which battery chemistry is best for solar charging?

Batteries, Chargers, and Battery Management Systems.
Heynow999   10 mW

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which battery chemistry is best for solar charging?

Post by Heynow999 » May 24 2013 5:53pm

The idea I am playing around with is a solar powered battery pack that would power a low wattage AC inverter. The idea is to have a small, lightweight, portable battery pack with a solar panel on it that you can take with you to a job site or where ever you may need an AC power source. I am thinking about the size and weight of a 2000 watt Honda generator. I am in the solar business so I understand the limitations or solar. I know you are not going to run your RVs air conditioner off a 20 watt panel, but charging some cordless drill batteries or running a radio would be easy.

To throw some numbers out, let's say I want to power a 1000 watt inverter for an hour a day at full power, but realistically tyhat power usage would be at a lower rate spread out throughtout the day. I already have an inverter and a solar panel, I just need a battery and charging solution

Thanks

Peter

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Re: which battery chemistry is best for solar charging?

Post by chroot » May 24 2013 6:49pm

I would suggest best setup is going use deep cycle battery for the solar setup.

[solar panels] --> [ battery float charger] --> [ deep cycle batteries ] --> [ inverter ] --> [whatever you use power]
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Re: which battery chemistry is best for solar charging?

Post by spinningmagnets » May 24 2013 7:18pm

Use an RC charger to convert 12V into the 18V of your charger batteries. I have charged 18V drill batteries with alligator clips, because they were too low for the stock charger to recognize them as 18V, so it refused to charge them. (later I learned to parallel a full 18V battery pack with a low one, so the stock 18V charger would charge both of them together)

Common 120V-AC inverters will lose about 30% of your watts in the conversion from 12V-DC to 120V-AC (An expensive higher-end model might only lose 20%), so it is much more efficient to have as few conversions inline as possible. For back up power to charge flashlight-batteries/cell-phones/laptop-computers...I use a large solar-PV 12V panel (actually three of them) to charge a couple deep cycle 12V Flooded Lead Acid (FLA) batteries.

http://endless-sphere.com/forums/viewto ... 97#p717539

There was a recent poster who mentioned in passing that he sells 4S LiFePO4 batteries in motorcycle cases as starter batteries. I don't know the details or if LiFePO4 is a good idea or bad idea for solar charging...

Heynow999   10 mW

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Re: which battery chemistry is best for solar charging?

Post by Heynow999 » May 24 2013 7:32pm

I understand why you would suggest deep cycle LA or SLA but it would make the unit too heavy. Really what I want to do is take one of those portable booster packs and replace the SLA battery in it with a battery more energy dense, and add a solar panel that would help keep the pack charged. I have two booster packs with dead batteries that I am going to use for the inverter

I may be able to find a Morningstar charge controller that would deliver a controlled voltage, or I have seen lipo, solar charge controllers. I know solar but I am not very familiar with batteries and charging

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Re: which battery chemistry is best for solar charging?

Post by friendly1uk » May 24 2013 9:50pm

7.5Kg of lipo should do it.
bmsbattery sent me broken and incorrect stuff, and won't even talk to me about it.

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Re: which battery chemistry is best for solar charging?

Post by dogman dan » May 25 2013 5:50am

The best economy would likely be lifepo4 of some kind, because of the higher expected cycle lifespan. So the motorcycle starters or similar stuff would work.

You only need 12v to run an inverter for AC, but if charging another battery an RC charger for the win. So 12v 40 ah or so of lifepo4 would be a good choice.

If you didn't need all the wh every day, you could use a 40w panel. In my climate, you'd get 240 wh available daily. A two day charge. 240 wh would fill a lot of drill batteries. Add more panel if the use is heavier.

12v 40 ah would just be able to put out 1000w, but not for a long period. 80 ah for a continuous 1000w. That's with the cheaper 2c lifepo4 cells. 80 ah would be a 4 day charge with 40w panel in a 6 hr insolation area.

Or, if you only needed about 100wh per day, you could use better lifepo4. 12v 10 ah of headways for example, could put out 500w easy. They have a better c rate. And charge in less than a day with 40w panel. In one day, you could possibly draw 200 wh from the 120wh pack, tapping the solar as well as the stored charge.

EM3 ev could make you a dynamite 12v 20 ah A123 pack. That would be the best possible lifepo4. 240wh that could discharge 2000w. That would start a front loader on a cold day.

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jun 05 2013 11:05am

dogman wrote:The best economy would likely be lifepo4 of some kind, because of the higher expected cycle lifespan.... EM3 ev could make you a dynamite 12v 20 ah A123 pack. That would be the best possible lifepo4. 240wh that could discharge 2000w. That would start a front loader on a cold day.
Dogman, as usual, you seem to consistently be a wealth of know-how. I've got my A123 AMP20 12s battery, nominally 36volts (~39v to 42v actual). The idea of charging this battery with a solar panel is captivating, especially if I can make it mobile with my ebike. The idea is a second battery, so one in use and one charging. A perpetual motion machine of sorts so I'm not distance restricted.

