Solar regulator with built in BMS for Lithium batteries

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Solar regulator with built in BMS for Lithium batteries

Postby gfsben » Wed Feb 22, 2017 6:15 pm

There is a current Kickstarter campaign for a Solar regulator with integrated BMS for Lithium batteries.
https://www.kickstarter.com/projects/electrodacus/digital-mppt-and-solar-bms-for-a-net-zero-energy-h/description
There is also an optional excess PV diverter that is designed to dump surplus PV into restive loads in thermal storage. This would be most relevant in locations where a large heating load is required. The concept is that an large array would preferentially charge a smaller than usually battery bank then divert surplus PV to heating. In this way a battery might be charged every day even when its overcast.
This 'DMPPT' does not seem quite so relevant to applications here in Australia. It would be good if it where able to drive heat pump compressors.

I am a little hesitant to start a thread about this device (the SBMS) as previous discussions about it here and elsewhere can become somewhat combative.
However it is a unique device and could end up being a very reliable and modifiable (its open source). It contains no electrolytic capacitors and has a rugged layered construction.

It's only available in 12 and 24v version which would limit large inverter choices.

It uses the Intersil ISL94203 bms chip for cell balancing which it does throughout the charge process.

I'm posting this because I know there are people here with significant experience with off grid LiFePO4 battery banks, and I would really like some of them to get one of these devices and properly evaluate it, rather than just be critical from the sidelines. The price of $400 or so for a 120 amp version seems pretty good considering its features.
I am planning on getting both the 40amp and 120amp versions.

I am really surprised at the lack of purpose built components on the market for utilising Lithium battery banks. Sure you can change parameters on existing charge regulators and use external cell balancers or other BMS. But this doesn't seem a very integrated or efficient approach and dosnt necessarily take advantage of Lithium battery characteristics, or current PV technology and prices.

The kickstarter campaign finishes in a week and is now fully funded. If you want to order an SBMS you need to do it soon, there is no indication they will be available for purchase outside KS at this point (as with previous campaigns).
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Re: Solar regulator with built in BMS for Lithium batteries

Postby davef » Wed Feb 22, 2017 8:08 pm

I bought-in on the last Kickstarter project, specifically the SBMS-060.

There were one installation issue that was quickly resolved.

The designer has provided the best product support that I have experienced in 40 years of hardware and software development.
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Re: Solar regulator with built in BMS for Lithium batteries

Postby Gordon-Loomberah » Wed Feb 22, 2017 8:20 pm

Electrodacus is a forum member, and was active here for a month or 2, a couple of years ago.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
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Re: Solar regulator with built in BMS for Lithium batteries

Postby gfsben » Thu Feb 23, 2017 11:34 am

Thanks Dave, that is good to know. What battery bank have you got it attached to? Do you use the external current sensor and a shunt so it can measure the current of attached inverters?
Apparently (hopefully) the new firmware will allow for bi-directional current measurement, so other types of charging inputs can be kept track of, for true SOC.

Hi Gordon. Yes I have read the thread you are thinking of. Electrodacus is a member of dozens of forums. He has in the past got fully involved in the discussion where ever on the web the SBMS has been mentioned (or he has brought it up). Strangely he has not been as active in bringing the discussion to forums recently. Perhaps he dosn't feel the need this time around.
I personally appreciate the effort. Most designers/manufactures do not get anywhere near as involved in the discussions about their products, leaving many valid suggestions for improvements or problems encountered, totally unanswered.
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Re: Solar regulator with built in BMS for Lithium batteries

Postby davef » Thu Feb 23, 2017 1:50 pm

gfbsen,

One of the main reasons I bought-in was the way he handled the flack on other forums. A profession engineer me-thinks.

8 * 200AH Winston. I am using the external shunt as I really should have bought the SBMS100 ... after the issue with large in-rush currents blowing up the discharge FET was "fixed". I was one of the unlucky ones, using it to feed a 3KW inverter, hence the VERY high in-rush current when switched on.

Unfortunately, other sources are not catered for. I only use a microhydro as a last-ditch backup so don't care how it contributes to SOC. Bi-directional current is a current feature.

Because of the usage profile I have battery capacity set to 220AH and I think it could even be at 240AH to get a better SOC readout.

Dave
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Re: Solar regulator with built in BMS for Lithium batteries

Postby gfsben » Thu Feb 23, 2017 5:31 pm

It's good to hear the board/FET can be easily repaired. I know this isn't everyone's cup of tea but I would rather something be repairable into the long term than just reliable for 5-10 years.
I did think it was a bit odd that in the diagrams of how one might connect a load, it showed an inverter running through the SBMS itself. This would really only be satisfactory for quite small inverters and even then it seems a bit unnecessarily risky, as you found out.
Interesting to hear that the current measurement via the shunt IS bidirectional. I must have missed that in the manual. When I asked about other external charging methods (ie an alternator or micro hydro) he said that he may include bidirectional current sensing and a digital signal to stop. This signal could open a contactor, shut a valve or stop a generator. Is there any obvious digital output signal that could stop a external charge source when the batteries reach a set voltage?

Cheers

Ben
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Re: Solar regulator with built in BMS for Lithium batteries

Postby davef » Thu Feb 23, 2017 8:20 pm

Ben,

He offered to repair the board. I have access to the required hotplate but the FETs were expensive here (shipping), so I haven't bothered.

By measuring battery, inverter and PV current one can work out what "direction" things are moving in.

I use several of the digital outputs. One is for LVD to control the inverter, he describes that in the manual. I didn't like the roughly one minute ON/OFF cycles so I use some of the digital outputs to control some external FET switches so that I can turn the PV off at 97% SOC. This gives me about 1 hour cycles. If you read the latest postings on that long thread on cruisersforum referred to in a recent posting on this forum, they seem keen on charging to 3.4 to 3.45V and discharge to 3.1V, then start charging again. I guess 3.1V is about 20-30% SOC. One would want the next day to be sunny!

Another digital output I use to control the microhydro. I was only turning it on if SOC or battery voltage dropped to some low level, ie 3.2V/cell or 40%.

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Re: Solar regulator with built in BMS for Lithium batteries

Postby beaujewel » Sat Feb 25, 2017 8:46 am

I have the sbms100, as was mentioned support has been fantastic. Emails to Dacian answered personally very quickly and concisely. I'll be using mine with a leaf battery bank and external shunt on a 2kw array.
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