Selecting the right battery chemistry is just the beginning. We do much more to make custom battery packs for different use cases to meet specific customer requirements.

But first, a little background. Battery solutions are complicated. We aren’t talking about the AA you pop into the TV remote. Nor the lead-acid ones in your car. (Using lead-acid batteries for solar is costly, dangerous, and outdated, so don’t do it.)

The ones in your smartphones and laptops are purpose-built lithium batteries. Yet, they exist because the Apples and Samsungs of the world have invested billions into designing and producing them for the global, lucrative consumer electronics market.

Developing any battery solution is a lengthy and dangerous process💥 that costs millions. They require highly specialized expertise and dedicated facilities. That leaves the rest of the world needing battery solutions in the Stone Age. *caveman grunt*

The frustrating world of battery can’t-do’s

When you talk to most battery industry veterans, you get more “no, can’t do” than “yes, sure!”:

Can you mix cells of different battery chemistries cos it’s such a waste to toss out my lead-acid ones, but I want to upgrade to lithium? “No, can’t do.”
Can you combine cells of different ages so that I can expand my capacity without replacing a slightly aged pack? “No, can’t do.”
Can you make a battery pack that lasts much longer than what’s typically available? “Theoretically, maybe. Practically, we don’t wanna do it.”

If you’re lucky enough to come across a Bronze Age solution, you have a slightly more advanced battery management system (BMS) sitting on top of your pack to show you a few things about the cells. But it still doesn’t do much to proactively manage the battery solution or adapt the battery behaviors to meet specific needs.

But the truth is that all of the above can be done and have been done. In two places: our own motorhome and the military — until now. We’re bringing advanced battery solutions into the custom off-grid solar power systems we design and build for our clients.

What “Yes, can do” battery solutions look like:

Ok, so what can a “can-do” battery solution do? Here are some examples.

An ultra-long-endurance battery pack

Lead-acid batteries last 5 years if you’re lucky. Lithium cobalt cells can go for about 10 years if you baby them. But we can make battery packs with a 15-year lifespan (or maybe longer) with the right chemistry and some BMS magic.

The picture below is a work-in-progress of an ultra-high-endurance battery pack. We source special high-endurance lithium iron phosphate (LFP) cells and perform a "top balancing" process to enhance the pack’s longevity.

We trickle-charge all the cells to a uniform level close to the maximum charge allowed before wiring them into a pack. The process stabilizes the chemistry and takes a few days (that’s why commercial pack manufacturers don’t do this). Plus, we program the charge and discharge levels in the BMS to keep them between 20% and 80% of the maximum.

What’s the catch? Before we built this solution, we discussed the tradeoffs with the client. By not having 40% of the battery capacity available (unless we change the BMS setting, which we can do in the future), they’ll get less power during nighttime but have a solution that won’t require maintenance for a long time.

Since the main purpose of building the system is to add resiliency during outages (and the client doesn’t want to worry about the battery for as long as possible), they’re ok with switching to the grid when the battery runs out.

A phased upgrade to lithium batteries

This client has an ailing lead acid battery bank. After we topped off the cells and adjusted the settings to increase its longevity, it had a year or two of life left. It didn't have enough capacity to meet the client’s needs, and he was in a conundrum. He had two equally suboptimal options if he were to follow conventional wisdom (which says you can’t mix battery chemistries):

Sink another $5k into a new batch of lead-acid batteries and perpetuate the cycle of using an expensive, high-maintenance, and short-lifespan chemistry.
Bite the bullet, upgrade to LFP chemistry, and toss out the lead-acid batteries, on which he recently spent $5k a year ago. Ouch.

But he can have his cake and eat it too with some software magic, which makes the old lead-acid batteries play nice with new lithium-ion batteries. Based on that approach, we designed a phased upgrade plan for him.

First, we combine the lead-acid batteries with one high-endurance LFP pack to increase the system’s storage capacity. We also add a couple of new solar charge controllers (SCCs) to augment power production. The upgraded system will allow us to accurately measure his usage pattern to determine the additional battery capacity he needs.

Then, we’ll likely add another LFP battery to the system, bringing it to one lead-acid battery pack and two LFP packs. Finally, when the lead-acid batteries run their course, we replace them with an LFP pack to take the solution to its ideal state.

A battery for high surge power and prolonged draw

Different battery chemistries have different characteristics. Some are 100m sprinters, while others are marathoners. Traditional battery technology doesn’t let you mix them in the same pack to get the best of both worlds.

Packs ideal for high surge power (e.g., to start a monster power tool) don’t run for long, while those that can go for hours have trouble jolting a chainsaw into action (unless you buy a large pack, which means a lot of excess capacity when you aren’t starting a monster power tool).

But what if you can mix battery chemistry to achieve the exact characteristics you need for your specific use case? A little software wizardry can make that happen, too.

When we design a mobile solar generator solution for a client to run his workshop while at home and power tools while on the go, we mix lithium cobalt cells with a more aggressive discharging curve (i.e., higher output for a shorter period) with those that discharge at a more sustained manner.

The result is a pack that can jolt some heavy-duty power tools into action and keep them running without over-dimensioning battery capacity, which is heavy (bad for mobility!) and expensive.

What do you want your solar and battery solutions to do for you?

There’s so much more you can do with a custom battery pack (and it will still cost you less and last way longer than old-school lead-acid batteries). When you talk to us, toss the conventional thinking aside and ask, “What if my solar power system could…” (no, we can’t make it dance.)

Get in touch and explore what’s possible.

Battery Wizarding: A Peak Under the Hood