I'm having trouble finding the correct solar charge controller, one suited to the specific make of my battery. Any suggestions? Many thanks. :mrgreen:

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Tommy L   100 kW

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Re: which battery chemistry is best for solar charging?

Post by Tommy L » Jun 05 2013 11:41am

I'm the guy with the 4s4p motorcycle start LiFePO4 batteries :)

If you use LiFePO4, then an appropriate solar charger is needed. One of the companies does
take the battery chemistry in mind and does make one.

My guess is that if you use LiFePO4 over Lead, you should be able to absorb 30% more energy into
the LiFePO4 vs Lead. I use the words "Should Be Able To" because the LiFePO4 cells have less internal
resistance. I haven't experimented yet.

Experiment - Observe - Take notes! :)


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arkmundi   1 GW

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jun 05 2013 12:02pm

At the Alt-E Store:

Solar Converters PT 36-5A, 36V MPPT Charge Controller at $119.00 per
All the listed Power Tracker™ charge controllers with MPPT can charge control a battery of lower voltage.... so long as the battery voltage is less than the panel voltage.
Nominal Voltage (V) 36
Nominal PV Array (V) 36
Max Array Voltage (V) 67.5
Float Setting **(V) 42
Overcharge Setting (V) 43
Temp. Comp. mv/Deg C -4
Efficiency 96%

-AND-
Three of these:
Sunwize SolCharger SC24-12V 24W 12V Solar Panel at $271.00 per
Model SC24
Rated Power (Watts) 24.0
Rated Voltage (Vmp, Volts) 18.7
Rated Current (Imp, Amps) 1.24
Open Circuit (Voc, Volts) 22.4
Short Circuit (Isc, Amps) 1.32
Dimensions (Inches) 13.3 x 21.18
Unit Weight (lbs) 3.70

3 of these panels is 21" by 40" and weights a mere 11 lbs
giving me the nominal 36V (54V rated), so works with the above charge controller
I figure about .06 kwh per ah to charge my battery: a full charge of 20ah is 0.120 kwh or 120 watt-hours, so about 5 hours of sunlight with this setup.

What do you think?

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Re: which battery chemistry is best for solar charging?

Post by Suspect » Jun 05 2013 12:16pm

I have 24 V Li batteries and made a "test" setup like this:
(custom module with 25X PV cells in series, 156 mm x 156 mm polycrystaline, output is ~13 V @ ~8 A) => (Boost converter to output ~30 V) => (arduino micro-controller switching a mosfet that limits voltage to 29.4 V)

This would work at other voltages. If you had the luxury of a PV panel w/ higher output voltage than the battery you could use the microcontroller to do all of the work.

Next I'd like to add power point tracking of the PV module using another PWM channel on the microcontroller. Does anyone know if this would work? I wonder if the microcontroller switching will mess with the boost converter and if so, how can I prevent it.

The boost controller I used is like this:
http://dx.com/p/120w-dc-dc-10-32v-to-35 ... red-156701
I do take an efficiency hit at the boost converter but building low voltage modules is easier, and I don't take a cell spacing efficiency hit.

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Re: which battery chemistry is best for solar charging?

Post by doovalacky » Jun 05 2013 6:08pm

I'm running LiFePO4. 16s system 40Ah with 500w solar and a morningstar ts-mppt-45. Nice seeing the amp meters pegged to max as soon as sun gets onto the panels. Am running with 800mA shunts that start to kick in at 3.6v max at 3.8v and due to one cell thats slow to charge they are just enough to keep other cells from going to high.

Nice and compact compared to lead. Did have to fiddle with the charge voltages to suit it to Li.

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Tommy L   100 kW

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Re: which battery chemistry is best for solar charging?

Post by Tommy L » Jun 07 2013 5:56am

doovalacky wrote:I'm running LiFePO4. 16s system 40Ah with 500w solar and a morningstar ts-mppt-45. Nice seeing the amp meters pegged to max as soon as sun gets onto the panels. Am running with 800mA shunts that start to kick in at 3.6v max at 3.8v and due to one cell thats slow to charge they are just enough to keep other cells from going to high.

Nice and compact compared to lead. Did have to fiddle with the charge voltages to suit it to Li.
Does your Morningstar have adjustable setting for the voltage?

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- 4th Hoolagan FS Mtn 9C-2810 with 128v nom 9.2ah A123 40S40P(1.2Kw) - Lyen 18Fet 4115 - 77.8kph :)
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- 3rd Catrike 700 Bionx PL350 Velo build
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Re: which battery chemistry is best for solar charging?

Post by doovalacky » Jun 07 2013 6:25pm

Yes, as I mentioned I had to reprogram it to suit with custom charge levels.
Floating them at 3.4v, with absorb set to 15min that only kicks in if been below float for 30m. Using equalise function to balance every 3 day at 3.68v.

Conservative perhaps but works for me battery voltage rarely goes below 3.2v. If it was not for one cell that drifts slowly I wouldn't be balancing as often as I am.

