wait a few minutes for the grid to stabilize, before switching things on. We have lost computers, internet modes, freezers/fridges, alarm systems etc, damaged when the grid goes off and back comes on. UPS’es have the best protection for this.

How does one solve the issues from frequent blackouts?

Here are some pertinent notes from my own experience.

  • Older fridges/freezers have a huge start-up current, necessitating a bigger inverter and they use a lot of kWh over 24 hours. Upgrade them to an A++ or even A+++ model, as soon as you can. It will save you on utilities and can be powered longer on batteries.
  • Lights: obviously CFL and / or LED, and not cheap LEDs. They are cheap for a reason. Test the wattage, it may be more than the claimed wattage “saving” you nothing. Check the claims lumens.
  • Putting lights on solar is not a “savings”. It is actually an increase in cost for batteries are more expensive per kWh than utility power costs per kWh because lights are use when there is no solar power. So switch to the best lumens for the lowest watts, and switch the light off when not in use, biggest saving ever.
  • Stove/oven/kettle – entire kitchen – on solar power is doable, but expensive. Utilities are cheaper. Kettle take few minutes to boil, microwave also a few minutes, why spend more on inverter and batteries to power them. Use gas. Gas per unit of power may not be cheaper than utilities. Check what you are paying for each.
    Maximum savings are: Switch off at the wall, not in standby, for all the standby power adds up to a lot of power paid for, yet not used.
  • When all the occupants of a house are asleep, say 11pm – 5am – how much power is used during that time? Excluding alarms and outside lights – which have a motion sensor to switch on. Figure this out and find places to cut.

The Rules of Running Backup Power Efficiently

Right, now that you have a few notes to consider, here are the rules that we have found important when using backup power like a generator.

The very first rule: NEEDs vs WANTs

Needs are much cheaper than wants, like you WANT to power your entire house during a power failure, or do you just NEED to power very selected devices like a fridge, lights, cell phone chargers?

The second rule: Know your loads and runtimes and match the batteries to that…

Click here to continue reading at the Organic Prepper.

American Partisan: Making the “Lightning”

JC Dodge has an article up at American Partisan about keeping your batteries for various important devices charged up when you can’t just plug in an AC adapter –Making The “Lightning” For Your Force Multipliers.

Making The “Lightning” For Your Force Multipliers
Winter ruckin'16

Charging the large fold up solar unit on top of my pack in the field.

Since the 90’s, I’ve carried a small solar charger for AA batteries in my kit. This was for keeping certain devices I had, like flashlights and PVS-7 NOD’s, operating in the field when there was no chance to get new batteries or charge the rechargeables I had on household 110 system. I started using CR123 batteries in the early 2000’s when I bought an IR laser that used a single 123 battery, and shortly after, I upgraded my weapons light to a two celled, CR123 powered, Surefire.

Solar post07

The DBAL and Surefire light on this M1A Socom both use CR123 batteries


The use of CR123 batteries put a gap in my preps because, at that time, no one was selling 123 rechargeables. Oh well, guess when they’re done, the IR laser and Surefire is done, right? I made sure I bought a lot of CR123’s for storage. Back in 2013 I found CR123 rechargeables that were made by a company called Tenergy, and I’ve been using them ever since. The caveat to using Tenergy 123’s is that their charge is a little higher than a normal CR123’s 3.2 Volts and two together will burn out a standard Surefire bulb immediately upon hitting the switch (ask me how I know…). No problem, I also ordered some programmable bulbs for my lights and I was back in business.

Last year I decided to get with the times and see if I could come up with alternative charging means to recharge not only my AA’s and CR123’s, but also my 9 Volt batteries for my laser range finder and heat (game) detector. My FLIR 24 which has an internal battery and recharges via micro USB also needed a way to get a boost in the field…

Click here to read the rest of the story at American Partisan.