Did have to convert all settings into 48v equivalents for it.

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jun 20 2013 9:13am

So, Amy got back from vacation and is back at her desk with the Alt-E store, so had a chance to discuss my needs and their product offerings. As we all know, solar & solar charge tech is advancing at a very fast pace. So she altered me to the Genasun GV-Boost 105-350W Solar Boost Charge Controller with MPPT for Lithium Batteries. Not even in their system yet its so new. Amazing tech! Its a charge controller specifically for solar charging of lithium batteries, with voltage boost. So as long as your panels are 105-350 watts and as long as your battery is 12/24/36/48V, this controller is the little jewel that'll make it work! Enjoy. :mrgreen:

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arkmundi   1 GW

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jun 28 2013 3:54pm

arkmundi wrote:Genasun GV-Boost 105-350W Solar Boost Charge Controller with MPPT for Lithium Batteries
Amazing tech! Its a charge controller specifically for solar charging of lithium batteries, with voltage boost. So as long as your panels are 105-350 watts and as long as your battery is 12/24/36/48V, this controller is the little jewel that'll make it work!
Ok, so not a range of voltages, which would have been nice, but a custom single voltage which gets set a purchase. I asked for 41.8V, the full charge voltage for my nano-LiFePO4 AMP20 pack. See this thread for more.

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Re: which battery chemistry is best for solar charging?

Post by dnmun » Jun 28 2013 5:03pm

you should test out the repurposed lifepo4 packs that battboy guy just posted up.

has anyone developed a hack to build those solar trackers charge controllers? they cost more that it cost me to rebuild the engine on my car.

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jun 28 2013 6:02pm

dnmun wrote:you should test out the repurposed lifepo4 packs that battboy guy just posted up.

has anyone developed a hack to build those solar trackers charge controllers? they cost more that it cost me to rebuild the engine on my car.
haaahaaa... sure, someone should go for a hack. Let me know if anyone succeeds.

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Re: which battery chemistry is best for solar charging?

Post by dnmun » Jun 28 2013 6:51pm

i could not understand how they could charge $170 for the 12V version and $300 for the 48V version. i thought that was tacky to take advantage of people not knowing better.

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jun 28 2013 7:06pm

dnmun wrote:i could not understand how they could charge $170 for the 12V version and $300 for the 48V version. i thought that was tacky to take advantage of people not knowing better.
This is new tech, and there is nothing comparable that I could find. Its a solar charge controller custom made to my 36v (41.8v) LiFePO4 battery pack. I didn't buy retail from Genasun, but through the Alt-E store and they do volume purchasing, so I got a better price. I explored the world of solar charge controllers, found this to be best, made my purchase and am wholly satisfied. If yea no likeee then no buyee. Again, if someone knows of better product, or can hack the controller or has a better price for comparable product, please post it. Thanks.

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Re: which battery chemistry is best for solar charging?

Post by dnmun » Jun 29 2013 12:39am

it just can't cost that much more. maybe $10-12 for parts and real estate on the pcb.

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jun 29 2013 2:08am

The CEO of Genasun has a boat that he wanted equiped with solar. He found product lacking, so he went to MIT folks and they invented new charge controllers, capable of taking solar charge, doing MPPT, boosting it from 12V to 41.8V and charging LiFePO4 batteries. If you think you can do the same, go for it. If you know folks doing BMS charge control, then get them onto it. I did not find comparable product on the market. If you have, let me know. Thanks.

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Re: which battery chemistry is best for solar charging?

Post by doovalacky » Jun 30 2013 6:02am

I think you have been listening to much sales talk. Beyond the fact its a boost rather than buck regulator I don't see anything special about it from the specs.

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jun 30 2013 7:44pm

doovalacky wrote:I think you have been listening to much sales talk. Beyond the fact its a boost rather than buck regulator I don't see anything special about it from the specs.
Again, I'm buying, so of course I listen to sales people OR ANYONE ELSE that has comparable product. So again, if you know of actual product, as in the kind someone like me buys, and then can get product support and warranty on, then PLEASE let me know. Instead of ragging on me because I bought something I think will do the job make actual product recommendation. So far, no one has done that.

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Re: which battery chemistry is best for solar charging?

Post by doovalacky » Jul 01 2013 12:27am

Already posted above the details of the regulator (morningstar) that I am using. 800mA shunts came from evpower in Australia. Beyond the fact it's a boost regulator I don't see any difference to any other unit on the market that is programmable.

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Re: which battery chemistry is best for solar charging?

Post by arkmundi » Jul 01 2013 1:21am

doovalacky wrote:Beyond the fact it's a boost regulator I don't see any difference to any other unit on the market that is programmable.
That's a big deal for me, part of the spec. It has to boost from 12v to 36v, be solar MPPT, specific to a LiFEePO4 chemistry and generally do what a solar charge controller does. It also has to have a warranty. My Genasun has a 5 year warranty on it and its a company in the US, so no shipping to Hong Kong or what not. I have yet to find comparable product, or have it recommended.

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